Effects of Rainfall-Induced Topsoil Structure Changes on Root-Zone Moisture Regime during the Dry Period

NASA Astrophysics Data System (ADS)

Wang, Feng; Chen, Jiazhou; Lin, Lirong

2018-01-01

Rainfall erosion and subsequent intermittent drought are serious barriers for agricultural production in the subtropical red soil region of China. Although it is widely recognized that rainfall-induced soil structure degradation reduced soil water storage and water-holding capacity, the effects of variation of the rainfall-induced topsoil structure on the subsequent soil water regime during the dry period is still rarely considered. The objective of this study was to ascertain the way of rainfall-induced topsoil structure changes on the subsequent soil water regime during the dry period. In a three-year-long experiment, six practices (CK, only crop; SM, straw mulching; PAM, polyacrylamide surface application; B, contour Bahia-grass strip; SPAM, straw mulching and polyacrylamide surface application; and BPAM, contour Bahia-grass strip and polyacrylamide surface application) were conducted at an 8° farmland with planting summer maize resulting in different topsoil structure and root-zone moisture, to establish and reveal the quantitatively relationship between the factors of topsoil structure and soil drought. Rainfall erosion significantly increased the soil crust coverage, and decreased the WSA 0.25, 0-30 mm soil porosity and mean pore size. There was no significant difference during the raining stage of root-zone water storage between CK and other practices. An index of soil drought intensity ( I) and degree ( D) was established using soil water loss rate and soil drought severity. The larger value of I means a higher rate of water loss. The larger value of D means more severe drought. During the dry period, I and D were significantly higher in CK than in other practices. I and D had significantly positively correlation with the crust size and crust coverage, and negatively with WSA 0.25, 15-30 mm soil porosity and mean pore size. Among of soil structure factors, the soil porosity had the largest effect on I and D. The rainfall-induced topsoil structure changes greatly deteriorated the root-zone regime during the dry period mainly due to significant increasing soil water loss but little improving the raining stage of soil water storage. Straw mulching had greater effects than other practices in alleviating rainfall-induced erosion and intermittent drought, and could be a better strategy applied for this region.

Topsoil structure stability in a restored floodplain: Impacts of fluctuating water levels, soil parameters and ecosystem engineers.

PubMed

Schomburg, A; Schilling, O S; Guenat, C; Schirmer, M; Le Bayon, R C; Brunner, P

2018-10-15

Ecosystem services provided by floodplains are strongly controlled by the structural stability of soils. The development of a stable structure in floodplain soils is affected by a complex and poorly understood interplay of hydrological, physico-chemical and biological processes. This paper aims at analysing relations between fluctuating groundwater levels, soil physico-chemical and biological parameters on soil structure stability in a restored floodplain. Water level fluctuations in the soil are modelled using a numerical surface-water-groundwater flow model and correlated to soil physico-chemical parameters and abundances of plants and earthworms. Causal relations and multiple interactions between the investigated parameters are tested through structural equation modelling (SEM). Fluctuating water levels in the soil did not directly affect the topsoil structure stability, but indirectly through affecting plant roots and soil parameters that in turn determine topsoil structure stability. These relations remain significant for mean annual days of complete and partial (>25%) water saturation. Ecosystem functioning of a restored floodplain might already be affected by the fluctuation of groundwater levels alone, and not only through complete flooding by surface water during a flood period. Surprisingly, abundances of earthworms did not show any relation to other variables in the SEM. These findings emphasise that earthworms have efficiently adapted to periodic stress and harsh environmental conditions. Variability of the topsoil structure stability is thus stronger driven by the influence of fluctuating water levels on plants than by the abundance of earthworms. This knowledge about the functional network of soil engineering organisms, soil parameters and fluctuating water levels and how they affect soil structural stability is of fundamental importance to define management strategies of near-natural or restored floodplains in the future. Copyright © 2018 Elsevier B.V. All rights reserved.

Soil Texture Often Exerts a Stronger Influence Than Precipitation on Mesoscale Soil Moisture Patterns

NASA Astrophysics Data System (ADS)

Dong, Jingnuo; Ochsner, Tyson E.

2018-03-01

Soil moisture patterns are commonly thought to be dominated by land surface characteristics, such as soil texture, at small scales and by atmospheric processes, such as precipitation, at larger scales. However, a growing body of evidence challenges this conceptual model. We investigated the structural similarity and spatial correlations between mesoscale (˜1-100 km) soil moisture patterns and land surface and atmospheric factors along a 150 km transect using 4 km multisensor precipitation data and a cosmic-ray neutron rover, with a 400 m diameter footprint. The rover was used to measure soil moisture along the transect 18 times over 13 months. Spatial structures of soil moisture, soil texture (sand content), and antecedent precipitation index (API) were characterized using autocorrelation functions and fitted with exponential models. Relative importance of land surface characteristics and atmospheric processes were compared using correlation coefficients (r) between soil moisture and sand content or API. The correlation lengths of soil moisture, sand content, and API ranged from 12-32 km, 13-20 km, and 14-45 km, respectively. Soil moisture was more strongly correlated with sand content (r = -0.536 to -0.704) than with API for all but one date. Thus, land surface characteristics exhibit coherent spatial patterns at scales up to 20 km, and those patterns often exert a stronger influence than do precipitation patterns on mesoscale spatial patterns of soil moisture.

Colonization and community structure of root-associated microorganisms of Sabina vulgaris with soil depth in a semiarid desert ecosystem with shallow groundwater.

PubMed

Taniguchi, Takeshi; Usuki, Hiroyuki; Kikuchi, Junichi; Hirobe, Muneto; Miki, Naoko; Fukuda, Kenji; Zhang, Guosheng; Wang, Linhe; Yoshikawa, Ken; Yamanaka, Norikazu

2012-08-01

Arbuscular mycorrhizal fungi (AMF) have been observed in deep soil layers in arid lands. However, change in AMF community structure with soil depth and vertical distributions of the other root-associated microorganisms are unclear. Here, we examined colonization by AMF and dark septate fungi (DSF), as well as the community structure of AMF and endophytic fungi (EF) and endophytic bacteria (EB) in association with soil depth in a semiarid desert with shallow groundwater. Roots of Sabina vulgaris and soils were collected from surface to groundwater level at 20-cm intervals. Soil chemistry (water content, total N, and available P) and colonization of AMF and DSF were measured. Community structures of AMF, EF, and EB were examined by terminal restriction fragment length polymorphism analysis. AMF colonization decreased with soil depth, although it was mostly higher than 50%. Number of AMF phylotypes decreased with soil depth, but more than five phylotypes were observed at depths up to 100 cm. Number of AMF phylotypes had a significant and positive relationship with soil moisture level within 0-15% of soil water content. DSF colonization was high but limited to soil surface. Number of phylotypes of EF and EB were diverse even in deep soil layers, and the community composition was associated with the colonization and community composition of AMF. This study indicates that AMF species richness in roots decreases but is maintained in deep soil layers in semiarid regions, and change in AMF colonization and community structure associates with community structure of the other root-associated microorganisms.

Mechanisms of surface runoff genesis on a subsurface drained soil affected by surface crusting: A field investigation

NASA Astrophysics Data System (ADS)

Augeard, Bénédicte; Kao, Cyril; Chaumont, Cédric; Vauclin, Michel

Artificial drainage has been subject to widespread criticism because of its impact on water quality and because there is suspicion that it may have detrimental effects on flood genesis. The present work aims at a better understanding of the mechanisms controlling infiltration and surface runoff genesis, particularly in soils with artificial drainage and affected by surface crusting. A field experiment was conducted during one drainage season (November 2003-March 2004) in the Brie region (80 km east of Paris, France) on a subsurface drained silty soil. Water table elevation and surface runoff were monitored above the drain and at midpoint between drains. Soil water pressure head was measured at various depths and locations between the midpoint and the drain. Soil surface characteristics (microtopography and degree of structural and sedimentary crust development) were recorded regularly on the experimental site and on other plots of various drainage intensities. The results show that the first surface runoff events were induced by high water table. However, runoff was higher at midpoint between the drains because water table reached the soil surface at that point, thus considerably reducing infiltration capacity compared to that above the drain. Comparing different plots, the area with older drainage installation (1948) yielded the most surface runoff. Wider drain spacing, smaller drain depth and possible plugging may have led to a greater area of saturated soil between drains. During the winter period, the impact of raindrops induced the formation of a structural crust on the soil surface. Furthermore, the development of the sedimentary crust, which was favored by water actually flowing on the soil surface during the high water table periods could be correlated with surface runoff volume. The formation of this crust had a significant impact on runoff occurrence at the end of the winter. Therefore, poorly drained fields presented more favorable conditions for both Horton type runoff and saturation excess runoff. Drainage effectively reduces surface runoff occurrences not only by lowering the water table in winter but also by limiting soil surface sealing.

Response surface method in geotechnical/structural analysis, phase 1

NASA Astrophysics Data System (ADS)

Wong, F. S.

1981-02-01

In the response surface approach, an approximating function is fit to a long running computer code based on a limited number of code calculations. The approximating function, called the response surface, is then used to replace the code in subsequent repetitive computations required in a statistical analysis. The procedure of the response surface development and feasibility of the method are shown using a sample problem in slop stability which is based on data from centrifuge experiments of model soil slopes and involves five random soil parameters. It is shown that a response surface can be constructed based on as few as four code calculations and that the response surface is computationally extremely efficient compared to the code calculation. Potential applications of this research include probabilistic analysis of dynamic, complex, nonlinear soil/structure systems such as slope stability, liquefaction, and nuclear reactor safety.

HYDRAULIC REDISTRIBUTION OF SOIL WATER BY ROOTS IN FORESTS OF THE PACIFIC NORTHWEST

EPA Science Inventory

One aspect of structural complexity of forest canopies is the root system structure belowground, which influences patterns of soil water utilization by trees. Deeply rooted trees and other plants can hydraulically lift water via their roots from several m below the soil surface ...

Enhancing soil begins with soil biology and a stable soil microclimate

USDA-ARS?s Scientific Manuscript database

Protection of the soil resource from erosion requires reducing the surface impact from raindrop energy and maintaining soil structure and stability to allow more efficient infiltration of water into the soil column. These two processes are linked with practices associated with enhancing and maintain...

Using SMAP to identify structural errors in hydrologic models

NASA Astrophysics Data System (ADS)

Crow, W. T.; Reichle, R. H.; Chen, F.; Xia, Y.; Liu, Q.

2017-12-01

Despite decades of effort, and the development of progressively more complex models, there continues to be underlying uncertainty regarding the representation of basic water and energy balance processes in land surface models. Soil moisture occupies a central conceptual position between atmosphere forcing of the land surface and resulting surface water fluxes. As such, direct observations of soil moisture are potentially of great value for identifying and correcting fundamental structural problems affecting these models. However, to date, this potential has not yet been realized using satellite-based retrieval products. Using soil moisture data sets produced by the NASA Soil Moisture Active/Passive mission, this presentation will explore the use of the remotely-sensed soil moisture data products as a constraint to reject certain types of surface runoff parameterizations within a land surface model. Results will demonstrate that the precision of the SMAP Level 4 Surface and Root-Zone soil moisture product allows for the robust sampling of correlation statistics describing the true strength of the relationship between pre-storm soil moisture and subsequent storm-scale runoff efficiency (i.e., total storm flow divided by total rainfall both in units of depth). For a set of 16 basins located in the South-Central United States, we will use these sampled correlations to demonstrate that so-called "infiltration-excess" runoff parameterizations under predict the importance of pre-storm soil moisture for determining storm-scale runoff efficiency. To conclude, we will discuss prospects for leveraging this insight to improve short-term hydrologic forecasting and additional avenues for SMAP soil moisture products to provide process-level insight for hydrologic modelers.

Sensitivity of Rayleigh wave ellipticity and implications for surface wave inversion

NASA Astrophysics Data System (ADS)

Cercato, Michele

2018-04-01

The use of Rayleigh wave ellipticity has gained increasing popularity in recent years for investigating earth structures, especially for near-surface soil characterization. In spite of its widespread application, the sensitivity of the ellipticity function to the soil structure has been rarely explored in a comprehensive and systematic manner. To this end, a new analytical method is presented for computing the sensitivity of Rayleigh wave ellipticity with respect to the structural parameters of a layered elastic half-space. This method takes advantage of the minor decomposition of the surface wave eigenproblem and is numerically stable at high frequency. This numerical procedure allowed to retrieve the sensitivity for typical near surface and crustal geological scenarios, pointing out the key parameters for ellipticity interpretation under different circumstances. On this basis, a thorough analysis is performed to assess how ellipticity data can efficiently complement surface wave dispersion information in a joint inversion algorithm. The results of synthetic and real-world examples are illustrated to analyse quantitatively the diagnostic potential of the ellipticity data with respect to the soil structure, focusing on the possible sources of misinterpretation in data inversion.

Arbuscule mycorrhizae: A linkage between erosion and plant processes in a southwest grassland

Treesearch

Mary O' Dea; D. Phillip Guertin; C. P. P. Reid

2000-01-01

Plant and soil processes within a natural ecosystem interact with surface hydrology through their influence on surface roughness, soil structure, and evaporation, and through their relation with soil biota. In the Southwest, decreases in perennial grass cover and erosion on uplands and stream channels can initiate a decline in watershed condition. Agronomic literature...

The activity and community structure of total bacteria and denitrifying bacteria across soil depths and biological gradients in estuary ecosystem.

PubMed

Lee, Seung-Hoon; Kang, Hojeong

2016-02-01

The distribution of soil microorganisms often shows variations along soil depth, and even in the same soil layer, each microbial group has a specific niche. In particular, the estuary soil is intermittently flooded, and the characteristics of the surface soil layer are different from those of other terrestrial soils. We investigated the microbial community structure and activity across soil depths and biological gradients composed of invasive and native plants in the shallow surface layer of an estuary ecosystem by using molecular approaches. Our results showed that the total and denitrifying bacterial community structures of the estuarine wetland soil differed according to the short depth gradient. In growing season, gene copy number of 16S rRNA were 1.52(±0.23) × 10(11), 1.10(±0.06) × 10(11), and 4.33(±0.16) × 10(10) g(-1) soil; nirS were 5.41(±1.25) × 10(8), 4.93(±0.94) × 10(8), and 2.61(±0.28) × 10(8) g(-1) soil; and nirK were 9.67(±2.37) × 10(6), 3.42(±0.55) × 10(6), and 2.12(±0.19) × 10(6) g(-1) soil in 0 cm, 5 cm, and 10 cm depth layer, respectively. The depth-based difference was distinct in the vegetated sample and in the growing season, evidencing the important role of plants in structuring the microbial community. In comparison with other studies, we observed differences in the microbial community and functions even across very short depth gradients. In conclusion, our results suggested that (i) in the estuary ecosystem, the denitrifying bacterial community could maintain its abundance and function within shallow surface soil layers through facultative anaerobiosis, while the total bacterial community would be both quantitatively and qualitatively affected by the soil depth, (ii) the nirS gene community, rather than the nirK one, should be the first candidate used as an indicator of the microbial denitrification process in the estuary system, and (iii) as the microbial community is distributed and plays a certain niche role according to biogeochemical factors, the study of the microbial community even in surface soil should be performed in detail by considering the soil depth.

Fire effects on soil organic matter content, composition, and nutrients in boreal interior Alaska

USGS Publications Warehouse

Neff, J.C.; Harden, J.W.; Gleixner, G.

2005-01-01

Boreal ecosystems contain a substantial fraction of the earth's soil carbon stores and are prone to frequent and severe wildfires. In this study, we examine changes in element and organic matter stocks due to a 1999 wildfire in Alaska. One year after the wildfire, burned soils contained between 1071 and 1420 g/m2 less carbon than unburned soils. Burned soils had lower nitrogen than unburned soils, higher calcium, and nearly unchanged potassium, magnesium, and phosphorus stocks. Burned surface soils tended to have higher concentrations of noncombustible elements such as calcium, potassium, magnesium, and phosphorus compared with unburned soils. Combustion losses of carbon were mostly limited to surface dead moss and fibric horizons, with no change in the underlying mineral horizons. Burning caused significant changes in soil organic matter structure, with a 12% higher ratio of carbon to combustible organic matter in surface burned horizons compared with unburned horizons. Pyrolysis gas chromatography - mass spectroscopy also shows preferential volatilization of polysaccharide-derived organic matter and enrichment of lignin-and lipid-derived compounds in surface soils. The chemistry of deeper soil layers in burned and unburned sites was similar, suggesting that immediate fire impacts were restricted to the surface soil horizon. ?? 2005 NRC.

Mapping of Soil-Ecological Conditions of a Medium-Size Industrial City (Birobidzhan City, Jewish Autonomous Oblast, FarEast of Russia as an Example)

NASA Astrophysics Data System (ADS)

Kalmanova, V. B.; Matiushkina, L. A.

2018-01-01

The authors analyze soil relations with other elements of the city ecosystem (the position in the landscape, soil-forming rocks and lithology, vegetation and its state) to develop the legend and map of soils in the City of Birobidzhan (scale 1:25 000). The focus of study is the morphological structure of urban soils with different degree of disturbance of these relations under the impact of technical effects, economic and recreational activities of the city population. The soil cover structure is composed of four large ecological groups of soils: natural untransformed, natural with a disturbed surface, anthropogenic soils and technogenic surface formations. Using cartometry of the mapped soil contours the authors created the scheme of soil-ecological city zoning, which in a general way depicts the state of soil ecological functions in the city as well as identified zones of soils with preserved, partially and fully distured ecological functions and zones of local geochemical anomalies at the initial formation stage (environmental risk zones).

Using lagged dependence to identify (de)coupled surface and subsurface soil moisture values

NASA Astrophysics Data System (ADS)

Carranza, Coleen D. U.; van der Ploeg, Martine J.; Torfs, Paul J. J. F.

2018-04-01

Recent advances in radar remote sensing popularized the mapping of surface soil moisture at different spatial scales. Surface soil moisture measurements are used in combination with hydrological models to determine subsurface soil moisture values. However, variability of soil moisture across the soil column is important for estimating depth-integrated values, as decoupling between surface and subsurface can occur. In this study, we employ new methods to investigate the occurrence of (de)coupling between surface and subsurface soil moisture. Using time series datasets, lagged dependence was incorporated in assessing (de)coupling with the idea that surface soil moisture conditions will be reflected at the subsurface after a certain delay. The main approach involves the application of a distributed-lag nonlinear model (DLNM) to simultaneously represent both the functional relation and the lag structure in the time series. The results of an exploratory analysis using residuals from a fitted loess function serve as a posteriori information to determine (de)coupled values. Both methods allow for a range of (de)coupled soil moisture values to be quantified. Results provide new insights into the decoupled range as its occurrence among the sites investigated is not limited to dry conditions.

DYNAMICS OF MINERAL STRUCTURES AND THE FATE OF METALS IN SOILS AND SEDIMENTS

EPA Science Inventory

Significant progress has been made in elucidating sorption reactions that control the partitioning of metals from solution to mineral surfaces in contaminated soil/sediment systems. Surface complexation models have been developed to quantify the forward reaction with reasonable ...

Soil seal development under simulated rainfall: Structural, physical and hydrological dynamics

NASA Astrophysics Data System (ADS)

Armenise, Elena; Simmons, Robert W.; Ahn, Sujung; Garbout, Amin; Doerr, Stefan H.; Mooney, Sacha J.; Sturrock, Craig J.; Ritz, Karl

2018-01-01

This study delivers new insights into rainfall-induced seal formation through a novel approach in the use of X-ray Computed Tomography (CT). Up to now seal and crust thickness have been directly quantified mainly through visual examination of sealed/crusted surfaces, and there has been no quantitative method to estimate this important property. X-ray CT images were quantitatively analysed to derive formal measures of seal and crust thickness. A factorial experiment was established in the laboratory using open-topped microcosms packed with soil. The factors investigated were soil type (three soils: silty clay loam - ZCL, sandy silt loam - SZL, sandy loam - SL) and rainfall duration (2-14 min). Surface seal formation was induced by applying artificial rainfall events, characterised by variable duration, but constant kinetic energy, intensity, and raindrop size distribution. Soil porosities derived from CT scans were used to quantify the thickness of the rainfall-induced surface seals and reveal temporal seal micro-morphological variations with increasing rainfall duration. In addition, the water repellency and infiltration dynamics of the developing seals were investigated by measuring water drop penetration time (WDPT) and unsaturated hydraulic conductivity (Kun). The range of seal thicknesses detected varied from 0.6 to 5.4 mm. Soil textural characteristics and OM content played a central role in the development of rainfall-induced seals, with coarser soil particles and lower OM content resulting in thicker seals. Two different trends in soil porosity vs. depth were identified: i) for SL soil porosity was lowest at the immediate soil surface, it then increased constantly with depth till the median porosity of undisturbed soil was equalled; ii) for ZCL and SL the highest reduction in porosity, as compared to the median porosity of undisturbed soil, was observed in a well-defined zone of maximum porosity reduction c. 0.24-0.48 mm below the soil surface. This contrasting behaviour was related to different dynamics and processes of seal formation which depended on the soil properties. The impact of rainfall-induced surface sealing on the hydrological behaviour of soil (as represented by WDTP and Kun) was rapid and substantial: an average 60% reduction in Kun occurred for all soils between 2 and 9 min rainfall, and water repellent surfaces were identified for SZL and ZCL. This highlights that the condition of the immediate surface of agricultural soils involving rainfall-induced structural seals has a strong impact in the overall ability of soil to function as water reservoir.

Urbanization Effects on the Vertical Distribution of Soil Microbial Communities and Soil C Storage across Edge-to-Interior Urban Forest Gradients

NASA Astrophysics Data System (ADS)

Rosier, C. L.; Van Stan, J. T., II; Trammell, T. L.

2017-12-01

Urbanization alters environmental conditions such as temperature, moisture, carbon (C) and nitrogen (N) deposition affecting critical soil processes (e.g., C storage). Urban soils experience elevated N deposition (e.g., transportation, industry) and decreased soil moisture via urban heat island that can subsequently alter soil microbial community structure and activity. However, there is a critical gap in understanding how increased temperatures and pollutant deposition influences soil microbial community structure and soil C/N cycling in urban forests. Furthermore, canopy structural differences between individual tree species is a potentially important mechanism facilitating the deposition of pollutants to the soil. The overarching goal of this study is to investigate the influence of urbanization and tree species structural differences on the bacterial and fungal community and C and N content of soils experiencing a gradient of urbanization pressures (i.e., forest edge to interior; 150-m). Soil cores (1-m depth) were collected near the stem (< 0.5 meter) of two tree species with contrasting canopy and bark structure (Fagus grandifolia, vs. Liriodendron tulipifera), and evaluated for soil microbial structure via metagenomic analysis and soil C/N content. We hypothesize that soil moisture constraints coupled with increases in recalcitrant C will decrease gram negative bacteria (i.e., dependent on labile C) while increasing saprophytic fungal community abundance (i.e., specialist consuming recalcitrant C) within both surface and subsurface soils experiencing the greatest urban pressure (i.e., forest edge). We further expect trees located on the edge of forest fragments will maintain greater surface soil (< 20 cm) C concentrations due to decreased soil moisture constraining microbial activity (e.g., slower decay), and increased capture of recalcitrant C stocks from industrial/vehicle emission sources (e.g., black C). Our initial results support our hypotheses that urbanization alters soil microbial community composition via reduced soil moisture and carbon storage potential via deposition gradients. Further analyses will answer important questions regarding how individual tree species alters urban soil C storage, N retention, and microbial dynamics.

Installing artificial macropores in degraded soils to enhance vertical infiltration and increase soil carbon content

NASA Astrophysics Data System (ADS)

Mori, Yasushi; Fujihara, Atsushi; Yamagishi, Kazuto

2014-12-01

Of all terrestrial media (including vegetation and the atmosphere), soil is the largest store of carbon. Soils also have important functions such as water storage and plant support roles. However, at present, these characteristics do not fully function, because of, for example, climate-change-induced heavy rainfall would wash away the organic-rich surface soils. In this study, artificial macropores were introduced into exposed soil plots for the purpose of enhancing infiltration, and fibrous material was inserted to reinforce the macropore structure. As expected, the capillary force caused by the fibers drew surface water deeper into the soil profile before saturation. Additionally, the same capillary force promoted vertical transport, while micropores (matrix) enhanced horizontal flow. Our results show that infiltration was more effective in the fiber-containing macropores than in empty macropores. Additionally, our column experiments showed that artificial macropores reduced surface runoff when the rainfall intensities were 2, 4, and 20 mm · h-1 but not for 80 mm · h-1. In field experiments, soil moisture sensors installed at depths of 10, 30, and 50 cm responded well to rainfall, showing that artificial macropores were able to successfully introduce surface water into the soil profile. One year after the artificial macropores were installed, a field survey carried out to assess soil organic matter and plant growth showed that plant biomass had doubled and that there was a significant increase in soil carbon. This novel technique has many advantages as it mimics natural processes, is low cost, and has a simple structure.

pH dependence and unsuitability of fluorescein dye as a tracer for pesticide mobility studies in acid soil

Treesearch

Chris Peterson

2009-01-01

The mobility of fluorescein and bromide used as tracers in packed soil columns was investigated.Five different soils were used in two application methods: soil surface application and soil incorporation, both of which simulate accepted methods of soil application of termiticides to prevent structural infestation. The...

Cleanup Verification Package for the 118-H-6:2, 105-H Reactor Ancillary Support Areas, Below-Grade Structures, and Underlying Soils; the 118-H-6:3, 105-H Reactor Fuel Storage Basin and Underlying Soils; The 118-H-6:3 Fuel Storage Basin Deep Zone Side Slope Soils; the 100-H-9, 100-H-10, and 100-H-13 French Drains; the 100-H-11 and 100-H-12 Expansion Box French Drains; and the 100-H-14 and 100-H-31 Surface Contamination Zones

DOE Office of Scientific and Technical Information (OSTI.GOV)

M. J. Appel

2006-06-29

This cleanup verification package documents completion of removal actions for the 105-H Reactor Ancillary Support Areas, Below-Grade Structures, and Underlying Soils (subsite 118-H-6:2); 105-H Reactor Fuel Storage Basin and Underlying Soils (118-H-6:3); and Fuel Storage Basin Deep Zone Side Slope Soils. This CVP also documents remedial actions for the following seven additional waste sties: French Drain C (100-H-9), French Drain D (100-H-10), Expansion Box French Drain E (100-H-11), Expansion Box French Drain F (100-H-12), French Drain G (100-H-13), Surface Contamination Zone H (100-H-14), and the Polychlorinated Biphenyl Surface Contamination Zone (100-H-31).

Microbial mediated soil structure formation under wetting and drying cycles along a climate gradient (arid to humid) on hillslopes in Chile

NASA Astrophysics Data System (ADS)

Bernhard, Nadine; Moskwa, Lisa-Marie; Kühn, Peter; Mueller, Carsten W.; Wagner, Dirk; Scholten, Thomas

2017-04-01

It is well-known that the land surface resistance against erosion is largely controlled by the structure stability of the soil given by its inherent properties. Microbial activity plays a vital role in soil structure development, and thus affecting soil physical parameters. Accordingly the influence of biota shaping the earth's surface has been described through mechanisms such as mineral weathering, formation of ions and biofilms controlling land surface resistance against erosion. However the role of microorganisms for the development of soil stabilizing properties is still unclear and a precise quantitative understanding of the mechanisms under different climate conditions is widely missing. The objectives of our study are to examine to which extend microbiological processes control soil structure formation and stability and whether this is influenced by climate and topographic position. Soil samples were taken along a climate gradient and from different topographic positions of hillslopes in the Chilean Coastal Cordillera in austral autumn 2016. The variables of lithology, human disturbances and relief were held as far as possible constant whereas climate varies along the transect. We implemented 10 wet-dry cycles on air dried and sieved natural and sterile samples to enhance particle aggregation and increase structure stability. Throughout the entire experiment temperature is held constant at 20 °C to avoid changes in microbial activity. Samples are moistened and dried and each kept at the same respective pF-values for the same duration to add the same stress to each sample. Aggregate stability will be measured using wet sieving, ultrasonic dispersion and simulated rainfall. The results will be compared with on-site rainfall simulation experiments on hillslopes in the Chilean Coastal Cordillera to link laboratory results with natural field conditions. The experiment gives first insight into the aggregate formation process over time with and without microorganisms (sterilized samples). Furthermore it allows to qualify and quantify the contribution of biota to soil structure formation and stability.

Spatial structure and scaling of macropores in hydrological process at small catchment scale

NASA Astrophysics Data System (ADS)

Silasari, Rasmiaditya; Broer, Martine; Blöschl, Günter

2013-04-01

During rainfall events, the formation of overland flow can occur under the circumstances of saturation excess and/or infiltration excess. These conditions are affected by the soil moisture state which represents the soil water content in micropores and macropores. Macropores act as pathway for the preferential flows and have been widely studied locally. However, very little is known about their spatial structure and conductivity of macropores and other flow characteristic at the catchment scale. This study will analyze these characteristics to better understand its importance in hydrological processes. The research will be conducted in Petzenkirchen Hydrological Open Air Laboratory (HOAL), a 64 ha catchment located 100 km west of Vienna. The land use is divided between arable land (87%), pasture (5%), forest (6%) and paved surfaces (2%). Video cameras will be installed on an agricultural field to monitor the overland flow pattern during rainfall events. A wireless soil moisture network is also installed within the monitored area. These field data will be combined to analyze the soil moisture state and the responding surface runoff occurrence. The variability of the macropores spatial structure of the observed area (field scale) then will be assessed based on the topography and soil data. Soil characteristics will be supported with laboratory experiments on soil matrix flow to obtain proper definitions of the spatial structure of macropores and its variability. A coupled physically based distributed model of surface and subsurface flow will be used to simulate the variability of macropores spatial structure and its effect on the flow behaviour. This model will be validated by simulating the observed rainfall events. Upscaling from field scale to catchment scale will be done to understand the effect of macropores variability on larger scales by applying spatial stochastic methods. The first phase in this study is the installation and monitoring configuration of video cameras and soil moisture monitoring equipment to obtain the initial data of overland flow occurrence and soil moisture state relationships.

Improving Water Level and Soil Moisture Over Peatlands in a Global Land Modeling System

NASA Technical Reports Server (NTRS)

Bechtold, M.; De Lannoy, G. J. M.; Roose, D.; Reichle, R. H.; Koster, R. D.; Mahanama, S. P.

2017-01-01

New model structure for peatlands results in improved skill metrics (without any parameter calibration) Simulated surface soil moisture strongly affected by new model, but reliable soil moisture data lacking for validation.

Community structures and activity of denitrifying microbes in a forested catchment in central Japan: survey using nitrite reductase genes

NASA Astrophysics Data System (ADS)

Ohte, N.; Aoki, M.; Katsuyama, C.; Suwa, Y.; Tange, T.

2012-12-01

To elucidate the mechanisms of denitrification processes in the forested catchment, microbial ecological approaches have been applied in an experimental watershed that has previously investigated its hydrological processes. The study catchment is located in the Chiba prefecture in central Japan under the temperate Asian monsoon climate. Potential activities of denitrification of soil samples were measured by incubation experiments under anoxic condition associated with Na15NO3 addition. Existence and variety of microbes having nitrite reductase genes were investigated by PCR amplification, cloning and sequencings of nirK and nirS fragments after DNA extraction. Contrary to our early expectation that the potential denitrification activity was higher at deeper soil horizon with consistent groundwater residence than that in the surface soil, denitrification potential was higher in shallower soil horizons than deeper soils. This suggested that the deficiency of NO3- as a respiratory substrate for denitrifier occurred in deeper soils especially in the summer. However, high denitrification activity and presence of microbes having nirK and nirS in surface soils usually under aerobic condition was explainable by the fact that the majority of denitrifying bacteria have been recognized as a facultative anaerobic bacterium. This also suggests the possibility of that denitrification occurs even in the surface soils if the wet condition is provided by rainwater during and after a storm event. Community structures of microbes having nirK were different between near surface and deeper soil horizons, and ones having nirS was different between saturated zone (under groundwater table) and unsaturated soil horizons. These imply that microbial communities with nisK are sensitive to the concentration of soil organic matters and ones with nirS is sensitive to soil moisture contents.

Modeling interface shear behavior of granular materials using micro-polar continuum approach

NASA Astrophysics Data System (ADS)

Ebrahimian, Babak; Noorzad, Ali; Alsaleh, Mustafa I.

2018-01-01

Recently, the authors have focused on the shear behavior of interface between granular soil body and very rough surface of moving bounding structure. For this purpose, they have used finite element method and a micro-polar elasto-plastic continuum model. They have shown that the boundary conditions assumed along the interface have strong influences on the soil behavior. While in the previous studies, only very rough bounding interfaces have been taken into account, the present investigation focuses on the rough, medium rough and relatively smooth interfaces. In this regard, plane monotonic shearing of an infinite extended narrow granular soil layer is simulated under constant vertical pressure and free dilatancy. The soil layer is located between two parallel rigid boundaries of different surface roughness values. Particular attention is paid to the effect of surface roughness of top and bottom boundaries on the shear behavior of granular soil layer. It is shown that the interaction between roughness of bounding structure surface and the rotation resistance of bounding grains can be modeled in a reasonable manner through considered Cosserat boundary conditions. The influence of surface roughness is investigated on the soil shear strength mobilized along the interface as well as on the location and evolution of shear localization formed within the layer. The obtained numerical results have been qualitatively compared with experimental observations as well as DEM simulations, and acceptable agreement is shown.

Assessing the fate of radioactive nickel in cultivated soil cores.

PubMed

Denys, Sébastien; Echevarria, Guillaume; Florentin, Louis; Leclerc, Elisabeth; Morel, Jean-Louis

2009-10-01

Parameters regarding fate of (63)Ni in the soil-plant system (soil: solution distribution coefficient, K(d) and soil plant concentration ratio, CR) are mostly determined in controlled pot experiments or from simple models involving a limited set of soil parameters. However, as migration of pollutants in soil is strongly linked to the water migration, variation of soil structure in the field and seasonal variation of evapotranspiration will affect these two parameters. The aim of this work was to explore to what extent the downward transfer of (63)Ni and its uptake by plants from surface-contaminated undisturbed soil cores under cultivation can be explained by isotopic dilution of this radionuclide in the pool of stable Ni of soils. Undisturbed soil cores (50 cm x 50 cm) were sampled from a brown rendzina (Rendzic Leptosol), a colluvial brown soil (Fluvic Cambisol) and an acidic brown soil (Dystric Cambisol) using PVC lysimeter tubes (three lysimeters sampled per soil type). Each core was equipped with a leachate collector. Cores were placed in a greenhouse and maize (DEA, Pioneer) was sown. After 44 days, an irrigation was simulated at the core surfaces to supply 10 000 Bq (63)NiCl(2). Maize was harvested 135 days after (63)Ni input and radioactivity determined in both vegetal and water samples. Effective uptake of (63)Ni by maize was calculated for leaves and kernels. Water drainage and leaching of (63)Ni were monitored over the course of the experiment. Values of K(d) in surface soil samples were calculated from measured parameters of isotopic exchange kinetics. Results confirmed that (63)Ni was strongly retained at the soil surface. Prediction of the (63)Ni downward transfer could not be reliably assessed using the K(d) values, since the soil structure, which controls local water fluxes, also affected both water and Ni transport. In terms of (63)Ni plant uptake, the effective uptake in undisturbed soil cores is controlled by isotope dilution as previously shown at the pot experiment scale.

Method and apparatus for optimized sampling of volatilizable target substances

DOEpatents

Lindgren, Eric R.; Phelan, James M.

2004-10-12

An apparatus for capturing, from gases such as soil gas, target analytes. Target analytes may include emanations from explosive materials or from residues of explosive materials. The apparatus employs principles of sorption common to solid phase microextraction, and is best used in conjunction with analysis means such as a gas chromatograph. To sorb target analytes, the apparatus functions using various sorptive structures to capture target analyte. Depending upon the embodiment, those structures may include a capillary tube including an interior surface on which sorptive material (similar to that on the surface of a SPME fiber) is supported (along with means for moving gases through the capillary tube so that the gases come into close proximity to the sorptive material). In one disclosed embodiment, at least one such sorptive structure is associated with an enclosure including an opening in communication with the surface of a soil region potentially contaminated with buried explosive material such as unexploded ordnance. Emanations from explosive materials can pass into and accumulate in the enclosure where they are sorbed by the sorptive structures. Also disclosed is the use of heating means such as microwave horns to drive target analytes into the soil gas from solid and liquid phase components of the soil.

Surface soil root response to season of repeated fire in a young longleaf pine plantation

Treesearch

Mary Anne Sword Sayer; James D. Haywood

2012-01-01

The potential exists for interaction between naturally high soil bulk density and low soil water content to create root-growth limiting soil strengths. This problem is commonly remedied by soil structural attributes, old root channels and other perturbations, and periods of wetness during which soil strength is favorable for root elongation. Because the application and...

Soil ecology of a rock outcrop ecosystem: Abiotic stresses, soil respiration, and microbial community profiles in limestone cedar glades

USGS Publications Warehouse

Cartwright, Jennifer M.; Advised by Dzantor, E. Kudjo

2015-01-01

Stress factors quantified by this research include shallow soil (depth to bedrock ranging from 2.4 to 22.6 cm), volumetric soil water content levels seasonally ranging from xeric (below 5%) to saturated (above 50%), and seasonally extreme ground-surface temperatures (above 48°C). Findings from this research indicate that spatial and temporal heterogeneity exists in limestone cedar glades in terms of abiotic stress factors and soil physical and chemical properties. Several such soil properties (e.g. soil depth, organic matter levels, pH, and particle size distribution) are spatially correlated. These soil properties were statistically related to ecological structures and functions such as vegetation patterns, soil respiration, the density of culturable heterotrophic microbes in soil and metabolic diversity of soil microbial community profiles. In general, zones within limestone cedar glades that had relatively shallow soil, alkaline pH, low levels of organic matter and high levels of silt also tended to have depressed rates of soil respiration and reduced densities and metabolic diversity of culturable heterotrophic soil microbes. Additionally, seasonally-relevant stress factors including soil water content and temperatures at or near the soil surface were related to the same set of ecological structures and functions.

The Role of Protein-Mineral Interactions for Protein Adsorption or Fragmentation

NASA Astrophysics Data System (ADS)

Chacon, S. S.; Reardon, P.; Washton, N.; Kleber, M.

2014-12-01

Soil exo-enzymes (EE) are proteins with the capability to catalyze the depolymerization of soil organic matter (SOM). SOM must be disassembled by EEs in order to be transported through the microbial cell wall and become metabolized. One factor determining an EE's functionality is their affinity to mineral surfaces found in the soil. Our goal was to establish the range of protein modifications, either chemical or structural, as the protein becomes associated with mineral surfaces. We hypothesized that pedogenic oxides would generate more extensive chemical alterations to the protein structure than phyllosilicates. A well-characterized protein proxy (Gb1, IEP 4.0, 6.2 kDA) was adsorbed onto functionally different mineral surfaces (goethite, montmorillonite, kaolinite and birnesite) at pH 5 and pH 7. We used 1H 15N Heteronuclear Single Quantum Coherence Nuclear Magnetic Resonance Spectroscopy (HSQC NMR) to observe structural modifications in the unadsorbed Gb1 that was allowed to equilibrate during the adsorption process for kaolinite, goethite and birnessite. Solid state NMR was used to observe the structural modifications of Gb1 while adsorbed onto kaolinite and montmorillonite. Preliminary results in the HSQC NMR spectra observed no changes in the native conformation of Gb1 when allowed to interact with goethite and kaolinite while birnessite induced strong structural modification of Gb1 at an acidic pH. Our results suggest that not all mineral surfaces in soil act as sorbents for EEs and changes in their catalytic activity upon adsorption to minerals surfaces may not just be an indication of conformational changes but of fragmentation of the protein itself.

Agriculture on Mars: Soils for Plant Growth

NASA Technical Reports Server (NTRS)

Ming, D. W.

2016-01-01

Robotic rovers and landers have enabled the mineralogical, chemical, and physical characterization of loose, unconsolidated materials on the surface of Mars. Planetary scientists refer to the regolith material as "soil." NASA is currently planning to send humans to Mars in the mid 2030s. Early missions may rely on the use of onsite resources to enable exploration and self-sufficient outposts on Mars. The martian "soil" and surface environment contain all essential plant growth elements. The study of martian surface materials and how they might react as agricultural soils opens a new frontier for researchers in the soil science community. Other potential applications for surface "soils" include (i) sources for extraction of essential plant-growth nutrients, (ii) sources of O2, H2, CO2, and H2O, (iii) substrates for microbial populations in the degradation of wastes, and (iv) shielding materials surrounding outpost structures to protect humans, plants, and microorganisms from radiation. There are many challenges that will have to be addressed by soil scientists prior to human exploration over the next two decades.

Modification of Soil Temperature and Moisture Budgets by Snow Processes

NASA Astrophysics Data System (ADS)

Feng, X.; Houser, P.

2006-12-01

Snow cover significantly influences the land surface energy and surface moisture budgets. Snow thermally insulates the soil column from large and rapid temperature fluctuations, and snow melting provides an important source for surface runoff and soil moisture. Therefore, it is important to accurately understand and predict the energy and moisture exchange between surface and subsurface associated with snow accumulation and ablation. The objective of this study is to understand the impact of land surface model soil layering treatment on the realistic simulation of soil temperature and soil moisture. We seek to understand how many soil layers are required to fully take into account soil thermodynamic properties and hydrological process while also honoring efficient calculation and inexpensive computation? This work attempts to address this question using field measurements from the Cold Land Processes Field Experiment (CLPX). In addition, to gain a better understanding of surface heat and surface moisture transfer process between land surface and deep soil involved in snow processes, numerical simulations were performed at several Meso-Cell Study Areas (MSAs) of CLPX using the Center for Ocean-Land-Atmosphere (COLA) Simplified Version of the Simple Biosphere Model (SSiB). Measurements of soil temperature and soil moisture were analyzed at several CLPX sites with different vegetation and soil features. The monthly mean vertical profile of soil temperature during October 2002 to July 2003 at North Park Illinois River exhibits a large near surface variation (<5 cm), reveals a significant transition zone from 5 cm to 25 cm, and becomes uniform beyond 25cm. This result shows us that three soil layers are reasonable in solving the vertical variation of soil temperature at these study sites. With 6 soil layers, SSiB also captures the vertical variation of soil temperature during entire winter season, featuring with six soil layers, but the bare soil temperature is underestimated and root-zone soil temperature is overestimated during snow melting; which leads to overestimated temperature variations down to 20 cm. This is caused by extra heat loss from upper soil level and insufficient heat transport from the deep soil. Further work will need to verify if soil temperature displays similar vertical thermal structure for different vegetation and soil types during snow season. This study provides insight to the surface and subsurface thermodynamic and hydrological processes involved in snow modeling which is important for accurate snow simulation.

The role of fire on soil mounds and surface roughness in the Mojave Desert

USGS Publications Warehouse

Soulard, Christopher E.; Esque, Todd C.; Bedford, David R.; Bond, Sandra

2013-01-01

A fundamental question in arid land management centers on understanding the long-term effects of fire on desert ecosystems. To assess the effects of fire on surface topography, soil roughness, and vegetation, we used terrestrial (ground-based) LiDAR to quantify the differences between burned and unburned surfaces by creating a series of high-resolution vegetation structure and bare-earth surface models for six sample plots in the Grand Canyon-Parashant National Monument, Arizona. We find that 11 years following prescribed burns, mound volumes, plant heights, and soil-surface roughness were significantly lower on burned relative to unburned plots. Results also suggest a linkage between vegetation and soil mounds, either through accretion or erosion mechanisms such as wind and/or water erosion. The biogeomorphic implications of fire-induced changes are significant. Reduced plant cover and altered soil surfaces from fire likely influence seed residence times, inhibit seed germination and plant establishment, and affect other ecohydrological processes.

Soil physical conditions as livestock treading effect in tropical Agroecosystem of dryland and strategies to mitigate desertification risk

NASA Astrophysics Data System (ADS)

Florentino, A.; Torres, D.; Ospina, A.; Contreras, J.; Palma, Z.; Silvera, J.

2012-04-01

Soil degradation in natural ecosystem of arid and semi-arid zones of Venezuela due to livestock treading (goats) it is an important problem that affect their environment functions; increase soil erodibility, bulk density, water losses and reduce porosity, water infiltration rate and soil structural stability. The presence of biological crust (BSC) in this type of soil it is very common. The objective of this study was to evaluate the soil surface physical quality through the use of selected indicators, mainly some of that related to structural stability, infiltrability and the prediction of soil erosion risk in two zones of Lara state: 1) Quíbor (QUI) and 2) Humocaro Bajo (HB). The study was conducted on two selected plots (30 m x 20 m) in each zone, with natural vegetation and BSC cover, with areas affected by different degree of compaction due to treading in the paths where the goats are moving. Five sites per plot (50 cm x 50 cm) under vegetation cover and five sites over the path with bare soil were sampled (0-7,5 and 7,5-15 cm depth). The results showed that soil macroaggregate stability (equivalent diameter of aggregates >0,25 mm) was significantly higher (p<0,05 %) in soil with vegetation cover and BSC compared with bare soil. Sealing index, as a measure of aggregate stability, determined in laboratory under simulated rain and expressed as hydraulic conductivity of soil surface sealing (Kse), decreased with decreasing soil vegetation cover and the presence of BSC. However, Ksei (i: inicial) and Ksef (f: final) were significantly greater in soil with more than 75 % of BSC in comparison to bare soils. The sealing index it is used to for to estimate changes in soil water losses. As the sealing index increases, the susceptibility of the soil to undergo surface sealing or slaking decrease. These results suggested that soil physical properties are potential indicators of soil quality with regard to soil erodibility and showed that soils under vegetation cover had higher quality level than bare soils. Some predictive regression equation had a high R2 value and was a useful tool for to evaluate the risk of extreme climatic changes and to mitigate their detrimental effects. We conclude that the global climatic change (CCG) will have a negative effect on these agroecosystems functions, mainly in soil and water conservation, carbon sequestration, and productivity. Natural recovery of soil physical properties from treading damage of pastoral soils will be possible in the future with the implementation of soil management strategies, mainly through re-vegetation and recuperation of the BSC. Key word: Soil structure; aggregate stability; soil sealing index; hydraulic conductivity of surface sealing.

[Effects of several low-molecular-weight organic acids on the release kinetic of endosulfan from red soil].

PubMed

Zhao, Zhen-hua; Wu, Yu; Jiang, Xin; Xia, Li-ling; Ni, Li-xiao

2009-10-15

The kinetic release behaviors of a-endosulfan from red soil with three kinds of low-molecular-weight organic acids (LMWOA: oxalate, tartrate and citrate) solution and water leaching were investigated by kinetic device designed by ourselves and batch method. The results show that: the release percentage of endosulfan from red soil by tartrate and citrate solution (10 mmol/L) can increase by 7%-18% more than that by distilled water and oxalate solution, especially for tartrate solution. There is no significant difference between distilled water and oxalate solution for the release percentage of endosulfan (p > 0.05). There are two stages of quick and slow for the release of endosulfan from red soil, and the leaching speed is quicker especially for the initial 200 mL leaching solution. When using distilled water or oxalate solution as leaching solution, the best equations that described the kinetic release behavior of endosulfan from red soil were parabola diffuse equation and double constant equation, and weren't the apparent first dynamics equation that represented the simple surface diffusion mechanism. The kinetic release behavior of endosulfan in tartrate or citrate leaching system can be described by Elovich equation (R2 > 0.99, p < 0.0001), it implied that the simple surface diffusion mechanism is not the primary factor that effected the release of endosulfan, which three-dimensional molecule structure is complex, from red soil in aqueous phase leaching systems, and it maybe related to the outward diffuse mechanism from soil particle, activation and deactivation function of soil particles surface, the dissolution of soil mineral surface and structure change of inherent organic matter that coating onto the soil mineral surface induced by LMW organic acid. It suggested that the tartrate and citrate induced the complication of the release mechanisms of the pesticides from red soil.

Macroscopic and molecular approaches of enrofloxacin retention in soils in presence of Cu(II).

PubMed

Graouer-Bacart, Mareen; Sayen, Stéphanie; Guillon, Emmanuel

2013-10-15

The co-adsorption of copper and the fluoroquinolone antibiotic enrofloxacin (ENR) at the water-soil interface was studied by means of batch adsorption experiments, and extended X-ray absorption fine structure (EXAFS) spectroscopy. The system was investigated over a pH range between 6 and 10, at different contact times, ionic strengths, and ENR concentrations. Adsorption coefficient - Kd - was determined at relevant environmental concentrations and the value obtained in water at a ionic strength imposed by the soil and at soil natural pH was equal to 0.66Lg(-1). ENR adsorption onto the soil showed strong pH dependence illustrating the influence of the electrostatic interactions in the sorption processes. The simultaneous co-adsorption of ENR and Cu(II) on the soil was also investigated. The presence of Cu(II) strongly influenced the retention of the antibiotic, leading to an increase up to 35% of adsorbed ENR amount. The combined quantitative and spectroscopic results showed that Cu(II) and ENR directly interacted at the water-soil interface to form ternary surface complexes. Cu K-edge EXAFS data indicated a molecular structure where the carboxylate and carbonyl groups of ENR coordinate to Cu(II) to form a 6-membered chelate ring and where Cu(II) bridges between ENR and the soil surface sites. Cu(II) bonds bidentately to the surface in an inner-sphere mode. Thus, the spectroscopic data allowed us to propose the formation of ternary surface complexes with the molecular architecture soil-Cu(II)-ENR. Copyright © 2013 Elsevier Inc. All rights reserved.

Microbial community responses in forest mineral soil to compaction, organic matter removal, and vegetation control

Treesearch

Matt D. Busse; Samual E. Beattie; Robert F. Powers; Felipe G. Sanchez; Allan E. Tiarks

2006-01-01

We tested three disturbance hypotheses in young conifer plantations: H1: soil compaction and removal of surface organic matter produces sustained changes in microbial community size, activity, and structure in mineral soil; H2: microbial community characteristics in mineral soil are linked to the recovery of plant diversity...

Mycorrhizas and soil ecosystem function of co-existing woody vegetation islands at the alpine tree line.

PubMed

Wang, Lixia; Otgonsuren, Burenjargal; Godbold, Douglas L

2017-01-01

Picea abies , Pinus mugo and Rhododendron ferrugineum co-exist at the alpine tree line, and can have different mycorrhizal communities. The activity and diversity of mycorrhizal fungi are considered to be important factors in regulation of soil function. At a tree line site and a lower elevation site in the Austrian Alps, the community structure of ectomycorrhiza on Picea abies and Pinus mugo was determined. The activity of surface enzymes was determined on ectomycorrhizal and ericoid mycorrhizal roots. In soils, the activity of a range of enzymes, nitrogen (N) mineralization and biomass decomposition were determined. The community structure of the ectomycorrhizal community of Picea abies and Pinus mugo differed strongly, but the average activity of surface enzymes of the ectomycorrhizal communities was similar. A lower root surface enzyme activity was determined on Rhododendron ferrugineum . Soil N-mineralization under Rhododendron ferrugineum was significantly lower than under Picea abies and Pinus mugo . In soil, the activity of a range of enzymes did not differ at the tree line but differed between the tree line and the lower elevation sites. The different ectomycorrhizal communities on Picea abies and Pinus mugo and ericoid mycorrhizas on Rhododendron ferrugineum support similar ecosystem functions in soil.

A Comparison of Relative Abundance and Biomass of Ground-Dwelling Arthropods Under Different Forest Management Practices

Treesearch

Cathryn H. Greenberg; Arlene McGrane

1996-01-01

Habitat structural characteristics and relative abundance and biomass of ground-dwelling arthropods were compared among four replicated stand treatments: intense burning and salvage logging; clearcutting followed by roller-chopping (100% soil surface disturbance): clearcutting followed by bracke seeding (30% soil surface disturbance); and naturally regenerated mature...

The error structure of the SMAP single and dual channel soil moisture retrievals

USDA-ARS?s Scientific Manuscript database

Knowledge of the temporal error structure for remotely-sensed surface soil moisture retrievals can improve our ability to exploit them for hydrology and climate studies. This study employs a triple collocation type analysis to investigate both the total variance and temporal auto-correlation of erro...

Soil sealing and vesicular layer formation as initial structure development and its effect on infiltration

NASA Astrophysics Data System (ADS)

Badorreck, A.; Gerke, H. H.; Weller, U.; Vontobel, P.

2009-04-01

In the Lusatia mining district (NE-Germany) an artificial catchment was constructed to study initial ecosystem development and runoff generation. As a key process in this early stage, we investigate the surface structure dynamics as it strongly influences erosion, infiltration, matter dynamics, and vegetation establishment. The presented work focuses on observations of soil pore structure formation at the surface at five sites in the catchment and in an adjacent "younger" area composed of comparable sediments. Moreover we've conducted infiltration experiments in the lab and field to relate the soil pore structure to the hydraulic properties. The surface soil was sampled in cylindrical rings (10 cm³) down to 2 cm depth from which bulk density profiles were obtained using X-ray computed tomography (CT) (at UFZ- Halle, Germany) with a resolution of 0.084 mm. The influence of structure on infiltration was investigated using neutron radiography (at the NEUTRA facility of the Paul-Scherrer-Institut, Villigen, Switzerland) to visualise two-dimensional (2D) infiltration patterns. The slab-type samples were equilibrated to different initial water contents and then exposed to drip irrigation (to simulate rainfall) while a series of neutron radiographs were taken. In addition, field measurements with a miniature tension infiltrometer were conduced. The micro-tomographies exhibit formation of surface sealing whose thickness and intensity vary with silt and clay content. The CT images show several coarser- and finer-textured micro-layers at the sample surfaces that were formed as a consequence of repeated washing in of finer particles in underlying coarser sediment. In micro-depressions, the uppermost layers consist of sorted fine sand and silt due to wind erosion. Similar as for desert pavements, a vesicular pore structure developed in these sediments on top, but also scattered in fine sand- and silt-enriched micro-layers. The infiltration rates were severely affected by the surface crusts; however, the rates were independent of the vesicular pore layer.

Structural equation modeling of PAHs in ambient air, dust fall, soil, and cabbage in vegetable bases of Northern China.

PubMed

Zhang, YunHui; Hou, DeYi; Xiong, GuanNan; Duan, YongHong; Cai, ChuanYang; Wang, Xin; Li, JingYa; Tao, Shu; Liu, WenXin

2018-08-01

A series of field samples including ambient air (gaseous and particulate phases), dust fall, surface soil, rhizosphere soil and cabbage tissues (leaf, root and core), were collected in vegetable bases near a large coking manufacturer in Shanxi Province, Northern China, during a harvest season. A factor analysis was employed to apportion the emission sources of polycyclic aromatic hydrocarbons (PAHs), and the statistical results indicated coal combustion was the dominant emission source that accounted for different environmental media and cabbage tissues, while road traffic, biomass burning and the coking industry contributed to a lesser extent. A structural equation model was first developed to quantitatively explore the transport pathways of PAHs from surrounding media to cabbage tissues. The modeling results showed that PAHs in ambient air were positively associated with those in dust fall, and a close relationship was also true for PAHs in dust fall and in surface soil due to air-soil exchange process. Furthermore, PAHs in surface soil were correlated with those in rhizosphere soil and in the cabbage leaf with the path coefficients of 0.83 and 0.39, respectively. PAHs in the cabbage leaf may dominantly contribute to the accumulation of PAHs in the edible part of cabbages. Copyright © 2018 Elsevier Ltd. All rights reserved.

Directional reflectance factors for monitoring spatial changes in soil surface structure and soil organic matter erosion in agricultural systems

NASA Astrophysics Data System (ADS)

Croft, H.; Anderson, K.

2012-04-01

Soils can experience rapid structural degradation in response to land cover changes, resulting in reduced soil productivity, increased erodibility and a loss of soil organic matter (SOM). The breakdown of soil aggregates through slaking and raindrop impact is linked to organic matter turnover, with subsequently eroded material often displaying proportionally more SOM. A reduction in aggregate stability is reflected in a decline in soil surface roughness (SSR), indicating that a soil structural change can be used to highlight soil vulnerability to SOM loss through mineralisation or erosion. Accurate, spatially-continuous measurements of SSR are therefore needed at a variety of spatial and temporal scales to understand the spatial nature of SOM erosion and deposition. Remotely-sensed data can provide a cost-effective means of monitoring changes in soil surface condition over broad spatial extents. Previous work has demonstrated the ability of directional reflectance factors to monitor soil crusting within a controlled laboratory experiment, due to changes in the levels of self-shadowing effects by soil aggregates. However, further research is needed to test this approach in situ, where other soil variables may affect measured reflectance factors and to investigate the use of directional reflectance factors for monitoring soil erosion processes. This experiment assesses the potential of using directional reflectance factors to monitor changes in SSR, aggregate stability and soil organic carbon (SOC) content for two agricultural conditions. Five soil plots representing tilled and seedbed soils were subjected to different durations of natural rainfall, producing a range of different levels of SSR. Directional reflectance factors were measured concomitantly with sampling for soil structural and biochemical tests at each soil plot. Soil samples were taken to measure aggregate stability (wet sieving), SOC (loss on ignition) and soil moisture (gravimetric method). SSM values varied from 8.70 to 20.05% and SOC from 1.33 to 1.05%, across all soil plots. Each plot was characterised using a close-range laser scanning device with a 2 mm sampling interval. The point laser data were geostatistically analysed to provide a spatially-distributed measure of SSR, giving sill variance values from 3.15 to 22.99. Reflectance factors from the soil states were measured using a ground-based hyperspectral spectroradiometer (400-2500 nm) attached to an A-frame device. This method allowed measurement at a range of viewing zenith angles from extreme forwardscatter (-60°) to extreme backscatter (+60°) at a 10° sampling resolution in the solar principal plane. Reflectance measurements were compared to geostatistically-derived indicators of SSR from the laser profile data. Forward-scattered reflectance factors exhibited a very strong relationship to SSR (R2 = 0.84 at -60°; p< 0.05), demonstrating the operational potential of directional reflectance for providing SSR measurements, despite conflicting variation in SSM. SSM also presented an interesting directional signal (R2 = 0.99 at +20°; p< 0.01). Furthermore, the results showed an important link between SRR decline as measured using directional reflectance, with a decline in aggregate stability and SOC content. These findings provide an empirical and theoretical basis for the future retrieval of spatially-continuous assessments of soil surface structure and carbon turnover within a landscape context.

Wettability of natural root mucilage studied by atomic force microscopy and contact angle: Links between nanoscale and macroscale surface properties

NASA Astrophysics Data System (ADS)

Kaltenbach, Robin; Diehl, Dörte; Schaumann, Gabriele E.

2017-04-01

Organic coatings are considered as main cause of soil water repellency (SWR). This phenomenon plays a crucial role in the rhizosphere, at the interface of plant water uptake and soil hydraulics. Still, there is little knowledge about the nanoscale properties of natural soil compounds such as root-mucilage and its mechanistic effect on wettability. In this study, dried films of natural root-mucilage from Sorghum (Sorghum sp., MOENCH) on glass substrates were studied in order to explore experimental and evaluation methods that allow to link between macroscopic wettability and nano-/microscopic surface properties in this model soil system. SWR was assessed by optical contact angle (CA) measurements. The nanostructure of topography and adhesion forces of the mucilage surfaces was revealed by atomic force microscopy (AFM) measurements in ambient air, using PeakForce Quantitative Nanomechanical Mapping (PFQNM). Undiluted mucilage formed hydrophobic films on the substrate with CA > 90° and rather homogeneous nanostructure. Contact angles showed reduced water repellency of surfaces, when concentration of mucilage was decreased by dilution. AFM height and adhesion images displayed incomplete mucilage surface coverage for diluted samples. Hole-like structures in the film frequently exhibited increased adhesion forces. Spatial analysis of the AFM data via variograms enabled a numerical description of such 'adhesion holes'. The use of geostatistical approaches in AFM studies of the complex surface structure of soil compounds was considered meaningful in view of the need of comprehensive analysis of large AFM image data sets that exceed the capability of comparative visual inspection. Furthermore, force curves measured with the AFM showed increased break-free distances and pull-off forces inside the observed 'adhesion holes', indicating enhanced capillary forces due to adsorbed water films at hydrophilic domains for ambient RH (40 ± 2 %). This offers the possibility of mapping the nanostructure of water layers on soil surfaces and assessing the consequences for wettability. The collected information on macroscopic wetting properties, nanoscale roughness and adhesion structure of the investigated surfaces in this study are discussed in view of the applicability of the mechanistic wetting models given by Wenzel and Cassie-Baxter.

[Priming effect of biochar on the minerialization of native soil organic carbon and the mechanisms: A review.

PubMed

Chen, Ying; Liu, Yu Xue; Chen, Chong Jun; Lyu, Hao Hao; Wa, Yu Ying; He, Li Li; Yang, Sheng Mao

2018-01-01

In recent years, studies on carbon sequestration of biochar in soil has been in spotlight owing to the specific characteristics of biochar such as strong carbon stability and well developed pore structure. However, whether biochar will ultimately increase soil carbon storage or promote soil carbon emissions when applied into the soil? This question remains controversial in current academic circles. Further research is required on priming effect of biochar on mineralization of native soil organic carbon and its mechanisms. Based on the analysis of biochar characteristics, such as its carbon composition and stability, pore structure and surface morphology, research progress on the priming effect of biochar on the decomposition of native soil organic carbon was reviewed in this paper. Furthermore, possible mechanisms of both positive and negative priming effect, that is promoting and suppressing the mineralization, were put forward. Positive priming effect is mainly due to the promotion of soil microbial activity caused by biochar, the preferential mineralization of easily decomposed components in biochar, and the co-metabolism of soil microbes. While negative priming effect is mainly based on the encapsulation and adsorption protection of soil organic matter due to the internal pore structure and the external surface of biochar. Other potential reasons for negative priming effect can be the stabilization resulted from the formation of organic-inorganic complex promoted by biochar in the soil, and the inhibition of activity of soil microbes and its enzymes by biochar. Finally, future research directions were proposed in order to provide theoretical basis for the application of biochar in soil carbon sequestration.

Principles of control automation of soil compacting machine operating mechanism

NASA Astrophysics Data System (ADS)

Anatoly Fedorovich, Tikhonov; Drozdov, Anatoly

2018-03-01

The relevance of the qualitative compaction of soil bases in the erection of embankment and foundations in building and structure construction is given.The quality of the compactible gravel and sandy soils provides the bearing capability and, accordingly, the strength and durability of constructed buildings.It has been established that the compaction quality depends on many external actions, such as surface roughness and soil moisture; granulometry, chemical composition and degree of elasticity of originalfilled soil for compaction.The analysis of technological processes of soil bases compaction of foreign and domestic information sources showed that the solution of such important problem as a continuous monitoring of soil compaction actual degree in the process of machine operation carry out only with the use of modern means of automation. An effective vibrodynamic method of gravel and sand material sealing for the building structure foundations for various applications was justified and suggested.The method of continuous monitoring the soil compaction by measurement of the amplitudes and frequencies of harmonic oscillations on the compactible surface was determined, which allowed to determine the basic elements of facilities of soil compacting machine monitoring system of operating, etc. mechanisms: an accelerometer, a bandpass filter, a vibro-harmonics, an on-board microcontroller. Adjustable parameters have been established to improve the soil compaction degree and the soil compacting machine performance, and the adjustable parameter dependences on the overall indexhave been experimentally determined, which is the soil compaction degree.A structural scheme of automatic control of the soil compacting machine control mechanism and theoperation algorithm has been developed.

Determination of Martian soil mineralogy and water content using the Thermal Analyzer for Planetary Soils (TAPS)

NASA Technical Reports Server (NTRS)

Gooding, James L.; Ming, Douglas W.; Allton, Judith H.; Byers, Terry B.; Dunn, Robert P.; Gibbons, Frank L.; Pate, Daniel B.; Polette, Thomas M.

1992-01-01

Physical and chemical interactions between the surface and atmosphere of Mars can be expected to embody a strong cause-and-effect relationship with the minerals comprising the martian regolith. Many of the minerals in soils and sediments are probably products of chemical weathering (involving surface/atmosphere or surface/hydrosphere reactions) that could be expected to subsequently influence the sorption of atmospheric gases and water vapor. Therefore, identification of the minerals in martian surface soils and sediments is essential for understanding both past and present interactions between the Mars surface and atmosphere. Clearly, the most definitive mineral analyses would be achieved with well-preserved samples returned to Earth-based laboratories. In advance of a Mars sample return mission, however, significant progress could be made with in situ experiments that fill current voids in knowledge about the presence or abundance of key soil minerals such as clays (layered-structured silicates), zeolites, and various salts, including carbonates. TAPS is intended to answer that challenge by providing first-order identification of soil and sediment minerals.

Differentiate responses of soil structure to natural vegetation and artificial plantation in landslide hazard region of the West Qinling Mountains, China

NASA Astrophysics Data System (ADS)

Wang, X.; Huang, Z.; Zhao, Y.; Hong, M.

2017-12-01

Natural vegetation and artificial plantation are the most important measures for ecological restoration in soil erosion and landslide hazard-prone regions of China. Previous studies have demonstrated that both measures can significantly change the soil structure and decrease soil and water erosion. Few reports have compared the effects of the two contrasting measures on mechanical and hydrological properties and further tested the differentiate responses of soil structure. In the study areas, two vegetation restoration measures-natural vegetation restoration (NVR) and artificial plantation restoration (APR) compared with control site, with similar topographical and geological backgrounds were selected to investigate the different effects on soil structure based on eight-year ecological restoration projects. The results showed that the surface vegetation played an important role in releasing soil erosion and enhance soil structure stability through change the soil aggregates (SA) and total soil porosity (TSP). The SA<0.25mm content in NVR (36.13%) was higher than that in APR (32.14%). The study indicated that SA and TSP were the principal components (PCs) related to soil structure variation. Soil organic carbon, soil water retention, clay and vegetation biomass were more strongly correlated with the PCs in NVR than those in APR. The study indicated that NVR was more beneficial for soil structure stability than APR. These findings will provide a theoretical basis for the decisions around reasonable land use for ecological restoration and conservation in geological hazard-prone regions.

Distribution of rock fragments and their effects on hillslope soil erosion in purple soil, China

NASA Astrophysics Data System (ADS)

Wang, Xiaoyan

2017-04-01

Purple soil is widely distributed in Sichuan Basin and Three Gorges Reservoir Area. Purple soil region is abundant in soil fertility and hydrothermal resources, playing an important role in the agricultural development of China. Soil erosion has long been recognized as a major environmental problem in the purple soil region where the population is large and slope farming is commonly practiced, and rainstorm is numerous. The existence of rock fragments is one of the most important characteristics of purple soil. Rock fragments at the soil surface or in the soil layer affect soil erosion processes by water in various direct and indirect ways, thus the erosion processes of soil containing rock fragments have unique features. Against the severe soil degradation by erosion of purple soil slope, carrying out the research about the characteristics of purple soil containing rock fragments and understanding the influence of rock fragments on soil erosion processes have important significance, which would promote the rational utilization of purple soil slope land resources and accurate prediction of purple soil loss. Therefore, the aims of this study were to investigate the distribution of rock fragments in purple soil slope and the impact of rock fragment content on soil physical properties and soil erosion. First, field sampling methods were used to survey the spatial variability of rock fragments in soil profiles and along slope and the physical properties of soils containing rock fragments. Secondly, indoor simulated rainfall experiments were used to exam the effect of rock fragments in the soil layer on soil erosion processes and the relationships between rainfall infiltration, change of surface flow velocity, surface runoff volume and sediment on one hand, and rock fragment content (Rv, 0% 30%, which was determined according the results of field investigation for rock fragment distribution) on the other were investigated. Thirdly, systematic analysis about the influence of rock fragment cover on purple soil slope erosion process were carried on, under different conditions with two kind of rock fragment positions (resting on soil surface and embedded into top soil layer), varied rock fragment coverage (Rc, 0% 40%), two kind of soils with textural porosity or structural porosity, and three kind of rainfall intensities (I, 1 mm/min, 1.5 mm/min and 2 mm/min). Simulated rainfall experiments in situ plots in the field, combined with simulated rainfall experiments in soil pans indoor, were used. The main conclusions of this dissertation are as following: 1. The spatial distribution characteristics of rock fragments in purple soil slope and its effects on the soil physical properties were clarified basically. 2. The mechanism of influence of rock fragments within top soil layer on soil erosion processes was understood and a threshold of rock fragment content on the infiltration was figured out. 3. The relationships between surface rock fragment cover and hillslope soil erosion in purple soil under different conditions with varied rock fragment positions, soil structures and rainfall intensities were obtained and the soil and water conservation function of surface rock fragment cover on reducing soil loss was affirmed.

Tellurium Distribution and Speciation in Contaminated Soils from Abandoned Mine Tailings: Comparison with Selenium.

PubMed

Qin, Hai-Bo; Takeichi, Yasuo; Nitani, Hiroaki; Terada, Yasuko; Takahashi, Yoshio

2017-06-06

The distribution and chemical species of tellurium (Te) in contaminated soil were determined by a combination of microfocused X-ray fluorescence (μ-XRF), X-ray diffraction (μ-XRD), and X-ray absorption fine structure (μ-XAFS) techniques. Results showed that Te was present as a mixture of Te(VI) and Te(IV) species, while selenium (Se) was predominantly present in the form of Se(IV) in the soil contaminated by abandoned mine tailings. In the contaminated soil, Fe(III) hydroxides were the host phases for Se(IV), Te(IV), and Te(VI), but Te(IV) could be also retained by illite. The difference in speciation and solubility of Se and Te in soil can result from different structures of surface complexes for Se and Te onto Fe(III) hydroxides. Furthermore, our results suggest that the retention of Te(IV) in soil could be relatively weaker than that of Te(VI) due to structural incorporation of Te(VI) into Fe(III) hydroxides. These findings are of geochemical and environmental significance for better understanding the solubility, mobility, and bioavailability of Te in the surface environment. To the best of our knowledge, this is the first study reporting the speciation and host phases of Te in field soil by the μ-XRF-XRD-XAFS techniques.

Using the Subsurface Soil Sounding Radar for Investigating the Structure and Total Electron Content of the Martian Ionosphere

NASA Astrophysics Data System (ADS)

Smirnov, V. M.; Yushkova, O. V.; Marchuk, V. N.

2018-05-01

The possibilities of using the Martian soil subsurface sounding radar for investigating the structure of the plasma shell surrounding the planet have been considered. Based on the numerical modeling results and actual soil sounding data, it has been shown that the soil sounding mode of the radio-locating MARSIS radar can be used to assess the structure of the Martian ionosphere. As the emitted signals pass to the planet's surface, it is possible to use the reflected signals to estimate the total electron content of the Martian ionosphere along the flight track of the spacecraft.

[Effects of Phyllostachys edulis cultivation on soil bacterial and fungal community structure and diversity].

PubMed

Zhao, Tian Xin; Mao, Xin Wei; Cheng, Min; Chen, Jun Hui; Qin, Hua; Li, Yong Chun; Liang, Chen Fei; Xu, Qiu Fang

2017-11-01

This study examined how soil bacterial and fungal communities responded to the cultivation history of Moso bamboo in Anji and Changxing counties, Huzhou, Zhejiang, China. Soil samples (0-20 and 20-40 cm) were taken from bamboo plantations subjected to different cultivation histories and analyzed the community structures of soil bacterial and fungal by PCR-DGGE methods. It was found that soil bacterial and fungal communities varied greatly with the development of bamboo plantations which converted from Masson pine forest or formed via invading adjacent broadleaf shrub forest. Soil bacterial community structures exhibited a greater response to bamboo cultivation time than fungal community, but bacteria structure of surface soil displayed an ability of resiliency to disturbance and the tendency to recover to the original state. The cultivation time, sampling site and soil layer significantly affected the biodiversity of soil bacteria and fungi, especially the latter two factors. Redundancy analysis (RDA) of soil properties and bacteria or fungi communities showed that there were no accordant factors to drive the alteration of microbial structure, and the first two axes explained less than 65.0% of variance for most of the sampling sites and soil layers, indicating there existed soil parameters besides the five examined that contributed to microbial community alteration.

The Effects of Subsurface Bioremediation on Soil Structure, Colloid Formation, and Contaminant Transport

NASA Astrophysics Data System (ADS)

Wang, Y.; Liang, X.; Zhuang, J.; Radosevich, M.

2016-12-01

Anaerobic bioremediation is widely applied to create anaerobic subsurface conditions designed to stimulate microorganisms that degrade organic contaminants and immobilize toxic metals in situ. Anaerobic conditions that accompany such techniques also promotes microbially mediated Fe(III)-oxide mineral reduction. The reduction of Fe(III) could potentially cause soil structure breakdown, formation of clay colloids, and alternation of soil surface chemical properties. These processes could then affect bioremediation and the migration of contaminants. Column experiments were conducted to investigate the impact of anaerobic bioreduction on soil structure, hydraulic properties, colloid formation, and transport of three tracers (bromide, DFBA, and silica shelled silver nanoparticles). Columns packed with inoculated water stable soil aggregates were placed in anaerobic glovebox, and artificial groundwater media was pumped into the columns to simulate anaerobic bioreduction process for four weeks. Decent amount of soluble Fe(II) accompanied by colloids were detected in the effluent from bioreduction columns a week after initiation of bioreduction treatment, which demonstrated bioreduction of Fe(III) and formation of colloids. Transport experiments were performed in the columns before and after bioreduction process to assess the changes of hydraulic and surface chemical properties through bioreduction treatment. Earlier breakthrough of bromide and DFBA after treatment indicated alterations in flow paths (formation of preferential flow paths). Less dispersion of bromide and DFBA, and less tailing of DFBA after treatment implied breakdown of soil aggregates. Dramatically enhanced transport and early breakthrough of silica shelled silver nanoparticles after treatment supported the above conclusion of alterations in flow paths, and indicated changes of soil surface chemical properties.

Zambia Wetland

Atmospheric Science Data Center

2013-04-16

... and are influenced by terrain, vegetation structure, soil type and soil moisture content. Wet surfaces or areas with standing water ... NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Science Mission Directorate, Washington, D.C. The Terra spacecraft is managed ...

Multiscale analysis of surface soil moisture dynamics in a mesoscale catchment utilizing an integrated ecohydrological model

NASA Astrophysics Data System (ADS)

Korres, W.; Reichenau, T. G.; Schneider, K.

2012-12-01

Soil moisture is one of the fundamental variables in hydrology, meteorology and agriculture, influencing the partitioning of solar energy into latent and sensible heat flux as well as the partitioning of precipitation into runoff and percolation. Numerous studies have shown that in addition to natural factors (rainfall, soil, topography etc.) agricultural management is one of the key drivers for spatio-temporal patterns of soil moisture in agricultural landscapes. Interactions between plant growth, soil hydrology and soil nitrogen transformation processes are modeled by using a dynamically coupled modeling approach. The process-based ecohydrological model components of the integrated decision support system DANUBIA are used to identify the important processes and feedbacks determining soil moisture patterns in agroecosystems. Integrative validation of plant growth and surface soil moisture dynamics serves as a basis for a spatially distributed modeling analysis of surface soil moisture patterns in the northern part of the Rur catchment (1100 sq km), Western Germany. An extensive three year dataset (2007-2009) of surface soil moisture-, plant- (LAI, organ specific biomass and N) and soil- (texture, N, C) measurements was collected. Plant measurements were carried out biweekly for winter wheat, maize, and sugar beet during the growing season. Soil moisture was measured with three FDR soil moisture stations. Meteorological data was measured with an eddy flux station. The results of the model validation showed a very good agreement between the modeled plant parameters (biomass, green LAI) and the measured parameters with values between 0.84 and 0.98 (Willmotts index of agreement). The modeled surface soil moisture (0 - 20 cm) showed also a very favorable agreement with the measurements for winter wheat and sugar beet with an RMSE between 1.68 and 3.45 Vol.-%. For maize, the RMSE was less favorable particularly in the 1.5 months prior to harvest. The modeled soil moisture remained in contrast to the measurements very responsive to precipitation with high soil moisture after precipitation events. This behavior indicates that the soil properties might have changed due to the formation of a surface crust or seal towards the end of the growing season. Spatial soil moisture patterns were investigated using a grid resolution of 150 meter. Spatial autocorrelation was computed on a daily basis using patterns of soil texture as well as transpiration and precipitation indices as co-variables. Spatial patterns of surface soil moisture are mostly determined by the structure of the soil properties (soil type) during winter, early growing season and after harvest of all crops. Later in the growing season, after establishment of a closed canopy the dependence of the soil moisture patterns on soil texture patterns becomes smaller and diminishes quickly after precipitation events, due to differences of the transpiration rate of the different crops. When changing the spatial scale of the analysis, the highest autocorrelation values can be found on a grid cell size between 450 and 1200 meters. Thus, small scale variability of transpiration induced by the land use pattern almost averages out, leaving the larger scale structure of soil properties to explain the soil moisture patterns.

Soil analyses and evaluations at the impact dynamics research facility for two full-scale aircraft crash tests

NASA Technical Reports Server (NTRS)

Cheng, R. Y. K.

1977-01-01

The aircraft structural crash behavior and occupant survivability for aircraft crashes on a soil surface was studied. The results of placement, compaction, and maintenance of two soil test beds are presented. The crators formed by the aircraft after each test are described.

Load dissipation by corn residue on tilled soil in laboratory and field-wheeling conditions.

PubMed

Reichert, José M; Brandt, André A; Rodrigues, Miriam F; Reinert, Dalvan J; Braida, João A

2016-06-01

Crop residues may partially dissipate applied loads and reduce soil compaction. We evaluated the effect of corn residue on energy-applied dissipation during wheeling. The experiment consisted of a preliminary laboratory test and a confirmatory field test on a Paleaudalf soil. In the laboratory, an adapted Proctor test was performed with three energy levels, with and without corn residue. Field treatments consisted of three 5.1 Mg tractor wheeling intensities (0, 2, and 6), with and without 12 Mg ha(-1) corn residue on the soil surface. Corn residue on the soil surface reduced soil bulk density in the adapted Proctor test. By applying energy of 52.6 kN m m(-3) , soil dissipated 2.98% of applied energy, whereas with 175.4 kN m m(-3) a dissipation of 8.60% was obtained. This result confirms the hypothesis that surface mulch absorbs part of the compaction effort. Residue effects on soil compaction observed in the adapted Proctor test was not replicated under subsoiled soil field conditions, because of differences in applied pressure and soil conditions (structure, moisture and volume confinement). Nevertheless, this negative result does not mean that straw has no effect in the field. Such effects should be measured via stress transmission and compared to soil load-bearing capacity, rather than on bulk deformations. Wheeling by heavy tractor on subsoiled soil increased compaction, independently of surface residue. Two wheelings produced a significantly increase, but six wheelings did not further increase compaction. Reduced traffic intensity on recently tilled soil is necessary to minimize soil compaction, since traffic intensity show a greater effect than surface mulch on soil protection from excessive compaction. © 2015 Society of Chemical Industry. © 2015 Society of Chemical Industry.

Derivation of thermokarst distribution based on climate and surface characteristics

NASA Astrophysics Data System (ADS)

Schöngaßner, Thomas; Hagemann, Stefan

2013-04-01

About one quarter of the northern hemisphere is covered by permafrost. Permafrost areas inherit a high amount of deposited soil organic carbon, which represents approximately 50% of the estimated global below-ground organic carbon pool and is more than twice the size of the current atmospheric carbon pool. A destabilization due to the expected amplitude of future Arctic climate warming would lead to a global-scale feedback mechanism. This feedback comprise interactions between snow, permafrost, hydrology, and ecosystems, which include altered energy and water fluxes between atmosphere and land surface. The representation of permafrost related processes in GCMs and ESMs is still rudimentary and needs to be extended to improve the climate model performance in high latitudes. In this sense thermokarst processes should be included into JSBACH, the land-surface component of MPI-ESM. Initially, a 1-D scheme of thermal dynamics will be implemented into JSBACH, which fits into very recent developments with regards to permafrost melting and freezing (T. Blome; Ekici et al., in prep.) and a dynamical wetland scheme (Stacke and Hagemann, 2012). Structural improvements and new parametrization of the model are required with regard to heat and water flow (physical processes) and carbon and nitrogen dynamics (bio-geochemical processes). The implementation of a thermokarst module is one task within the EU project PAGE21 and is a joint activity between MPI-M Hamburg and MPI-BGC Jena. Thermokarst changes are coupled thermal-hydrological processes, which lead to an enhanced thawing of ice-rich permafrost on local-to-regional scales, where the soil structure is characterized by segregated ice and ice-wedges. They result in severe consequences for soil structure, hydrology, and depletion of soil organic carbon. Thermokarst affected areas appear as a very uneven surface of hummocks and marshy hollows. The initial heat balance of the surface is disturbed by different trigger mechanisms, which cause the ground ice to melt and the soil to subside into depressions due to developing cavities in the interior. The depressions fill up with melting and precipitating water. Since deeper water bodies do not freeze up entirely, the annual mean surface temperature increases in the soil beneath. Therefore permafrost thawing is continued and depressions grow further due to soil subsidence and slope wash at the margins until a new soil surface heat balance is reached. Here I'd like to give a short overview and an introduction into the ongoing thermokarst process in the Arctic tundra. The main focus will be on investigating the actual distribution of thermokarst lakes in the high northern latitudes. The development of thermokarst lakes depends on soil parameters like ice content, surface temperature, soil texture as well as on climate states like monthly mean temperature, precipitation, winter snow depth. They contribute to the surface heat balance and may serve as a measure for thermokarst potential. Since thermokarst mechanism is a small-scale process of 10-1000m in spatial extent, it needs to be parametrized for GCM applications on ESM grid scale. Thus, we want to derive the thermokarst distribution as a function of climate and soil parameters.

Warming Effects on Enzyme Activities are Predominant in Sub-surface Soils of an Arctic Tundra Ecosystem over 6-Year Field Manipulation

NASA Astrophysics Data System (ADS)

Kang, H.; Seo, J.; Kim, M.; Jung, J. Y.; Lee, Y. K.

2017-12-01

Arctic tundra ecosystems are of great importance because they store a large amount of carbon as un-decomposed organic matter. Global climate change is expected to affect enzyme activities and heterotrophic respiration in Arctic soils, which may accelerate greenhouse gas (GHG) emission through positive biological feedbacks. Unlike laboratory-based incubation experiments, field measurements often show different warming effects on decomposition of organic carbon and releases of GHGs. In the present study, we conducted a field-based warming experiment in Cambridge Bay, Canada (69°07'48″N, 105°03'36″W) by employing passive chambers during growing seasons over 6 years. A suite of enzyme activities (ß-glucosidase, cellobiohydrolase, N-acetylglucosaminidase, leucine aminopeptidase and phenol oxidase), microbial community structure (NGS), microbial abundances (gene copy numbers of bacteria and fungi), and soil chemical properties have been monitored in two depths (0-5 cm and 5-10 cm) of tundra soils, which were exposed to four different treatments (`control', `warming-only', `water-addition only', and both `warming and water-addition'). Phenol oxidase activity increased substantially, and bacterial community structure and abundance changed in the early stage (after 1 year's warming manipulation), but these changes disappeared afterwards. Most hydrolases were enhanced in surface soils by `water-addition only' over the period. However, the long-term effects of warming appeared in sub-surface soils where both `warming only' and `warming and water addition' increased hydrolase activities. Overall results of this study indicate that the warming effects on enzyme activities in surface soils are only short-term (phenol oxidase) or masked by water-limitation (hydrolases). However, hydrolases activities in sub-surface soils are more strongly enhanced than surface soils by warming, probably due to the lack of water limitation. Meanwhile, negative correlations between hydrolase activities and humic fraction of DOC appeared following the sudden increase in phenol oxidase after 1 year's manipulation, suggesting that `enzyme latch' hypothesis is partially responsible for the control of hydrolases in the ecosystem.

Comparison of Hard Surface and Soft Soil Impact Performance of a Crashworthy Composite Fuselage Concept

NASA Technical Reports Server (NTRS)

Sareen, Ashish K.; Sparks, Chad; Mullins, B. R., Jr.; Fasanella, Edwin; Jackson, Karen

2002-01-01

A comparison of the soft soil and hard surface impact performance of a crashworthy composite fuselage concept has been performed. Specifically, comparisons of the peak acceleration values, pulse duration, and onset rate at specific locations on the fuselage were evaluated. In a prior research program, the composite fuselage section was impacted at 25 feet per second onto concrete at the Impact Dynamics Research Facility (IDRF) at NASA Langley Research Center. A soft soil test was conducted at the same impact velocity as a part of the NRTC/RITA Crashworthy and Energy Absorbing Structures project. In addition to comparisons of soft soil and hard surface test results, an MSC. Dytran dynamic finite element model was developed to evaluate the test analysis correlation. In addition, modeling parameters and techniques affecting test analysis correlation are discussed. Once correlated, the analytical methodology will be used in follow-on work to evaluate the specific energy absorption of various subfloor concepts for improved crash protection during hard surface and soft soil impacts.

Relationships between soil microbial communities and soil carbon turnover along a vegetation and moisture gradient in interior Alaska

NASA Astrophysics Data System (ADS)

Waldrop, M. P.; Harden, J. W.; Turetsky, M. R.; Petersen, D. G.; McGuire, A. D.; Briones, M. J.; Churchill, A. C.; Doctor, D. H.; Pruett, L. E.

2010-12-01

Boreal landscapes are characterized by a mosaic of uplands and lowlands, which differ in plant species composition, litter biochemistry, and biogeochemical cycling rates. Boreal ecosystems, from upland black spruce stands to lowland fens, are structured largely by water table position and contain quantitatively and qualitatively different forms of soil organic matter. Differences in carbon (C) availability among ecosystems likely translate to differences in the structure of soil microbial communities, which in turn could affect rates of organic matter decomposition and turnover. We examined relationships between microbial communities and soil C turnover in near-surface soils along a topographic soil moisture and vegetation gradient in interior Alaska. We tested the hypothesis that upland black spruce sites would be dominated by soil fungi and have slow rates of C turnover, whereas lowland ecosystems would be dominated by bacteria and mesofauna (enchytraeids) and have more rapid rates of C turnover. We utilized several isotopic measures of soil C turnover including bomb radiocarbon techniques, the δ15N of SOM, and the difference between δ13C of SOM, DOC, and respired CO2. All three measures indicated greater C turnover rates in the surface soils of the lowland fen sites compared to the more upland locations. Quantitative PCR analyses of soil bacteria and archaea, combined with enchytraed counts, confirmed that surface soils from the lowland fen ecosystems had the highest abundances of these functional groups. Fungal biomass was highly variable and tended to be more abundant in the upland forest sites. Soil enzymatic results were mixed: potential cellulase activities were higher in the more upland soils even though rates of microbial activity were generally lower. Oxidative enzyme activities were higher in fens, even though these ecosystems are saturated and partly anaerobic. Overall our data support soil food web theory which argues that rapidly cycling systems are bacterial dominated with mesofaunal grazing, whereas slowly cycling systems have characteristic higher fungal:bacterial ratios.

Particle transport patterns of short-distance soil erosion by wind-driven rain, rain and wind

NASA Astrophysics Data System (ADS)

Marzen, Miriam; Iserloh, Thomas; de Lima, João L. M. P.; Ries, Johannes B.

2015-04-01

Short distance erosion of soil surface material is one of the big question marks in soil erosion studies. The exact measurement of short-distance transported soil particles, prior to the occurrence of overland flow, is a challenge to soil erosion science due to the particular requirements of the experimental setup and test procedure. To approach a quantification of amount and distance of each type of transport, we applied an especially developed multiple-gutter system installed inside the Trier Portable Wind and Rainfall Simulator (PWRS). We measured the amount and travel distance of soil particles detached and transported by raindrops (splash), wind-driven rain (splash-saltation and splash-drift) and wind (saltation). The test setup included three different erosion agents (rain/ wind-driven rain/ wind), two substrates (sandy/ loamy), three surface structures (grain roughness/ rills lengthwise/ rills transversal) and three slope angles (0°/+7°/-7°). The results present detailed transport patterns of the three erosion agents under the varying soil and surface conditions up to a distance of 1.6 m. Under the applied rain intensity and wind velocity, wind-driven rain splash generates the highest erosion. The erodibility and travel distance of the two substrates depend on the erosion agent. The total erosion is slightly higher for the slope angle -7° (downslope), but for wind-driven rain splash, the inclination is not a relevant factor. The effect of surface structures (rills) changes with traveling distance. The wind driven rain splash generates a much higher amount of erosion and a further travel distance of the particles due to the combined action of wind and rain. The wind-driven rain factor appears to be much more significant than the other factors. The study highlights the effects of different erosion agents and surface parameters on short-distance particle transport and the powerful impact of wind-driven rain on soil erosion.

Submicron structures provide preferential spots for carbon and nitrogen sequestration in soils

PubMed Central

Vogel, Cordula; Mueller, Carsten W.; Höschen, Carmen; Buegger, Franz; Heister, Katja; Schulz, Stefanie; Schloter, Michael; Kögel-Knabner, Ingrid

2014-01-01

The sequestration of carbon and nitrogen by clay-sized particles in soils is well established, and clay content or mineral surface area has been used to estimate the sequestration potential of soils. Here, via incubation of a sieved (<2 mm) topsoil with labelled litter, we find that only some of the clay-sized surfaces bind organic matter (OM). Surprisingly, <19% of the visible mineral areas show an OM attachment. OM is preferentially associated with organo-mineral clusters with rough surfaces. By combining nano-scale secondary ion mass spectrometry and isotopic tracing, we distinguish between new labelled and pre-existing OM and show that new OM is preferentially attached to already present organo-mineral clusters. These results, which provide evidence that only a limited proportion of the clay-sized surfaces contribute to OM sequestration, revolutionize our view of carbon sequestration in soils and the widely used carbon saturation estimates. PMID:24399306

Rainfall Driven Sorting of Soils and Manure in Beef Feedlot Pens, Implications for Steroid Hormone Transport

NASA Astrophysics Data System (ADS)

Bryson, R.; Harter, T.

2009-12-01

Previous research has documented elevated estrogenic and androgenic activity in surface waters receiving cattle feedlot effluent, while current research shows that significant concentrations of hydrophobic steroid hormones are transported in the solid phase of feedlot pen surface runoff. Accumulated manure in beef feedlot pens includes organic matter ranging from colloidal particles to partially digested feed, forming a complex soil-manure conglomerate at the pen surface. We hypothesized that the transport of solid phase particles in rainfall runoff on beef feedlots would be influenced but not limited by shield layer development. Soils and manure at a beef feedlot were evaluated before and after rainfall-runoff events to determine changes in soil composition and structure. Runoff samples were also collected during an hour of runoff and analyzed for suspended solids. Results indicate that rainfall actively sorts the soil and manure components through raindrop impact, depression storage and runoff. However, transport of solid phase constituents was found to be elevated throughout the hydrograph. This suggests that the surface shield layer conceptualization applied to other soils should be modified before application to the soil-manure conglomerate found in beef feedlot pens.

Assimilation of Spatially Sparse In Situ Soil Moisture Networks into a Continuous Model Domain

NASA Astrophysics Data System (ADS)

Gruber, A.; Crow, W. T.; Dorigo, W. A.

2018-02-01

Growth in the availability of near-real-time soil moisture observations from ground-based networks has spurred interest in the assimilation of these observations into land surface models via a two-dimensional data assimilation system. However, the design of such systems is currently hampered by our ignorance concerning the spatial structure of error afflicting ground and model-based soil moisture estimates. Here we apply newly developed triple collocation techniques to provide the spatial error information required to fully parameterize a two-dimensional (2-D) data assimilation system designed to assimilate spatially sparse observations acquired from existing ground-based soil moisture networks into a spatially continuous Antecedent Precipitation Index (API) model for operational agricultural drought monitoring. Over the contiguous United States (CONUS), the posterior uncertainty of surface soil moisture estimates associated with this 2-D system is compared to that obtained from the 1-D assimilation of remote sensing retrievals to assess the value of ground-based observations to constrain a surface soil moisture analysis. Results demonstrate that a fourfold increase in existing CONUS ground station density is needed for ground network observations to provide a level of skill comparable to that provided by existing satellite-based surface soil moisture retrievals.

Seismic loading due to mining: Wave amplification and vibration of structures

NASA Astrophysics Data System (ADS)

Lokmane, N.; Semblat, J.-F.; Bonnet, G.; Driad, L.; Duval, A.-M.

2003-04-01

A vibration induced by the ground motion, whatever its source is, can in certain cases damage surface structures. The scientific works allowing the analysis of this phenomenon are numerous and well established. However, they generally concern dynamic motion from real earthquakes. The goal of this work is to analyse the impact of shaking induced by mining on the structures located on the surface. The methods allowing to assess the consequences of earthquakes of strong amplitude are well established, when the methodology to estimate the consequences of moderate but frequent dynamic loadings is not well defined. The mining such as the "Houillères de Bassin du Centre et du Midi" (HBCM) involves vibrations which are regularly felt on the surface. An extracting work of coal generates shaking similar to those caused by earthquakes (standard waves and laws of propagation) but of rather low magnitude. On the other hand, their recurrent feature makes the vibrations more harmful. A three-dimensional modeling of standard structure of the site was carried out. The first results show that the fundamental frequencies of this structure are compatible with the amplification measurements carried out on site. The motion amplification in the surface soil layers is then analyzed. The modeling works are performed on the surface soil layers of Gardanne (Provence), where measurements of microtremors were performed. The analysis of H/V spectral ratio (horizontal on vertical component) indeed makes it possible to characterize the fundamental frequencies of the surface soil layers. This experiment also allows to characterize local evolution of amplification induced by the topmost soil layers. The numerical methods we consider to model seismic wave propagation and amplification in the site, is the Boundary Element Methode (BEM) The main advantage of the boundary element method is to get rid of artificial truncations of the mesh (as in Finite Element Method) in the case of infinite medium. For dynamic problems, these truncations lead to spurious wave reflections giving a numerical error in the solution. The experimental and numerical (BEM) results on surface motion amplification are then compared in terms of both amplitude and frequency range.

The Vertical Structure of Urban Soils and Their Convergence Across Cities

NASA Astrophysics Data System (ADS)

Herrmann, D.; Schifman, L. A.; Shuster, W.; Schwarz, K.

2017-12-01

The theoretical patterns for vertical soil structure (e.g., A-B-C ordering of horizons) are a basis for research methods and our understanding of ecosystem structure and function in general. A general understanding of how urban soils differ from non-urban soils vertically is needed to inform urban research methods and advance our knowledge of urban ecosystems. We performed a soil taxonomic assessment of 391 deep soil cores (up to 5-m) collected in 11 cities across the U.S. and Puerto Rico. The likely soil series in the absence of urbanization was identified for each soil core and comparison soil taxonomy data for agricultural and wildlands land uses soils of the same soil series was gathered from the NASIS database. We hypothesized that urbanization has modified the vertical arrangement of soil horizons and decreased their vertical complexity (e.g., degree of horizonation). In addition, we hypothesized that soils in each city are becoming more like each other and less like their pre-urbanization soils. Urban soils had fewer soil horizons than their non-urban references; specifically, urban soils had two fewer distinct genetic horizons in the top meter of soil. B horizons were commonly lost or reduced in extent as A horizons deepened and C horizons shallowed in urban relative to reference soils. The order of horizons was also different from reference and theoretical soil structure. Namely A-C transitions with an absence of B horizons was more common in urban than non-urban soils. If these patterns hold across more cities, our results indicate a need to revisit the conventional predictions of vertical soil structure for understanding urban ecosystems. Finally, we found that several attributes for urban soils with evidence of significant disturbance associated with urbanization were converging across cities. Similar findings have been found for surface soils; here we show the structure of urban soil convergence at greater soil depths than previously reported.

Biological soil crusts as an organizing principle in drylands: Chapter 1

USGS Publications Warehouse

Belnap, Jayne; Weber, Bettina; Büdel, Burkhard; Weber, Bettina; Buedel, Burkhard; Belnap, Jayne

2016-01-01

Biological soil crusts (biocrusts) have been present on Earth’s terrestrial surfaces for billions of years. They are a critical part of ecosystem processes in dryland regions, as they cover most of the soil surface and thus mediate almost all inputs and outputs from soils in these areas. There are many intriguing, but understudied, roles these communities may play in drylands. These include their function in nutrient capture and transformation, influence on the movement and distribution of nutrients and water within dryland soils, ability to structure vascular plant communities, role in creating biodiversity hotspots, and the possibility that they can be used as indicators of soil health. There are still many fascinating aspects of these communities that need study, and we hope that this chapter will facilitate such efforts.

Influence of biochar on the physical, chemical and retention properties of an amended sandy soil

NASA Astrophysics Data System (ADS)

Baiamonte, Giorgio; De Pasquale, Claudio; Parrino, Francesco; Crescimanno, Giuseppina

2017-04-01

Soil porosity plays an important role in soil-water retention and water availability to crops, potentially affecting both agricultural practices and environmental sustainability. The pore structure controls fluid flow and transport through the soil, as well as the relationship between the properties of individual minerals and plants. Moreover, the anthropogenic pressure on soil properties has produced numerous sites with extensive desertification process close to residential areas. Biochar (biologically derived charcoal) is produced by pyrolysis of biomasses under low oxygen conditions, and it can be applied for recycling organic waste in soils and increase soil fertility, improving soil structure and enhancing soil water storage and soil water movement. Soil application of biochar might have agricultural, environmental and sustainability advantages over the use of organic manures or compost, as it is a porous material with a high inner surface area. The main objectives of the present study were to investigate the possible application of biochar from forest residues, derived from mechanically chipped trunks and large branches of Abies alba M., Larix decidua Mill., Picea excelsa L., Pinus nigra A. and Pinus sylvestris L. pyrolysed at 450 °C for 48h, to improve soil structural and hydraulic properties (achieving a stabilization of soil). Different amount of biochar were added to a desertic sandy soil, and the effect on soil porosity water retention and water available to crops were investigated. The High Energy Moisture Characteristic (HEMC) technique was applied to investigate soil-water retention at high-pressure head levels. The adsorption and desorption isotherms of N2 on external surfaces were also determined in order to investigate micro and macro porosity ratio. Both the described model of studies on adsorption-desorption experiments with the applied isotherms model explain the increasing substrate porosity with a particular attention to the macro and micro porosity, respectively.

[Spatial variation characteristics of surface soil water content, bulk density and saturated hydraulic conductivity on Karst slopes].

PubMed

Zhang, Chuan; Chen, Hong-Song; Zhang, Wei; Nie, Yun-Peng; Ye, Ying-Ying; Wang, Ke-Lin

2014-06-01

Surface soil water-physical properties play a decisive role in the dynamics of deep soil water. Knowledge of their spatial variation is helpful in understanding the processes of rainfall infiltration and runoff generation, which will contribute to the reasonable utilization of soil water resources in mountainous areas. Based on a grid sampling scheme (10 m x 10 m) and geostatistical methods, this paper aimed to study the spatial variability of surface (0-10 cm) soil water content, soil bulk density and saturated hydraulic conductivity on a typical shrub slope (90 m x 120 m, projected length) in Karst area of northwest Guangxi, southwest China. The results showed that the surface soil water content, bulk density and saturated hydraulic conductivity had different spatial dependence and spatial structure. Sample variogram of the soil water content was fitted well by Gaussian models with the nugget effect, while soil bulk density and saturated hydraulic conductivity were fitted well by exponential models with the nugget effect. Variability of soil water content showed strong spatial dependence, while the soil bulk density and saturated hydraulic conductivity showed moderate spatial dependence. The spatial ranges of the soil water content and saturated hydraulic conductivity were small, while that of the soil bulk density was much bigger. In general, the soil water content increased with the increase of altitude while it was opposite for the soil bulk densi- ty. However, the soil saturated hydraulic conductivity had a random distribution of large amounts of small patches, showing high spatial heterogeneity. Soil water content negatively (P < 0.01) correlated with the bulk density and saturated hydraulic conductivity, while there was no significant correlation between the soil bulk density and saturated hydraulic conductivity.

Minute tubular forms in soil

NASA Technical Reports Server (NTRS)

Casida, L. E., Jr.; Liu, K.-C.

1979-01-01

Large numbers of long, straight, flattened structures were observed during an electron-microscope study of bacteriophage in aqueous extracts. These structures were called tubules and ranged in width from 10 to 50 nm. Materials and methods were discussed relative to extraction of tubules from soil, electron microscopy, quantitation of tubules in filtrate suspension, tests performed on tubules, plaque formation, and nutrient amendments. It is found that all of the tubules recovered from soil are broken at one or both ends. They are present in surface soils but not in a subsurface sample. Their numbers decrease during bacterial multiplication in soil or broth-containing soil. The tubules appear to be composed of protein that could be disintegrated to liberate nonprotein fibers. A possible clue to the nature of the tubules is their apparent relation to soil bacteria.

76 FR 70105 - National Oil and Hazardous Substance Pollution Contingency Plan National Priorities List: Partial...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-11-10

... property PINs listed above. The deletion of these two parcels from the Site affects all surface soils, subsurface soils, structures and groundwater within the boundaries of these parcels. In 2005, the ETA...

Phytoremediation in the tropics--influence of heavy crude oil on root morphological characteristics of graminoids.

PubMed

Merkl, Nicole; Schultze-Kraft, Rainer; Infante, Carmen

2005-11-01

When studying species for phytoremediation of petroleum-contaminated soils, one of the main traits is the root zone where enhanced petroleum degradation takes place. Root morphological characteristics of three tropical graminoids were studied. Specific root length (SRL), surface area, volume and average root diameter (ARD) of plants grown in crude oil-contaminated and uncontaminated soil were compared. Brachiaria brizantha and Cyperus aggregatus showed coarser roots in polluted soil compared to the control as expressed in an increased ARD. B. brizantha had a significantly larger specific root surface area in contaminated soil. Additionally, a shift of SRL and surface area per diameter class towards higher diameters was found. Oil contamination also caused a significantly smaller SRL and surface area in the finest diameter class of C. aggregatus. The root structure of Eleusine indica was not significantly affected by crude oil. Higher specific root surface area was related to higher degradation of petroleum hydrocarbons found in previous studies.

Plot-scale soil loss estimation with laser scanning and photogrammetry methods

NASA Astrophysics Data System (ADS)

Szabó, Boglárka; Szabó, Judit; Jakab, Gergely; Centeri, Csaba; Szalai, Zoltán; Somogyi, Árpád; Barsi, Árpád

2017-04-01

Structure from Motion (SfM) is an automatic feature-matching algorithm, which nowadays is widely used tool in photogrammetry for geoscience applications. SfM method and parallel terrestrial laser scanning measurements are widespread and they can be well accomplished for quantitative soil erosion measurements as well. Therefore, our main scope was soil erosion characterization quantitatively and qualitatively, 3D visualization and morphological characterization of soil-erosion-dynamics. During the rainfall simulation, the surface had been measured and compared before and after the rainfall event by photogrammetry (SfM - Structure from Motion) and laser scanning (TLS - Terrestrial Laser Scanning) methods. The validation of the given results had been done by the caught runoff and the measured soil-loss value. During the laboratory experiment, the applied rainfall had 40 mm/h rainfall intensity. The size of the plot was 0.5 m2. The laser scanning had been implemented with Faro Focus 3D 120 S type equipment, while the SfM shooting had been carried out by 2 piece SJCAM SJ4000+ type, 12 MP resolution and 4K action cams. The photo-reconstruction had been made with Agisoft Photoscan software, while evaluation of the resulted point-cloud from laser scanning and photogrammetry had been implemented partly in CloudCompare and partly in ArcGIS. The resulted models and the calculated surface changes didn't prove to be suitable for estimating soil-loss, only for the detection of changes in the vertical surface. The laser scanning resulted a quite precise surface model, while the SfM method is affected by errors at the surface model due to other factors. The method needs more adequate technical laboratory preparation.

Soil microbial structure and function post-volcanic eruption on Kasatochi Island and regional controls on microbial heterogeneity

NASA Astrophysics Data System (ADS)

Zeglin, L. H.; Rainey, F.; Wang, B.; Waythomas, C.; Talbot, S. L.

2013-12-01

Microorganisms are abundant and diverse in soil and their integrated activity drives nutrient cycling on the ecosystem scale. Organic matter (OM) inputs from plant production support microbial heterotrophic life, and soil geochemistry constrains microbial activity and diversity. As vegetation and soil develops over time, these factors change, modifying the controls on microbial heterogeneity. Following a volcanic eruption, ash deposition creates new surfaces where both organismal growth and weathering processes are effectively reset. The trajectory of microbial community development following this disturbance depends on both organic matter accumulation and geochemical constraints. Also, dispersal of microbial cells to the sterile ash surface may determine microbial community succession. The Aleutian Islands (Alaska, USA) are a dynamic volcanic region, with active and dormant volcanoes distributed across the volcanic arc. One of these volcanoes, Kasatochi, erupted violently in August 2008, burying a small lush island in pryoclastic flows and fine ash. Since, plants and birds are beginning to re-establish on developing surfaces, including legacy soils exposed by rapid erosion of pyroclastic deposits, suggesting that recovery of microbial life is also proceeding. However, soil microbial diversity and function has not been examined on Kasatochi Island or across the greater Aleutian region. The project goal is to address these questions: How is soil microbial community structure and function developing following the Kasatochi eruption? What is the relative importance of dispersal, soil OM and geochemistry to microbial community heterogeneity across the Aleutians? Surface mineral soil (20-cm depth) samples were collected from Kasatochi Island in summer 2013, five years after the 2008 eruption, and from eight additional Aleutian islands. On Kasatochi, pryoclastic deposits, exposed legacy soils supporting regrowth of remnant dune wild-rye (Leymus mollis) and mesic meadow plant communities, and soils impacted by recovering seabird rookeries were sampled. On the other islands, soils supporting both Leymus and mesic meadow communities (representative of dominant vegetation types on Kasatochi pre-eruption) were sampled. For each soil category and island combination, three transects of soil cores at 10-cm, 50-cm, 1-m, 5-m and 10-m distance were collected; with distances between sites and islands included (up to >700 km), the range of geographic distance examined covers over 7 orders of magnitude. For all samples, data on fundamental geochemical and OM factors, bacterial and fungal biomass, activity and diversity (via QPCR, extracellular enzyme potential assays and T-RFLP) are being collected. Covariance analysis is being used to evaluate the scale of maximum spatial heterogeneity in microbial structure and function, and ordination and matrix correlation analyses are being used to identify the key environmental covariates with heterogeneity. We hypothesize that heterogeneity at small (cm) scales will reflect predominant geochemical controls, at medium (m) scales will reflect predominant OM (vegetation) controls and at large (km) scales will reflect dispersal-related controls on microbial community structure and function.

Below the disappearing marshes of an urban estuary: historic nitrogen trends and soil structure

USGS Publications Warehouse

Wigand, Cathleen; Roman, Charles T.; Davey, Earl; Stolt, Mark; Johnson, Roxanne; Hanson, Alana; Watson, Elizabeth B.; Moran, S. Bradley; Cahoon, Donald R.; Lynch, James C.; Rafferty, Patricia

2014-01-01

Marshes in the urban Jamaica Bay Estuary, New York, USA are disappearing at an average rate of 13 ha/yr, and multiple stressors (e.g., wastewater inputs, dredging activities, groundwater removal, and global warming) may be contributing to marsh losses. Among these stressors, wastewater nutrients are suspected to be an important contributing cause of marsh deterioration. We used census data, radiometric dating, stable nitrogen isotopes, and soil surveys to examine the temporal relationships between human population growth and soil nitrogen; and we evaluated soil structure with computer-aided tomography, surface elevation and sediment accretion trends, carbon dioxide emissions, and soil shear strength to examine differences among disappearing (Black Bank and Big Egg) and stable marshes (JoCo). Radiometric dating and nitrogen isotope analyses suggested a rapid increase in human wastewater nutrients beginning in the late 1840s, and a tapering off beginning in the 1930s when wastewater treatment plants (WWTPs) were first installed. Current WWTPs nutrient loads to Jamaica Bay are approximately 13 995 kg N/d and 2767 kg P/d. At Black Bank, the biomass and abundance of roots and rhizomes and percentage of organic matter on soil were significantly lower, rhizomes larger in diameter, carbon dioxide emission rates and peat particle density significantly greater, and soil strength significantly lower compared to the stable JoCo Marsh, suggesting Black Bank has elevated decomposition rates, more decomposed peat, and highly waterlogged peat. Despite these differences, the rates of accretion and surface elevation change were similar for both marshes, and the rates of elevation change approximated the long term relative rate of sea level rise estimated from tide gauge data at nearby Sandy Hook, New Jersey. We hypothesize that Black Bank marsh kept pace with sea level rise by the accretion of material on the marsh surface, and the maintenance of soil volume through production of larger diameter rhizomes and swelling (dilation) of waterlogged peat. JoCo Marsh kept pace with sea-level rise through surface accretion and soil organic matter accumulation. Understanding the effects of multiple stressors, including nutrient enrichment, on soil structure, organic matter accumulation, and elevation change will better inform management decisions aimed at maintaining and restoring coastal marshes.

Below the disappearing marshes of an urban estuary: historic nitrogen trends and soil structure.

PubMed

Wigand, Cathleen; Roman, Charles T; Davey, Earl; Stolt, Mark; Johnson, Roxanne; Hanson, Alana; Watson, Elizabeth B; Moran, S Bradley; Cahoon, Donald R; Lynch, James C; Rafferty, Patricia

2014-06-01

Marshes in the urban Jamaica Bay Estuary, New York, USA are disappearing at an average rate of 13 ha/yr, and multiple stressors (e.g., wastewater inputs, dredging activities, groundwater removal, and global warming) may be contributing to marsh losses. Among these stressors, wastewater nutrients are suspected to be an important contributing cause of marsh deterioration. We used census data, radiometric dating, stable nitrogen isotopes, and soil surveys to examine the temporal relationships between human population growth and soil nitrogen; and we evaluated soil structure with computer-aided tomography, surface elevation and sediment accretion trends, carbon dioxide emissions, and soil shear strength to examine differences among disappearing (Black Bank and Big Egg) and stable marshes (JoCo). Radiometric dating and nitrogen isotope analyses suggested a rapid increase in human wastewater nutrients beginning in the late 1840s, and a tapering off beginning in the 1930s when wastewater treatment plants (WWTPs) were first installed. Current WWTPs nutrient loads to Jamaica Bay are approximately 13 995 kg N/d and 2767 kg P/d. At Black Bank, the biomass and abundance of roots and rhizomes and percentage of organic matter on soil were significantly lower, rhizomes larger in diameter, carbon dioxide emission rates and peat particle density significantly greater, and soil strength significantly lower compared to the stable JoCo Marsh, suggesting Black Bank has elevated decomposition rates, more decomposed peat, and highly waterlogged peat. Despite these differences, the rates of accretion and surface elevation change were similar for both marshes, and the rates of elevation change approximated the long-term relative rate of sea level rise estimated from tide gauge data at nearby Sandy Hook, New Jersey. We hypothesize that Black Bank marsh kept pace with sea level rise by the accretion of material on the marsh surface, and the maintenance of soil volume through production of larger diameter rhizomes and swelling (dilation) of waterlogged peat. JoCo Marsh kept pace with sea-level rise through surface accretion and soil organic matter accumulation. Understanding the effects of multiple stressors, including nutrient enrichment, on soil structure, organic matter accumulation, and elevation change will better inform management decisions aimed at maintaining and restoring coastal marshes.

Properties of Forested Loess Soils After Repeated Prescribed Burns

Treesearch

D.M. Moehring; C.X. Grano; J.R. Bassett

1966-01-01

Nine annual burns have had little effect on the nutrient content and structure of the surface 4 inches of loess soils on flat terrain.Because prescribed burns must often be repeated to obtain desired results, many foresters are apprehensive about the possible deleterious effects on soils. In 1954 the Timber Management Laboratory at Crossett, Arkansas, in co-...

The surface-pore integrated effect of soil organic matter on retention and transport of pharmaceuticals and personal care products in soils.

PubMed

Qin, Qin; Chen, Xijuan; Zhuang, Jie

2017-12-01

This study examines a surface-pore integrated mechanism that allows soil organic matter (SOM) to influence the retention and transport of three representative pharmaceuticals and personal care products (PPCPs)-ibuprofen, carbamazepine, and bisphenol A-in agricultural soil. A series of sorption-desorption batch tests and breakthrough column experiments were conducted using manured and non-manured soils. Results show that SOM could substantially influence the environmental behaviors of PPCPs via two mechanisms: surface-coating and pore-filling. Surface-coating with molecular SOM decreases the sorption of dissociated PPCPs (e.g., ibuprofen) but increases the sorption of non-dissociated PPCPs (e.g., carbamazepine and bisphenol A), while pore-filling with colloidal SOM enhances the retention of all the PPCPs by providing nano-/micro-pores that limit diffusion. The higher retention and lower mobility of PPCPs in soil microaggregates than in bulk soils suggest that SOM content and SOM-altered soil pore structure could exert a coupled effect on PPCP retention. Differences in the elution of PPCPs with low surface tension solution (i.e., 20% ethanol) in the presence and absence of SOM indicate that PPCPs prefer to remain in SOM-filled pores. Overall, ibuprofen has a high environmental risk, whereas carbamazepine and bisphenol A could be readily retarded in agricultural soils (with a loamy clay texture). This study implies that SOM accrual (particularly pore-filling SOM) has a high potential for reducing the off-site risks of PPCPs by increasing soil nano-/micro-porosity. Copyright © 2017 Elsevier B.V. All rights reserved.

Novel manure management technologies in no-till and forage introduction to the special series.

PubMed

Maguire, Rory O; Kleinman, Peter J A; Beegle, Douglas B

2011-01-01

Surface application of manures leaves nitrogen (N) and phosphorus (P) susceptible to being lost in runoff, and N can also be lost to the atmosphere through ammonia (IH3) volatilization. Tillage immediately after surface application of manure moves manure nutrients under the soil surface, where they are less vulnerable to runoff and volatilization loss. Tillage, however, destroys soil structure, can lead to soil erosion, and is incompatible with forage and no-till systems. A variety of technologies are now available to place manure nutrients under the soil surface, but these are not widely used as surface broadcasting is cheap and long established as the standard method for land application of manure. This collection of papers includes agronomic, environmental, and economic assessments of subsurface manure application technologies, many of which clearly show benefits when comparedwith surface broadcasting. However, there remain significant gaps in our current knowledge, some related to the site-specific nature of technological performance, others related to the nascent and incomplete nature of the assessment process. Thus, while we know that we can improve land application of manure and the sustainability of farming systems with alternatives to surface broadcasting, many questions remain concerning which technologies work best for particular soils, manure types, and farming and cropping systems.

Bacterial community structure and soil properties of a subarctic tundra soil in Council, Alaska.

PubMed

Kim, Hye Min; Jung, Ji Young; Yergeau, Etienne; Hwang, Chung Yeon; Hinzman, Larry; Nam, Sungjin; Hong, Soon Gyu; Kim, Ok-Sun; Chun, Jongsik; Lee, Yoo Kyung

2014-08-01

The subarctic region is highly responsive and vulnerable to climate change. Understanding the structure of subarctic soil microbial communities is essential for predicting the response of the subarctic soil environment to climate change. To determine the composition of the bacterial community and its relationship with soil properties, we investigated the bacterial community structure and properties of surface soil from the moist acidic tussock tundra in Council, Alaska. We collected 70 soil samples with 25-m intervals between sampling points from 0-10 cm to 10-20 cm depths. The bacterial community was analyzed by pyrosequencing of 16S rRNA genes, and the following soil properties were analyzed: soil moisture content (MC), pH, total carbon (TC), total nitrogen (TN), and inorganic nitrogen (NH4+ and NO3-). The community compositions of the two different depths showed that Alphaproteobacteria decreased with soil depth. Among the soil properties measured, soil pH was the most significant factor correlating with bacterial community in both upper and lower-layer soils. Bacterial community similarity based on jackknifed unweighted unifrac distance showed greater similarity across horizontal layers than through the vertical depth. This study showed that soil depth and pH were the most important soil properties determining bacterial community structure of the subarctic tundra soil in Council, Alaska. © 2014 The Authors. FEMS Microbiology Ecology published by John Wiley & Sons Ltd on behalf of the Federation of European Microbiological Societies.

Microwave emission measurements of sea surface roughness, soil moisture, and sea ice structure

NASA Technical Reports Server (NTRS)

Gloersen, P.; Wilheit, T. T.; Schmugge, T. J.

1972-01-01

In order to demonstrate the feasibility of the microwave radiometers to be carried aboard the Nimbus 5 and 6 satellites and proposed for one of the earth observatory satellites, remote measurements of microwave radiation at wavelengths ranging from 0.8 to 21 cm have been made of a variety of the earth's surfaces from the NASA CV-990 A/C. Brightness temperatures of sea water surfaces of varying roughness, of terrain with varying soil moisture, and of sea ice of varying structure were observed. In each case, around truth information was available for correlation with the microwave brightness temperature. The utility of passive microwave radiometry in determining ocean surface wind speeds, at least for values higher than 7 meters/second has been demonstrated. In addition, it was shown that radiometric signatures can be used to determine soil moisture in unvegetated terrain to within five percentage points by weight. Finally, it was demonstrated that first year thick, multi-year, and first year thin sea ice can be distinguished by observing their differing microwave emissivities at various wavelengths.

Method and apparatus for optimized sampling of volatilizable target substances

DOEpatents

Lindgren, Eric R.; Phelan, James M.

2002-01-01

An apparatus for capturing, from gases such as soil gas, target analytes. Target analytes may include emanations from explosive materials or from residues of explosive materials. The apparatus employs principles of sorption common to solid phase microextraction, and is best used in conjunction with analysis means such as a gas chromatograph. To sorb target analytes, the apparatus functions using various sorptive structures to capture target analyte. Depending upon the embodiment, those structures may include 1) a conventional solid-phase microextraction (SPME) fiber, 2) a SPME fiber suspended in a capillary tube (with means provided for moving gases through the capillary tube so that the gases come into close proximity to the suspended fiber), and 3) a capillary tube including an interior surface on which sorptive material (similar to that on the surface of a SPME fiber) is supported (along with means for moving gases through the capillary tube so that the gases come into close proximity to the sorptive material). In one disclosed embodiment, at least one such sorptive structure is associated with an enclosure including an opening in communication with the surface of a soil region potentially contaminated with buried explosive material such as unexploded ordnance. Emanations from explosive materials can pass into and accumulate in the enclosure where they are sorbed by the sorptive structures. Also disclosed is the use of heating means such as microwave horns to drive target analytes into the soil gas from solid and liquid phase components of the soil.

Differential distribution patterns of ammonia-oxidizing archaea and bacteria in acidic soils of Nanling National Nature Reserve forests in subtropical China.

PubMed

Gan, Xian-Hua; Zhang, Fang-Qiu; Gu, Ji-Dong; Guo, Yue-Dong; Li, Zhao-Qing; Zhang, Wei-Qiang; Xu, Xiu-Yu; Zhou, Yi; Wen, Xiao-Ying; Xie, Guo-Guang; Wang, Yong-Feng

2016-02-01

In addition to ammonia-oxidizing bacteria (AOB) the more recently discovered ammonia-oxidizing archaea (AOA) can also oxidize ammonia, but little is known about AOA community structure and abundance in subtropical forest soils. In this study, both AOA and AOB were investigated with molecular techniques in eight types of forests at surface soils (0-2 cm) and deep layers (18-20 cm) in Nanling National Nature Reserve in subtropical China. The results showed that the forest soils, all acidic (pH 4.24-5.10), harbored a wide range of AOA phylotypes, including the genera Nitrosotalea, Nitrososphaera, and another 6 clusters, one of which was reported for the first time. For AOB, only members of Nitrosospira were retrieved. Moreover, the abundance of the ammonia monooxygenase gene (amoA) from AOA dominated over AOB in most soil samples (13/16). Soil depth, rather than forest type, was an important factor shaping the community structure of AOA and AOB. The distribution patterns of AOA and AOB in soil layers were reversed: AOA diversity and abundances in the deep layers were higher than those in the surface layers; on the contrary, AOB diversity and abundances in the deep layers were lower than those in the surface layers. Interestingly, the diversity of AOA was positively correlated with pH, but negatively correlated with organic carbon, total nitrogen and total phosphorus, and the abundance of AOA was negatively correlated with available phosphorus. Our results demonstrated that AOA and AOB were differentially distributed in acidic soils in subtropical forests and affected differently by soil characteristics.

[Influence of different types of surface on the diversity of soil fauna in Beijing Olympic Park].

PubMed

Song, Ying-shi; Li, Xiao-wen; Li, Feng; Li, Hai-mei

2015-04-01

Soil fauna are impacted by urbanization. In order to explore the stress of different surface covers on diversity and community structure of soil fauna, we conducted this experiment in Beijing Olympic Park. In autumn of 2013, we used Baermann and Tullgren methods to study the diversity of soil fauna in the depth of 0-5 cm, 5-10 cm, 10-15 cm under four different land covers i.e. bared field (BF), totally impervious surface (TIS), partly impervious surface (PIS) and grassland (GL). The results showed that the total number of soil fauna in 100 cm3 was in order of GL (210) > PIS (193) > TIS (183) > BF (90), and the number of nematodes accounted for 72.0%-92.8% of the total number. On the vertical level, except for the TIS, the other three types of surface soil fauna had the surface gathered phenomenon. The Shannon diversity index and the Pielou evenness index of BF were lower, but the Simpson dominance index was higher than in the other land covers. The Shannon index and Margalef richness indes of GL were higher than those of the other land covers. The Shannon indexes of TIS and PIS were between the BF and GL. Except for the TIS and GL, the similarity indexes were between 0.4-0.5, indicating moderate non-similar characteristics. The diversity of soil fauna was significantly correlated with temperature, pH and available potassium.

Stream Flow Prediction by Remote Sensing and Genetic Programming

NASA Technical Reports Server (NTRS)

Chang, Ni-Bin

2009-01-01

A genetic programming (GP)-based, nonlinear modeling structure relates soil moisture with synthetic-aperture-radar (SAR) images to present representative soil moisture estimates at the watershed scale. Surface soil moisture measurement is difficult to obtain over a large area due to a variety of soil permeability values and soil textures. Point measurements can be used on a small-scale area, but it is impossible to acquire such information effectively in large-scale watersheds. This model exhibits the capacity to assimilate SAR images and relevant geoenvironmental parameters to measure soil moisture.

MSL DAN Science Investigation: Physical Simulation of DAN

NASA Technical Reports Server (NTRS)

Jun, Insoo

2012-01-01

The main objective of the proposed investigation is to study the characteristics (i.e., hydrogen content, soil composition, layer-structure, etc.) of sub-surface and the surface radiation (neutron in particular) environment.

Soil erosion under multiple time-varying rainfall events

NASA Astrophysics Data System (ADS)

Heng, B. C. Peter; Barry, D. Andrew; Jomaa, Seifeddine; Sander, Graham C.

2010-05-01

Soil erosion is a function of many factors and process interactions. An erosion event produces changes in surface soil properties such as texture and hydraulic conductivity. These changes in turn alter the erosion response to subsequent events. Laboratory-scale soil erosion studies have typically focused on single independent rainfall events with constant rainfall intensities. This study investigates the effect of multiple time-varying rainfall events on soil erosion using the EPFL erosion flume. The rainfall simulator comprises ten Veejet nozzles mounted on oscillating bars 3 m above a 6 m × 2 m flume. Spray from the nozzles is applied onto the soil surface in sweeps; rainfall intensity is thus controlled by varying the sweeping frequency. Freshly-prepared soil with a uniform slope was subjected to five rainfall events at daily intervals. In each 3-h event, rainfall intensity was ramped up linearly to a maximum of 60 mm/h and then stepped down to zero. Runoff samples were collected and analysed for particle size distribution (PSD) as well as total sediment concentration. We investigate whether there is a hysteretic relationship between sediment concentration and discharge within each event and how this relationship changes from event to event. Trends in the PSD of the eroded sediment are discussed and correlated with changes in sediment concentration. Close-up imagery of the soil surface following each event highlight changes in surface soil structure with time. This study enhances our understanding of erosion processes in the field, with corresponding implications for soil erosion modelling.

Design of a scientific probe for obtaining Mars surface material

NASA Technical Reports Server (NTRS)

Baker, Miles; Deyerl, Eric; Gibson, Tim; Langberg, Bob; Yee, Terrance (Editor)

1990-01-01

The objective is to return a 1 Kg Martian soil sample from the surface of Mars to a mothership in a 60 km Mars orbit. Given here is information on the mission profile, the structural design and component placement, thermal control and guidance, propulsion systems, orbital mechanics, and specialized structures.

Significance of wall structure, macromolecular composition, and surface polymers to the survival and transport of Cryptosporidium parvum Oocysts

USDA-ARS?s Scientific Manuscript database

The structure and composition of the oocyst wall are primary factors determining the survival of Cryptosporidium parvum oocysts outside the host. An external polymer matrix (glycocalyx) may mediate interactions with environmental surfaces and, thus, affect the transport of oocysts in water, soil, an...

Quantification and mapping of surface residue cover and tillage practices for maize and soybean fields in south central Nebraska-USA using Landsat imagery

USDA-ARS?s Scientific Manuscript database

The area cultivated under conservation tillage practices such as no-till and minimal tillage has recently increased in south central Nebraska (NE). Consequently, changes in some of the impacts of cropping systems on soil such as enhancing soil and water quality, improving soil structures and infiltr...

Ground-Water Levels and Soil Characteristics in a Forested Typic Glossaqualf

Treesearch

Peter L. Lorio

1977-01-01

The presence of impermeable layers can affect the development of a soil and its water regime. In a forested Typic Glossaqualf in southwest Louisiana, moisture, density, and piezometer measurements revealed an impermeable layer of soil between about 1.8 and 2.8 m below the surface. A high proportion of very fine sand and development of platy structure appeared related...

Wettability, soil organic matter and structure-properties of typical chernozems under the forest and under the arable land

NASA Astrophysics Data System (ADS)

Bykova, Galina; Umarova, Aminat; Tyugai, Zemfira; Milanovskiy, Evgeny; Shein, Evgeny

2017-04-01

Intensive tillage affects the properties of soil: decrease in content of soil organic matter and in hydrophobicity of the soil's solid phase, the reduction of amount of water stable aggregates - all this leads to deterioration of the structure of the soil and affects the process of movement of moisture in the soil profile. One of the hypotheses of soil's structure formation ascribes the formation of water stable aggregates with the presence of hydrophobic organic substances on the surface of the soil's solid phase. The aim of this work is to study the effect of tillage on properties of typical chernozems (pachic Voronic Chernozems, Haplic Chernozems) (Russia, Kursk region), located under the forest and under the arable land. The determination of soil-water contact angle was performed by a Drop Shape Analyzer DSA100 (Krüss GmbH, Germany) by the static sessile drop method. For all samples the content of total and organic carbon by dry combustion in oxygen flow and the particle size distribution by the laser diffraction method on the device Analysette 22 comfort, FRITCH, Germany were determined. The estimation of aggregate composition was performed by dry sieving (AS 200, Retsch, Germany), the content of water stable aggregates was estimated by the Savvinov method. There was a positive correlation between the content of organic matter and soil's wettability in studied soils, a growth of contact angle with the increasing the content of organic matter. Under the forest the content of soil organic matter was changed from 6,41% on the surface up to 1,9% at the depth of 100 cm. In the Chernozem under the arable land the organic carbon content in arable horizon is almost two times less. The maximum of hydrophobicity (78.1o) was observed at the depth of 5 cm under the forest. In the profile under the arable land the contact angle value at the same depth was 50o. The results of the structure analysis has shown a decrease in the content of agronomically valuable and water stable aggregates in the profile under arable land. These data indicate the correlation between the wettability of soils with the content of organic matter and their influence on the formation of water stable structure, as well as the negative impact of tillage on the analyzed characteristics.

Influence of selected physicochemical parameters on microbiological activity of mucks.

NASA Astrophysics Data System (ADS)

Całka, A.; Sokołowska, Z.; Warchulska, P.; Dąbek-Szreniawska, M.

2009-04-01

One of the basic factor decided about soil fertility are microorganisms that together with flora, determine trend and character of biochemical processes as well totality of fundamental transformations connected with biogeochemistry and physicochemical properties of soil. Determination of general bacteria number, quantity of selected groups of microorganisms and investigation of respiration intensity let estimate microbiological activity of soil. Intensity of microbiological processes is directly connected with physicochemical soil parameters. In that case, such structural parameters as bulk density, porosity, surface or carbon content play significant role. Microbiological activity also changes within the bounds of mucks with different stage of humification and secondary transformation. Knowledge of relations between structural properties, microorganism activity and degree of transformation and humification can lead to better understanding microbiological processes as well enable to estimate microbiological activity at given physicochemical conditions and at progressing process of soil transformation. The study was carried out on two peaty-moorsh (muck) soils at different state of secondary transformation and humification degree. Soil samples were collected from Polesie Lubelskie (layer depth: 5 - 25 cm). Investigated mucks originated from soils formed from low peatbogs. Soil sample marked as I belonged to muck group weakly secondary transformed. Second sample (II) represented soil group with middle stage of secondary transformation. The main purpose of the research was to examine the relations between some physicochemical and surface properties and their biological activity. Total number and respiration activity of microorganisms were determined. The effectiveness of utilizing the carbon substances from the soil by the bacteria increased simultaneously with the transformation state of the peat-muck soils. Quantity of organic carbon decreased distinctly in the soil at the higher stage of secondary transformation and it influenced quantity and activity of soil microorganisms. Bulk density and surface increased with increasing secondary transformation degree. On the other hand, porosity decreased with increasing secondary transformation index. Process of secondary transformation influenced the soil environment for the microbes by changing the physicochemical properties. This way it influenced the number of microorganisms and caused changes of biological activity in the soils.

Application of atomic force microscopy to the study of natural and model soil particles.

PubMed

Cheng, S; Bryant, R; Doerr, S H; Rhodri Williams, P; Wright, C J

2008-09-01

The structure and surface chemistry of soil particles has extensive impact on many bulk scale properties and processes of soil systems and consequently the environments that they support. There are a number of physiochemical mechanisms that operate at the nanoscale which affect the soil's capability to maintain native vegetation and crops; this includes soil hydrophobicity and the soil's capacity to hold water and nutrients. The present study used atomic force microscopy in a novel approach to provide unique insight into the nanoscale properties of natural soil particles that control the physiochemical interaction of material within the soil column. There have been few atomic force microscopy studies of soil, perhaps a reflection of the heterogeneous nature of the system. The present study adopted an imaging and force measurement research strategy that accounted for the heterogeneity and used model systems to aid interpretation. The surface roughness of natural soil particles increased with depth in the soil column a consequence of the attachment of organic material within the crevices of the soil particles. The roughness root mean square calculated from ten 25 microm(2) images for five different soil particles from a Netherlands soil was 53.0 nm, 68.0 nm, 92.2 nm and 106.4 nm for the respective soil depths of 0-10 cm, 10-20 cm, 20-30 cm and 30-40 cm. A novel analysis method of atomic force microscopy phase images based on phase angle distribution across a surface was used to interpret the nanoscale distribution of organic material attached to natural and model soil particles. Phase angle distributions obtained from phase images of model surfaces were found to be bimodal, indicating multiple layers of material, which changed with the concentration of adsorbed humic acid. Phase angle distributions obtained from phase images of natural soil particles indicated a trend of decreasing surface coverage with increasing depth in the soil column. This was consistent with previous macroscopic determination of the proportions of organic material chemically extracted from bulk samples of the soils from which specimen particles were drawn. Interaction forces were measured between atomic force microscopy cantilever tips (Si(3)N(4)) and natural soil and model surfaces. Adhesion forces at humic acid free specimen surfaces (Av. 20.0 nN), which are primarily hydrophilic and whose interactions are subject to a significant contribution from the capillary forces, were found to be larger than those of specimen surfaces with adsorbed humic acid (Av. 6.5 nN). This suggests that adsorbed humic acid increased surface hydrophobicity. The magnitude and distribution of adhesion forces between atomic force microscopy tips and the natural particle surfaces was affected by both local surface roughness and the presence of adsorbed organic material. The present study has correlated nanoscale measurements with established macroscale methods of soil study. Thus, the research demonstrates that atomic force microscopy is an important addition to soil science that permits a multiscale analysis of the multifactorial phenomena of soil hydrophobicity and wetting.

Cross-Site Soil Microbial Communities under Tillage Regimes: Fungistasis and Microbial Biomarkers

PubMed Central

Yrjälä, Kim; Alakukku, Laura; Palojärvi, Ansa

2012-01-01

The exploitation of soil ecosystem services by agricultural management strategies requires knowledge of microbial communities in different management regimes. Crop cover by no-till management protects the soil surface, reducing the risk of erosion and nutrient leaching, but might increase straw residue-borne and soilborne plant-pathogenic fungi. A cross-site study of soil microbial communities and Fusarium fungistasis was conducted on six long-term agricultural fields with no-till and moldboard-plowed treatments. Microbial communities were studied at the topsoil surface (0 to 5 cm) and bottom (10 to 20 cm) by general bacterial and actinobacterial terminal restriction fragment length polymorphism (T-RFLP) and phospholipid fatty acid (PLFA) analyses. Fusarium culmorum soil fungistasis describing soil receptivity to plant-pathogenic fungi was explored by using the surface layer method. Soil depth had a significant impact on general bacterial as well as actinobacterial communities and PLFA profiles in no-till treatment, with a clear spatial distinction of communities (P < 0.05), whereas the depth-related separation of microbial communities was not observed in plowed fields. The fungal biomass was higher in no-till surface soil than in plowed soil (P < 0.07). Soil total microbial biomass and fungal biomass correlated with fungistasis (P < 0.02 for the sum of PLFAs; P < 0.001 for PLFA 18:2ω6). Our cross-site study demonstrated that agricultural management strategies can have a major impact on soil microbial community structures, indicating that it is possible to influence the soil processes with management decisions. The interactions between plant-pathogenic fungi and soil microbial communities are multifaceted, and a high level of fungistasis could be linked to the high microbial biomass in soil but not to the specific management strategy. PMID:22983972

A multi-scale ''soil water structure'' model based on the pedostructure concept

NASA Astrophysics Data System (ADS)

Braudeau, E.; Mohtar, R. H.; El Ghezal, N.; Crayol, M.; Salahat, M.; Martin, P.

2009-02-01

Current soil water models do not take into account the internal organization of the soil medium and, a fortiori, the physical interaction between the water film surrounding the solid particles of the soil structure, and the surface charges of this structure. In that sense they empirically deal with the physical soil properties that are all generated from this soil water-structure interaction. As a result, the thermodynamic state of the soil water medium, which constitutes the local physical conditions, namely the pedo-climate, for biological and geo-chemical processes in soil, is not defined in these models. The omission of soil structure from soil characterization and modeling does not allow for coupling disciplinary models for these processes with soil water models. This article presents a soil water structure model, Kamel®, which was developed based on a new paradigm in soil physics where the hierarchical soil structure is taken into account allowing for defining its thermodynamic properties. After a review of soil physics principles which forms the basis of the paradigm, we describe the basic relationships and functionality of the model. Kamel® runs with a set of 15 soil input parameters, the pedohydral parameters, which are parameters of the physically-based equations of four soil characteristic curves that can be measured in the laboratory. For cases where some of these parameters are not available, we show how to estimate these parameters from commonly available soil information using published pedotransfer functions. A published field experimental study on the dynamics of the soil moisture profile following a pounded infiltration rainfall event was used as an example to demonstrate soil characterization and Kamel® simulations. The simulated soil moisture profile for a period of 60 days showed very good agreement with experimental field data. Simulations using input data calculated from soil texture and pedotransfer functions were also generated and compared to simulations of the more ideal characterization. The later comparison illustrates how Kamel® can be used and adapt to any case of soil data availability. As physically based model on soil structure, it may be used as a standard reference to evaluate other soil-water models and also pedotransfer functions at a given location or agronomical situation.

The Role of Iron-Bearing Minerals in NO2 to HONO Conversion on Soil Surfaces.

PubMed

Kebede, Mulu A; Bish, David L; Losovyj, Yaroslav; Engelhard, Mark H; Raff, Jonathan D

2016-08-16

Nitrous acid (HONO) accumulates in the nocturnal boundary layer where it is an important source of daytime hydroxyl radicals. Although there is clear evidence for the involvement of heterogeneous reactions of NO2 on surfaces as a source of HONO, mechanisms remain poorly understood. We used coated-wall flow tube measurements of NO2 reactivity on environmentally relevant surfaces (Fe (hydr)oxides, clay minerals, and soil from Arizona and the Saharan Desert) and detailed mineralogical characterization of substrates to show that reduction of NO2 by Fe-bearing minerals in soil can be a more important source of HONO than the putative NO2 hydrolysis mechanism. The magnitude of NO2-to-HONO conversion depends on the amount of Fe(2+) present in substrates and soil surface acidity. Studies examining the dependence of HONO flux on substrate pH revealed that HONO is formed at soil pH < 5 from the reaction between NO2 and Fe(2+)(aq) present in thin films of water coating the surface, whereas in the range of pH 5-8 HONO stems from reaction of NO2 with structural iron or surface complexed Fe(2+) followed by protonation of nitrite via surface Fe-OH2(+) groups. Reduction of NO2 on ubiquitous Fe-bearing minerals in soil may explain HONO accumulation in the nocturnal boundary layer and the enhanced [HONO]/[NO2] ratios observed during dust storms in urban areas.

Sorption of Hydrophobic Organic Compounds on Natural Sorbents and Organoclays from Aqueous and Non-Aqueous Solutions: A Mini-Review

PubMed Central

Moyo, Francis; Tandlich, Roman; Wilhelmi, Brendan S.; Balaz, Stefan

2014-01-01

Renewed focus on the sorption of hydrophobic organic chemicals (HOCs) onto mineral surfaces and soil components is required due to the increased and wider range of organic pollutants being released into the environment. This mini-review examines the possibility of the contribution and mechanism of HOC sorption onto clay mineral sorbents such as kaolinite, and soil organic matter and the possible role of both in the prevention of environmental contamination by HOCs. Literature data indicates that certain siloxane surfaces can be hydrophobic. Therefore soils can retain HOCs even at low soil organic levels and the extent will depend on the structure of the pollutant and the type and concentration of clay minerals in the sorbent. Clay minerals are wettable by nonpolar solvents and so sorption of HOCs onto them from aqueous and non-aqueous solutions is possible. This is important for two reasons: firstly, the movement and remediation of soil environments will be a function of the concentration and type of clay minerals in the soil. Secondly, low-cost sorbents such as kaolinite and expandable clays can be added to soils or contaminated environments as temporary retention barriers for HOCs. Inorganic cations sorbed onto the kaolinite have a strong influence on the rate and extent of sorption of hydrophobic organic pollutants onto kaolinite. Structural sorbate classes that can be retained by the kaolinite matrix are limited by hydrogen bonding between hydroxyl groups of the octahedral alumosilicate sheet and the tetrahedral sheet with silicon. Soil organic carbon plays a key role in the sorption of HOCs onto soils, but the extent will be strongly affected by the structure of the organic soil matter and the presence of soot. Structural characterisation of soil organic matter in a particular soil should be conducted during a particular contamination event. Contamination by mining extractants and antibiotics will require renewed focus on the use of the QSAR approaches in the context of the sorption of HOCs onto clay minerals from aqueous and non-aqueous solutions. PMID:24821385

Composition and molecular scale structure of nanophases formed by precipitation of biotite weathering products

NASA Astrophysics Data System (ADS)

Tamrat, Wuhib Zewde; Rose, Jérôme; Grauby, Olivier; Doelsch, Emmanuel; Levard, Clément; Chaurand, Perrine; Basile-Doelsch, Isabelle

2018-05-01

Because of their large surface area and reactivity, nanometric-size soil mineral phases have a high potential for soil organic matter stabilization, contaminant sorption or soil aggregation. In the literature, Fe and Al phases have been the main targets of batch-synthesized nanomineral studies while nano-aluminosilicates (Al and Si phases) have been mainly studied in Andic soils. In the present work, we synthesized secondary nanophases of Fe, Al and Si. To simulate a system as close as possible to soil conditions, we conducted laboratory simulations of the processes of (1) biotite alteration in acidic conditions producing a Al Si Fe Mg K leachate solution and (2) the following neoformation of secondary nanophases by titrating the leachate solution to pH 4.2, 5 and 7. The morphology of the nanophases, their size, crystallinity and chemistry were characterized by TEM-EDX on single particles and their local atomic structure by EXAFS (Extended X-ray Absorption Fine Structure) at the Fe absorption K-edge. The main nanophases formed were amorphous particles 10-60 nm in size whose composition (dominated by Fe and Si) was strongly controlled by the pH conditions at the end of the titration. At pH 4.2 and pH 7, the structure of the nanophases was dominated by the polymerization of Fe, which was hindered by Al, Si, Mg and K. Conversely, at pH 5, the polymerization of Fe was counteracted by precipitation of high amounts of Si. The synthetized nanophases were estimated to be rather analogous to nanophases formed in natural biotite-bearing soils. Because of their small size and potential high surface reactivity, the adsorption capacities of these nanophases with respect to the OM should be revisited in the framework of soil C storage.

Organic matter controls of soil water retention in an alpine grassland and its significance for hydrological processes

NASA Astrophysics Data System (ADS)

Yang, Fei; Zhang, Gan-Lin; Yang, Jin-Ling; Li, De-Cheng; Zhao, Yu-Guo; Liu, Feng; Yang, Ren-Min; Yang, Fan

2014-11-01

Soil water retention influences many soil properties and soil hydrological processes. The alpine meadows and steppes of the Qilian Mountains on the northeast border of the Qinghai-Tibetan Plateau form the source area of the Heihe River, the second largest inland river in China. The soils of this area therefore have a large effect on water movement and storage of the entire watershed. In order to understand the controlling factors of soil water retention and how they affect regional eco-hydrological processes in an alpine grassland, thirty-five pedogenic horizons in fourteen soil profiles along two facing hillslopes in typical watersheds of this area were selected for study. Results show that the extensively-accumulated soil organic matter plays a dominant role in controlling soil water retention in this alpine environment. We distinguished two mechanisms of this control. First, at high matric potentials soil organic matter affected soil water retention mainly through altering soil structural parameters and thereby soil bulk density. Second, at low matric potentials the water adsorbing capacity of soil organic matter directly affected water retention. To investigate the hydrological functions of soils at larger scales, soil water retention was compared by three generalized pedogenic horizons. Among these soil horizons, the mattic A horizon, a diagnostic surface horizon of Chinese Soil Taxonomy defined specially for alpine meadow soils, had the greatest soil water retention over the entire range of measured matric potentials. Hillslopes with soils having these horizons are expected to have low surface runoff. This study promotes the understanding of the critical role of alpine soils, especially the vegetated surface soils in controlling the eco-hydrological processes in source regions of the Heihe River watershed.

Soil Moisture or Groundwater?

NASA Astrophysics Data System (ADS)

Swenson, S. C.; Lawrence, D. M.

2017-12-01

Partitioning the vertically integrated water storage variations estimated from GRACE satellite data into the components of which it is comprised requires independent information. Land surface models, which simulate the transfer and storage of moisture and energy at the land surface, are often used to estimate water storage variability of snow, surface water, and soil moisture. To obtain an estimate of changes in groundwater, the estimates of these storage components are removed from GRACE data. Biases in the modeled water storage components are therefore present in the residual groundwater estimate. In this study, we examine how soil moisture variability, estimated using the Community Land Model (CLM), depends on the vertical structure of the model. We then explore the implications of this uncertainty in the context of estimating groundwater variations using GRACE data.

Using Combustion Synthesis to Reinforce Berms and Other Regolith Structures

NASA Technical Reports Server (NTRS)

Rodriquez, Gary

2013-01-01

The Moonraker Excavator and other tools under development for use on the Moon, Mars, and asteroids will be employed to construct a number of civil engineering projects and to mine the soil. Mounds of loose soil will be subject to the local transport mechanisms plus artificial mechanisms such as blast effects from landers and erosion from surface vehicles. Some of these structures will require some permanence, with a minimum of maintenance and upkeep. Combustion Synthesis (CS) is a family of processes and techniques whereby chemistry is used to transform materials, often creating flame in a hard vacuum. CS can be used to stabilize civil engineering works such as berms, habitat shielding, ramps, pads, roadways, and the like. The method is to unroll thin sheets of CS fabric between layers of regolith and then fire the fabric, creating a continuous sheet of crusty material to be interposed among layers of loose regolith. The combination of low-energy processes, ISRU (in situ resource utilization) excavator, and CS fabrics, seems compelling as a general method for establishing structures of some permanence and utility, especially in the role of robotic missions as precursors to manned exploration and settlement. In robotic precursory missions, excavator/ mobility ensembles mine the Lunar surface, erect constructions of soil, and dispense sheets of CS fabrics that are covered with layers of soil, fired, and then again covered with layers of soil, iterating until the desired dimensions and forms are achieved. At the base of each berm, for example, is a shallow trench lined with CS fabric, fired and filled, mounded, and then covered and fired, iteratively to provide a footing against lateral shear. A larger trench is host to a habitat module, backfilled, covered with fabric, covered with soil, and fired. Covering the applied CS fabric with layers of soil before firing allows the resulting matrix to incorporate soil both above and below the fabric ply into the fused layer, developing a very irregular surface which, like sandpaper, can provide an anchor for loose soil. CS fabrics employ a coarse fiberglass weave that persists as reinforcement for the fired material. The fiberglass softens at a temperature that exceeds the combustion temperature by factors of two to three, and withstands the installation process. This type of structure should be more resistant to rocket blast effects from Lunar landers.

Study of the Effect of Turbulence and Large Obstacles on the Evaporation from Bare Soil Surface through Coupled Free-flow and Porous-medium Flow Model

NASA Astrophysics Data System (ADS)

Gao, B.; Smits, K. M.

2017-12-01

Evaporation is a strongly coupled exchange process of mass, momentum and energy between the atmosphere and the soil. Several mechanisms influence evaporation, such as the atmospheric conditions, the structure of the soil surface, and the physical properties of the soil. Among the previous studies associated with evaporation modeling, most efforts use uncoupled models which simplify the influences of the atmosphere and soil through the use of resistance terms. Those that do consider the coupling between the free flow and porous media flow mainly consider flat terrain with grain-scale roughness. However, larger obstacles, which may form drags or ridges allowing normal convective air flow through the soil, are common in nature and may affect the evaporation significantly. Therefore, the goal of this work is to study the influence of large obstacles such as wavy surfaces on the flow behavior within the soil and exchange processes to the atmosphere under turbulent free-flow conditions. For simplicity, the soil surface with large obstacles are represented by a simple wavy surface. To do this, we modified a previously developed theory for two-phase two-component porous-medium flow, coupling it to single-phase two-component turbulent flow to simulate and analyze the evaporation from wavy soil surfaces. Detailed laboratory scale experiments using a wind tunnel interfaced with a porous media tank were carried out to test the modeling results. The characteristics of turbulent flow across a permeable wavy surface are discussed. Results demonstrate that there is an obvious recirculation zone formed at the surface, which is special because of the accumulation of water vapor and the thicker boundary layer in this area. In addition, the influences of both the free flow and porous medium on the evaporation are also analyzed. The porous medium affects the evaporation through the amount of water it can provide to the soil surface; while the atmosphere influences the evaporation through the gradients formed within the boundary layer. This study gives a primary cognition on the evaporation from bare soil surface with obstacles. Ongoing work will include a deep understanding of the mechanisms which may provide the basis for land-atmosphere study on field scale.

A Comparison of Microbial Community Structures by Depth and Season Under Switchgrass

NASA Astrophysics Data System (ADS)

Fansler, S. J.; Smith, J. L.; Bolton, H.; Bailey, V. L.

2008-12-01

As part of a multidisciplinary study of C sequestration in switchgrass production systems, the soil microbial community structure was monitored at 6 different depths (reaching 90 cm) in both spring and autumn. Microbial community structure was assessed using ribosomal intergenic spacer analysis (RISA), and primers were used specific to either bacteria or fungi, generating microbial community fingerprints for each taxonomic group. Diverse microbial communities for both groups were detected throughout the soil profile. It is notable that while community structure clearly changed with depth, there was the deepest soil samples still retained relatively diverse communities. Seasonally, differences are clearly evident within plots at the surface. As the plots were replicated, significant differences in the community fingerprints with depth and season are reported.

Restoring the biological crust cover of soils across biomes in arid North America

NASA Astrophysics Data System (ADS)

Garcia-Pichel, Ferran; Antoninka, Anita; Bowker, Matthew; Giraldo Silva, Ana; Nelson, Corey; Velasco Ayuso, Sergio; Barger, Nichole; Belnap, Jayne; Reed, Sasha; Duniway, Michael

2015-04-01

Biological soil crust communities provide important ecosystem services to arid lands, particularly regarding soil fertility and stability against erosion. In North America, and in many other areas of the globe, increasingly intense human activities, ranging from cattle grazing to military training, have resulted in the significant deterioration of biological soil surface cover of soils. With the intent of attaining sustainable land use practices, we are conducting a 5-year, multi-institutional research effort to develop feasible soil crusts restoration strategies for US military lands. We are including field sites of varying climatic regions (warm and cold deserts, in the Chihuahuan Desert and in the Great Basin, respectively) and varying edaphic characteristics (sandy and silty soils in each). We have multiple aims. First, we aim to establishing effective "biocrust nurseries" that produce viable and pedigreed inoculum, as a supply center for biocrust restoration and for research and development. Second, we aim to develop optimal field application methods of biocrust inoculum in a series of field trials. Currently in our second year of research, we will be reporting on significant advances made on optimizing methodologies for the large-scale supply of inoculum based on a) pedigreed laboratory cultures that match the microbial community structure of the original sites, and b) "in soil" biomass enhancement, whereby small amounts of local crusts are nursed under greenhouse conditions to yield hundred-fold increases in biomass without altering significantly community structure. We will also report on field trials for methodologies in field application, which included shading, watering, application of chemical polymers, and soil surface roughening. In a soon-to-be-initiated effort we also aim to evaluate soil and plant responses to biocrust restoration with respect to plant community structure, soil fertility, and soil stability, in multi-factorial field experiments. An important part of the plan will be to construct effective channels for sharing challenges and solutions in biocrust restoration with military and federal land managers.

Physical and chemical properties of the Martian soil: Review of resources

NASA Technical Reports Server (NTRS)

Stoker, C. R.; Gooding, James L.; Banin, A.; Clark, Benton C.; Roush, Ted

1991-01-01

The chemical and physical properties of Martian surface materials are reviewed from the perspective of using these resources to support human settlement. The resource potential of Martian sediments and soils can only be inferred from limited analyses performed by the Viking Landers (VL), from information derived from remote sensing, and from analysis of the SNC meteorites thought to be from Mars. Bulk elemental compositions by the VL inorganic chemical (x ray fluorescence) analysis experiments have been interpreted as evidence for clay minerals (possibly smectites) or mineraloids (palagonite) admixed with sulfate and chloride salts. The materials contained minerals bearing Fe, Ti, Al, Mg and Si. Martian surface materials may be used in many ways. Martian soil, with appropriate preconditioning, can probably be used as a plant growth medium, supplying mechanical support, nutrient elements, and water at optimal conditions to the plants. Loose Martian soils could be used to cover structures and provide radiation shielding for surface habitats. Martian soil could be wetted and formed into abode bricks used for construction. Duricrete bricks, with strength comparable to concrete, can probably be formed using compressed muds made from martian soil.

Interactions between soil texture, water, and nutrients control patterns of biocrusts abundance and structure

NASA Astrophysics Data System (ADS)

Young, Kristina; Bowker, Matthew; Reed, Sasha; Howell, Armin

2017-04-01

Heterogeneity in the abiotic environment structures biotic communities by controlling niche space and parameters. This has been widely observed and demonstrated in vascular plant and other aboveground communities. While soil organisms are presumably also strongly influenced by the physical and chemical dimensions of the edaphic environment, there are fewer studies linking the development, structure, productivity or function of surface soil communities to specific edaphic gradients. Here, we use biological soil crusts (biocrusts) as a model system to determine mechanisms regulating community structure of soil organisms. We chose soil texture to serve as an edaphic gradient because of soil texture's influence over biocrust distribution on a landscape level. We experimentally manipulated texture in constructed soil, and simultaneously manipulated two main outcomes of texture, water and nutrient availability, to determine the mechanism underlying texture's influence on biocrust abundance and structure. We grew biocrust communities from a field-sourced inoculum on four different soil textures, sieved from the same parent soil material, manipulating watering levels and nutrient additions across soil textures in a full-factorial design over a 5-month period of time. We measured abundance and structure of biocrusts over time, and measured two metrics of function, N2 fixation rates and soil stabilization, at the conclusion of the experiment. Our results showed finer soil textures resulted in faster biocrust community development and dominance by mosses, whereas coarser textures grew more slowly and had biocrust communities dominated by cyanobacteria and lichen. Additionally, coarser textured soils contained cyanobacterial filaments significantly deeper into the soil profile than fine textured soils. N2-fixation values increased with increasing moss cover and decreased with increasing cyanobacterial cover, however, the rate of change depended on soil texture and water amount. Soil shear resistance was highest on finer textured soil with the highest watering treatment, whereas compression resistance was highest on the coarsest textured soils with the highest watering amounts. Nutrient addition did not influence total cover or biocrust function, but did decrease lichen cover. Taken together, these results suggest that interactions between soil texture, water, and to a lesser degree nutrients, create predictable patterns in biocrust assemblage and offers a mechanistic understanding of edaphic controls over biocrust abundance and structure. These insights add to our increasing understanding of how edaphic gradients structure soil communities.

Evaluating the importance of characterizing soil structure and horizons in parameterizing a hydrologic process model

USGS Publications Warehouse

Mirus, Benjamin B.

2015-01-01

Incorporating the influence of soil structure and horizons into parameterizations of distributed surface water/groundwater models remains a challenge. Often, only a single soil unit is employed, and soil-hydraulic properties are assigned based on textural classification, without evaluating the potential impact of these simplifications. This study uses a distributed physics-based model to assess the influence of soil horizons and structure on effective parameterization. This paper tests the viability of two established and widely used hydrogeologic methods for simulating runoff and variably saturated flow through layered soils: (1) accounting for vertical heterogeneity by combining hydrostratigraphic units with contrasting hydraulic properties into homogeneous, anisotropic units and (2) use of established pedotransfer functions based on soil texture alone to estimate water retention and conductivity, without accounting for the influence of pedon structures and hysteresis. The viability of this latter method for capturing the seasonal transition from runoff-dominated to evapotranspiration-dominated regimes is also tested here. For cases tested here, event-based simulations using simplified vertical heterogeneity did not capture the state-dependent anisotropy and complex combinations of runoff generation mechanisms resulting from permeability contrasts in layered hillslopes with complex topography. Continuous simulations using pedotransfer functions that do not account for the influence of soil structure and hysteresis generally over-predicted runoff, leading to propagation of substantial water balance errors. Analysis suggests that identifying a dominant hydropedological unit provides the most acceptable simplification of subsurface layering and that modified pedotransfer functions with steeper soil-water retention curves might adequately capture the influence of soil structure and hysteresis on hydrologic response in headwater catchments.

Microbial Community and Functional Structure Significantly Varied among Distinct Types of Paddy Soils But Responded Differently along Gradients of Soil Depth Layers

PubMed Central

Bai, Ren; Wang, Jun-Tao; Deng, Ye; He, Ji-Zheng; Feng, Kai; Zhang, Li-Mei

2017-01-01

Paddy rice fields occupy broad agricultural area in China and cover diverse soil types. Microbial community in paddy soils is of great interest since many microorganisms are involved in soil functional processes. In the present study, Illumina Mi-Seq sequencing and functional gene array (GeoChip 4.2) techniques were combined to investigate soil microbial communities and functional gene patterns across the three soil types including an Inceptisol (Binhai), an Oxisol (Leizhou), and an Ultisol (Taoyuan) along four profile depths (up to 70 cm in depth) in mesocosm incubation columns. Detrended correspondence analysis revealed that distinctly differentiation in microbial community existed among soil types and profile depths, while the manifest variance in functional structure was only observed among soil types and two rice growth stages, but not across profile depths. Along the profile depth within each soil type, Acidobacteria, Chloroflexi, and Firmicutes increased whereas Cyanobacteria, β-proteobacteria, and Verrucomicrobia declined, suggesting their specific ecophysiological properties. Compared to bacterial community, the archaeal community showed a more contrasting pattern with the predominant groups within phyla Euryarchaeota, Thaumarchaeota, and Crenarchaeota largely varying among soil types and depths. Phylogenetic molecular ecological network (pMEN) analysis further indicated that the pattern of bacterial and archaeal communities interactions changed with soil depth and the highest modularity of microbial community occurred in top soils, implying a relatively higher system resistance to environmental change compared to communities in deeper soil layers. Meanwhile, microbial communities had higher connectivity in deeper soils in comparison with upper soils, suggesting less microbial interaction in surface soils. Structure equation models were developed and the models indicated that pH was the most representative characteristics of soil type and identified as the key driver in shaping both bacterial and archaeal community structure, but did not directly affect microbial functional structure. The distinctive pattern of microbial taxonomic and functional composition along soil profiles implied functional redundancy within these paddy soils. PMID:28611747

Microbial Community and Functional Structure Significantly Varied among Distinct Types of Paddy Soils But Responded Differently along Gradients of Soil Depth Layers.

PubMed

Bai, Ren; Wang, Jun-Tao; Deng, Ye; He, Ji-Zheng; Feng, Kai; Zhang, Li-Mei

2017-01-01

Paddy rice fields occupy broad agricultural area in China and cover diverse soil types. Microbial community in paddy soils is of great interest since many microorganisms are involved in soil functional processes. In the present study, Illumina Mi-Seq sequencing and functional gene array (GeoChip 4.2) techniques were combined to investigate soil microbial communities and functional gene patterns across the three soil types including an Inceptisol (Binhai), an Oxisol (Leizhou), and an Ultisol (Taoyuan) along four profile depths (up to 70 cm in depth) in mesocosm incubation columns. Detrended correspondence analysis revealed that distinctly differentiation in microbial community existed among soil types and profile depths, while the manifest variance in functional structure was only observed among soil types and two rice growth stages, but not across profile depths. Along the profile depth within each soil type, Acidobacteria , Chloroflexi , and Firmicutes increased whereas Cyanobacteria , β -proteobacteria , and Verrucomicrobia declined, suggesting their specific ecophysiological properties. Compared to bacterial community, the archaeal community showed a more contrasting pattern with the predominant groups within phyla Euryarchaeota , Thaumarchaeota , and Crenarchaeota largely varying among soil types and depths. Phylogenetic molecular ecological network (pMEN) analysis further indicated that the pattern of bacterial and archaeal communities interactions changed with soil depth and the highest modularity of microbial community occurred in top soils, implying a relatively higher system resistance to environmental change compared to communities in deeper soil layers. Meanwhile, microbial communities had higher connectivity in deeper soils in comparison with upper soils, suggesting less microbial interaction in surface soils. Structure equation models were developed and the models indicated that pH was the most representative characteristics of soil type and identified as the key driver in shaping both bacterial and archaeal community structure, but did not directly affect microbial functional structure. The distinctive pattern of microbial taxonomic and functional composition along soil profiles implied functional redundancy within these paddy soils.

Active microwave remote sensing research program plan. Recommendations of the Earth Resources Synthetic Aperture Radar Task Force. [application areas: vegetation canopies, surface water, surface morphology, rocks and soils, and man-made structures

NASA Technical Reports Server (NTRS)

1980-01-01

A research program plan developed by the Office of Space and Terrestrial Applications to provide guidelines for a concentrated effort to improve the understanding of the measurement capabilities of active microwave imaging sensors, and to define the role of such sensors in future Earth observations programs is outlined. The focus of the planned activities is on renewable and non-renewable resources. Five general application areas are addressed: (1) vegetation canopies, (2) surface water, (3) surface morphology, (4) rocks and soils, and (5) man-made structures. Research tasks are described which, when accomplished, will clearly establish the measurement capabilities in each area, and provide the theoretical and empirical results needed to specify and justify satellite systems using imaging radar sensors for global observations.

The spectroscopic chemical and photophysical properties of Martian soils and their analogs

NASA Technical Reports Server (NTRS)

Coyne, Lelia M.

1987-01-01

The program of research outlined should advance significantly the understanding of the spectral signal of montmorillonites in general and the variations produced in it by structural and surface ferric and ferrous iron and interlayer water as a function of several environmental conditions that are different between Earth and Mars. In addition, an extensive data base was collected providing spectral characterization of several features (iron, both surface and structural, OH-groups, both structural and from adsorbed water and O(-) centers) that are known, or thought to be, influential in directing the surface activity of these important materials. With this data base with which to assess the results of the Viking labeled release simulation studies, it should be possible to gain important insights into the mechanisms of surface reactivity for this important chemical reaction. The results to be gained from these studies will provide a significant body of ground base truth from which to assess: the presence of smectite clays on Mars; the mineralogical form in which the Martian iron is bound; establish upper limits on the present surface water content of Martian soils; perhaps provide insights on the Martian surface radiation history; and to make strong predictions about the nature of surface chemistry on Mars, if iron-bearing clays are a significant component of the surface mineralogical assemblage.

Spatial patterns of plant litter in a tidal freshwater marsh and implications for marsh persistence.

PubMed

Elmore, Andrew J; Engelhardt, Katharina A M; Cadol, Daniel; Palinkas, Cindy M

2016-04-01

The maintenance of marsh platform elevation under conditions of sea level rise is dependent on mineral sediment supply to marsh surfaces and conversion of above- and belowground plant biomass to soil organic material. These physical and biological processes interact within the tidal zone, resulting in elevation-dependent processes contributing to marsh accretion. Here, we explore spatial pattern in a variable related to aboveground biomass, plant litter, to reveal its role in the maintenance of marsh surfaces. Plant litter persisting through the dormant season represents the more recalcitrant portion of plant biomass, and as such has an extended period of influence on ecosystem processes. We conducted a field and remote sensing analysis of plant litter height, aboveground biomass, vertical cover, and stem density (collectively termed plant litter structure) at a tidal freshwater marsh located within the Potomac River estuary, USA. LiDAR and field observations show that plant litter structure becomes more prominent with increasing elevation. Spatial patterns in litter structure exhibit stability from year to year and correlate with patterns in soil organic matter content, revealed by measuring the loss on ignition of surface sediments. The amount of mineral material embedded within plant litter decreases with increasing elevation, representing an important tradeoff with litter structure. Therefore, at low elevations where litter structure is short and sparse, the role of plant litter is to capture sediment; at high elevations where litter structure is tall and dense, aboveground litter contributes organic matter to soil development. This organic matter contribution has the potential to eclipse that of belowground biomass as the root:shoot ratio of dominant species at high elevations is low compared to that of dominant species at low elevations. Because of these tradeoffs in mineral and organic matter incorporation into soil across elevation gradients, the rate of marsh surface elevation change is remarkably consistent across elevation. Because of the role of plant litter in marsh ecosystem processes, monitoring and assessment of these dynamic geomorphic marsh landscapes might be streamlined through the measurement of plant litter structure, either via LiDAR technologies or field observation.

Rich in life but poor in data: the known knowns and known unknowns of modelling how soil biology drives soil structure

NASA Astrophysics Data System (ADS)

Hallett, Paul; Ogden, Mike

2015-04-01

Soil biology has a fascinating capacity to manipulate pore structure by altering or overcoming hydrological and mechanical properties of soil. Many have postulated, quite rightly, that this capacity of soil biology to 'engineer' its habitat drives its diversity, improves competitiveness and increases resilience to external stresses. A large body of observational research has quantified pore structure evolution accompanied by the growth of organisms in soil. Specific compounds that are exuded by organisms or the biological structures they create have been isolated and found to correlate well with observed changes to pore structure or soil stability. This presentation will provide an overview of basic mechanical and hydrological properties of soil that are affected by biology, and consider missing data that are essential to model how they impact soil structure evolution. Major knowledge gaps that prevent progress will be identified and suggestions will be made of how research in this area should progress. We call for more research to gain a process based understanding of structure formation by biology, to complement observational studies of soil structure before and after imposed biological activity. Significant advancement has already been made in modelling soil stabilisation by plant roots, by combining data on root biomechanics, root-soil interactions and soil mechanical properties. Approaches for this work were developed from earlier materials science and geotechnical engineering research, and the same ethos should be adopted to model the impacts of other biological compounds. Fungal hyphae likely reinforce soils in a similar way to plant roots, with successful biomechanical measurements of these micron diameter structures achieved with micromechanical test frames. Extending root reinforcement models to fungi would not be a straightforward exercise, however, as interparticle bonding and changes to pore water caused by fungal exudates could have a major impact on structure formation and stability. Biological exudates from fungi, bacteria or roots have been found to decrease surface tension and increase viscosity of pore water, with observed impacts to soil strength and water retention. Modelling approaches developed in granular mechanics and geotechnical engineering could be built upon to incorporate biological transformations of hydrological and mechanical properties of soil. With new testing approaches, adapted from materials science, pore scale hydromechanical impacts from biological exudates can be quantified. The research can be complemented with model organisms with differences in biological structures (e.g. root hair mutants), exudation or other properties. Coupled with technological advances that provide 4D imaging of soil structure at relatively rapid capture rates, the potential opportunities to disentangle and model how biology drives soil structure evolution and stability are vast. By quantifying basic soil hydrological and mechanical processes that are driven by soil biology, unknown unknowns may also emerge, providing new insight into how soils function.

High-resolution synchrotron imaging shows that root hairs influence rhizosphere soil structure formation.

PubMed

Koebernick, Nicolai; Daly, Keith R; Keyes, Samuel D; George, Timothy S; Brown, Lawrie K; Raffan, Annette; Cooper, Laura J; Naveed, Muhammad; Bengough, Anthony G; Sinclair, Ian; Hallett, Paul D; Roose, Tiina

2017-10-01

In this paper, we provide direct evidence of the importance of root hairs on pore structure development at the root-soil interface during the early stage of crop establishment. This was achieved by use of high-resolution (c. 5 μm) synchrotron radiation computed tomography (SRCT) to visualise both the structure of root hairs and the soil pore structure in plant-soil microcosms. Two contrasting genotypes of barley (Hordeum vulgare), with and without root hairs, were grown for 8 d in microcosms packed with sandy loam soil at 1.2 g cm -3 dry bulk density. Root hairs were visualised within air-filled pore spaces, but not in the fine-textured soil regions. We found that the genotype with root hairs significantly altered the porosity and connectivity of the detectable pore space (> 5 μm) in the rhizosphere, as compared with the no-hair mutants. Both genotypes showed decreasing pore space between 0.8 and 0.1 mm from the root surface. Interestingly the root-hair-bearing genotype had a significantly greater soil pore volume-fraction at the root-soil interface. Effects of pore structure on diffusion and permeability were estimated to be functionally insignificant under saturated conditions when simulated using image-based modelling. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

Digital modelling of landscape and soil in a mountainous region: A neuro-fuzzy approach

NASA Astrophysics Data System (ADS)

Viloria, Jesús A.; Viloria-Botello, Alvaro; Pineda, María Corina; Valera, Angel

2016-01-01

Research on genetic relationships between soil and landforms has largely improved soil mapping. Recent technological advances have created innovative methods for modelling the spatial soil variation from digital elevation models (DEMs) and remote sensors. This generates new opportunities for the application of geomorphology to soil mapping. This study applied a method based on artificial neural networks and fuzzy clustering to recognize digital classes of land surfaces in a mountainous area in north-central Venezuela. The spatial variation of the fuzzy memberships exposed the areas where each class predominates, while the class centres helped to recognize the topographic attributes and vegetation cover of each class. The obtained classes of terrain revealed the structure of the land surface, which showed regional differences in climate, vegetation, and topography and landscape stability. The land-surface classes were subdivided on the basis of the geological substratum to produce landscape classes that additionally considered the influence of soil parent material. These classes were used as a framework for soil sampling. A redundancy analysis confirmed that changes of landscape classes explained the variation in soil properties (p = 0.01), and a Kruskal-Wallis test showed significant differences (p = 0.01) in clay, hydraulic conductivity, soil organic carbon, base saturation, and exchangeable Ca and Mg between classes. Thus, the produced landscape classes correspond to three-dimensional bodies that differ in soil conditions. Some changes of land-surface classes coincide with abrupt boundaries in the landscape, such as ridges and thalwegs. However, as the model is continuous, it disclosed the remaining variation between those boundaries.

Visual soil evaluation - future research requirements

NASA Astrophysics Data System (ADS)

Emmet-Booth, Jeremy; Forristal, Dermot; Fenton, Owen; Ball, Bruce; Holden, Nick

2017-04-01

A review of Visual Soil Evaluation (VSE) techniques (Emmet-Booth et al., 2016) highlighted their established utility for soil quality assessment, though some limitations were identified; (1) The examination of aggregate size, visible intra-porosity and shape forms a key assessment criterion in almost all methods, thus limiting evaluation to structural form. The addition of criteria that holistically examine structure may be desirable. For example, structural stability can be indicated using dispersion tests or examining soil surface crusting, while the assessment of soil colour may indirectly indicate soil organic matter content, a contributor to stability. Organic matter assessment may also indicate structural resilience, along with rooting, earthworm numbers or shrinkage cracking. (2) Soil texture may influence results or impeded method deployment. Modification of procedures to account for extreme texture variation is desirable. For example, evidence of compaction in sandy or single grain soils greatly differs to that in clayey soils. Some procedures incorporate separate classification systems or adjust deployment based on texture. (3) Research into impacts of soil moisture content on VSE evaluation criteria is required. Criteria such as rupture resistance and shape may be affected by moisture content. It is generally recommended that methods are deployed on moist soils and quantification of influences of moisture variation on results is necessary. (4) Robust sampling strategies for method deployment are required. Dealing with spatial variation differs between methods, but where methods can be deployed over large areas, clear instruction on sampling is required. Additionally, as emphasis has been placed on the agricultural production of soil, so the ability of VSE for exploring structural quality in terms of carbon storage, water purification and biodiversity support also requires research. References Emmet-Booth, J.P., Forristal. P.D., Fenton, O., Ball, B.C. & Holden, N.M. 2016. A review of visual soil evaluation techniques for soil structure. Soil Use and Management, 32, 623-634.

How far can we prevent further physical soil degradation in the future?

NASA Astrophysics Data System (ADS)

Horn, Rainer

2017-04-01

Arable as well as forest soils are exposed to increasing external stresses, which coincide with a further and deeper reaching soil degradation, which may result in an aggravation of hydraulic, gaseous, thermal but also physicochemical and chemical soil functions. The decline coincides with a simultaneous reduction in useable land areas and worsens food production amongst others. Therefore, it is mandatory, that stable soil structure from the surface down to depth prevents soil compaction, sustains water infiltration, reduces rates of soil erosion by water and wind in each case to the minimum possible under the soil, terrain, land use, and climatic conditions in which the soils occur. It improves organic carbon storage in soils and optimizes microbial activity and functions. These benefits coincide with sustainable soil properties and soil management systems, which prevent - deep mechanical stress propagation which can cause irreversible soil deformation, - loss of surface soil layers with coinciding organic and mineral nutrient pool available for microbial processing and plant uptake, - Truncation of soil horizons, or damage on private and public infrastructures (roads, houses) and downstream fields. In order to prevent negative impacts on soils, it is recommended, that A) concerning prevention of soil compaction - stresses applied to soils shall not exceed the mechanical soil stability to maintain the actual functioning of chemical, physical and biological processes and to utilize their resilience (i.e. the elasticity), - land use management strategies have to be related to the actual soil properties in order to optimize plant growth, yield, filtering and buffering of infiltrating water, and carbon sequestration. B) soil erosion by - water, wind, and tillage is counteracted by an adequate surface soil stability including a site specific residue management (e.g. conservation tillage), controlled traffic and harvesting, ecological grassland use strategies (e.g. fodder production and harvesting, adequate animal grazing), - wind is furthermore minimized by adequate hedgerow plantations, continuous cover crop growth, optimized particle bindings by water, infiltrating organic acids, appropriate grazing intensity. Agroforestry can be considered as an additional positive measure to reduce soil erosion risks generally and to ameliorate degraded sites. C) -plant cover on slopes remains untouched, overgrazing and consecutive soil homogenization especially under moist climatic conditions must be prevented but adjusted to the actual structure stability of the hillsides. The communication of these findings followed by application of such measures can help farmers and foresters as well as landowners to prevent (further) physical soil degradation in the future.

The influence of continuous rice cultivation and different waterlogging periods on morphology, clay mineralogy, Eh, pH and K in paddy soils.

PubMed

Bahmanyar, M A

2007-09-01

The effect of different rice cultivation periods on the properties of selected soils in alluvial plain were studied in Mazandaran province (north of Iran) in 2004. Soils were sampled form 0, 6, 16, 26 and over 40 years rice cultivation fields. In each treatment three soil profiles and six nearby auger holes were studied. The present study results indicated that continuous rice cultivation have changed soil moisture regime from xeric to aquic, soil color from brown to grayish, surface horizons from mollic to ochric epipedon and soil structure changed from granular or blocky to massive. Therefore, the soil order has changed from Mollisols to Inceptisols. No illuviation and eluviation of clay minerals occurred as a consequence of rice cultivation. X-ray diffraction analysis showed that clay minerals in non-rice cultivated field were illite, vermiculite, montmorillonite, kaolinite and chlorite, but in rice field were illite, montmorillonite, kaolinite and chlorite, respectively. In contrast of montmorillonite, the amount of illite and vermiculite have been decreased by increasing periods of rice cultivation. The pH values of the saturated soil surface in six weeks past plantation have shifted toward neutrality. While Eh value of non-paddy soils were about +90 mv, surface horizons of paddy soils at field conditions had Eh value about +40, -12, -84, -122 mv, respectively. The amounts of organic matter and available Fe, Mn, Zn and Cu were increased whereas available K was decreased in paddy soils.

Accomplishments of the NASA Johnson Space Center portion of the soil moisture project in fiscal year 1981

NASA Technical Reports Server (NTRS)

Paris, J. F.; Arya, L. M.; Davidson, S. A.; Hildreth, W. W.; Richter, J. C.; Rosenkranz, W. A.

1982-01-01

The NASA/JSC ground scatterometer system was used in a row structure and row direction effects experiment to understand these effects on radar remote sensing of soil moisture. Also, a modification of the scatterometer system was begun and is continuing, to allow cross-polarization experiments to be conducted in fiscal years 1982 and 1983. Preprocessing of the 1978 agricultural soil moisture experiment (ASME) data was completed. Preparations for analysis of the ASME data is fiscal year 1982 were completed. A radar image simulation procedure developed by the University of Kansas is being improved. Profile soil moisture model outputs were compared quantitatively for the same soil and climate conditions. A new model was developed and tested to predict the soil moisture characteristic (water tension versus volumetric soil moisture content) from particle-size distribution and bulk density data. Relationships between surface-zone soil moisture, surface flux, and subsurface moisture conditions are being studied as well as the ways in which measured soil moisture (as obtained from remote sensing) can be used for agricultural applications.

Geomorphological characterization of conservation agriculture

NASA Astrophysics Data System (ADS)

Tarolli, Paolo; Cecchin, Marco; Prosdocimi, Massimo; Masin, Roberta

2017-04-01

Soil water erosion is one of the major threats to soil resources throughout the world. Conventional agriculture has worsened the situation. Therefore, agriculture is facing multiple challenges: it has to produce more food to feed a growing population, and, on the other hand, safeguard natural resources adopting more sustainable production practices. In this perspective, more conservation-minded soil management practices should be taken to achieve an environmental sustainability of crop production. Indeed, conservation agriculture is considered to produce relevant environmental positive outcomes (e.g. reducing runoff and soil erosion, improving soil organic matter content and soil structure, and promoting biological activity). However, as mechanical weed control is limited or absent, in conservation agriculture, dependence on herbicides increases especially in the first years of transition from the conventional system. Consequently, also the risk of herbicide losses via runoff or adsorbed to eroded soil particles could be increased. To better analyse the complexity of soil water erosion and runoff processes in landscapes characterised by conservation agriculture, first, it is necessary to demonstrate if such different practices can significantly affect the surface morphology. Indeed, surface processes such erosion and runoff strongly depend on the shape of the surface. The questions are: are the lands treated with conservation and conventional agriculture different from each other regarding surface morphology? If so, can these differences provide a better understanding of hydrogeomorphic processes as the basis for a better and sustainable land management? To give an answer to these questions, we considered six study areas (three cultivated with no-tillage techniques, three with tillage techniques) in an experimental farm. High-resolution topography, derived from low-cost and fast photogrammetric techniques Structure-from-Motion (SfM), served as the basis to characterise the surface morphology. For each of derived Digital Elevation Model, seven morphometric indexes, such as slope, curvature, flow direction, contributing area, roughness, and connectivity was calculated. We showed then the variations of the morphology in the areas converted to the conservation agriculture, and, consequently, a possible modification of processes such as erosion and runoff. The results suggested that the agricultural surfaces interested by no-tillage practices are different from those tilled with conventional systems. The topography is rougher, with chaotic flow directions, and more concave areas, thus resulting in potential water storages, mitigating the intensity of soil erosion and runoff processes. On the other hand, the topography of traditional tillage area is more regular and smooth, with flow directions that tend to follow the same direction on the surface. These results are a novelty in the Earth Science and Agronomy: we demonstrated and quantified, from the geomorphological point of view, the potential role of conservative agriculture in mitigating, not only land degradation phenomena, but also the distribution of pollutants, and rainfall-runoff processes. References Prosdocimi, M., Tarolli, P., Cerdà, A. (2016). Mulching practice for reducing soil water erosion: A review. Earth-Science Reviews, 161, 191-203. Prosdocimi, M., Burguet, M., Di Prima, S., Sofia, G., Terol, E, Rodrigo Comino J., Cerdà, A., Tarolli, P. (2017). Rainfall simulation and Structure-from-Motion photogrammetry for the analysis of soil water erosion in Mediterranean vineyards. Science of the Total Environment, 574, 204-215. Tarolli, P., Sofia G. (2016). Human topographic signatures and derived geomorphic processes across landscapes, Geomorphology, 255, 140-161.

Vertical distribution of the soil microbiota along a successional gradient in a glacier forefield.

PubMed

Rime, Thomas; Hartmann, Martin; Brunner, Ivano; Widmer, Franco; Zeyer, Josef; Frey, Beat

2015-03-01

Spatial patterns of microbial communities have been extensively surveyed in well-developed soils, but few studies investigated the vertical distribution of micro-organisms in newly developed soils after glacier retreat. We used 454-pyrosequencing to assess whether bacterial and fungal community structures differed between stages of soil development (SSD) characterized by an increasing vegetation cover from barren (vegetation cover: 0%/age: 10 years), sparsely vegetated (13%/60 years), transient (60%/80 years) to vegetated (95%/110 years) and depths (surface, 5 and 20 cm) along the Damma glacier forefield (Switzerland). The SSD significantly influenced the bacterial and fungal communities. Based on indicator species analyses, metabolically versatile bacteria (e.g. Geobacter) and psychrophilic yeasts (e.g. Mrakia) characterized the barren soils. Vegetated soils with higher C, N and root biomass consisted of bacteria able to degrade complex organic compounds (e.g. Candidatus Solibacter), lignocellulolytic Ascomycota (e.g. Geoglossum) and ectomycorrhizal Basidiomycota (e.g. Laccaria). Soil depth only influenced bacterial and fungal communities in barren and sparsely vegetated soils. These changes were partly due to more silt and higher soil moisture in the surface. In both soil ages, the surface was characterized by OTUs affiliated to Phormidium and Sphingobacteriales. In lower depths, however, bacterial and fungal communities differed between SSD. Lower depths of sparsely vegetated soils consisted of OTUs affiliated to Acidobacteria and Geoglossum, whereas depths of barren soils were characterized by OTUs related to Gemmatimonadetes. Overall, plant establishment drives the soil microbiota along the successional gradient but does not influence the vertical distribution of microbiota in recently deglaciated soils. © 2014 John Wiley & Sons Ltd.

Exploring functional relationships between post-fire soil water repellency, soil structure and physico-chemical properties

NASA Astrophysics Data System (ADS)

Quarfeld, Jamie; Brook, Anna; Keestra, Saskia; Wittenberg, Lea

2016-04-01

Soil water repellency (WR) and aggregate stability (AS) are two soil properties that are typically modified after burning and impose significant influence on subsequent hydrological and geomorphological dynamics. The response of AS and soil WR to fire depends upon how fire has influenced other key soil properties (e.g. soil OM, mineralogy). Meanwhile, routine thinning of trees and woody vegetation may alter soil properties (e.g. structure and porosity, wettability) by use of heavy machinery and species selection. The study area is situated along a north-facing slope of Mount Carmel national park (Israel). The selected sites are presented as a continuum of management intensity and fire histories. To date, the natural baseline of soil WR has yet to be thoroughly assessed and must be investigated alongside associated soil aggregating parameters in order to understand its overall impact. This study examines (i) the natural baseline of soil WR and physical properties compared to those of disturbed sites in the immediate (controlled burn) and long-term (10-years), and (ii) the interactions of soil properties with different control factors (management, surface cover, seasonal-temporal, burn temperature, soil organic carbon (OC) and mineralogy) in Mediterranean calcareous soils. Analysis of surface soil samples before and after destruction of WR by heating (200-600°C) was implemented using a combination of traditional methods and infrared (IR) spectroscopy. Management and surface cover type conditioned the wettability, soil structure and porosity of soils in the field, although this largely did not affect the heat-induced changes observed in the lab. A positive correlation was observed along an increasing temperature gradient, with relative maxima of MWD and BD reached by most soils at the threshold of 400-500°C. Preliminary analyses of soil OC (MIR) and mineralogical composition (VIS-NIR) support existing research regarding: (i) the importance of soil OC quality and composition in determining wettability rather than quantity, as evidenced both by the high variation observed in the field and the strong presence of aliphatic functional groups in the absence of WR; and (ii) commonly proposed mechanisms affecting soil aggregate properties - albeit with differing temperature thresholds and longer exposure times employed in this study. Namely, these mechanisms tend to involve: (i) soil OM and WR reduction at low to moderate temperatures, and (ii) thermal fusion of particles within moderate to high temperatures. Overall, results suggest a positive influence of management on soil properties as well as high soil resilience to moderate severity fire disturbance in the studied areas. However, the specific changes in soil OM and mineral composition that are responsible for destruction of WR and subsequent changes in AS remain poorly understood. Based on these results, a key next step within this study will entail a closer examination of OC ratios and their potential links with certain mineral species known to influence soil aggregation and soil WR. Noting the importance of soil OM-mineralogical interactions on run-off and erosion processes, results may contribute to better prediction of post-fire responses in the future and improve the ability to fine-tune site specific management approaches accordingly.

Spatial distribution of vanadium and microbial community responses in surface soil of Panzhihua mining and smelting area, China.

PubMed

Cao, Xuelong; Diao, Muhe; Zhang, Baogang; Liu, Hui; Wang, Song; Yang, Meng

2017-09-01

Spatial distribution of vanadium in surface soils from different processing stages of vanadium-bearing titanomagnetite in Panzhihua mining and smelting area (China) as well as responses of microbial communities including bacteria and fungi to vanadium were investigated by fieldwork and laboratory incubation experiment. The vanadium contents in this region ranged from 149.3 to 4793.6 mg kg -1 , exceeding the soil background value of vanadium in China (82 mg kg -1 ) largely. High-throughput DNA sequencing results showed bacterial communities from different manufacturing locations were quite diverse, but Bacteroidetes and Proteobacteria were abundant in all samples. The contents of organic matter, available P, available S and vanadium had great influences on the structures of bacterial communities in soils. Bacterial communities converged to similar structure after long-term (240 d) cultivation with vanadium containing medium, dominating by bacteria which can tolerate or reduce toxicities of heavy metals. Fungal diversities decreased after cultivation, but Ascomycota and Ciliophora were still the most abundant phyla as in the original soil samples. Results in this study emphasize the urgency of investigating vanadium contaminations in soils and provide valuable information on how vanadium contamination influences bacterial and fungal communities. Copyright © 2017 Elsevier Ltd. All rights reserved.

Ferrihydrite in soils

NASA Astrophysics Data System (ADS)

Vodyanitskii, Yu. N.; Shoba, S. A.

2016-07-01

Ferrihydrite—an ephemeral mineral—is the most active Fe-hydroxide in soils. According to modern data, the ferrihydrite structure contains tetrahedral lattice in addition to the main octahedral lattice, with 10-20% of Fe being concentrated in the former. The presence of Fe tetrahedrons influences the surface properties of this mineral. The chemical composition of ferrihydrite samples depends largely on the size of lattice domains ranging from 2 to 6 nm. Chemically pure ferrihydrite rarely occurs in the soil; it usually contains oxyanion (SiO14 4-, PO4 3-) and cation (Al3+) admixtures. Aluminum replace Fe3+ in the structure with a decrease in the mineral particle size. Oxyanions slow down polymerization of Fe3+ aquahydroxomonomers due to the films at the surface of mineral nanoparticles. Si- and Al-ferrihydrites are more resistant to the reductive dissolution than the chemically pure ferrihydrite. In addition, natural ferrihydrite contains organic substance that decreases the grain size of the mineral. External organic ligands favor ferrihydrite dissolution. In the European part of Russia, ferrihydrite is more widespread in the forest soils than in the steppe soils. Poorly crystallized nanoparticles of ferrihydrite adsorb different cations (Zn, Cu) and anions (phosphate, uranyl, arsenate) to immobilize them in soils; therefore, ferrihydrite nanoparticles play a significant role in the biogeochemical cycle of iron and other elements.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kebede, Mulu A.; Bish, David L.; Losovyj, Yaroslav

Nitrous acid (HONO) accumulates in the nocturnal boundary layer where it is an important source of daytime hydroxyl radicals. Although there is clear evidence for the involvement of heterogeneous reactions of NO2 on surfaces as a source of HONO, mechanisms remain poorly understood. We used coated-wall flow tube measurements of NO2 reactivity on environmentally relevant surfaces [Fe (hydr)oxides, clay minerals, and soil from Arizona and the Saharan Desert] and detailed mineralogical characterization of substrates to show that reduction of NO2 by Fe-bearing minerals in soil can be a more important source of HONO than the putative NO2 hydrolysis mechanism. Themore » magnitude of NO2-to-HONO conversion depends on the amount of Fe2+ present in substrates and soil surface acidity. Studies examining the dependence of HONO flux on substrate pH revealed that HONO is formed at soil pH < 5 from the reaction between NO2 and Fe2+(aq) present in thin films of water coating the surface, whereas in the range of pH 5–8 HONO stems from reaction of NO2 with structural iron or surface complexed Fe2+ followed by protonation of nitrite via surface Fe-OH2+ groups. Reduction of NO2 on ubiquitous Fe-bearing minerals in soil may explain HONO accumulation in the nocturnal boundary layer and the enhanced [HONO]/[NO2] ratios observed during dust storms in urban areas.« less

Disturbance Impacts on Thermal Hot Spots and Hot Moments at the Peatland-Atmosphere Interface

NASA Astrophysics Data System (ADS)

Leonard, R. M.; Kettridge, N.; Devito, K. J.; Petrone, R. M.; Mendoza, C. A.; Waddington, J. M.; Krause, S.

2018-01-01

Soil-surface temperature acts as a master variable driving nonlinear terrestrial ecohydrological, biogeochemical, and micrometeorological processes, inducing short-lived or spatially isolated extremes across heterogeneous landscape surfaces. However, subcanopy soil-surface temperatures have been, to date, characterized through isolated, spatially discrete measurements. Using spatially complex forested northern peatlands as an exemplar ecosystem, we explore the high-resolution spatiotemporal thermal behavior of this critical interface and its response to disturbances by using Fiber-Optic Distributed Temperature Sensing. Soil-surface thermal patterning was identified from 1.9 million temperature measurements under undisturbed, trees removed and vascular subcanopy removed conditions. Removing layers of the structurally diverse vegetation canopy not only increased mean temperatures but it shifted the spatial and temporal distribution, range, and longevity of thermal hot spots and hot moments. We argue that linking hot spots and/or hot moments with spatially variable ecosystem processes and feedbacks is key for predicting ecosystem function and resilience.

A soil-landscape framework for understanding spatial and temporal variability in biogeochemical processes in catchments

NASA Astrophysics Data System (ADS)

McGuire, K. J.; Bailey, S. W.; Ross, D. S.

2017-12-01

Heterogeneity in biophysical properties within catchments challenges how we quantify and characterize biogeochemical processes and interpret catchment outputs. Interactions between the spatiotemporal variability of hydrological states and fluxes and soil development can spatially structure catchments, leading to a framework for understanding patterns in biogeochemical processes. In an upland, glaciated landscape at the Hubbard Brook Experimental Forest (HBEF) in New Hampshire, USA, we are embracing the structure and organization of soils to understand the spatial relations between runoff production zones, distinct soil-biogeochemical environments, and solute retention and release. This presentation will use observations from the HBEF to demonstrate that a soil-landscape framework is essential in understanding the spatial and temporal variability of biogeochemical processes in this catchment. Specific examples will include how laterally developed soils reveal the location of active runoff production zones and lead to gradients in primary mineral dissolution and the distribution of weathering products along hillslopes. Soil development patterns also highlight potential carbon and nitrogen cycling hotspots, differentiate acidic conditions, and affect the regulation of surface water quality. Overall, this work demonstrates the importance of understanding the landscape-level structural organization of soils in characterizing the variation and extent of biogeochemical processes that occur in catchments.

Benchmarking NLDAS-2 Soil Moisture and Evapotranspiration to Separate Uncertainty Contributions

NASA Technical Reports Server (NTRS)

Nearing, Grey S.; Mocko, David M.; Peters-Lidard, Christa D.; Kumar, Sujay V.; Xia, Youlong

2016-01-01

Model benchmarking allows us to separate uncertainty in model predictions caused 1 by model inputs from uncertainty due to model structural error. We extend this method with a large-sample approach (using data from multiple field sites) to measure prediction uncertainty caused by errors in (i) forcing data, (ii) model parameters, and (iii) model structure, and use it to compare the efficiency of soil moisture state and evapotranspiration flux predictions made by the four land surface models in the North American Land Data Assimilation System Phase 2 (NLDAS-2). Parameters dominated uncertainty in soil moisture estimates and forcing data dominated uncertainty in evapotranspiration estimates; however, the models themselves used only a fraction of the information available to them. This means that there is significant potential to improve all three components of the NLDAS-2 system. In particular, continued work toward refining the parameter maps and look-up tables, the forcing data measurement and processing, and also the land surface models themselves, has potential to result in improved estimates of surface mass and energy balances.

Benchmarking NLDAS-2 Soil Moisture and Evapotranspiration to Separate Uncertainty Contributions

PubMed Central

Nearing, Grey S.; Mocko, David M.; Peters-Lidard, Christa D.; Kumar, Sujay V.; Xia, Youlong

2018-01-01

Model benchmarking allows us to separate uncertainty in model predictions caused by model inputs from uncertainty due to model structural error. We extend this method with a “large-sample” approach (using data from multiple field sites) to measure prediction uncertainty caused by errors in (i) forcing data, (ii) model parameters, and (iii) model structure, and use it to compare the efficiency of soil moisture state and evapotranspiration flux predictions made by the four land surface models in the North American Land Data Assimilation System Phase 2 (NLDAS-2). Parameters dominated uncertainty in soil moisture estimates and forcing data dominated uncertainty in evapotranspiration estimates; however, the models themselves used only a fraction of the information available to them. This means that there is significant potential to improve all three components of the NLDAS-2 system. In particular, continued work toward refining the parameter maps and look-up tables, the forcing data measurement and processing, and also the land surface models themselves, has potential to result in improved estimates of surface mass and energy balances. PMID:29697706

Benchmarking NLDAS-2 Soil Moisture and Evapotranspiration to Separate Uncertainty Contributions.

PubMed

Nearing, Grey S; Mocko, David M; Peters-Lidard, Christa D; Kumar, Sujay V; Xia, Youlong

2016-03-01

Model benchmarking allows us to separate uncertainty in model predictions caused by model inputs from uncertainty due to model structural error. We extend this method with a "large-sample" approach (using data from multiple field sites) to measure prediction uncertainty caused by errors in (i) forcing data, (ii) model parameters, and (iii) model structure, and use it to compare the efficiency of soil moisture state and evapotranspiration flux predictions made by the four land surface models in the North American Land Data Assimilation System Phase 2 (NLDAS-2). Parameters dominated uncertainty in soil moisture estimates and forcing data dominated uncertainty in evapotranspiration estimates; however, the models themselves used only a fraction of the information available to them. This means that there is significant potential to improve all three components of the NLDAS-2 system. In particular, continued work toward refining the parameter maps and look-up tables, the forcing data measurement and processing, and also the land surface models themselves, has potential to result in improved estimates of surface mass and energy balances.

Faunal Drivers of Soil Flux Dynamics via Alterations in Crack Structure

NASA Astrophysics Data System (ADS)

DeCarlo, Keita; Caylor, Kelly

2016-04-01

Organismal activity, in addition to its role in ecological feedbacks, has the potential to serve as instigators or enhancers of atmospheric and hydrologic processes via alterations in soil structural regimes. We investigated the biomechanical effect of faunal activity on soil carbon dynamics via changes in soil crack structure, focusing on three dryland soil systems: bioturbated, biocompacted and undisturbed soils. Carbon fluxes were characterized using a closed-system respiration chamber, with CO2 concentration differences measured using an infrared gas analyzer (IRGA). Results show that faunal influences play a divergent biomechanics role in bulk soil cracking: bioturbation induced by belowground fauna creates "surficial" (shallow, large, well-connected) networks relative to the "systematic" (deep, moderate, poorly connected) networks created by aboveground fauna. The latter also shows a "memory" of past wetting/drying events in the consolidated soil through a crack layering effect. These morphologies further drive differences in soil carbon flux: under dry conditions, bioturbated and control soils show a persistently high and low mean carbon flux, respectively, while biocompacted soils show a large diurnal trend, with daytime lows and nighttime highs comparable to the control and bioturbated soils, respectively. Overall fluxes under wet conditions are considerably higher, but also more variable, though higher mean fluxes are observed in the biocompacted and bioturbated soils. Our results suggest that the increased surface area in the bioturbated soils create enhanced but constant diffusive processes, whereas the increased thermal gradient in the biocompacted soils create novel convective processes that create high fluxes that are diurnal in nature.

A long-term soil structure observatory for post-compaction soil structure evolution: design and initial soil structure recovery observations

NASA Astrophysics Data System (ADS)

Keller, Thomas; Colombi, Tino; Ruiz, Siul; Grahm, Lina; Reiser, René; Rek, Jan; Oberholzer, Hans-Rudolf; Schymanski, Stanislaus; Walter, Achim; Or, Dani

2016-04-01

Soil compaction due to agricultural vehicular traffic alters the geometrical arrangement of soil constituents, thereby modifying mechanical properties and pore spaces that affect a range of soil hydro-ecological functions. The ecological and economic costs of soil compaction are dependent on the immediate impact on soil functions during the compaction event, and a function of the recovery time. In contrast to a wealth of soil compaction information, mechanisms and rates of soil structure recovery remain largely unknown. A long-term (>10-yr) soil structure observatory (SSO) was established in 2014 on a loamy soil in Zurich, Switzerland, to quantify rates and mechanisms of structure recovery of compacted arable soil under different post-compaction management treatments. We implemented three initial compaction treatments (using a two-axle agricultural vehicle with 8 Mg wheel load): compaction of the entire plot area (i.e. track-by-track), compaction in wheel tracks, and no compaction. After compaction, we implemented four post-compaction soil management systems: bare soil (BS), permanent grass (PG), crop rotation without mechanical loosening (NT), and crop rotation under conventional tillage (CT). BS and PG provide insights into uninterrupted natural processes of soil structure regeneration under reduced (BS) and normal biological activity (PG). The two cropping systems (NT and CT) enable insights into soil structure recovery under common agricultural practices with minimal (NT) and conventional mechanical soil disturbance (CT). Observations include periodic sampling and measurements of soil physical properties, earthworm abundance, crop measures, electrical resistivity and ground penetrating radar imaging, and continuous monitoring of state variables - soil moisture, temperature, CO2 and O2 concentrations, redox potential and oxygen diffusion rates - for which a network of sensors was installed at various depths (0-1 m). Initial compaction increased soil bulk density to about half a metre, decreased gas and water transport functions (air permeability, gas diffusivity, saturated hydraulic conductivity), and increased mechanical impedance. Water infiltration at the soil surface was initially reduced by three orders of magnitude, but significantly recovered within a year. However, within the soil profile, recovery of transport properties is much smaller. Air permeability tended to recover more than gas diffusivity, suggesting that initial post-compaction recovery is initiated by new macropores (e.g. biopores). Tillage recovered topsoil bulk density but not topsoil transport functions. Compaction changed grass species composition in PG, and significantly reduced grass biomass in PG and crop yields in NT and CT.

Effect of the slope and initial moisture content on soil loss, aggregate and particle size distribution

NASA Astrophysics Data System (ADS)

Szabó, Judit Alexandra; Jakab, Gergely; Szabó, Boglárka

2015-04-01

Soil structure degradation has effect through the soil water balance and nutrient supply on the agricultural potential of an area. The soil erosion process comprises two phases: detachment and transport by water. To study the transport phase nozzle type laboratory-scale rainfall simulator was used with constant 80 mmhr-1 intensity on an arable haplic Cambisol. Measuring the aggregate and particle size distribution of the soil loss gives a good approach the erosion process. The primary objective of this study was to examine the sediment concentration, and detect the quality and quantity change of the soil loss during a single precipitation under six treatment combinations (recently tilled and crusty soil surface on two different slope steepness, inland inundation and drought soil conditions). Soil loss were collected continually, and separated per aggregate size fractions with sieves in three rounds during a rain to measure the weights. The particle size distribution was measured with Horiba LA-950 particle size analyzer. In general the ratio of the macro aggregates decreases and the ratio of the micro aggregates and clay fraction increases in the sediment with time during the precipitation due to the raindrop impact. Sediment concentration depends on the slope steepness, as from steeper slopes the runoff can transport bigger amount of sediment, but from the tilled surface bigger aggregates were washing down. Micro aggregate fraction is one of the indicators of good soil structure. The degradation of micro aggregates occurs in steeper slopes and the most erosive time period depends on the micromorphology of the surface. And while the aggregate size distribution of the soil loss of the treatments shows high variety of distribution and differs from the original soil, the particle size distribution of each aggregate size fraction shows similar trends except the 50-250 µm fraction where the fine sand fraction is dominating instead of the loam. This anomaly may be connected with the TC content of this fraction, but more research is needed. In agricultural areas micro aggregate fraction plays important role in nutrient supply thus understanding the erosion process is necessary because of the better protection in the future.

Self-organization, preferential flow and rainfall runoff behavior - is there a connection?

NASA Astrophysics Data System (ADS)

Zehe, Erwin; Blume, Theresa; Kleidon, Axel; Ehret, Uwe; Scherer, Ulrike; Westhoff, Martijn

2013-04-01

In line with the studies of Kleidon et al. (2012) and Zehe et al. (2010) the proposed study analyzes mass flow related flows of free energy in open hydrological systems - hillslopes and small catchments - using thermodynamics methods. Why a thermodynamic treatment? A small part of the kinetic energy input from incoming rainfall is dissipated into heat and to break up soil aggregates. Depending on the partitioning of the incoming rainfall into overland flow and soil water, the remaining part of the incoming kinetic energy is partly transformed into potential energy of surface water and subsequently partly exported as kinetic energy of overland flow from the system; the rest is dissipated by frictional losses. The other part of rainfall infiltrates thereby increasing potential energy of soil water but depleting at the same time (gradients in) capillary binding energy of soil water, which again comprises energy dissipation into heat of immersion. Although, these mass fluxes are not associated with large heat fluxes, they reflect the overall conservation of energy as well as the second law of thermodynamics. They require thus a thermodynamic treatment, because tiny amounts of kinetic energy, surface energy and potential energy are dissipated into heat: this implies irreversibility and explains why water does not flow uphill. Soil hydraulic equilibrium (HE), arising from a balance in potential and capillary binding energy in soil, can be interpreted as a state of maximum entropy in soil. Soil water potential, defined as sum of matric potential and gravity potential, is in HE equal to zero along the soil profile. This corresponds to a state of maximum entropy due to a zero potential gradient, which implies due to Zehe et al. (2010) a state of minimum (Helmholtz) free energy. Our first main objective is to quantify to which extent connected preferential flow path, in our case vertical macropores and the river network enhance flow velocities at a given driving gradient and thus power in the associated mass fluxes. This implies either an enhanced export of free energy in form of kinetic energy in case of the river net, or an accelerated reduction of potential energy of infiltrating surface water which implies a reduction free energy in form of capillary binding energy of soil water. We hypothesize (H1) that network like structures act as dissipative structures "serving the purpose" of reducing the relaxation time to a state of lower "free" energy in the entire system. This is because they minimize dissipative losses of kinetic energy along their extent. This faster relaxation towards a state of smaller free energy is deemed to be favorable for mechanic stability of the entire hydrological system because a) mass flows perform due to the enhanced export of kinetic energy less work on the system itself and b) mechanical stress from ponded surface water is quickly reduced by fast infiltration and preferential flow. Our second main objective is, in line with the study of Zehe et al. (2010), the search for thermodynamic optimal hillslope architectures both with respect to the surface density of vertical macropores in soil and with respect to the spatial arrangement of soil types and macropores at the hillslope scale. In line with H1 we suggest (H2) that a hydro-geo-ecosystem is closer to a functional optimum than other possible configurations if it dissipates and exports more of the kinetic energy input from incoming rainfall by redistributing water against internal gradients and exporting water against macroscale geo-potential gradients. Note that H2 does not postulate that functionally optimal hillslope architectures necessarily exist, if they exist H2 implies however that they maximize entropy production and thus reduction of total free energy of the system at a "wisely" selected time scale. The surface density of apparent macropores does for instance control the tradeoff between Hortonian overland flow formation and infiltration, which implies a tradeoff between the amount of kinetic energy input from rainfall that is converted in to power associated with overland flow and power associated with soil water flows depleting gradients in soil water potential. Does this tradeoff imply an optimum surface density of macropores at the hillslope scale in the sense that power in soil water flow is maximized or reduction of free energy is maximized? In case such an optimum hillslope architecture existed, and in case that the evolution of the hydrological systems of interested was indeed in accordance with hypothesis H2, this optimal architecture should allow an acceptable uncalibrated simulation of the systems rainfall -runoff behavior (if the selected model structure can properly represent this architecture). We will address these questions and test the main implications of our hypotheses by means of numerical experiments with the physically based hydrological model CATFLOW. We use behavioral model structures as basic model setup, which have been shown to closely portray system behavior and its architecture in a sense that they reproduce distributed observations of soil moisture and catchment scale discharge and represent the observed structural and textural signatures of soils, flow networks and vegetation. Our test areas are the Weiherbach (Germany) and the Malalcahuello research headwaters (Chile), which are located in distinctly different hydro-climatic and hydro-pedological settings. Within the numerical experiments we will simulate the full concert of hydrological processes at the hillslope and headwater scales for meaningful perturbations of the behavioral model structure and compare them with respect to dynamics of free energy and production of power. These perturbations affect a) the river network and the geomorphology of the Weiherbach catchment, b) surface density of macropores in both catchments c) the spatial arrangement of soils and preferential pathways at the hillslope scale in the Weiherbach catchment. References: Kleidon, A., Zehe, E., Ehret, U., and Scherer, U.: Thermodynamics, maximum power, and the dynamics of preferential river flow structures on continents, Hydrol. Earth Syst. Sci. Discuss., 9, 7317-7378, 10.5194/hessd-9-7317-2012, 2012. Zehe, E., Blume, T., and Blöschl, G.: The principle of 'maximum energy dissipation': a novel thermodynamic perspective on rapid water flow in connected soil structures, Phil. Trans. R. Soc. B, 1-10, doi:10.1098/rstb.2009.0308, 2010.

Bacterial and enchytraeid abundance accelerate soil carbon turnover along a lowland vegetation gradient in interior Alaska

USGS Publications Warehouse

Waldrop, M.P.; Harden, Jennifer W.; Turetsky, M.R.; Petersen, D.G.; McGuire, A.D.; Briones, M.J.I.; Churchill, A.C.; Doctor, D.H.; Pruett, L.E.

2012-01-01

Boreal wetlands are characterized by a mosaic of plant communities, including forests, shrublands, grasslands, and fens, which are structured largely by changes in topography and water table position. The soil associated with these plant communities contain quantitatively and qualitatively different forms of soil organic matter (SOM) and nutrient availability that drive changes in biogeochemical cycling rates. Therefore different boreal plant communities likely contain different soil biotic communities which in turn affect rates of organic matter decomposition. We examined relationships between plant communities, microbial communities, enchytraeids, and soil C turnover in near-surface soils along a shallow topographic soil moisture and vegetation gradient in interior Alaska. We tested the hypothesis that as soil moisture increases along the gradient, surface soils would become increasingly dominated by bacteria and mesofauna and have more rapid rates of C turnover. We utilized bomb radiocarbon techniques to infer rates of C turnover and the 13C isotopic composition of SOM and respired CO2 to infer the degree of soil humification. Soil phenol oxidase and peroxidase enzyme activities were generally higher in the rich fen compared with the forest and bog birch sites. Results indicated greater C fluxes and more rapid C turnover in the surface soils of the fen sites compared to the wetland forest and shrub sites. Quantitative PCR analyses of soil bacteria and archaea, combined with enchytraeid counts, indicated that surface soils from the lowland fen ecosystems had higher abundances of these microbial and mesofaunal groups. Fungal abundance was highly variable and not significantly different among sites. Microbial data was utilized in a food web model that confirmed that rapidly cycling systems are dominated by bacterial activity and enchytraeid grazing. However, our results also suggest that oxidative enzymes play an important role in the C mineralization process in saturated systems, which has been often ignored.

Influence of soil structure on nutrient cycling using microfluidic techniques

NASA Astrophysics Data System (ADS)

Arellano Caicedo, Carlos; Aleklett, Kristin; Ohlsson, Pelle; Hammer, Edith

2017-04-01

The rising of atmospheric CO2 levels and its effects on global warming make it necessary to understand the elements that regulate such levels and furthermore try to slow down the CO2 accumulation in the atmosphere. The exchange of carbon between soil and atmosphere plays a significant role in the atmospheric carbon budget. Soil organisms deposit organic compounds on and in soil aggregates, either as exudates or dead remains. Much of this dead organic material is quickly recycled, but a portion, however, will stay in the soil for long term. Evidence suggests that micro-scale biogeochemical interactions could play a highly significant role in degradation or persistence of organic matter in soils, thus, soil physical structure might play a decisive role in preventing accessibility of nutrients to microorganisms. For studying effects of spatial microstructure on soil nutrient cycles, we have constructed artificial habitats for microbes that simulate soil structures. Microfluidic, so called Lab-on-a-chip technologies, are one of the tools used to achieve our purpose. Such micro-habitats consist of pillar structures of difference density and surface area, tunnels with increasing depth, and mazes of increasing complexity to simulate different stages of soil aggregation. Using microscopy and analytical chemistry, we can follow the growth of microorganisms inoculated into the "soil chip" as well as the chemical degradation of organic matter compounds provided as nutrient source. In this way, we want to be able to predict how soil structure influences soil microbial activity leading to different effects on the carbon cycle. Our first results of a chip inoculated with natural soil showed a succession of organisms colonizing channels leading to dead-end arenas, starting with a high presence of bacteria inside the chip during the first days. Fungal hyphae growth gradually inside the channels until it finally occupied the big majority of the spaces isolating bacteria which dramatically decreased in number. The structure inside the soil chip changes dynamically due to the creation of biofilms. Such changes alter the spatial distribution inside the chip gradually, to the point of getting significantly different from the original structures. Fungal hyphae, bacterial biofilms, and microbial necro mass accumulation where the components altering the chip structure. These findings suggest that a considerable part of the soil structure is microbial biomass. Using Lab-on-a-chip techniques leads to the creation of a much more realistic soil and ecosystem model, resembling spatial and chemical complexity in real soil structures at a micrometer scale, the scale relevant for soil organisms. Understanding small-scale processes in the soils is crucial to predict carbon and nutrient cycling, and to enable us to give recommendations for soil management in agriculture, horticulture and nature conservation. If parameterization of soil structure as a central determinant for carbon sequestration is possible, it will allow strong argumentation for management practices that conserve and foster soil structure, such as low-tillage, support of mycorrhizal fungi, and reduction of heavy machinery usage.

Microsite and time since prescribed fire's influence on soil microbiology in a pinyon woodland

Treesearch

Benjamin M. Rau; Robert R. Blank; Tye Morgan

2008-01-01

Pinyon-juniper (Pinus monophylla Torr. & Frém.? Juniperus osteosperma Torr.) encroachment into sagebrush grasslands is a continuing problem in the Western United States. Prescribed burning has been suggested to slow woodland encroachment. We examined surface soil microbial community structure using Phospholipid Fatty Acid (PLFA...

Application of ground-penetrating radar imagery for three-dimensional visualisation of near-surface structures in ice-rich permafrost, Barrow, Alaska

USGS Publications Warehouse

Munroe, Jeffrey S.; Doolittle, James A.; Kanevskiy, Mikhail; Hinkel, Kenneth M.; Nelson, Frederick E.; Jones, Benjamin M.; Shur, Yuri; Kimble, John M.

2007-01-01

Three-dimensional ground-penetrating radar (3D GPR) was used to investigate the subsurface structure of ice-wedge polygons and other features of the frozen active layer and near-surface permafrost near Barrow, Alaska. Surveys were conducted at three sites located on landscapes of different geomorphic age. At each site, sediment cores were collected and characterised to aid interpretation of GPR data. At two sites, 3D GPR was able to delineate subsurface ice-wedge networks with high fidelity. Three-dimensional GPR data also revealed a fundamental difference in ice-wedge morphology between these two sites that is consistent with differences in landscape age. At a third site, the combination of two-dimensional and 3D GPR revealed the location of an active frost boil with ataxitic cryostructure. When supplemented by analysis of soil cores, 3D GPR offers considerable potential for imaging, interpreting and 3D mapping of near-surface soil and ice structures in permafrost environments.

Heat transfer and phase transitions of water in multi-layer cryolithozone-surface systems

NASA Astrophysics Data System (ADS)

Khabibullin, I. L.; Nigametyanova, G. A.; Nazmutdinov, F. F.

2018-01-01

A mathematical model for calculating the distribution of temperature and the dynamics of the phase transfor-mations of water in multilayer systems on permafrost-zone surface is proposed. The model allows one to perform calculations in the annual cycle, taking into account the distribution of temperature on the surface in warm and cold seasons. A system involving four layers, a snow or land cover, a top layer of soil, a layer of thermal-insulation materi-al, and a mineral soil, is analyzed. The calculations by the model allow one to choose the optimal thickness and com-position of the layers which would ensure the stability of structures built on the permafrost-zone surface.

Thermal and Hydrologic Signatures of Soil Controls on Evaporation: A Combined Energy and Water Balance Approach with Implications for Remote Sensing of Evaporation

NASA Technical Reports Server (NTRS)

Salvucci, Guido D.

2000-01-01

The overall goal of this research is to examine the feasibility of applying a newly developed diagnostic model of soil water evaporation to large land areas using remotely sensed input parameters. The model estimates the rate of soil evaporation during periods when it is limited by the net transport resulting from competing effects of capillary rise and drainage. The critical soil hydraulic properties are implicitly estimated via the intensity and duration of the first stage (energy limited) evaporation, removing a major obstacle in the remote estimation of evaporation over large areas. This duration, or 'time to drying' (t(sub d)) is revealed through three signatures detectable in time series of remote sensing variables. The first is a break in soil albedo that occurs as a small vapor transmission zone develops near the surface. The second is a break in either surface to air temperature differences or in the diurnal surface temperature range, both of which indicate increased sensible heat flux (and/or storage) required to balance the decrease in latent heat flux. The third is a break in the temporal pattern of near surface soil moisture. Soil moisture tends to decrease rapidly during stage I drying (as water is removed from storage), and then become more or less constant during soil limited, or 'stage II' drying (as water is merely transmitted from deeper soil storage). The research tasks address: (1) improvements in model structure, including extensions to transpiration and aggregation over spatially variable soil and topographic landscape attributes; and (2) applications of the model using remotely sensed input parameters.

Thermal and Hydrologic Signatures of Soil Controls on Evaporation: A Combined Energy and Water Balance Approach with Implications for Remote Sensing of Evaporation

NASA Technical Reports Server (NTRS)

Salvucci, Guido D.

1997-01-01

The overall goal of this research is to examine the feasibility of applying a newly developed diagnostic model of soil water evaporation to large land areas using remotely sensed input parameters. The model estimates the rate of soil evaporation during periods when it is limited by the net transport resulting from competing effects of capillary rise and drainage. The critical soil hydraulic properties are implicitly estimated via the intensity and duration of the first stage (energy limited) evaporation, removing a major obstacle in the remote estimation of evaporation over large areas. This duration, or "time to drying" (t(sub d)), is revealed through three signatures detectable in time series of remote sensing variables. The first is a break in soil albedo that occurs as a small vapor transmission zone develops near the surface. The second is a break in either surface to air temperature differences or in the diurnal surface temperature range, both of which indicate increased sensible heat flux (and/or storage) required to balance the decrease in latent heat flux. The third is a break in the temporal pattern of near surface soil moisture. Soil moisture tends to decrease rapidly during stage 1 drying (as water is removed from storage), and then become more or less constant during soil limited, or "stage 2" drying (as water is merely transmitted from deeper soil storage). The research tasks address: (1) improvements in model structure, including extensions to transpiration and aggregation over spatially variable soil and topographic landscape attributes; and (2) applications of the model using remotely sensed input parameters.

Small-scale barriers mitigate desertification processes and enhance plant recruitment in a degraded semiarid grassland

USGS Publications Warehouse

Fick, Stephen E; Decker, Cheryl E.; Duniway, Michael C.; Miller, Mark E.

2016-01-01

Anthropogenic desertification is a problem that plagues drylands globally; however, the factors which maintain degraded states are often unclear. In Canyonlands National Park on the Colorado Plateau of southeastern Utah, many degraded grasslands have not recovered structure and function >40 yr after release from livestock grazing pressure, necessitating active restoration. We hypothesized that multiple factors contribute to the persistent degraded state, including lack of seed availability, surficial soil-hydrological properties, and high levels of spatial connectivity (lack of perennial vegetation and other surface structure to retain water, litter, seed, and sediment). In combination with seeding and surface raking treatments, we tested the effect of small barrier structures (“ConMods”) designed to disrupt the loss of litter, seed and sediment in degraded soil patches within the park. Grass establishment was highest when all treatments (structures, seed addition, and soil disturbance) were combined, but only in the second year after installation, following favorable climatic conditions. We suggest that multiple limiting factors were ameliorated by treatments, including seed limitation and microsite availability, seed removal by harvester ants, and stressful abiotic conditions. Higher densities of grass seedlings on the north and east sides of barrier structures following the summer months suggest that structures may have functioned as artificial “nurse-plants”, sheltering seedlings from wind and radiation as well as accumulating wind-blown resources. Barrier structures increased the establishment of both native perennial grasses and exotic annuals, although there were species-specific differences in mortality related to spatial distribution of seedlings within barrier structures. The unique success of all treatments combined, and even then only under favorable climatic conditions and in certain soil patches, highlights that restoration success (and potentially, natural regeneration) often is contingent on many interacting factors.

Biological soil crust and disturbance controls on surface hydrology in a semi-arid ecosystem

USGS Publications Warehouse

Faist, Akasha M; Herrick, Jeffrey E.; Belnap, Jayne; Van Zee, Justin W; Barger, Nichole N

2017-01-01

Biological soil crust communities (biocrusts) play an important role in surface hydrologic processes in dryland ecosystems, and these processes may then be dramatically altered with soil surface disturbance. In this study, we examined biocrust hydrologic responses to disturbance at different developmental stages on sandy soils on the Colorado Plateau. Our results showed that all disturbance (trampling, scalping and trampling+scalping) of the early successional light cyanobacterial biocrusts generally reduced runoff. In contrast, trampling well-developed dark-cyano-lichen biocrusts increased runoff and sediment loss relative to intact controls. Scalping did not increase runoff, implying that soil aggregate structure was important to the infiltration process. Well-developed, intact dark biocrusts generally had lower runoff, low sediment loss, and highest aggregate stability whereas the less-developed light biocrusts were highest in runoff and sediment loss when compared to the controls. These results suggest the importance of maintaining the well-developed dark biocrusts, as they are beneficial for lowering runoff and reducing soil loss and redistribution on the landscape. These data also suggest that upslope patches of light biocrust may either support water transport to downslope vegetation patches or alternatively this runoff may place dark biocrust patches at risk of disruption and loss, given that light patches increase runoff and thus soil erosion potential.

Uncertainty in Ecohydrological Modeling in an Arid Region Determined with Bayesian Methods

PubMed Central

Yang, Junjun; He, Zhibin; Du, Jun; Chen, Longfei; Zhu, Xi

2016-01-01

In arid regions, water resources are a key forcing factor in ecosystem circulation, and soil moisture is the critical link that constrains plant and animal life on the soil surface and underground. Simulation of soil moisture in arid ecosystems is inherently difficult due to high variability. We assessed the applicability of the process-oriented CoupModel for forecasting of soil water relations in arid regions. We used vertical soil moisture profiling for model calibration. We determined that model-structural uncertainty constituted the largest error; the model did not capture the extremes of low soil moisture in the desert-oasis ecotone (DOE), particularly below 40 cm soil depth. Our results showed that total uncertainty in soil moisture prediction was improved when input and output data, parameter value array, and structure errors were characterized explicitly. Bayesian analysis was applied with prior information to reduce uncertainty. The need to provide independent descriptions of uncertainty analysis (UA) in the input and output data was demonstrated. Application of soil moisture simulation in arid regions will be useful for dune-stabilization and revegetation efforts in the DOE. PMID:26963523

High Throughput Sequencing to Detect Differences in Methanotrophic Methylococcaceae and Methylocystaceae in Surface Peat, Forest Soil, and Sphagnum Moss in Cranesville Swamp Preserve, West Virginia, USA

PubMed Central

Lau, Evan; Nolan, Edward J.; Dillard, Zachary W.; Dague, Ryan D.; Semple, Amanda L.; Wentzell, Wendi L.

2015-01-01

Northern temperate forest soils and Sphagnum-dominated peatlands are a major source and sink of methane. In these ecosystems, methane is mainly oxidized by aerobic methanotrophic bacteria, which are typically found in aerated forest soils, surface peat, and Sphagnum moss. We contrasted methanotrophic bacterial diversity and abundances from the (i) organic horizon of forest soil; (ii) surface peat; and (iii) submerged Sphagnum moss from Cranesville Swamp Preserve, West Virginia, using multiplex sequencing of bacterial 16S rRNA (V3 region) gene amplicons. From ~1 million reads, >50,000 unique OTUs (Operational Taxonomic Units), 29 and 34 unique sequences were detected in the Methylococcaceae and Methylocystaceae, respectively, and 24 potential methanotrophs in the Beijerinckiaceae were also identified. Methylacidiphilum-like methanotrophs were not detected. Proteobacterial methanotrophic bacteria constitute <2% of microbiota in these environments, with the Methylocystaceae one to two orders of magnitude more abundant than the Methylococcaceae in all environments sampled. The Methylococcaceae are also less diverse in forest soil compared to the other two habitats. Nonmetric multidimensional scaling analyses indicated that the majority of methanotrophs from the Methylococcaceae and Methylocystaceae tend to occur in one habitat only (peat or Sphagnum moss) or co-occurred in both Sphagnum moss and peat. This study provides insights into the structure of methanotrophic communities in relationship to habitat type, and suggests that peat and Sphagnum moss can influence methanotroph community structure and biogeography. PMID:27682082

The herbicide glyphosate and its metabolite AMPA in the Lavaux vineyard area, western Switzerland: proof of widespread export to surface waters. Part II: the role of infiltration and surface runoff.

PubMed

Daouk, Silwan; De Alencastro, Luiz F; Pfeifer, Hans-Rudolf

2013-01-01

Two parcels of the Lavaux vineyard area, western Switzerland, were studied to assess to which extent the widely used herbicide, glyphosate, and its metabolite aminomethylphosphonic acid (AMPA) were retained in the soil or exported to surface waters. They were equipped at their bottom with porous ceramic cups and runoff collectors, which allowed retrieving water samples for the growing seasons 2010 and 2011. The role of slope, soil properties and rainfall regime in their export was examined and the surface runoff/throughflows ratio was determined with a mass balance. Our results revealed elevated glyphosate and AMPA concentrations at 60 and 80 cm depth at parcel bottoms, suggesting their infiltration in the upper parts of the parcels and the presence of preferential flows in the studied parcels. Indeed, the succession of rainy days induced the gradual saturation of the soil porosity, leading to rapid infiltration through macropores, as well as surface runoff formation. Furthermore, the presence of more impervious weathered marls at 100 cm depth induced throughflows, the importance of which in the lateral transport of the herbicide molecules was determined by the slope steepness. Mobility of glyphosate and AMPA into the unsaturated zone was thus likely driven by precipitation regime and soil characteristics, such as slope, porosity structure and layer permeability discrepancy. Important rainfall events (>10 mm/day) were clearly exporting molecules from the soil top layer, as indicated by important concentrations in runoff samples. The mass balance showed that total loss (10-20%) mainly occurred through surface runoff (96%) and, to a minor extent, by throughflows in soils (4%), with subsequent exfiltration to surface waters.

Loss of surface horizon of an irrigated soil detected by radiometric images of normalized difference vegetation index.

NASA Astrophysics Data System (ADS)

Fabian Sallesses, Leonardo; Aparicio, Virginia Carolina; Costa, Jose Luis

2017-04-01

The use of the soil in the Humid Pampa of Argentina has changed since the mid-1990s from agricultural-livestock production (that included pastures with direct grazing) to a purely agricultural production. Also, in recent years the area under irrigation by central pivot has been increased to 150%. The waters used for irrigation are sodium carbonates. The combination of irrigation and rain increases the sodium absorption ratio of soil (SARs), consequently raising the clay dispersion and reducing infiltration. This implies an increased risk of soil loss. A reduction in the development of white clover crop (Trifolium repens L.) was observed at an irrigation plot during 2015 campaign. The clover was planted in order to reduce the impact of two maize (Zea mays L.) campaigns under irrigation, which had increased soil SAR and deteriorated soil structure. SPOT-5 radiometric normalized difference vegetation index (NDVI) images were used to determine two zones of high and low production. In each zone, four random points were selected for further geo-referenced field sampling. Two geo-referenced measures of effective depth and surface soil sampling were carried out in each point. Texture of soil samples was determined by Pipette Method of Sedimentation Analysis. Data exploratory analysis showed that low production zone had a media effective depth = 80 cm and silty clay loam texture, while high production zone had a media effective depth > 140 cm and silt loam texture. The texture class of the low production zone did not correspond to prior soil studies carried out by the INTA (National Institute of Agricultural Technology), which showed that those soil textures were silt loam at surface and silty clay loam at sub-surface. The loss of the A horizon is proposed as a possible explanation, but further research is required. Besides, the need of a soil cartography actualization, which integrates new satellite imaging technologies and geo-referenced measurements with soil sensors is emphasized. Key words: soil use change, satellite images, erosion.

Application of the two-source energy balance model to partition evapotranspiration in an arid wine vineyard

NASA Astrophysics Data System (ADS)

Kool, Dilia; Kustas, William P.; Agam, Nurit

2016-04-01

The partitioning of evapotranspiration (ET) into transpiration (T), a productive water use, and soil water evaporation (E), which is generally considered a water loss, is highly relevant to agriculture in the light of increasing desertification and water scarcity. This task is challenged by the complexity of soil and plant interactions, coupled with changes in atmospheric and soil water content conditions. Many of the processes controlling water/energy exchange are not adequately modeled. The two-source energy balance model (TSEB) was evaluated and adapted for independent E and T estimations in an isolated drip-irrigated wine vineyard in the arid Negev desert. The TSEB model estimates ET by computing vegetation and soil energy fluxes using remotely sensed composite surface temperature, local weather data (solar radiation, air temperature and humidity, and wind speed), and vegetation metrics (row spacing, canopy height and width, and leaf area). The soil and vegetation energy fluxes are computed numerically using a system of temperature gradient and resistance equations; where soil and canopy temperatures are derived from the composite surface temperature. For estimation of ET, the TSEB model has been shown to perform well for various agricultural crops under a wide range of environmental conditions, but validation of T and E fluxes is limited to one study in a well-watered cotton crop. Extending the TSEB approach to water-limited vineyards demands careful consideration regarding how the complex canopy structure of vineyards will influence the accuracy of the partitioning between E and T. Data for evaluation of the TSEB model were collected over a season (bud break till harvest). Composite, canopy, and soil surface temperatures were measured using infrared thermometers. The composite vegetation and soil surface energy fluxes were assessed using independent measurements of net radiation, and soil, sensible and latent heat flux. The below canopy energy balance was assessed at the dry midrow position as well as the wet irrigated position directly underneath the vine row, where net radiation and soil heat flux were measured, sensible heat flux was computed indirectly, and E was calculated as the residual. While the below canopy energy balance approach used in this study allowed continuous assessment of E at daily intervals, instantaneous E fluxes could not be assessed due to vertical variability in shading below the canopy. Seasonal partitioning indicated that total E amounted to 9-11% of ET. Initial evaluation of the TSEB model indicated that discrepancies between modeled and measured fluxes can largely be attributed to net radiation partitioning. In addition, large diurnal variation at the soil surface requires adaptation of the soil heat flux formulations. Improved estimation of energy fluxes by accounting for the relatively complex canopy structure of vineyards will be highlighted.

Spatial arrangement of organic compounds on a model mineral surface: implications for soil organic matter stabilization.

PubMed

Petridis, Loukas; Ambaye, Haile; Jagadamma, Sindhu; Kilbey, S Michael; Lokitz, Bradley S; Lauter, Valeria; Mayes, Melanie A

2014-01-01

The complexity of the mineral-organic carbon interface may influence the extent of stabilization of organic carbon compounds in soils, which is important for global climate futures. The nanoscale structure of a model interface was examined here by depositing films of organic carbon compounds of contrasting chemical character, hydrophilic glucose and amphiphilic stearic acid, onto a soil mineral analogue (Al2O3). Neutron reflectometry, a technique which provides depth-sensitive insight into the organization of the thin films, indicates that glucose molecules reside in a layer between Al2O3 and stearic acid, a result that was verified by water contact angle measurements. Molecular dynamics simulations reveal the thermodynamic driving force behind glucose partitioning on the mineral interface: The entropic penalty of confining the less mobile glucose on the mineral surface is lower than for stearic acid. The fundamental information obtained here helps rationalize how complex arrangements of organic carbon on soil mineral surfaces may arise.

Nematode community structure in a vineyard soil.

PubMed

Ferris, H; McKenry, M V

1976-04-01

Distribution of the nematode community in a California vineyard was studied over a 13-month period. Omnivorous and microbivorous nematodes were similarly distributed in the root zone, with greatest densities occurring between vine rows and near the soil surface. Greatest densities of plant-parasitic nematodes were found in the vine row, with the individual species differing in their vertical distribution. Total nematode biomass was greatest between rows near the surface. Biomass of plant parasites was greatest in the upper 30 cm of soil in the row, whereas biomass of microbivores was greatest in this region between rows. Of the plant-parasitic nematodes, the variability in distribution among vines was greatest for Paratylenchus hamatus and least for Meloidogyne spp.

Organochlorines in surface soil at electronic-waste wire burning sites and metal contribution evaluated using quantitative X-ray speciation

NASA Astrophysics Data System (ADS)

Fujimori, Takashi; Takigami, Hidetaka; Takaoka, Masaki

2013-04-01

Heavy metals and toxic chlorinated aromatic compounds (aromatic-Cls) such as dioxins and polychlorinated biphenyls (PCBs) are found at high concentrations and persist in surface soil at wire burning sites (WBSs) in developing countries in which various wire cables are recycled to yield pure metals. Chlorine K-edge near-edge X-ray absorption fine structure (NEXAFS) is used to detect the specific chemical form of Cl and estimate its amount using a spectrum jump in the solid phase. Quantitative X-ray speciation of Cl was applied to study the mechanisms of aromatic-Cls formation in surface soil at WBSs in Southeast Asia. Relationships between aromatic-Cls and chlorides of heavy metals were evaluated because heavy metals are promoters of the thermochemical solid-phase formation of aromatic-Cls.

Linking crop structure, throughfall, soil surface conditions, runoff and soil detachment: 10 land uses analyzed in Northern Laos.

PubMed

Lacombe, Guillaume; Valentin, Christian; Sounyafong, Phabvilay; de Rouw, Anneke; Soulileuth, Bounsamai; Silvera, Norbert; Pierret, Alain; Sengtaheuanghoung, Oloth; Ribolzi, Olivier

2018-03-01

In Montane Southeast Asia, deforestation and unsuitable combinations of crops and agricultural practices degrade soils at an unprecedented rate. Typically, smallholder farmers gain income from "available" land by replacing fallow or secondary forest by perennial crops. We aimed to understand how these practices increase or reduce soil erosion. Ten land uses were monitored in Northern Laos during the 2015 monsoon, using local farmers' fields. Experiments included plots of the conventional system (food crops and fallow), and land uses corresponding to new market opportunities (e.g. commercial tree plantations). Land uses were characterized by measuring plant cover and plant mean height per vegetation layer. Recorded meteorological variables included rainfall intensity, throughfall amount, throughfall kinetic energy (TKE), and raindrop size. Runoff coefficient, soil loss, and the percentage areas of soil surface types (free aggregates and gravel; crusts; macro-faunal, vegetal and pedestal features; plant litter) were derived from observations and measurements in 1-m 2 micro-plots. Relationships between these variables were explored with multiple regression analyses. Our results indicate that TKE induces soil crusting and soil loss. By reducing rainfall infiltration, crusted area enhances runoff, which removes and transports soil particles detached by splash over non-crusted areas. TKE is lower under land uses reducing the velocity of raindrops and/or preventing an increase in their size. Optimal vegetation structures combine minimum height of the lowest layer (to reduce drop velocity at ground level) and maximum coverage (to intercept the largest amount of rainfall), as exemplified by broom grass (Thysanolaena latifolia). In contrast, high canopies with large leaves will increase TKE by enlarging raindrops, as exemplified by teak trees (Tectona grandis), unless a protective understorey exists under the trees. Policies that ban the burning of multi-layered vegetation structure under tree plantations should be enforced. Shade-tolerant shrubs and grasses with potential economic return could be promoted as understorey. Copyright © 2017 Elsevier B.V. All rights reserved.

Utilising Structure-From-Motion Approaches to Develop a Spatial Understanding of Soil Erosion Processes, in an Experimental Setting.

NASA Astrophysics Data System (ADS)

Benaud, P.; Anderson, K.; Quine, T. A.; James, M. R.; Quinton, J.; Brazier, R. E.

2016-12-01

While total sediment capture can accurately quantify soil loss via water erosion, it isn't practical at the field scale and provides little information on the spatial nature of soil erosion processes. Consequently, high-resolution, remote sensing, point cloud data provide an alternative method for quantifying soil loss. The accessibility of Structure-from-Motion Multi-Stereo View (SfM) and the potential for multi-temporal applications, offers an exciting opportunity to spatially quantify soil erosion. Accordingly, published research provides examples of the successful quantification of large erosion features and events, to centimetre accuracy. Through rigorous control of the camera and image network geometry, the centimetre accuracy achievable at the field scale, can translate to sub-millimetre accuracies within a laboratory environment. Accordingly, this study looks to understand how the ultra-high-resolution spatial information on soil surface topography, derived from SfM, can be integrated with a multi-element sediment tracer to develop a mechanistic understanding of rill and inter-rill erosion, under experimental conditions. A rainfall simulator was used to create three soil surface conditions; compaction and rainsplash, inter-rill erosion, and rill erosion, at two experimental scales (0.15 m2 and 3 m2). Total sediment capture was the primary validation for the experiments, allowing the comparison between structurally and volumetrically derived change, and true soil loss. A Terrestrial Laser Scanner (resolution of ca. 0.8mm) has been employed to assess spatial discrepancies within the SfM data sets and to provide an alternative measure of volumetric change. Preliminary results show the SfM approach used can achieve a ground resolution of less than 0.2 mm per pixel, and a RMSE of less than 0.3 mm. Consequently, it is expected that the ultra-high-resolution SfM point clouds can be utilised to provide a detailed assessment of soil loss via water erosion processes.

Demonstration and Validation of Controlled Low-Strength Materials for Corrosion Mitigation of Buried Steel Pipes: Final Report on Project F09-A17

DTIC Science & Technology

2015-12-01

steel surfaces. Two different CLSM blends were tested. Both used cement and a flowability admixture, but one used native soil instead of standard...by about 63% in the soil cement . Therefore, CLSMs can reduce the cost of applying CP to buried steel structures. The return-on-investment ratio for...was exposed in the native-soil backfill to deter- mine the corrosion rate in the absence of any flowable fill or soil cement . The removable steel

Transport and fate of estrogenic hormones in slurry-treated soil monoliths.

PubMed

Laegdsmand, Mette; Andersen, Henrik; Jacobsen, Ole Hørbye; Halling-Sørensen, Bent

2009-01-01

The naturally occurring hormones, such as 17-beta-estradiol, 17-alpha-estradiol, and estrone, present in livestock manure may have detrimental environmental effects if released into surface waters. In areas where manure application is intensive, estrogens have been found in surface waters in concentrations known to affect the endocrine system of fish and amphibians. How the estrogens reach the surface waters is unclear. To investigate whether leaching through the soil profile plays a significant role, we conducted leaching experiments on intact soil cores. Lysimeter soil monoliths (60 cm in diameter and 100 cm long) were excavated from two sites in Denmark (one loamy and one sandy soil). The soil monoliths were treated with pig slurry containing estrogenic hormones and amended with an estrogen tracer (17-alpha-ethinylestradiol) and a conservative tracer (bromide). 17-alpha-ethinylestradiol is a synthetic analog of 17-beta-estradiol with sorption characteristics and molecular structure similar to those of the naturally occurring estrogens in slurry. The monoliths were exposed to a short-term irrigation event (12 h) followed by a long-term semi-field experiment (16 wk), during which leaching of natural estrogens and tracers was followed. Estrogens from slurry were transported to a depth of 1 m in loamy soil and sandy soil. The estrogen concentrations in the leachate were at a level known to affect the endocrine system of aquatic organisms.

National Dam Safety Program. Structure F-1 (MO 20512), Verdigris - Neosho River Basin, Newton County, Missouri. Phase I Inspection Report.

DTIC Science & Technology

1980-08-01

soil series. These soils generally make good fill material when properly compacted. The "Geologic Map ot Missouri" indicates that two known faults run in...appurtenant structures, reser- voir, and downstream features are presented in Appendix D. B. Dam: The dam appears to be in good condition. No sloughing...or sliding of the embankment was noted. The horizontal and vertical alignments of the crest were good , and no surfacing cracking or unusual movement

Temperature sensitivity of gaseous elemental mercury in the active layer of the Qinghai-Tibet Plateau permafrost.

PubMed

Ci, Zhijia; Peng, Fei; Xue, Xian; Zhang, Xiaoshan

2018-07-01

Soils represent the single largest mercury (Hg) reservoir in the global environment, indicating that a tiny change of Hg behavior in soil ecosystem could greatly affect the global Hg cycle. Climate warming is strongly altering the structure and functions of permafrost and then would influence the Hg cycle in permafrost soils. However, Hg biogeochemistry in climate-sensitive permafrost is poorly investigated. Here we report a data set of soil Hg (0) concentrations in four different depths of the active layer in the Qinghai-Tibet Plateau permafrost. We find that soil Hg (0) concentrations exhibited a strongly positive and exponential relationship with temperature and showed different temperature sensitivity under the frozen and unfrozen condition. We conservatively estimate that temperature increases following latest temperature scenarios of the IPCC could result in up to a 54.9% increase in Hg (0) concentrations in surface permafrost soils by 2100. Combining the simultaneous measurement of air-soil Hg (0) exchange, we find that enhanced Hg (0) concentrations in upper soils could favor Hg (0) emissions from surface soil. Our findings indicate that Hg (0) emission could be stimulated by permafrost thawing in a warmer world. Copyright © 2018 Elsevier Ltd. All rights reserved.

Towards an improved soil moisture retrieval for organic-rich soils from SMOS passive microwave L-band observations

NASA Astrophysics Data System (ADS)

Bircher, Simone; Richaume, Philippe; Mahmoodi, Ali; Mialon, Arnaud; Fernandez-Moran, Roberto; Wigneron, Jean-Pierre; Demontoux, François; Jonard, François; Weihermüller, Lutz; Andreasen, Mie; Rautiainen, Kimmo; Ikonen, Jaakko; Schwank, Mike; Drusch, Mattias; Kerr, Yann H.

2017-04-01

From the passive L-band microwave radiometer onboard the Soil Moisture and Ocean Salinity (SMOS) space mission global surface soil moisture data is retrieved every 2 - 3 days. Thus far, the empirical L-band Microwave Emission of the Biosphere (L-MEB) radiative transfer model applied in the SMOS soil moisture retrieval algorithm is exclusively calibrated over test sites in dry and temperate climate zones. Furthermore, the included dielectric mixing model relating soil moisture to relative permittivity accounts only for mineral soils. However, soil moisture monitoring over the higher Northern latitudes is crucial since these regions are especially sensitive to climate change. A considerable positive feedback is expected if thawing of these extremely organic soils supports carbon decomposition and release to the atmosphere. Due to differing structural characteristics and thus varying bound water fractions, the relative permittivity of organic material is lower than that of the most mineral soils at a given water content. This assumption was verified by means of L-band relative permittivity laboratory measurements of organic and mineral substrates from various sites in Denmark, Finland, Scotland and Siberia using a resonant cavity. Based on these data, a simple empirical dielectric model for organic soils was derived and implemented in the SMOS Soil Moisture Level 2 Prototype Processor (SML2PP). Unfortunately, the current SMOS retrieved soil moisture product seems to show unrealistically low values compared to in situ soil moisture data collected from organic surface layers in North America, Europe and the Tibetan Plateau so that the impact of the dielectric model for organic soils cannot really be tested. A simplified SMOS processing scheme yielding higher soil moisture levels has recently been proposed and is presently under investigation. Furthermore, recalibration of the model parameters accounting for vegetation and roughness effects that were thus far only evaluated using the default dielectric model for mineral soils is ongoing for the "organic" L-MEB version. Additionally, in order to decide where a soil moisture retrieval using the "organic" dielectric model should be triggered, information on soil organic matter content in the soil surface layer has to be considered in the retrieval algorithm. For this purpose, SoilGrids (www.soilgrids.org) providing soil organic carbon content (SOCC) in g/kg is under study. A SOCC threshold based on the relation between the SoilGrids' SOCC and the presence of organic soil surface layers (relevant to alter the microwave L-band emissions from the land surface) in the SoilGrids' source soil profile information has to be established. In this communication, we present the current status of the above outlined studies with the objective to advance towards an improved soil moisture retrieval for organic-rich soils from SMOS passive microwave L-band observations.

Characterization of soil phosphorus in a fire-affected forest Cambisol by chemical extractions and (31)P-NMR spectroscopy analysis.

PubMed

Turrion, María-Belén; Lafuente, Francisco; Aroca, María-José; López, Olga; Mulas, Rafael; Ruipérez, Cesar

2010-07-15

This study was conducted to investigate the long-term effects of fire on soil phosphorus (P) and to determine the efficiency of different procedures in extracting soil P forms. Different P forms were determined: labile forms (Olsen-P, Bray-P, and P extracted by anion exchange membranes: AEM-P); moderately labile inorganic and organic P, obtained by NaOH-EDTA extraction after removing the AEM-P fraction; and total organic and inorganic soil P. (31)P-NMR spectroscopy was used to characterize the structure of alkali-soluble P forms (orthophosphate, monoester, pyrophosphate, and DNA). The studied area was a Pinus pinaster forest located at Arenas de San Pedro (southern Avila, Spain). The soils were Dystric Cambisols over granites. Soil samples were collected at 0-2 cm, 2-5 cm, and 10-15 cm depths, two years after a fire in the burned area and in an adjacent unburned forest area. Fire increased the total N, organic C, total P, and organic and inorganic P content in the surface soil layer. In burned soil, the P extracted by the sequential procedure (AEM and NaOH+EDTA) was about 95% of the total P. Bray extraction revealed a fire-induced increase in the sorption surfaces. Analysis by chemical methods overestimated the organic P fraction in the EDTA-NaOH extract in comparison with the determination by ignition procedure. This overestimation was more important in the burned than unburned soil samples, probably due to humification promoted by burning, which increased P sorption by soil particles. The fire-induced changes on the structure of alkali-soluble P were an increase in orthophosphate-P and a decrease in monoester-P and DNA-P. Copyright 2010 Elsevier B.V. All rights reserved.

Links between nanoscale and macroscale surface properties of natural root mucilage studied by atomic force microscopy and contact angle.

PubMed

Kaltenbach, Robin; Diehl, Dörte; Schaumann, Gabriele E

2018-04-15

Soil water repellency originating from organic coatings plays a crucial role for soil hydraulics and plant water uptake. Focussing on hydrophobicity in the rhizosphere induced by root-mucilage, this study aims to explore the link between macroscopic wettability and nano-microscopic surface properties. The existing knowledge of the nanostructures of organic soil compounds and its effect on wettability is limited by the lack of a method capable to assess the natural spatial heterogeneity of physical and chemical properties. In this contribution, this task is tackled by a geostatistical approach via variogram analysis of topography and adhesion force data acquired by atomic force microscopy and macroscopic sessile drop measurements on dried films of mucilage. The results are discussed following the wetting models given by Wenzel and Cassie-Baxter. Undiluted mucilage formed homogeneous films on the substrate with contact angles >90°. For diluted samples contact angles were smaller and incomplete mucilage surface coverage with hole-like structures frequently exhibited increased adhesion forces. Break-free distances of force curves indicated enhanced capillary forces due to adsorbed water films at atmospheric RH (35 ± 2%) that promote wettability. Variogram analysis enabled a description of complex surface structures exceeding the capability of comparative visual inspection. Copyright © 2018 Elsevier Inc. All rights reserved.

Effect of stone coverage on soil erosion

NASA Astrophysics Data System (ADS)

Jomaa, S.; Barry, D. A.; Heng, B. P.; Brovelli, A.; Sander, G. C.; Parlange, J.

2010-12-01

Soil surface coverage has a significant impact on water infiltration, runoff and soil erosion yields. In particular, surface stones protect the soils from raindrop detachment, they retard the overland flow therefore decreasing its sediment transport capacity, and they prevent surface sealing. Several physical and environmental factors control to what extent stones on the soil surface modify the erosion rates and the related hydrological response. Among the most important factors are the moisture content of the topsoil, stone size, emplacement, coverage density and soil texture. Owing to the different inter-related processes, there is ambiguity concerning the quantitative effect of stones, and process-based understanding is limited. Experiments were performed (i) to quantify how stone features affect sediment yields, (ii) to understand the local effect of isolated surface stones, that is, the changes of the soil particle size distribution in the vicinity of a stone and (iii) to determine how stones attenuate the development of surface sealing and in turn how this affects the local infiltration rate. A series of experiments using the EPFL 6-m × 2-m erosion flume were conducted at different rainfall intensities (28 and 74 mm h-1) and stone coverage (20 and 40%). The total sediment concentration, the concentration of the individual size classes and the flow discharge were measured. In order to analyze the measurements, the Hairsine and Rose (HR) erosion model was adapted to account for the shielding effect of the stone cover. This was done by suitably adjusting the parameters based on the area not covered by stones. It was found that the modified HR model predictions agreed well with the measured sediment concentrations especially for the long time behavior. Changes in the bulk density of the topsoil due to raindrop-induced compaction with and without stone protection revealed that the stones protect the upper soil surface against the structural seals resulting in negligible changes in the bulk density during the erosion event. Since the main process contributing to surface sealing development is the compaction due to the raindrop kinetic energy and associated physico-chemical changes, the protection provided by the stone cover is consistent with the area-averaging approach used in applying the HR model.

Modeling the surface and interior structure of comet nuclei using a multidisciplinary approach

NASA Technical Reports Server (NTRS)

Odell, C. R.; Dakoulas, Panos C.; Pharr, George M.

1991-01-01

The goal was to investigate the structural properties of the surface of comet nucleus and how the surface should change with time under effect of solar radiation. The basic model that was adopted was that the nucleus is an aggregate of frosty particles loosely bound together, so that it is essentially a soil. The nucleus must mostly be composed of dust particles. The observed mass ratios of dust to gas in the coma is never much greater than unity, but this ratio is probably a much lower limit than that of the nucleus because it is vastly easier to remove the gaseous component by sublimation than by carrying off the dust. Therefore the described models assumed that the particles in the soil were frost covered grains of submicron basic size, closely resembling the interstellar grains. The surface properties of such a nucleus under the effects of heating and cooling as the nucleus approaches and recedes from the Sun generally characterized.

Surface Runoff of Pesticides from a Clay Loam Field in Sweden.

PubMed

Larsbo, Mats; Sandin, Maria; Jarvis, Nick; Etana, Ararso; Kreuger, Jenny

2016-07-01

Pesticides stored at or close to the soil surface after field application can be mobilized and transported off the field when surface runoff occurs. The objective of our study was to quantify the potential pesticide losses in surface runoff from a conventionally managed agricultural field in a Swedish climate. This was achieved by measuring surface runoff volumes and concentrations in runoff of six spring-applied pesticides and autumn-applied glyphosate and its metabolite aminomethylphosphonic acid (AMPA). Measurements were performed for 3 yr both during the growing seasons and during intervening winter snowmelt periods on a clay loam field close to Uppsala. During growing seasons, surface runoff was generated on only five occasions during one 25-d period in 2012 when the infiltration capacity of the soil may have been reduced by structural degradation due to large cumulative rainfall amounts after harrowing. Concentrations in surface runoff exceeded Swedish water quality standards in all samples during this growing season for diflufenican and pirimicarb. Surface runoff was generated during three snowmelt periods during the winter of 2012-2013. All of the applied pesticides were found in snowmelt samples despite incorporation of residues by autumn plowing, degradation, and leaching into the soil profile during the period between spraying and sampling. Concentrations of glyphosate ranged from 0.12 to 7.4 μg L, and concentrations of AMPA ranged from 0 to 2.7 μg L. Our results indicate that temporal changes in hydraulic properties during the growing season and when the soil freezes during winter affect pesticide losses through surface runoff. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Spatial and temporal distribution of 13C labelled plant residues in soil aggregates and Lumbricus terrestris surface casts: A combination of Transmission Electron Microscopy and Nanoscale Secondary Ion Mass Spectrometry

NASA Astrophysics Data System (ADS)

Vidal, Alix; Remusat, Laurent; Watteau, Françoise; Derenne, Sylvie; Quenea, Katell

2016-04-01

Earthworms play a central role in litter decomposition, soil structuration and carbon cycling. They ingest both organic and mineral compounds which are mixed, complexed with mucus and dejected in form of casts at the soil surface and along burrows. Bulk isotopic or biochemical technics have often been used to study the incorporation of litter in soil and casts, but they could not reflect the complex interaction between soil, plant and microorganisms at the microscale. However, the heterogeneous distribution of organic carbon in soil structures induces contrasted microbial activity areas. Nano-scale secondary ion mass spectrometry (NanoSIMS), which is a high spatial resolution method providing elemental and isotopic maps of organic and mineral materials, has recently been applied in soil science (Herrmann et al., 2007; Vogel et al., 2014). The combination of Nano-scale secondary ion mass spectrometry (NanoSIMS) and Transmission Electron Microscopy (TEM) has proven its potential to investigate labelled residues incorporation in earthworm casts (Vidal et al., 2016). In line of this work, we studied the spatial and temporal distribution of plant residues in soil aggregates and earthworm surface casts. This study aimed to (1) identify the decomposition states of labelled plant residues incorporated at different time steps, in casts and soil, (2) identify the microorganisms implied in this decomposition (3) relate the organic matter states of decomposition with their 13C signature. A one year mesocosm experiment was set up to follow the incorporation of 13C labelled Ryegrass (Lolium multiflorum) litter in a soil in the presence of anecic earthworms (Lumbricus terrestris). Soil and surface cast samples were collected after 8 and 54 weeks, embedded in epoxy resin and cut into ultra-thin sections. Soil was fractionated and all and analyzed with TEM and NanoSIMS, obtaining secondary ion images of 12C, 16O, 12C14N, 13C14N and 28Si. The δ13C maps were obtained using the 13C14N-/12C14N- ratio. We identified various states of decomposition within a same sample, associated with a high heterogeneity of δ13C values of plant residues. We also recognized various labelled microorganisms, mainly bacteria and fungi, underlining their participation in residues decomposition. δ13C values were higher in casts than soil aggregates and decreased between 8 and 54 weeks for both samples. Herrmann, A.M., Ritz, K., Nunan, N., Clode, P.L., Pett-Ridge, J., Kilburn, M.R., Murphy, D.V., O'Donnell, A.G., Stockdale, E.A., 2007. Nano-scale secondary ion mass spectrometry - A new analytical tool in biogeochemistry and soil ecology: A review article. Soil Biology and Biochemistry. 39, 1835-1850. Vidal, A., Remusat, L., Watteau, F., Derenne, S., Quenea K., 2016. Incorporation of 13C labelled shoot residues in Lumbricus terrestris casts: A combination of Transmission Electron Microscopy and Nanoscale Secondary Ion Mass Spectrometry. Soil Biology and Biochemistry. Vogel, C., Mueller, C.W., Höschen, C., Buegger, F., Heister, K., Schulz, S., Schloter, M., Kögel-Knabner, I., 2014. Submicron structures provide preferential spots for carbon and nitrogen sequestration in soils. Nature Communications 5.

How biological soil crusts became recognized as a functional unit: a selective history

USGS Publications Warehouse

Lange, Otto L.; Belnap, Jayne

2016-01-01

It is surprising that despite the world-wide distribution and general importance of biological soil crusts (biocrusts), scientific recognition and functional analysis of these communities is a relatively young field of science. In this chapter, we sketch the historical lines that led to the recognition of biocrusts as a community with important ecosystem functions. The idea of biocrusts as a functional ecological community has come from two main scientific branches: botany and soil science. For centuries, botanists have long recognized that multiple organisms colonize the soil surface in the open and often dry areas occurring between vascular plants. Much later, after the initial taxonomic and phyto-sociological descriptions were made, soil scientists and agronomists observed that these surface organisms interacted with soils in ways that changed the soil structure. In the 1970’s, research on these communities as ecological units that played an important functional role in drylands began in earnest, and these studies have continued to this day. Here, we trace the history of these studies from the distant past until 1990, when biocrusts became well-known to scientists and the public.

Bird Perches Increase Forest Seeds on Puerto Rican Landslides.

Treesearch

Aaron B. Shiels; Lawrence R. Walker

2003-01-01

Landslides result in the loss of vertical vegetative structure, soil nutrients, and the soil seed bank. These losses impede timely recovery of tropical forest communities. In this study we added bird perches to six Puerto Rican landslides with three types of surfaces (bare, climbing fern, grass) in an effort to facilitate inputs of forest seeds through bird dispersal...

Response of Surface Soil Hydrology to the Micro-Pattern of Bio-Crust in a Dry-Land Loess Environment, China

PubMed Central

Wei, Wei; Yu, Yun; Chen, Liding

2015-01-01

The specific bio-species and their spatial patterns play crucial roles in regulating eco-hydrologic process, which is significant for large-scale habitat promotion and vegetation restoration in many dry-land ecosystems. Such effects, however, are not yet fully studied. In this study, 12 micro-plots, each with size of 0.5 m in depth and 1 m in length, were constructed on a gentle grassy hill-slope with a mean gradient of 8° in a semiarid loess hilly area of China. Two major bio-crusts, including mosses and lichens, had been cultivated for two years prior to the field simulation experiments, while physical crusts and non-crusted bare soils were used for comparison. By using rainfall simulation method, four designed micro-patterns (i.e., upper bio-crust and lower bare soil, scattered bio-crust, upper bare soil and lower bio-crust, fully-covered bio-crust) to the soil hydrological response were analyzed. We found that soil surface bio-crusts were more efficient in improving soil structure, water holding capacity and runoff retention particularly at surface 10 cm layers, compared with physical soil crusts and non-crusted bare soils. We re-confirmed that mosses functioned better than lichens, partly due to their higher successional stage and deeper biomass accumulation. Physical crusts were least efficient in water conservation and erosion control, followed by non-crusted bare soils. More importantly, there were marked differences in the efficiency of the different spatial arrangements of bio-crusts in controlling runoff and sediment generation. Fully-covered bio-crust pattern provides the best option for soil loss reduction and runoff retention, while a combination of upper bio-crust and lower bare soil pattern is the least one. These findings are suggested to be significant for surface-cover protection, rainwater infiltration, runoff retention, and erosion control in water-restricted and degraded natural slopes. PMID:26207757

Response of Surface Soil Hydrology to the Micro-Pattern of Bio-Crust in a Dry-Land Loess Environment, China.

PubMed

Wei, Wei; Yu, Yun; Chen, Liding

2015-01-01

The specific bio-species and their spatial patterns play crucial roles in regulating eco-hydrologic process, which is significant for large-scale habitat promotion and vegetation restoration in many dry-land ecosystems. Such effects, however, are not yet fully studied. In this study, 12 micro-plots, each with size of 0.5 m in depth and 1 m in length, were constructed on a gentle grassy hill-slope with a mean gradient of 8° in a semiarid loess hilly area of China. Two major bio-crusts, including mosses and lichens, had been cultivated for two years prior to the field simulation experiments, while physical crusts and non-crusted bare soils were used for comparison. By using rainfall simulation method, four designed micro-patterns (i.e., upper bio-crust and lower bare soil, scattered bio-crust, upper bare soil and lower bio-crust, fully-covered bio-crust) to the soil hydrological response were analyzed. We found that soil surface bio-crusts were more efficient in improving soil structure, water holding capacity and runoff retention particularly at surface 10 cm layers, compared with physical soil crusts and non-crusted bare soils. We re-confirmed that mosses functioned better than lichens, partly due to their higher successional stage and deeper biomass accumulation. Physical crusts were least efficient in water conservation and erosion control, followed by non-crusted bare soils. More importantly, there were marked differences in the efficiency of the different spatial arrangements of bio-crusts in controlling runoff and sediment generation. Fully-covered bio-crust pattern provides the best option for soil loss reduction and runoff retention, while a combination of upper bio-crust and lower bare soil pattern is the least one. These findings are suggested to be significant for surface-cover protection, rainwater infiltration, runoff retention, and erosion control in water-restricted and degraded natural slopes.

Geomys bursars burrowing patterns: influence of season and food patch structure

USGS Publications Warehouse

Andersen, Douglas C.

1987-01-01

The relationship between belowground food resources and the pattern and pace of soil excavation by Geomys bursarius, the plains pocket gopher, was assessed during spring and autumn using replicated 18 x 18 m enclosures containing uniform arrays of food plants (Daucus carota) at spacings assumed to result in burrowing being energetically profitable (25 and 50 cm) or unprofitable (100 cm and empty). Soil excavation rate, measured in terms of either daily additions to tunnel length or volume, or the maximum volume excavated during a 3-d interval, varied greatly among individuals. No significant effect due to season or density of belowground plant biomass was detected when burrowing was profitable. Individuals readily initiated aboveground travel in unprofitable treatments. Soil bulk density was negatively related and animal body mass positively related to excavation rate. Individuals deposited from 41 to 87% of excavated soil on the ground surface; the remainder was used to backfill previously created tunnels or chambers. Plant size, but not plant spacing, affected the ratio of the volumes deposited aboveground and belowground. There was no evidence that animals in enclosures disturbed soil in a manner quantitatively or qualitatively different from free-ranging adults. The large proportions and absolute quantities (up to 30 L/d) of soil involved suggest that backfilling may affect ecosystem structure and functioning as much as surface mound-building.

Evaluation of resolution-precision relationships when using Structure-from-Motion to measure low intensity erosion processes, within a laboratory setting.

NASA Astrophysics Data System (ADS)

Benaud, Pia; Anderson, Karen; Quine, Timothy; James, Mike; Quinton, John; Brazier, Richard E.

2017-04-01

The accessibility of Structure-from-Motion Multi-Stereo View (SfM) and the potential for multi-temporal applications, offers an exciting opportunity to quantify soil erosion spatially. Accordingly, published research provides examples of the successful quantification of large erosion features and events, to centimetre accuracy. Through rigorous control of the camera and image network geometry, the centimetre accuracy achievable at the field scale, can translate to sub-millimetre accuracies within a laboratory environment. The broad aim of this study, therefore, was to understand how ultra-high-resolution spatial information on soil surface topography, derived from SfM, can be utilised to develop a spatially explicit, mechanistic understanding of rill and inter-rill erosion, under experimental conditions. A rainfall simulator was used to create three soil surface conditions; compaction and rainsplash erosion, inter-rill erosion, and rill erosion. Total sediment capture was the primary validation for the experiments, allowing the comparison between structurally and volumetrically derived change, and true soil loss. A Terrestrial Laser Scanner (resolution of ca. 0.8mm) was employed to assess spatial discrepancies within the SfM datasets and to provide an alternative measure of volumetric change. The body of work will present the workflow that has been developed for the laboratory-scale studies and provide information on the importance of DTM resolution for volumetric calculations of soil loss, under different soil surface conditions. To-date, using the methodology presented, point clouds with ca. 3.38 x 107 points per m2, and RMSE values of 0.17 to 0.43 mm (relative precision 1:2023-5117), were constructed. Preliminary results suggest a decrease in DTM resolution from 0.5 to 10 mm does not result in a significant change in volumetric calculations (p = 0.088), while affording a 24-fold decrease in processing times, but may impact negatively on mechanistic understanding of patterns of erosion. It is argued that the approach can be an invaluable tool for the spatially-explicit evaluation of soil erosion models.

Estimation of small-scale soil erosion in laboratory experiments with Structure from Motion photogrammetry

NASA Astrophysics Data System (ADS)

Balaguer-Puig, Matilde; Marqués-Mateu, Ángel; Lerma, José Luis; Ibáñez-Asensio, Sara

2017-10-01

The quantitative estimation of changes in terrain surfaces caused by water erosion can be carried out from precise descriptions of surfaces given by means of digital elevation models (DEMs). Some stages of water erosion research efforts are conducted in the laboratory using rainfall simulators and soil boxes with areas less than 1 m2. Under these conditions, erosive processes can lead to very small surface variations and high precision DEMs are needed to account for differences measured in millimetres. In this paper, we used a photogrammetric Structure from Motion (SfM) technique to build DEMs of a 0.5 m2 soil box to monitor several simulated rainfall episodes in the laboratory. The technique of DEM of difference (DoD) was then applied using GIS tools to compute estimates of volumetric changes between each pair of rainfall episodes. The aim was to classify the soil surface into three classes: erosion areas, deposition areas, and unchanged or neutral areas, and quantify the volume of soil that was eroded and deposited. We used a thresholding criterion of changes based on the estimated error of the difference of DEMs, which in turn was obtained from the root mean square error of the individual DEMs. Experimental tests showed that the choice of different threshold values in the DoD can lead to volume differences as large as 60% when compared to the direct volumetric difference. It turns out that the choice of that threshold was a key point in this method. In parallel to photogrammetric work, we collected sediments from each rain episode and obtained a series of corresponding measured sediment yields. The comparison between computed and measured sediment yields was significantly correlated, especially when considering the accumulated value of the five simulations. The computed sediment yield was 13% greater than the measured sediment yield. The procedure presented in this paper proved to be suitable for the determination of sediment yields in rainfall-driven soil erosion experiments conducted in the laboratory.

[Community structure and seasonal change of soil micro-arthropodes in the Lower Reaches of Liaohe River Plain under different land utilization].

PubMed

Ke, Xin; Liang, Wenju; Yu, Wantai; Xie, Rongdong; Weng, Chaolian; Yang, Yiming; Yin, Wenying

2004-04-01

The data on the soil micro-arthropodes under four land utilization types (fallow, forest, upland field and paddy) in the Lower Reaches of Liaohe River Plain were collected in a period from October 2000 to October 2001. Using the community parameters of population density, group richness, diversity index and evenness, the community structure and its seasonal changes were described. There were 12 groups of soil micro-arthropodes in this region, and of the groups, Collembola and Acarina were dominant, and Diptera, Coleoptera and Hymenoptera were often seen in fallow, forest and upland field, while Collembola, Acarina and Diptera were dominant in paddy. Both land utilization and seasonal change influenced the population density, group richness and diversity index of soil micro-arthropodes. The vertical distribution in both density and group number of arthropods in soil was in the order of surface > middle > bottom.

Soil microbial community profiles and functional diversity in limestone cedar glades

USGS Publications Warehouse

Cartwright, Jennifer M.; Dzantor, E. Kudjo; Momen, Bahram

2016-01-01

Rock outcrop ecosystems, such as limestone cedar glades (LCGs), are known for their rare and endemic plant species adapted to high levels of abiotic stress. Soils in LCGs are thin (< 25 cm), soil-moisture conditions fluctuate seasonally between xeric and saturated, and summer soil temperatures commonly exceed 48 °C. The effects of these stressors on soil microbial communities (SMC) remain largely unstudied, despite the importance of SMC-plant interactions in regulating the structure and function of terrestrial ecosystems. SMC profiles and functional diversity were characterized in LCGs using community level physiological profiling (CLPP) and plate-dilution frequency assays (PDFA). Most-probable number (MPN) estimates and microbial substrate-utilization diversity (H) were positively related to soil thickness, soil organic matter (OM), soil water content, and vegetation density, and were diminished in alkaline soil relative to circumneutral soil. Soil nitrate showed no relationship to SMCs, suggesting lack of N-limitation. Canonical correlation analysis indicated strong correlations between microbial CLPP patterns and several physical and chemical properties of soil, primarily temperature at the ground surface and at 4-cm depth, and secondarily soil-water content, enabling differentiation by season. Thus, it was demonstrated that several well-described abiotic determinants of plant community structure in this ecosystem are also reflected in SMC profiles.

Different Effects of Roughness (Granularity) and Hydrophobicity

NASA Astrophysics Data System (ADS)

Shirtcliffe, Neil; McHale, Glen; Hamlett, Christopher; Newton, Michael

2010-05-01

With thanks to Stefan Doerr and Jorge Mataix-Solera for their invitation Superhydrophobicity is an interesting effect that appears to be simple on the outset; increased surface area from roughness increases interfacial area and therefore energy loss or gain. More extreme roughness prevents total wetting, resulting in gas pockets present at the surface and a drastic change in the properties of the system. Increases in complexity of the system, by adding porosity (granularity), allowing the structures to move, varying the shape of the roughness or the composition of the liquid used often has unexpected effects. Here we will consider a few of these related to complex topography. Overhanging features are commonly used in test samples as they perform better in some tests than simple roughness. It has been shown to be a prerequisite for superoleophobic surfaces as it allows liquids to be suspended for contact angles considerably below 90°. It also allows trapping of gas in lower layers even if the first layer is flooded. This is important in soils as a fixed bed of granules behaves just like a surface with overhanging roughness. Using simple geometry it is possible to predict at what contact angle penetration will occur. Plants have some structured superhydrophobic surfaces and we have shown that some use them in conjunction with other structured surfaces to control water flows. This allows some plants to survive in difficult environments and shows us how subtly different structures interact completely differently with water. Long fibres can either cause water droplets to roll over a plant surface or halt it in its tracks. Implications of this in soils include predicting when particles will adhere more strongly to water drops and why organic fibrous material may play a greater role in the behaviour of water in soils than may be expected from the amount present. The garden snail uses a biosurfactant that is very effective at wetting surfaces and can crawl over most superhydrophobic surfaces. There are some, however, that defeat even the snail's complex slime. Looking at these surfaces in more detail reveals that some superhydrophobic surfaces are much more resistant to the effects of surfactants than others. As mentioned above, overhanging structures, such as those found in granular materials are particularly effective at suspending liquids. This does not, however, always translate to them being more effective against surfactants, unfortunately, however, surfactants are not always as effective as we would like them to be, although drops do not skate across superhydrophobic surfaces they often do not penetrate into them fully either.

Agriculturization in the Argentinean Northern Humid Pampas: the Impact on Soil Structure and Runoff

NASA Astrophysics Data System (ADS)

Sasal, M. C.; Léonard, J.; Andriulo, A.; Wilson, M. G.

2012-04-01

Argentina is among the countries with the largest cropped area under no-tillage (NT). No tillage was adopted in the northern Humid Pampas to reduce the widespread soil degradation by water erosion. With the advent of genetically modified soybean varieties, NT has developed exponentially. This evolution, combined with the influence of the international market trend, has resulted in large changes in crop sequence composition toward the disappearance of pastures and the expansion of soybean monoculture. The aim of this work was to evaluate the long-term consequences of these changes on the topsoil structure and the way in which the evolution of soil structure relates to the simplification of the crop sequence and to runoff at a regional scale. We analyzed the topsoil structure of 25 sites with Argiudolls having 4 to 29 consecutive years of NT using the cultural profile approach. An intensification sequence index (ISI) was calculated as the ratio between the length of the growth period and the length of the year. Fifteen natural-rainfall runoff plots (100 m2) with 3.5% slope were used to analyze the relationship between soil structural state, crop sequence and runoff for four years. Four types of soil structures were identified and a general pattern of vertical soil structure organization was revealed. The top centimeters of 72% of the sites were dominated by a granular structure. Platy soil structure development was omnipresent: all sites exhibited a horizontal platy structure (<10 cm thick) developing either directly from the soil surface or from below the granular structure. Below the platy structure layer, a gamma soil structure (with visible structural porosity) was observed in all sites (30-75% of the A horizon), while compacted delta soil structure was detected in localized zones. A significant parabolic relationship (R2=0.60) was found between the number of consecutive years under NT and the proportion of platy structure in the A horizon. The proportion of platy structure increased during the first 15 years of NT, and then the extension of platy structure tended to stabilize and even to decrease after 20 to 25 years. The development of platy soil structure was negatively related to the ISI (R2=0.57) and runoff increased as the proportion of platy structure increased and the proportion of granular structure decreased (R2=0.85). We concluded that high soybean frequency in cropping systems under NT favors the extension of platy soil structure and increases runoff. More than 70% of the agricultural area of the northern Humid Pampas region is currently covered by soybean cultivation, mostly as a single annual crop (ISI=0.38). Our results thus suggest that promoting management practices such as the expansion of wheat/soybean double crop (ISI=0.83) could limit soil structure degradation and reduce runoff and the associated environmental risks.

Influence of Biochar on C and N Transformation in Soil and Their Impact on Greenhouse Gas Emissions

NASA Astrophysics Data System (ADS)

Chintala, R.; Schumacher, T. E.; Kumar, S.; Clay, D. E.; Malo, D. D.

2014-12-01

The capacity of pyrogenic biochar to mitigate soil surface exchange of greenhouse gases (GHG) is dependent on the influence of biochar on physiochemical transformations of C and N in soils. Incorporated biochar amendments are hypothesized to interfere with transformations of C and N as a result of the unique recalcitrant chemical structure and surface complexity of biochars. The nature of interference by biochar with C and N transformations are assumed to be dynamic not only due to their highly variable amphilicity inherited from feedstock source and controlled pyrolytic processing parameters but also to variation in soil factors. Experiments comprised of laboratory and field studies were designed to gain insight into the priming effect of incorporated non-native biochar materials on the transformations of C and N species in the soil. Molecular structure and surface functionality of plant based biochar materials produced from carbon optimized gasification of corn stover (Zea mays L.), Ponderosa pine (Pinus ponderosa Lawson and C. Lawson) wood residue, and switchgrass (Panicum virgatum L.) were studied in the laboratory using NMR and SEM-EdX. Biochar materials were found to be highly hydrophobic (low H/C values) with high aromaticity. The surface morphology of all the biochar materials was highly heterogeneous and pore size ranged from 1-22µm with the faces and edges of ordered sheets. In the field study, all the three biochar types were applied at a 1% (w/w) rate to a Maddock soil (Sandy, Mixed, Frigid Entic Hapludolls) located in an eroded upper landscape position and a Brookings soil (Fine-Silty, Mixed, Superactive, Frigid Pachic Hapludolls) located in a depositional landscape position. The crop rotation is a corn (Zea mays L.) followed by soybean (Glycine max L.). The priming effect of biochars on the transformations of C and N is determined by measuring the changes in soil C (total organic carbon, microbial biomass C, hydrolyzable C, and δ 13C) and N pools (microbial biomass N, inorganic N, and δ 15N). Greenhouse gas fluxes (CO2, CH4, and N2O) were measured and correlation studies will be conducted to determine the relationship with the interference effect of biochars on C and N transformation in soil. Initial data shows that biochar has an impact especially on CO2, and N2O emissions.

Complementary effects of surface water and groundwater on soil moisture dynamics in a degraded coastal floodplain forest

NASA Astrophysics Data System (ADS)

Kaplan, D.; Muñoz-Carpena, R.

2011-02-01

SummaryRestoration of degraded floodplain forests requires a robust understanding of surface water, groundwater, and vadose zone hydrology. Soil moisture is of particular importance for seed germination and seedling survival, but is difficult to monitor and often overlooked in wetland restoration studies. This research hypothesizes that the complex effects of surface water and shallow groundwater on the soil moisture dynamics of floodplain wetlands are spatially complementary. To test this hypothesis, 31 long-term (4-year) hydrological time series were collected in the floodplain of the Loxahatchee River (Florida, USA), where watershed modifications have led to reduced freshwater flow, altered hydroperiod and salinity, and a degraded ecosystem. Dynamic factor analysis (DFA), a time series dimension reduction technique, was applied to model temporal and spatial variation in 12 soil moisture time series as linear combinations of common trends (representing shared, but unexplained, variability) and explanatory variables (selected from 19 additional candidate hydrological time series). The resulting dynamic factor models yielded good predictions of observed soil moisture series (overall coefficient of efficiency = 0.90) by identifying surface water elevation, groundwater elevation, and net recharge (cumulative rainfall-cumulative evapotranspiration) as important explanatory variables. Strong and complementary linear relationships were found between floodplain elevation and surface water effects (slope = 0.72, R2 = 0.86, p < 0.001), and between elevation and groundwater effects (slope = -0.71, R2 = 0.71, p = 0.001), while the effect of net recharge was homogenous across the experimental transect (slope = 0.03, R2 = 0.05, p = 0.242). This study provides a quantitative insight into the spatial structure of groundwater and surface water effects on soil moisture that will be useful for refining monitoring plans and developing ecosystem restoration and management scenarios in degraded coastal floodplains.

Keeping soil in the field - runoff and erosion management in asparagus crops

NASA Astrophysics Data System (ADS)

Niziolomski, Joanna; Simmons, Robert; Rickson, Jane; Hann, Mike

2016-04-01

Row crop production (including potatoes, onions, carrots, asparagus, bulbs and lettuce) is regarded as one of the most erosive agricultural cropping systems. This is a result of the many practices involved that increase erosion risk including: fine seedbed preparation, a typically short growing season where adequate ground cover protects the soil, permanent bare soil areas between crops, and often intensive harvesting methods that can damage soil structure and result in soil compaction. Sustained exposure of bare soil coupled with onsite compaction on slightly sloping land results in soil and water issues in asparagus production. Asparagus production is a growing British industry covering > 2000 ha and is worth approximately £30 million yr-1. However, no tried and tested erosion control measurements currently exist to manage associated problems. Research has recently been undertaken investigating the effectiveness of erosion control measures suitable for asparagus production systems. These consisted of surface applied wheat straw mulch and shallow soil disturbance (< 350 mm) using several tine configurations: a currently adopted winged tine, a narrow with two shallow leading tines, and a modified para-plough. These treatments were tested individually and in combination (straw mulch with each shallow soil disturbance tine configuration) using triplicated field plots situated on a working asparagus farm in Herefordshire, UK. Testing was conducted between May and November 2013. Rainfall-event based runoff and erosion measurements were taken including; runoff volume, runoff rate and total soil loss. Runoff and soil erosion was observed from all treatments. However, the surface application of straw mulch alone out performed each shallow soil disturbance practice. This suggests that runoff and erosion from asparagus production can be reduced using the simple surface application of straw.

Using SMOS brightness temperature and derived surface-soil moisture to characterize surface conditions and validate land surface models.

NASA Astrophysics Data System (ADS)

Polcher, Jan; Barella-Ortiz, Anaïs; Piles, Maria; Gelati, Emiliano; de Rosnay, Patricia

2017-04-01

The SMOS satellite, operated by ESA, observes the surface in the L-band. On continental surface these observations are sensitive to moisture and in particular surface-soil moisture (SSM). In this presentation we will explore how the observations of this satellite can be exploited over the Iberian Peninsula by comparing its results with two land surface models : ORCHIDEE and HTESSEL. Measured and modelled brightness temperatures show a good agreement in their temporal evolution, but their spatial structures are not consistent. An empirical orthogonal function analysis of the brightness temperature's error identifies a dominant structure over the south-west of the Iberian Peninsula which evolves during the year and is maximum in autumn and winter. Hypotheses concerning forcing-induced biases and assumptions made in the radiative transfer model are analysed to explain this inconsistency, but no candidate is found to be responsible for the weak spatial correlations. The analysis of spatial inconsistencies between modelled and measured TBs is important, as these can affect the estimation of geophysical variables and TB assimilation in operational models, as well as result in misleading validation studies. When comparing the surface-soil moisture of the models with the product derived operationally by ESA from SMOS observations similar results are found. The spatial correlation over the IP between SMOS and ORCHIDEE SSM estimates is poor (ρ 0.3). A single value decomposition (SVD) analysis of rainfall and SSM shows that the co-varying patterns of these variables are in reasonable agreement between both products. Moreover the first three SVD soil moisture patterns explain over 80% of the SSM variance simulated by the model while the explained fraction is only 52% of the remotely sensed values. These results suggest that the rainfall-driven soil moisture variability may not account for the poor spatial correlation between SMOS and ORCHIDEE products. Other reasons have to be sought to explain the poor agreement in spatial patterns between satellite derived and modelled SSM. This presentation will hopefully contribute to the discussion of how SMOS and other observations can be used to prepare, carry-out and exploit a field campaign over the Iberian Peninsula which aims at improving our understanding of semi-arid land surface processes.

Experimental Verification of Integrity of Low-Pressure Injection Piles Structure - Pile Internal Capacity

NASA Astrophysics Data System (ADS)

Pachla, Henryk

2017-12-01

The idea of strengthening the foundation using injection piles lies in transferring loads from the foundation to the piles anchorage in existing structure and formed in the soil. Such a system has to be able to transfer loads from the foundation to the pile and from the pile onto the soil. Pile structure often reinforced with steel element has to also be able to transfer such a loading. According to the rules of continuum mechanics, the bearing capacity of such a system and a deformation of its individual elements can be determined by way of an analysis of the contact problem of three interfaces. Each of these surfaces is determined by different couples of materials. Those surfaces create: pile-foundation anchorage, bonding between reinforcement and material from which the pile is formed and pilesoil interface. What is essential is that on the contact surfaces the deformation of materials which adhere to each other can vary and depends on the mechanical properties and geometry of these surfaces. Engineering practice and experimental research point out that the failure in such structures occurs at interfaces. The paper is concentrating on presenting the experiments on interaction between cement grout and various types of steel reinforcement. The tests were conducted on the special low pressure injection piles widely used to strengthen foundations of already existing structures of historical buildings due to the technology of formation and injection pressure.

Screening hydroxyapatite for cadmium and lead immobilization in aqueous solution and contaminated soil: The role of surface area.

PubMed

Li, Hongying; Guo, Xisheng; Ye, Xinxin

2017-02-01

Hydroxyapatite (HAP) has been widely used to immobilize many cationic metals in water and soils. The specific reason why an increase in the surface area of HAP enhances cadmium (Cd) uptake, but has no effect on lead (Pb) uptake, is not clear. The aim of this study was to determine the factors causing the differences in sorption behavior between Cd and Pb by evaluating HAPs with different surface areas. We synthesized HAPs with two different surface areas, which were characterized by X-ray diffraction, N 2 adsorption, and scanning electron microscopy, and then evaluated them as sorbents for Cd and Pb removal by testing in single and binary systems. The sorption capacity of large surface area HAP (1.85mmol/g) for Cd in the single-metal system was higher than that of small surface area HAP (0.64mmol/g), but there were no differences between single- and binary-metal solutions containing Pb. After the Cd experiments, the HAP retained a stable structure and intact morphology, which promotes the accessibility of reactive sites for Cd. However, a newly formed precipitate covered the surface and blocked the channels in the presence of Pb, which reduced the number of potential adsorption sites on HAP for Cd and Pb. Remediation experiments using Cd- and Pb-contaminated soil produced similar results to the solution tests. These results indicate that alterations of the structure and morphology during the reaction is an important factor influencing metal sorption to HAP. Copyright © 2016. Published by Elsevier B.V.

Short and Long-Term Soil Moisture Effects of Liana Removal in a Seasonally Moist Tropical Forest

PubMed Central

Reid, Joseph Pignatello; Schnitzer, Stefan A.; Powers, Jennifer S.

2015-01-01

Lianas (woody vines) are particularly abundant in tropical forests, and their abundance is increasing in the neotropics. Lianas can compete intensely with trees for above- and belowground resources, including water. As tropical forests experience longer and more intense dry seasons, competition for water is likely to intensify. However, we lack an understanding of how liana abundance affects soil moisture and hence competition with trees for water in tropical forests. To address this critical knowledge gap, we conducted a large-scale liana removal experiment in a seasonal tropical moist forest in central Panama. We monitored shallow and deep soil moisture over the course of three years to assess the effects of lianas in eight 0.64 ha removal plots and eight control plots. Liana removal caused short-term effects in surface soils. Surface soils (10 cm depth) in removal plots dried more slowly during dry periods and accumulated water more slowly after rainfall events. These effects disappeared within four months of the removal treatment. In deeper soils (40 cm depth), liana removal resulted in a multi-year trend towards 5–25% higher soil moisture during the dry seasons with the largest significant effects occurring in the dry season of the third year following treatment. Liana removal did not affect surface soil temperature. Multiple and mutually occurring mechanisms may be responsible for the effects of liana removal on soil moisture, including competition with trees, and altered microclimate, and soil structure. These results indicate that lianas influence hydrologic processes, which may affect tree community dynamics and forest carbon cycling. PMID:26545205

A Catchment-Based Approach to Modeling Land Surface Processes in a GCM. Part 1; Model Structure

NASA Technical Reports Server (NTRS)

Koster, Randal D.; Suarez, Max J.; Ducharne, Agnes; Stieglitz, Marc; Kumar, Praveen

2000-01-01

A new strategy for modeling the land surface component of the climate system is described. The strategy is motivated by an arguable deficiency in most state-of-the-art land surface models (LSMs), namely the disproportionately higher emphasis given to the formulation of one-dimensional, vertical physics relative to the treatment of horizontal heterogeneity in surface properties -- particularly subgrid soil moisture variability and its effects on runoff generation. The new strategy calls for the partitioning of the continental surface into a mosaic of hydrologic catchments, delineated through analysis of high-resolution surface elevation data. The effective "grid" used for the land surface is therefore not specified by the overlying atmospheric grid. Within each catchment, the variability of soil moisture is related to characteristics of the topography and to three bulk soil moisture variables through a well-established model of catchment processes. This modeled variability allows the partitioning of the catchment into several areas representing distinct hydrological regimes, wherein distinct (regime-specific) evaporation and runoff parameterizations are applied. Care is taken to ensure that the deficiencies of the catchment model in regions of little to moderate topography are minimized.

Temporal Stability of Surface Roughness Effects on Radar Based Soil Moisture Retrieval During the Corn Growth Cycle

NASA Technical Reports Server (NTRS)

Joseph, A.T.; Lang, R.; O'Neill, P.E.; van der Velde, R.; Gish, T.

2008-01-01

A representative soil surface roughness parameterization needed for the retrieval of soil moisture from active microwave satellite observation is difficult to obtain through either in-situ measurements or remote sensing-based inversion techniques. Typically, for the retrieval of soil moisture, temporal variations in surface roughness are assumed to be negligible. Although previous investigations have suggested that this assumption might be reasonable for natural vegetation covers (Moran et al. 2002, Thoma et al. 2006), insitu measurements over plowed agricultural fields (Callens et al. 2006) have shown that the soil surface roughness can change considerably over time. This paper reports on the temporal stability of surface roughness effects on radar observations and soil moisture retrieved from these radar observations collected once a week during a corn growth cycle (May 10th - October 2002). The data set employed was collected during the Optimizing Production Inputs for Economic and Environmental Enhancement (OPE3) field campaign covering this 2002 corn growth cycle and consists of dual-polarized (HH and VV) L-band (1.6 GHz) acquired at view angles of 15, 35, and 55 degrees. Cross-polarized L baud radar data were also collected as part of this experiment, but are not used in the analysis reported on here. After accounting for vegetation effects on radar observations, time-invariant optimum roughness parameters were determined using the Integral Equation Method (IEM) and radar observations acquired over bare soil and cropped conditions (the complete radar data set includes entire corn growth cycle). The optimum roughness parameters, soil moisture retrieval uncertainty, temporal distribution of retrieval errors and its relationship with the weather conditions (e.g. rainfall and wind speed) have been analyzed. It is shown that over the corn growth cycle, temporal roughness variations due to weathering by rain are responsible for almost 50% of soil moisture retrieval uncertainty depending on the sensing configuration. The effects of surface roughness variations are found to be smallest for observations acquired at a view angle of 55 degrees and HH polarization. A possible explanation for this result is that at 55 degrees and HH polarization the effect of vertical surface height changes on the observed radar response are limited because the microwaves travel parallel to the incident plane and as a result will not interact directly with vertically oriented soil structures.

A Novel Growing Device Inspired by Plant Root Soil Penetration Behaviors

PubMed Central

Sadeghi, Ali; Tonazzini, Alice; Popova, Liyana; Mazzolai, Barbara

2014-01-01

Moving in an unstructured environment such as soil requires approaches that are constrained by the physics of this complex medium and can ensure energy efficiency and minimize friction while exploring and searching. Among living organisms, plants are the most efficient at soil exploration, and their roots show remarkable abilities that can be exploited in artificial systems. Energy efficiency and friction reduction are assured by a growth process wherein new cells are added at the root apex by mitosis while mature cells of the root remain stationary and in contact with the soil. We propose a new concept of root-like growing robots that is inspired by these plant root features. The device penetrates soil and develops its own structure using an additive layering technique: each layer of new material is deposited adjacent to the tip of the device. This deposition produces both a motive force at the tip and a hollow tubular structure that extends to the surface of the soil and is strongly anchored to the soil. The addition of material at the tip area facilitates soil penetration by omitting peripheral friction and thus decreasing the energy consumption down to 70% comparing with penetration by pushing into the soil from the base of the penetration system. The tubular structure provides a path for delivering materials and energy to the tip of the system and for collecting information for exploratory tasks. PMID:24587244

Surface Runoff Estimation Using SMOS Observations, Rain-gauge Measurements and Satellite Precipitation Estimations. Comparison with Model Predictions

NASA Astrophysics Data System (ADS)

Garcia Leal, Julio A.; Lopez-Baeza, Ernesto; Khodayar, Samiro; Estrela, Teodoro; Fidalgo, Arancha; Gabaldo, Onofre; Kuligowski, Robert; Herrera, Eddy

Surface runoff is defined as the amount of water that originates from precipitation, does not infiltrates due to soil saturation and therefore circulates over the surface. A good estimation of runoff is useful for the design of draining systems, structures for flood control and soil utilisation. For runoff estimation there exist different methods such as (i) rational method, (ii) isochrone method, (iii) triangular hydrograph, (iv) non-dimensional SCS hydrograph, (v) Temez hydrograph, (vi) kinematic wave model, represented by the dynamics and kinematics equations for a uniforme precipitation regime, and (vii) SCS-CN (Soil Conservation Service Curve Number) model. This work presents a way of estimating precipitation runoff through the SCS-CN model, using SMOS (Soil Moisture and Ocean Salinity) mission soil moisture observations and rain-gauge measurements, as well as satellite precipitation estimations. The area of application is the Jucar River Basin Authority area where one of the objectives is to develop the SCS-CN model in a spatial way. The results were compared to simulations performed with the 7-km COSMO-CLM (COnsortium for Small-scale MOdelling, COSMO model in CLimate Mode) model. The use of SMOS soil moisture as input to the COSMO-CLM model will certainly improve model simulations.

Annual compilation and analysis of hydrologic data for Calaveras Creek, San Antonio River basin, Texas 1970

USGS Publications Warehouse

Reddy, D.R.

1971-01-01

The U.S. Soil Conservation Service is actively engaged in the installation of flood and soil erosion reducing measures in Texas under the authority of "The Flood Control Act of 1936 and 1944" and ''Watershed Protection and Flood Prevention Act" (Public Law 566), as amended. The Soil Conservation Service has found a total of approximately 3,500 floodwater-retarding structures to be physically and economically feasible in Texas. As of September 30, 1970, 1,439 of these structures had been built. This watershed-development program will have varying but important effects on the natural surface- and ground-water resources of river basins, especially where a large number of the floodwater-retarding structures are built. Basic hydrologic data under natural and developed conditions are needed to appraise the effects of the structures on the yield and mode of occurrence of runoff.

Annual compilation and analysis of hydrologic data for Honey Creek, Trinity River Basin, Texas, 1969

USGS Publications Warehouse

Sansom, J.N.

1971-01-01

The U.S. Soil Conservation Service is actively engaged in the installation of flood and soil erosion reducing measures in Texas under the authority of ''The Flood Control Act of 1936 and 1944" and ''Watershed Protection and Flood Prevention Act" (Public Law 566), as amended. The Soil Conservation Service has found a total of approximately 3,500 floodwater-retarding structures to be physically and economically feasible in Texas. As of September 30, 1969, 1,355 of these structures had been built. This watershed-development program will have varying but important effects on the natural surface- and ground-water resources of river basins, especially where a large number of the floodwater-retarding structures are built. Basic hydrologic data under natural and developed conditions are needed to appraise the effects of the structures on the yield and mode of occurrence of runoff .

[Effect of pine plantations on soil arthropods in a high Andean forest].

PubMed

León-Gamboa, Alba Lucía; Ramos, Carolina; García, Mary Ruth

2010-09-01

One of the most common problems in the Colombian mountains has been the replacement of native vegetation by pine plantations. Soil arthropods are a fundamental component of forest ecosystem, since they participate in the organic matter fragmentation, previous to decomposition. This role is more valuable in high altitude environments, where low temperatures limit the dynamics of biological processes, where the effects of pine plantations on soil arthropods are still not well-known. In a remnant of high-andean forest (Neusa - Colombia) and a pine plantation of about 50 years-old, it was evaluated the composition, richness and abundance of arthropods at surface (S), organic horizon (O) and mineral horizon (A) of soil, to establish the differences associated to the soil use transformation. It was used "Pitfall" sampling to register the movement of the epigeous fauna, and extraction by funnel Berlese for determining the fauna density from O and A horizons. The Shannon and Simpson indexes estimated the diversity at different places and horizons, and the trophic structure of the community was evaluated. Overall, there were collected 38 306 individuals from forest and 17 386 individuals from pine plantation, mainly distributed in Collembola (42.4%), Acari (27%), Diptera (17.6%) and Coleoptera (4.6%). The most important differences were given in the surface, where the mobilization in forest (86 individuals/day) almost triplicates the one in pine plantation (33 individuals/day). The differences in composition were given in Collembola, Araneae, Hemiptera, Homoptera and Hymenoptera. The dynamics of richness and abundance along the year had significant high values in the native forest than in the pine plantation. The general trophic structure was dominated by saprophagous (75%), followed by predators (14%) and phytophagous (9%), but in two layers of the pine plantation soil (S and O) this structural pattern was not given. Based on the results, it was concluded that pine plantations affect the diversity, composition, community dynamic and trophic structure of soil arthropods. Also, some estimators of soil stability give signals that these effects are reducing the ecosystem function in the region.

Quantitative Analysis Of Three-dimensional Branching Systems From X-ray Computed Microtomography Data

DOE Office of Scientific and Technical Information (OSTI.GOV)

McKinney, Adriana L.; Varga, Tamas

Branching structures such as lungs, blood vessels and plant roots play a critical role in life. Growth, structure, and function of these branching structures have an immense effect on our lives. Therefore, quantitative size information on such structures in their native environment is invaluable for studying their growth and the effect of the environment on them. X-ray computed tomography (XCT) has been an effective tool for in situ imaging and analysis of branching structures. We developed a costless tool that approximates the surface and volume of branching structures. Our methodology of noninvasive imaging, segmentation and extraction of quantitative information ismore » demonstrated through the analysis of a plant root in its soil medium from 3D tomography data. XCT data collected on a grass specimen was used to visualize its root structure. A suite of open-source software was employed to segment the root from the soil and determine its isosurface, which was used to calculate its volume and surface. This methodology of processing 3D data is applicable to other branching structures even when the structure of interest is of similar x-ray attenuation to its environment and difficulties arise with sample segmentation.« less

Stabilities of ant nests and their adjacent soils

NASA Astrophysics Data System (ADS)

Echezona, B. C.; Igwe, C. A.

2012-10-01

Nests habour ants and termites and protect them from harsh environmental conditions. The structural stabilities of nests were studied to ascertain their relative vulnerability to environmental stresses. Arboreal-ant nests were pried from different trees, while epigeous-termite nests were excavated from soil surface within the sample area. Soils without any visible sign of ant or termite activity were also sampled 6 m away from the nests as control. Laboratory analysis result showed that irrespective of the tree hosts, the aggregate stabilities of the ant nests were lower than those of the ground termite, with nests formed on Cola nitida significantly showing lower aggregate stability (19.7%) than other antnest structures. Clay dispersion ratio, moisture content, water stable aggregate class <0.25mm and sand mass were each negatively correlated with aggregate stability, while water stable aggregate class1.00-0.50 mm gave a positive correlation. Nest structures were dominated more by water stable aggregate class >2.00 mm but path analysis demonstrated that water stable aggregate class <0.25 mm contributed most to the higher aggregate stability of the termite nest than the other nest. Nest aggregates had greater structural stability compared to the control soil. The higher structural stability of termite nests over other nest and soil was considered a better adaptive mechanism against body desiccation.

Microbial exopolysaccharides as determinants of geomorphological, hydrological and optical properties of soil crusts from the Precambrian till today

NASA Astrophysics Data System (ADS)

Garcia-Pichel, F.

2012-04-01

The presence of microbial extracellular polysaccharides (EPS) in the soil solution and/or in association with particular microbial types can impart novel properties to biological soil crust (BSC), and hence to soil surfaces. For the most part these properties are of a geobiological relevance that exceeds what one could surmise from its relatively low specific mass content. I will review some examples that range from the mundane to the unexpected. EPS associated with filamentous cyanobacteria can effectively and in the long term stabilize the soil surface against erosive forces, even after the microbes are long gone. Electrostatic interactions between EPS and blowing dust may help retain dust particles, enriching the soil with new nutrient sources. In a telltale sign of BSC presence, EPS is the agent that allows sandy soils to fold and curl-up, to form pee-tee's and elephant-skin surfaces, and to crack into polygons like clays would. EPS in large quantities in flat crusts can retain fluids (both liquid and gaseous) resulting in the alteration of hydrological flow and in the formation of internal vesicular horizons, gas bubbles, pock-marked surfaces and other characteristic structures. Yet, in some settings, EPS plays an architectural role in creating a "spongy" texture that increases hydraulic conductivity. This architectural role can indirectly result in significant increases of a crust's albedo. While the diversity of consequences of EPS presence is far from understood, evidence for its sustained role through Earth's history can be found in the form of sedimentary bio-signatures as far back as the Proterozoic.

K/Ar dating of lunar soils. II

NASA Technical Reports Server (NTRS)

Alexander, E. C., Jr.; Bates, A.; Coscio, M. R., Jr.; Dragon, J. C.; Murthy, V. R.; Pepin, R. O.; Venkatesan, T. R.

1976-01-01

An attempt is made to identify those K/Ar techniques which extract the most reliable chronological information from lunar soils and to define the situations in which the best data are obtainable. Results are presented for determinations of the exposure and K/Ar ages of five lunar soil samples, which were performed by applying correlation techniques for a two-component argon structure to stepwise-heated and neutron-irradiated aliquots of grain-sized separates. It is found that ages deduced from Ar-40/surface-correlated Ar-36 vs K-40/surface-correlated Ar-36 and analogous plots of data from grain-sized separates appear to be the best available K/Ar ages of submature to mature lunar soils, that ages deduced from Ar-40 vs Ar-36 and analogous plots which assume a uniform K content can be significantly in error, and that stepwise-heating (Ar-40)-(Ar-39) experiments yield useful information only for simple immature soils where the K-Ar systematics are dominated by a single component.

Soil hydrological and soil property changes resulting from termite activity on agricultural fields in Burkina Faso

NASA Astrophysics Data System (ADS)

Mettrop, I.; Cammeraat, L. H.; Verbeeten, E.

2009-04-01

Termites are important ecosystem-engineers in subtropical and tropical regions. The effect of termite activity affecting soil infiltration is well documented in the Sahelian region. Most studies find increased infiltration rates on surfaces that are affected by termite activity in comparison to crusted areas showing non-termite presence. Crusted agricultural fields in the Sanmatenga region in Burkina Faso with clear termite activity were compared to control fields without visual ground dwelling termite activity. Fine scale rainfall simulations were carried out on crusted termite affected and control sites. Furthermore soil moisture change, bulk density, soil organic matter as well as general soil characteristics were studied. The top soils in the study area were strongly crusted (structural crust) after the summer rainfall and harvest of millet. They have a loamy sand texture underlain by a shallow sandy loam Bt horizon. The initial soil moisture conditions were significantly higher on the termite plots when compared to control sites. It was found that the amount of runoff produced on the termite plots was significantly higher, and also the volumetric soil moisture content after the experiments was significantly lower if compared to the control plots. Bulk density showed no difference whereas soil organic matter was significantly higher under termite affected areas, in comparison to the control plots. Lab tests showed no significant difference in hydrophobic behavior of the topsoil and crust material. Micro and macro-structural properties of the topsoil did not differ significantly between the termite sites and the control sites. The texture of the top 5 cm of the soil was also found to be not significantly different. The infiltration results are contradictory to the general literature, which reports increased infiltration rates after prolonged termite activity although mostly under different initial conditions. The number of nest entrances was clearly higher in the termite areas, but apparently did not significantly affect infiltration. The increased soil organic matter contents in the termite affected areas however, are as expected from literature, but did not improve soil aggregation which would be expected given the importance of organic matter in soil aggregation in this type of soils. One of the explanations for the reduced infiltration rates might be that termites bring clay from the finer textured subsoil to the surface to build casts over the organic material on the surface (mainly millet stems). It is speculated that the excavated clay material could be involved in crust formation, only present is in the upper 0.5 cm of the soil crust, which is enough to block pores in the crust surface, hampering infiltration. The topsoil aggregates are slaking under the summer rainfall and the increase in fine textured material, excavated by the termites, could be incorporated into the crust and reduce infiltration. Furthermore this specific effect might also be related to the type of termite involved, as impacts from ecosystem engineers on their environment is highly dependent on the specific species involved.

Complete Soil-Structure Interaction (SSI) Analyses of I-walls Embedded in Level Ground During Flood Loading

DTIC Science & Technology

2012-09-01

at the ground surface el 0 ft versus water elevation...sheet pile at the ground surface . ................ 62  Figure 3.24. Total displacements for a water elevation of 16.5 ft and a gap tip elevation of -11...103  Figure 4.19. Relative horizontal displacements of the sheet pile at the ground surface

An improved model for soil surface temperature from air temperature in permafrost regions of Qinghai-Xizang (Tibet) Plateau of China

NASA Astrophysics Data System (ADS)

Hu, Guojie; Wu, Xiaodong; Zhao, Lin; Li, Ren; Wu, Tonghua; Xie, Changwei; Pang, Qiangqiang; Cheng, Guodong

2017-08-01

Soil temperature plays a key role in hydro-thermal processes in environments and is a critical variable linking surface structure to soil processes. There is a need for more accurate temperature simulation models, particularly in Qinghai-Xizang (Tibet) Plateau (QXP). In this study, a model was developed for the simulation of hourly soil surface temperatures with air temperatures. The model incorporated the thermal properties of the soil, vegetation cover, solar radiation, and water flux density and utilized field data collected from Qinghai-Xizang (Tibet) Plateau (QXP). The model was used to simulate the thermal regime at soil depths of 5 cm, 10 cm and 20 cm and results were compared with those from previous models and with experimental measurements of ground temperature at two different locations. The analysis showed that the newly developed model provided better estimates of observed field temperatures, with an average mean absolute error (MAE), root mean square error (RMSE), and the normalized standard error (NSEE) of 1.17 °C, 1.30 °C and 13.84 %, 0.41 °C, 0.49 °C and 5.45 %, 0.13 °C, 0.18 °C and 2.23 % at 5 cm, 10 cm and 20 cm depths, respectively. These findings provide a useful reference for simulating soil temperature and may be incorporated into other ecosystem models requiring soil temperature as an input variable for modeling permafrost changes under global warming.

[Effects of forest regeneration patterns on the quantity and chemical structure of soil solution dissolved organic matter in a subtropical forest.

PubMed

Yuan, Xiao Chun; Lin, Wei Sheng; Pu, Xiao Ting; Yang, Zhi Rong; Zheng, Wei; Chen, Yue Min; Yang, Yu Sheng

2016-06-01

Using the negative pressure sampling method, the concentrations and spectral characte-ristics of dissolved organic matter (DOM) of soil solution were studied at 0-15, 15-30, 30-60 cm layers in Castanopsis carlesii forest (BF), human-assisted naturally regenerated C. carlesii forest (RF), C. carlesii plantation (CP) in evergreen broad-leaved forests in Sanming City, Fujian Pro-vince. The results showed that the overall trend of dissolved organic carbon (DOC) concentrations in soil solution was RF>CP>BF, and the concentration of dissolved organic nitrogen (DON) was highest in C. carlesii plantation. The concentrations of DOC and DON in surface soil (0-15 cm) were all significantly higher than in the subsurface (30-60 cm). The aromatic index (AI) was in the order of RF>CP>BF, and as a whole, the highest AI was observed in the surface soil. Higher fluorescence intensity and a short wave absorption peak (320 nm) were observed in C. carlesii plantation, suggesting the surface soil of C. carlesii plantation was rich in decomposed substance content, while the degree of humification was lower. A medium wave absorption peak (380 nm) was observed in human-assisted naturally regenerated C. carlesii forest, indicating the degree of humification was higher which would contribute to the storage of soil fertility. In addition, DOM characte-ristics in 30-60 cm soil solution were almost unaffected by forest regeneration patterns.

Microbial Signatures of Cadaver Gravesoil During Decomposition.

PubMed

Finley, Sheree J; Pechal, Jennifer L; Benbow, M Eric; Robertson, B K; Javan, Gulnaz T

2016-04-01

Genomic studies have estimated there are approximately 10(3)-10(6) bacterial species per gram of soil. The microbial species found in soil associated with decomposing human remains (gravesoil) have been investigated and recognized as potential molecular determinants for estimates of time since death. The nascent era of high-throughput amplicon sequencing of the conserved 16S ribosomal RNA (rRNA) gene region of gravesoil microbes is allowing research to expand beyond more subjective empirical methods used in forensic microbiology. The goal of the present study was to evaluate microbial communities and identify taxonomic signatures associated with the gravesoil human cadavers. Using 16S rRNA gene amplicon-based sequencing, soil microbial communities were surveyed from 18 cadavers placed on the surface or buried that were allowed to decompose over a range of decomposition time periods (3-303 days). Surface soil microbial communities showed a decreasing trend in taxon richness, diversity, and evenness over decomposition, while buried cadaver-soil microbial communities demonstrated increasing taxon richness, consistent diversity, and decreasing evenness. The results show that ubiquitous Proteobacteria was confirmed as the most abundant phylum in all gravesoil samples. Surface cadaver-soil communities demonstrated a decrease in Acidobacteria and an increase in Firmicutes relative abundance over decomposition, while buried soil communities were consistent in their community composition throughout decomposition. Better understanding of microbial community structure and its shifts over time may be important for advancing general knowledge of decomposition soil ecology and its potential use during forensic investigations.

Biological soil crusts: Diminutive communities of potential global importance

USGS Publications Warehouse

Ferrenberg, Scott; Tucker, Colin; Reed, Sasha C.

2017-01-01

Biological soil crusts (biocrusts) are widespread, diverse communities of cyanobacteria, fungi, lichens, and mosses living on soil surfaces, primarily in drylands. Biocrusts can locally govern primary production, soil fertility, hydrology, and surface energy balance, with considerable variation in these functions across alternate community states. Further, these communities have been implicated in Earth system functioning via potential influences on global biogeochemistry and climate. Biocrusts are easily destroyed by disturbances and appear to be exceptionally vulnerable to warming temperatures and altered precipitation inputs, signaling possible losses of dryland functions with global change. Despite these concerns, we lack sufficient spatiotemporal data on biocrust function, cover, and community structure to confidently assess their ecological roles across the extensive dryland biome. Here, we present the case for cross-scale research and restoration efforts coupled with remote-sensing and modeling approaches that improve our collective understanding of biocrust responses to global change and the ecological roles of these diminutive communities at global scales.

Lunar vertical-shaft mining system

NASA Technical Reports Server (NTRS)

Introne, Steven D. (Editor); Krause, Roy; Williams, Erik; Baskette, Keith; Martich, Frederick; Weaver, Brad; Meve, Jeff; Alexander, Kyle; Dailey, Ron; White, Matt

1994-01-01

This report proposes a method that will allow lunar vertical-shaft mining. Lunar mining allows the exploitation of mineral resources imbedded within the surface. The proposed lunar vertical-shaft mining system is comprised of five subsystems: structure, materials handling, drilling, mining, and planning. The structure provides support for the exploration and mining equipment in the lunar environment. The materials handling subsystem moves mined material outside the structure and mining and drilling equipment inside the structure. The drilling process bores into the surface for the purpose of collecting soil samples, inserting transducer probes, or locating ore deposits. Once the ore deposits are discovered and pinpointed, mining operations bring the ore to the surface. The final subsystem is planning, which involves the construction of the mining structure.

Roughness of biopores and cracks in Bt-horizons by confocal laser scanning microscopy

NASA Astrophysics Data System (ADS)

Leue, Martin; Gerke, Horst H.

2016-04-01

During preferential flow events in structured soils, the movement of water and reactive solutes is mostly restricted to larger inter-aggregate pores, cracks, and biopores. The micro-topography of such macropores in terms of pore shapes, geometry, and roughness is crucial for describing the exchange of water and solutes between macropores and the soil matrix. The objective of this study was to determine the surface roughness of intact structural surfaces from the Bt-horizon of Luvisols by confocal laser scanning microscopy. For this purpose, samples with the structural surface types including cracks with and without clay-organic coatings from Bt-horizons developed on loess and glacial till were compared. The surface roughness of these structures was calculated in terms of three parameters from selected surface regions of 0.36 mm² determined with a confocal laser scanning microscope of the type Keyence VK-X100K. These data were evaluated in terms of the root-mean-squared roughness, Rq, the curvature, Rku, and the ratio between surface area and base area, RA. Values of Rq and RA were smaller for coated as compared to uncoated cracks and earthworm burrows of the Bt-horizons from both parent materials. The results indicated that the illuviation of clayey material led to a "smoothing" of the crack surfaces, which was similar for the coarser textured till-Bt and the finer-textured loess-Bt surfaces. The roughness indicated by Rq and RA values was only slightly smaller and that indicated by Rku slightly higher for the structural surfaces from the loess as compared to those from the glacial till. These results suggest a minor importance of the parent material on the roughness of structural surfaces in the Bt-horizon. The similarity of Rq, RA, and Rku values between surfaces of earthworm burrows and uncoated cracks did not confirm an expected smoothing effect of the burrow walls by the earthworm. In contrast to burrow walls, root channels from the loess-Bt were smoother than the surfaces of the other structure types, suggesting that the two types of biopores have to be distinguished when describing preferential flow and macropore-matrix exchange. Nevertheless, the confocal laser microscopy technique proved useful for characterizing the roughness of intact structural surfaces.

Standards for the Mobility Common Operational Picture (M-COP): Elements of Ground Vehicle Maneuver

DTIC Science & Technology

2007-07-01

saturated 0009 waterlogged 0010 wet Surface_Slippery Indication that a surface is slippery . Examples: wet grass, and wet clay soil. 1 boolean...Enumeration Values or Units† 0022 cypress 0023 deciduous_unspecified 0024 dry_crops 0025 elm 0026 eucalyptus 0027 evergreen_unspecified 0028 filao...internal structural material. 1 integer 0024 concrete_steel 0137 steel 0155 wood Surface_Slippery Indication that a surface is slippery

Nematode diversity, abundance and community structure 50 years after the formation of the volcanic island of Surtsey

NASA Astrophysics Data System (ADS)

Ilieva-Makulec, K.; Bjarnadottir, B.; Sigurdsson, B. D.

2014-10-01

The soil nematode fauna can give important insights into soil development and other habitat changes that occur during primary succession. We investigated the generic composition, density, distribution and community structure of nematodes 50 years after the formation of a pristine volcanic island, Surtsey, Iceland. Part of the island has received additional nutrient inputs from seagulls breeding there since 1985, while the reminder has been much less affected and is at present found at a different successional sere. In total, 25 genera of nematodes were identified, of which 14 were reported on Surtsey for the first time. Nematode communities were more diverse in the more infertile area outside the gull colony, where 24 genera were found, compared to 18 inside. The trophic structure of the nematode communities showed relatively higher abundance of fungal feeders in the infertile areas, but relatively more bacterial- and plant-feeders inside the colony. Nematode abundance in surface soil was, however, significantly higher within the gull colony, with 16.7 ind. cm-2 compared to 3.6 ind. cm-2 outside. A multivariate analysis indicated that the nematode abundance and distribution on Surtsey were most strongly related to the soil C : N ratio, soil acidity, plant cover and biomass, soil temperature and soil depth.

Namib Desert Soil Microbial Community Diversity, Assembly, and Function Along a Natural Xeric Gradient.

PubMed

Scola, Vincent; Ramond, Jean-Baptiste; Frossard, Aline; Zablocki, Olivier; Adriaenssens, Evelien M; Johnson, Riegardt M; Seely, Mary; Cowan, Don A

2018-01-01

The hyperarid Namib desert is a coastal desert in southwestern Africa and one of the oldest and driest deserts on the planet. It is characterized by a west/east increasing precipitation gradient and by regular coastal fog events (extending up to 75 km inland) that can also provide soil moisture. In this study, we evaluated the role of this natural aridity and xeric gradient on edaphic microbial community structure and function in the Namib desert. A total of 80 individual soil samples were collected at 10-km intervals along a 190-km transect from the fog-dominated western coastal region to the eastern desert boundary. Seventeen physicochemical parameters were measured for each soil sample. Soil parameters reflected the three a priori defined climatic/xeric zones along the transect ("fog," "low rain," and "high rain"). Microbial community structures were characterized by terminal restriction fragment length polymorphism fingerprinting and shotgun metaviromics, and their functional capacities were determined by extracellular enzyme activity assays. Both microbial community structures and activities differed significantly between the three xeric zones. The deep sequencing of surface soil metavirome libraries also showed shifts in viral composition along the xeric transect. While bacterial community assembly was influenced by soil chemistry and stochasticity along the transect, variations in community "function" were apparently tuned by xeric stress.

Variation of Desert Soil Hydraulic Properties with Pedogenic Maturity

NASA Astrophysics Data System (ADS)

Nimmo, J. R.; Perkins, K. S.; Mirus, B. B.; Schmidt, K. M.; Miller, D. M.; Stock, J. D.; Singha, K.

2006-12-01

Older alluvial desert soils exhibit greater pedogenic maturity, having more distinct desert pavements, vesicular (Av) horizons, and more pronounced stratification from processes such as illuviation and salt accumulation. These and related effects strongly influence the soil hydraulic properties. Older soils have been observed to have lower saturated hydraulic conductivity, and possibly greater capacity to retain water, but the quantitative effect of specific pedogenic features on the soil water retention or unsaturated hydraulic conductivity (K) curves is poorly known. With field infiltration/redistribution experiments on three different-aged soils developed within alluvial wash deposits in the Mojave National Preserve, we evaluated effective hydraulic properties over a scale of several m horizontally and to 1.5 m depth. We then correlated these properties with pedogenic features. The selected soils are (1) recently deposited sediments, (2) a soil of early Holocene age, and (3) a highly developed soil of late Pleistocene age. In each experiment we ponded water in a 1-m-diameter infiltration ring for 2.3 hr. For several weeks we monitored subsurface water content and matric pressure using surface electrical resistance imaging, dielectric-constant probes, heat-dissipation probes, and tensiometers. Analysis of these data using an inverse modeling technique gives the water retention and K properties needed for predictive modeling. Some properties show a consistent trend with soil age. Progressively more developed surface and near-surface features such as desert pavement and Av horizons are the likely cause of an observed consistent decline of infiltration capacity with soil age. Other properties, such as vertical flow retardation by layer contrasts, appear to have a more complicated soil-age dependence. The wash deposits display distinct depositional layering that has a retarding effect on vertical flow, an effect that may be less pronounced in the older Holocene soil, where the original depositional structure has a relatively modest influence. Anisotropy at the scale of centimeters is of major importance in the Pleistocene soil, with developed horizons that tend to hold water within about 0.5 m of the surface for a longer duration than in the two younger soils. Correlation of these and related pedogenic features with soil hydraulic properties is a first step toward the estimation of effective hydraulic properties of widely varying Mojave Desert soils, as needed for large-scale evaluation of soil moisture dynamics in relation to ecological habitat quality.

Estimating persistence of brominated and chlorinated organic pollutants in air, water, soil, and sediments with the QSPR-based classification scheme.

PubMed

Puzyn, T; Haranczyk, M; Suzuki, N; Sakurai, T

2011-02-01

We have estimated degradation half-lives of both brominated and chlorinated dibenzo-p-dioxins (PBDDs and PCDDs), furans (PBDFs and PCDFs), biphenyls (PBBs and PCBs), naphthalenes (PBNs and PCNs), diphenyl ethers (PBDEs and PCDEs) as well as selected unsubstituted polycyclic aromatic hydrocarbons (PAHs) in air, surface water, surface soil, and sediments (in total of 1,431 compounds in four compartments). Next, we compared the persistence between chloro- (relatively well-studied) and bromo- (less studied) analogs. The predictions have been performed based on the quantitative structure-property relationship (QSPR) scheme with use of k-nearest neighbors (kNN) classifier and the semi-quantitative system of persistence classes. The classification models utilized principal components derived from the principal component analysis of a set of 24 constitutional and quantum mechanical descriptors as input variables. Accuracies of classification (based on an external validation) were 86, 85, 87, and 75% for air, surface water, surface soil, and sediments, respectively. The persistence of all chlorinated species increased with increasing halogenation degree. In the case of brominated organic pollutants (Br-OPs), the trend was the same for air and sediments. However, we noticed that the opposite trend for persistence in surface water and soil. The results suggest that, due to high photoreactivity of C-Br chemical bonds, photolytic processes occurring in surface water and soil are able to play significant role in transforming and removing Br-OPs from these compartments. This contribution is the first attempt of classifying together Br-OPs and Cl-OPs according to their persistence, in particular, environmental compartments.

Spatial characterization of soil properties and influence in soil formation in oak-grassland of Sierra Morena, S Spain

NASA Astrophysics Data System (ADS)

Román-Sánchez, Andrea; Cáceres, Francisco; Pédèches, Remi; Giráldez Cervera, Juan Vicente; Vanwalleghem, Tom

2016-04-01

The Mediterranean oak-grassland ecosystem is very important for the rural economy and for the biodiversity of south-western European countries like Spain and Portugal. Nevertheless these ecosystems are not well characterized especially their soils. In this report soil carbon has been evaluated and related to other properties. The principal factors controlling the structure, productivity and evolution of forest ecosystems are bedrock, climate, relief, vegetation and time. Soil carbon has an important influence in the soil and ecosystem structures. The purpose of this study is to determine the relationship between relief, soil properties, spatial distribution of soil carbon and their influence in soil formation and geomorphology. This work is part of another study which aims to elucidate the processes involved in the soil formation and to examine their behaviour on long-term with a modelling. In our study area, located in oak-grassland of Sierra Morena, in Cordoba, S Spain, have been studied 67 points at 6 depths in 262 hectares in order to determine carbon content varying between 0-6%, soil properties such as soil depth between 0-4 m, horizon depth and the rocks amount in surface. The relationship between the soil carbon, soil properties and the relief characteristic like slope, aspect, curvature can shed light the processes that affect the mechanisms of bedrock weathering and their interrelationship with geomorphological processes.

One perspective on spatial variability in geologic mapping

USGS Publications Warehouse

Markewich, H.W.; Cooper, S.C.

1991-01-01

This paper discusses some of the differences between geologic mapping and soil mapping, and how the resultant maps are interpreted. The role of spatial variability in geologic mapping is addressed only indirectly because in geologic mapping there have been few attempts at quantification of spatial differences. This is largely because geologic maps deal with temporal as well as spatial variability and consider time, age, and origin, as well as composition and geometry. Both soil scientists and geologists use spatial variability to delineate mappable units; however, the classification systems from which these mappable units are defined differ greatly. Mappable soil units are derived from systematic, well-defined, highly structured sets of taxonomic criteria; whereas mappable geologic units are based on a more arbitrary heirarchy of categories that integrate many features without strict values or definitions. Soil taxonomy is a sorting tool used to reduce heterogeneity between soil units. Thus at the series level, soils in any one series are relatively homogeneous because their range of properties is small and well-defined. Soil maps show the distribution of soils on the land surface. Within a map area, soils, which are often less than 2 m thick, show a direct correlation to topography and to active surface processes as well as to parent material.

Earthworm impacts on organo-mineral interactions and soil carbon inventories in Fennoscandian boreal and sub-arctic landscapes

NASA Astrophysics Data System (ADS)

Wackett, Adrian; Yoo, Kyungsoo; Cameron, Erin; Klaminder, Jonatan

2017-04-01

Boreal and sub-arctic environments sustain some of the most pristine and fragile ecosystems in the world and house a disproportionate amount of the global soil carbon pool. Although the historical view of soil carbon turnover has focused on the intrinsic molecular structure of organic matter, recent work has highlighted the importance of stabilizing soil carbon on reactive mineral surfaces. However, the rates and mechanisms controlling these processes at high latitudes are poorly understood. Here we explored the biogeochemical impacts of deep-burrowing earthworm species on a range of Fennoscandian forest soils to investigate how earthworms impact soil carbon inventories and organo-mineral associations across boreal and sub-arctic landscapes. We sampled soils and earthworms at six sites spanning almost ten degrees latitude and encompassing a wide range of soil types and textures, permitting simultaneous consideration of how climate and mineralogy affect earthworm-mediated shifts in soil carbon dynamics. Across all sites, earthworms significantly decreased the carbon and nitrogen contents of the upper 10 cm, presumably through consumption of the humus layer and subsequent incorporation of the underlying mineral soil into upper organic horizons. Their mixing of humus and underlying soil also generally increased the proportion of mineral surface area occluded by organic matter, although the extent to which earthworms facilitate such organo-mineral interactions appears to be controlled by soil texture and mineralogy. This work indicates that quantitative measurements of mineral surface area and its extent of coverage by soil organic matter facilitate scaling up of molecular interactions between organic matter and minerals to the level of soil profiles and landscapes. Our preliminary data also strongly suggests that earthworms have profound effects on the fate of soil carbon and nitrogen in boreal and sub-arctic environments, highlighting the need for a better understanding of the joint ecological impacts of warming and indirect disturbances like earthworm introduction by humans to make sound predictions of future ecosystem change and carbon-climate feedbacks.

Pleistocene permafrost features in soils in the South-western Italian Alps

NASA Astrophysics Data System (ADS)

D'Amico, Michele; Catoni, Marcella; Bonifacio, Eleonora; Zanini, Ermanno

2015-04-01

Because of extensive Pleistocenic glaciations which erased most of the previously existing soils, slope steepness and climatic conditions favoring soil erosion, most soils observed on the Alps (and in other mid-latitude mountain ranges) developed only during the Holocene. However, in few sites, particularly in the outermost sections of the Alpine range, Pleistocene glaciers covered only small and scattered surfaces because of the low altitude reached in the basins, and ancient soils could be preserved for long periods of time on particularly stable surfaces. In some cases, these soils retain good memories of past periglacial activity. We described and sampled soils on stable surfaces in the Upper Tanaro valley, Ligurian Alps (Southwestern Piemonte, Italy). The sampling sites were between 600 to 1600 m of altitude, under present day lower montane Castanea sativa/Ostrya carpinifolia forests, montane Fagus sylvatica and Pinus uncinata forests or montane heath/grazed grassland, on different quartzitic substrata. The surface morphology often showed strongly developed, fossil periglacial patterned ground forms, such as coarse stone circles on flat surfaces, or stone stripes on steeper slopes. The stone circles could be up to 5 m wide, while the sorted stripes could be as wide as 12-15 m. A strong lateral cryogenic textural sorting characterized the fine fraction too, with sand dominating close to the stone rims of the patterned ground features and silt and clay the central parts. The surface 60-120 cm of the soils were podzolized during the Holocene; as a result of the textural lateral sorting, the thickness of the podzolic E and Bs horizons varied widely across the patterns. The lower boundary of the Holocene Podzols was abrupt, and corresponded with dense layers with thick coarse laminar structure and illuvial silt accumulation (Cjj horizons). Dense Cjj diapiric inclusions were sometimes preserved in the central parts of the patterns. Where cover beds were developed, more superimposed podzol cycles were observed: the deeper podzols, included in the dense layer, were strongly cryoturbated and showed convoluted horizons and buried organic horizons. The presence of the dense Cjj horizons also influenced surface soil hydrology, which in turn influenced the expression of E and Bs horizons, in addition to textural lateral variability. In conclusion, surface morphology and soil properties evidence the presence of permafrost during cold Pleistocene phases, with an active layer 60-120 cm thick, associated with a particularly strong cryoturbation. However, all the permafrost features were not necessarily formed during the same periods, and dating of different materials would be necessary in order to obtain precise paleoenvironmental reconstructions of cold Quaternary phases in the Alps.

Collective Structural Changes in Vermiculite Clay Suspensions Induced by Cesium Ions

NASA Astrophysics Data System (ADS)

Motokawa, Ryuhei; Endo, Hitoshi; Yokoyama, Shingo; Nishitsuji, Shotaro; Kobayashi, Tohru; Suzuki, Shinichi; Yaita, Tsuyoshi

2014-10-01

Following the Fukushima Daiichi nuclear disaster in 2011, Cs radioisotopes have been dispersed over a wide area. Most of the Cs has remained on the surface of the soil because Cs+ is strongly adsorbed in the interlayer spaces of soil clays, particularly vermiculite. We have investigated the microscopic structure of an aqueous suspension of vermiculite clay over a wide length scale (1-1000 Å) by small-angle X-ray scattering. We determined the effect of the adsorption behavior of Cs+ on the structural changes in the clay. It was found that the abruption of the clay sheets was induced by the localization of Cs+ at the interlayer. This work provides important information for predicting the environmental fate of radioactive Cs in polluted areas, and for developing methods to extract Cs from the soil and reduce radioactivity.

Investigation of Expedient Ground Surfacing with a Glass Fiber-Resin Mixture by a Spray-Deposition Technique,

DTIC Science & Technology

PAVEMENTS, *REINFORCED PLASTICS), LANDING FIELDS, SPRAYS, GLASS TEXTILES, LAMINATED PLASTICS, TEST METHODS, FOUNDATIONS(STRUCTURES), SANDWICH CONSTRUCTION, SOILS, FEASIBILITY STUDIES, LOAD DISTRIBUTION

The Impact of Model and Rainfall Forcing Errors on Characterizing Soil Moisture Uncertainty in Land Surface Modeling

NASA Technical Reports Server (NTRS)

Maggioni, V.; Anagnostou, E. N.; Reichle, R. H.

2013-01-01

The contribution of rainfall forcing errors relative to model (structural and parameter) uncertainty in the prediction of soil moisture is investigated by integrating the NASA Catchment Land Surface Model (CLSM), forced with hydro-meteorological data, in the Oklahoma region. Rainfall-forcing uncertainty is introduced using a stochastic error model that generates ensemble rainfall fields from satellite rainfall products. The ensemble satellite rain fields are propagated through CLSM to produce soil moisture ensembles. Errors in CLSM are modeled with two different approaches: either by perturbing model parameters (representing model parameter uncertainty) or by adding randomly generated noise (representing model structure and parameter uncertainty) to the model prognostic variables. Our findings highlight that the method currently used in the NASA GEOS-5 Land Data Assimilation System to perturb CLSM variables poorly describes the uncertainty in the predicted soil moisture, even when combined with rainfall model perturbations. On the other hand, by adding model parameter perturbations to rainfall forcing perturbations, a better characterization of uncertainty in soil moisture simulations is observed. Specifically, an analysis of the rank histograms shows that the most consistent ensemble of soil moisture is obtained by combining rainfall and model parameter perturbations. When rainfall forcing and model prognostic perturbations are added, the rank histogram shows a U-shape at the domain average scale, which corresponds to a lack of variability in the forecast ensemble. The more accurate estimation of the soil moisture prediction uncertainty obtained by combining rainfall and parameter perturbations is encouraging for the application of this approach in ensemble data assimilation systems.

Characterising soil surface roughness with a frequency modulated polarimetric radar

NASA Astrophysics Data System (ADS)

Seeger, Manuel; Gronz, Oliver; Beiske, Joshua; Klein, Tobias

2014-05-01

Soil surface roughness is considered crucial for soil erosion as it determines the effective surface exposed to the raindrop impact. It regulates surface runoff velocity and it causes runoff concentration. But a comprehensive characterisation of the shape of the soils' surface is still difficult to achieve. Photographic systems and terrestrial laser-scanning are nowadays able to generate high resolution DEMs, but the derivation of roughness parameters is still not clear. Spaceborne radar systems are used for about 3 decades for earth survey. Spatial soil moisture distribution, ice sheet monitoring and earth-wide topographic survey are the main objectives of these radar systems, working generally with frequencies <10 GHz. Contrasting with this, technologies emitting frequencies up to 77 GHz are generally used for object tracking purposes. But it is known, that the reflection characteristics, such as intensity and polarisation, strongly depend on the properties of the target object. A new design of a frequency modulated continuous wave radar, emitting a right hand shaped circular polarization and receiving both polarization directions, right and left-hand shaped, is tested here for its ability to detect and quantify different surface roughness. The reflection characteristics of 4 different materials 1) steel, 2) sand (0,5-1 mm), 3) fine (2-4 mm) and 4) coarse (15-30 mm) rock-fragments and different roughness as well as moisture content are analysed. In addition, the signals are taken at 2 different angles to the soil's surface (90° and 70°). For quantification of the roughness, a photographic method (Structure-from-Motion) is applied to generate a detailed DEM and random roughness (RR) is calculated. To characterise the radar signal, different ratios of the reflected channels and polarisations are calculated. The signals show differences for all substrates, also clearly visible between sand and fine rock fragments, despite a wavelength of 1 cm of the electromagnetic waves. A systematic change of the signals with changing roughness is also observed. Measurements show a significant influence of the angle of observation. Soil moisture shows also an influence on the reflected signal, but is quite well differentiable to the effects of the shape of the soil's surface. The results show that polarimetric radar technology may be suitable to characterise the surface of soils, but still faces a big lack of knowledge on how to quantify and differentiate the different signals, how to handle variable observation angles, and finally how to characterise roughness.

Effect of freeze-thaw cycles on greenhouse gas fluxes from peat soils

NASA Astrophysics Data System (ADS)

Oh, H. D.; Rezanezhad, F.; Markelov, I.; McCarter, C. P. R.; Van Cappellen, P.

2017-12-01

The ongoing displacement of climate zones by global warming is increasing the frequency and intensity of freeze-thaw cycles in middle and high latitude regions, many of which are dominated by organic soils such as peat. Repeated freezing and thawing of soils changes their physical properties, geochemistry, and microbial community structure, which together govern the biogeochemical cycling of carbon and nutrients. In this presentation, we focus on how freeze-thaw cycles influence greenhouse gas fluxes from peat using a newly developed experimental soil column system that simulates realistic soil temperature profiles during freeze-thaw cycles. We measured the surface and subsurface changes to gas and aqueous phase chemistry to delineate the diffusion pathways and quantify soil greenhouse gas fluxes during freeze-thaw cycles using sulfur hexafluoride (SF6) as a conservative tracer. Three peat columns were assembled inside a temperature controlled chamber with different soil structures. All three columns were packed with 40 cm of undisturbed, slightly decomposed peat, where the soil of two columns had an additional 10 cm layer on top (one with loose Sphagnum moss and one with an impermeable plug). The results indicate that the release of SF6 and CO2 gas from the soil surface was influenced by the recurrent development of a physical ice barrier, which prevented gas exchange between the soil and atmosphere during freezing conditions. With the onset of thawing a pulse of SF6 and CO2 occurred, resulting in a flux of 3.24 and 2095.52 µmol/m2h, respectively, due to the build-up of gases in the liquid-phase pore space during freezing. Additionally, we developed a model to determine the specific diffusion coefficients for each peat column. These data allow us to better predict how increased frequency and intensity of freeze-thaw cycles will affect greenhouse gas emissions in northern peat soils.

Spatial Variability of PAHs and Microbial Community Structure in Surrounding Surficial Soil of Coal-Fired Power Plants in Xuzhou, China

PubMed Central

Ma, Jing; Zhang, Wangyuan; Chen, Yi; Zhang, Shaoliang; Feng, Qiyan; Hou, Huping; Chen, Fu

2016-01-01

This work investigated the spatial profile and source analysis of polycyclic aromatic hydrocarbons (PAHs) in soil that surrounds coal-fired power plants in Xuzhou, China. High-throughput sequencing was employed to investigate the composition and structure of soil bacterial communities. The total concentration of 15 PAHs in the surface soils ranged from 164.87 to 3494.81 μg/kg dry weight. The spatial profile of PAHs was site-specific with a concentration of 1400.09–3494.81 μg/kg in Yaozhuang. Based on the qualitative and principal component analysis results, coal burning and vehicle emission were found to be the main sources of PAHs in the surface soils. The phylogenetic analysis revealed differences in bacterial community compositions among different sampling sites. Proteobacteria was the most abundant phylum, while Acidobacteria was the second most abundant. The orders of Campylobacterales, Desulfobacterales and Hydrogenophilales had the most significant differences in relative abundance among the sampling sites. The redundancy analysis revealed that the differences in bacterial communities could be explained by the organic matter content. They could also be explicated by the acenaphthene concentration with longer arrows. Furthermore, OTUs of Proteobacteria phylum plotted around particular samples were confirmed to have a different composition of Proteobacteria phylum among the sample sites. Evaluating the relationship between soil PAHs concentration and bacterial community composition may provide useful information for the remediation of PAH contaminated sites. PMID:27598188

Spatial Variability of PAHs and Microbial Community Structure in Surrounding Surficial Soil of Coal-Fired Power Plants in Xuzhou, China.

PubMed

Ma, Jing; Zhang, Wangyuan; Chen, Yi; Zhang, Shaoliang; Feng, Qiyan; Hou, Huping; Chen, Fu

2016-09-02

This work investigated the spatial profile and source analysis of polycyclic aromatic hydrocarbons (PAHs) in soil that surrounds coal-fired power plants in Xuzhou, China. High-throughput sequencing was employed to investigate the composition and structure of soil bacterial communities. The total concentration of 15 PAHs in the surface soils ranged from 164.87 to 3494.81 μg/kg dry weight. The spatial profile of PAHs was site-specific with a concentration of 1400.09-3494.81 μg/kg in Yaozhuang. Based on the qualitative and principal component analysis results, coal burning and vehicle emission were found to be the main sources of PAHs in the surface soils. The phylogenetic analysis revealed differences in bacterial community compositions among different sampling sites. Proteobacteria was the most abundant phylum, while Acidobacteria was the second most abundant. The orders of Campylobacterales, Desulfobacterales and Hydrogenophilales had the most significant differences in relative abundance among the sampling sites. The redundancy analysis revealed that the differences in bacterial communities could be explained by the organic matter content. They could also be explicated by the acenaphthene concentration with longer arrows. Furthermore, OTUs of Proteobacteria phylum plotted around particular samples were confirmed to have a different composition of Proteobacteria phylum among the sample sites. Evaluating the relationship between soil PAHs concentration and bacterial community composition may provide useful information for the remediation of PAH contaminated sites.

Analysis of factors controlling soil phosphorus loss with surface runoff in Huihe National Nature Reserve by principal component and path analysis methods.

PubMed

He, Jing; Su, Derong; Lv, Shihai; Diao, Zhaoyan; Bu, He; Wo, Qiang

2018-01-01

Phosphorus (P) loss with surface runoff accounts for the P input to and acceleration of eutrophication of the freshwater. Many studies have focused on factors affecting P loss with surface runoff from soils, but rarely on the relationship among these factors. In the present study, rainfall simulation on P loss with surface runoff was conducted in Huihe National Nature Reserve, in Hulunbeier grassland, China, and the relationships between P loss with surface runoff, soil properties, and rainfall conditions were examined. Principal component analysis and path analysis were used to analyze the direct and indirect effects on P loss with surface runoff. The results showed that P loss with surface runoff was closely correlated with soil electrical conductivity, soil pH, soil Olsen P, soil total nitrogen (TN), soil total phosphorus (TP), and soil organic carbon (SOC). The main driving factors which influenced P loss with surface runoff were soil TN, soil pH, soil Olsen P, and soil water content. Path analysis and determination coefficient analysis indicated that the standard multiple regression equation for P loss with surface runoff and each main factor was Y = 7.429 - 0.439 soil TN - 6.834 soil pH + 1.721 soil Olsen-P + 0.183 soil water content (r = 0.487, p < 0.01, n = 180). Soil TN, soil pH, soil Olsen P, and soil water content and the interactions between them were the main factors affecting P loss with surface runoff. The effect of physical and chemical properties of undisturbed soils on P loss with surface runoff was discussed, and the soil water content and soil Olsen P were strongly positive influences on the P loss with surface runoff.

Impact of drainage on wettability of fen peat-moorsh soils

NASA Astrophysics Data System (ADS)

Szajdak, L.; Szatyłowicz, J.; Brandyk, T.

2009-04-01

High water retention in peat is attributed to structural voids (macro-pores) due to the partial degradation of the structure of peat-forming plants, and molecular absorption sites (micro-pores) associated with the formation of humic substances. Water retention by the heterogeneously-structured system in peat organic matter depends on the chemical structure of solid surfaces. These naturally wet solids, if dried sufficiently, lose the ability to rewet quickly when immersed in water. The ability of peat surfaces to attract and hold water is attributed to hydrophilic functional groups which characterize the organic substances of peat. The investigations of chemical and physical properties were performed for three different peat-moorsh soils located in the Biebrza River Valley in Poland. All examined soils were used as meadow. Soil samples were taken from two depths: 5-10 cm (moorsh) and 50-80 cm (peat). Total organic carbon (TOC), dissolved organic carbon (DOC) and humic acids (HA) extracted from these samples were analysed. Also basic physical properties such as ash content and bulk density were measured. Wetting behavior of soils was quantified using water drop penetration time test (WDPT) and measured values of the soil-water contact angle using sessile drop method. The measurements were conducted on air-dry soil samples which volumetric moisture content was not exceeding 7%. The significant differences in the concentrations of TOC, DOC and properties of HA between two investigated depth of among peat and moorsh samples were observed. The measured concentrations of total organic carbon in the considered soils ranged from 37.2 to 45.6%. Generally, the decrease of total organic carbon concentration with depth of profiles was observed. The contents of dissolved organic carbon in the soils ranged from 5.3 to 19.4%. The quantities of dissolved organic carbon decreased simultaneously with E4/E6 values and with the depth of the soil profiles. For the investigated peat's, an increase of the depth is accompanied by the decrease in the degree of humification or an increase in chemical maturity of HA. The measured values of the contact angle for investigated soils were in the range from 81.4˚ to 114.3˚ what indicates their high water repellency. The WDPT was positively correlated with total organic carbon, organic matter and humic acids content while ash content, soil bulk density, pH and absorbance were correlated negatively. The highest value of correlation coefficient (statistically significant) was obtained for relation between WDPT and ash content. The soil water contact angle was less correlated with peat-moorsh soil properties in comparison with WDPT with one exception pH. The pH against the contact angle indicates tendency of increasing the contact angle with decreasing pH.

Impacts of single and recurrent wildfires on topsoil moisture regime

NASA Astrophysics Data System (ADS)

González-Pelayo, Oscar; Malvar, Maruxa; van den Elsen, Erik; Hosseini, Mohammadreza; Coelho, Celeste; Ritsema, Coen; Bautista, Susana; Keizer, Jacob

2017-04-01

The increasing fire recurrence on forest in the Mediterranean basin is well-established by future climate scenarios due to land use changes and climate predictions. By this, shifts on mature pine woodlands to shrub rangelands are of major importance on forest ecosystems buffer functions, since historical patterns of established vegetation help to recover from fire disturbances. This fact, together with the predicted expansion of the drought periods, will affect feedback processes of vegetation patterns since water availability on these seasons are driven by post-fire local soil properties. Although fire impacts of soil properties and water availability has been widely studied using the fire severity as the main factor, little research is developed on post-fire soil moisture patterns, including the fire recurrence as a key explanatory variable. The following research investigated, in pine woodlands of north central Portugal, the short-term consequences (one year after a fire) of wildfire recurrence on the surface soil moisture content (SMC) and on effective soil water (SWEFF, parameter that includes actual daily soil moisture, soil field capacity-FC and permanent wilting point-PWP). The study set-up includes analyses at two fire recurrence scenarios (1x- and 4x-burnt since 1975), at a patch level (shrub patch/interpatch) and at two soil depths (2.5 and 7.5 cm) in a nested approach. Understanding how fire recurrence affects water in soil over space and time is the main goal of this research. The use of soil moisture sensors in a nested approach, the rainfall features and analyses on basic soil properties as soil organic matter, texture, bulk density, pF curves, soil water repellency and soil surface components will establish which factors has the largest role in controlling soil moisture behavior. Main results displayed, in a seasonal and yearly basis, no differences on SMC as increasing fire recurrence (1x- vs 4x-burnt) neither between patch/interpatch microsites at both two soil depths. Otherwise, in a yearly basis and during soil drying cycles, it was found less effective water on soil at the surface layers of the 4x-burnt and between shrub interpatches, based on the worst soil hydrological conditions (PWP) and the increasing percentage of abiotic soil surface components as increasing fire recurrence. Our results suggest that the inclusion of soil hydrological properties, as pF-curves, on the soil water effectiveness calculation seems to be a better indicator of water availability that volumetric SM per se. Otherwise, the use of a nested approach methodology, stresses how fire recurrence, expected increases in the summer drought spells and, the increasing dominance of abiotic soil surface components, are the factors that much influence soil eco-hydrological functioning in fire prone ecosystems. Furthermore, this research point out how post-fire soil structural quality into plant interpatches could provoke looping feedback processes triggering desertification situations also in humid Mediterranean forestlands.

Vegetation effects on soil water erosion rates and nutrient losses at Santa Catarina highlands, south Brazil

NASA Astrophysics Data System (ADS)

Bertol, I.; Barbosa, F. T.; Vidal Vázquez, E.; Paz Ferreiro, J.

2009-04-01

Water erosion involves three main processes: detachment, transport and deposition of soil particles. The main factors affecting water erosion are rainfall, soil, topography, soil management and land cover and use. Soil erosion potential is increased if the soil has no or very little vegetative cover of plants and/or crop residues, whereas plant and residue cover substantially decrease rates of soil erosion. Plant and residue cover protects the soil from raindrop impact and splash, tends to slow down the movement of surface runoff and allows excess surface water to infiltrate. Moreover, plant and residue cover improve soil physical, chemical and biological properties. Soils with improved structure have a greater resistance to erosion. By contrast, accelerated soil erosion is accentuated by deforestation, biomass burning, plowing and disking, cultivation of open-row crops, etc. The erosion-reducing effectiveness of plant and/or residue covers depends on the type, extent and quantity of cover. Vegetation and residue combinations that completely cover the soil are the most efficient in controlling soil. Partially incorporated residues and residual roots are also important, as these provide channels that allow surface water to move into the soil. The effectiveness of any crop, management system or protective cover also depends on how much protection is available at various periods during the year, relative to the amount of erosive rainfall that falls during these periods. Most of the erosion on annual row crop land can be reduced by leaving a residue cover greater after harvest and over the winter months, or by inter-seeding a forage crop. Soil erosion potential is also affected by tillage operations and tillage system. Conservation tillage reduces water erosion in relation to conventional tillage by increasing soil cover and soil surface roughness. Here, we review the effect of vegetation on soil erosion in the Santa Catarina highlands, south of Brazil, under subtropical climatic conditions. The area cropped under no tillage in Brazil has increased rapidly since 1990, especially in the southern region. This practice was first introduced in the 1970s as a strategy to control soil erosion and continuous declines in land productivity under conventional tillage systems. No tillage almost entirely keeps the previous crop residue on the surface. In the last 15 years soil and water losses by water erosion have been quantified for different soil tillage systems, diverse crop rotations and successive crop stages under simulated and natural rain conditions. Plot experiments showed that soil losses under no tillage systems with a vegetative cover were 98% lower when compared with conventionally tilled bare soil. Moreover water losses were 60% lower for these conditions. Conventional tillage (plowing + harrowing) in the presence of vegetative cover reduced soil losses and water losses by 80% and 50%, respectively, taken the uncultivated bare soil as a reference. The review includes the effect of vegetative cover on nutrient losses at the studied sites in the Santa Catarina highlands.

Investigating Forest Soil Disturbance with Different Timber Harvesting Operations in South Korea

NASA Astrophysics Data System (ADS)

Im, Sangjun; Lee, Eunjai; Eu, Song; Han, Sang-Kyun

2017-04-01

Forest operation such as timber harvesting can influence to forest environment by displacing soil particles, compacting surface layers, and destroying soil structures. This results in increased surface runoff and associated soil erosion during rainy season, due to soil disturbance. The extent of soil disturbance depends on the skidding/yarding method, types of machine used, and soil types. In South Korea, cut-to-length (CTL) operation is traditionally used by excavator with grapple in most areas. Recently, whole-tree (WT) harvesting system by swing yarder has gained considerable attention as an alternative traditional extraction method. The objectives of this study were to describe the effects of two different harvesting methods (CTL and WT) on soil disturbance and soil physical properties. After the CTL observation, we found that severe disturbed soils and compacted area were more than WT. Rutting was influenced more than 50% of the deep disturbance classes by the uphill climbing and downhill extraction method, while exposing bare soil was most disturbance in WT operation. Soil physical properties were influenced considerably by the number of excavator passes and slash residual classes in both units. The results from the study would be useful for understanding soil disturbance influence by timber harvesting in Korea. But, more detailed observations are needed to accurately estimate erosion rates and sediment delivery associated with forest management and operation. Acknowledgements. This study was carried out with the support of 'R&D Program for Forestry Technology (Project No. S211316L020110)' provided by Korea Forest Service.

Geochemical soil sampling for deeply-buried mineralized breccia pipes, northwestern Arizona

USGS Publications Warehouse

Wenrich, K.J.; Aumente-Modreski, R. M.

1994-01-01

Thousands of solution-collapse breccia pipes crop out in the canyons and on the plateaus of northwestern Arizona; some host high-grade uranium deposits. The mineralized pipes are enriched in Ag, As, Ba, Co, Cu, Mo, Ni, Pb, Sb, Se, V and Zn. These breccia pipes formed as sedimentary strata collapsed into solution caverns within the underlying Mississippian Redwall Limestone. A typical pipe is approximately 100 m (300 ft) in diameter and extends upward from the Redwall Limestone as much as 1000 m (3000 ft). Unmineralized gypsum and limestone collapses rooted in the Lower Permian Kaibab Limestone or Toroweap Formation also occur throughout this area. Hence, development of geochemical tools that can distinguish these unmineralized collapse structures, as well as unmineralized breccia pipes, from mineralized breccia pipes could significantly reduce drilling costs for these orebodies commonly buried 300-360 m (1000-1200 ft) below the plateau surface. Design and interpretation of soil sampling surveys over breccia pipes are plagued with several complications. (1) The plateau-capping Kaibab Limestone and Moenkopi Formation are made up of diverse lithologies. Thus, because different breccia pipes are capped by different lithologies, each pipe needs to be treated as a separate geochemical survey with its own background samples. (2) Ascertaining true background is difficult because of uncertainties in locations of poorly-exposed collapse cones and ring fracture zones that surround the pipes. Soil geochemical surveys were completed on 50 collapse structures, three of which are known mineralized breccia pipes. Each collapse structure was treated as an independent geochemical survey. Geochemical data from each collapse feature were plotted on single-element geochemical maps and processed by multivariate factor analysis. To contrast the results between geochemical surveys (collapse structures), a means of quantifying the anomalousness of elements at each site was developed. This degree of anomalousness, named the "correlation value", was used to rank collapse features by their potential to overlie a deeply-buried mineralized breccia pipe. Soil geochemical results from the three mineralized breccia pipes (the only three of the 50 that had previously been drilled) show that: (1) Soils above the SBF pipe contain significant enrichment of Ag, Al, As, Ba, Ga, K, La, Mo, Nd, Ni, Pb, Sc, Th, U and Zn, and depletion in Ca, Mg and Sr, in contrast to soils outside the topographic and structural rim; (2) Soils over the inner treeless zone of the Canyon pipe show Mo and Pb enrichment anf As and Ga depletion, in contrast to soils from the surrounding forest; and (3) The soil survey of the Mohawk Canyon pipe was a failure because of the rocky terrane and lack of a B soil horizon, or because the pipe plunges. At least 11 of the 47 other collapse structures studied contain anomalous soil enrichments similar to the SBF uranium ore-bearing pipe, and thus have good potential as exploration targets for uranium. One of these 11, #1102, does contain surface mineralized rock. These surveys suggest that soil geochemical sampling is a useful tool for the recognition of many collapse structures with underlying ore-bearing breccia pipes. ?? 1994.

Topographic changes detection through Structure-from-Motion in agricultural lands affected by erosion processes

NASA Astrophysics Data System (ADS)

Prosdocimi, Massimo; Pradetto Sordo, Nicoletta; Burguet, Maria; Di Prima, Simone; Terol Esparza, Enric; Tarolli, Paolo; Cerdà, Artemi

2016-04-01

Throughout the world, soil erosion by water is a serious problem, especially in semi-arid and semi-humid areas (Cerdà et al., 2009; Cerdan et al., 2010; García-Ruiz, 2010). Although soil erosion by water consists of physical processes that vary significantly in severity and frequency according to when and where they occur, they are also strongly influenced by anthropic factors such as land-use changes on large scales and unsustainable farming practices (Boardman et al., 1990; Cerdà 1994; Montgomery, 2007). Tillage operations, combined with weather conditions, are recognized to primarily influence soil erosion rates. If, on one hand, tillage operations cause uniform changes based on the tool used, on the other, weather conditions, such as rainfalls, produce more random changes, less easily traceable (Snapir et al., 2014). Within this context, remote-sensing technologies can facilitate the detection and quantification of these topographic changes. In particular, a real opportunity and challenge is offered by the low-cost and flexible photogrammetric technique, called 'Structure-from-Motion' (SfM), combined with the use of smartphones (Micheletti et al., 2014; Prosdocimi et al., 2015). This represents a significant advance compared with more expensive technologies and applications (e.g. Terrestrial Laser Scanner - TLS) (Tarolli, 2014). This work wants to test the Structure from Motion to obtain high-resolution topography for the detection of topographic changes in agricultural lands affected by erosion processes. Two case studies were selected: i) a tilled plot characterized by bare soil and affected by rill erosion located in the hilly countryside of Marche region (central Italy), and ii) a Mediterranean vineyard located within the province of Valencia (south eastern Spain) where rainfall simulation experiments were carried out. Extensive photosets were obtained by using one standalone reflex digital camera and one smartphone built-in digital camera. Digital Terrain Models (DTMs) derived from the smartphone reveled to be comparable to DTMs derived from the reflex camera. The results underlined the effectiveness of SfM for detecting topographic changes in agricultural lands affected by erosion processes, even when pictures are taken from a smartphone. This methodology could be very useful for farmers and/or technician for post-event analyses of erosion processes to implement technical measures to mitigate the problem of soil erosion by water. Acknowledgements The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement n° 603498 (RECARE project) References Boardman, J., Foster, I.D.L., Dearing, J.A., 1990. Soil Erosion on Agricultural Land. John Wiley and Sons Ltd., Chichester. Cerdà, A., 1994. The response of abandoned terraces to simulated rain, in: Rickson, R.J., (Ed.), Conserving Soil Resources: European Perspective, CAB International, Wallingford, pp. 44-55. Cerdà, A., Flanagan, D.C., Le Bissonnais, Y., Boardman, J., 2009. Soil erosion and agriculture. Soil & Tillage Research 106, 107-108. Cerdan, O., Govers, G., Le Bissonnais, Y., Van Oost, K., Poesen, J., Saby, N., Gobin, A., Vacca, A., Quinton, J., Auerwald, K., Klik, A., Kwaad, F.J.P.M., Raclot, D., Ionita, I., Rejman, J., Rousseva, S., Muxart, T., Roxo, M.J., Dostal, T., 2010. Rates and spatial variations of soil erosion in Europe: A study based on erosion plot data. Geomorphology 122, 167-177. Garcìa-Ruiz, J.M., 2010. The effects of land uses on soil erosion in Spain: A review. Catena 81, 1-11. Micheletti, N., Chandler, J.H., Lane, S.N., 2014. Investigating the geomorphological potential of freely available and accessible Structure-from-Motion photogrammetry using a smartphone. Earth Surface Processes and Landforms 40(4), 473-486. DOI: 10.1002/esp.3648 Montgomery, D.R., 2007. Soil erosion and agricultural sustainability. PNAS 104, 13268-13272. Prosdocimi, M., Calligaro, S., Sofia, G., Dalla Fontana, G., Tarolli, P., 2015. Bank rosion in agricultural drainage networks: new challenges from structure-from-motion photogrammetry for post-event analysis. Earth Surface Prosses and Landform 40(14), 1891-1906. DOI: 10.1002/esp.3767. Snapir, B., Hobbs, S., Waine, T.W., 2014. Roughness measurements over an agricultural soil surface with Structure from Motion. ISPRS Journal of Photogrammetry and Remote Sensing 96, 210-223. Tarolli, P., 2014. High-resolution topography for understanding Earth surface processes: opportunities and challenges. Geomorphology 216, 295-312.

Changes in microbial structure and functional communities at different soil depths during 13C labelled root litter degradation

NASA Astrophysics Data System (ADS)

Sanaullah, Muhammad; Baumann, Karen; Chabbi, Abad; Dignac, Marie-France; Maron, Pierre-Alain; Kuzyakov, Yakov; Rumpel, Cornelia

2014-05-01

Soil organic matter turnover depends on substrate quality and microbial activity in soil but little is known about how addition of freshly added organic material modifies the diversity of soil microbial communities with in a soil profile. We took advantage of a decomposition experiment, which was carried out at different soil depths under field conditions and sampled litterbags with 13C-labelled wheat roots, incubated in subsoil horizons at 30, 60 and 90 cm depth for up to 36 months. The effect of root litter addition on microbial community structure, diversity and activity was studied by determining total microbial biomass, PLFA signatures, molecular tools (DNA genotyping and pyrosequencing of 16S and 18S rDNAs) and extracellular enzyme activities. Automated ribosomal intergenic spacer analysis (ARISA) was also carried out to determine the differences in microbial community structure. We found that with the addition of root litter, total microbial biomass as well as microbial community composition and structure changed at different soil depths and change was significantly higher at top 30cm soil layer. Moreover, in the topsoil, population of both gram-positive and gram-negative bacteria increased with root litter addition over time, while subsoil horizons were relatively dominated by fungal community. Extra-cellular enzyme activities confirmed relatively higher fungal community at subsoil horizons compared with surface soil layer with bacteria dominant microbial population. Bacterial-ARISA profiling illustrated that the addition of root litter enhanced the abundance of Actinobacteria and Proteobacteria, at all three soil depths. These bacteria correspond to copiotrophic attributes, which can preferentially consume of labile soil organic C pools. While disappearance of oligotrophic Acidobacteria confirmed the shifting of microbial communities due to the addition of readily available substrate. We concluded that root litter mixing altered microbial community development which was soil horizon specific and its effects on soil microbial activity may impact on nutrient cycling.

The SMAP Level 4 Surface and Root-zone Soil Moisture (L4_SM) Product

NASA Technical Reports Server (NTRS)

Reichle, Rolf; Crow, Wade; Koster, Randal; Kimball, John

2010-01-01

The Soil Moisture Active and Passive (SMAP) mission is being developed by NASA for launch in 2013 as one of four first-tier missions recommended by the U.S. National Research Council Committee on Earth Science and Applications from Space in 2007. The primary science objectives of SMAP are to enhance understanding of land surface controls on the water, energy and carbon cycles, and to determine their linkages. Moreover, the high resolution soil moisture mapping provided by SMAP has practical applications in weather and seasonal climate prediction, agriculture, human health, drought and flood decision support. In this paper we describe the assimilation of SMAP observations for the generation of the planned SMAP Level 4 Surface and Root-zone Soil Moisture (L4_SM) product. The SMAP mission makes simultaneous active (radar) and passive (radiometer) measurements in the 1.26-1.43 GHz range (L-band) from a sun-synchronous low-earth orbit. Measurements will be obtained across a 1000 km wide swath using conical scanning at a constant incidence angle (40 deg). The radar resolution varies from 1-3 km over the outer 70% of the swath to about 30 km near the center of the swath. The radiometer resolution is 40 km across the entire swath. The radiometer measurements will allow high-accuracy but coarse resolution (40 km) measurements. The radar measurements will add significantly higher resolution information. The radar is however very sensitive to surface roughness and vegetation structure. The combination of the two measurements allows optimal blending of the advantages of each instrument. SMAP directly observes only surface soil moisture (in the top 5 cm of the soil column). Several of the key applications targeted by SMAP, however, require knowledge of root zone soil moisture (approximately top 1 m of the soil column), which is not directly measured by SMAP. The foremost objective of the SMAP L4_SM product is to fill this gap and provide estimates of root zone soil moisture that are informed by and consistent with SMAP observations. Such estimates are obtained by merging SMAP observations with estimates from a land surface model in a soil moisture data assimilation system. The land surface model component of the assimilation system is driven with observations-based surface meteorological forcing data, including precipitation, which is the most important driver for soil moisture. The model also encapsulates knowledge of key land surface processes, including the vertical transfer of soil moisture between the surface and root zone reservoirs. Finally, the model interpolates and extrapolates SMAP observations in time and in space. The L4_SM product thus provides a comprehensive and consistent picture of land surface hydrological conditions based on SMAP observations and complementary information from a variety of sources. The assimilation algorithm considers the respective uncertainties of each component and yields a product that is superior to satellite or model data alone. Error estimates for the L4_SM product are generated as a by-product of the data assimilation system.

Sorption, photodegradation, and chemical transformation of naproxen and ibuprofen in soils and water.

PubMed

Vulava, Vijay M; Cory, Wendy C; Murphey, Virginia L; Ulmer, Candice Z

2016-09-15

Pharmaceutically active compounds (PhACs) are released into the environment where they undergo soil sorption, photodegradation, and chemical transformation into structurally similar compounds. Here we report on studies of naproxen (NAP) and ibuprofen (IBP), two widely-used nonsteroidal anti-inflammatory drugs (NSAIDS), in soils and water. Organic matter (OM) was observed to play an important role in each of these processes. Sorption was observed to be stronger and nonlinear in higher OM soils while weaker but still significant in lower OM, higher clay soils; the amphiphilic nature of these two PhACs combined with the complex charged and nonpolar surfaces available in the soil was observed to control the sorption behavior. Simulated solar photodegradation rates of NAP and IBP in water were observed to change in the presence of humic acid or fulvic acid. Structural analogs of each compound were observed as the result of chemical transformation in both photoexposed aqueous solutions and non-photoexposed soil. Two of these transformation products were detected as both soil and photo transformation products for both PhACs. OM was observed to influence the chemical transformation of both pharmaceuticals. Copyright © 2016 Elsevier B.V. All rights reserved.

Inferring Land Surface Model Parameters for the Assimilation of Satellite-Based L-Band Brightness Temperature Observations into a Soil Moisture Analysis System

NASA Technical Reports Server (NTRS)

Reichle, Rolf H.; De Lannoy, Gabrielle J. M.

2012-01-01

The Soil Moisture and Ocean Salinity (SMOS) satellite mission provides global measurements of L-band brightness temperatures at horizontal and vertical polarization and a variety of incidence angles that are sensitive to moisture and temperature conditions in the top few centimeters of the soil. These L-band observations can therefore be assimilated into a land surface model to obtain surface and root zone soil moisture estimates. As part of the observation operator, such an assimilation system requires a radiative transfer model (RTM) that converts geophysical fields (including soil moisture and soil temperature) into modeled L-band brightness temperatures. At the global scale, the RTM parameters and the climatological soil moisture conditions are still poorly known. Using look-up tables from the literature to estimate the RTM parameters usually results in modeled L-band brightness temperatures that are strongly biased against the SMOS observations, with biases varying regionally and seasonally. Such biases must be addressed within the land data assimilation system. In this presentation, the estimation of the RTM parameters is discussed for the NASA GEOS-5 land data assimilation system, which is based on the ensemble Kalman filter (EnKF) and the Catchment land surface model. In the GEOS-5 land data assimilation system, soil moisture and brightness temperature biases are addressed in three stages. First, the global soil properties and soil hydraulic parameters that are used in the Catchment model were revised to minimize the bias in the modeled soil moisture, as verified against available in situ soil moisture measurements. Second, key parameters of the "tau-omega" RTM were calibrated prior to data assimilation using an objective function that minimizes the climatological differences between the modeled L-band brightness temperatures and the corresponding SMOS observations. Calibrated parameters include soil roughness parameters, vegetation structure parameters, and the single scattering albedo. After this climatological calibration, the modeling system can provide L-band brightness temperatures with a global mean absolute bias of less than 10K against SMOS observations, across multiple incidence angles and for horizontal and vertical polarization. Third, seasonal and regional variations in the residual biases are addressed by estimating the vegetation optical depth through state augmentation during the assimilation of the L-band brightness temperatures. This strategy, tested here with SMOS data, is part of the baseline approach for the Level 4 Surface and Root Zone Soil Moisture data product from the planned Soil Moisture Active Passive (SMAP) satellite mission.

Experimental study on soluble chemical transfer to surface runoff from soil.

PubMed

Tong, Juxiu; Yang, Jinzhong; Hu, Bill X; Sun, Huaiwei

2016-10-01

Prevention of chemical transfer from soil to surface runoff, under condition of irrigation and subsurface drainage, would improve surface water quality. In this paper, a series of laboratory experiments were conducted to assess the effects of various soil and hydraulic factors on chemical transfer from soil to surface runoff. The factors include maximum depth of ponding water on soil surface, initial volumetric water content of soil, depth of soil with low porosity, type or texture of soil and condition of drainage. In the experiments, two soils, sand and loam, mixed with different quantities of soluble KCl were filled in the sandboxes and prepared under different initial saturated conditions. Simulated rainfall induced surface runoff are operated in the soils, and various ponding water depths on soil surface are simulated. Flow rates and KCl concentration of surface runoff are measured during the experiments. The following conclusions are made from the study results: (1) KCl concentration in surface runoff water would decrease with the increase of the maximum depth of ponding water on soil surface; (2) KCl concentration in surface runoff water would increase with the increase of initial volumetric water content in the soil; (3) smaller depth of soil with less porosity or deeper depth of soil with larger porosity leads to less KCl transfer to surface runoff; (4) the soil with finer texture, such as loam, could keep more fertilizer in soil, which will result in more KCl concentration in surface runoff; and (5) good subsurface drainage condition will increase the infiltration and drainage rates during rainfall event and will decrease KCl concentration in surface runoff. Therefore, it is necessary to reuse drained fertile water effectively during rainfall, without polluting groundwater. These study results should be considered in agriculture management to reduce soluble chemical transfer from soil to surface runoff for reducing non-point sources pollution.

Organic layer serves as a hotspot of microbial activity and abundance in Arctic tundra soils.

PubMed

Lee, Seung-Hoon; Jang, Inyoung; Chae, Namyi; Choi, Taejin; Kang, Hojeong

2013-02-01

Tundra ecosystem is of importance for its high accumulation of organic carbon and vulnerability to future climate change. Microorganisms play a key role in carbon dynamics of the tundra ecosystem by mineralizing organic carbon. We assessed both ecosystem process rates and community structure of Bacteria, Archaea, and Fungi in different soil layers (surface organic layer and subsurface mineral soil) in an Arctic soil ecosystem located at Spitsbergen, Svalbard during the summer of 2008 by using biochemical and molecular analyses, such as enzymatic assay, terminal restriction fragment length polymorphism (T-RFLP), quantitative polymerase chain reaction (qPCR), and pyrosequencing. Activity of hydrolytic enzymes showed difference according to soil type. For all three microbial communities, the average gene copy number did not significantly differ between soil types. However, archaeal diversities appeared to differ according to soil type, whereas bacterial and fungal diversity indices did not show any variation. Correlation analysis between biogeochemical and microbial parameters exhibited a discriminating pattern according to microbial or soil types. Analysis of the microbial community structure showed that bacterial and archaeal communities have different profiles with unique phylotypes in terms of soil types. Water content and hydrolytic enzymes were found to be related with the structure of bacterial and archaeal communities, whereas soil organic matter (SOM) and total organic carbon (TOC) were related with bacterial communities. The overall results of this study indicate that microbial enzyme activity were generally higher in the organic layer than in mineral soils and that bacterial and archaeal communities differed between the organic layer and mineral soils in the Arctic region. Compared to mineral soil, peat-covered organic layer may represent a hotspot for secondary productivity and nutrient cycling in this ecosystem.

Wet-dry cycles impact DOM retention in subsurface soils

NASA Astrophysics Data System (ADS)

Olshansky, Yaniv; Root, Robert A.; Chorover, Jon

2018-02-01

Transport and reactivity of carbon in the critical zone are highly controlled by reactions of dissolved organic matter (DOM) with subsurface soils, including adsorption, transformation and exchange. These reactions are dependent on frequent wet-dry cycles common to the unsaturated zone, particularly in semi-arid regions. To test for an effect of wet-dry cycles on DOM interaction and stabilization in subsoils, samples were collected from subsurface (Bw) horizons of an Entisol and an Alfisol from the Catalina-Jemez Critical Zone Observatory and sequentially reacted (four batch steps) with DOM extracted from the corresponding soil litter layers. Between each reaction step, soils either were allowed to air dry (wet-dry treatment) before introduction of the following DOM solution or were maintained under constant wetness (continually wet treatment). Microbial degradation was the dominant mechanism of DOM loss from solution for the Entisol subsoil, which had higher initial organic C content, whereas sorptive retention predominated in the lower C Alfisol subsoil. For a given soil, bulk dissolved organic C losses from solution were similar across treatments. However, a combination of Fourier transform infrared (FTIR) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopic analyses revealed that wet-dry treatments enhanced the interactions between carboxyl functional groups and soil particle surfaces. Scanning transmission X-ray microscopy (STXM) data suggested that cation bridging by Ca2+ was the primary mechanism for carboxyl association with soil surfaces. STXM data also showed that spatial fractionation of adsorbed OM on soil organo-mineral surfaces was diminished relative to what might be inferred from previously published observations pertaining to DOM fractionation on reaction with specimen mineral phases. This study provides direct evidence of the role of wet-dry cycles in affecting sorption reactions of DOM to a complex soil matrix. In the soil environment, where wet-dry cycles occur at different frequencies from site to site and along the soil profile, different interactions between DOM and soil surfaces are expected and need to be considered for the overall assessment of carbon dynamics.

Can the soil fauna of boreal forests recover from lead-derived stress in a shooting range area?

PubMed

Selonen, Salla; Liiri, Mira; Setälä, Heikki

2014-04-01

The responses of soil faunal communities to lead (Pb) contamination in a shooting range area and the recovery of these fauna after range abandonment were studied by comparing the communities at an active shotgun shooting range, an abandoned shooting range, and a control site, locating in the same forest. Despite the similar overall Pb pellet load at the shooting ranges, reaching up to 4 kg m(-2), Pb concentrations in the top soil of the abandoned range has decreased due to the accumulation of detritus on the soil surface. As a consequence, soil animal communities were shown to recover from Pb-related disturbances by utilizing the less contaminated soil layer. Microarthropods showed the clearest signs of recovery, their numbers and community composition being close to those detected at the control site. However, in the deepest organic soil layer, the negative effects of Pb were more pronounced at the abandoned than at the active shooting range, which was detected as altered microarthropod and nematode community structures, reduced abundances of several microarthropod taxa, and the total absence of enchytraeid worms. Thus, although the accumulation of fresh litter on soil surface can promote the recovery of decomposer communities in the top soil, the gradual release of Pb from corroding pellets may pose a long-lasting risk for decomposer taxa deeper in the soil.

Selective nature and inherent variability of interrill erosion across prolonged rainfall simulation

NASA Astrophysics Data System (ADS)

Hu, Y.; Kuhn, N. J.; Fister, W.

2012-04-01

Sediment of interrill erosion has been generally recognized to be selectively enriched with soil organic carbon (SOC) and fine fractions (clay/silt-sized particles or aggregates) in comparison to source area soil. Limited kinetic energy and lack of concentrated runoff are the dominant factors causing selective detachment and transportation. Although enrichment ratios of SOC (ERsoc) in eroded sediment were generally reported > 1, the values varied widely. Causal factors to variation, such as initial soil properties, rainfall properties and experimental conditions, have been extensively discussed. But less attention was directed to the potential influence of prolonged rainfall time onto the temporal pattern of ERsoc. Conservation of mass dictates that ERsoc must be balanced by a decline in the source material which should also lead to a reduced or even negative ERsoc in sediment over time. Besides, the stabilizing effects of structural crust on reducing erosional variation, and the unavoidable variations of erosional response induced by the inherent complexity of interrill erosion, have scarcely been integrated. Moreover, during a prolonged rainfall event surface roughness evolves and affects the movement of eroded aggregates and mineral particles. In this study, two silt loams from Möhlin, Switzerland, organically (OS) and conventionally farmed (CS), were exposed to simulated rainfall of 30 mm h-1 for up to 6 hours. Round donut-flumes with a confined eroding area (1845 cm2) and limited transporting distance (20 cm) were used. Sediments, runoff and subsurface flow were collected in intervals of 30 min. Loose aggregates left on the eroded soil surface, crusts and the soil underneath the crusts were collected after the experiment. All the samples were analyzed for total organic carbon (TOC) content, and texture. Laser scanning of soil surface was applied before and after the rainfall event. The whole experiment was repeated for 10 times. Results from this study showed that: 1) ERsoc in eroded sediment increased at first, then reached steady state and declined afterwards, corresponding well with the formation and completion of structural crust and conservation of mass; 2) the effect of structural crust on stabilizing the surface condition and reducing variation of erosional response was more apparent once steady state discharge was achieved ; and 3) both texture and TOC content in crusts and soil underneath the crusts were comparable to parent soil, explaining the decline in ERsoc. In conclusion, the experiment showed that crusting and conservation of mass lead to a decline and even negative enrichment of organic matter in interrill sediment over time. Enrichment of organic matter should therefore be reported only in conjunction with information about the stage of crust development observed during an erosion event.

Brief Overview of Using Nonlinear Seismology in Analysis of the Soil Deposits Effects on Structure Location

NASA Astrophysics Data System (ADS)

Florin Balan, Stefan; Apostol, Bogdan Felix; Ionescu, Constantin

2017-12-01

The purpose of the paper is to show the great influence of nonlinear seismology in the analysis of the soil deposit response. Some elements about nonlinear seismology, the complexity of the seismic phenomenon are presented, and how we perceive seismic input for constructions at the surface of the earth. Further is presented the nonlinear behaviour of soil deposits during strong earthquakes as it results from resonant column tests (in laboratory) and from the spectral amplification factors (in situ records). The resonance phenomenon between natural period of a structure and soil deposit during strong earthquakes is analysed. All these studies have in common nonlinear behaviour of the soil deposit during strong earthquakes, in fact, the site where a new construction is built or an old one is rehabilitated and needs an optional assessment for mitigation seismic risk. All these studies stand up in supporting nonlinear seismology, the seismology of the XXI-st century.

Drought causes substantial reductions in non-isothermal soil strength

NASA Astrophysics Data System (ADS)

Vahedifard, F.; Robinson, J. D.; Love, C. A.; AghaKouchak, A.

2016-12-01

The stability and settlement of natural slopes and engineering structures are governed primarily by the shear strength of foundation soil. Understanding soil-atmosphere interactions and their impacts on shear strength is imperative to evaluating drought impacts on the resilience of our infrastructure. This understanding is also important for assessing a variety of emerging science and engineering problems in a changing climate including analyzing existing and new infrastructures, landslides, soil carbon sequestration, land management, and managing traction and tillage in agriculture. While progress has been made in understanding shear strength response to soil moisture changes, the impacts of concurrent soil moisture and temperature changes on shear strength remain uncertain from a regional-scale perspective. Here we present a methodological framework based on various soil types, temperatures, and moistures, and surface fluxes, to quantify a non-isothermal soil shear strength. We employ a non-isothermal soil strength analysis (NISSA) to explore the extent to which elevated soil temperatures and low moistures, along with abnormal surface fluxes, during California's record-setting 2012 - 2015 drought reduced the soil's shear strength. Our results suggest that the prolonged California drought reduced the shear strength of fine-grained soil as much as 95%. In contrast, the NISSA suggests that drought impacts on coarse-grained soil were not as significant. These opposing behaviors are attributed to the existence and absence of intermolecular physico-chemical forces in fine- and coarse-grained soils, respectively. The outlined framework offers a unique avenue to explore how soil shear strength is likely to behave under extreme drought conditions.

Relationship between gaseous N dynamics and the hydraulic state of hierarchically structured soils

NASA Astrophysics Data System (ADS)

Schlüter, Steffen; Dörsch, Peter; Vogel, Hans-Jörg

2017-04-01

The inherent spatial heterogeneity of soil generates spatially distributed micro-sites with different local N gas (NO, N2O, N2) production and release rates. Moreover, local micro-site conditions and the pathways between them depend on soil moisture which itself is highly dynamic close to the soil surface. These relationships need to be taken into account for a quantitative understanding of soil denitrification and associated N gas dynamics. Soil structure has been recognized as a key factor to understand the high spatial variability of N gas emissions. In particular gaseous N release from soils depends on: i) the total denitrification rate, which is related to the spatial extent and distribution of anaerobic sites and ii) the probability of N2O to escape from the soil without being further reduced to N2. This impact of soil structure is typically ignored in studies with soil slurries or repacked soil. In this project we run well-defined mesocosm experiments on N gas dynamics with hierarchically structured, artificial soils in which the spatial distribution of substrate and denitrifiers is known exactly. Sintered, porous glass pellets are inoculated with strains of Paracoccus denitrificans and/or Agrobacterium tumefaciens and amended with nutrient solution. These pellets are embedded in coarse-grained sand within gas-tight columns under O2/He atmosphere. The pellets are either places in layers or randomly to create different patterns of N gas production sites and diffusion pathways. Denitrification occurs in the anaerobic centers of the porous pellets, while the partially saturated sand matrix controls the diffusive transport of N gases towards the headspace, where all relevant gas concentrations are monitored with gas chromatography. Water saturations are adjusted such that the diffusive pathways are either fully continuous or partially discontinuous. Preliminary results indicate that the water content exert a major control on the magnitude of denitrification, whereas the onset and dynamics are mainly controlled by the position of the substrate and the denitrifiers.

Developing and using artificial soils to analyze soil microbial processes

NASA Astrophysics Data System (ADS)

Gao, X.; Cheng, H. Y.; Boynton, L.; Masiello, C. A.; Silberg, J. J.

2017-12-01

Microbial diversity and function in soils are governed by soil characteristics such as mineral composition, particles size and aggregations, soil organic matter (SOM), and availability of nutrients and H2O. The spatial and temporal heterogeneity of soils creates a range of niches (hotspots) differing in the availability of O2, H2O, and nutrients, which shapes microbial activities at scales ranging from nanometer to landscape. Synthetic biologists often examine microbial response trigged by their environment conditions in nutrient-rich aqueous media using single strain microbes. While these studies provided useful insight in the role of soil microbes in important soil biogeochemical processes (e.g., C cycling, N cycling, etc.), the results obtained from the over-simplified model systems are often not applicable natural soil systems. On the contrary, soil microbiologists examine microbial processes in natural soils using longer incubation time. However, due to its physical, chemical and biological complexity of natural soils, it is often difficult to examine soil characteristics independently and understand how each characteristic influences soil microbial activities and their corresponding soil functioning. Therefore, it is necessary to bridge the gap and develop a model matrix to exclude unpredictable influences from the environment while still reliably mimicking real environmental conditions. The objective of this study is to design a range of ecologically-relevant artificial soils with varying texture (particle size distribution), structure, mineralogy, SOM content, and nutrient heterogeneity. We thoroughly characterize the artificial soils for pH, active surface area and surface morphology, cation exchange capacity (CEC), and water retention curve. We demonstrate the effectiveness of the artificial soils as useful matrix for microbial processes, such as microbial growth and horizontal gene transfer (HGT), using the gas-reporting biosensors recently developed in our lab.

Multiple tuned mass damper based vibration mitigation of offshore wind turbine considering soil-structure interaction

NASA Astrophysics Data System (ADS)

Hussan, Mosaruf; Sharmin, Faria; Kim, Dookie

2017-08-01

The dynamics of jacket supported offshore wind turbine (OWT) in earthquake environment is one of the progressing focuses in the renewable energy field. Soil-structure interaction (SSI) is a fundamental principle to analyze stability and safety of the structure. This study focuses on the performance of the multiple tuned mass damper (MTMD) in minimizing the dynamic responses of the structures objected to seismic loads combined with static wind and wave loads. Response surface methodology (RSM) has been applied to design the MTMD parameters. The analyses have been performed under two different boundary conditions: fixed base (without SSI) and flexible base (with SSI). Two vibration modes of the structure have been suppressed by multi-mode vibration control principle in both cases. The effectiveness of the MTMD in reducing the dynamic response of the structure is presented. The dynamic SSI plays an important role in the seismic behavior of the jacket supported OWT, especially resting on the soft soil deposit. Finally, it shows that excluding the SSI effect could be the reason of overestimating the MTMD performance.

Simulation of Surface Energy Fluxes and Snow Interception Using a Higher Order Closure Multi-Layer Soil-Vegetation-Atmospheric Model: The Effect of Canopy Shape and Structure

NASA Astrophysics Data System (ADS)

McGowan, L. E.; Dahlke, H. E.; Paw U, K. T.

2015-12-01

Snow cover is a critical driver of the Earth's surface energy budget, climate change, and water resources. Variations in snow cover not only affect the energy budget of the land surface but also represent a major water supply source. In California, US estimates of snow depth, extent, and melt in the Sierra Nevada are critical to estimating the amount of water available for both California agriculture and urban users. However, accurate estimates of snow cover and snow melt processes in forested area still remain a challenge. Canopy structure influences the vertical and spatiotemporal distribution of snow, and therefore ultimately determines the degree and extent by which snow alters both the surface energy balance and water availability in forested regions. In this study we use the Advanced Canopy-Atmosphere-Soil algorithm (ACASA), a multi-layer soil-vegetation-atmosphere numerical model, to simulate the effect of different snow-covered canopy structures on the energy budget, and temperature and other scalar profiles within different forest types in the Sierra Nevada, California. ACASA incorporates a higher order turbulence closure scheme which allows the detailed simulation of turbulent fluxes of heat and water vapor as well as the CO2 exchange of several layers within the canopy. As such ACASA can capture the counter gradient fluxes within canopies that may occur frequently, but are typically unaccounted for, in most snow hydrology models. Six different canopy types were modeled ranging from coniferous forests (e.g. most biomass near the ground) to top-heavy (e.g. most biomass near the top of the crown) deciduous forests to multi-layered forest canopies (e.g. mixture of young and mature trees). Preliminary results indicate that the canopy shape and structure associated with different canopy types fundamentally influence the vertical scalar profiles (including those of temperature, moisture, and wind speed) in the canopy and thus alter the interception and snow melt dynamics in forested land surfaces. The turbulent transport dynamics, including counter-gradient fluxes, and radiation features including land surface albedo, are discussed in the context of the snow energy balance.

On the role of "internal variability" on soil erosion assessment

NASA Astrophysics Data System (ADS)

Kim, Jongho; Ivanov, Valeriy; Fatichi, Simone

2017-04-01

Empirical data demonstrate that soil loss is highly non-unique with respect to meteorological or even runoff forcing and its frequency distributions exhibit heavy tails. However, all current erosion assessments do not describe the large associated uncertainties of temporal erosion variability and make unjustified assumptions by relying on central tendencies. Thus, the predictive skill of prognostic models and reliability of national-scale assessments have been repeatedly questioned. In this study, we attempt to reveal that the high variability in soil losses can be attributed to two sources: (1) 'external variability' referring to the uncertainties originating at macro-scale, such as climate, topography, and land use, which has been extensively studied; (2) 'geomorphic internal variability' referring to the micro-scale variations of pedologic properties (e.g., surface erodibility in soils with multi-sized particles), hydrologic properties (e.g., soil structure and degree of saturation), and hydraulic properties (e.g., surface roughness and surface topography). Using data and a physical hydraulic, hydrologic, and erosion and sediment transport model, we show that the geomorphic internal variability summarized by spatio-temporal variability in surface erodibility properties is a considerable source of uncertainty in erosion estimates and represents an overlooked but vital element of geomorphic response. The conclusion is that predictive frameworks of soil erosion should embed stochastic components together with deterministic assessments, if they do not want to largely underestimate uncertainty. Acknowledgement: This study was supported by the Basic Science Research Program of the National Research Foundation of Korea funded by the Ministry of Education (2016R1D1A1B03931886).

Rhizosphere biophysics and root water uptake

NASA Astrophysics Data System (ADS)

Carminati, Andrea; Zarebanadkouki, Mohsen; Ahmed, Mutez A.; Passioura, John

2016-04-01

The flow of water into the roots and the (putative) presence of a large resistance at the root-soil interface have attracted the attention of plant and soil scientists for decades. Such resistance has been attributed to a partial contact between roots and soil, large gradients in soil matric potential around the roots, or accumulation of solutes at the root surface creating a negative osmotic potential. Our hypothesis is that roots are capable of altering the biophysical properties of the soil around the roots, the rhizosphere, facilitating root water uptake in dry soils. In particular, we expect that root hairs and mucilage optimally connect the roots to the soil maintaining the hydraulic continuity across the rhizosphere. Using a pressure chamber apparatus we measured the relation between transpiration rate and the water potential difference between soil and leaf xylem during drying cycles in barley mutants with and without root hairs. The samples were grown in well structured soils. At low soil moistures and high transpiration rates, large drops in water potential developed around the roots. These drops in water potential recovered very slowly, even after transpiration was severely decreased. The drops in water potential were much bigger in barley mutants without root hairs. These mutants failed to sustain high transpiration rates in dry conditions. To explain the nature of such drops in water potential across the rhizosphere we performed high resolution neutron tomography of the rhizosphere of the barleys with and without root hairs growing in the same soil described above. The tomograms suggested that the hydraulic contact between the soil structures was the highest resistance for the water flow in dry conditions. The tomograms also indicate that root hairs and mucilage improved the hydraulic contact between roots and soil structures. At high transpiration rates and low water contents, roots extracted water from the rhizosphere, while the bulk soil, due its low unsaturated conductivity, failed to compensate root water uptake. We conclude that root hairs are functional to increase the contact area between the roots and the soil structures and mucilage maintains wet the soil region between root hairs. These observations demonstrate the importance of the biophysical processes in the rhizosphere in modulating root water uptake.

Unexpectedly high soil organic carbon stocks under impervious surfaces contributed by urban deep cultural layers

NASA Astrophysics Data System (ADS)

Bae, J.; Ryu, Y.

2017-12-01

The expansion of urban artificial structures has altered the spatial distribution of soil organic carbon (SOC) stocks. The majority of the urban soil studies within the land-cover types, however, focused on top soils despite the potential of deep soils to store large amounts of SOC. Here, we investigate vertical distribution of SOC stocks in both impervious surfaces (n = 11) and adjacent green spaces (n = 8) to a depth of 4 m with in an apartment complex area, Seoul, Republic of Korea. We found that more than six times differences in SOC stocks were observed at 0-1 m depth between the impervious surfaces (1.90 kgC m-2) and the green spaces (12.03 kgC m-2), but no significant differences appeared when comparing them at the depth of 0-4 m. We found "cultural layers" with the largest SOC stocks at 1-2 m depth in the impervious surfaces (15.85 kgC m-2) and 2-3 m depths in urban green spaces (12.52 kgC m-2). Thus, the proportions of SOC stocks at the 0-1 m depth to the total of 0-4 m depth were 6.83% in impervious surfaces and 32.15% in urban green spaces, respectively. The 13C and 15N stable isotope data with historical aerial photographs revealed that the cropland which existed before 1978 formed the SOC in the cultural layers. Our results highlight that impervious surface could hold large amount of SOC stock which has been overlooked in urban carbon cycles. We believe this finding will help city planners and policy makers to develop carbon management programs better towards sustainable urban ecosystems.

Unsaturated flow processes in structurally-variable pathways in wildfire-affected soils and ash

NASA Astrophysics Data System (ADS)

Ebel, B. A.

2016-12-01

Prediction of flash flood and debris flow generation in wildfire-affected soils and ash hinges on understanding unsaturated flow processes. Water resources issues, such as groundwater recharge, also rely on our ability to quantify subsurface flow. Soil-hydraulic property data provide insight into unsaturated flow processes and timescales. A literature review and synthesis of existing data from the literature for wildfire-affected soils, including ash and unburned soils, facilitated calculating metrics and timescales of hydrologic response related to infiltration and surface runoff generation. Sorptivity (S) and the Green-Ampt wetting front parameter (Ψf) were significantly lower in burned soils compared to unburned soils, while field-saturated hydraulic conductivity (Kfs) was not significantly different. The magnitude and duration of the influence of capillarity was substantially reduced in burned soils, leading to faster ponding times in response to rainfall. Ash had large values of S and Kfs compared to unburned and burned soils but intermediate values of Ψf, suggesting that ash has long ponding times in response to rainfall. The ratio of S2/Kfs was nearly constant ( 100 mm) for unburned soils, but was more variable in burned soils. Post-wildfire changes in this ratio suggested that unburned soils had a balance between gravity and capillarity contributions to infiltration, which may depend on soil organic matter, while burning shifted infiltration more towards gravity contributions by reducing S. Taken together, the changes in post-wildfire soil-hydraulic properties increased the propensity for surface runoff generation and may have enhanced subsurface preferential flow through pathways altered by wildfire.

Protein–Mineral Interactions: Molecular Dynamics Simulations Capture Importance of Variations in Mineral Surface Composition and Structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andersen, Amity; Reardon, Patrick N.; Chacon, Stephany S.

Molecular dynamics simulations, conventional and metadynamics, were performed to determine the interaction of model protein Gb1 over kaolinite (001), Na+-montmorillonite (001), Ca2+-montmorillonite (001), goethite (100), and Na+-birnessite (001) mineral surfaces. Gb1, a small (56 residue) protein with a well-characterized solution-state nuclear magnetic resonance (NMR) structure and having α-helix, four-fold β-sheet, and hydrophobic core features, is used as a model protein to study protein soil mineral interactions and gain insights on structural changes and potential degradation of protein. From our simulations, we observe little change to the hydrated Gb1 structure over the kaolinite, montmorillonite, and goethite surfaces relative to its solvatedmore » structure without these mineral surfaces present. Over the Na+-birnessite basal surface, however, the Gb1 structure is highly disturbed as a result of interaction with this birnessite surface. Unraveling of the Gb1 β-sheet at specific turns and a partial unraveling of the α-helix is observed over birnessite, which suggests specific vulnerable residue sites for oxidation or hydrolysis possibly leading to fragmentation.« less

Phosphorus Release to Floodwater from Calcareous Surface Soils and Their Corresponding Subsurface Soils under Anaerobic Conditions.

PubMed

Jayarathne, P D K D; Kumaragamage, D; Indraratne, S; Flaten, D; Goltz, D

2016-07-01

Enhanced phosphorus (P) release from soils to overlying water under flooded, anaerobic conditions has been well documented for noncalcareous and surface soils, but little information is available for calcareous and subsurface soils. We compared the magnitude of P released from 12 calcareous surface soils and corresponding subsurface soils to overlying water under flooded, anaerobic conditions and examined the reasons for the differences. Surface (0-15 cm) and subsurface (15-30 cm) soils were packed into vessels and flooded for 8 wk. Soil redox potential and concentrations of dissolved reactive phosphorus (DRP) and total dissolved Ca, Mg, Fe, and Mn in floodwater and pore water were measured weekly. Soil test P was significantly smaller in subsurface soils than in corresponding surface soils; thus, the P release to floodwater from subsurface soils was significantly less than from corresponding surface soils. Under anaerobic conditions, floodwater DRP concentration significantly increased in >80% of calcareous surface soils and in about 40% of subsurface soils. The increase in floodwater DRP concentration was 2- to 17-fold in surface soils but only 4- to 7-fold in subsurface soils. With time of flooding, molar ratios of Ca/P and Mg/P in floodwater increased, whereas Fe/P and Mn/P decreased, suggesting that resorption and/or reprecipitation of P took place involving Fe and Mn. Results indicate that P release to floodwater under anaerobic conditions was enhanced in most calcareous soils. Surface and subsurface calcareous soils in general behaved similarly in releasing P under flooded, anaerobic conditions, with concentrations released mainly governed by initial soil P concentrations. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Structure of peat soils and implications for biogeochemical processes and hydrological flow

NASA Astrophysics Data System (ADS)

Rezanezhad, F.; McCarter, C. P. R.; Gharedaghloo, B.; Kleimeier, C.; Milojevic, T.; Liu, H.; Weber, T. K. D.; Price, J. S.; Quinton, W. L.; Lenartz, B.; Van Cappellen, P.

2017-12-01

Permafrost peatlands contain globally important amounts of soil organic carbon and play major roles in global water, nutrient and biogeochemical cycles. The structure of peatland soils (i.e., peat) are highly complex with unique physical and hydraulic properties; where significant, and only partially reversible, shrinkage occurs during dewatering (including water table fluctuations), compression and/or decomposition. These distinct physical and hydraulic properties controls water flow, which in turn affect reactive and non-reactive solute transport (such as, sorption or degradation) and biogeochemical functions. Additionally, peat further attenuates solute migration through molecular diffusion into the inactive pores of Sphagnum dominated peat. These slow, diffusion-limited solute exchanges between the pore regions may give rise to pore-scale chemical gradients and heterogeneous distributions of microbial habitats and activity in peat soils. Permafrost peat plateaus have the same essential subsurface characteristics as other widely organic soil-covered peatlands, where the hydraulic conductivity is related to the degree of decomposition and soil compression. Increasing levels of decomposition correspond with a reduction of effective pore diameter and consequently restrict water and solute flow (by several orders of magnitude in hydraulic conductivity between the ground surface and a depth of 50 cm). In this presentation, we present the current knowledge of key physical and hydraulic properties related to the structure of globally available peat soils and discuss their implications for water storage, flow and the migration of solutes.

Optimizing available water capacity using microwave satellite data for improving irrigation management

NASA Astrophysics Data System (ADS)

Gupta, Manika; Bolten, John; Lakshmi, Venkat

2015-04-01

This work addresses the improvement of available water capacity by developing a technique for estimating soil hydraulic parameters through the utilization of satellite-retrieved near surface soil moisture. The prototype involves the usage of Monte Carlo analysis to assimilate historical remote sensing soil moisture data available from the Advanced Microwave Scanning Radiometer (AMSR-E) within the hydrological model. The main hypothesis used in this study is that near-surface soil moisture data contain useful information that can describe the effective hydrological conditions of the basin such that when appropriately In the method followed in this study the hydraulic parameters are derived directly from information on the soil moisture state at the AMSR-E footprint scale and the available water capacity is derived for the root zone by coupling of AMSR-E soil moisture with the physically-based hydrological model. The available capacity water, which refers to difference between the field capacity and wilting point of the soil and represent the soil moisture content at 0.33 bar and 15 bar respectively is estimated from the soil hydraulic parameters using the van Genuchten equation. The initial ranges of soil hydraulic parameters are taken in correspondence with the values available from the literature based on Soil Survey Geographic (SSURGO) database within the particular AMSR-E footprint. Using the Monte Carlo simulation, the ranges are narrowed in the region where simulation shows a good match between predicted and near-surface soil moisture from AMSR-E. In this study, the uncertainties in accurately determining the parameters of the nonlinear soil water retention function for large-scale hydrological modeling is the focus of the development of the Bayesian framework. Thus, the model forecasting has been combined with the observational information to optimize the model state and the soil hydraulic parameters simultaneously. The optimization process is divided into two steps during one time interval: the state variable is optimized through the state filter and the optimal parameter values are then transferred for retrieving soil moisture. However, soil moisture from sensors such as AMSR-E can only be retrieved for the top few centimeters of soil. So, for the present study, a homogeneous soil system has been considered. By assimilating this information into the model, the accuracy of model structure in relating surface moisture dynamics to deeper soil profiles can be ascertained. To evaluate the performance of the system in helping improve simulation accuracy and whether they can be used to obtain soil moisture profiles at poorly gauged catchments alongwith the available water capacity, the root mean square error (RMSE) and Mean Bias error (MBE) are used to measure the performance of the soil moisture simulations. The optimized parameters as compared to the pedo-transfer based parameters were found to reduce the RMSE from 0.14 to 0.04 and 0.15 to 0.07 in surface layer and root zone respectively.

Organic matter quantity and source affects microbial community structure and function following volcanic eruption on Kasatochi Island, Alaska

USGS Publications Warehouse

Zeglin, Lydia H.; Wang, Bronwen; Waythomas, Christopher F.; Rainey, Frederick; Talbot, Sandra L.

2016-01-01

In August 2008, Kasatochi volcano erupted and buried a small island in pyroclastic deposits and fine ash; since then, microbes, plants and birds have begun to re-colonize the initially sterile surface. Five years post-eruption, bacterial 16S rRNA gene and fungal internal transcribed spacer (ITS) copy numbers and extracellular enzyme activity (EEA) potentials were one to two orders of magnitude greater in pyroclastic materials with organic matter (OM) inputs relative to those without, despite minimal accumulation of OM (< 0.2%C). When normalized by OM levels, post-eruptive surfaces with OM inputs had the highest β-glucosidase, phosphatase, NAGase and cellobiohydrolase activities, and had microbial population sizes approaching those in reference soils. In contrast, the strongest factor determining bacterial community composition was the dominance of plants versus birds as OM input vectors. Although soil pH ranged from 3.9 to 7.0, and %C ranged 100×, differentiation between plant- and bird-associated microbial communities suggested that cell dispersal or nutrient availability are more likely drivers of assembly than pH or OM content. This study exemplifies the complex relationship between microbial cell dispersal, soil geochemistry, and microbial structure and function; and illustrates the potential for soil microbiota to be resilient to disturbance.

Soil aggregate stability and rainfall-induced sediment transport on field plots as affected by amendment with organic matter inputs

NASA Astrophysics Data System (ADS)

Shi, Pu; Arter, Christian; Liu, Xingyu; Keller, Martin; Schulin, Rainer

2017-04-01

Aggregate stability is an important factor in soil resistance against erosion, and, by influencing the extent of sediment transport associated with surface runoff, it is thus also one of the key factors which determine on- and off-site effects of water erosion. As it strongly depends on soil organic matter, many studies have explored how aggregate stability can be improved by organic matter inputs into the soil. However, the focus of these studies has been on the relationship between aggregate stability and soil organic matter dynamics. How the effects of organic matter inputs on aggregate stability translate into soil erodibility under rainfall impacts has received much less attention. In this study, we performed field plot experiments to examine how organic matter inputs affect aggregate breakdown and surface sediment transport under field conditions in artificial rainfall events. Three pairs of plots were prepared by adding a mixture of grass and wheat straw to one of plots in each pair but not to the other, while all plots were treated in the same way otherwise. The rainfall events were applied some weeks later so that the applied organic residues had sufficient time for decomposition and incorporation into the soil. Surface runoff rate and sediment concentration showed substantial differences between the treatments with and without organic matter inputs. The plots with organic inputs had coarser and more stable aggregates and a rougher surface than the control plots without organic inputs, resulting in a higher infiltration rate and lower transport capacity of the surface runoff. Consequently, sediments exported from the amended plots were less concentrated but more enriched in suspended particles (<20 µm) than from the un-amended plots, indicating a more size-selective sediment transport. In contrast to the amended plots, there was an increase in the coarse particle fraction (> 250 µm) in the runoff from the plots with no organic matter inputs towards the end of the rainfall events due to emerging bed-load transport. The results show that a single application of organic matter can already cause a large difference in aggregate breakdown, surface sealing, and lateral sediment-associated matter transfer under rainfall impact. Furthermore, we will present terrestrial laser scanning data showing the treatment effects on soil surface structure, as well as data on carbon, phosphorus and heavy metal export associated with the translocation of the sediments.

Phosphate effects on copper(II) and lead(II) sorption to ferrihydrite

NASA Astrophysics Data System (ADS)

Tiberg, Charlotta; Sjöstedt, Carin; Persson, Ingmar; Gustafsson, Jon Petter

2013-11-01

Transport of lead(II) and copper(II) ions in soil is affected by the soil phosphorus status. Part of the explanation may be that phosphate increases the adsorption of copper(II) and lead(II) to iron (hydr)oxides in soil, but the details of these interactions are poorly known. Knowledge about such mechanisms is important, for example, in risk assessments of contaminated sites and development of remediation methods. We used a combination of batch experiments, extended X-ray absorption fine structure (EXAFS) spectroscopy and surface complexation modeling with the three-plane CD-MUSIC model to study the effect of phosphate on sorption of copper(II) and lead(II) to ferrihydrite. The aim was to identify the surface complexes formed and to derive constants for the surface complexation reactions. In the batch experiments phosphate greatly enhanced the adsorption of copper(II) and lead(II) to ferrihydrite at pH < 6. The largest effects were seen for lead(II).

Transfer of radiocesium from rhizosphere soil to four cruciferous vegetables in association with a Bacillus pumilus strain and root exudation.

PubMed

Aung, Han Phyo; Mensah, Akwasi Dwira; Aye, Yi Swe; Djedidi, Salem; Oikawa, Yosei; Yokoyama, Tadashi; Suzuki, Sohzoh; Dorothea Bellingrath-Kimura, Sonoko

2016-11-01

This study was carried out to assess the effect of Bacillus pumilus on the roots of four cruciferous vegetables with different root structures in regard to enhancement of 137 Cs bioavailability in contaminated rhizosphere soil. Results revealed that B. pumilus inoculation did not enhance the plant biomass of vegetables, although it increased root volume and root surface areas of all vegetables except turnip. The pH changes due to rhizosphere acidification by B. pumilus inoculation and root exudation did not affect the bioavailability of 137 Cs. However, concentrations of 137 Cs in plant tissues and soil-to-plant transfer values increased as a result of the larger root volume and root surface area of vegetables due to inoculation. Moreover, leafy vegetables, which possessed larger root volume and root surface areas, had a higher 137 Cs transfer value than root vegetables. Copyright © 2016 Elsevier Ltd. All rights reserved.

Thermal separation of soil particles from thermal conductivity measurement under various air pressures.

PubMed

Lu, Sen; Ren, Tusheng; Lu, Yili; Meng, Ping; Zhang, Jinsong

2017-01-05

The thermal conductivity of dry soils is related closely to air pressure and the contact areas between solid particles. In this study, the thermal conductivity of two-phase soil systems was determined under reduced and increased air pressures. The thermal separation of soil particles, i.e., the characteristic dimension of the pore space (d), was then estimated based on the relationship between soil thermal conductivity and air pressure. Results showed that under both reduced and increased air pressures, d estimations were significantly larger than the geometrical mean separation of solid particles (D), which suggested that conductive heat transfer through solid particles dominated heat transfer in dry soils. The increased air pressure approach gave d values lower than that of the reduced air pressure method. With increasing air pressure, more collisions between gas molecules and solid surface occurred in micro-pores and intra-aggregate pores due to the reduction of mean free path of air molecules. Compared to the reduced air pressure approach, the increased air pressure approach expressed more micro-pore structure attributes in heat transfer. We concluded that measuring thermal conductivity under increased air pressure procedures gave better-quality d values, and improved soil micro-pore structure estimation.

Infiltration performance of engineered surfaces commonly used for distributed stormwater management

NASA Astrophysics Data System (ADS)

Valinski, Nicholas A.

Engineered porous media are commonly used in low impact development (LID) structures to mitigate excess stormwater in urban environments. Differences in infiltrability of these LID systems arise from the wide variety of materials used to create porous surfaces and subsequent maintenance, debris loading, and physical damage. In this study, infiltration capacity of six common materials was tested by multiple replicate experiments with automated mini-disk infiltrometers. The tested materials included porous asphalt, porous concrete, porous brick pavers, flexible porous pavement, engineered soils, and native soils. Porous asphalt, large porous brick pavers, and curb cutout rain gardens showed the greatest infiltration rates. Most engineered porous pavements and soils performed better than the native silt loam soils. Infiltration performance was found to be related more to site design and environmental factors than material choice. Sediment trap zones in both pavements and engineered soil rain gardens were found to be beneficial to the whole site performance. Winter chloride application had a large negative impact on poured in place concrete, making it a poor choice for heavily salted areas.

Infiltration performance of engineered surfaces commonly used for distributed stormwater management.

PubMed

Valinski, N A; Chandler, D G

2015-09-01

Engineered porous media are commonly used in low impact development (LID) structures to mitigate excess stormwater in urban environments. Differences in infiltrability of these LID systems arise from the wide variety of materials used to create porous surfaces and subsequent maintenance, debris loading, and physical damage. In this study, the infiltration capacity of six common materials was tested by multiple replicate experiments with automated mini-disk infiltrometers. The tested materials included porous asphalt, porous concrete, porous brick pavers, flexible porous pavement, engineered soils, and native soils. Porous asphalt, large porous brick pavers, and curb cutout rain gardens showed the greatest infiltration rates. Most engineered porous pavements and soils performed better than the native silt loam soils. Infiltration performance was found to be related more to site design and environmental factors than material choice. Sediment trap zones in both pavements and engineered soil rain gardens were found to be beneficial to the whole site performance. Winter chloride application had a large negative impact on poured in place concrete, making it a poor choice for heavily salted areas. Copyright © 2015 Elsevier Ltd. All rights reserved.

Effects of fire and fuels management on water quality in eastern North America

Treesearch

R. K. Kolka

2012-01-01

Fuels management, especially prescribed fire, can have direct impacts on aquatic resources through deposition of ash to surface waters. On the terrestrial side, fuels management leads to changes in vegetative structure and potentially soil properties that affect ecosystem cycling of water and inorganic and organic constituents. Because surface water systems (streams,...

DAYCENT AND ITS LAND SURFACE SUBMODEL: DESCRIPTION AND TESTING. (R824993)

EPA Science Inventory

Abstract

A land surface submodel was developed for the daily version of the CENTURY ecosystem model (DAYCENT). The goal of DAYCENT to simulate soil N₂O, NO_x, and CH₄ fluxes for terrestrial ecosystems determined the structure and ...

MODELING AGGREGATE EXPOSURE AND DOSE OF CHILDREN TO A WOOD TREATMENT PRESERVATIVE FROM PLAYSETS AND HOME DECKS

EPA Science Inventory

Pressure- or non-pressure- treated lumber may pose a potential health hazard to children if the children contact certain chemicals in soils around leaching wood structures and/or in dislodgeable residues that may form on the wood surfaces of the structures. A physically-based,...

Sinking during earthquakes: Critical acceleration criteria control drained soil liquefaction

NASA Astrophysics Data System (ADS)

Clément, C.; Toussaint, R.; Stojanova, M.; Aharonov, E.

2018-02-01

This article focuses on liquefaction of saturated granular soils, triggered by earthquakes. Liquefaction is defined here as the transition from a rigid state, in which the granular soil layer supports structures placed on its surface, to a fluidlike state, in which structures placed initially on the surface sink to their isostatic depth within the granular layer. We suggest a simple theoretical model for soil liquefaction and show that buoyancy caused by the presence of water inside a granular medium has a dramatic influence on the stability of an intruder resting at the surface of the medium. We confirm this hypothesis by comparison with laboratory experiments and discrete-element numerical simulations. The external excitation representing ground motion during earthquakes is simulated via horizontal sinusoidal oscillations of controlled frequency and amplitude. In the experiments, we use particles only slightly denser than water, which as predicted theoretically increases the effect of liquefaction and allows clear depth-of-sinking measurements. In the simulations, a micromechanical model simulates grains using molecular dynamics with friction between neighbors. The effect of the fluid is captured by taking into account buoyancy effects on the grains when they are immersed. We show that the motion of an intruder inside a granular medium is mainly dependent on the peak acceleration of the ground motion and establish a phase diagram for the conditions under which liquefaction happens, depending on the soil bulk density, friction properties, presence of water, and peak acceleration of the imposed large-scale soil vibrations. We establish that in liquefaction conditions, most cases relax toward an equilibrium position following an exponential in time. We also show that the equilibrium position itself, for most liquefaction regimes, corresponds to the isostatic equilibrium of the intruder inside a medium of effective density. The characteristic time to relaxation is shown to be essentially a function of the peak ground velocity.

Sinking during earthquakes: Critical acceleration criteria control drained soil liquefaction.

PubMed

Clément, C; Toussaint, R; Stojanova, M; Aharonov, E

2018-02-01

This article focuses on liquefaction of saturated granular soils, triggered by earthquakes. Liquefaction is defined here as the transition from a rigid state, in which the granular soil layer supports structures placed on its surface, to a fluidlike state, in which structures placed initially on the surface sink to their isostatic depth within the granular layer. We suggest a simple theoretical model for soil liquefaction and show that buoyancy caused by the presence of water inside a granular medium has a dramatic influence on the stability of an intruder resting at the surface of the medium. We confirm this hypothesis by comparison with laboratory experiments and discrete-element numerical simulations. The external excitation representing ground motion during earthquakes is simulated via horizontal sinusoidal oscillations of controlled frequency and amplitude. In the experiments, we use particles only slightly denser than water, which as predicted theoretically increases the effect of liquefaction and allows clear depth-of-sinking measurements. In the simulations, a micromechanical model simulates grains using molecular dynamics with friction between neighbors. The effect of the fluid is captured by taking into account buoyancy effects on the grains when they are immersed. We show that the motion of an intruder inside a granular medium is mainly dependent on the peak acceleration of the ground motion and establish a phase diagram for the conditions under which liquefaction happens, depending on the soil bulk density, friction properties, presence of water, and peak acceleration of the imposed large-scale soil vibrations. We establish that in liquefaction conditions, most cases relax toward an equilibrium position following an exponential in time. We also show that the equilibrium position itself, for most liquefaction regimes, corresponds to the isostatic equilibrium of the intruder inside a medium of effective density. The characteristic time to relaxation is shown to be essentially a function of the peak ground velocity.

Indirect diagnosis of pavement structural damages using surface GPR reflection techniques

NASA Astrophysics Data System (ADS)

Benedetto, A.; Pensa, S.

2007-06-01

The safety and operability of road networks is, in part, dependent on the quality of the pavement. It is known that pavements suffer from many different structural problems which can lead to damage to the pavement surface. To minimize the effect of these problems programmed policies for pavement management are required. Additionally a given local anomaly on the road surface can affect the safety of the road to various degrees according to the category of the road, so it is possible to set up different programmes of repair according to the different standards of road. Programmed policies for pavement management are required because of the wide structural damage which occurs to pavements during their normal operating life. This has consequences for the safety and operability of road networks. During the last decade, road networks suffered from great structural damage. The damage occurs for different reasons, such as the increasing traffic or the lack of means for routine maintenance. Many forms of damage, originating in the bottom layers are invisible until the pavement cracks. They depend on the infiltration of water and the presence of cohesive soil greatly reduces the bearing capacity of the sub-asphalt layers and underlying soils. On the basis of an in-depth literature review, an experimental survey with Ground Penetrating Radar (GPR) was carried out to calibrate the geophysical parameters and to validate the reliability of an indirect diagnostic method of pavement damage. The experiments were set on a pavement under which water was injected over a period of several hours. GPR travel time data were used to estimate the dielectric constant and the water content in the unbound aggregate layer, the variations in water content with time and particular areas where rate of infiltration decreases. A new methodology has been proposed to extract the hydraulic permittivity fields in sub-asphalt structural layers and soils from the moisture maps observed with GPR. It is effective at diagnosing the presence of clay or cohesive soil that compromises the bearing capacity of sub-base and induces damage.

Combining geomorphological mapping and near surface geophysics (GPR and ERT) to study piping systems

NASA Astrophysics Data System (ADS)

Bernatek-Jakiel, Anita; Kondracka, Marta

2016-12-01

This paper aims to provide a more comprehensive characterization of piping systems in mountainous areas under a temperate climate using geomorphological mapping and geophysical methods (electrical resistivity tomography - ERT and ground penetrating radar - GPR). The significance of piping in gully formation and hillslope hydrology has been discussed for many years, and most of the studies are based on surface investigations. However, it seems that most surface investigations underestimate this subsurface process. Therefore, our purpose was to estimate the scale of piping activity based on both surface and subsurface investigations. We used geophysical methods to detect the boundary of lateral water movement fostering pipe development and recognize the internal structure of the underlying materials. The survey was carried out in the Bereźnica Wyżna catchment, in the Bieszczady Mountains. (Eastern Carpathians, Poland), where pipes develop in Cambisols at a mean depth of about 0.7-0.8 m. The geophysical techniques that were used are shown to be successful in identifying pipes. GPR data suggest that the density of piping systems is much larger than that detectible from surface observations alone. Pipe length can be > 6.5-9.2% (maximum = 49%) higher than what surface mapping suggests. Thus, the significance of piping in hillslope hydrology and gully formation can be greater than previously assumed. These results also draw attention to the scale of piping activity in the Carpathians, where this process has been neglected for many years. The ERT profiles reveal areas affected by piping as places of higher resistivity values, which are an effect of a higher content of air-filled pores (due to higher soil porosity, intense biological activity, and well-developed soil structure). In addition, the ERT profiles show that the pipes in the study area develop at the soil-bedrock interface, probably above the layers of shales or mudstones which create a water restrictive layer. Our results illustrate the suitability and limitations of GPR and ERT to study soil piping. In general, geophysical surveying is useful for gathering more information on pipe density, potential pipe detection, and recognition of the internal structure of materials underlying the pipes. However, the interpretation of radargrams and ERT profiles should be always accompanied by detailed terrain mapping due to potential disturbances affecting geophysical profiles.

Influence of the Amino Acid Sequence on Protein-Mineral Interactions in Soil

NASA Astrophysics Data System (ADS)

Chacon, S. S.; Reardon, P. N.; Purvine, S.; Lipton, M. S.; Washton, N.; Kleber, M.

2017-12-01

The intimate associations between protein and mineral surfaces have profound impacts on nutrient cycling in soil. Proteins are an important source of organic C and N, and a subset of proteins, extracellular enzymes (EE), can catalyze the depolymerization of soil organic matter (SOM). Our goal was to determine how variation in the amino acid sequence could influence a protein's susceptibility to become chemically altered by mineral surfaces to infer the fate of adsorbed EE function in soil. We hypothesized that (1) addition of charged amino acids would enhance the adsorption onto oppositely charged mineral surfaces (2) addition of aromatic amino acids would increase adsorption onto zero charged surfaces (3) Increase adsorption of modified proteins would enhance their susceptibility to alterations by redox active minerals. To test these hypotheses, we generated three engineered proxies of a model protein Gb1 (IEP 4.0, 6.2 kDA) by inserting either negatively charged, positively charged or aromatic amino acids in the second loop. These modified proteins were allowed to interact with functionally different mineral surfaces (goethite, montmorillonite, kaolinite and birnessite) at pH 5 and 7. We used LC-MS/MS and solution-state Heteronuclear Single Quantum Coherence Spectroscopy NMR to observe modifications on engineered proteins as a consequence to mineral interactions. Preliminary results indicate that addition of any amino acids to a protein increase its susceptibility to fragmentation and oxidation by redox active mineral surfaces, and alter adsorption to the other mineral surfaces. This suggest that not all mineral surfaces in soil may act as sorbents for EEs and chemical modification of their structure should also be considered as an explanation for decrease in EE activity. Fragmentation of proteins by minerals can bypass the need to produce proteases, but microbial acquisition of other nutrients that require enzymes such as cellulases, ligninases or phosphatases may be hampered by mineral association.

First and Higher Order Effects on Zero Order Radiative Transfer Model

NASA Astrophysics Data System (ADS)

Neelam, M.; Mohanty, B.

2014-12-01

Microwave radiative transfer model are valuable tool in understanding the complex land surface interactions. Past literature has largely focused on local sensitivity analysis for factor priotization and ignoring the interactions between the variables and uncertainties around them. Since land surface interactions are largely nonlinear, there always exist uncertainties, heterogeneities and interactions thus it is important to quantify them to draw accurate conclusions. In this effort, we used global sensitivity analysis to address the issues of variable uncertainty, higher order interactions, factor priotization and factor fixing for zero-order radiative transfer (ZRT) model. With the to-be-launched Soil Moisture Active Passive (SMAP) mission of NASA, it is very important to have a complete understanding of ZRT for soil moisture retrieval to direct future research and cal/val field campaigns. This is a first attempt to use GSA technique to quantify first order and higher order effects on brightness temperature from ZRT model. Our analyses reflect conditions observed during the growing agricultural season for corn and soybeans in two different regions in - Iowa, U.S.A and Winnipeg, Canada. We found that for corn fields in Iowa, there exist significant second order interactions between soil moisture, surface roughness parameters (RMS height and correlation length) and vegetation parameters (vegetation water content, structure and scattering albedo), whereas in Winnipeg, second order interactions are mainly due to soil moisture and vegetation parameters. But for soybean fields in both Iowa and Winnipeg, we found significant interactions only to exist between soil moisture and surface roughness parameters.

Inclusion of Solar Elevation Angle in Land Surface Albedo Parameterization Over Bare Soil Surface.

PubMed

Zheng, Zhiyuan; Wei, Zhigang; Wen, Zhiping; Dong, Wenjie; Li, Zhenchao; Wen, Xiaohang; Zhu, Xian; Ji, Dong; Chen, Chen; Yan, Dongdong

2017-12-01

Land surface albedo is a significant parameter for maintaining a balance in surface energy. It is also an important parameter of bare soil surface albedo for developing land surface process models that accurately reflect diurnal variation characteristics and the mechanism behind the solar spectral radiation albedo on bare soil surfaces and for understanding the relationships between climate factors and spectral radiation albedo. Using a data set of field observations, we conducted experiments to analyze the variation characteristics of land surface solar spectral radiation and the corresponding albedo over a typical Gobi bare soil underlying surface and to investigate the relationships between the land surface solar spectral radiation albedo, solar elevation angle, and soil moisture. Based on both solar elevation angle and soil moisture measurements simultaneously, we propose a new two-factor parameterization scheme for spectral radiation albedo over bare soil underlying surfaces. The results of numerical simulation experiments show that the new parameterization scheme can more accurately depict the diurnal variation characteristics of bare soil surface albedo than the previous schemes. Solar elevation angle is one of the most important factors for parameterizing bare soil surface albedo and must be considered in the parameterization scheme, especially in arid and semiarid areas with low soil moisture content. This study reveals the characteristics and mechanism of the diurnal variation of bare soil surface solar spectral radiation albedo and is helpful in developing land surface process models, weather models, and climate models.

De-icing salt contamination reduces urban tree performance in structural soil cells.

PubMed

Ordóñez-Barona, Camilo; Sabetski, Vadim; Millward, Andrew A; Steenberg, James

2018-03-01

Salts used for de-icing roads and sidewalks in northern climates can have a significant impact on water quality and vegetation. Sub-surface engineering systems, such as structural soil cells, can regulate water runoff and pollutants, and provide the necessary soil volume and irrigation to grow trees. However, the ability of such systems to manage de-icing salt contamination, and the impact of this contamination on the trees growing in them, have not been evaluated. We report on an field investigation of de-icing salt contamination in structural cells in two street-revitalization projects in Toronto, Canada, and the impact of this contamination on tree performance. We analyzed soil chemistry and collected tree attributes; these data were examined together to understand the effect of salinity on tree mortality rates and foliar condition. Data collected from continuous soil salinity loggers from April to June for one of the two sites were used to determine whether there was a long-term accumulation of salts in the soils. Results for both sites indicate that both sites displayed high salinity and alkalinity, with levels elevated beyond those suggested before those reported to cause negative tree effects. For one site, trees that were alive and trees that had a better foliar condition had significantly lower levels of soil salinity and alkalinity than other trees. High salinity and alkalinity in the soil were also associated with lower nutrient levels for both sites. Although tests for salinity accumulation in the soils of one site were negative, a longer monitoring of the soil conditions within the soil cells is warranted. Despite structural cells being increasingly utilized for their dual role in storm-water management and tree establishment, there may be a considerable trade-off between storm-water management and urban-forest function in northern climates where de-icing salt application continues to be commonplace. Copyright © 2017 Elsevier Ltd. All rights reserved.

Molecular Studies of Complex Soil Organic Matter Interactions with Metal Ions and Mineral Surfaces using Classical Molecular Dynamics and Quantum Chemistry Methods

NASA Astrophysics Data System (ADS)

Andersen, A.; Govind, N.; Laskin, A.

2017-12-01

Mineral surfaces have been implicated as potential protectors of soil organic matter (SOM) against decomposition and ultimate mineralization to small molecules which can provide nutrients for plants and soil microbes and can also contribute to the Earth's elemental cycles. SOM is a complex mixture of organic molecules of biological origin at varying degrees of decomposition and can, itself, self-assemble in such a way as to expose some biomolecule types to biotic and abiotic attack while protecting other biomolecule types. The organization of SOM and SOM with mineral surfaces and solvated metal ions is driven by an interplay of van der Waals and electrostatic interactions leading to partitioning of hydrophilic (e.g. sugars) and hydrophobic (e.g., lipids) SOM components that can be bridged with amphiphilic molecules (e.g., proteins). Classical molecular dynamics simulations can shed light on assemblies of organic molecules alone or complexation with mineral surfaces. The role of chemical reactions is also an important consideration in potential chemical changes of the organic species such as oxidation/reduction, degradation, chemisorption to mineral surfaces, and complexation with solvated metal ions to form organometallic systems. For the study of chemical reactivity, quantum chemistry methods can be employed and combined with structural insight provided by classical MD simulations. Moreover, quantum chemistry can also simulate spectroscopic signatures based on chemical structure and is a valuable tool in interpreting spectra from, notably, x-ray absorption spectroscopy (XAS). In this presentation, we will discuss our classical MD and quantum chemistry findings on a model SOM system interacting with mineral surfaces and solvated metal ions.

Microbial Composition in Decomposing Pine Litter Shifts in Response to Common Soil Secondary Minerals

NASA Astrophysics Data System (ADS)

Welty-Bernard, A. T.; Heckman, K.; Vazquez, A.; Rasmussen, C.; Chorover, J.; Schwartz, E.

2011-12-01

A range of environmental and biotic factors have been identified that drive microbial community structure in soils - carbon substrates, redox conditions, mineral nutrients, salinity, pH, and species interactions. However, soil mineralogy has been largely ignored as a candidate in spite of recent studies that indicate that minerals have a substantial impact on soil organic matter stores and subsequent fluxes from soils. Given that secondary minerals and organic colloids govern a soil's biogeochemical activity due to surface area and electromagnetic charge, we propose that secondary minerals are a strong determinant of the communities that are responsible for process rates. To test this, we created three microcosms to study communities during decomposition using pine forest litter mixed with two common secondary minerals in soils (goethite and gibbsite) and with quartz as a control. Changes in bacterial and fungal communities were tracked over the 154-day incubation by pyrosequencing fragments of the bacterial 16S and fungal 18S rRNA genes. Ordination using nonmetric multidimensional scaling showed that bacterial communities separated on the basis of minerals. Overall, a single generalist - identified as an Acidobacteriaceae isolate - dominated all treatments over the course of the experiment, representing roughly 25% of all communities. Fungal communities discriminated between the quartz control alone and mineral treatments as a whole. Again, several generalists dominated the community. Coniochaeta ligniaria dominated communities with abundances ranging from 29 to 40%. The general stability of generalist populations may explain the similarities between treatment respiration rates. Variation between molecular fingerprints, then, were largely a function of unique minor members with abundances ranging from 0.01 to 8%. Carbon availability did not surface as a possible mechanism responsible for shifts in fingerprints due to the relatively large mass of needles in the incubation. Other possible mechanisms include the presence of soluble Fe as an alternative energy source in the goethite treatment, the presence of toxic soluble Al in the gibbsite treatment, the loss of available phosphorus in the secondary mineral treatments due to sorption by secondary mineral surfaces, and variations in mineral surfaces as microhabitats. These findings suggest that Al and Fe oxides, such as goethite or gibbsite, are a factor in determining microbial community structure.

The artifcial catchment Chicken Creek as a tool to study initial ecosystem development

NASA Astrophysics Data System (ADS)

Schaaf, W.; Elmer, M.; Fischer, A.; Gerwin, W.; Nenov, R.

2011-12-01

The artificial catchment Chicken Creek was constructed in 2005 to study the increasingly complex interactions of processes and structures during initial development of ecosystems. The 6ha area serves as the central research site for the Transregional Collaborative Research Center 38. Both internal and external factors could be identified as driving forces for the formation of structures and patterns in the artificial catchment during the first five years of development. Initial structures formed by the construction process (e.g. catchment morphology, subsurface structures like clay dams and dumping cones, caterpillar tracks at the surface) and initial substrate characteristics (e.g. texture, geochemistry) were decisive both for the distribution and flow of precipitation water and for vegetation succession. External factors like episodic events (e.g. heavy thunderstorms) triggered erosion and dissection during this initial phase, promoted by the low vegetation cover and the unconsolidated sandy substrate. These processes resulted in transport and redistribution of water and sediment within the catchment, mainly along the main slope, and the formation of new structural elements like gullies and channels, a sedimentation fan above and sediments within the pond. As a result, we observed an overall differentiation of the site, e.g. with respect to water availability and texture redistribution, into areas with abrasion or accumulation processes dominating and areas with stable surfaces. During further development, both external factors and processes within the catchment continued to influence the site. For example, beside the initial soil seed bank, the surrounding environment of the catchment clearly affected species invasion. The dissection and stability of surfaces may be an important factor for the establishment of plants and habitats as well as for the formation of vegetation patterns and biological soil crusts. The transformation of the initial geo-system into areas with evolving terrestrial or aquatic characteristics and from a very episodic to a more permanent stream network and discharge, together with the observed vegetation dynamics increased site diversity and heterogeneity with respect to water and nutrient availability and transformation processes compared to the more homogenous conditions at point zero. We expect that these more permanent structures and patterns established after five years will greatly influence the future development of the catchment with respect to e.g. input and accumulation of soil organic matter, nitrogen input and availability by symbiotic microbial N-fixation, development of root systems and soil food webs, weathering and soil formation, element cycling, and the water and element budget at the catchment scale.

Comparison of transport and attachment behaviors of Cryptosporidium parvum oocysts and oocyst-sized microspheres being advected through three minerologically different granular porous media.

PubMed

Mohanram, Arvind; Ray, Chittaranjan; Harvey, Ronald W; Metge, David W; Ryan, Joseph N; Chorover, Jon; Eberl, D D

2010-10-01

In order to gain more information about the fate of Cryptosporidium parvum oocysts in tropical volcanic soils, the transport and attachment behaviors of oocysts and oocyst-sized polystyrene microspheres were studied in the presence of two soils. These soils were chosen because of their differing chemical and physical properties, i.e., an organic-rich (43-46% by mass) volcanic ash-derived soil from the island of Hawaii, and a red, iron (22-29% by mass), aluminum (29-45% by mass), and clay-rich (68-76% by mass) volcanic soil from the island of Oahu. A third agricultural soil, an organic- (13% by mass) and quartz-rich (40% by mass) soil from Illinois, was included for reference. In 10-cm long flow-through columns, oocysts and microspheres advecting through the red volcanic soil were almost completely (98% and 99%) immobilized. The modest breakthrough resulted from preferential flow-path structure inadvertently created by soil-particle aggregation during the re-wetting process. Although a high (99%) removal of oocysts and microsphere within the volcanic ash soil occurred initially, further examination revealed that transport was merely retarded because of highly reversible interactions with grain surfaces. Judging from the slope of the substantive and protracted tail of the breakthrough curve for the 1.8-μm microspheres, almost all (>99%) predictably would be recovered within ∼4000 pore volumes. This suggests that once contaminated, the volcanic ash soil could serve as a reservoir for subsequent contamination of groundwater, at least for pathogens of similar size or smaller. Because of the highly reversible nature of organic colloid immobilization in this soil type, C. parvum could contaminate surface water should overland flow during heavy precipitation events pick up near-surface grains to which they are attached. Surprisingly, oocyst and microsphere attachment to the reference soil from Illinois appeared to be at least as sensitive to changes in pH as was observed for the red, metal-oxide rich soil from Oahu. In contrast, colloidal attachment in the organic-rich, volcanic ash soil was relatively insensitive to changes in pH in spite of the high iron content. Given the fundamental differences in transport behavior of oocyst-sized colloids within the two volcanic soils of similar origin, agricultural practices modified to lessen C. parvum contamination of ground or surface water would necessitate taking the individual soil properties into account. Copyright © 2010 Elsevier Ltd. All rights reserved.

Comparison of transport and attachment behaviors of Cryptosporidium parvum oocysts and oocyst-sized microspheres being advected through three minerologically different granular porous media

USGS Publications Warehouse

Mohanram, Arvind; Ray, Chittaranjan; Harvey, Ronald W.; Metge, David W.; Ryan, Joseph N.; Chorover, Jon; Eberl, D.D.

2010-01-01

In order to gain more information about the fate of Cryptosporidium parvum oocysts in tropical volcanic soils, the transport and attachment behaviors of oocysts and oocyst-sized polystyrene microspheres were studied in the presence of two soils. These soils were chosen because of their differing chemical and physical properties, i.e., an organic-rich (43–46% by mass) volcanic ash-derived soil from the island of Hawaii, and a red, iron (22–29% by mass), aluminum (29–45% by mass), and clay-rich (68–76% by mass) volcanic soil from the island of Oahu. A third agricultural soil, an organic- (13% by mass) and quartz-rich (40% by mass) soil from Illinois, was included for reference. In 10-cm long flow-through columns, oocysts and microspheres advecting through the red volcanic soil were almost completely (98% and 99%) immobilized. The modest breakthrough resulted from preferential flow-path structure inadvertently created by soil-particle aggregation during the re-wetting process. Although a high (99%) removal of oocysts and microsphere within the volcanic ash soil occurred initially, further examination revealed that transport was merely retarded because of highly reversible interactions with grain surfaces. Judging from the slope of the substantive and protracted tail of the breakthrough curve for the 1.8-μm microspheres, almost all (>99%) predictably would be recovered within ∼4000 pore volumes. This suggests that once contaminated, the volcanic ash soil could serve as a reservoir for subsequent contamination of groundwater, at least for pathogens of similar size or smaller. Because of the highly reversible nature of organic colloid immobilization in this soil type, C. parvum could contaminate surface water should overland flow during heavy precipitation events pick up near-surface grains to which they are attached. Surprisingly, oocyst and microsphere attachment to the reference soil from Illinois appeared to be at least as sensitive to changes in pH as was observed for the red, metal-oxide rich soil from Oahu. In contrast, colloidal attachment in the organic-rich, volcanic ash soil was relatively insensitive to changes in pH in spite of the high iron content. Given the fundamental differences in transport behavior of oocyst-sized colloids within the two volcanic soils of similar origin, agricultural practices modified to lessen C. parvum contamination of ground or surface water would necessitate taking the individual soil properties into account.

Comparison of transport and attachment behaviors of Cryptosporidium parvum oocysts and oocyst-sized microspheres being advected through three minerologically different granular porous media

USGS Publications Warehouse

Mohanram, A.; Ray, C.; Harvey, R.W.; Metge, D.W.; Ryan, J.N.; Chorover, J.; Eberl, D.D.

2010-01-01

In order to gain more information about the fate of Cryptosporidium parvum oocysts in tropical volcanic soils, the transport and attachment behaviors of oocysts and oocyst-sized polystyrene microspheres were studied in the presence of two soils. These soils were chosen because of their differing chemical and physical properties, i.e., an organic-rich (43-46% by mass) volcanic ash-derived soil from the island of Hawaii, and a red, iron (22-29% by mass), aluminum (29-45% by mass), and clay-rich (68-76% by mass) volcanic soil from the island of Oahu. A third agricultural soil, an organic- (13% by mass) and quartz-rich (40% by mass) soil from Illinois, was included for reference. In 10-cm long flow-through columns, oocysts and microspheres advecting through the red volcanic soil were almost completely (98% and 99%) immobilized. The modest breakthrough resulted from preferential flow-path structure inadvertently created by soil-particle aggregation during the re-wetting process. Although a high (99%) removal of oocysts and microsphere within the volcanic ash soil occurred initially, further examination revealed that transport was merely retarded because of highly reversible interactions with grain surfaces. Judging from the slope of the substantive and protracted tail of the breakthrough curve for the 1.8-??m microspheres, almost all (>99%) predictably would be recovered within ~4000 pore volumes. This suggests that once contaminated, the volcanic ash soil could serve as a reservoir for subsequent contamination of groundwater, at least for pathogens of similar size or smaller. Because of the highly reversible nature of organic colloid immobilization in this soil type, C. parvum could contaminate surface water should overland flow during heavy precipitation events pick up near-surface grains to which they are attached. Surprisingly, oocyst and microsphere attachment to the reference soil from Illinois appeared to be at least as sensitive to changes in pH as was observed for the red, metal-oxide rich soil from Oahu. In contrast, colloidal attachment in the organic-rich, volcanic ash soil was relatively insensitive to changes in pH in spite of the high iron content. Given the fundamental differences in transport behavior of oocyst-sized colloids within the two volcanic soils of similar origin, agricultural practices modified to lessen C. parvum contamination of ground or surface water would necessitate taking the individual soil properties into account. ?? 2010.

3D near-surface soil response from H/V ambient-noise ratios

USGS Publications Warehouse

Wollery, E.W.; Street, R.

2002-01-01

The applicability of the horizontal-to-vertical (H/V) ambient-noise spectral ratio for characterizing earthquake site effects caused by nearsurface topography and velocity structures was evaluated at sites underlain by thick (i.e. >100 m) sediment deposits near the southern-end of the New Madrid seismic zone in the central United States. Three-component ambient-noise and velocity models derived from seismic (shearwave) refraction/reflection surveys showed that a relatively horizontal, sharp shear-wave velocity interface in the soil column resulted in an H/V spectral ratio with a single well-defined peak. Observations at sites with more than one sharp shear-wave velocity contrast and horizontally arranged soil layers resulted in at least two well-defined H/V spectral ratio peaks. Furthermore, at sites where there were sharp shear-wave velocity contrasts in nonhorizontal, near-surface soil layers, the H/V spectra exhibited a broad-bandwidth, relatively low amplitude signal instead of a single well-defined peak. ?? 2002 Elsevier Science Ltd. All rights reserved.

Benchmarking a Soil Moisture Data Assimilation System for Agricultural Drought Monitoring

NASA Technical Reports Server (NTRS)

Hun, Eunjin; Crow, Wade T.; Holmes, Thomas; Bolten, John

2014-01-01

Despite considerable interest in the application of land surface data assimilation systems (LDAS) for agricultural drought applications, relatively little is known about the large-scale performance of such systems and, thus, the optimal methodological approach for implementing them. To address this need, this paper evaluates an LDAS for agricultural drought monitoring by benchmarking individual components of the system (i.e., a satellite soil moisture retrieval algorithm, a soil water balance model and a sequential data assimilation filter) against a series of linear models which perform the same function (i.e., have the same basic inputoutput structure) as the full system component. Benchmarking is based on the calculation of the lagged rank cross-correlation between the normalized difference vegetation index (NDVI) and soil moisture estimates acquired for various components of the system. Lagged soil moistureNDVI correlations obtained using individual LDAS components versus their linear analogs reveal the degree to which non-linearities andor complexities contained within each component actually contribute to the performance of the LDAS system as a whole. Here, a particular system based on surface soil moisture retrievals from the Land Parameter Retrieval Model (LPRM), a two-layer Palmer soil water balance model and an Ensemble Kalman filter (EnKF) is benchmarked. Results suggest significant room for improvement in each component of the system.

A comparative study of soil water movement under different vegetation covers

NASA Astrophysics Data System (ADS)

FERNANDO, A.; Tanaka, T.

2002-05-01

Vegetation, varying widely floristically, structurally, and in spatial distribution, is a complex phenomenon, delicately adjusted within itself and to its broader environment. To investigate the soil water movement of different vegetation covers, soil physical properties, and pressure head of soil water, have been analysed in a pine forest and adjacent disturbed grassland at the Terrestrial Environmental Research Centre (ERC) of Tsukuba University, Japan. Our results of the soil physical properties showed significant differences under different vegetation. At the forest site, the total porosity was nearly constant, i.e. 81% to 84%, from the ground surface to the depth of 70 cm, and decreased uniformly with the depth to reach 63.2% at 150 cm. At the grassland site, the total porosity was about 70% near the ground surface, however, expeditiously decreased to approximately 62% between the depths of 10 and 40 cm. Below these depths the total porosity increased to a maximum of about 77% between the depths of 50 and 80 cm, then decreased again to 54.9% at 150 cm. The total pressure head indicated that the evapotranspiration zone of the pine forest was 70 cm but was 50 cm in the grassland. KEY WORDS: Natural pine forest, Disturbed grassland, Soil water movement, Soil physical properties, Evaporation effective zone.

Quantification of soil structure based on Minkowski functions

NASA Astrophysics Data System (ADS)

Vogel, H.-J.; Weller, U.; Schlüter, S.

2010-10-01

The structure of soils and other geologic media is a complex three-dimensional object. Most of the physical material properties including mechanical and hydraulic characteristics are immediately linked to the structure given by the pore space and its spatial distribution. It is an old dream and still a formidable challenge to relate structural features of porous media to their functional properties. Using tomographic techniques, soil structure can be directly observed at a range of spatial scales. In this paper we present a scale-invariant concept to quantify complex structures based on a limited set of meaningful morphological functions. They are based on d+1 Minkowski functionals as defined for d-dimensional bodies. These basic quantities are determined as a function of pore size or aggregate size obtained by filter procedures using mathematical morphology. The resulting Minkowski functions provide valuable information on the size of pores and aggregates, the pore surface area and the pore topology having the potential to be linked to physical properties. The theoretical background and the related algorithms are presented and the approach is demonstrated for the pore structure of an arable soil and the pore structure of a sand both obtained by X-ray micro-tomography. We also analyze the fundamental problem of limited resolution which is critical for any attempt to quantify structural features at any scale using samples of different size recorded at different resolutions. The results demonstrate that objects smaller than 5 voxels are critical for quantitative analysis.

Critical Zone Co-dynamics: Quantifying Interactions between Subsurface, Land Surface, and Vegetation Properties Using UAV and Geophysical Approaches

NASA Astrophysics Data System (ADS)

Dafflon, B.; Leger, E.; Peterson, J.; Falco, N.; Wainwright, H. M.; Wu, Y.; Tran, A. P.; Brodie, E.; Williams, K. H.; Versteeg, R.; Hubbard, S. S.

2017-12-01

Improving understanding and modelling of terrestrial systems requires advances in measuring and quantifying interactions among subsurface, land surface and vegetation processes over relevant spatiotemporal scales. Such advances are important to quantify natural and managed ecosystem behaviors, as well as to predict how watershed systems respond to increasingly frequent hydrological perturbations, such as droughts, floods and early snowmelt. Our study focuses on the joint use of UAV-based multi-spectral aerial imaging, ground-based geophysical tomographic monitoring (incl., electrical and electromagnetic imaging) and point-scale sensing (soil moisture sensors and soil sampling) to quantify interactions between above and below ground compartments of the East River Watershed in the Upper Colorado River Basin. We evaluate linkages between physical properties (incl. soil composition, soil electrical conductivity, soil water content), metrics extracted from digital surface and terrain elevation models (incl., slope, wetness index) and vegetation properties (incl., greenness, plant type) in a 500 x 500 m hillslope-floodplain subsystem of the watershed. Data integration and analysis is supported by numerical approaches that simulate the control of soil and geomorphic characteristic on hydrological processes. Results provide an unprecedented window into critical zone interactions, revealing significant below- and above-ground co-dynamics. Baseline geophysical datasets provide lithological structure along the hillslope, which includes a surface soil horizon, underlain by a saprolite layer and the fractured Mancos shale. Time-lapse geophysical data show very different moisture dynamics in various compartments and locations during the winter and growing season. Integration with aerial imaging reveals a significant linkage between plant growth and the subsurface wetness, soil characteristics and the topographic gradient. The obtained information about the organization and connectivity of the landscape is being transferred to larger regions using aerial imaging and will be used to constrain multi-scale, multi-physics hydro-biogeochemical simulations of the East River watershed response to hydrological perturbations.

Evolving soils and hydrologic connectivity in semiarid hillslopes

NASA Astrophysics Data System (ADS)

Saco, Patricia M.

2015-04-01

Soil moisture availability is essential for the stability and resilience of semiarid ecosystems. In these ecosystems the amount of soil moisture available for vegetation growth and survival is intrinsically related to the way water is redistributed, that is from source to sink areas, and therefore prescribed by the hydrologic connectivity of the landscape. Recent studies have shown that hydrologic connectivity is highly dynamic and linked to the coevolution of geomorphic, soil and vegetation structures at a variety of spatial and temporal scales. This study investigates the effect of evolving soil depths on hydrologic connectivity using a modelling framework. The focus is on Australian semiarid hillslopes with patterned vegetation that result from coevolving landforms, soils, water redistribution, and vegetation patterns. We present and analyse results from simulations using a coupled landform evolution-dynamic vegetation model, which includes a soil depth evolution module and accounts for soil production and sediment erosion and deposition processes. We analyse the effect of soils depths on surface connectivity for a range of biotic (plant functional type strategies) and abiotic (slope and erodibility) conditions. The analysis shows that different plant functional types, through their varying facilitation strategies, have a profound effect on soils depths and therefore affect hydrologic connectivity and soil moisture patterns. This interplay becomes particularly important for systems that coevolve to have very shallow soils. In this case soil depth becomes the key factor prescribing surface connectivity and available soil moisture for plants, which affect the recovery of the system after disturbance. Conditions for the existence of threshold behaviour for which small perturbations can trigger a sudden increase in hydrologic connectivity, reduced soil moisture availability and decrease in productivity leading to degraded states are investigated. Critical implications for effective restoration efforts are discussed.

A tracer experiment to study flow paths of water in a forest soil

NASA Astrophysics Data System (ADS)

Feyen, H.; Wunderli, H.; Wydler, H.; Papritz, A.

1999-12-01

This contribution discusses a tracer experiment, which was performed to study the flow paths of water in a macroporous forest soil. The experiment was performed in the framework of a study on the cycling of nitrogen in forested Prealpine catchments, in which losses of nitrate from virtually pristine areas were observed. Two soil plots with distinct micro-topography and top-soil were investigated: a well drained mor humus on a mound and a wet muck humus in a small depression. To reveal the effect of the soil horizons on the flow regime, tracers were applied both onto the soil surface and injected into the sub-soil. Tracers injected directly into the gleyic sub-soil reached the outlet (at a distance of 3.3 m) about 1000 times faster than could be expected from the saturated hydraulic conductivity of the soil matrix. Peak concentrations were observed after 18 (muck humus, tracer recovery 31%) to 70 min (mor humus, tracer recovery 40%). The peak concentration was 10 times smaller on the drier mor humus plot as compared to the muck humus. The mobile water content of the sub-soil varied between 0.5 (muck humus) and 1.3% (mor humus) of the total available soil water. The discrepancy in residence time, peak concentration and volume of mobile water between both sub-soils can be attributed to the differently structured sub-soil (longer travel distance and mixing volume in the drier mor humus). Tracers applied onto the soil surface resulted in a much slower breakthrough (tracer peaks after 400-700 min). Thus, in contrast to the sub-soil, flow through the matrix was the predominating transport process in the upper humus layers of both plots.

Effects of Microbial and Phosphate Amendments on the Bioavailability of Lead (Pb) in Shooting Range Soil

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brigmon, Robin; Wilson, Christina; Knox, Anna

Heavy metals including lead (Pb) are released continually into the environment as a result of industrial, recreational, and military activities. Lead ranked number two on the CERCLA Priority List of Hazardous Substances and was identified as a major hazardous chemical found on 47% of USEPA's National Priorities List sites (Hettiarachchi and Pierzynski 2004). In-situ remediation of lead (Pb) contaminated soils may be accomplished by changing the soil chemistry and structure with the application of microbial and phosphate amendments. Soil contaminated with lead bullets was collected from the surface of the berm at Savannah River Site (SRS) Small Arms Training Academymore » (SATA) in Aiken, SC. While uncontaminated soils typically have Pb levels ranging from 2 to 200 mg/kg (Berti et al. 1998), previous analysis show Pb levels of the SATA berm to reach 8,673 mg/kg. Biosurfactants are surface-active compounds naturally produced by soil bacteria that can bind metals. Biosurfactants have a wide variety of chemical structures that reduce interfacial surface tensions (Jennings and Tanner 2000) and have demonstrated efficient metal complexion (Lin 1996). Biosurfactants also have the potential to change the availability of natural organic matter (Strong-Gunderson 1995). Two types of bacteria, Alcaligenes piechaudii and Pseudomonas putida, were employed as amendments based on their ability to produce biosurfactants and survive in metal-contaminated soils. Apatites (calcium phosphate compounds) are important in the formation of Pb phosphates. Pb phosphates form rapidly when phosphate is available and are the most stable environmental form of lead in soil (Ruby et al.1998). Pyromorphites in particular remain insoluble under a wide range of environmental conditions (Zhang et al. 1998). The three apatites evaluated in the current study were North Carolina apatite (NCA), Florida apatite (FA), and biological apatite (BA). BA is ground fish bone that has few impurities such as As, Cr, or U and contains about 27% total phosphate, most of which is available. FA and NCA are two types of rock phosphates that release small amounts of phosphate over time. Total phosphate is around 30% with only 1-2% phosphate available (Knox et al. 2005). In this study, we describe the influence of combining the two microbial and three phosphate amendments on reducing lead bioavailability in shooting range soil.« less

Laser Absorption spectrometer instrument for tomographic 2D-measurement of climate gas emission from soils

NASA Astrophysics Data System (ADS)

Seidel, Anne; Wagner, Steven; Dreizler, Andreas; Ebert, Volker

2014-05-01

One of the most intricate effects in climate modelling is the role of permafrost thawing during the global warming process. Soil that has formerly never totally lost its ice cover now emits climate gases due to melting processes[1]. For a better prediction of climate development and possible feedback mechanisms, insights into physical procedures (like e.g. gas emission from underground reservoirs) are required[2]. Therefore, a long-term quantification of greenhouse gas concentrations (and further on fluxes) is necessary and the related structures that are responsible for emission need to be identified. In particular the spatial heterogeneity of soils caused by soil internal structures (e.g. soil composition changes or surface cracks) or by surface modifications (e.g. by plant growth) generate considerable complexities and difficulties for local measurements, for example with soil chambers. For such situations, which often cannot be avoided, a spatially resolved 2D-measurement to identify and quantify the gas emission from the structured soil would be needed, to better understand the influence of the soil sub-structures on the emission behavior. Thus we designed a spatially scanning laser absorption spectrometer setup to determine a 2D-gas concentration map in the soil-air boundary layer. The setup is designed to cover the surfaces in the range of square meters in a horizontal plane above the soil to be investigated. Existing field instruments for gas concentration or flux measurements are based on point-wise measurements, so structure identification is very tedious or even impossible. For this reason, we have developed a tomographic in-situ instrument based on TDLAS ('tunable diode laser absorption spectroscopy') that delivers absolute gas concentration distributions of areas with 0.8m × 0.8m size, without any need for reference measurements with a calibration gas. It is a simple and robust device based on a combination of scanning mirrors and reflecting foils, so that only very little optical alignment is necessary in the field. The measurement rate for a complete 2D field is presently up to 2.5 Hz. The measurement field size is currently limited only by laboratory conditions and could be extended easily to the range of several meters, as previous tests have confirmed[3]. A fast laser tuning rate of more than 5 kHz leads to high measurement path density, and overall more than 70% of a square shaped field area is covered. With this instrument, measurements of H2O- and CH4 - concentration distributions have taken place so far. We are going to discuss the instrument setup and the spectroscopic performance and present numerical studies concerning the tomographic reconstruction quality as well as first 2D reconstructions in the laboratory. The applicability to 2D CO2 detection and the improvement of frame rate and reconstruction quality using faster laser tuning will be discussed. [1] K. M. Walter Anthony, P. Anthony, G. Grosse, and J. Chanton, 'Geologic methane seeps along boundaries of Arctic permafrost thaw and melting glaciers,' Nat. Geosci., vol. 5, no. 6, pp. 419-426, May 2012. [2] B. Elberling, A. Michelsen, C. Schädel, E. A. G. Schuur, H. H. Christiansen, L. Tamstorf, M. P. Berg, and C. Sigsgaard, 'Long-term CO2 production following permafrost thaw,' Nat. Clim. Chang., vol. 3, no. 10, pp. 890-894, 2013. [3] A. Seidel, S. Wagner, and V. Ebert, 'TDLAS-based open-path laser hygrometer using simple reflective foils as scattering targets,' Appl. Phys. B, vol. 109, no. 3, pp. 497-504, Oct. 2012.

Theoretical considerations of soil retention. [dirtying of solar energy devices

NASA Technical Reports Server (NTRS)

Cuddihy, E. F.

1980-01-01

The performance of solar energy devices is adversely affected by surface soiling, and generally, the loss of performance increases with increases in the quantity of soil retained on their surfaces. To minimize performance losses caused by soiling, solar devices should not only be deployed in low soiling geographical areas, but employ surfaces or surfacing materials having low affinity for soil retention, maximum susceptibility to be naturally cleaned by wind, rain and snow, and to be readily cleanable by simple and inexpensive maintenance cleaning techniques. This article describes known and postulated mechanisms of soil retention on surfaces, and infers from these mechanisms that low soiling and easily cleanable surfaces should have low surface energy, and be hard, smooth, hydrophobic and chemically clean of sticky materials and water soluble salts.

[Stabilization of Cadmium Contaminated Soils by Ferric Ion Modified Attapulgite (Fe/ATP)--Characterizations and Stabilization Mechanism].

PubMed

Rong, Yang; Li, Rong-bo; Zhou, Yong-li; Chen, Jing; Wang, Lin-ling; Lu, Xiao-hua

2015-08-01

Ferric ion modified attapulgite (Fe/ATP) was prepared by impregnation and its structure and morphology were characterized. The toxicity characteristic leaching procedure (TCLP) was used to evaluate the effect of Cadmium( Cd) stabilization in soil with the addition of attapulgite (ATP) and Fe/ATP. The stabilization mechanism of Cd was further elucidated by comparing the morphologies and structure of ATP and Fe/ATP before and after Cd adsorption. Fe/ATP exhibited much better adsorption capacity than ATP, suggesting different adsorption mechanisms occurred between ATP and Fe/ATP. The leaching concentrations of Cd in soil decreased by 45% and 91% respectively, with the addition of wt. 20% ATP and Fe/ATP. The former was attributed to the interaction between Cd2 and --OH groups by chemical binding to form inner-sphere complexes in ATP and the attachment between Cd2+ and the defect sites in ATP framework. Whereas Cd stabilization with Fe/ATP was resulted from the fact that the active centers (--OH bonds or O- sites) on ATP could react with Fe3+ giving Fe--O--Cd-- bridges, which helped stabilize Cd in surface soil. What'more, the ferric oxides and metal hydroxides on the surface of ATP could interact with Cd, probably by the formation of cadmium ferrite. In conclusion, Fe/ATP, which can be easily prepared, holds promise as a potential low-cost and environmental friendly stabilizing agent for remediation of soil contaminated with heavy metals.

Porous media augmented with biochar for the retention of E. coli

NASA Astrophysics Data System (ADS)

Kolotouros, Christos A.; Manariotis, Ioannis D.; Karapanagioti, Hrissi K.

2016-04-01

A significant number of epidemic outbreaks has been attributed to waterborne fecal-borne pathogenic microorganisms from contaminated ground water. The transport of pathogenic microorganisms in groundwater is controlled by physical and chemical soil properties like soil structure, texture, percent water saturation, soil ionic strength, pore-size distribution, soil and solution pH, soil surface charge, and concentration of organic carbon in solution. Biochar can increase soil productivity by improving both chemical and physical soil properties. The mixing of biochar into soils may stimulate microbial population and activate dormant soil microorganisms. Furthermore, the application of biochar into soil affects the mobility of microorganisms by altering the physical and chemical properties of the soil, and by retaining the microorganisms on the biochar surface. The aim of this study was to investigate the effect of biochar mixing into soil on the transport of Escherichia coli in saturated porous media. Initially, batch experiments were conducted at two different ionic strengths (1 and 150 mM KCl) and at varying E. coli concentrations in order to evaluate the retention of E. coli on biochar in aqueous solutions. Kinetic analysis was conducted, and three isotherm models were employed to analyze the experimental data. Column experiments were also conducted in saturated sand columns augmented with different biochar contents, in order to examine the effect of biochar on the retention of E. coli. The Langmuir model fitted better the retention experimental data, compared to Freundlich and Tempkin models. The retention of E. coli was enhanced at lower ionic strength. Finally, biochar-augmented sand columns were more capable in retaining E. coli than pure sand columns.

Differences in the Activities of Eight Enzymes from Ten Soil Fungi and Their Possible Influences on the Surface Structure, Functional Groups, and Element Composition of Soil Colloids

PubMed Central

Wang, Wenjie; Li, Yanhong; Wang, Huimei; Zu, Yuangang

2014-01-01

How soil fungi function in soil carbon and nutrient cycling is not well understood by using fungal enzymatic differences and their interactions with soil colloids. Eight extracellular enzymes, EEAs (chitinase, carboxymethyl cellulase, β-glucosidase, protease, acid phosphatase, polyphenol oxidase, laccase, and guaiacol oxidase) secreted by ten fungi were compared, and then the fungi that showed low and high enzymatic activity were co-cultured with soil colloids for the purpose of finding fungi-soil interactions. Some fungi (Gomphidius rutilus, Russula integra, Pholiota adiposa, and Geastrum mammosum) secreted 3–4 enzymes with weak activities, while others (Cyathus striatus, Suillus granulate, Phallus impudicus, Collybia dryophila, Agaricus sylvicola, and Lactarius deliciosus) could secret over 5 enzymes with high activities. The differences in these fungi contributed to the alterations of functional groups (stretching bands of O-H, N-H, C-H, C = O, COO- decreased by 11–60%, while P = O, C-O stretching, O-H bending and Si-O-Si stretching increased 9–22%), surface appearance (disappearance of adhesive organic materials), and elemental compositions (11–49% decreases in C1s) in soil colloids. Moreover, more evident changes were generally in high enzymatic fungi (C. striatus) compared with low enzymatic fungi (G. rutilus). Our findings indicate that inter-fungi differences in EEA types and activities might be responsible for physical and chemical changes in soil colloids (the most active component of soil matrix), highlighting the important roles of soil fungi in soil nutrient cycling and functional maintenance. PMID:25398013

Differences in the activities of eight enzymes from ten soil fungi and their possible influences on the surface structure, functional groups, and element composition of soil colloids.

PubMed

Wang, Wenjie; Li, Yanhong; Wang, Huimei; Zu, Yuangang

2014-01-01

How soil fungi function in soil carbon and nutrient cycling is not well understood by using fungal enzymatic differences and their interactions with soil colloids. Eight extracellular enzymes, EEAs (chitinase, carboxymethyl cellulase, β-glucosidase, protease, acid phosphatase, polyphenol oxidase, laccase, and guaiacol oxidase) secreted by ten fungi were compared, and then the fungi that showed low and high enzymatic activity were co-cultured with soil colloids for the purpose of finding fungi-soil interactions. Some fungi (Gomphidius rutilus, Russula integra, Pholiota adiposa, and Geastrum mammosum) secreted 3-4 enzymes with weak activities, while others (Cyathus striatus, Suillus granulate, Phallus impudicus, Collybia dryophila, Agaricus sylvicola, and Lactarius deliciosus) could secret over 5 enzymes with high activities. The differences in these fungi contributed to the alterations of functional groups (stretching bands of O-H, N-H, C-H, C = O, COO- decreased by 11-60%, while P = O, C-O stretching, O-H bending and Si-O-Si stretching increased 9-22%), surface appearance (disappearance of adhesive organic materials), and elemental compositions (11-49% decreases in C1s) in soil colloids. Moreover, more evident changes were generally in high enzymatic fungi (C. striatus) compared with low enzymatic fungi (G. rutilus). Our findings indicate that inter-fungi differences in EEA types and activities might be responsible for physical and chemical changes in soil colloids (the most active component of soil matrix), highlighting the important roles of soil fungi in soil nutrient cycling and functional maintenance.

Interactions Between Wind Erosion, Vegetation Structure, and Soil Stability in Groundwater Dependent Plant Communities

NASA Astrophysics Data System (ADS)

Vest, K. R.; Elmore, A. J.; Okin, G. S.

2009-12-01

Desertification is a human induced global phenomenon causing a loss of biodiversity and ecosystem productivity. Semi-arid grasslands are vulnerable to anthropogenic impacts (i.e., groundwater pumping and surface water diversion) that decrease vegetation cover and increase bare soil area leading to a greater probability of soil erosion, potentially enhancing feedback processes associated with desertification. To enhance our understanding of interactions between anthropogenic, physical, and biological factors causing desertification, this study used a combination of modeling and field observations to examine the relationship between chronic groundwater pumping and vegetation cover change and its effects on soil erosion and stability. The work was conducted in Owens Valley California, where a long history of groundwater pumping and surface water diversion has lead to documented vegetation changes. The work examined hydrological, ecological and biogeochemical factors across thirteen sites in Owens Valley. We analyzed soil stability, vegetation and gap size, soil organic carbon, and we also installed Big Spring Number Eight (BSNE) catchers to calculate mass transport of aeolian sediment across sites. Mass transport calculations were used to validate a new wind erosion model that represents the effect of porous vegetation on surface windshear velocity. Results across two field seasons show that the model can be used to predict mass transport, and areas with increased groundwater pumping show a greater susceptibility to erosion. Sediment collected in BSNE catchers was positively correlated with site gap size. Additionally, areas with larger gap sizes have a greater threshold shear velocity and soil stability, yet mass transport was greater at these sites than at sites with smaller gap sizes. Although modeling is complicated by spatial variation in multiple model parameters (e.g., gap size, threshold shear velocity in gaps), our results support the hypothesis that soils with high organic matter are being eroded following the loss of vegetation cover due to groundwater decline leaving behind bare soil surfaces with less fertility hampering vegetation reestablishment. Desertification in this system is apparently easily initiated through groundwater decline due to the high friability of these meadow soils.

Soil Tillage Conservation and its Effect on Soil Properties Bioremediation and Sustained Production of Crops

NASA Astrophysics Data System (ADS)

Rusu, Teodor; Ioana Moraru, Paula; Muresan, Liliana; Andriuca, Valentina; Cojocaru, Olesea

2017-04-01

Soil Tillage Conservation (STC) is considered major components of agricultural technology for soil conservation strategies and part of Sustainable Agriculture (SA). Human action upon soil by tillage determines important morphological, physical-chemical and biological changes, with different intensities and evaluative directions. Nowadays, internationally is unanimous accepted the fact that global climatic changes are the results of human intervention in the bio-geo-chemical water and material cycle, and the sequestration of carbon in soil is considered an important intervention to limit these changes. STC involves reducing the number of tillage's (minimum tillage) to direct sowing (no-tillage) and plant debris remains at the soil surface in the ratio of at least 30%. Plant debris left on the soil surface or superficial incorporated contributes to increased biological activity and is an important source of carbon sequestration. STC restore soil structure and improve overall soil drainage, allowing more rapid infiltration of water into soil. The result is a soil bioremediation, more productive, better protected against wind and water erosion and requires less fuel for preparing the germinative bed. Carbon sequestration in soil is net advantageous, improving the productivity and sustainability. We present the influence of conventional plough tillage system on soil, water and organic matter conservation in comparison with an alternative minimum tillage (paraplow, chisel plow and rotary harrow) and no-tillage system. The application of STC increased the organic matter content 0.8 to 22.1% and water stabile aggregate content from 1.3 to 13.6%, in the 0-30 cm depth, as compared to the conventional system. For the organic matter content and the wet aggregate stability, the statistical analysis of the data showed, increasing positive significance of STC. While the soil fertility and the wet aggregate stability were initially low, the effect of conservation practices on the soil features resulted in a positive impact on the water permeability of the soil. Availability of soil moisture during the crop growth resulted in better plant water status. Subsequent release of conserved soil water regulated proper plant water status, soil structure, and lowered soil penetrometer resistance. Productions obtained at STC did not have significant differences for the wheat and maize crop but were higher for soybean. The advantages of minimum soil tillage systems for Romanian pedo-climatic conditions can be used to improve methods in low producing soils with reduced structural stability on sloped fields, as well as measures of water and soil conservation on the whole agroecosystem. Presently, it is necessary to make a change concerning the concept of conservation practices and to consider a new approach regarding the good agricultural practice. We need to focus on an upper level concerning conservation by focusing on soil quality. Carbon management is necessary for a complexity of matters including soil, water management, field productivity, biological fuel and climatic change. In conclusion a Sustainable Agriculture includes a range of complementary agricultural practices: (i) minimum soil tillage (through a system of reduced tillage or no-tillage) to preserve the structure, fauna and soil organic matter; (ii) permanent soil cover (cover crops, residues and mulches) to protect the soil and help to remove and control weeds; (iii) various combinations and rotations of the crops which stimulate the micro-organisms in the soil and controls pests, weeds and plant diseases. Acknowledgements: This paper was performed under the frame of the Partnership in priority domains - PNII, developed with the support of MEN-UEFISCDI, project no. PN-II-PT-PCCA-2013-4-0015: Expert System for Risk Monitoring in Agriculture and Adaptation of Conservative Agricultural Technologies to Climate Change, and International Cooperation Program - Sub-3.1. Bilateral AGROCEO c. no. 21BM/2016, PN-III-P3-3.1-PM-RO-MD-2016-0034: The comparative evaluation of conventional and conservative tillage systems regarding carbon sequestration and foundation of sustainable agroecosystems.

Temperature-dependent residual shear strength characteristics of smectite-bearing landslide soils

NASA Astrophysics Data System (ADS)

Shibasaki, Tatsuya; Matsuura, Sumio; Hasegawa, Yoichi

2017-02-01

This paper presents experimental investigations regarding the effect of temperature on the residual strength of landslide soils at slow-to-moderate shearing velocities. We performed ring-shear tests on 23 soil samples at temperatures of 6-29°C. The test results show that the shear strength of smectite-rich soils decreased when temperatures were relatively low. These positive temperature effects (strength losses at lower temperatures) observed for smectite-bearing soils are typical under relatively slow shearing rates. In contrast, under relatively high shearing rates, strength was gained as temperature decreased. As rheological properties of smectite suspensions are sensitive to environmental factors, such as temperature, pH, and dissolved ions, we inferred that temperature-dependent residual strengths of smectitic soils are also attributed to their specific rheological properties. Visual and scanning electron microscope observations of Ca-bentonite suggest that slickensided shear surfaces at slow shearing rates are very shiny and smooth, whereas those at moderate shearing rates are not glossy and are slightly turbulent, indicating that platy smectite particles are strongly orientated at slow velocities. The positive temperature effect is probably due to temperature-dependent microfriction that is mobilized in the parallel directions of the sheet structure of hydrous smectite particles. On the contrary, the influence of microviscous resistance, which appears in the vertical directions of the lamination, is assumed to increase at faster velocities. Our results imply that if slip-surface soils contain high fractions of smectite, decreases in ground temperature can lead to lowered shear resistance of the slip surface and trigger slow landslide movement.

Determination of Fluxes and their Source Partitioning from high-resolution Profile Measurements of Wind Speed and Scalars within and above short Canopies

NASA Astrophysics Data System (ADS)

Graf, A.; Ney, P.

2017-12-01

A continuously moving elevator-based system is described to measure vertical profiles of wind speed, temperature, CO2 and H2O within and above short plant canopies with a vertical resolution in the centimeter range. On sample days in 2015 to 2017, we measured profiles from the soil surface to 2 m a.g.l. in a crop rotation including wheat, barley, bare soil, winter catch crops and sugarbeet, with canopy heights of up to 1 m. Profiles over bare soil or very short canopies could be described well by fitting Monin-Obukhov-like profiles, and the derived fluxes of momentum and all three scalars matched well those of a nearby eddy-covariance station. In green canopies during the day, CO2 profiles clearly indicated the plant sink and soil source by a local minimum in the canopy and a maximum at the soil surface. H2O profiles, indicating sources both in the canopy and at the soil surface, did or did not show a local minimum between both, depending on canopy structure and turbulence. Temperature profiles showed various shapes including solar incident angle effects, and often the expected opposing signs of thermal stability between the subcanopy and the roughness sublayer. Finally, we test different existing parametrizations to estimate the vertical source / sink distribution from the measured profiles, compare the resulting vertically integrated fluxes to eddy-covariance based net fluxes, and discuss limitations and needed improvements to quantify subcanopy soil respiration and evaporation from such approaches.

Effects of warming on the structure and function of a boreal black spruce forest

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stith T.Gower

2010-03-03

A strong argument can be made that there is a greater need to study the effect of warming on boreal forests more than on any other terrestrial biome. Boreal forests, the second largest forest biome, are predicted to experience the greatest warming of any forest biome in the world, but a process-based understanding of how warming will affect the structure and function of this economically and ecologically important forest biome is lacking. The effects of warming on species composition, canopy structure and biogeochemical cycles are likely to be complex; elucidating the underlying mechanisms will require long-term whole-ecosystem manipulation to capturemore » all the complex feedbacks (Shaver et al. 2000, Rustad et al. 2001, Stromgren 2001). The DOE Program for Ecosystem Research funded a three year project (2002-2005) to use replicated heated chambers on soil warming plots in northern Manitoba to examine the direct effects of whole-ecosystem warming. We are nearing completion of our first growing season of measurements (fall 2004). In spite of the unforeseen difficulty of installing the heating cable, our heating and irrigation systems worked extremely well, maintaining environmental conditions within 5-10% of the specified design 99% of the time. Preliminary data from these systems, all designed and built by our laboratory at the University of Wisconsin, support our overall hypothesis that warming will increase the carbon sink strength of upland boreal black spruce forests. I request an additional three years of funding to continue addressing the original objectives: (1) Examine the effect of warming on phenology of overstory, understory and bryophyte strata. Sap flux systems and dendrometer bands, monitored by data loggers, will be used to quantify changes in phenology and water use. (2) Quantify the effects of warming on nitrogen and water use by overstory, understory and bryophytes. (3) Compare effects of warming on autotrophic respiration and above- and belowground net primary production (NPP) budgets. Autotrophic respiration budgets will be constructed using chamber measurements for each tissue and NPP and standard allometry techniques (Gower et al. 1999). (4) Compare microbial and root dynamics, and net soil surface CO2 flux, of control and warmed soils to identify causes that may explain the hypothesized minimal effect of soil warming on soil surface CO2 flux. Fine root production and turnover will be quantified using minirhizotrons, and microbial dynamics will be determined using laboratory mineralization incubations. Soil surface CO2 flux will be measured using automated soil surface CO2 flux systems and portable CO2 analyzers. The proposed study builds on the existing research programs Gower has in northern Manitoba and would not be possible without in-kind services and financial support from Manitoba Hydro and University of Wisconsin.« less

Water vapor weathering of Taurus-Littrow orange soil - A pore-structure analysis

NASA Technical Reports Server (NTRS)

Cadenhead, D. A.; Mikhail, R. S.

1975-01-01

A pore-volume analysis was performed on water vapor adsorption data previously obtained on a fresh sample of Taurus-Littrow orange soil, and the analysis was repeated on the same sample after its exposure to moist air for a period of approximately six months. The results indicate that exposure of an outgassed sample to high relative pressures of water vapor can result in the formation of substantial micropore structure, the precise amount being dependent on the sample pretreatment, particularly the outgassing temperature. Micropore formation is explained in terms of water penetration into surface defects. In contrast, long-term exposure to moist air at low relative pressures appears to reverse the process with the elimination of micropores and enlargement of mesopores possibly through surface diffusion of metastable adsorbent material. The results are considered with reference to the storage of lunar samples.

Microwave Sinterator Freeform Additive Construction System (MS-FACS)

NASA Technical Reports Server (NTRS)

Howe, Alan S.; Wilcox, Brian H.; Barmatz, Martin B.; Mercury, Michael B.; Siebert, Michael A.; Rieber, Richard R.

2013-01-01

The harmful properties of lunar dust, such as small size, glass composition, abnormal surface area, and coatings of imbedded nanophase iron, lead to a unique coupling of the dust with microwave radiation. This coupling can be exploited for rapid sintering of lunar soil for use as a construction material that can be formed to take on an infinite number of shapes and sizes. This work describes a system concept for building structures on the lunar surface using lunar regolith (soil). This system uses the ATHLETE (All-Terrain Hex- Limbed Extra-Terrestrial Explorer) mobility system as a positioning system with a microwave print head (similar to that of a smaller-scale 3D printer). A processing system delivers the lunar regolith to the microwave print head, where the microwave print head/chamber lays down a layer of melted regolith. An arm on the ATHLETE system positions the layer depending on the desired structure.

Quantification of the proliferation of arbuscular mycorrhizal fungi in soil

NASA Astrophysics Data System (ADS)

Zhang, Ning; Lilje, Osu; McGee, Peter

2013-04-01

Good soil structure is important for sustaining agricultural production and preserving functions of the soil ecosystem. Soil aggregation is a critically important component of soil structure. Stable aggregates enable water infiltration, gas exchange for biological activities of plant roots and microorganisms, living space and surfaces for soil microbes, and contribute to stabilization of organic matter and storage of organic carbon (OC) in soil. Soil aggregation involves fine roots, organic matter and hyphae of arbuscular mycorrhizal (AM) fungi. Hyphal proliferation is essential for soil aggregation and sequestration of OC in soil. We do not yet have a mechanism to directly quantify the density of hyphae in soil. Organic materials and available phosphorus are two of the major factors that influence fungi in soil. Organic materials are a source of energy for saprotrophic microbes. Fungal hyphae increase in the presence of organic matter. Phosphorus is an important element usually found in ecosystems. The low availability of phosphorus limits the biological activity of microbes. AM fungi benefit plants by delivering phosphorus to the root system. However, the density and the length of hyphae of AM fungi do not appear to be influenced by available phosphorus. A number of indirect methods have been used to visualize distribution of fungi in soil. Reliable analyses of soil are limited because of soil characteristics. Soils are fragile, and fragility limits opportunity for non-destructive analysis. The soil ecosystem is complex. Soil particles are dense and the density obscures the visualization of fungal hyphae. Fungal hyphae are relatively fine and information at the small scale (<250µm) is key to understanding how fungi respond to environmental stimuli. This experiment tested whether organic carbon (starch), phosphorus (K2HPO4) and their mixture influences proliferation of hyphae of AM fungi. Hyphae were quantified in an artificial soil matrix using micro-computer aided tomography. Micro-computer aided tomography provides three dimensional images of hyphal ramification through electron lucent materials and enables the visualization and quantification of hyphae. Starch and the mixture of starch plus K2HPO4, stimulated hyphal proliferation, while K2HPO4 alone did not change the density of hyphae. The images also indicate that fungal hyphae attached to the surfaces of the particles rather than grow through the spaces between them. The capacity to quantify hyphae in three-dimensional space allows a wide range of questions to now be addressed. Apart from studying mechanisms of carbon turnover, more complex processes may now be considered. Soil is commonly thought of as a black box. That black box is now a shade of grey.

Contribution to the study of pollution of soil and water in Oued El Maleh area (Mohammedia, Morocco)

NASA Astrophysics Data System (ADS)

El hajjaji, Souad; Dahchour, Abdelmalek; Belhsaien, Kamal; Zouahri, Abdelmjid; Moussadek, Rachid; Douaik, Ahmed

2016-04-01

In Morocco, diffuse ground and surface water pollution in irrigated areas has caused an increase in the risk of water and soil quality deterioration. This has generated a health and environmental risks. The present study was carried out in the Oued El Maleh region located 65 Km to the south of Rabat on the Moroccan Atlantic coast. It covers a surface area of 310 km2 where agriculture constitutes the main activity of the population. This region is considered as a very important agricultural area, known nationally for its high potential for market gardening. This intensification has been accompanied by an excessive use of agrochemical inputs and poor control of irrigation and drainage. Consequently, salinization phenomena and deterioration of soil structure as well as water are about to create an alarming situation. In order to assess the state of pollution of waters and soil in the region, our study focuses on the determination of physicochemical parameters for the quality of water and soil. The obtained results from sampled wells and surface water show relatively higher values of nitrate and conductivity exceeding Moroccan national standards and revealing net degradation of water quality; therefore the water can be considered not suitable for human consumption and can induce a degradation of soil. The results of the studied soil show that the pH of these soils is weakly to moderately basic; they are usually non-saline with organic matter content moderately filled. Moreover, very high concentrations of nutrients (potassium, phosphorus and nitrogen) were recorded, highlighting poor management fertilizing vegetable crops in the region of Oued El Maleh.

Modification of biochar for functionality improvement in soils

NASA Astrophysics Data System (ADS)

Zwart, Kor; Kuikman, Peter; Ross, Anrew; Takaya, Chibi; Singh, Surjit; Kocaturk, Pelin; Visser, Rian

2014-05-01

Application of biochar to soils is generally considered and practiced in order to improve specific soil functions such as CEC, moisture and nutrient retention and providing additional habitat for micro-organisms. Improvement of these soil functions should lead to a higher crop yield. This would be added value to the long term sequestration of carbon in soils and contribution to renewable energy from producing and using biochar. The concept of using biochar for soil amendment is predicated on biochar behaving in a similar manner as soil organic matter (SOM) does. However, if one critically compares the properties of biochar with the properties of SOM, it is evident that biochar is rather different from SOM [Zwart, 2013 ;Zwart & Kuikman, 2013]. We have has produced a range of biochar from different feedstock using pyrolysis, gasification and hydrothermal carbonisation resulting in chars with significantly different properties. The project also investigates and tested several possibilities for improving the functionality of biochar in soils by either(i) selection of feedstock, (ii), selection of processing conditions and (iii) chemical and physical modification of biochar during and after the production process. Post modification includes the chemical treatment of biochars with either H2O2, KOH, H2SO4 and transitional metals such as Fe and investigates their effect on surface functionality, porosity, surface area, CEC and phosphate sorption. The influence of the addition of chemical modifiers and oxidants during pyrolysis and gasification has also been investigated and their effect on surface functionality determined using similar techniques. The influence of the original biomass structure on the morphology of the resultant biochars has been investigated using scanning electron microscopy.

Spatial distribution of heavy metals in the surface soil of source-control stormwater infiltration devices - Inter-site comparison.

PubMed

Tedoldi, Damien; Chebbo, Ghassan; Pierlot, Daniel; Branchu, Philippe; Kovacs, Yves; Gromaire, Marie-Christine

2017-02-01

Stormwater runoff infiltration brings about some concerns regarding its potential impact on both soil and groundwater quality; besides, the fate of contaminants in source-control devices somewhat suffers from a lack of documentation. The present study was dedicated to assessing the spatial distribution of three heavy metals (copper, lead, zinc) in the surface soil of ten small-scale infiltration facilities, along with several physical parameters (soil moisture, volatile matter, variable thickness of the upper horizon). High-resolution samplings and in-situ measurements were undertaken, followed by X-ray fluorescence analyses and spatial interpolation. Highest metal accumulation was found in a relatively narrow area near the water inflow zone, from which concentrations markedly decreased with increasing distance. Maximum enrichment ratios amounted to >20 in the most contaminated sites. Heavy metal patterns give a time-integrated vision of the non-uniform infiltration fluxes, sedimentation processes and surface flow pathways within the devices. This element indicates that the lateral extent of contamination is mainly controlled by hydraulics. The evidenced spatial structure of soil concentrations restricts the area where remediation measures would be necessary in these systems, and suggests possible optimization of their hydraulic functioning towards an easier maintenance. Heterogeneous upper boundary conditions should be taken into account when studying the fate of micropollutants in infiltration facilities with either mathematical modeling or soil coring field surveys. Copyright © 2016 Elsevier B.V. All rights reserved.

Soil fertility in deserts: a review on the influence of biological soil crusts and the effect of soil surface disturbance on nutrient inputs and losses

USGS Publications Warehouse

Reynolds, R.; Phillips, S.; Duniway, M.; Belnap, J.

2003-01-01

Sources of desert soil fertility include parent material weathering, aeolian deposition, and on-site C and N biotic fixation. While parent materials provide many soil nutrients, aeolian deposition can provide up to 75% of plant-essential nutrients including N, P, K, Mg, Na, Mn, Cu, and Fe. Soil surface biota are often sticky, and help retain wind-deposited nutrients, as well as providing much of the N inputs. Carbon inputs are from both plants and soil surface biota. Most desert soils are protected by cyanobacterial-lichen-moss soil crusts, chemical crusts and/or desert pavement. Experimental disturbances applied in US deserts show disruption of soil surfaces result in decreased N and C inputs from soil biota by up to 100%. The ability to glue aeolian deposits in place is compromised, and underlying soils are exposed to erosion. The ability to withstand wind increases with biological and physical soil crust development. While most undisturbed sites show little sediment production, disturbance by vehicles or livestock produce up to 36 times more sediment production, with soil movement initiated at wind velocities well below commonly-occurring wind speeds. Soil fines and flora are often concentrated in the top 3 mm of the soil surface. Winds across disturbed areas can quickly remove this material from the soil surface, thereby potentially removing much of current and future soil fertility. Thus, disturbances of desert soil surfaces can both reduce fertility inputs and accelerate fertility losses.

Using Remote Sensing Platforms to Estimate Near-Surface Soil Properties

NASA Technical Reports Server (NTRS)

Sullivan, D. G.; Shaw, J. N.; Rickman, D.; Mask, P. L.; Wersinger, J. M.; Luvall, J.

2003-01-01

Evaluation of near-surface soil properties via remote sensing (RS) could facilitate soil survey mapping, erosion prediction, fertilization regimes, and allocation of agrochemicals. The objective of this study was to evaluate the relationship between soil spectral signature and near surface soil properties in conventionally managed row crop systems. High resolution RS data were acquired over bare fields in the Coastal Plain, Appalachian Plateau, and Ridge and Valley provinces of Alabama using the Airborne Terrestrial Applications Sensor (ATLAS) multispectral scanner. Soils ranged from sandy Kandiudults to fine textured Rhodudults. Surface soil samples (0-1 cm) were collected from 163 sampling points for soil water content, soil organic carbon (SOC), particle size distribution (PSD), and citrate dithionite extractable iron (Fed) content. Surface roughness, soil water content, and crusting were also measured at sampling. Results showed RS data acquired from lands with less than 4 % surface soil water content best approximated near-surface soil properties at the Coastal Plain site where loamy sand textured surfaces were predominant. Utilizing a combination of band ratios in stepwise regression, Fed (r2 = 0.61), SOC (r2 = 0.36), sand (r2 = 0.52), and clay (r2 = 0.76) were related to RS data at the Coastal Plain site. In contrast, the more clayey Ridge and Valley soils had r-squares of 0.50, 0.36, 0.17, and 0.57. for Fed, SOC, sand and clay, respectively. Use of estimated eEmissivity did not generally improve estimates of near-surface soil attributes.

Microbial Life in Soil - Linking Biophysical Models with Observations

NASA Astrophysics Data System (ADS)

Or, Dani; Tecon, Robin; Ebrahimi, Ali; Kleyer, Hannah; Ilie, Olga; Wang, Gang

2015-04-01

Microbial life in soil occurs within fragmented aquatic habitats formed in complex pore spaces where motility is restricted to short hydration windows (e.g., following rainfall). The limited range of self-dispersion and physical confinement promote spatial association among trophically interdepended microbial species. Competition and preferences for different nutrient resources and byproducts and their diffusion require high level of spatial organization to sustain the functioning of multispecies communities. We report mechanistic modeling studies of competing multispecies microbial communities grown on hydrated surfaces and within artificial soil aggregates (represented by 3-D pore network). Results show how trophic dependencies and cell-level interactions within patchy diffusion fields promote spatial self-organization of motile microbial cells. The spontaneously forming patterns of segregated, yet coexisting species were robust to spatial heterogeneities and to temporal perturbations (hydration dynamics), and respond primarily to the type of trophic dependencies. Such spatially self-organized consortia may reflect ecological templates that optimize substrate utilization and could form the basic architecture for more permanent surface-attached microbial colonies. Hydration dynamics affect structure and spatial arrangement of aerobic and anaerobic microbial communities and their biogeochemical functions. Experiments with well-characterized artificial soil microbial assemblies grown on porous surfaces provide access to community dynamics during wetting and drying cycles detected through genetic fingerprinting. Experiments for visual observations of spatial associations of tagged bacterial species with known trophic dependencies on model porous surfaces are underway. Biophysical modeling provide a means for predicting hydration-mediated critical separation distances for activation of spatial self-organization. The study provides new modeling and observational tools that enable new mechanistic insights into how differences in substrate affinities among microbial species and soil micro-hydrological conditions may give rise to a remarkable spatial and functional order in an extremely heterogeneous soil microbial world

Microbial Life in Soil - Linking Biophysical Models with Observations

NASA Astrophysics Data System (ADS)

Or, D.; Tecon, R.; Ebrahimi, A.; Kleyer, H.; Ilie, O.; Wang, G.

2014-12-01

Microbial life in soil occurs within fragmented aquatic habitats in complex pore spaces where motility is restricted to short hydration windows (e.g., following rainfall). The limited range of self-dispersion and physical confinement promote spatial association among trophically interdepended microbial species. Competition and preferences for different nutrient resources and byproducts and their diffusion require high level of spatial organization to sustain the functioning of multispecies communities. We report mechanistic modeling studies of competing multispecies microbial communities grown on hydrated surfaces and within artificial soil aggregates (represented by 3-D pore network). Results show how trophic dependencies and cell-level interactions within patchy diffusion fields promote spatial self-organization of motile microbial cells. The spontaneously forming patterns of segregated, yet coexisting species were robust to spatial heterogeneities and to temporal perturbations (hydration dynamics), and respond primarily to the type of trophic dependencies. Such spatially self-organized consortia may reflect ecological templates that optimize substrate utilization and could form the basic architecture for more permanent surface-attached microbial colonies. Hydration dynamics affect structure and spatial arrangement of aerobic and anaerobic microbial communities and their biogeochemical functions. Experiments with well-characterized artificial soil microbial assemblies grown on porous surfaces provide access to community dynamics during wetting and drying cycles detected through genetic fingerprinting. Experiments for visual observations of spatial associations of tagged bacterial species with known trophic dependencies on model porous surfaces are underway. Biophysical modeling provide a means for predicting hydration-mediated critical separation distances for activation of spatial self-organization. The study provides new modeling and observational tools that enable new mechanistic insights into how differences in substrate affinities among microbial species and soil micro-hydrological conditions may give rise to a remarkable spatial and functional order in an extremely heterogeneous soil microbial world.

Leaching potential of chlorpyrifos in an Andisol and Entisol: adsorption-desorption and degradation studies

NASA Astrophysics Data System (ADS)

Mosquera-Vivas, Carmen; Walther Hansen, Eddy; Garcia-Santos, Glenda; Obregón-Neira, Nelson; Celis-Ossa, Raul Ernesto; González-Murillo, Carlos Alberto; Juraske, Ronnie; Hellweg, Stefanie; Guerrero-Dallos, Jairo Arturo

2017-04-01

Ecological status of tropical soils like high OC content and microbial activity plays a key role to reduce the leaching of insecticide chlorpyrifos through the soil profile and therefore into groundwater. We found that chlorpyrifos has "transitional" leaching potential (GUS values varied between 1.8 and 2.5) throughout the soil depth, which differs from the "nonleacher" classification for temperate soils as based on surface level t1/2 and Koc values from international databases. These findings provide strong evidence of the importance of estimating the transport parameters and insecticide concentrations in different soil layers, especially when the amount and type of OC content vary throughout the soil profile. We got to such conclusions after studying the soil profile structural composition of soil organic matter and the adsorption/desorption characteristics of the insecticide in two different soil profiles (Andisol and Entisol) under agriculture production using Fourier transform infrared spectroscopy, nuclear magnetic resonance, and batch analysis methods.

A semiempirical model for interpreting microwave emission from semiarid land surfaces as seen from space

NASA Technical Reports Server (NTRS)

Kerr, Yann H.; Njoku, Eni G.

1990-01-01

A radiative-transfer model for simulating microwave brightness temperatures over land surfaces is described. The model takes into account sensor viewing conditions (spacecraft altitude, viewing angle, frequency, and polarization) and atmospheric parameters over a soil surface characterized by its moisture, roughness, and temperature and covered with a layer of vegetation characterized by its temperature, water content, single scattering albedo, structure, and percent coverage. In order to reduce the influence of atmospheric and surface temperature effects, the brightness temperatures are expressed as polarization ratios that depend primarily on the soil moisture and roughness, canopy water content, and percentage of cover. The sensitivity of the polarization ratio to these parameters is investigated. Simulation of the temporal evolution of the microwave signal over semiarid areas in the African Sahel is presented and compared to actual satellite data from the SMMR instrument on Nimbus-7.

Soils are sensitive reactors - do we need a paradigm change towards a more sustainable soil use?

NASA Astrophysics Data System (ADS)

Horn, Rainer; Holthusen, Dörthe

2015-04-01

The aim of the lecture is to clarify the effect of soil management and the consequences of physical degradation on processes like soil aggregation and changes in the accessibility and functionality of structured soils. If due to soil management strategies the internal soil strength will be exceeded by external stresses applied not only the available pore space is reduced while the solid mass is increased but especially the pore continuity and the accessibility of exchange places for nutrients or heavy metals are altered. In addition, the root distribution in soils becomes not only reduced but also unevenly distributed which again hinders the possibility to evenly uptake plant available water and nutrient out of the pores. The applied stresses also create an anisotropic arrangement of the pores and their functions and also result in a more pronounced lateral mass transport by surface runoff including soil erosion by water and wind. Thus, also the water balance on all scales (from the pedon to the catchment) shows an increased water loss by evaporation and surface water while the groundwater recharge and the transpiration rates are reduced. If we analyze the scale dependency of nutrient adsorption and desorption phenomena it has to be stated, that the accessibility of exchange places within soil aggregates are the better the more structured and the more rigid these aggregates are, while with increasing mechanical stress applied aggregates are deformed and as a consequences they become less porous with a severe differentiation between the outer and the inner part of the aggregate volume. On the bulk soil scale, we can analyze the platy structure as a visible hint for anthropogenic soil degradation which affects amongst others also the ion exchange processes. Furthermore an uneven aeration within such degraded soils results in a very pronounced anoxia on all scales (from the aggregate to the hectare scale) which can be quantified not only by corresponding measurements of the spatial distribution of redox potential values. In recent studies under "normal" wheeling conditions in arable fields and also in harvested forest sites it was proofed that Eh values close to 0 mV or even a methane emission have to be expected (with consequences for the global warming). Finally anoxic conditions also affect the redox induced mobilization of Fe and Mn which even results in a more rapid soil development with consequences also for yield and further soil functions. Consequently a shift to a more sustainable landuse or soil management strategy is urgently requested in order to prevent a further soil degradation. The scenario of peak soil must and can be prevented by a more site specific soil management. In the lecture, these effects will be discussed as well as a soil protection guide line (based on the German soil protection law) will be presented in order to prevent further irreversible soil degradation phenomena. Keywords: mechanical strength, mechanical stress and strain effects soil degradation, pore functions, ad-/desorption processes, redox potential, anoxia;, global change

Undercut Rocks at the MER Gusev Landing Site

NASA Technical Reports Server (NTRS)

Landis, Geoffrey A.

2004-01-01

On January 3 2004, the NASA Spirit rover landed on the plains inside the Gusev Crater in the southern hemisphere of Mars, and has made observations of the landing site and nearby region in visual and infrared wavelengths, as well as making in-situ measurements of rocks and soil. A number of rocks at the Gusev site are perched, with a significant undercut above the surface; additional rocks show a feature of being eroded or etched at a height of one to three centimeters immediately above the soil line. Some rocks also show terracing, and others show a two-tone pattern of albedo, with a distinct dividing line between a lighter area near the surface and a darker color above the surface. In a small number of cases, the dividing line is correlated with a visible horizontal groove in the rock, most likely indicating an earlier location of burial of the rock. A number of explanations for this undercutting are possible. Perched rocks can be placed on the surface by deflation of the soil from underneath the rock. The surface etching may be abrasion due to reptation. Reptation, or surface creep, occurs as sand moves without leaving the surface, as small (100-200 micron particles) moved by saltation set larger particles in motion. These large particles are effective at abrading the rocks at the surface level. The structure of "ripple" features at the site is evidence to support reptation at the Gusev site. An alternate explanation is etching at the surface by chemically active grit.

Stomatal Conductance, Plant Hydraulics, and Multilayer Canopies: A New Paradigm for Earth System Models or Unnecessary Uncertainty

NASA Astrophysics Data System (ADS)

Bonan, G. B.

2016-12-01

Soil moisture stress is a key regulator of canopy transpiration, the surface energy budget, and land-atmosphere coupling. Many land surface models used in Earth system models have an ad-hoc parameterization of soil moisture stress that decreases stomatal conductance with soil drying. Parameterization of soil moisture stress from more fundamental principles of plant hydrodynamics is a key research frontier for land surface models. While the biophysical and physiological foundations of such parameterizations are well-known, their best implementation in land surface models is less clear. Land surface models utilize a big-leaf canopy parameterization (or two big-leaves to represent the sunlit and shaded canopy) without vertical gradients in the canopy. However, there are strong biometeorological and physiological gradients in plant canopies. Are these gradients necessary to resolve? Here, I describe a vertically-resolved, multilayer canopy model that calculates leaf temperature and energy fluxes, photosynthesis, stomatal conductance, and leaf water potential at each level in the canopy. In this model, midday leaf water stress manifests in the upper canopy layers, which receive high amounts of solar radiation, have high leaf nitrogen and photosynthetic capacity, and have high stomatal conductance and transpiration rates (in the absence of leaf water stress). Lower levels in the canopy become water stressed in response to longer-term soil moisture drying. I examine the role of vertical gradients in the canopy microclimate (solar radiation, air temperature, vapor pressure, wind speed), structure (leaf area density), and physiology (leaf nitrogen, photosynthetic capacity, stomatal conductance) in determining above canopy fluxes and gradients of transpiration and leaf water potential within the canopy.

Using simple structures for flow dispersion in wet meadow restoration

Treesearch

Bill Zeedyk; Benjamin Romero; Steven K. Albert

1996-01-01

Historically, wet meadow recovery projects have relied on heavy earth moving equipment to harden nick points and install gully plugs or terraces to trap and detain sediments. We experimented with a variety of simple hand-built structures fashioned of logs, rocks, geotextile fabrics and/or sandbags designed to disperse runoff, rewet surface and subsurface soils and...

Detecting surface runoff location in a small catchment using distributed and simple observation method

NASA Astrophysics Data System (ADS)

Dehotin, Judicaël; Breil, Pascal; Braud, Isabelle; de Lavenne, Alban; Lagouy, Mickaël; Sarrazin, Benoît

2015-06-01

Surface runoff is one of the hydrological processes involved in floods, pollution transfer, soil erosion and mudslide. Many models allow the simulation and the mapping of surface runoff and erosion hazards. Field observations of this hydrological process are not common although they are crucial to evaluate surface runoff models and to investigate or assess different kinds of hazards linked to this process. In this study, a simple field monitoring network is implemented to assess the relevance of a surface runoff susceptibility mapping method. The network is based on spatially distributed observations (nine different locations in the catchment) of soil water content and rainfall events. These data are analyzed to determine if surface runoff occurs. Two surface runoff mechanisms are considered: surface runoff by saturation of the soil surface horizon and surface runoff by infiltration excess (also called hortonian runoff). The monitoring strategy includes continuous records of soil surface water content and rainfall with a 5 min time step. Soil infiltration capacity time series are calculated using field soil water content and in situ measurements of soil hydraulic conductivity. Comparison of soil infiltration capacity and rainfall intensity time series allows detecting the occurrence of surface runoff by infiltration-excess. Comparison of surface soil water content with saturated water content values allows detecting the occurrence of surface runoff by saturation of the soil surface horizon. Automatic records were complemented with direct field observations of surface runoff in the experimental catchment after each significant rainfall event. The presented observation method allows the identification of fast and short-lived surface runoff processes at a small spatial and temporal resolution in natural conditions. The results also highlight the relationship between surface runoff and factors usually integrated in surface runoff mapping such as topography, rainfall parameters, soil or land cover. This study opens interesting prospects for the use of spatially distributed measurement for surface runoff detection, spatially distributed hydrological models implementation and validation at a reasonable cost.

Identification and classification of structural soil conservation measures based on very high resolution stereo satellite data.

PubMed

Eckert, Sandra; Tesfay Ghebremicael, Selamawit; Hurni, Hans; Kohler, Thomas

2017-05-15

Land degradation affects large areas of land around the globe, with grave consequences for those living off the land. Major efforts are being made to implement soil and water conservation measures that counteract soil erosion and help secure vital ecosystem services. However, where and to what extent such measures have been implemented is often not well documented. Knowledge about this could help to identify areas where soil and water conservation measures are successfully supporting sustainable land management, as well as areas requiring urgent rehabilitation of conservation structures such as terraces and bunds. This study explores the potential of the latest satellite-based remote sensing technology for use in assessing and monitoring the extent of existing soil and water conservation structures. We used a set of very high resolution stereo Geoeye-1 satellite data, from which we derived a detailed digital surface model as well as a set of other spectral, terrain, texture, and filtered information layers. We developed and applied an object-based classification approach, working on two segmentation levels. On the coarser level, the aim was to delimit certain landscape zones. Information about these landscape zones is useful in distinguishing different types of soil and water conservation structures, as each zone contains certain specific types of structures. On the finer level, the goal was to extract and identify different types of linear soil and water conservation structures. The classification rules were based mainly on spectral, textural, shape, and topographic properties, and included object relationships. This approach enabled us to identify and separate from other classes the majority (78.5%) of terraces and bunds, as well as most hillside terraces (81.25%). Omission and commission errors are similar to those obtained by the few existing studies focusing on the same research objective but using different types of remotely sensed data. Based on our results, we estimate that the construction of the conservation structures in our study area in Eritrea required over 300,000 person-days of work, which underlines the huge efforts involved in soil and water conservation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Biological soil crusts in deserts: A short review of their role in soil fertility, stabilization, and water relations

USGS Publications Warehouse

Belnap, Jayne

2003-01-01

Cyanobacteria and cyanolichens dominate most desert soil surfaces as the major component of biological soil crusts (BSC). BSCs contribute to soil fertility in many ways. BSC can increase weathering of parent materials by up to 100 times. Soil surface biota are often sticky, and help retain dust falling on the soil surface; this dust provides many plant-essential nutrients including N, P, K, Mg, Na, Mn, Cu, and Fe. BSCs also provide roughened soil surfaces that slow water runoff and aid in retaining seeds and organic matter. They provide inputs of newly-fixed carbon and nitrogen to soils. They are essential in stabilizing soil surfaces by linking soil particles together with filamentous sheaths, enabling soils to resist both water and wind erosion. These same sheaths are important in keeping soil nutrients from becoming bound into plant-unavailable forms. Experimental disturbances applied in US deserts show soil surface impacts decrease N and C inputs from soil biota by up to 100%. The ability to hold aeolian deposits in place is compromised, and underlying soils are exposed to erosion. While most undisturbed sites show little sediment production, disturbance by vehicles or livestock produces up to 36 times more sediment production, with soil movement initiated at wind velocities well below commonly-occurring wind speeds. Winds across disturbed areas can quickly remove this material from the soil surface, thereby potentially removing much of current and future soil fertility. Thus, reduction in the cover of cyanophytes in desert soils can both reduce fertility inputs and accelerate fertility losses.

Soil erodibility in Europe: a high-resolution dataset based on LUCAS.

PubMed

Panagos, Panos; Meusburger, Katrin; Ballabio, Cristiano; Borrelli, Pasqualle; Alewell, Christine

2014-05-01

The greatest obstacle to soil erosion modelling at larger spatial scales is the lack of data on soil characteristics. One key parameter for modelling soil erosion is the soil erodibility, expressed as the K-factor in the widely used soil erosion model, the Universal Soil Loss Equation (USLE) and its revised version (RUSLE). The K-factor, which expresses the susceptibility of a soil to erode, is related to soil properties such as organic matter content, soil texture, soil structure and permeability. With the Land Use/Cover Area frame Survey (LUCAS) soil survey in 2009 a pan-European soil dataset is available for the first time, consisting of around 20,000 points across 25 Member States of the European Union. The aim of this study is the generation of a harmonised high-resolution soil erodibility map (with a grid cell size of 500 m) for the 25 EU Member States. Soil erodibility was calculated for the LUCAS survey points using the nomograph of Wischmeier and Smith (1978). A Cubist regression model was applied to correlate spatial data such as latitude, longitude, remotely sensed and terrain features in order to develop a high-resolution soil erodibility map. The mean K-factor for Europe was estimated at 0.032 thahha(-1)MJ(-1)mm(-1) with a standard deviation of 0.009 thahha(-1)MJ(-1)mm(-1). The yielded soil erodibility dataset compared well with the published local and regional soil erodibility data. However, the incorporation of the protective effect of surface stone cover, which is usually not considered for the soil erodibility calculations, resulted in an average 15% decrease of the K-factor. The exclusion of this effect in K-factor calculations is likely to result in an overestimation of soil erosion, particularly for the Mediterranean countries, where highest percentages of surface stone cover were observed. Copyright © 2014. Published by Elsevier B.V.

A Simplified Land Model (SLM) for use in cloud-resolving models: Formulation and evaluation

NASA Astrophysics Data System (ADS)

Lee, Jungmin M.; Khairoutdinov, Marat

2015-09-01

A Simplified Land Model (SLM) that uses a minimalist set of parameters with a single-layer vegetation and multilevel soil structure has been developed distinguishing canopy and undercanopy energy budgets. The primary motivation has been to design a land model for use in the System for Atmospheric Modeling (SAM) cloud-resolving model to study land-atmosphere interactions with a sufficient level of realism. SLM uses simplified expressions for the transport of heat, moisture, momentum, and radiation in soil-vegetation system. The SLM performance has been evaluated over several land surface types using summertime tower observations of micrometeorological and biophysical data from three AmeriFlux sites, which include grassland, cropland, and deciduous-broadleaf forest. In general, the SLM captures the observed diurnal cycle of surface energy budget and soil temperature reasonably well, although reproducing the evolution of soil moisture, especially after rain events, has been challenging. The SLM coupled to SAM has been applied to the case of summertime shallow cumulus convection over land based on the Atmospheric Radiation Measurements (ARM) Southern Great Plain (SGP) observations. The simulated surface latent and sensible heat fluxes as well as the evolution of thermodynamic profiles in convective boundary layer agree well with the estimates based on the observations. Sensitivity of atmospheric boundary layer development to the soil moisture and different land cover types has been also examined.

Use of treated wastewater in agriculture: effects on soil environment

NASA Astrophysics Data System (ADS)

Levy, Guy J.; Lado, Marcos

2014-05-01

Disposal of treated sewage, both from industrial and domestic origin (herein referred to as treated wastewater [TWW]), is often considered as an environmental hazard. However, in areas afflicted by water scarcity, especially in semi-arid and arid regions, where the future of irrigated agriculture (which produces approximately one third of crop yield and half the return from global crop production) is threatened by existing or expected shortage of fresh water, the use of TWW offers a highly effective and sustainable strategy to exploit a water resource. However, application of TWW to the soil is not free of risks both to organisms (e.g., crops, microbiota) and to the soil. Potential risks may include reduction in biological activity (including crop yield) due to elevated salinity and specific ion toxicity, migration of pollutants towards surface- and ground-water, and deterioration of soil structure. In recent years, new evidence about the possible negative impact of long-term irrigation with TWW on soil structure and physical and chemo-physical properties has emerged, thus putting the sustainability of irrigation with TWW in question. In this presentation, some aspects of the effects of long-term irrigation with TWW on soil properties are shown.

Are preferential flow paths perpetuated by microbial activity in the soil matrix? A review

NASA Astrophysics Data System (ADS)

Morales, Verónica L.; Parlange, J.-Yves; Steenhuis, Tammo S.

2010-10-01

SummaryRecently, the interactions between soil structure and microbes have been associated with water transport, retention and preferential or column flow development. Of particular significance is the potential impact of microbial extracellular polymeric substances (EPS) on soil porosity (i.e., hydraulic conductivity reduction or bioclogging) and of exudates from biota, including bacteria, fungi, roots and earthworms on the degree of soil water repellency. These structural and surface property changes create points of wetting instability, which under certain infiltrating conditions can often result in the formation of persistent preferential flow paths. Moreover, distinct differences in physical and chemical properties between regions of water flow (preferential flow paths) and no-flow (soil matrix) provide a unique set of environmental living conditions for adaptable microorganisms to exist. In this review, special consideration is given to: (1) the functional significance of microbial activity in the host porous medium in terms of feedback mechanisms instigated by irregular water availability and (2) the related physical and chemical conditions that force the organization and formation of unique microbial habitats in unsaturated soils that prompt and potentially perpetuate the formation of preferential flow paths in the vadose zone.

Grass mulching effect on infiltration, surface runoff and soil loss of three agricultural soils in Nigeria.

PubMed

Adekalu, K O; Olorunfemi, I A; Osunbitan, J A

2007-03-01

Mulching the soil surface with a layer of plant residue is an effective method of conserving water and soil because it reduces surface runoff, increases infiltration of water into the soil and retard soil erosion. The effectiveness of using elephant grass (Pennisetum purpureum) as mulching material was evaluated in the laboratory using a rainfall simulator set at rainfall intensities typical of the tropics. Six soil samples, two from each of the three major soil series representing the main agricultural soils in South Western Nigeria were collected, placed on three different slopes, and mulched with different rates of the grass. The surface runoff, soil loss, and apparent cumulative infiltration were then measured under each condition. The results with elephant grass compared favorably with results from previous experiments using rice straw. Runoff and soil loss decreased with the amount of mulch used and increased with slope. Surface runoff, infiltration and soil loss had high correlations (R = 0.90, 0.89, and 0.86, respectively) with slope and mulch cover using surface response analysis. The mean surface runoff was correlated negatively with sand content, while mean soil loss was correlated positively with colloidal content (clay and organic matter) of the soil. Infiltration was increased and soil loss was reduced greatly with the highest cover. Mulching the soils with elephant grass residue may benefit late cropping (second cropping) by increasing stored soil water for use during dry weather and help to reduce erosion on sloping land.

Soil Aggregates and Associated Organic Matter under Conventional Tillage, No-Tillage, and Forest Succession after Three Decades

PubMed Central

Devine, Scott; Markewitz, Daniel; Hendrix, Paul; Coleman, David

2014-01-01

Impacts of land use on soil organic C (SOC) are of interest relative to SOC sequestration and soil sustainability. The role of aggregate stability in SOC storage under contrasting land uses has been of particular interest relative to conventional tillage (CT) and no-till (NT) agriculture. This study compares soil structure and SOC fractions at the 30-yr-old Horseshoe Bend Agroecosystem Experiment (HSB). This research is unique in comparing NT and CT with adjacent land concurrently undergoing forest succession (FS) and in sampling to depths (15–28 cm) previously not studied at HSB. A soil moving experiment (SME) was also undertaken to monitor 1-yr changes in SOC and aggregation. After 30 years, enhanced aggregate stability under NT compared to CT was limited to a depth of 5 cm, while enhanced aggregate stability under FS compared to CT occurred to a depth of 28 cm and FS exceeded NT from 5–28 cm. Increases in SOC concentrations generally followed the increases in stability, except that no differences in SOC concentration were observed from 15–28 cm despite greater aggregate stability. Land use differences in SOC were explained equally by differences in particulate organic carbon (POC) and in silt-clay associated fine C. Enhanced structural stability of the SME soil was observed under FS and was linked to an increase of 1 Mg SOC ha−1 in 0–5 cm, of which 90% could be attributed to a POC increase. The crushing of macroaggregates in the SME soil also induced a 10% reduction in SOC over 1 yr that occurred under all three land uses from 5–15 cm. The majority of this loss was in the fine C fraction. NT and FS ecosystems had greater aggregation and carbon storage at the soil surface but only FS increased aggregation below the surface, although in the absence of increased carbon storage. PMID:24465460

Rainfall simulation and Structure-from-Motion photogrammetry for the analysis of soil water erosion in Mediterranean vineyards.

PubMed

Prosdocimi, Massimo; Burguet, Maria; Di Prima, Simone; Sofia, Giulia; Terol, Enric; Rodrigo Comino, Jesús; Cerdà, Artemi; Tarolli, Paolo

2017-01-01

Soil water erosion is a serious problem, especially in agricultural lands. Among these, vineyards deserve attention, because they constitute for the Mediterranean areas a type of land use affected by high soil losses. A significant problem related to the study of soil water erosion in these areas consists in the lack of a standardized procedure of collecting data and reporting results, mainly due to a variability among the measurement methods applied. Given this issue and the seriousness of soil water erosion in Mediterranean vineyards, this works aims to quantify the soil losses caused by simulated rainstorms, and compare them with each other depending on two different methodologies: (i) rainfall simulation and (ii) surface elevation change-based, relying on high-resolution Digital Elevation Models (DEMs) derived from a photogrammetric technique (Structure-from-Motion or SfM). The experiments were carried out in a typical Mediterranean vineyard, located in eastern Spain, at very fine scales. SfM data were obtained from one reflex camera and a smartphone built-in camera. An index of sediment connectivity was also applied to evaluate the potential effect of connectivity within the plots. DEMs derived from the smartphone and the reflex camera were comparable with each other in terms of accuracy and capability of estimating soil loss. Furthermore, soil loss estimated with the surface elevation change-based method resulted to be of the same order of magnitude of that one obtained with rainfall simulation, as long as the sediment connectivity within the plot was considered. High-resolution topography derived from SfM revealed to be essential in the sediment connectivity analysis and, therefore, in the estimation of eroded materials, when comparing them to those derived from the rainfall simulation methodology. The fact that smartphones built-in cameras could produce as much satisfying results as those derived from reflex cameras is a high value added for using SfM. Copyright © 2016 Elsevier B.V. All rights reserved.

Phosphorus leaching from loamy sand and clay loam topsoils after application of pig slurry.

PubMed

Liu, Jian; Aronsson, Helena; Bergström, Lars; Sharpley, Andrew

2012-12-01

Appropriate management of animal waste is essential for guaranteeing good water quality. A laboratory leaching study with intact soil columns was performed to investigate the risk of phosphorus (P) leaching from a clay loam and a loamy sand. The columns (0.2 m deep) were irrigated before and after application of pig slurry on the surface or after incorporation, or application of mineral P, each at a rate of 30 kg P ha(-1). The two soils had different initial P contents (i.e. the ammonium lactate-extractable P was 65 and 142 mg kg(-1) for the clay loam and loamy sand, respectively), but had similar P sorption characteristics (P sorption index 3.0) and degree of P saturation (17-21%). Concentrations of dissolved reactive P (DRP) and total P (TP) before P application were significantly higher in leachate from the loamy sand (TP 0.21 mg L(-1)) than from the clay loam (TP 0.13 mg L(-1)), but only increased significantly after P application to the clay loam. The highest concentrations were found when slurry was surface-applied (DRP 1.77 mg L(-1)), while incorporation decreased the DRP concentration by 64% in the clay loam. Thus moderate slurry application to a sandy soil with low P saturation did not pose a major risk of P leaching. However, application of P increased the risk of P leaching from the clay loam, irrespective of application method and despite low P saturation. The results show the importance of considering soil texture and structure in addition to soil chemical characteristics in risk assessments of P leaching. Structured soils such as the clay loam used in this study are high risk soils and application of P to bare soil during wet periods, e.g. in autumn or spring, should be followed by incorporation or avoided completely.

Synthesis of soil-hydraulic properties and infiltration timescales in wildfire-affected soils

USGS Publications Warehouse

Ebel, Brian A.; Moody, John A.

2017-01-01

We collected soil-hydraulic property data from the literature for wildfire-affected soils, ash, and unburned soils. These data were used to calculate metrics and timescales of hydrologic response related to infiltration and surface runoff generation. Sorptivity (S) and wetting front potential (Ψf) were significantly different (lower) in burned soils compared with unburned soils, whereas field-saturated hydraulic conductivity (Kfs) was not significantly different. The magnitude and duration of the influence of capillarity during infiltration was greatly reduced in burned soils, causing faster ponding times in response to rainfall. Ash had large values of S and Kfs but moderate values of Ψf, compared with unburned and burned soils, indicating ash has long ponding times in response to rainfall. The ratio of S2/Kfs was nearly constant (~100 mm) for unburned soils but more variable in burned soils, suggesting that unburned soils have a balance between gravity and capillarity contributions to infiltration that may depend on soil organic matter, whereas in burned soils the gravity contribution to infiltration is greater. Changes in S and Kfs in burned soils act synergistically to reduce infiltration and accelerate and amplify surface runoff generation. Synthesis of these findings identifies three key areas for future research. First, short timescales of capillary influences on infiltration indicate the need for better measurements of infiltration at times less than 1 min to accurately characterize S in burned soils. Second, using parameter values, such as Ψf, from unburned areas could produce substantial errors in hydrologic modeling when used without adjustment for wildfire effects, causing parameter compensation and resulting underestimation of Kfs. Third, more thorough measurement campaigns that capture soil-structural changes, organic matter impacts, quantitative water repellency trends, and soil-water content along with soil-hydraulic properties could drive the development of better techniques for numerically simulating infiltration in burned areas.

Rainfall simulations to study the types of groundcover on surface runoff and soil erosion in Champagne vineyards in France

NASA Astrophysics Data System (ADS)

Xavier, Morvan; Christophe, Naisse; Issa Oumarou, Malam; Jean-François, Desprats; Anne, Combaud; Olivier, Cerdan

2015-04-01

In the literature, grass cover is often considered to be one of the best methods of limiting runoff in the vineyards; But results can vary, especially when the plot area is <2 m². However, in any study to our knowledge, the way grass cover is structured in the inter-row is taken into account to explain the variability of runoff and soil loss. The objective of this study, conducted in Champagne vineyards in France, was to quantify the influence of the cultivation practices in the inter-rows of vines and determine the influence of the density of the grass cover in the wheel tracks on the surface runoff and soil erosion in experimental plots of 0.25 m2 under simulated rainfall. Three types of ground cover were studied. In the bark-and-vine-prunings plots, the runoff coefficient ranged from 1.3 to 4.0% and soil losses were <1 g/m²/h. In the bare soil plot, the highest runoff coefficient of the study was found (80.0%) and soil losses reached 7.4 g/m²/h. In the grass cover plots, the runoff coefficient and amount of eroded soil were highly variable: the runoff coefficients ranged from 0.4 to 77.0%, and soil losses were between less than 1 and 13.4 g/m²/h. Soil type, soil moisture, slope and agricultural practices did not account for the variability. In fact, the density of grass cover in the wheel tracks explained a portion of this variability. The lack of grass in the centre of the inter-row allowed for a preferential flow and created an erosion line in the wheel tracks where the soil was compacted. This study showed that grass cover in a vineyard was not necessarily sufficient to reduce surface runoff and prevent soil erosion. To be effective, the grass cover must be dense enough in the wheel tracks of agricultural machinery to avoid runoff coefficients close to those achieved with bare soil.

Characteristics of Nitrogen Balances of Large-scale Stock Farms and Reduction of Environmental Nitrogen Loads

NASA Astrophysics Data System (ADS)

Hattori, Toshihiro; Takamatsu, Rieko

We calculated nitrogen balances on farm gate and soil surface on large-scale stock farms and discussed methods for reducing environmental nitrogen loads. Four different types of public stock farms (organic beef, calf supply and daily cows) were surveyed in Aomori Prefecture. (1) Farm gate and soil surface nitrogen inflows were both larger than the respective outflows on all types of farms. Farm gate nitrogen balance for beef farms were worse than that for dairy farms. (2) Soil surface nitrogen outflows and soil nitrogen retention were in proportion to soil surface nitrogen inflows. (3) Reductions in soil surface nitrogen retention were influenced by soil surface nitrogen inflows. (4) In order to reduce farm gate nitrogen retention, inflows of formula feed and chemical fertilizer need to be reduced. (5) In order to reduce soil surface nitrogen retention, inflows of fertilizer need to be reduced and nitrogen balance needs to be controlled.

Processes Affecting the Annual Surface Energy Budget at High-Latitude Terrestrial Sites

NASA Astrophysics Data System (ADS)

Persson, P. O. G.; Stone, R. S.; Grachev, A.; Matrosova, L.

2012-04-01

Instrumentation at four Study of Environmental Arctic Change (SEARCH) sites (Barrow, Eureka, Alert, and Tiksi) have been enhanced in the past 6 years, including during the 2007-2008 IPY. Data from these sites are used to investigate the annual cycle of the surface energy budget (SEB), its coupling to atmospheric processes, and for Alert, its interannual variability. The comprehensive data sets are useful for showing interactions between the atmosphere, surface, and soil at high temporal resolution throughout the annual cycle. Processes that govern the SEB variability at each site are identified, and their impacts on the SEB are quantified. For example, mesoscale modulation of the SEB caused by forcing from the local terrain (downslope wind events) and coastlines (sea and land breezes) are significant at Alert and Eureka, with these processes affecting both radiative, turbulent, and ground heat flux terms in the SEB. Sub-seasonal and interannual variations in atmospheric processes and SEB impact soil thermal structures, such as the depth and timing of the summer active layer. These analyses provide an improved understanding of the processes producing changes in surface and soil temperature, linking them through the SEB as affected by atmospheric processes.

Location of Bare Soil Surface and Soil Line on the RED-NIR Spectral Plane

NASA Astrophysics Data System (ADS)

Koroleva, P. V.; Rukhovich, D. I.; Rukhovich, A. D.; Rukhovich, D. D.; Kulyanitsa, A. L.; Trubnikov, A. V.; Kalinina, N. V.; Simakova, M. S.

2017-12-01

Soil as a separate natural body occupies certain area with its own set of spectral characteristics within the RED-NIR spectral space. This is an ellipse-shaped area, and its semi-major axis is the soil line for a satellite image. The spectral area for a bare soil surface is neighboring to the areas of black carbon, straw, vegetating plants, and missing RED-NIR values. A reliable separation of the bare soil surface within the spectral space is possible with the technology of spectral neighborhood of soil line. The accuracy of this method is 90%. The determination of the bare soil surface using vegetation indices, both relative (NDVI), and perpendicular (PVI), is incorrect; the accuracy of these methods does not exceed 65%, and for most of the survey seasons it may be lower than 50%. The flat part of the "tasseled cap" described as the soil line, is not a synonym for the area of the bare soil surface. The bare soil surface on the RED-NIR plots occupies significantly smaller areas than the area of soil line according to Kauth and Thomas.

Heterogeneity of soil surface temperature induced by xerophytic shrub in a revegetated desert ecosystem, northwestern China

NASA Astrophysics Data System (ADS)

Zhang, Ya-Feng; Wang, Xin-Ping; Pan, Yan-Xia; Hu, Rui; Zhang, Hao

2013-06-01

Variation characteristics of the soil surface temperature induced by shrub canopy greatly affects the near-surface biological and biochemical processes in desert ecosystems. However, information regarding the effects of shrub upon the heterogeneity of soil surface temperature is scarce. Here we aimed to characterize the effects of shrub ( Caragana korshinskii) canopy on the soil surface temperature heterogeneity at areas under shrub canopy and the neighbouring bare ground. Diurnal variations of soil surface temperature were measured at areas adjacent to the shrub base (ASB), beneath the midcanopy (BMC), and in the bare intershrub spaces (BIS) at the eastern, southern, western and northern aspects of shrub, respectively. Results indicated that diurnal mean soil surface temperature under the C. korshinskii canopy (ASB and BMC) was significantly lower than in the BIS, with the highest in the BIS, followed by the BMC and ASB. The diurnal maximum and diurnal variations of soil surface temperatures under canopy vary strongly with different aspects of shrub with the diurnal variation in solar altitude, which could be used as cues to detect safe sites for under-canopy biota. A significant empirical linear relationship was found between soil surface temperature and solar altitude, suggesting an empirical predicator that solar altitude can serve for soil surface temperature. Lower soil surface temperatures under the canopy than in the bare intershrub spaces imply that shrubs canopy play a role of `cool islands' in the daytime in terms of soil surface temperature during hot summer months in the desert ecosystems characterized by a mosaic of sparse vegetation and bare ground.

Physical erosion modelling of complex morphodynamics in the upper Val d'Orcia: a combination of EROSION 3D, UAV, SFM and CANUPO

NASA Astrophysics Data System (ADS)

Buchholz, Arno; Kaiser, Andreas; Neugirg, Fabian; Schindewolf, Marcus; Schmidt, Jürgen

2017-04-01

Throughout the Mediterranean Basin soil erosion is both a widely spread and a landscape shaping process. In order to increase the understanding of morphodynamics inside large Italian badland areas, so called Calanchi, the process based erosion model EROSION 3D was parameterized by artificial rainfall simulations, soil sampling and an UAV based high resolution digital elevation model. Vegetation structures were removed with the CANUPO-classifier in CloudCompare. The rainfall experiments proved to be a convenient but costly tool for deriving the model input parameters. While building up the model, different composition of the inhomogeneous soil surface was considered. A diverse behavior against erosion by water was observed. The results showed that the deposition surfaces of rotational or translational slides, besides calanco depth contour, tend to degrade. Although these deposits present a comparatively low bulk density, they reduce the infiltration due to soil surface clogging and cause less erosion resistances. The differential consideration of erosion sub-processes turns out as particularly challenging. The simulation of a reference year showed an annual soil export from the catchment of 43 t/ha, which corresponds to an average surface lowering of 3 mm. Sheet erosion represents an amount of about 5% of the total erosion of badlands. Furthermore, infiltration depth, amount of runoff, sediment concentration, and grain size composition of the deposits were calculated. This study makes a contribution to the understanding of denudation processes in Calanchi badlands. The presented process-based modeling of badlands is contributing a new aspect to erosion research.

Organic matter quantity and source affects microbial community structure and function following volcanic eruption on Kasatochi Island, Alaska.

PubMed

Zeglin, Lydia H; Wang, Bronwen; Waythomas, Christopher; Rainey, Frederick; Talbot, Sandra L

2016-01-01

In August 2008, Kasatochi volcano erupted and buried a small island in pyroclastic deposits and fine ash; since then, microbes, plants and birds have begun to re-colonize the initially sterile surface. Five years post-eruption, bacterial 16S rRNA gene and fungal internal transcribed spacer (ITS) copy numbers and extracellular enzyme activity (EEA) potentials were one to two orders of magnitude greater in pyroclastic materials with organic matter (OM) inputs relative to those without, despite minimal accumulation of OM (< 0.2%C). When normalized by OM levels, post-eruptive surfaces with OM inputs had the highest β-glucosidase, phosphatase, NAGase and cellobiohydrolase activities, and had microbial population sizes approaching those in reference soils. In contrast, the strongest factor determining bacterial community composition was the dominance of plants versus birds as OM input vectors. Although soil pH ranged from 3.9 to 7.0, and %C ranged 100×, differentiation between plant- and bird-associated microbial communities suggested that cell dispersal or nutrient availability are more likely drivers of assembly than pH or OM content. This study exemplifies the complex relationship between microbial cell dispersal, soil geochemistry, and microbial structure and function; and illustrates the potential for soil microbiota to be resilient to disturbance. © 2015 Society for Applied Microbiology and John Wiley & Sons Ltd.

[Selective enrichment of Pseudomonas spp. in the rhizoplane of different plant species].

PubMed

Marrero, Mariana A; Agaras, Betina; Wall, Luis G; Valverde, Claudio

2015-01-01

In contrast to rhizobia-legume symbiosis, the specificity for root colonization by pseudomonads seems to be less strict. However, several studies about bacterial diversity in the rhizosphere highlight the influence of plant species on the selective enrichment of certain microorganisms from the bulk soil community. In order to evaluate the effect that different crops have on the structure of pseudomonad community on the root surface, we performed plant trap experiments, using surface-disinfected maize, wheat or soybean seeds that were sown in pots containing the same pristine soil as substrate. Rhizoplane suspensions were plated on a selective medium for Pseudomonas, and pooled colonies served as DNA source to carry out PCR-RFLP community structure analysis of the pseudomonads-specific marker genes oprF and gacA. PCR-RFLP profiles were grouped by plant species, and were distinguished from those of bulk soil samples. Partial sequencing of 16S rDNA genes of some representative colonies of Pseudomonas confirmed the selective enrichment of distinctive genotypes in the rhizoplane of each plant species. These results support the idea that the root systems of agricultural crops such as soybean, maize and wheat, select differential sets of pseudomonads from the native microbial repertoire inhabiting the bulk soil. Copyright © 2014 Asociación Argentina de Microbiología. Publicado por Elsevier España, S.L.U. All rights reserved.

Soil-vegetation relationships on a banded ironstone 'island', Carajás Plateau, Brazilian Eastern Amazonia.

PubMed

Nunes, Jaquelina A; Schaefer, Carlos E G R; Ferreira Júnior, Walnir G; Neri, Andreza V; Correa, Guilherme R; Enright, Neal J

2015-01-01

Vegetation and soil properties of an iron-rich canga (laterite) island on the largest outcrop of banded-iron formation in Serra de Carajás (eastern Amazonia, Brazil) were studied along a topographic gradient (738-762 m asl), and analyzed to test the hypothesis that soil chemical and physical attributes play a key role in the structure and floristic composition of these plant communities. Soil and vegetation were sampled in eight replicate plots within each of the four vegetation types. Surface (0-10 cm) soil samples from each plot were analyzed for basic cations, N, P and plant species density for all species was recorded. CCA ordination analysis showed a strong separation between forest and non-forest sites on the first axis, and between herbaceous and shrubby campo rupestre on the second axis. The four vegetation types shared few plant species, which was attributed to their distinctive soil environments and filtering of their constituent species by chemical, physical and hydrological constraints. Thus, we can infer that Edaphic (pedological) factors are crucial in explaining the types and distributions of campo rupestre vegetation associated with ferruginous ironstone uplands (Canga) in Carajás, eastern Amazonia, therefore the soil properties are the main drivers of vegetation composition and structure on these ironstone islands.

Meta-barcoding of 'dirt' DNA from soil reflects vertebrate biodiversity.

PubMed

Andersen, Kenneth; Bird, Karen Lise; Rasmussen, Morten; Haile, James; Breuning-Madsen, Henrik; Kjaer, Kurt H; Orlando, Ludovic; Gilbert, M Thomas P; Willerslev, Eske

2012-04-01

DNA molecules originating from animals and plants can be retrieved directly from sediments and have been used for reconstructing both contemporary and past ecosystems. However, the extent to which such 'dirt' DNA reflects taxonomic richness and structural diversity remains contentious. Here, we couple second generation high-throughput sequencing with 16S mitochondrial DNA (mtDNA) meta-barcoding, to explore the accuracy and sensitivity of 'dirt' DNA as an indicator of vertebrate diversity, from soil sampled at safari parks, zoological gardens and farms with known species compositions. PCR amplification was successful in the full pH range of the investigated soils (6.2 ± 0.2 to 8.3 ± 0.2), but inhibition was detected in extracts from soil of high organic content. DNA movement (leaching) through strata was evident in some sporadic cases and is influenced by soil texture and structure. We find that DNA from the soil surface reflects overall taxonomic richness and relative biomass of individual species. However, one species that was recently introduced was not detected. Furthermore, animal behaviour was shown to influence DNA deposition rates. The approach potentially provides a quick methodological alternative to classical ecological surveys of biodiversity, and most reliable results are obtained with spatial sample replicates, while relative amounts of soil processed per site is of less importance. © 2011 Blackwell Publishing Ltd.

Redistribution of soil nitrogen, carbon and organic matter by mechanical disturbance during whole-tree harvesting in northern hardwoods

USGS Publications Warehouse

Ryan, D.F.; Huntington, T.G.; Wayne, Martin C.

1992-01-01

To investigate whether mechanical mixing during harvesting could account for losses observed from forest floor, we measured surface disturbance on a 22 ha watershed that was whole-tree harvested. Surface soil on each 10 cm interval along 81, randomly placed transects was classified immediately after harvesting as mineral or organic, and as undisturbed, depressed, rutted, mounded, scarified, or scalped (forest floor scraped away). We quantitatively sampled these surface categories to collect soil in which preharvest forest floor might reside after harvest. Mechanically mixed mineral and organic soil horizons were readily identified. Buried forest floor under mixed mineral soil occurred in 57% of mounds with mineral surface soil. Harvesting disturbed 65% of the watershed surface and removed forest floor from 25% of the area. Mechanically mixed soil under ruts with organic or mineral surface soil, and mounds with mineral surface soil contained organic carbon and nitrogen pools significantly greater than undisturbed forest floor. Mechanical mixing into underlying mineral soil could account for the loss of forest floor observed between the preharvest condition and the second growing season after whole-tree harvesting. ?? 1992.

Compilation of hydrologic data, Little Elm Creek, Trinity River basin, Texas, 1968

USGS Publications Warehouse

,

1972-01-01

The U.S. Soil Conservation Service is actively engaged in the installation of flood and soil erosion reducing measures in Texas under the authority of "The Flood Control Act ot 1936 and 1944" and ''Watershed Protection and Flood Prevention Act" (Public Law 566), as amended. In June 1968, the Soil Conservation Service estimated approximately 3,500 structures to be physically and economically feasible for installation in Texas. As of September 30, 1968, 1,271 of these structures had been built. This watershed-development program will have varying but important effects on the surface- and ground-water resources of river basins, especially where a large number of the floodwater-retarding structures are built. Basic hydrologic data are needed to appraise the effects of the structures on water yield and the mode of occurrence of runoff. Hydrologic investigations of these small watersheds were begun by the Geological Survey in 1951 and are now being made in 11 areas (fig. 1). These studies are being made in cooperation with t he Texas Water Development Board, the Soil Conservation Service, the San Antonio River Authority, the city of Dallas, and the Tarrant County Water Control and Improvement District No. 1. The 11 study areas were choson to sample watersheds having different rainfall, topography, geology, and soils. In four of the study areas (Mukewater, North, Little Elm, and Pin Oak Creeks), streamflow and rainfall records were collected prior to construction of the floodwater-retarding structures, thus affording the opportunity for analyses to the conditions before and after" development. Structures have now been built in three of these study areas. A summary of the development of the floodwater-retarding structures on each study area as of September 30, 1968, is shown in table 1.

Canopy structural alterations to nitrogen functions of the soil microbial community in a Quercus virginiana forest

NASA Astrophysics Data System (ADS)

Moore, L. D.; Van Stan, J. T., II; Rosier, C. L.; Gay, T. E.; Wu, T.

2014-12-01

Forest canopy structure controls the timing, amount and chemical character of precipitation supply to soils through interception and drainage along crown surfaces. Yet, few studies have examined forest canopy structural connections to soil microbial communities (SMCs), and none have measured how this affects SMC N functions. The maritime Quercus virginiana Mill. (southern live oak) forests of St Catherine's Island, GA, USA provide an ideal opportunity to examine canopy structural alterations to SMCs and their functioning, as their throughfall varies substantially across space due to dense Tillandsia usneoides L. (spanish moss) mats bestrewn throughout. To examine the impact of throughfall variability on SMC N functions, we examined points along the canopy coverage continuum: large canopy gaps (0%), bare canopy (50-60%), and canopy of heavy T. usneoides coverage (>=85%). Five sites beneath each of the canopy cover types were monitored for throughfall water/ions and soil leachates chemistry for one storm each month over the growing period (7 months, Mar-2014 to Sep-2014) to compare with soil chemistry and SMC communities sampled every two months throughout that same period (Mar, May, Jul, Sep). DGGE and QPCR analysis of the N functioning genes (NFGs) to characterize the ammonia oxidizing bacterial (AOB-amoA), archaea (AOA-amoA), and ammonification (chiA) communities were used to determine the nitrification and decomposition potential of these microbial communities. PRS™-probes (Western Ag Innovations Inc., Saskatoon, Canada) were then used to determine the availability of NO3-N and NH4+N in the soils over a 6-week period to evaluate whether the differing NFG abundance and community structures resulted in altered N cycling.

Global digital data sets of soil type, soil texture, surface slope and other properties: Documentation of archived data tape

NASA Technical Reports Server (NTRS)

Staub, B.; Rosenzweig, C.; Rind, D.

1987-01-01

The file structure and coding of four soils data sets derived from the Zobler (1986) world soil file is described. The data were digitized on a one-degree square grid. They are suitable for large-area studies such as climate research with general circulation models, as well as in forestry, agriculture, soils, and hydrology. The first file is a data set of codes for soil unit, land-ice, or water, for all the one-degree square cells on Earth. The second file is a data set of codes for texture, land-ice, or water, for the same soil units. The third file is a data set of codes for slope, land-ice, or water for the same units. The fourth file is the SOILWRLD data set, containing information on soil properties of land cells of both Matthews' and Food and Agriculture Organization (FAO) sources. The fourth file reconciles land-classification differences between the two and has missing data filled in.

Effect of long-term organic fertilization on the soil pore characteristics of greenhouse vegetable fields converted from rice-wheat rotation fields.

PubMed

Xu, L Y; Wang, M Y; Shi, X Z; Yu, Q B; Shi, Y J; Xu, S X; Sun, W X

2018-08-01

The shift from rice-wheat rotation (RWR) to greenhouse vegetable soils has been widely practiced in China. Several studies have discussed the changes in soil properties with land-use changes, but few studies have sought to address the differences in soil pore properties, especially for fields based on long-term organic fertilization under greenhouse vegetable system from RWR fields. This study uses the X-ray computed tomography (CT) scanning and statistical analysis to compare the long-term effects of the conversion of organic greenhouse vegetable fields (over one year, nine years, and fourteen years) from RWR fields on the soil macropore structure as well as the influencing factors from samples obtained in Nanjing, Jiangsu, China, using the surface soil layer and triplicate samples. The results demonstrated that the macropore structure became more complex and stable, with a higher connectivity, fractal dimension (FD) and a lower degree of anisotropy (DA), as the greenhouse vegetable planting time increased. The total topsoil macroporosity increased considerably, but the rate of increase gradually decelerated with time. The transmission pores (round pores ranging from 50 to 500μm) increased with time, but the biopores (>2000μm) clearly decreased after nine years of use as greenhouse vegetable fields. Soil organic matter (OM) has a significant relationship with the soil pore structure characteristics, especially for the transmission pores. In addition, organic fertilization on the topsoil had a short-term effect on the pores, but the effect stabilized and had a weak influence on the pores over longer periods. These results suggested that organic fertilization was conducive for controlling soil degradation regarding it physical quality for water and oxygen availability in the short term. Copyright © 2018 Elsevier B.V. All rights reserved.

Documentation for Program SOILSIM: A computer program for the simulation of heat and moisture flow in soils and between soils, canopy and atmosphere

NASA Technical Reports Server (NTRS)

Field, Richard T.

1990-01-01

SOILSIM, a digital model of energy and moisture fluxes in the soil and above the soil surface, is presented. It simulates the time evolution of soil temperature and moisture, temperature of the soil surface and plant canopy the above surface, and the fluxes of sensible and latent heat into the atmosphere in response to surface weather conditions. The model is driven by simple weather observations including wind speed, air temperature, air humidity, and incident radiation. The model intended to be useful in conjunction with remotely sensed information of the land surface state, such as surface brightness temperature and soil moisture, for computing wide area evapotranspiration.

Mars 2001 Mission: Addressing Scientific Questions Regarding the Characteristics and Origin of Local Bedrock and Soil

NASA Technical Reports Server (NTRS)

Saunders, R. S.; Arvidson, R. E.; Weitz, C. M.; Marshall, J.; Squyres, S. W.; Christensen, P. R.; Meloy, T.; Smith, P.

1999-01-01

The Mars Surveyor Program 2001 Mission will carry instruments on the orbiter, lander and rover that will support synergistic observations and experiments to address important scientific questions regarding the local bedrock and soils. The martian surface is covered in varying degrees by fine materials less than a few mms in size. Viking and Pathfinder images of the surface indicate that soils at those sites are composed of fine particles. Wheel tracks from the Sojourner rover suggest that soil deposits are composed of particles <40 mm. Viking images show that dunes are common in many areas on Mars and new MOC images indicate that dunes occur nearly everywhere. Dunes on Mars are thought to be composed of 250-500 microns particles based upon Viking IRTM data and Mars wind tunnel experiments. If martian dunes are composed of sand particles > 100 microns and soils are dominated by <10 micron particles, then where are the intermediate grain sizes? Have they been wom away through prolonged transport over the eons? Were they never generated to begin with? Or are they simply less easy to identify because do they not form distinctive geomorphic features such as dunes or uniform mantles that tend to assume superposition in the soil structure?

Enhancing SMAP Soil Moisture Retrievals via Superresolution Techniques

NASA Astrophysics Data System (ADS)

Beale, K. D.; Ebtehaj, A. M.; Romberg, J. K.; Bras, R. L.

2017-12-01

Soil moisture is a key state variable that modulates land-atmosphere interactions and its high-resolution global scale estimates are essential for improved weather forecasting, drought prediction, crop management, and the safety of troop mobility. Currently, NASA's Soil Moisture Active/Passive (SMAP) satellite provides a global picture of soil moisture variability at a resolution of 36 km, which is prohibitive for some hydrologic applications. The goal of this research is to enhance the resolution of SMAP passive microwave retrievals by a factor of 2 to 4 using modern superresolution techniques that rely on the knowledge of high-resolution land surface models. In this work, we explore several super-resolution techniques including an empirical dictionary method, a learned dictionary method, and a three-layer convolutional neural network. Using a year of global high-resolution land surface model simulations as training set, we found that we are able to produce high-resolution soil moisture maps that outperform the original low-resolution observations both qualitatively and quantitatively. In particular, on a patch-by-patch basis we are able to produce estimates of high-resolution soil moisture maps that improve on the original low-resolution patches by on average 6% in terms of mean-squared error, and 14% in terms of the structural similarity index.

Functional microbial community response to nutrient pulses by artificial groundwater recharge practice in surface soils and subsoils.

PubMed

Schütz, Kirsten; Kandeler, Ellen; Nagel, Peter; Scheu, Stefan; Ruess, Liliane

2010-06-01

Subsurface microorganisms are essential constituents of the soil purification processes associated with groundwater quality. In particular, soil enzyme activity determines the biodegradation of organic compounds passing through the soil profile. Transects from surface soil to a depth of 3.5 m were investigated for microbial and chemical soil characteristics at two groundwater recharge sites and one control site. The functional diversity of the microbial community was analyzed via the activity of eight enzymes. Acid phosphomonoesterase was dominant across sites and depths, followed by L-leucine aminopeptidase and beta-glucosidase. Structural [e.g. phospholipid fatty acid (PLFA) pattern] and functional microbial diversities were linked to each other at the nonwatered site, whereas amendment with nutrients (DOC, NO(3)(-)) by flooding uncoupled this relationship. Microbial biomass did not differ between sites, whereas microbial respiration was the highest at the watered sites. Hence, excess nutrients available due to artificial groundwater recharge could not compensate for the limitation by others (e.g. phosphorus as assigned by acid phosphomonoesterase activity). Instead, at a similar microbial biomass, waste respiration via overflow metabolism occurred. In summary, ample supply of carbon by flooding led to a separation of decomposition and microbial growth, which may play an important role in regulating purification processes during groundwater recharge.

Impact of biochar produced from post-harvest residue on the adsorption behavior of diesel oil on loess soil.

PubMed

Jiang, Yu Feng; Sun, Hang; Yves, Uwamungu J; Li, Hong; Hu, Xue Fei

2016-02-01

The primary objective of this study was to investigate the effect of biochar, produced from wheat residue at different temperatures, on the adsorption of diesel oil by loess soil. Kinetic and equilibrium data were processed to understand the adsorption mechanism of diesel by biochar-affected loess soil; dynamic and thermodynamic adsorption experiments were conducted to characterize this adsorption. The surface features and chemical structure of biochar, modified at varying pyrolytic temperatures, were investigated using surface scanning electron microscopy and Fourier transform infrared analysis. The kinetic data showed that the adsorption of diesel oil onto loess soil could be described by a pseudo-second-order kinetic model, with the rate-controlling step being intraparticle diffusion. However, in the presence of biochar, boundary layer control and intraparticle diffusion were both involved in the adsorption. Besides, the adsorption equilibrium data were well described by the Freundlich isothermal model. The saturated adsorption capacity weakened as temperature increased, suggesting a spontaneous exothermic process. Thermodynamic parameter analysis showed that adsorption was mainly a physical process and was enhanced by chemical adsorption. The adsorption capacity of loess soil for diesel oil was weakened with increasing pH. The biochar produced by pyrolytic wheat residue increased the adsorption behavior of petroleum pollutants in loess soil.

Modeling Stand-Scale Patterns in Evapotranspiration and Soil Moisture in a Heterogeneous Plant Canopy: A Coupled Subsurface-Land Surface Approach

NASA Astrophysics Data System (ADS)

Miller, G. R.; Gou, S.; Ferguson, I. M.; Maxwell, R. M.

2011-12-01

Savanna ecosystems present a well-known modeling challenge; understory grasses and overstory woody vegetation combine to form an open, heterogeneous canopy that creates strong spatial differences in soil moisture and evapotranspiration rates. In this analysis, we used ParFlow.CLM to create a stand-scale model of the Tonzi Ranch oak savanna, based on extensive topography, vegetation, soil, and hydrogeology data collected at the site. Measurements included canopy distribution and ground surface elevation from airborne Lidar, depth to groundwater from deep piezometers, soil and rock hydraulic conductivity, and leaf area index. We then compared the results to the site's long-term data records of radiative flux partitioning, obtained using the eddy-covariance method, and soil moisture, collected via a distributed network of capacitance probes. In order to obtain good agreement between the measured and modeled values, we identified several necessary modifications to the current CLM parameterization. These changes included the addition of a "winter grass" type and the alteration of the root structure and water stress functions to accommodate uptake of groundwater by deep roots. Finally, we compared variograms of site parameters and response variables and performed a scaling analysis relating ET and soil moisture variance to sampling size.

Specificity of Cs-137 redistribution in toposequence of arable soils cultivated after the Chernobyl accident

NASA Astrophysics Data System (ADS)

Korobova, Elena; Romanov, Sergey; Baranchukov, Vladimir; Berezkin, Victor; Moiseenko, Fedor; Kirov, Sergey

2017-04-01

Investigations performed after the Chernobyl accident showed high spatial variation of radionuclide contamination of the soil cover in elementary landscape geochemical systems (ELGS) that characterize catena's structure. Our studies of Cs-137 distribution along and cross the slopes of local ridges in natural forested key site revealed a cyclic character of variation of the radionuclide surface activity along the studied transections (Korobova et al, 2008; Korobova, Romanov, 2009; 2011). We hypothesized that the observed pattern reflects a specific secondary migration of Cs-137 with water, and that this process could have taken place in any ELGS. To test this hypothesis a detailed field measurement of Cs-137 surface activity was performed in ELGS in agricultural area cultivated after the Chernobyl accident but later withdrawn from land-use. In situ measurements carried out by field gamma-spectrometry were accompanied by soil core sampling at the selected points. Soil samples were taken in increments of 2 cm down to 20 cm and of 5 cm down to 40 cm. The samples were analyzed for Cs-137 in laboratory using Canberra gamma-spectrometer with HP-Ge detector. Obtained results confirmed the fact of area cultivation down to 20 cm that was clearly traced by Cs-137 profile in soil columns. At the same time, the measurements also showed a cyclic character of Cs-137 variation in a sequence of ELGS from watershed to the local depression similar to that found in woodland key site. This proved that the observed pattern is a natural process typical for matter migration in ELGS independently of the vegetation type and ploughing. Therefore, spatial aspect is believed to be an important issue for development of adequate technique for a forecast of contamination of agricultural production and remediation of the soil cover on the local scale within the contaminated areas. References Korobova, E.M., Romanov, S.L., 2009. A Chernobyl 137Cs contamination study as an example for the spatial structure of geochemical fields and modeling of the geochemical field //Chemometrics and Intelligent Laboratory Systems, 99, 1-8. Korobova, E., Romanov S., 2011. Experience of mapping spatial structure of Cs-137 in natural landscape and patterns of its distribution in soil toposequence // Journal of Geochemical Exploration, 109, 1-3, 139-145. Korobova Elena, Sergey Romanov, Vladimir Samsonov, Fedor Moiseenko, 2008. Peculiarities of spatial structure of 137Cs contamination field in landscape toposequence: regularities in geo-field structure. Proceedings of the International Conference on Radioecology and Environmental Radioactivity, 15-20 June 2008, Bergen, Norway, Part 2, 182-186.

Leaving moss and litter layers undisturbed reduces the short-term environmental consequences of heathland managed burns.

PubMed

Grau-Andrés, Roger; Davies, G Matt; Waldron, Susan; Scott, E Marian; Gray, Alan

2017-12-15

Variation in the structure of ground fuels, i.e. the moss and litter (M/L) layer, may be an important control on fire severity in heather moorlands and thus influence vegetation regeneration and soil carbon dynamics. We completed experimental fires in a Calluna vulgaris-dominated heathland to study the role of the M/L layer in determining (i) fire-induced temperature pulses into the soil and (ii) post-fire soil thermal dynamics. Manually removing the M/L layer before burning increased fire-induced soil heating, both at the soil surface and 2 cm below. Burnt plots where the M/L layer was removed simulated the fuel structure after high severity fires where ground fuels are consumed but the soil does not ignite. Where the M/L layer was manually removed, either before or after the fire, post-fire soil thermal dynamics showed larger diurnal and seasonal variation, as well as similar patterns to those observed after wildfires, compared to burnt plots where the M/L layer was not manipulated. We used soil temperatures to explore potential changes in post-fire soil respiration. Simulated high fire severity (where the M/L layer was manually removed) increased estimates of soil respiration in warm months. With projected fire regimes shifting towards higher severity fires, our results can help land managers develop strategies to balance ecosystem services in Calluna-dominated habitats. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

STIR Proposal For Research Area 2.1.2 Surface Energy Balance: Transient Soil Density Impacts Land Surface Characteristics and Characterization

DTIC Science & Technology

2015-12-22

not shown). The relatively small differences were likely associated with differences in surface albedo and longwave radiation from soil surface. Ground...SECURITY CLASSIFICATION OF: Soil density is commonly treated as static in studies on land surface property dynamics. Magnitudes of errors associated...with this assumption are largely unknown. Objectives of this preliminary investigation were to: i) quantify effects of soil density variation on soil

The utility of surface temperature measurements for the remote sensing of surface soil water status

NASA Technical Reports Server (NTRS)

Idso, S. B.; Jackson, R. D.; Reginato, R. J.; Schmugge, T. J.

1975-01-01

Experiments carried out on an Avondale loam soil indicated that the thermal inertia concept of soil water content detection is reasonably sound. The volumetric water contents of surface soil layers between 2 and 4 cm thick were found to be linear functions of the amplitude of the diurnal surface soil temperature wave for clear day-night periods. They were also found to be linear functions of the daily maximum value of the surface soil-air-temperature differential. Tests on three additional soils ranging from sandy loam to clay indicated that the relations determined for Avondale loam could not be accurately applied to these other soil types. When the moisture characteristic curves of each soil were used to transform water contents into pressure potentials, however, it was found that soil water pressure potential could be determined without prior knowledge of soil type, and thus its value as a potential soil water status survey tool was significantly enhanced.

Antisoiling technology: Theories of surface soiling and performance of antisoiling surface coatings

NASA Technical Reports Server (NTRS)

Cuddihy, E. F.; Willis, P. B.

1984-01-01

Physical examination of surfaces undergoing natural outdoor soiling suggests that soil matter accumulates in up to three distinct layers. The first layer involves strong chemical attachment or strong chemisorption of soil matter on the primary surface. The second layer is physical, consisting of a highly organized arrangement of soil creating a gradation in surface energy from a high associated with the energetic first layer to the lowest possible state on the outer surfce of the second layer. The lowest possible energy state is dictated by the physical nature of the regional atmospheric soiling materials. These first two layers are resistant to removal by rain. The third layer constitutes a settling of loose soil matter, accumulating in dry periods and being removed during rainy periods. Theories and evidence suggest that surfaces that should be naturally resistant to the formation of the first two-resistant layers should be hard, smooth, hydrophobic, free of first-period elements, and have the lowest possible surface energy. These characteristics, evolving as requirements for low-soiling surfaces, suggest that surfaces or surface coatings should be of fluorocarbon chemistry. Evidence for the three-soil-layer concept, and data on the positive performance of candidate fluorocarbon coatings on glass and transparent plastic films after 28 months of outdoor exposure, are presented.

Scratching technique for the study and analysis of soil surface abrasion mechanism

NASA Astrophysics Data System (ADS)

Ta, Wanquan

2007-11-01

Aeolian abrasion is the most fundamental and active surface process that takes place in arid and semi-arid environments. Its nature is a wear process for wind blown grains impinging on a soil or sediment surface, which causes particles and aggregates to fracture from the soil surface through a series of plastic and brittle cracking deformation such as cutting, ploughing and brittle fracturing. Using a Universal Micro-Tribometer (UMT), a scratching test was carried out on six soil surfaces (sandy soil, sand loam, silt loam, loam, silt clay loam, and silt clay). The results indicate that traces of normal and tangential force vs. time show a jagged curve, which can reflect the plastic deformation and brittle fracturing of aggregates and particles of various sizes fractured from the soil surfaces. The jagged curve peaks, and the area enclosed underneath, may represent the bonding forces and bonding energies of some aggregates and grains on the soil surface, respectively. Connecting the scratching test with an impact abrasion experiment furthermore demonstrates that soil surface abrasion rates are proportional to the square of speeds of impacting particles and to the 2.6 power of mean soil grain size, and inversely proportional to the 1.5 power of specific surface abrasive energy or to the 1.7 power of specific surface hardness.

Increased precipitation accelerates soil organic matter turnover associated with microbial community composition in topsoil of alpine grassland on the eastern Tibetan Plateau.

PubMed

Han, Conghai; Wang, Zongli; Si, Guicai; Lei, Tianzhu; Yuan, Yanli; Zhang, Gengxin

2017-10-01

Large quantities of carbon are stored in alpine grassland of the Tibetan Plateau, which is extremely sensitive to climate change. However, it remains unclear whether soil organic matter (SOM) in different layers responds to climate change analogously, and whether microbial communities play vital roles in SOM turnover of topsoil. In this study we measured and collected SOM turnover by the 14 C method in alpine grassland to test climatic effects on SOM turnover in soil profiles. Edaphic properties and microbial communities in the northwestern Qinghai Lake were investigated to explore microbial influence on SOM turnover. SOM turnover in surface soil (0-10 cm) was more sensitive to precipitation than that in subsurface layers (10-40 cm). Precipitation also imposed stronger effects on the composition of microbial communities in the surface layer than that in deeper soil. At the 5-10 cm depth, the SOM turnover rate was positively associated with the bacteria/fungi biomass ratio and the relative abundance of Acidobacteria, both of which are related to precipitation. Partial correlation analysis suggested that increased precipitation could accelerate the SOM turnover rate in topsoil by structuring soil microbial communities. Conversely, carbon stored in deep soil would be barely affected by climate change. Our results provide valuable insights into the dynamics and storage of SOM in alpine grasslands under future climate scenarios.

[Dynamics of soil physical properties and biological soil crust during the vegetation restoration process of abandoned croplands in the Ordos Plateau, China].

PubMed

Cai, Wen Tao; Li, He Yi; Lai, Li Ming; Zhang, Xiao Long; Guan, Tian Yu; Zhou, Ji Hua; Jiang, Lian He; Zheng, Yuan Run

2017-03-18

A series of typical abandoned croplands in the regions of Ruanliang and Yingliang in the Ordos Plateau, China, were selected, and dynamics of the surface litter, biological soil crust and soil bulk density, soil texture, and soil moisture in different soil layers were investigated. The results showed that in the abandoned cropland in Ruanliang, the clay particle content and surface litter of the surface soil layer (0-10 cm) increased during the restoration process, while that of soil bulk density substantially decreased and soil water content slightly increased in the surface soil. In the medium soil layer (10-30 cm), the clay particle content increased and the soil water content slightly decreased. In the deep soil layer (30-50 cm), there was a relatively large variation in the physical properties. In the abandoned cropland in Yingliang, the coverage of litter and the coverage and thickness of the biological soil crust increased during the abandonment process. The surface soil bulk density, soil clay particle content and soil water content remained constant in 0-10 cm soil layer, while the physical properties varied substantially in 10-40 cm soil layer. The shallow distribution of the soil water content caused by the accumulation of the litter and clay particles on the soil surface might be the key reason of the replacement of the semi-shrub Artemisia ordosica community with a perennial grass community over the last 20 years of the abandoned cropland in Ruanliang. The relatively high soil water content in the shallow layer and the development of the biological soil crust might explain why the abandoned cropland in Yingliang was not invaded by the semi-shrub A. ordosica during the restoration process.

Vs30 mapping at selected sites within the Greater Accra Metropolitan Area

NASA Astrophysics Data System (ADS)

Nortey, Grace; Armah, Thomas K.; Amponsah, Paulina

2018-06-01

A large part of Accra is underlain by a complex distribution of shallow soft soils. Within seismically active zones, these soils hold the most potential to significantly amplify seismic waves and cause severe damage, especially to structures sited on soils lacking sufficient stiffness. This paper presents preliminary site classification for the Greater Accra Metropolitan Area of Ghana (GAMA), using experimental data from two-dimensional (2-D) Multichannel Analysis of Surface Wave (MASW) technique. The dispersive characteristics of fundamental mode Rayleigh type surface waves were utilized for imaging the shallow subsurface layers (approx. up to 30 m depth) by estimating the 1D (depth) and 2D (depth and surface location) shear wave velocities at 5 selected sites. The average shear wave velocity for 30 m depth (Vs30), which is critical in evaluating the site response of the upper 30 m, was estimated and used for the preliminary site classification of the GAM area, as per NEHRP (National Earthquake Hazards Reduction Program). Based on the Vs30 values obtained in the study, two common site types C, and D corresponding to shallow (>6 m < 30 m) weathered rock and deep (up 30 m thick) stiff soils respectively, have been identified within the study area. Lower velocity profiles are inferred for the residual soils (sandy to silty clays), derived from the Accraian Formation that lies mainly within Accra central. Stiffer soil sites lie to the north of Accra, and to the west near Nyanyano. The seismic response characteristics over the residual soils in the GAMA have become apparent using the MASW technique. An extensive site effect map and a more robust probabilistic seismic hazard analysis can now be efficiently built for the metropolis, by considering the site classes and design parameters obtained from this study.

The effect of water harvesting techniques on runoff, sedimentation, and soil properties.

PubMed

Al-Seekh, Saleh H; Mohammad, Ayed G

2009-07-01

This study addressed the hydrological processes of runoff and sedimentation, soil moisture content, and properties under the effect of different water harvesting techniques (treatments). The study was conducted at three sites, representing environmental condition gradients, located in the southern part of the West Bank. For each treatment, the study evaluated soil chemical and physical properties, soil moisture at 30 cm depth, surface runoff and sedimentation at each site. Results showed that runoff is reduced by 65-85% and sedimentation by 58-69% in stone terraces and semi-circle bunds compared to the control at the semi-humid site. In addition, stone terraces and contour ridges significantly reduced the amount of total runoff by 80% and 73%, respectively, at the arid site. Soil moisture content was significantly increased by water harvesting techniques compared to the control in all treatments at the three study sites. In addition, the difference between the control and the water harvesting structures were higher in the arid and semi-arid areas than in the semi-humid area. Soil and water conservation, via utilization of water harvesting structures, is an effective principle for reducing the negative impact of high runoff intensity and subsequently increasing soil moisture storage from rainfall. Jessour systems in the valley and stone terraces were effective in increasing soil moisture storage, prolonging the growing season for natural vegetation, and decreasing the amount of supplemental irrigation required for growing fruit trees.

The Effect of Water Harvesting Techniques on Runoff, Sedimentation, and Soil Properties

NASA Astrophysics Data System (ADS)

Al-Seekh, Saleh H.; Mohammad, Ayed G.

2009-07-01

This study addressed the hydrological processes of runoff and sedimentation, soil moisture content, and properties under the effect of different water harvesting techniques (treatments). The study was conducted at three sites, representing environmental condition gradients, located in the southern part of the West Bank. For each treatment, the study evaluated soil chemical and physical properties, soil moisture at 30 cm depth, surface runoff and sedimentation at each site. Results showed that runoff is reduced by 65-85% and sedimentation by 58-69% in stone terraces and semi-circle bunds compared to the control at the semi-humid site. In addition, stone terraces and contour ridges significantly reduced the amount of total runoff by 80% and 73%, respectively, at the arid site. Soil moisture content was significantly increased by water harvesting techniques compared to the control in all treatments at the three study sites. In addition, the difference between the control and the water harvesting structures were higher in the arid and semi-arid areas than in the semi-humid area. Soil and water conservation, via utilization of water harvesting structures, is an effective principle for reducing the negative impact of high runoff intensity and subsequently increasing soil moisture storage from rainfall. Jessour systems in the valley and stone terraces were effective in increasing soil moisture storage, prolonging the growing season for natural vegetation, and decreasing the amount of supplemental irrigation required for growing fruit trees.

Retrieval of Soil Moisture and Roughness from the Polarimetric Radar Response

NASA Technical Reports Server (NTRS)

Sarabandi, Kamal; Ulaby, Fawwaz T.

1997-01-01

The main objective of this investigation was the characterization of soil moisture using imaging radars. In order to accomplish this task, a number of intermediate steps had to be undertaken. In this proposal, the theoretical, numerical, and experimental aspects of electromagnetic scattering from natural surfaces was considered with emphasis on remote sensing of soil moisture. In the general case, the microwave backscatter from natural surfaces is mainly influenced by three major factors: (1) the roughness statistics of the soil surface, (2) soil moisture content, and (3) soil surface cover. First the scattering problem from bare-soil surfaces was considered and a hybrid model that relates the radar backscattering coefficient to soil moisture and surface roughness was developed. This model is based on extensive experimental measurements of the radar polarimetric backscatter response of bare soil surfaces at microwave frequencies over a wide range of moisture conditions and roughness scales in conjunction with existing theoretical surface scattering models in limiting cases (small perturbation, physical optics, and geometrical optics models). Also a simple inversion algorithm capable of providing accurate estimates of soil moisture content and surface rms height from single-frequency multi-polarization radar observations was developed. The accuracy of the model and its inversion algorithm is demonstrated using independent data sets. Next the hybrid model for bare-soil surfaces is made fully polarimetric by incorporating the parameters of the co- and cross-polarized phase difference into the model. Experimental data in conjunction with numerical simulations are used to relate the soil moisture content and surface roughness to the phase difference statistics. For this purpose, a novel numerical scattering simulation for inhomogeneous dielectric random surfaces was developed. Finally the scattering problem of short vegetation cover above a rough soil surface was considered. A general scattering model for grass-blades of arbitrary cross section was developed and incorporated in a first order random media model. The vegetation model and the bare-soil model are combined and the accuracy of the combined model is evaluated against experimental observations from a wheat field over the entire growing season. A complete set of ground-truth data and polarimetric backscatter data were collected. Also an inversion algorithm for estimating soil moisture and surface roughness from multi-polarized multi-frequency observations of vegetation-covered ground is developed.

Response of the Atmospheric Boundary Layer and Soil Layer to a High Altitude, Dense Aerosol Cover.

NASA Astrophysics Data System (ADS)

Garratt, J. R.; Pittock, A. B.; Walsh, K.

1990-01-01

The response of the atmospheric boundary layer to the appearance of a high-altitude smoke layer has been investigated in a mesoscale numerical model of the atmosphere. Emphasis is placed on the changes in mean boundary-layer structure and near-surface temperatures when smoke of absorption optical depth (AOD) in the, range 0 to 1 is introduced. Calculations have been made at 30°S, for different soil thermal properties and degrees of surface wetness, over a time period of several days during which major smoke-induced cooling occurs. The presence of smoke reduces the daytime mixed-layer depth and, for large enough values of AOD, results in a daytime surface inversion with large cooling confined to heights of less than a few hundred meters. Smoke-induced reductions in daytime soil and air temperatures of several degrees are typical, dependent critically upon soil wetness and smoke AOD. Locations near the coast experience reduced cooling whenever there is a significant onshore flow related to a sea breeze (this would also be the case with a large-scale onshore flow). The sea breeze itself disappears for large enough smoke AOD and, over sloping coastal terrain, a smoke-induced, offshore drainage flow may exist throughout the diurnal cycle.

Coupled Environmental Processes in the Mojave Desert and Implications for ET Covers as Stable Landforms

DOE Office of Scientific and Technical Information (OSTI.GOV)

D. Shafer; M. Y oung; S. Zitzer

2006-01-18

Monolayer evapotranspiration (ET) covers are the baseline method for closure of disposal sites for low-level radioactive waste (LLW), mixed LLW, and transuranic (TRU) waste at the Nevada Test Site (NTS). The regulatory timeline is typically 1,000 years for LLW and 10,000 years for TRU waste. Covers for such waste have different technical considerations than those with shorter timelines because they are subject to environmental change for longer periods of time, and because the environmental processes are often coupled. To evaluate these changes, four analog sites (approximately 30, 1,000 to 2,000, 7,000 to 12,500, and 125,000 years in age) on themore » NTS were analyzed to address the early post-institutional control period (the youngest site), the 1,000-year compliance period for disposal of LLW, and the 10,000-year period for TRU waste. Tests included soil texture, structure, and morphology; surface soil infiltration and hydraulic conductivity; vegetation and faunal surveys; and literature reviews. Separate measurements were made in plant undercanopy and intercanopy areas. The results showed a progressive increase in silt and clay content of surface soils with age. Changes in soil texture and structure led to a fivefold decline in saturated hydraulic conductivity in intercanopy areas, but no change in undercanopies, which were subject to bioturbation. These changes may have been responsible for the reduction in total plant cover, most dramatically in intercanopy areas, primarily because more precipitation either runs off the site or is held nearer to the surface where plant roots are less common. The results suggest that covers may evolve over longer timeframes to stable landforms that minimize the need for active maintenance.« less

Thermal signature characteristics of vehicle/terrain interaction disturbances: implications for battlefield vehicle classification.

PubMed

Eastes, John W; Mason, George L; Kusinger, Alan E

2004-05-01

Thermal emissivity spectra (8-14 microm) of track impressions/background were determined in conjunction with operation of six military vehicle types, T-72 and M1 Tanks, an M2 Bradley Fighting Vehicle, a 5-ton truck, a D7 tractor, and a High Mobility Multipurpose Wheeled Vehicle (HMMWV), over diverse soil surfaces to determine if vehicle type could be related to track thermal signatures. Results suggest soil compaction and fragmentation/pulverization are primary parameters affecting track signatures and that soil and vehicle/terrain-contact type determine which parameter dominates. Steel-tracked vehicles exert relatively low ground-contact pressure but tend to fragment/pulverize soil more so than do rubber-tired vehicles, which tend mainly to compact. In quartz-rich, lean clay soil tracked vehicles produced impressions with spectral contrast of the quartz reststrahlen features decreased from that of the background. At the same time, 5-ton truck tracks exhibited increased contrast on the same surface, suggesting that steel tracks fragmented soil while rubber tires mainly produced compaction. The structure of materials such as sand and moist clay-rich river sediment makes them less subject to further fragmentation/pulverization; thus, compaction was the main factor affecting signatures in these media, and both tracked and wheeled vehicles created impressions with increased spectral contrast on these surfaces. These results suggest that remotely sensed thermal signatures could differentiate tracked and wheeled vehicles on terrain in many areas of the world of strategic interest. Significant applications include distinguishing visually/spectrally identical lightweight decoys from actual threat vehicles.

A Conceptual Approach to Assimilating Remote Sensing Data to Improve Soil Moisture Profile Estimates in a Surface Flux/Hydrology Model. Part 1; Overview

NASA Technical Reports Server (NTRS)

Crosson, William L.; Laymon, Charles A.; Inguva, Ramarao; Schamschula, Marius; Caulfield, John

1998-01-01

Knowledge of the amount of water in the soil is of great importance to many earth science disciplines. Soil moisture is a key variable in controlling the exchange of water and energy between the land surface and the atmosphere. Thus, soil moisture information is valuable in a wide range of applications including weather and climate, runoff potential and flood control, early warning of droughts, irrigation, crop yield forecasting, soil erosion, reservoir management, geotechnical engineering, and water quality. Despite the importance of soil moisture information, widespread and continuous measurements of soil moisture are not possible today. Although many earth surface conditions can be measured from satellites, we still cannot adequately measure soil moisture from space. Research in soil moisture remote sensing began in the mid 1970s shortly after the surge in satellite development. Recent advances in remote sensing have shown that soil moisture can be measured, at least qualitatively, by several methods. Quantitative measurements of moisture in the soil surface layer have been most successful using both passive and active microwave remote sensing, although complications arise from surface roughness and vegetation type and density. Early attempts to measure soil moisture from space-borne microwave instruments were hindered by what is now considered sub-optimal wavelengths (shorter than 5 cm) and the coarse spatial resolution of the measurements. L-band frequencies between 1 and 3 GHz (10-30 cm) have been deemed optimal for detection of soil moisture in the upper few centimeters of soil. The Electronically Steered Thinned Array Radiometer (ESTAR), an aircraft-based instrument operating a 1,4 GHz, has shown great promise for soil moisture determination. Initiatives are underway to develop a similar instrument for space. Existing space-borne synthetic aperture radars (SARS) operating at C- and L-band have also shown some potential to detect surface wetness. The advantage of radar is its much higher resolution than passive microwave systems, but it is currently hampered by surface roughness effects and the lack of a good algorithm based on a single frequency and single polarization. In addition, its repeat frequency is generally low (about 40 days). In the meantime, two new radiometers offer some hope for remote sensing of soil moisture from space. The Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI), launched in November 1997, possesses a 10.65 GHz channel and the Advanced Microwave Scanning Radiometer (AMSR) on both the ADEOS-11 and Earth Observing System AM-1 platforms to be launched in 1999 possesses a 6.9 GHz channel. Aside from issues about interference from vegetation, the coarse resolution of these data will provide considerable challenges pertaining to their application. The resolution of TMI is about 45 km and that of AMSR is about 70 km. These resolutions are grossly inconsistent with the scale of soil moisture processes and the spatial variability of factors that control soil moisture. Scale disparities such as these are forcing us to rethink how we assimilate data of various scales in hydrologic models. Of particular interest is how to assimilate soil moisture data by reconciling the scale disparity between what we can expect from present and future remote sensing measurements of soil moisture and modeling soil moisture processes. It is because of this disparity between the resolution of space-based sensors and the scale of data needed for capturing the spatial variability of soil moisture and related properties that remote sensing of soil moisture has not met with more widespread success. Within a single footprint of current sensors at the wavelengths optimal for this application, in most cases there is enormous heterogeneity in soil moisture created by differences in landcover, soils and topography, as well as variability in antecedent precipitation. It is difficult to interpret the meaning of 'mean' soil moisture under such conditions and even more difficult to apply such a value. Because of the non-linear relationships between near-surface soil moisture and other variables of interest, such as surface energy fluxes and runoff, mean soil moisture has little applicability at such large scales. It is for these reasons that the use of remote sensing in conjunction with a hydrologic model appears to be of benefit in capturing the complete spatial and temporal structure of soil moisture. This paper is Part I of a four-part series describing a method for intermittently assimilating remotely-sensed soil moisture information to improve performance of a distributed land surface hydrology model. The method, summarized in section II, involves the following components, each of which is detailed in the indicated section of the paper or subsequent papers in this series: Forward radiative transfer model methods (section II and Part IV); Use of a Kalman filter to assimilate remotely-sensed soil moisture estimates with the model profile (section II and Part IV); Application of a soil hydrology model to capture the continuous evolution of the soil moisture profile within and below the root zone (section III); Statistical aggregation techniques (section IV and Part II); Disaggregation techniques using a neural network approach (section IV and Part III); and Maximum likelihood and Bayesian algorithms for inversely solving for the soil moisture profile in the upper few cm (Part IV).

Microwave remote sensing and its application to soil moisture detection

NASA Technical Reports Server (NTRS)

Newton, R. W. (Principal Investigator)

1977-01-01

The author has identified the following significant results. Experimental measurements were utilized to demonstrate a procedure for estimating soil moisture, using a passive microwave sensor. The investigation showed that 1.4 GHz and 10.6 GHz can be used to estimate the average soil moisture within two depths; however, it appeared that a frequency less than 10.6 GHz would be preferable for the surface measurement. Average soil moisture within two depths would provide information on the slope of the soil moisture gradient near the surface. Measurements showed that a uniform surface roughness similar to flat tilled fields reduced the sensitivity of the microwave emission to soil moisture changes. Assuming that the surface roughness was known, the approximate soil moisture estimation accuracy at 1.4 GHz calculated for a 25% average soil moisture and an 80% degree of confidence, was +3% and -6% for a smooth bare surface, +4% and -5% for a medium rough surface, and +5.5% and -6% for a rough surface.

Soil gas (²²²Rn, CO₂, ⁴He) behaviour over a natural CO₂ accumulation, Montmiral area (Drôme, France): geographical, geological and temporal relationships.

PubMed

Gal, Frédérick; Joublin, Franck; Haas, Hubert; Jean-Prost, Véronique; Ruffier, Véronique

2011-02-01

The south east basin of France shelters deep CO₂ reservoirs often studied with the aim of better constraining geological CO₂ storage operations. Here we present new soil gas data, completing an existing dataset (CO₂, ²²²Rn, ⁴He), together with mineralogical and physical characterisations of soil columns, in an attempt to better understand the spatial distribution of gas concentrations in the soils and to rule on the sealed character of the CO₂ reservoir at present time. Anomalous gas concentrations were found but did not appear to be clearly related to geological structures that may drain deep gases up to the surface, implying a dominant influence of near surface processes as indicated by carbon isotope ratios. Coarse grained, quartz-rich soils favoured the existence of high CO₂ concentrations. Fine grained clayey soils preferentially favoured the existence of ²²²Rn but not CO₂. Soil formations did not act as barriers preventing gas migrations in soils, either due to water content or due to mineralogical composition. No abundant leakage from the Montmiral reservoir can be highlighted by the measurements, even near the exploitation well. As good correlation between CO₂ and ²²²Rn concentrations still exist, it is suggested that ²²²Rn migration is also CO₂ dependent in non-leaking areas--diffusion dominated systems. Copyright © 2010 Elsevier Ltd. All rights reserved.

Mapping fields of 137Cs contamination in soils in the context of their stability and hierarchical spatial structure

NASA Astrophysics Data System (ADS)

Korobova, E.; Romanov, S.

2009-04-01

Technogenic radioisotopes now dispersed in the environment are involved in natural and technogenic processes forming specific geochemical fields and serving as tracers of modern mass migration and geofield transformation. Cs-137 radioisotopes having a comparatively long life time are known for a fast fixation by the top soil layer; radiocesium activity can be measured in the surface layer in field conditions. This makes 137Cs rather convenient for the study and modeling a behavior of toxic elements in soils [1-3, 5] and for the investigation of relative stability and hierarchical fractal structures of the soil contamination of the atmospheric origin [2]. The objective of the experimental study performed on the test site in Bryansk region was to find and prove polycentric regularities in the structure of 137Cs contamination field formed after the Chernobyl accident in natural conditions. Such a character of spatial variability can be seen on the maps showing different soil parameters and chemical element distribution measured in grids [3-5]. The research was undertaken to support our idea of the regular patterns in the contamination field structure that enables to apply a mathematical theory of the field to the geochemical fields modeling on the basis of a limited number of direct measurements sufficient to reproduce the configuration and main parameters of the geochemical field structure on the level of the elementary landscape geochemical system (top-slope-bottom). Cs-137 field measurements were verified by a direct soil sampling. Soil cores dissected into subsamples with increments of 2, 5 and 10 cm, were taken to the depth of 40 cm at points with various surface activity located at different elements of relief. According to laboratory measurements 137Cs inventory in soils varied from 344 to 3448 kBq/m2 (983 kBq/m2 on the average). From 95,1% to 98,0% to of the total inventory was retained in the top 20-cm soil layer. This confirmed that field gamma spectrometry could be used to investigate patterns of 137Cs spatial redistribution in the top soil layers. The portion of 137Cs conserved in top layers corresponded to the meso- and micro relief elements. The character and stability of 137Cs spatial structure was studied by measuring its activity within nested plots with different steps of 5, 2, 1 and 0,2 m (the latter was a minimum resolution step for the field NaI detector). Performed measurements showed that the contamination field of 137Cs had a regular structure of polycentric character and exhibited a decrease in spatial variability of contamination with the decrease of the measured area. Repeated measurements of soil contamination in successive years of 2005-2008 along and cross the slopes provided with topographic survey proved the stability of contamination field (r=0, 915, n=121, r=0,912, n=30) and its relation to the meso- and microrelief features. Variation 137Cs activity in lateral direction (along the slopes and thalweg of the hollow)showed a regular character also. In our opinion the regularity in 137Cs spatial structure in the soil cover may result from radionuclide redistribution with the surface and subsurface water flow highly sensitive to the changes in elevation of different scale, and to the slope length and inclination. Cs-137 lateral distribution pattern was likely to reflect alternation of lateral and vertical water mass migration along the slopes. The performed study showing regularity in 137Cs redistribution seems to open new possibilities to develop the deterministic strategy in the study of contamination fields and modeling toxic elements spatial distribution in the soil cover on different scales. The authors are much obliged to Dr. V. Samsonov and Dr. F. Moiseenko for participation in the field work and to S. Kirov for the performance of the laboratory measurement of the soil and plant samples. References 1. Khomutinin, Yu.V., Kashparov, V.A., Zhebrovskaya, E.I., 2001. Optimization of sampling and measurement of the specimen for radioecological monitoring. UkrNIISKHR, Kiev. 2. Korobova, E.M., Romanov, S.L., Samsonov, V.L., Kirov, S.S., 2006. Experimental study of spatial 137Cs redistribution in paragenetic elementary landscapes, in: Kasimov, N.S. et al (Eds.), Geochemistry of biosphere (devoted to 90-th anniversary of A.I. Perelman), MSU, IGEM, RFFI, Moscow-Smolensk, pp.157-159. 3. Linnik, V.G., Saveliev, A.A., Govorun, A.P., Ivanitsky, O.M., Sokolov, A.V., 2006. Analysis of the Cs-137 contamination field on micro-landscape scale within the virgin meadows in the western part of the Bryansk region, in: Kasimov, N.S. et al (Eds.), Geochemistry of biosphere (devoted to 90-th anniversary of A.I. Perelman), MSU, IGEM, RFFI, Moscow-Smolensk, pp. 201-204. 4. Samsonova V.P. Spatial variability of the soil parameters. On example of soddy-podozolic soils. Moscow, LKI, 2008, 156 p. 5.Shcheglov, A.I., Tsvetnova, O.B., Klyashtorin, A.I., 2001. Biogeochemical migration of technogenic radionuclides in forest ecosystems. Nauka, Moscow.

[Preliminary Study on Linear Alkylbenzenes as Indicator for Process of Urbanization].

PubMed

Xu, Te; Zeng, Hui; Ni, Hong-Gang

2016-01-15

In this study, we selected Shenzhen City as a typical region of urbanization and took Linear alkylbenzenes ( LABs) as an environmental molecular marker to investigate the relationship between soil LABs levels and urbanization indexes on the basis of analysis of spatial distribution of LABs in surface soil. Our results indicated relations between the LABs levels in soil and the five urbanization indexes, such as the population, water supply, urban construction, income and expenditure, as well as industrial structure. These results suggested that LABs levels were correlated with urbanization and could be used as an environmental molecular indicator for the process of urbanization.

Environmental drivers of soil microbial community structure and function at the Avon River Critical Zone Observatory.

PubMed

Gleeson, Deirdre; Mathes, Falko; Farrell, Mark; Leopold, Matthias

2016-11-15

The Critical Zone is defined as the thin, permeable layer from the tops of the trees to the bottom of the bedrock that sustains terrestrial life on Earth. The geometry and shape of the various weathering zones are known as the critical zone architecture. At the centre of the Critical Zone are soils and the microorganisms that inhabit them. In Western Australia, the million-year-old stable weathering history and more recent lateral erosion during the past hundreds of thousands of years have created a geomorphic setting where deep weathering zones are now exposed on the surface along the flanks of many lateritic hills. These old weathering zones provide diverse physical and chemical properties that influence near surface pedologic conditions and thus likely shape current surface microbiology. Here, we present data derived from a small lateritic hill on the UWA Farm Ridgefield. Spatial soil sampling revealed the contrasting distribution patterns of simple soil parameters such as pH (CaCl2) and electric conductivity. These are clearly linked with underlying changes of the critical zone architecture and show a strong contrast with low values of pH3.3 at the top of the hill to pH5.3 at the bottom. These parameters were identified as major drivers of microbial spatial variability in terms of bacterial and archaeal community composition but not abundance. In addition, we used sensitive (14)C labelling to assess turnover of three model organic nitrogen compounds - an important biogeochemical functional trait relating to nutrient availability. Though generally rapid and in the order of rates reported elsewhere (t½<5h), some points in the sampling area showed greatly reduced turnover rates (t½>10h). In conclusion, we have shown that the weathering and erosion history of ancient Western Australia affects the surface pedology and has consequences for microbial community structure and function. Copyright © 2016 Elsevier B.V. All rights reserved.

Directional Canopy Emissivity Estimation Based on Spectral Invariants

NASA Astrophysics Data System (ADS)

Guo, M.; Cao, B.; Ren, H.; Yongming, D.; Peng, J.; Fan, W.

2017-12-01

Land surface emissivity is a crucial parameter for estimating land surface temperature from remote sensing data and also plays an important role in the physical process of surface energy and water balance from local to global scales. To our knowledge, the emissivity varies with surface type and cover. As for the vegetation, its canopy emissivity is dependent on vegetation types, viewing zenith angle and structure that changes in different growing stages. Lots of previous studies have focused on the emissivity model, but few of them are analytic and suited to different canopy structures. In this paper, a new physical analytic model is proposed to estimate the directional emissivity of homogenous vegetation canopy based on spectral invariants. The initial model counts the directional absorption in six parts: the direct absorption of the canopy and the soil, the absorption of the canopy and soil after a single scattering and after multiple scattering within the canopy-soil system. In order to analytically estimate the emissivity, the pathways of photons absorbed in the canopy-soil system are traced using the re-collision probability in Fig.1. After sensitive analysis on the above six absorptions, the initial complicated model was further simplified as a fixed mathematic expression to estimate the directional emissivity for vegetation canopy. The model was compared with the 4SAIL model, FRA97 model, FRA02 model and DART model in Fig.2, and the results showed that the FRA02 model is significantly underestimated while the FRA97 model is a little underestimated, on basis of the new model. On the contrary, the emissivity difference between the new model with the 4SAIL model and DART model was found to be less than 0.002. In general, since the new model has the advantages of mathematic expression with accurate results and clear physical meaning, the model is promising to be extended to simulate the directional emissivity for the discrete canopy in further study.

Divergent surface and total soil moisture projections under global warming

USGS Publications Warehouse

Berg, Alexis; Sheffield, Justin; Milly, Paul C.D.

2017-01-01

Land aridity has been projected to increase with global warming. Such projections are mostly based on off-line aridity and drought metrics applied to climate model outputs but also are supported by climate-model projections of decreased surface soil moisture. Here we comprehensively analyze soil moisture projections from the Coupled Model Intercomparison Project phase 5, including surface, total, and layer-by-layer soil moisture. We identify a robust vertical gradient of projected mean soil moisture changes, with more negative changes near the surface. Some regions of the northern middle to high latitudes exhibit negative annual surface changes but positive total changes. We interpret this behavior in the context of seasonal changes in the surface water budget. This vertical pattern implies that the extensive drying predicted by off-line drought metrics, while consistent with the projected decline in surface soil moisture, will tend to overestimate (negatively) changes in total soil water availability.

Abiotic protein fragmentation by manganese oxide: Implications for a mechanism to supply soil biota with oligopeptides

DOE PAGES

Reardon, Patrick N.; Chacon, Stephany S.; Walter, Eric D.; ...

2016-03-14

Proteins facilitate a wide range of chemical transformations important in soil as well as being a major reservoir of soil nitrogen themselves. The interactions and reactions of proteins with soils and minerals are of key importance to our understanding of their functional persistence in the environment. We combined NMR and EPR spectroscopies to distinguish the reaction of a model protein with a redox active mineral surface (Birnessite, MnO 2) from its response to a redox neutral phyllosilicate (Kaolinite). Our data demonstrate that birnessite fragments the model protein while kaolinite has little impact on the protein structure. NMR and EPR spectroscopiesmore » are shown to be valuable tools to observe these reactions and capture the extent of protein transformation together with the extent of mineral response. These data suggest that mineral surfaces can have both promoting and retarding roles in terrestrial nitrogen cycling, with redox active minerals acting as accelerators by catalyzing the breakdown of proteins and proteinaceous materials while phyllosilicates are more likely to act as preservative media.« less

Crash tests of four identical high-wing single-engine airplanes

NASA Technical Reports Server (NTRS)

Vaughan, V. L., Jr.; Hayduk, R. J.

1980-01-01

Four identical four place, high wing, single engine airplane specimens with nominal masses of 1043 kg were crash tested at the Langley Impact Dynamics Research Facility under controlled free flight conditions. These tests were conducted with nominal velocities of 25 m/sec along the flight path angles, ground contact pitch angles, and roll angles. Three of the airplane specimens were crashed on a concrete surface; one was crashed on soil. Crash tests revealed that on a hard landing, the main landing gear absorbed about twice the energy for which the gear was designed but sprang back, tending to tip the airplane up to its nose. On concrete surfaces, the airplane impacted and remained in the impact attitude. On soil, the airplane flipped over on its back. The crash impact on the nose of the airplane, whether on soil or concrete, caused massive structural crushing of the forward fuselage. The liveable volume was maintained in both the hard landing and the nose down specimens but was not maintained in the roll impact and nose down on soil specimens.

Effects of Pedogenic Fe Oxides on Soil Aggregate-Associated Carbon

NASA Astrophysics Data System (ADS)

Asefaw Berhe, A.; Jin, L.

2017-12-01

Carbon sequestration is intimately related to the soil structure, mainly soil aggregate dynamics. Carbon storage in soil aggregates has been recognized as an important carbon stabilization mechanism in soils. Organic matter and pedogenic Fe oxides are major binding agents that facilitate soil aggregate formation and stability. However, few studies have investigated how different forms of pedogenic Fe oxides can affect soil carbon distribution in different aggregate-size fractions. We investigated sequentially extracted pedogenic Fe oxides (in the order of organically complexed Fe extracted with sodium pyrophosphate, poorly-crystalline Fe oxides extracted with hydroxylamine hydrochloride, and crystalline Fe oxides extracted with dithionite hydrochloride) and determined the amount and nature of C in macroaggregates (2-0.25mm), microaggregates (0.25-0.053mm), and two silt and clay fractions (0.053-0.02mm, and <0.02mm) in Musick soil from Sierra Nevada mountain in California. We also determined how pedogenic Fe oxides affect soil carbon distribution along soil depth gradients. Findings of our study revealed that the proportion of organic matter complexed Fe decreased, but the proportion of crystalline Fe increased with increasing soil depths. Poorly crystalline Fe oxides (e.g. ferrihydrite) was identified as a major Fe oxide in surface soil, whereas crystalline Fe oxides (e.g. goethite) were found in deeper soil layers. These results suggest that high concentration of organic matter in surface soil suppressed Fe crystallization. Calcium cation was closely related to the pyrophosphate extractable Fe and C, which indicates that calcium may be a major cation that contribute to the organic matter complexed Fe and C pool. Increasing concentrations of extractable Fe and C with decreasing aggregate size fractions also suggests that Fe oxides play an important role in formation and stability of silt and clay fractions, and leading to further stabilization of carbon in soil. Our findings provide mechanistic understanding of how pedogenic Fe oxides play important role in carbon stabilization in different aggregate-size fractions in soil.

Assessing soil quality indicator under different land use and soil erosion using multivariate statistical techniques.

PubMed

Nosrati, Kazem

2013-04-01

Soil degradation associated with soil erosion and land use is a critical problem in Iran and there is little or insufficient scientific information in assessing soil quality indicator. In this study, factor analysis (FA) and discriminant analysis (DA) were used to identify the most sensitive indicators of soil quality for evaluating land use and soil erosion within the Hiv catchment in Iran and subsequently compare soil quality assessment using expert opinion based on soil surface factors (SSF) form of Bureau of Land Management (BLM) method. Therefore, 19 soil physical, chemical, and biochemical properties were measured from 56 different sampling sites covering three land use/soil erosion categories (rangeland/surface erosion, orchard/surface erosion, and rangeland/stream bank erosion). FA identified four factors that explained for 82 % of the variation in soil properties. Three factors showed significant differences among the three land use/soil erosion categories. The results indicated that based upon backward-mode DA, dehydrogenase, silt, and manganese allowed more than 80 % of the samples to be correctly assigned to their land use and erosional status. Canonical scores of discriminant functions were significantly correlated to the six soil surface indices derived of BLM method. Stepwise linear regression revealed that soil surface indices: soil movement, surface litter, pedestalling, and sum of SSF were also positively related to the dehydrogenase and silt. This suggests that dehydrogenase and silt are most sensitive to land use and soil erosion.

Influence of invasive earthworm activity on carbon dynamics in soils from the Aspen Free Air CO2 Enrichment Experiment

NASA Astrophysics Data System (ADS)

Filley, T. R.; Top, S. M.; Hopkins, F. M.

2010-12-01

The influence of CO2-driven increase in net primary productivity on soil organic carbon accrual has received considerable emphasis in ecological literature with conclusions varying from positive, to neutral, to negative. What has been understudied is the coupled role of soil fauna, such as earthworms, in controlling the ultimate fate of new above and below ground plant carbon under elevated CO2. Such considerations are particularly relevant considering that in most northern North American forests earthworms are an exotic organism known to cause significant changes to forest floor chemistry and soil structure, possibly increasing nutrient loss from both soil and leaf litter and mixing litter and humus deep into the mineral soil. The impact of these exotic earthworms on overall soil carbon stabilization is largely unknown but likely a function of both species composition and edaphic soil properties. In this paper we present the initial results of a carbon isotope study (13C, 14C) conducted at the Aspen free air CO2 enrichment (FACE) site, Rhinelander, WI, USA to track allocation and redistribution within the soil of plant litter and root carbon (bulk and biopolymer). Along with litter and soil to 25 cm depth, earthworm populations were quantified, and their gut contents collected for isotopic and plant biopolymer chemistry analysis. Contributions of root vs. leaf input to soil and earthworm fecal matter were derived from differences in the chemical and isotope composition of alkaline CuO-derived lignin and substituted fatty acids (SFA) from cutin and suberin. Our investigation demonstrates the presence of invasive European earthworms, of both litter and surface soil dwelling (epigeic) and deep soil dwelling (endogeic) varieties, whose abundance increases under elevated CO2 conditions. Additionally, the different species show selective vertical movement of new and pre-FACE plant biopolymers indicating dynamics in root and leaf decomposition and burial (down to 30 cm) based upon exotic earthworm activity. The isotopic analysis also demonstrates that these invasive ecosystem engineers are bringing up “old” pre-FACE carbon to the surface, diluting the surface soil carbon isotope signature and potentially causing an apparent “slowing” of the rate of accumulation of FACE derived carbon. Our results highlight the complexity of determining soil C dynamics and the important role of invertebrate ecology in this process.

Effect of Soil Roughness on Overland Flow Connectivity at Different Slope Scenarios

NASA Astrophysics Data System (ADS)

Penuela Fernandez, A.; Javaux, M.; Bielders, C.

2013-12-01

Runoff generation, which involves the gradual depression filling and connection of overflowing depressions, is affected by surface roughness and slope. Therefore, quantifying and understanding the effects of surface roughness and slope on overland flow connectivity at the sub-grid scale can potentially improve current hydrological modeling and runoff prediction. However, little work has been conducted on quantifying these effects. This study examines the role of surface roughness on overland flow connectivity at the plot scale at different slopes. For this purpose, standard multi-Gaussian synthetic fields (6 × 6 m) with contrasting surface roughnesses, as defined by the parameters of the variogram (sill and range) of surface elevation, were used. In order to quantify the effects of soil roughness and slope on overland flow connectivity a functional connectivity indicator, so-called the Relative Surface Connection function (Antoine et al., 2009), was applied. This indicator, that represents the ratio of area connected to the outflow boundary (C) in function of the depression storage (DS), is able to capture runoff-relevant connectivity properties. Three parameters characterizing the connectivity function were used to quantify the effects of roughness and slope. These parameters are: C at DS = 0 (CDS=0), connectivity threshold (CT) and maximum depression storage (MDS). Results showed that variations on soil roughness and slope greatly affect the three parameters showing in some cases a clear relationship between structural connectivity and functional connectivity, such as between the ratio sill/range and MDS and between CDS=0 and range. This relationship, described by mathematical expressions, not only allows the quantification and comparison of the effects of soil roughness and slope in overland flow connectivity but also the prediction of these effects by the study of the variogram.

The global distribution and dynamics of surface soil moisture

NASA Astrophysics Data System (ADS)

McColl, Kaighin A.; Alemohammad, Seyed Hamed; Akbar, Ruzbeh; Konings, Alexandra G.; Yueh, Simon; Entekhabi, Dara

2017-01-01

Surface soil moisture has a direct impact on food security, human health and ecosystem function. It also plays a key role in the climate system, and the development and persistence of extreme weather events such as droughts, floods and heatwaves. However, sparse and uneven observations have made it difficult to quantify the global distribution and dynamics of surface soil moisture. Here we introduce a metric of soil moisture memory and use a full year of global observations from NASA's Soil Moisture Active Passive mission to show that surface soil moisture--a storage believed to make up less than 0.001% of the global freshwater budget by volume, and equivalent to an, on average, 8-mm thin layer of water covering all land surfaces--plays a significant role in the water cycle. Specifically, we find that surface soil moisture retains a median 14% of precipitation falling on land after three days. Furthermore, the retained fraction of the surface soil moisture storage after three days is highest over arid regions, and in regions where drainage to groundwater storage is lowest. We conclude that lower groundwater storage in these regions is due not only to lower precipitation, but also to the complex partitioning of the water cycle by the surface soil moisture storage layer at the land surface.

Soil Carbon Dioxide Production and Surface Fluxes: Subsurface Physical Controls

NASA Astrophysics Data System (ADS)

Risk, D.; Kellman, L.; Beltrami, H.

Soil respiration is a critical determinant of landscape carbon balance. Variations in soil temperature and moisture patterns are important physical processes controlling soil respiration which need to be better understood. Relationships between soil respi- ration and physical controls are typically addressed using only surface flux data but other methods also exist which permit more rigorous interpretation of soil respira- tion processes. Here we use a combination of subsurface CO_{2} concentrations, surface CO_{2} fluxes and detailed physical monitoring of the subsurface envi- ronment to examine physical controls on soil CO_{2} production at four climate observatories in Eastern Canada. Results indicate that subsurface CO_{2} produc- tion is more strongly correlated to the subsurface thermal environment than the surface CO_{2} flux. Soil moisture was also found to have an important influence on sub- surface CO_{2} production, particularly in relation to the soil moisture - soil profile diffusivity relationship. Non-diffusive profile CO_{2} transport appears to be im- portant at these sites, resulting in a de-coupling of summertime surface fluxes from subsurface processes and violating assumptions that surface CO_{2} emissions are the result solely of diffusion. These results have implications for the study of soil respiration across a broad range of terrestrial environments.

Visually assessing the level of development and soil surface stability of cyanobacterially dominated biological soil crusts

USGS Publications Warehouse

Belnap, J.; Phillips, S.L.; Witwicki, D.L.; Miller, M.E.

2008-01-01

Biological soil crusts (BSCs) are an integral part of dryland ecosystems and often included in long-term ecological monitoring programs. Estimating moss and lichen cover is fairly easy and non-destructive, but documenting cyanobacterial level of development (LOD) is more difficult. It requires sample collection for laboratory analysis, which causes soil surface disturbance. Assessing soil surface stability also requires surface disturbance. Here we present a visual technique to assess cyanobacterial LOD and soil surface stability. We define six development levels of cyanobacterially dominated soils based on soil surface darkness. We sampled chlorophyll a concentrations (the most common way of assessing cyanobacterial biomass), exopolysaccharide concentrations, and soil surface aggregate stability from representative areas of each LOD class. We found that, in the laboratory and field, LOD classes were effective at predicting chlorophyll a soil concentrations (R2=68-81%), exopolysaccharide concentrations (R2=71%), and soil aggregate stability (R2=77%). We took representative photos of these classes to construct a field guide. We then tested the ability of field crews to distinguish these classes and found this technique was highly repeatable among observers. We also discuss how to adjust this index for the different types of BSCs found in various dryland regions.

Combining Sequential Extractions and X-ray Absorption Spectroscopy for Quantitative and Qualitative Zinc Speciation in Soil

NASA Astrophysics Data System (ADS)

Bauer, Tatiana; Minkina, Tatiana; Batukaev, Abdulmalik; Nevidomskaya, Dina; Burachevskaya, Marina; Tsitsuashvili, Viktoriya; Urazgildieva, Kamilya

2017-04-01

The combined use of X-ray absorption spectrometry and extractive fractionation is an effective approach for studying the interaction of metal ions with soil compounds and identifying the phases-carriers of metals in soil and their stable fixation. These studies were carried out using the technique of X-ray absorption spectroscopy and chemical extractive fractionation. In a model experiment the samples taken in Calcic Chernozem were artificially contaminated with higher portion of Zn(NO3)2 (2000 mg/kg). The metal were incubated in soil samples for 2 year. The samples of soil mineral and organic phases (calcite, kaolinite, bentonite, humic acids) were saturated with Zn2+ from a solution of nitrate salts of metal. The total content of Zn in soil and soil various phases was determined using the X-ray fluorescence method. Extended X-ray absorption fine structure (EXAFS) Zn was measured at the Structural Materials Science beamline of the Kurchatov Center for Synchrotron Radiation. Sequential fractionation of Zn in soil conducted by Tessier method (Tessier et al., 1979) which determining 5 fractions of metals in soil: exchangeable, bound to Fe-Mn oxide, bound to carbonate, bound to the organic matter, and bound to silicate (residual). This methodology has so far more than 4000 citations (Web of Science), which demonstrates the popularity of this approach. Much Zn compounds are contained in uncontaminated soils in stable primary and secondary silicates inherited from the parental rocks (67% of the total concentrations in all fractions), which is a regional trait of soils in the fore-Caucasian plain. Extracted fractionation of metal compounds in soil samples, artificially contaminated with Zn salts, indicates the priority holding of Zn2+ ions by silicates, carbonates and Fe-Mn oxides. The Zn content significantly increases in the exchangeable fraction. Atomic structure study of the soil various phases saturated with Zn2+ ion by using (XANES) X-ray absorption spectroscopy allowed the determination of mechanism of metal ions interaction with soil phases and the resulting types of chemical bonds. Interaction with soil components modifies the electron structure of the metal ions themselves. The soil contamination with Zn is accompanied by decreasing the stable connection between metal and soil components. Interacting with humic acids in chernozem, the Zn2+ ion is coordinated by functional groups and ligands and forms unstable outer-sphere complexes. Zinc included into octahedral structures of layered minerals and hydro(oxides) can be inner-and outer-sphere adsorbed. The Zn2+ ions enable to replace Ca2+ ions in octahedral positions being coordinated with carbonate ions as ligands, thus forming absorbed complexes at the surface of mineral calcite. This work was supported by grant of the Russian Scientific Foundation № 16-14-10217.

Velocity of water flow along saturated loess slopes under erosion effects

NASA Astrophysics Data System (ADS)

Huang, Yuhan; Chen, Xiaoyan; Li, Fahu; Zhang, Jing; Lei, Tingwu; Li, Juan; Chen, Ping; Wang, Xuefeng

2018-06-01

Rainfall or snow-melted water recharge easily saturates loose top soils with a less permeable underlayer, such as cultivated soil slope and partially thawed top soil layer, and thus, may influence the velocity of water flow. This study suggested a methodology and device system to supply water from the bottom soil layer at the different locations of slopes. Water seeps into and saturates the soil, when the water level is controlled at the same height of the soil surface. The structures and functions of the device, the components, and the operational principles are described in detail. A series of laboratory experiments were conducted under slope gradients of 5°, 10°, 15°, and 20° and flow rates of 2, 4, and 8 L min-1 to measure the water flow velocities over eroding and non-eroded loess soil slopes, under saturated conditions by using electrolyte tracing. Results showed that flow velocities on saturated slopes were 17% to 88% greater than those on non-saturated slopes. Flow velocity increased rapidly under high flow rates and slope gradients. Saturation conditions were suitable in maintaining smooth rill geomorphology and causing fast water flow. The saturated soil slope had a lubricant effect on the soil surface to reduce the frictional force, resulting in high flow velocity. The flow velocities of eroding rills under different slope gradients and flow rates were approximately 14% to 33% lower than those of non-eroded rills on saturated loess slopes. Compared with that on a saturated loess slope, the eroding rill on a non-saturated loess slope can produce headcuts to reduce the flow velocity. This study helps understand the hydrodynamics of soil erosion and sediment transportation of saturated soil slopes.

Petroleum Contamination and Plant Identity Influence Soil and Root Microbial Communities While AMF Spores Retrieved from the Same Plants Possess Markedly Different Communities

PubMed Central

Iffis, Bachir; St-Arnaud, Marc; Hijri, Mohamed

2017-01-01

Phytoremediation is a promising in situ green technology based on the use of plants to cleanup soils from organic and inorganic pollutants. Microbes, particularly bacteria and fungi, that closely interact with plant roots play key roles in phytoremediation processes. In polluted soils, the root-associated microbes contribute to alleviation of plant stress, improve nutrient uptake and may either degrade or sequester a large range of soil pollutants. Therefore, improving the efficiency of phytoremediation requires a thorough knowledge of the microbial diversity living in the rhizosphere and in close association with plant roots in both the surface and the endosphere. This study aims to assess fungal ITS and bacterial 16S rRNA gene diversity using high-throughput sequencing in rhizospheric soils and roots of three plant species (Solidago canadensis, Populus balsamifera, and Lycopus europaeus) growing spontaneously in three petroleum hydrocarbon polluted sedimentation basins. Microbial community structures of rhizospheric soils and roots were compared with those of microbes associated with arbuscular mycorrhizal fungal (AMF) spores to determine the links between the root and rhizosphere communities and those associated with AMF. Our results showed a difference in OTU richness and community structure composition between soils and roots for both bacteria and fungi. We found that petroleum hydrocarbon pollutant (PHP) concentrations have a significant effect on fungal and bacterial community structures in both soils and roots, whereas plant species identity showed a significant effect only on the roots for bacteria and fungi. Our results also showed that the community composition of bacteria and fungi in soil and roots varied from those associated with AMF spores harvested from the same plants. This let us to speculate that in petroleum hydrocarbon contaminated soils, AMF may release chemical compounds by which they recruit beneficial microbes to tolerate or degrade the PHPs present in the soil. PMID:28848583

Petroleum Contamination and Plant Identity Influence Soil and Root Microbial Communities While AMF Spores Retrieved from the Same Plants Possess Markedly Different Communities.

PubMed

Iffis, Bachir; St-Arnaud, Marc; Hijri, Mohamed

2017-01-01

Phytoremediation is a promising in situ green technology based on the use of plants to cleanup soils from organic and inorganic pollutants. Microbes, particularly bacteria and fungi, that closely interact with plant roots play key roles in phytoremediation processes. In polluted soils, the root-associated microbes contribute to alleviation of plant stress, improve nutrient uptake and may either degrade or sequester a large range of soil pollutants. Therefore, improving the efficiency of phytoremediation requires a thorough knowledge of the microbial diversity living in the rhizosphere and in close association with plant roots in both the surface and the endosphere. This study aims to assess fungal ITS and bacterial 16S rRNA gene diversity using high-throughput sequencing in rhizospheric soils and roots of three plant species ( Solidago canadensis, Populus balsamifera , and Lycopus europaeus ) growing spontaneously in three petroleum hydrocarbon polluted sedimentation basins. Microbial community structures of rhizospheric soils and roots were compared with those of microbes associated with arbuscular mycorrhizal fungal (AMF) spores to determine the links between the root and rhizosphere communities and those associated with AMF. Our results showed a difference in OTU richness and community structure composition between soils and roots for both bacteria and fungi. We found that petroleum hydrocarbon pollutant (PHP) concentrations have a significant effect on fungal and bacterial community structures in both soils and roots, whereas plant species identity showed a significant effect only on the roots for bacteria and fungi. Our results also showed that the community composition of bacteria and fungi in soil and roots varied from those associated with AMF spores harvested from the same plants. This let us to speculate that in petroleum hydrocarbon contaminated soils, AMF may release chemical compounds by which they recruit beneficial microbes to tolerate or degrade the PHPs present in the soil.

30 CFR 715.16 - Topsoil handling.

Code of Federal Regulations, 2010 CFR

2010-07-01

... as the surface soil layers. Where the A horizon is less than 6 inches, a 6-inch layer that includes... replaced as the surface soil layer. (3) Where necessary to obtain soil productivity consistent with... amounts and analyses as determined by soil tests shall be applied to the surface soil layer so that it...

30 CFR 715.16 - Topsoil handling.

Code of Federal Regulations, 2011 CFR

2011-07-01

... as the surface soil layers. Where the A horizon is less than 6 inches, a 6-inch layer that includes... replaced as the surface soil layer. (3) Where necessary to obtain soil productivity consistent with... amounts and analyses as determined by soil tests shall be applied to the surface soil layer so that it...

30 CFR 715.16 - Topsoil handling.

Code of Federal Regulations, 2014 CFR

2014-07-01

... as the surface soil layers. Where the A horizon is less than 6 inches, a 6-inch layer that includes... replaced as the surface soil layer. (3) Where necessary to obtain soil productivity consistent with... amounts and analyses as determined by soil tests shall be applied to the surface soil layer so that it...

30 CFR 715.16 - Topsoil handling.

Code of Federal Regulations, 2012 CFR

2012-07-01

... as the surface soil layers. Where the A horizon is less than 6 inches, a 6-inch layer that includes... replaced as the surface soil layer. (3) Where necessary to obtain soil productivity consistent with... amounts and analyses as determined by soil tests shall be applied to the surface soil layer so that it...

30 CFR 715.16 - Topsoil handling.

Code of Federal Regulations, 2013 CFR

2013-07-01

... as the surface soil layers. Where the A horizon is less than 6 inches, a 6-inch layer that includes... replaced as the surface soil layer. (3) Where necessary to obtain soil productivity consistent with... amounts and analyses as determined by soil tests shall be applied to the surface soil layer so that it...

Density functional theory study of phase stability and defect thermodynamics in iron-oxyhydroxide mineral materials

NASA Astrophysics Data System (ADS)

Pinney, Nathan Douglas

Due to their high surface area and reactivity toward a variety of heavy metal and oxyanion species of environmental concern, Fe-(oxyhydr)oxide materials play an important role in the geochemical fate of natural and anthropogenic contaminants in soils, aquifers and surface water environments worldwide. In this research, ab initio simulations describe the bulk structure, magnetic properties, and relative phase stability of major Fe-(oxyhydr)oxide materials, including hematite, goethite, lepidocrocite, and ferrihydrite.These bulk models are employed in further studies of point defect and alloy/dopant thermodynamics in these materials, allowing construction of a phase stability model that better replicates the structure and composition of real materials. Li + adsorption at the predominant goethite (101) surface is simulated using ab initio methods, offering energetic and structural insight into the binding mechanisms of metal cations over a range of surface protonation conditions.

Designing sustainable soils in Earth's critical zone

NASA Astrophysics Data System (ADS)

Banwart, Steven Allan; de Souza, Danielle Maia; Menon, Manoj; Nikolaidis, Nikolaos; Panagos, Panos; Vala Ragnardsdottir, Kristin; Rousseva, Svelta; van Gaans, Pauline

2014-05-01

The demographic drivers of increasing human population and wealth are creating tremendous environmental pressures from growing intensity of land use, resulting in soil and land degradation worldwide. Environmental services are provided through multiple soil functions that include biomass production, water storage and transmission, nutrient transformations, contaminant attenuation, carbon and nitrogen storage, providing habitat and maintaining the genetic diversity of the land environment. One of the greatest challenges of the 21st century is to identify key risks to soil, and to design mitigation strategies to manage these risks and to enhance soil functions that can last into the future. The scientific study of Earth's Critical Zone (CZ), the thin surface layer that extends vertically from the top of the tree canopy to the bottom of aquifers, provides an essential integrating scientific framework to study, protect and enhance soil functions. The research hypothesis is that soil structure, the geometric architecture of solids, pores and biomass, is a critical indicator and essential factor of productive soil functions. The experimental design selects a network of Critical Zone Observatories (CZOs) as advanced field research sites along a gradient of land use intensity in order to quantify soil structure and soil processes that dictate the flows and transformations of material and energy as soil functions. The CZOs focus multidisciplinary expertise on soil processes, field observation and data interpretation, management science and ecological economics. Computational simulation of biophysical processes provides a quantitative method of integration for the range of theory and observations that are required to quantify the linkages between changes in soil structure and soil functions. Key results demonstrate that changes in soil structure can be quantified through the inputs of organic carbon and nitrogen from plant productivity and microbial activity, coupled with particle aggregation dynamics and organic matter mineralization. Simulation results show that soil structure is highly dynamic and is sensitive to organic matter production and minearlisation rates as influenced by vegetation, tillage and organic carbon amendments. These results point to a step-change in the capability to design soil management and land use through computational simulation. This approach of "sustainability by design" describes the mechanistic process linkages that exist between the above-ground inputs to the CZ and the internal processes that produce soil functions. This approach provides a rational, scientific approach to selecting points of intervention with the CZ in order to design methods to mitigate soil threats and to enhance and sustain vital soil functions. Furthermore, this approach provides a successful pilot study to the use of international networks of CZOs as a planetary-scale laboratory to test the response of CZ process rates along gradients of global environmental change - and to test adaptation strategies to manage the risks arising from the CZ impacts. Acknowledgements. The authors acknowledge the substantial contributions of the entire team of investigators and funding of the SoilTrEC project (EC FP7, agreement no. 244118; www.soiltrec.eu).

[Effect of irregular bedrock topography on the soil profile pattern of water content in a Karst hillslope.

PubMed

Jia, Jin Tian; Fu, Zhi Yong; Chen, Hong Song; Wang, Ke Lin; Zhou, Wei Jun

2016-06-01

Based on three manually excavated trenches (projection length of 21 m, width of 1 m) along a typical Karst hillslope, the changing trends for soil-bedrock structure, average water content of soil profile and soil-bedrock interface water content along each individual trench were studied. The effect of irregular bedrock topography on soil moisture distribution was discussed. The results showed that the surface topography was inconsistent with the bedrock topography in the Karst hill-slopes. The bedrock topography was highly irregular with a maximum variation coefficient of 82%. The distribution pattern of soil profile of moisture was significantly affected by the underlying undulant bedrock. The soil water content was related to slope position when the fluctuation was gentle, and displayed a linear increase from upslope to downslope. When the bedrock fluctuation increased, the downslope linear increasing trend for soil water content became unapparent, and the spatial continuity of soil moisture was weakened. The soil moisture was converged in rock dents and cracks. The average water content of soil profile was significantly positively correlated with the soil-bedrock interface water content, while the latter responded more sensitively to the bedrock fluctuation.

Sensitivity of Land Surface Parameters on Thunderstorm Simulation through HRLDAS-WRF Coupling Mode

NASA Astrophysics Data System (ADS)

Kumar, Dinesh; Kumar, Krishan; Mohanty, U. C.; Kisore Osuri, Krishna

2016-07-01

Land surface characteristics play an important role in large scale, regional and mesoscale atmospheric process. Representation of land surface characteristics can be improved through coupling of mesoscale atmospheric models with land surface models. Mesoscale atmospheric models depend on Land Surface Models (LSM) to provide land surface variables such as fluxes of heat, moisture, and momentum for lower boundary layer evolution. Studies have shown that land surface properties such as soil moisture, soil temperature, soil roughness, vegetation cover, have considerable effect on lower boundary layer. Although, the necessity to initialize soil moisture accurately in NWP models is widely acknowledged, monitoring soil moisture at regional and global scale is a very tough task due to high spatial and temporal variability. As a result, the available observation network is unable to provide the required spatial and temporal data for the most part of the globe. Therefore, model for land surface initializations rely on updated land surface properties from LSM. The solution for NWP land-state initialization can be found by combining data assimilation techniques, satellite-derived soil data, and land surface models. Further, it requires an intermediate step to use observed rainfall, satellite derived surface insolation, and meteorological analyses to run an uncoupled (offline) integration of LSM, so that the evolution of modeled soil moisture can be forced by observed forcing conditions. Therefore, for accurate land-state initialization, high resolution land data assimilation system (HRLDAS) is used to provide the essential land surface parameters. Offline-coupling of HRLDAS-WRF has shown much improved results over Delhi, India for four thunder storm events. The evolution of land surface variables particularly soil moisture, soil temperature and surface fluxes have provided more realistic condition. Results have shown that most of domain part became wetter and warmer after assimilation of soil moisture and soil temperature at the initial condition which helped to improve the exchange fluxes at lower atmospheric level. Mixing ratio were increased along with elevated theta-e at lower level giving a signature of improvement in LDAS experiment leading to a suitable condition for convection. In the analysis, moisture convergence, mixing ratio and vertical velocities have improved significantly in terms of intensity and time lag. Surface variables like soil moisture, soil temperature, sensible heat flux and latent heat flux have progressed in a possible realistic pattern. Above discussion suggests that assimilation of soil moisture and soil temperature improves the overall simulations significantly.

Surface features of soil particles of three types of soils under different land use strategies

NASA Astrophysics Data System (ADS)

Matveeva, Nataliy; Kotelnikova, Anna; Rogova, Olga; Proskurnin, Mikhail

2017-04-01

Nowadays, there is a clear need in a deep investigation of molecular composition of soils and of its influence on surface characteristics of soil particles. The aim of this study is to evaluate the composition and properties of physical fractions in different soil types in determining functional specificity of soil solid-phase surface. The experiments were carried out with three different types of Russian soils—Sod-Podzolic, Chestnut, and Chernozem soils—under various treatments (fallow, different doses of mineral fertilizers and their aftereffects). The samples were separated into three fractions: silt (SF) with a particle size of <2 μm, light fraction (LF) with a density of <2 g/cm3, and residual fraction (RF) with a size >2 μm and the density >2 g/cm3. We measured specific surface area, surface hydrophobicity (contact angle, CA), ζ-potential, and the point of zero charge (PZC). For Chernozem and Chestnut soils and their fractions of we observed an increase in hydrophobicity for SF and RF under fertilizer treatment. At the sites not treated with fertilizers and aftereffect sites, the hydrophobicity of fractions was lower compared to the sites under treatment. The CA of the original soils and fractions were different: in 35% of cases CA was higher for SF and RF by 12-16%. The rest of samples demonstrated CA of all three physical fractions lower than CA of the original soil. The variability of the mean CA indicates considerable differences in ζ-potential and PZC between different types of soils and soil fractions. The results of potentiometric titration of PZC for Sod-Podzolic soil showed that all values are in acidic range, which suggests predominance of acidic functional groups at the surface of soil particles. Specific surface area determines soil sorption processes, bioavailability of nutrients, water etc. Here, specific surface area of Sod-Podzolic soil was low and SF-dependent. We calculated specific surface charge from obtained data on specific surface area and PZC. The results suggested considerable differences between sorption features of both soils and fractions under different land use strategies.

Fundamental considerations of water repellancy in soil, and related effects on other natural and man-made materials

NASA Astrophysics Data System (ADS)

Matthews, G. Peter

2010-05-01

This presentation will concern the understanding of soil water repellancy and wettability at a fundamental level, and the difficulties of relating the very small, micron scale at which the repellancy and wettability characteristics are produced to the much larger, field scale at which they are normally observed. The presentation will not be a review of past work, but rather will concentrate on recent publications, publications in press, and speculative considerations which may lead to future work in this area. There are three fundamental components of water repellancy - the nature of the soil surfaces themselves, the effect of organic matter and microbiologically produced substances, and the topology of the resultant surfaces. The effects of hydrophobic surfaces will be illustrated by a consideration of the wettability of substances such as commercially produced talc grades. The faces of these platey mineral particles are hydrophobic, whereas their edges are hydrophilic, and the combination not only causes water repellency in itself, but also causes unusual adsorption effects from aqueous solution. The effect of organic matter on soil wettability has been widely studied, often by core-scale wettability experiments. It will be shown how a consideration of micro-wetting effects has led to a more robust data analysis method for such studies (Matthews, G. P. et al, European J.Soil Sci., 2008). Traditionally wetting fronts are assumed to advance in proportion to the square root of time (as predicted by the Washburn equation), but micro-modelling shows that, once inertial effects are taken into account, low-volume fingers of wetting fluid track through porous substances in advance of the observed Washburn wetting front (Bodurtha, P. et al, J.Colloid Interface Sci., 2005). The effects of micro-topology are also well known (Ridgway, C. J. et al, J.Colloid Interface Sci., 2001), but need to be integrated and upscaled, as described below. Soil water repellency is not only dependant on the soil mineral characteristics, surface topology and organic matter content, but is also influenced by microbiological activity. The production of hydrophobic microbial biomass and exudates alter the hydrological characteristics of soil (Chan, K. Y., Soil Sci.Soc.Am.J., 1992) and strengthen the bonds between soil particles. Amongst these are extracellular polymeric substances (EPS), which are produced as a result of microbial activity and increase during periods of substrate utilisation and microbial growth (Hallett, P. D. et al, European J.Soil Sci., 1999). They form part of a wide spectrum of soil organic species, many produced by the soil's bacterial and fungal biomass. EPS provides a living protective membrane between changing hydrological conditions and the micro-organisms. It comprises polysaccharides and smaller amounts of protein, lipids and humic substances, with masses ranging from 103 to 108 kDaltons (Allison, D. G. et al, Fems Microbiology Letters, 1998). The small amounts of EPS in soil have a disproportionately large effect on soil hydraulic properties, and the response of EPS to major perturbations, such as wetting and drying cycles, has recently been well characterised (Or, D. et al, Vadose Zone J, 2007). Therefore, as will be described, the use of EPS as an analogue to the wider range of organic species can lead to an understanding of climatic effects on soil wettability. The upscaling of the effects from micron to field scale requires a highly detailed modelling approach, using a dual -porous void structure model (a modification of the previous ‘Pore-Cor' model) which takes into account both the soil micro-matrix and the macroscopic percolation and wetting pathways (Laudone, G. M. et al, European J.Soil Sci., submitted). Super-hydrophobicity in natural materials (the ‘lotus' effect) and man-made materials (micro-structured arrays) will also be explained and illustrated, and the condition under which super-hydrophobicity can flip to super-wettability. Super-hydrophobicity gives an unusual insight into the less extreme examples of water repellancy found in many soils.

Characterization of the humic substances isolated from postfire soils of scotch pine forest in Togljatty city, Samara region by the 13C-NMR spectroscopy

NASA Astrophysics Data System (ADS)

Maksimova, Ekaterina; Abakumov, Evgeny

2016-04-01

Postpyrogenic soil dynamics is an informative tool for studying of soil elementary processes in extreme temperature conditions and for predicting of short time environmental changes in conditions of catastrophic landscape changes. Soil organic matter (SOM) system evolution is the most rapid process of postpyrogenic soil development. In this relation the evaluation of humus accumulation rates and humification trend were conducted with use of the classical chemical and modern spectroscopy methods. Soil restoration after spontaneous forest fires near Togljatty city (Samara region, Russia) was abandoned in 2010, and further monitoring over the next four years was organized to evaluate the speed of biogenic processes and humus accumulation dynamics. Three key soil plots were studied for estimating SOM quality changes under the forest fire effect: surface forest fire, crown forest fire and control. Total carbon and nitrogen content as well as Cha/Cfa ratios (content of humic acids/ content of fulvic acids), were estimated to assess the dynamics of soil restoration. Humic acid powders were extracted and analyzed by elemental composition and 13C-NMR spectroscopy to assess changes in humic substance structure and composition. The data obtained indicate that burning of a forest floor and sod (humic) horizon led to humus losses and decreases in total carbon stocks. As a result of the fires, the content of humic acids in the pyrogenic horizon increased, leading alterations of humus type. Greater increases in the degree of organic matter humification were observed for surface fires than crown fires. It was shown that the humus molecular composition was substantially affected by the wildfires. The data show an increase in aromaticity, a loss of oxygen-containing groups and dehydrogenation of humic acids. Humic acids in the soils of the control plots and after wildfires were significantly different, especially in the ratios of hydrogen, oxygen and carbon. The increase in the degree of humic acid aromatization was confirmed by the hydrogen/carbon ratio. Investigation of the humic acids' molecular structure by 13C-NMR showed a relative increase in aromatic compounds and decrease in aliphatic ones. In general, crown and surface fires plots are not very different in terms of 13C-NMR spectra of humic acids, however humic acids of control plot have essential differences from pyrogenic ones. This study was a contribution to the Russian foundation for basic research, project for young scientists No.14-04-32132 and 15-34-20844.

Representing the effects of alpine grassland vegetation cover on the simulation of soil thermal dynamics by ecosystem models applied to the Qinghai-Tibetan Plateau

USGS Publications Warehouse

Yi, S.; Li, N.; Xiang, B.; Wang, X.; Ye, B.; McGuire, A.D.

2013-01-01

Soil surface temperature is a critical boundary condition for the simulation of soil temperature by environmental models. It is influenced by atmospheric and soil conditions and by vegetation cover. In sophisticated land surface models, it is simulated iteratively by solving surface energy budget equations. In ecosystem, permafrost, and hydrology models, the consideration of soil surface temperature is generally simple. In this study, we developed a methodology for representing the effects of vegetation cover and atmospheric factors on the estimation of soil surface temperature for alpine grassland ecosystems on the Qinghai-Tibetan Plateau. Our approach integrated measurements from meteorological stations with simulations from a sophisticated land surface model to develop an equation set for estimating soil surface temperature. After implementing this equation set into an ecosystem model and evaluating the performance of the ecosystem model in simulating soil temperature at different depths in the soil profile, we applied the model to simulate interactions among vegetation cover, freeze-thaw cycles, and soil erosion to demonstrate potential applications made possible through the implementation of the methodology developed in this study. Results showed that (1) to properly estimate daily soil surface temperature, algorithms should use air temperature, downward solar radiation, and vegetation cover as independent variables; (2) the equation set developed in this study performed better than soil surface temperature algorithms used in other models; and (3) the ecosystem model performed well in simulating soil temperature throughout the soil profile using the equation set developed in this study. Our application of the model indicates that the representation in ecosystem models of the effects of vegetation cover on the simulation of soil thermal dynamics has the potential to substantially improve our understanding of the vulnerability of alpine grassland ecosystems to changes in climate and grazing regimes.

Scaling methane oxidation: From laboratory incubation experiments to landfill cover field conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abichou, Tarek, E-mail: abichou@eng.fsu.edu; Mahieu, Koenraad; Chanton, Jeff

2011-05-15

Evaluating field-scale methane oxidation in landfill cover soils using numerical models is gaining interest in the solid waste industry as research has made it clear that methane oxidation in the field is a complex function of climatic conditions, soil type, cover design, and incoming flux of landfill gas from the waste mass. Numerical models can account for these parameters as they change with time and space under field conditions. In this study, we developed temperature, and water content correction factors for methane oxidation parameters. We also introduced a possible correction to account for the different soil structure under field conditions.more » These parameters were defined in laboratory incubation experiments performed on homogenized soil specimens and were used to predict the actual methane oxidation rates to be expected under field conditions. Water content and temperature corrections factors were obtained for the methane oxidation rate parameter to be used when modeling methane oxidation in the field. To predict in situ measured rates of methane with the model it was necessary to set the half saturation constant of methane and oxygen, K{sub m}, to 5%, approximately five times larger than laboratory measured values. We hypothesize that this discrepancy reflects differences in soil structure between homogenized soil conditions in the lab and actual aggregated soil structure in the field. When all of these correction factors were re-introduced into the oxidation module of our model, it was able to reproduce surface emissions (as measured by static flux chambers) and percent oxidation (as measured by stable isotope techniques) within the range measured in the field.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schostag, Morten; Stibal, Marek; Jacobsen, Carsten S.

The active layer of soil overlaying permafrost in the Arctic is subjected to dramatic annual changes in temperature and soil chemistry, which likely affect bacterial activity and community structure. We studied seasonal variations in the bacterial community of active layer soil from Svalbard (78°N) by co-extracting DNA and RNA from 12 soil cores collected monthly over a year. PCR amplicons of 16S rRNA genes (DNA) and reverse transcribed transcripts (cDNA) were quantified and sequenced to test for the effect of low winter temperature and seasonal variation in concentration of easily degradable organic matter on the bacterial communities. The copy numbermore » of 16S rRNA genes and transcripts revealed no distinct seasonal changes indicating potential bacterial activity during winter despite soil temperatures well below -10°C. Multivariate statistical analysis of the bacterial diversity data (DNA and cDNA libraries) revealed a season-based clustering of the samples, and, e.g., the relative abundance of potentially active Cyanobacteria peaked in June and Alphaproteobacteria increased over the summer and then declined from October to November. The structure of the bulk (DNA-based) community was significantly correlated with pH and dissolved organic carbon, while the potentially active (RNA-based) community structure was not significantly correlated with any of the measured soil parameters. A large fraction of the 16S rRNA transcripts was assigned to nitrogen-fixing bacteria (up to 24% in June) and phototrophic organisms (up to 48% in June) illustrating the potential importance of nitrogen fixation in otherwise nitrogen poor Arctic ecosystems and of phototrophic bacterial activity on the soil surface.« less

Quantifying the effects of wildfire on changes in soil properties by surface burning of soils from the Boulder Creek Critical Zone Observatory

USGS Publications Warehouse

Wieting, Celeste; Ebel, Brian A.; Singha, Kamini

2017-01-01

Study regionThis study used intact soil cores collected at the Boulder Creek Critical Zone Observatory near Boulder, Colorado, USA to explore fire impacts on soil properties.Study focusThree soil scenarios were considered: unburned control soils, and low- and high-temperature burned soils. We explored simulated fire impacts on field-saturated hydraulic conductivity, dry bulk density, total organic carbon, and infiltration processes during rainfall simulations.New hydrological insights for the regionSoils burned to high temperatures became more homogeneous with depth with respect to total organic carbon and bulk density, suggesting reductions in near-surface porosity. Organic matter decreased significantly with increasing soil temperature. Tension infiltration experiments suggested a decrease in infiltration rates from unburned to low-temperature burned soils, and an increase in infiltration rates in high-temperature burned soils. Non-parametric statistical tests showed that field-saturated hydraulic conductivity similarly decreased from unburned to low-temperature burned soils, and then increased with high-temperature burned soils. We interpret these changes result from the combustion of surface and near-surface organic materials, enabling water to infiltrate directly into soil instead of being stored in the litter and duff layer at the surface. Together, these results indicate that fire-induced changes in soil properties from low temperatures were not as drastic as high temperatures, but that reductions in surface soil water repellency in high temperatures may increase infiltration relative to low temperatures.

Effect of periodic fluctuation of soil particle rotation resistance on interface shear behaviour

NASA Astrophysics Data System (ADS)

Ebrahimian, Babak; Noorzad, Asadollah

2010-06-01

The interface behaviour between infinite extended narrow granular layer and bounding structure is numerically investigated using finite element method. The micro-polar (Cosserat) continuum approach within the framework of elasto-plasticity is employed to remove the numerical difficulties caused by strain-softening of materials in classical continuum mechanics. Mechanical properties of cohesionless granular soil are described with Lade's model enhanced with polar terms including Cosserat rotations, curvatures and couple stresses via mean grain diameter as the internal length. The main attention of paper is laid on the influence of spatial periodic fluctuation of rotation resistance of soil particles interlocked with the surface of bounding structure on evolution and location of shear band developed inside granular body. The finite element results demonstrate that the location and evolution of shear localization in granular body is strongly affected by prescribed non-uniform micro-polar kinematic boundary conditions along the interface.

Potential of EnMAP spaceborne imaging spectroscopy for the prediction of common surface soil properties and expected accuracy

NASA Astrophysics Data System (ADS)

Chabrillat, Sabine; Foerster, Saskia; Steinberg, Andreas; Stevens, Antoine; Segl, Karl

2016-04-01

There is a renewed awareness of the finite nature of the world's soil resources, growing concern about soil security, and significant uncertainties about the carrying capacity of the planet. As a consequence, soil scientists are being challenged to provide regular assessments of soil conditions from local through to global scales. However, only a few countries have the necessary survey and monitoring programs to meet these new needs and existing global data sets are out-of-date. A particular issue is the clear demand for a new area-wide regional to global coverage with accurate, up-to-date, and spatially referenced soil information as expressed by the modeling scientific community, farmers and land users, and policy and decision makers. Soil spectroscopy from remote sensing observations based on studies from the laboratory scale to the airborne scale has been shown to be a proven method for the quantitative prediction of key soil surface properties in local areas for exposed soils in appropriate surface conditions such as low vegetation cover and low water content. With the upcoming launch of the next generation of hyperspectral satellite sensors in the next 3 to 5 years (EnMAP, HISUI, PRISMA, SHALOM), a great potential for the global mapping and monitoring of soil properties is appearing. Nevertheless, the capabilities to extend the soil properties current spectral modeling from local to regional scales are still to be demonstrated using robust methods. In particular, three central questions are at the forefront of research nowadays: a) methodological developments toward improved algorithms and operational tools for the extraction of soil properties, b) up scaling from the laboratory into space domain, and c) demonstration of the potential of upcoming satellite systems and expected accuracy of soil maps. In this study, airborne imaging spectroscopy data from several test sites are used to simulate EnMAP satellite images at 30 m scale. Then, different soil algorithms are examined based on the analyses of chemical-physical features from the soil spectral reflectance and/or multivariate established techniques such as Partial-Least Squares PLS, Support-Vector Machine SVM, to determine common surface soil properties, in particular soil organic carbon (SOC), clay and iron oxide content. Results show that EnMAP is able to predict clay, free iron oxide, and SOC with an RV2 between 0.53 and 0.67 compared to airborne imagery with RV2 between 0.64 and 0.74. The correlation between EnMAP and airborne imagery prediction results is high (Pearson coefficients between 0.84 and 0.91). Furthermore, spatial distribution is coherent between the airborne mapping and simulated EnMAP mapping as shown with a spatial structure analysis. In general, this paper demonstrates the high potential of upcoming spaceborne hyperspectral missions for soil science studies but also shows the need for future adapted strategies to fulfill the entire potential of soil spectroscopy for orbital utilization.

Physical parameters of Fluvisols on flooded and non-flooded terraces

NASA Astrophysics Data System (ADS)

Kercheva, Milena; Sokołowska, Zofia; Hajnos, Mieczysław; Skic, Kamil; Shishkov, Toma

2017-01-01

The heterogeneity of soil physical properties of Fluvisols, lack of large pristine areas, and different moisture regimes on non-flooded and flooded terraces impede the possibility to find a soil profile which can serve as a baseline for estimating the impact of natural or anthropogenic factors on soil evolution. The aim of this study is to compare the pore size distribution of pristine Fluvisols on flooded and non-flooded terraces using the method of the soil water retention curve, mercury intrusion porosimetry, nitrogen adsorption isotherms, and water vapour sorption. The pore size distribution of humic horizons of pristine Fluvisols on the non-flooded terrace differs from pore size distribution of Fluvisols on the flooded terrace. The peaks of textural and structural pores are higher in the humic horizons under more humid conditions. The structural characteristics of subsoil horizons depend on soil texture and evolution stage. The peaks of textural pores at about 1 mm diminish with lowering of the soil organic content. Structureless horizons are characterized by uni-modal pore size distribution. Although the content of structural pores of the subsoil horizons of Fluvisols on the non-flooded terrace is low, these pores are represented by biopores, as the coefficient of filtration is moderately high. The difference between non-flooded and flooded profiles is well expressed by the available water storage, volume and mean radius of pores, obtained by mercury intrusion porosimetry and water desorption, which are higher in the surface horizons of frequently flooded Fluvisols.

Uncertainty in Arctic hydrology projections and the permafrost-carbon feedback

NASA Astrophysics Data System (ADS)

Andresen, C. G.; Lawrence, D. M.; Wilson, C. J.; McGuire, D.

2017-12-01

Projected warming is expected to thaw permafrost soils and deepen the permafrost active layer. These changes will affect surface hydrological conditions. Since the soil hydrologic state exerts a strong influence on the rate and pathway of soil organic matter decomposition into CO2 or CH4, there is a strong need to examine and better understand model projections of hydrologic change and how differences in process representation affect projections of wetting and/or drying of changing permafrost landscapes. This study aims to advance understanding of where, when and why arctic will become wetter or drier. We assessed simulations from 8 "permafrost enabled" land models that were run in offline mode from 1960 to 2299 forced with the same projected climate for a high-emissions scenario. Climate models project increased precipitation (P) across most of the Arctic domain and the land models indicate that runoff and evapotranspiration (ET) will also both increase. In general, the water input to the soil (P-ET) also increases, but the models project a contradicting long-term drying of the surface soil. The surface drying in the models can generally be explained by filtration of moisture to deeper soil layers as the active layer deepens or by increased sub-surface drainage where permafrost in a grid cell thaws completely. Though, there is a qualitative agreement in this type of response across the models, the projections vary dramatically in magnitude. Variability among simulations is largely attributed to parameterization and structural differences across the participating models, particularly the diverse representations of evapotranspiration, water table and soil water storage and transmission. A limited set of results from single forcing experiments suggests that the warming effect in the sensitivity analysis was the principal driver of soil drying while CO2 and precipitation effects had a small wetting influence. When compared to observational data, simulations tend to underestimate discharge by a factor of 2 for the major arctic river basins. This analysis serves as a baseline to identify key process representation gaps and opportunities to improve representation of permafrost hydrology and associated projections of carbon and energy feedbacks in land models.

Infiltration and soil erosion modelling on Lausatian post mine sites

NASA Astrophysics Data System (ADS)

Kunth, Franziska; Schmidt, Jürgen

2013-04-01

Land management of reclaimed lignite mine sites requires long-term and safe structuring of recultivation areas. Erosion by water leads to explicit soil losses, especially on heavily endangered water repellent and non-vegetated soil surfaces. Beyond that, weathering of pyrite-containing lignite burden dumps causes sulfuric acid-formation, and hence the acidification of groundwater, seepage water and surface waters. Pyrite containing sediment is detached by precipitation and transported into worked-out open cuts by draining runoff. In addition to ground water influence, erosion processes are therefore involved in acidification of surface waters. A model-based approach for the conservation of man-made slopes of post mining sites is the objective of this ongoing study. The study shall be completed by modeling of the effectiveness of different mine site recultivation scenarios. Erosion risks on man-made slopes in recultivation areas should be determined by applying the physical, raster- and event based computer model EROSION 2D/3D (Schmidt, 1991, 1992; v. Werner, 1995). The widely used erosion model is able to predict runoff as well as detachment, transport and deposition of sediments. Lignite burden dumps contain hydrophobic substances that cover soil particles. Consequently, these soils show strong water repellency, which influences the processes of infiltration and soil erosion on non-vegetated, coal containing dump soils. The influence of water repellency had to be implemented into EROSION 2D/3D. Required input data for soil erosion modelling (e.g. physical soil parameters, infiltration rates, calibration factors, etc.) were gained by soil sampling and rainfall experiments on non-vegetated as well as recultivated reclaimed mine sites in the Lusatia lignite mining region (southeast of Berlin, Germany). The measured infiltration rates on the non-vegetated water repellent sites were extremely low. Therefore, a newly developed water repellency-factor was applied to depict infiltration and erosion processes on water repellent dump soils. For infiltration modelling with EROSION 2D calibration factors (e.g. water repellency factor, skin-factor, etc.) were determined in different steps by calibrating computer modelled infiltration, respectively volume rate of flow to the measured data.

The Role of Management in Enrichment Ratio Dynamics and Resilience of Aggregate Fractions Via Raindrop Impact within Agricultural Hillslopes

NASA Astrophysics Data System (ADS)

Wacha, K.; Papanicolaou, T.; Hatfield, J.; Cambardella, C.; Abban, B. K.; Wilson, C. G.; Filley, T. R.; Hou, T.; Dold, C.

2017-12-01

The abundance and distribution of surface soil size fractions has been shown to be reflective of changes in management practices and landscape position. Soil size fractions exist in both un-aggregated and aggregated forms that differ in textural and biological composition, which can impact soil hydrology and aggregation processes. Soils with higher stocks of soil organic matter (SOM) promote higher biological activity, infiltration, and soil structure due to stronger, more resilient aggregates. Within ag-systems, intensive cultivation and steep gradients can negatively impact the formation/stability of aggregates and amplify erosion processes, which redistributes material along downslope flowpathways to varying degrees, based on the amount of available surface cover during a rainfall event. The innate variability in SOM composition found amongst the size fractions combined with these highly active flowpathways, produces a symphony of interactive biogeochemical and hydrologic processes, which promote spatial landscape heterogeneity. Due to this intricacy, accurately assessing changes in SOM stocks within high energy ag-systems is extremely challenging, and could greatly impact soil carbon budgets at the hillslope and greater spatial scales. To address this, in part, we utilize a systematic approach that isolates the role of management in building aggregate resilience to hydrologic forcing. Soil samples were collected from farm fields with varying slopes (1-20%) and management conditions, and then isolated into seven aggregate size fractions. Each aggregate fraction was tested for resilience to raindrop impact with corresponding SOM composition and biological activity. Rainfall simulations were conducted on plots under representative management and gradient to capture the dynamicity of the size fractions being transported during an applied rainfall event. Results found that small macroaggregate fractions were most indicative of changes in management, and erosion rates from plots were inversely proportional to SOM enrichment. These experiments not only promote our fundamental understanding on the dynamics of surface soil and SOM redistribution but also can provide guidance into best management practices that promote aggregate stability, decrease soil loss, and enhance soil health.

A multi-approach geophysical estimation of soil dynamic properties in settlements: a case study in Güzelbahce-İzmir (Western Anatolia)

NASA Astrophysics Data System (ADS)

Akgün, Mustafa; Gönenç, Tolga; Tunçel, Aykut; Pamukçu, Oya

2013-08-01

An earthquake is a natural disaster which cannot be predicted beforehand. The economic losses and casualties induced by earthquakes badly influence human life. In order to reduce these negative effects, buildings and structures should be designed to be earthquake resistant. In the design stage of earthquake-resistant structures, models of soil under dynamic conditions are used. The parameters that are required to account for soil dynamic models are shear wave velocity (Vs) values, stiffness, thickness, the number of layers, attenuation, rigidity and the depth to bedrock. These parameters are used to calculate an empirical transfer function, the bearing capacity of the soil and liquefaction. Within this context, these soil dynamic parameters should be obtained with the help of geophysical methods in situ, in the İzmir-Güzelbahçe region and its surrounds. The İzmir-Güzelbahçe region and its surrounds are located at the intersection point of two major faults (the İzmir fault and the Seferihisar fault). For this reason, soil dynamic parameters are variable in the lateral and vertical directions. These changes affect the soil Vs profiles. To identify the shear wave velocity (Vs) profile, common mid-point cross-correlation analysis of multi-channel surface-wave data (CMPCC MASW method), microtremor and microgravity methods can be used in common. As a result, when these three methods were evaluated together, it was concluded that the aforementioned region shows sudden lateral structure changes. Relying on these changes, the dynamic analyses that would be carried out to determine soil behavior at a possible earthquake site should be taken into consideration.

Microbial biomass and biological activity of soils and soil-like bodies in coastal oases of Antarctica

NASA Astrophysics Data System (ADS)

Nikitin, D. A.; Marfenina, O. E.; Kudinova, A. G.; Lysak, L. V.; Mergelov, N. S.; Dolgikh, A. V.; Lupachev, A. V.

2017-09-01

The method of luminescent microscopy has been applied to study the structure of the microbial biomass of soils and soil-like bodies in East (the Thala Hills and Larsemann Hills oases) and West (Cape Burks, Hobbs coast) Antarctica. According to Soil Taxonomy, the studied soils mainly belong to the subgroups of Aquic Haploturbels, Typic Haploturbels, Typic Haplorthels, and Lithic Haplorthels. The major contribution to their microbial biomass belongs to fungi. The highest fungal biomass (up to 790 μg C/g soil) has been found in the soils with surface organic horizons in the form of thin moss/lichen litters, in which the development of fungal mycelium is most active. A larger part of fungal biomass (70-98%) is represented by spores. For the soils without vegetation cover, the accumulation of bacterial and fungal biomass takes place in the horizons under surface desert pavements. In the upper parts of the soils without vegetation cover and in the organic soil horizons, the major part (>60%) of fungal mycelium contains protective melanin pigments. Among bacteria, the high portion (up to 50%) of small filtering forms is observed. A considerable increase (up to 290.2 ± 27 μg C/g soil) in the fungal biomass owing to the development of yeasts has been shown for gley soils (gleyzems) developing from sapropel sediments under subaquatic conditions and for the algal-bacterial mat on the bottom of the lake (920.7 ± 46 μg C/g soil). The production of carbon dioxide by the soils varies from 0.47 to 2.34 μg C-CO2/(g day). The intensity of nitrogen fixation in the studied samples is generally low: from 0.08 to 55.85 ng C2H4/(g day). The intensity of denitrification varies from 0.09 to 19.28 μg N-N2O/(g day).

Surficial geologic map of the Heath-Northfield-Southwick-Hampden 24-quadrangle area in the Connecticut Valley region, west-central Massachusetts

USGS Publications Warehouse

Stone, Janet R.; DiGiacomo-Cohen, Mary L.

2010-01-01

The surficial geologic map layer shows the distribution of nonlithified earth materials at land surface in an area of 24 7.5-minute quadrangles (1,238 mi2 total) in west-central Massachusetts. Across Massachusetts, these materials range from a few feet to more than 500 ft in thickness. They overlie bedrock, which crops out in upland hills and as resistant ledges in valley areas. The geologic map differentiates surficial materials of Quaternary age on the basis of their lithologic characteristics (such as grain size and sedimentary structures), constructional geomorphic features, stratigraphic relationships, and age. Surficial materials also are known in engineering classifications as unconsolidated soils, which include coarse-grained soils, fine-grained soils, and organic fine-grained soils. Surficial materials underlie and are the parent materials of modern pedogenic soils, which have developed in them at the land surface. Surficial earth materials significantly affect human use of the land, and an accurate description of their distribution is particularly important for assessing water resources, construction aggregate resources, and earth-surface hazards, and for making land-use decisions. This work is part of a comprehensive study to produce a statewide digital map of the surficial geology at a 1:24,000-scale level of accuracy. This report includes explanatory text, quadrangle maps at 1:24,000 scale (PDF files), GIS data layers (ArcGIS shapefiles), metadata for the GIS layers, scanned topographic base maps (TIF), and a readme.txt file.

Surficial geologic map of the Norton-Manomet-Westport-Sconticut Neck 23-quadrangle area in southeast Massachusetts

USGS Publications Warehouse

Stone, Byron D.; Stone, Janet R.; DiGiacomo-Cohen, Mary L.; Kincare, Kevin A.

2012-01-01

The surficial geologic map shows the distribution of nonlithified earth materials at land surface in an area of 23 7.5-minute quadrangles (919 mi2 total) in southeastern Massachusetts. Across Massachusetts, these materials range from a few feet to more than 500 ft in thickness. They overlie bedrock, which crops out in upland hills and as resistant ledges in valley areas. The geologic map differentiates surficial materials of Quaternary age on the basis of their lithologic characteristics (such as grain size and sedimentary structures), constructional geomorphic features, stratigraphic relationships, and age. Surficial materials also are known in engineering classifications as unconsolidated soils, which include coarse-grained soils, fine-grained soils, and organic fine-grained soils. Surficial materials underlie and are the parent materials of modern pedogenic soils, which have developed in them at the land surface. Surficial earth materials significantly affect human use of the land, and an accurate description of their distribution is particularly important for assessing water resources, construction aggregate resources, and earth-surface hazards, and for making land-use decisions. This work is part of a comprehensive study to produce a statewide digital map of the surficial geology at a 1:24,000-scale level of accuracy. This report includes explanatory text (PDF), quadrangle maps at 1:24,000 scale (PDF files), GIS data layers (ArcGIS shapefiles), metadata for the GIS layers, scanned topographic base maps (TIF), and a readme.txt file.

Surficial geologic map of the Mount Grace-Ashburnham-Monson-Webster 24-quadrangle area in central Massachusetts

USGS Publications Warehouse

Stone, Janet R.

2013-01-01

The surficial geologic map shows the distribution of nonlithified earth materials at land surface in an area of 24 7.5-minute quadrangles (1,238 mi2 total) in central Massachusetts. Across Massachusetts, these materials range from a few feet to more than 500 ft in thickness. They overlie bedrock, which crops out in upland hills and as resistant ledges in valley areas. The geologic map differentiates surficial materials of Quaternary age on the basis of their lithologic characteristics (such as grain size and sedimentary structures), constructional geomorphic features, stratigraphic relationships, and age. Surficial materials also are known in engineering classifications as unconsolidated soils, which include coarse-grained soils, fine-grained soils, and organic fine-grained soils. Surficial materials underlie and are the parent materials of modern pedogenic soils, which have developed in them at the land surface. Surficial earth materials significantly affect human use of the land, and an accurate description of their distribution is particularly important for assessing water resources, construction-aggregate resources, and earth-surface hazards, and for making land-use decisions. This work is part of a comprehensive study to produce a statewide digital map of the surficial geology at a 1:24,000-scale level of accuracy. This report includes explanatory text (PDF), quadrangle maps at 1:24,000 scale (PDF files), GIS data layers (ArcGIS shapefiles), metadata for the GIS layers, scanned topographic base maps (TIF), and a readme.txt file.

Insights into the attenuated sorption of organic compounds on black carbon aged in soil.

PubMed

Luo, Lei; Lv, Jitao; Chen, Zien; Huang, Rixiang; Zhang, Shuzhen

2017-12-01

Sorption of organic compounds on fresh black carbons (BCs) can be greatly attenuated in soil over time. We examined herein the changes in surface properties of maize straw-derived BCs (biochars) after aged in a black soil and their effects on the sorptive behaviors of naphthalene, phenanthrene and 1,3-dinitrobenzene. Dissolved fulvic and humic acids extracted from the soil were used to explore the role of dissolved organic carbon (DOC) in the aging of biochars. Chromatography analysis indicated that DOC molecules with relatively large molecular weight were preferentially adsorbed on the biochars during the aging processes. DOC sorption led to blockage of the biochar's micropores according to N 2 and CO 2 adsorption analyses. Surface chemistry of the biochars was also substantially modified, with more O-rich functional groups on the aged biochars compared to the original biochars, as evidenced by Near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and X-ray photoelectron spectroscopy (XPS) analyses. The changes in both the physical and chemical surface properties of biochars by DOC led to significant attenuation of the sorption capacity and nonlinearity of the nonionic organic compounds on the aged biochars. Among the tested organic compounds, phenanthrene was the most attenuated in its sorption by the aging treatments, possibly because of its relatively large molecular size and hydrophobicity. The information can help gain a mechanistic understanding of interactions between BCs and organic compounds in soil environment. Copyright © 2017 Elsevier Ltd. All rights reserved.

Soil and substrate morphology as witnesses of present and former agricultural landscape management

NASA Astrophysics Data System (ADS)

Chartin, C.; Salvador-Blanes, S.; Hinschberger, F.; Bourennane, H.; Macaire, J.-J.

2009-04-01

Water and tillage erosion, combined with the effect of successive regrouping of the land campaigns, have sensibly modified the morphology of cultivated hillslopes. Nowadays, we can still observe over cultivated landscapes various anthropogenic structures (e.g. lynchets) that correspond to former and/or present field limits. The aim of this work is to spatially characterise the geometry of these various structures, and to assess their relation with soil variability. The 10 ha studied site corresponds to an hillslope located in a small calcareous watershed near Tours in the Parisian Basin (France). Soils are mainly Cambisols (calcaric), Epileptic cambisols (calcaric) and Colluvic cambisols. This watershed is characterised by the presence of many soil accumulation structures and has been submitted to an important regrouping of the lands since the 1960's. The existing structures were accurately located and defined through a topographical analysis (slope, profile curvature...), and then related to past and present field limits using aerial photographies and cadastral maps. Two main morphological structures, deeply marked in the topography, are identified. The most remarkable type corresponds to well developed lynchets located at the lower part of field limits. Secondary structures, less marked than lynchets, are linked to field limits which existed at least since 1836, but that disappeared from the 1960's. These secondary structures look like longitudinal bulges placed perpendicularly to the direction of the main slope. A soil survey on these two geomorphic structure types has been performed in order to determine their specific geometry. Lynchets are characterised by a large increase in the thickness of soils: from 35 cm at 24 m upslope to more than 120 cm on its top. But, in some cases, the elevation study shows a topographical discontinuity between the top of the accumulation and the field or road below, discontinuity that is more important than the maximum soil thickness observed in the lynchet. This implies that the substrate, which is mostly homogeneous, has been largely excavated below these limits certainly due to repeated tillage operations. Concerning the secondary structures, soil thickness increases slightly from 35 cm at 16 m up- and downslope the former field limit to 70 cm at the maximum of the bulges convexity. However, the slope morphology seems to show larger soil accumulation considering a regular substrate morphology along the hillslope profile. Here too, by combining soil thickness and surface topography, we show that the substrate has certainly been strongly remodelled at these former field limits by tillage erosion. The spatial variability of the various soils types is closely linked to the sequence of structures oriented perpendicularly to the direction of the main slope. Although the current topography is clearly marked by various structures linked to former and present field limits, it appears that soil thickness is not the only factor explaining these large variations in the slope morphology: long-term agricultural practices, certainly tillage, "shape" the substrate as well. It is thus important to take into account these substrate excavations for sediment budget studies. The use of tracers such as 137Cs will allow to understand the intensity of these morphological changes at the slope scale within the last decades.

Hydrologically transported dissolved organic carbon influences soil respiration in a tropical rainforest

NASA Astrophysics Data System (ADS)

Zhou, Wen-Jun; Lu, Hua-Zheng; Zhang, Yi-Ping; Sha, Li-Qing; Schaefer, Douglas Allen; Song, Qing-Hai; Deng, Yun; Deng, Xiao-Bao

2016-10-01

To better understand the effect of dissolved organic carbon (DOC) transported by hydrological processes (rainfall, throughfall, litter leachate, and surface soil water; 0-20 cm) on soil respiration in tropical rainforests, we detected the DOC flux in rainfall, throughfall, litter leachate, and surface soil water (0-20 cm), compared the seasonality of δ13CDOC in each hydrological process, and δ13C in leaves, litter, and surface soil, and analysed the throughfall, litter leachate, and surface soil water (0-20 cm) effect on soil respiration in a tropical rainforest in Xishuangbanna, south-west China. Results showed that the surface soil intercepted 94.4 ± 1.2 % of the annual litter leachate DOC flux and is a sink for DOC. The throughfall and litter leachate DOC fluxes amounted to 6.81 and 7.23 % of the net ecosystem exchange respectively, indicating that the DOC flux through hydrological processes is an important component of the carbon budget, and may be an important link between hydrological processes and soil respiration in a tropical rainforest. Even the variability in soil respiration is more dependent on the hydrologically transported water than DOC flux insignificantly, soil temperature, and soil-water content (at 0-20 cm). The difference in δ13C between the soil, soil water (at 0-20 cm), throughfall, and litter leachate indicated that DOC is transformed in the surface soil and decreased the sensitivity indices of soil respiration of DOC flux to water flux, which suggests that soil respiration is more sensitive to the DOC flux in hydrological processes, especially the soil-water DOC flux, than to soil temperature or soil moisture.

77 FR 14717 - National Oil and Hazardous Substances Pollution Contingency Plan; National Priorities List...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-13

... preclude future actions under Superfund. This partial deletion pertains to the surface soil, unsaturated subsurface soil, surface water and sediments of Operable Unit (OU) 1, the Gateway Lake Ash Study Area, and.... Surface soil, unsaturated subsurface soil, surface water, and sediments at OU-2, OU-3, OU-4, OU-5, OU-6...

Spatial and temporal variability of soil temperature, moisture and surface soil properties

NASA Technical Reports Server (NTRS)

Hajek, B. F.; Dane, J. H.

1993-01-01

The overall objectives of this research were to: (l) Relate in-situ measured soil-water content and temperature profiles to remotely sensed surface soil-water and temperature conditions; to model simultaneous heat and water movement for spatially and temporally changing soil conditions; (2) Determine the spatial and temporal variability of surface soil properties affecting emissivity, reflectance, and material and energy flux across the soil surface. This will include physical, chemical, and mineralogical characteristics of primary soil components and aggregate systems; and (3) Develop surface soil classes of naturally occurring and distributed soil property assemblages and group classes to be tested with respect to water content, emissivity and reflectivity. This document is a report of studies conducted during the period funded by NASA grants. The project was designed to be conducted over a five year period. Since funding was discontinued after three years, some of the research started was not completed. Additional publications are planned whenever funding can be obtained to finalize data analysis for both the arid and humid locations.

The differences in crown formation during the splash on the thin water layers formed on the saturated soil surface and model surface

PubMed Central

Mazur, Rafał; Polakowski, Cezary; Bieganowski, Andrzej

2017-01-01

Splash is the first stage of a negative phenomenon–soil erosion. The aim of this work was to describe the crown formation quantitatively (as part of the splash erosion) and compare the course of this phenomenon on the thin water film formed on a smooth glass surface and on the surface of saturated soil. The height of the falling water drop was 1.5 m. The observation of the crowns was carried out by high-speed cameras. The static and dynamic parameters of crown formation were analysed. It was found that the crowns formed on the water film covering the saturated soil surface were smaller and the time intervals of their existence were shorter. In addition, the shapes of the crowns were different from those created on the water layer covering the glass surface. These differences can be explained by the slightly different values of surface tension and viscosity of the soil solution, the greater roughness of the soil surface and the lower thickness of the water film on the soil surface. PMID:28750072

The differences in crown formation during the splash on the thin water layers formed on the saturated soil surface and model surface.

PubMed

Beczek, Michał; Ryżak, Magdalena; Sochan, Agata; Mazur, Rafał; Polakowski, Cezary; Bieganowski, Andrzej

2017-01-01

Splash is the first stage of a negative phenomenon-soil erosion. The aim of this work was to describe the crown formation quantitatively (as part of the splash erosion) and compare the course of this phenomenon on the thin water film formed on a smooth glass surface and on the surface of saturated soil. The height of the falling water drop was 1.5 m. The observation of the crowns was carried out by high-speed cameras. The static and dynamic parameters of crown formation were analysed. It was found that the crowns formed on the water film covering the saturated soil surface were smaller and the time intervals of their existence were shorter. In addition, the shapes of the crowns were different from those created on the water layer covering the glass surface. These differences can be explained by the slightly different values of surface tension and viscosity of the soil solution, the greater roughness of the soil surface and the lower thickness of the water film on the soil surface.

Nitrate transport and transformation processes in unsaturated porous media

USGS Publications Warehouse

Tindall, James A.; Petrusak, Robin L.; McMahon, Peter B.

1995-01-01

A series of experiments was conducted on two contrasting agricultural soils to observe the influence of soil texture, preferential flow, and plants on nitrate transport and denitrification under unsaturated conditions. Calcium nitrate fertilizer was applied to the surface of four large undisturbed soil cores (30 cm diameter by 40 cm height). Two of the cores were a structured clay obtained from central Missouri and two were an unstructured fine sand obtained from central Florida. The cores were irrigated daily and maintained at a matric potential of -20 kPa, representative of soil tension in the rooting zone of irrigated agricultural fields. Volumetric water content (θ), concentration of nitrate-N in the soil solution, and nitrous oxide flux at the surface, 10, 20, and 30 cm were monitored daily. Leaching loss of surface-applied N03− -N was significant in both the sand and the clay. In unplanted sand cores, almost all of the applied nitrate was leached below 30 cm within 10 days. Gaseous N loss owing to denitrification was no greater than 2% of the nitrate-N applied to the unplanted sand cores and, in general, was less than 1 %. Although leaching was somewhat retarded in the clay cores, about 60% of the applied nitrate-N was leached from the unplanted clay soil in 5–6 weeks. Under unsaturated conditions, the clay had little to no tendency to denitrify despite the greater moisture content of the clay and retarded leaching of nitrate in the clay. The planted sand cores had surprisingly large gaseous N loss owing to denitrification, as much as 17% of the nitrate-N. Results from both the clay and sand experiments show that the dynamics of nitrate transport and transformation in unsaturated soils are affected by small, localized variations in the soil moisture content profile, the gaseous diffusion coefficient of the soil, the rate at which the nitrate pulse passes through the soil, the solubility of N2O and N2 and the diffusion of the gasses through the soil solution, and development of a water content profile in the soil. Limited dentrification in the clay soil was due to a limited volume of soil available for infiltration after internal catchment and the development of denitrifying conditions resulting from the presence of an extensive macropore system.

Influence of surface crusting on infiltration of a loess plateau soil

USDA-ARS?s Scientific Manuscript database

Surface sealing and crusting are common widespread processes that occur in many cultivated soils worldwide, especially in arid and semiarid regions. Soil crusting negatively affects water infiltration, increases surface runoff, reduces seedling emergence, restricts air exchange between the soil and ...

Periglacial morphogenesis in the Paris basin: insight from geophysical survey and consequences for the fate of soil pollution

NASA Astrophysics Data System (ADS)

Thiry, Médard; van Oort, Folkert; Thiesson, Julien; Van Vliet-Lanoe, Brigitte

2013-09-01

Geophysical survey by Automatic Resistivity Profiling (ARP©) system of the Pierrelaye-Bessancourt area revealed remarkable conductive polygon patterns of 20- to 30-m diameter detected between 0.5- and 1.7-m depth. Trenches dug down to the limestone substrate allowed detailing of the pedological and lithological units that compose such polygonal features. The patterns are formed by greenish glauconite and carbonated sand hollows where clay-rich pedological horizons bend downward, forming narrow tongs extending up to 2- to 3-m depth. Such structures were interpreted as a buried polygonal ice-wedge network (thermokarst depressions). Geometrical relationships between the lithological units and consecutive erosional surfaces allowed the identification of successive landscape events and a landscape chronology. The sequence started during the Saalian glaciation with (1) the development of patterned grounds by thermokarstic cryoturbation; (2) the consecutive deflation/erosion during post-permafrost aridity; (3) the loess and eolian sand deposits; (4) the weathering of the former deposits with development of pedogenic horizons during the Eemian interglacial; (5) the recurrent cryoturbation and thermal cracking leading to infolding of the pedogenic horizons during the Pleniglacial optimum (Weichselian); and finally (5) the erosion that levelled the periglacial microreliefs, most probably during the last glacial stage (Weichselian), leading to the modern landscape. In this agricultural area, urban waste water has been spread for more than 100 years by flooding irrigation for food crop production and has led to high levels of metal pollution in the surface horizons of the soils. The polygonal cryogenic structures have major impacts on soil hydrology and dispersion/distribution of heavy metals toward the geological substrate. Such structures are essential to consider when conceiving proposals for future soil management of this polluted area.

Geostatistical approach for management of soil nutrients with special emphasis on different forms of potassium considering their spatial variation in intensive cropping system of West Bengal, India.

PubMed

Chatterjee, Sourov; Santra, Priyabrata; Majumdar, Kaushik; Ghosh, Debjani; Das, Indranil; Sanyal, S K

2015-04-01

A large part of precision agriculture research in the developing countries is devoted towards precision nutrient management aspects. This has led to better economics and efficiency of nutrient use with off-farm advantages of environmental security. The keystone of precision nutrient management is analysis and interpretation of spatial variability of soils by establishing management zones. In this study, spatial variability of major soil nutrient contents was evaluated in the Ghoragacha village of North 24 Parganas district of West Bengal, India. Surface soil samples from 100 locations, covering different cropping systems of the village, was collected from 0 to 15 cm depth using 100×100 m grid system and analyzed in the laboratory to determine organic carbon (OC), available nitrogen (N), phosphorus (P), and potassium (K) contents of the soil as well as its water-soluble K (KWS), exchangeable K (KEX), and non-exchangeable forms of K (KNEX). Geostatistical analyses were performed to determine the spatial variation structure of each nutrient content within the village, followed by the generation of surface maps through kriging. Four commonly used semivariogram models, i.e., spherical, exponential, Gaussian, and linear models were fitted to each soil property, and the best one was used to prepare surface maps through krigging. Spherical model was found the best for available N and P contents, while linear and exponential model was the best for OC and available K, and for KWS and KNEK, Gausian model was the best. Surface maps of nutrient contents showed that N content (129-195 kg ha(-1)) was the most limiting factor throughout the village, while P status was generally very high ( 10-678 kg ha(-1)) in the soils of the present village. Among the different soil K fractions, KWS registered the maximum variability (CV 75%), while the remaining soil K fractions showed moderate to high variation. Interestingly, KNEX content also showed high variability, which essentially indicates reserve native K exploitation under intensive cultivation. These maps highlight the necessity of estimating the other soil K fractions as well for better understanding of soil K supplying capacity and K fertilization strategy rather than the current recommendations, based on the plant-available K alone. In conclusion, the present study revealed that the variability of nutrient distribution was a consequence of complex interactions between the cropping system, nutrient application rates, and the native soil characteristics, and such interactions could be utilized to develop the nutrient management strategies for intensive small-holder system.

Plant Community and Nitrogen Deposition as Drivers of Alpha and Beta Diversities of Prokaryotes in Reconstructed Oil Sand Soils and Natural Boreal Forest Soils

PubMed Central

Prescott, Cindy E.; Renaut, Sébastien; Terrat, Yves; Grayston, Sue J.

2017-01-01

ABSTRACT The Athabasca oil sand deposit is one of the largest single oil deposits in the world. Following surface mining, companies are required to restore soil-like profiles that can support the previous land capabilities. The objective of this study was to assess whether the soil prokaryotic alpha diversity (α-diversity) and β-diversity in oil sand soils reconstructed 20 to 30 years previously and planted to one of three vegetation types (coniferous or deciduous trees and grassland) were similar to those found in natural boreal forest soils subject to wildfire disturbance. Prokaryotic α-diversity and β-diversity were assessed using massively parallel sequencing of 16S rRNA genes. The β-diversity, but not the α-diversity, differed between reconstructed and natural soils. Bacteria associated with an oligotrophic lifestyle were more abundant in natural forest soils, whereas bacteria associated with a copiotrophic lifestyle were more abundant in reconstructed soils. Ammonia-oxidizing archaea were most abundant in reconstructed soils planted with grasses. Plant species were the main factor influencing α-diversity in natural and in reconstructed soils. Nitrogen deposition, pH, and plant species were the main factors influencing the β-diversity of the prokaryotic communities in natural and reconstructed soils. The results highlight the importance of nitrogen deposition and aboveground-belowground relationships in shaping soil microbial communities in natural and reconstructed soils. IMPORTANCE Covering over 800 km2, land disturbed by the exploitation of the oil sands in Canada has to be restored. Here, we take advantage of the proximity between these reconstructed ecosystems and the boreal forest surrounding the oil sand mining area to study soil microbial community structure and processes in both natural and nonnatural environments. By identifying key characteristics shaping the structure of soil microbial communities, this study improved our understanding of how vegetation, soil characteristics and microbial communities interact and drive soil functions. PMID:28213542

Radioisotope tracer approach for understanding the impacts of global change-induced pedoturbation on soil C dynamics

NASA Astrophysics Data System (ADS)

Gonzalez-Meler, M. A.; Sturchio, N. C.; Sanchez-de Leon, Y.; Blanc-Betes, E.; Taneva, L.; Poghosyan, A.; Norby, R. J.; Filley, T. R.; Guilderson, T. P.; Welker, J. M.

2010-12-01

Biogeochemical carbon-cycle feedbacks to climate are apparent but uncertain, primarily because of gaps in mechanistic understanding on the ecosystem processes that drive carbon cycling and storage in terrestrial ecosystems, particularly in soils. Recent findings are increasingly recognizing the interaction between soil biota and the soil physical environment. Soil carbon turnover is partly determined by burial of organic matter and its physical and chemical protection. These factors are potentially affected by changes in climate (freezing-thawing or wet-drying cycles) or ecosystem structure including biological invasions. A major impediment to understanding dynamics of soil C in terrestrial systems is our inability to measure soil physical processes such as soil mixing rates or turnover of soil structures, including aggregates. Here we present a multiple radioisotope tracer approach (naturally occurring and man-made) to measure soil mixing rates in response to global change. We will present evidence of soil mixing rate changes in a temperate forest exposed to increased levels of atmospheric CO2 and in a tundra ecosystem exposed to increased thermal insulation. In both cases, radioisotope tracers proved to be an effective way to measure effects of global change on pedoturbation. Results also provided insights into the specific mechanisms involved in the responses. Elevated CO2 resulted in deeper soil mixing cells (increased by about 5cm on average) when compared to control soils as a consequence of changes in biota (increased root growth, higher earthworm density). In the tundra, soil warming induced higher rates of cryoturbation, resulting in what appears to be a net uplift of organic matter to the surface thereby exposing deeper C to decomposers. In both cases, global change factors affected the vertical distribution of C and changed the amount of bulk soil actively involved in soil processes. As a consequence, comparisons of C budgets to a given soil depth in response to global change factors may be misleading if they do not account for the depth change in the soil mixing cells.

Plant Community and Nitrogen Deposition as Drivers of Alpha and Beta Diversities of Prokaryotes in Reconstructed Oil Sand Soils and Natural Boreal Forest Soils.

PubMed

Masse, Jacynthe; Prescott, Cindy E; Renaut, Sébastien; Terrat, Yves; Grayston, Sue J

2017-05-01

The Athabasca oil sand deposit is one of the largest single oil deposits in the world. Following surface mining, companies are required to restore soil-like profiles that can support the previous land capabilities. The objective of this study was to assess whether the soil prokaryotic alpha diversity (α-diversity) and β-diversity in oil sand soils reconstructed 20 to 30 years previously and planted to one of three vegetation types (coniferous or deciduous trees and grassland) were similar to those found in natural boreal forest soils subject to wildfire disturbance. Prokaryotic α-diversity and β-diversity were assessed using massively parallel sequencing of 16S rRNA genes. The β-diversity, but not the α-diversity, differed between reconstructed and natural soils. Bacteria associated with an oligotrophic lifestyle were more abundant in natural forest soils, whereas bacteria associated with a copiotrophic lifestyle were more abundant in reconstructed soils. Ammonia-oxidizing archaea were most abundant in reconstructed soils planted with grasses. Plant species were the main factor influencing α-diversity in natural and in reconstructed soils. Nitrogen deposition, pH, and plant species were the main factors influencing the β-diversity of the prokaryotic communities in natural and reconstructed soils. The results highlight the importance of nitrogen deposition and aboveground-belowground relationships in shaping soil microbial communities in natural and reconstructed soils. IMPORTANCE Covering over 800 km 2 , land disturbed by the exploitation of the oil sands in Canada has to be restored. Here, we take advantage of the proximity between these reconstructed ecosystems and the boreal forest surrounding the oil sand mining area to study soil microbial community structure and processes in both natural and nonnatural environments. By identifying key characteristics shaping the structure of soil microbial communities, this study improved our understanding of how vegetation, soil characteristics and microbial communities interact and drive soil functions. Copyright © 2017 American Society for Microbiology.

What can we learn from in-soil imaging of a live plant: X-ray Computed Tomography and 3D numerical simulation of root-soil system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Xiaofan; Varga, Tamas; Liu, Chongxuan

Plant roots play a critical role in plant-soil-microbe interactions that occur in the rhizosphere, as well as processes with important implications to farming, forest management and climate change. X-ray computed tomography (XCT) has been proven to be an effective tool for non-invasive root imaging and analysis. A combination of XCT, open-source software, and our own code was used to noninvasively image a prairie dropseed (Sporobolus heterolepis) specimen, segment the root data to obtain a 3D image of the root structure at 31µm resolution, and extract quantitative information (root volume and surface area) from the 3D data, respectively. Based on themore » mesh generated from the root structure, computational fluid dynamics (CFD) simulations were applied to numerically investigate the root-soil-groundwater system. The plant root conductivity, soil hydraulic conductivity and transpiration rate were shown to control the groundwater distribution. The flow variability and soil water distributions under different scenarios were investigated. Parameterizations were evaluated to show their impacts on the average conductivity. The pore-scale modeling approach provides realistic simulations of rhizosphere flow processes and provides useful information that can be linked to upscaled models.« less

[Detecting the moisture content of forest surface soil based on the microwave remote sensing technology.

PubMed

Li, Ming Ze; Gao, Yuan Ke; Di, Xue Ying; Fan, Wen Yi

2016-03-01

The moisture content of forest surface soil is an important parameter in forest ecosystems. It is practically significant for forest ecosystem related research to use microwave remote sensing technology for rapid and accurate estimation of the moisture content of forest surface soil. With the aid of TDR-300 soil moisture content measuring instrument, the moisture contents of forest surface soils of 120 sample plots at Tahe Forestry Bureau of Daxing'anling region in Heilongjiang Province were measured. Taking the moisture content of forest surface soil as the dependent variable and the polarization decomposition parameters of C band Quad-pol SAR data as independent variables, two types of quantitative estimation models (multilinear regression model and BP-neural network model) for predicting moisture content of forest surface soils were developed. The spatial distribution of moisture content of forest surface soil on the regional scale was then derived with model inversion. Results showed that the model precision was 86.0% and 89.4% with RMSE of 3.0% and 2.7% for the multilinear regression model and the BP-neural network model, respectively. It indicated that the BP-neural network model had a better performance than the multilinear regression model in quantitative estimation of the moisture content of forest surface soil. The spatial distribution of forest surface soil moisture content in the study area was then obtained by using the BP neural network model simulation with the Quad-pol SAR data.

Influence of soil structure on contaminant leaching from injected slurry

USDA-ARS?s Scientific Manuscript database

Animal manure application to agricultural land provides beneficial organic matter and nutrients but can spread harmful contaminants to the environment. Contamination of fresh produce, surface water and shallow groundwater with the manure-borne pollutants can be a critical concern. Leaching and persi...

36 CFR 228.108 - Surface use requirements.

Code of Federal Regulations, 2011 CFR

2011-07-01

... by the authorized Forest officer. (3) The operator must: (i) Control soil erosion and landslides; (ii...; (iv) Reshape and revegetate disturbed areas; (v) Remove structures, improvements, facilities and..., facilities, improvements, and equipment located on the area of operation in a safe and neat manner and in...

Representing the effects of alpine grassland vegetation cover on the simulation of soil thermal dynamics by ecosystem models applied to the Qinghai-Tibetan Plateau

NASA Astrophysics Data System (ADS)

Yi, S.; Li, N.; Xiang, B.; Wang, X.; Ye, B.; McGuire, A. D.

2013-07-01

surface temperature is a critical boundary condition for the simulation of soil temperature by environmental models. It is influenced by atmospheric and soil conditions and by vegetation cover. In sophisticated land surface models, it is simulated iteratively by solving surface energy budget equations. In ecosystem, permafrost, and hydrology models, the consideration of soil surface temperature is generally simple. In this study, we developed a methodology for representing the effects of vegetation cover and atmospheric factors on the estimation of soil surface temperature for alpine grassland ecosystems on the Qinghai-Tibetan Plateau. Our approach integrated measurements from meteorological stations with simulations from a sophisticated land surface model to develop an equation set for estimating soil surface temperature. After implementing this equation set into an ecosystem model and evaluating the performance of the ecosystem model in simulating soil temperature at different depths in the soil profile, we applied the model to simulate interactions among vegetation cover, freeze-thaw cycles, and soil erosion to demonstrate potential applications made possible through the implementation of the methodology developed in this study. Results showed that (1) to properly estimate daily soil surface temperature, algorithms should use air temperature, downward solar radiation, and vegetation cover as independent variables; (2) the equation set developed in this study performed better than soil surface temperature algorithms used in other models; and (3) the ecosystem model performed well in simulating soil temperature throughout the soil profile using the equation set developed in this study. Our application of the model indicates that the representation in ecosystem models of the effects of vegetation cover on the simulation of soil thermal dynamics has the potential to substantially improve our understanding of the vulnerability of alpine grassland ecosystems to changes in climate and grazing regimes.

How surface mounds and depressions change during rainfall events

USDA-ARS?s Scientific Manuscript database

The soil roughness, or microrelief, controls processes occurring on the surface. Although there are numerous studies on how soil roughness affects soil erosion processes, little are focused on quantifying different roughness functions on surface hydrology and erosion, i.e., water diverging and soil...

Water stability of aggregates in subtropical and tropical soils (Georgia and China) and its relationships with the mineralogy and chemical properties

NASA Astrophysics Data System (ADS)

Alekseeva, T. V.; Sokolowska, Z.; Hajnos, M.; Alekseev, A. O.; Kalinin, P. I.

2009-04-01

Water-stable aggregates isolated from three subtropical and one tropical soil (Western Georgia and China) were studied for their organic carbon, cation exchange capacity (CEC), specific surface area, magnetic susceptibility, and total chemical elements. The soils were also studied for their particle-size distribution, mineralogy, and nonsilicate Fe and Al oxides. Describe the water stability, three indices have been used: the content of water-stable macroaggregates (>0.25 mm), the mean weighted diameter of the aggregates, and the numerical aggregation index. The yellow-cinnamonic soil (China) was neutral, and the three other soils were acid. The soils were degraded with a low content of organic matter. The yellow-cinnamonic soil was characterized by the lowest water stability due to the predominantly vermiculite composition of the clay. The high water stability of the Oxisol structure was determined by the kaolinites and high content of oxides. In three out of the four soils studied, the hierarchical levels of the soil structure organization were defined; they were identified by the content of organic matter and the Ca + Mg (in Oxisols). Iron oxides mainly participated in the formation of micro-aggregates; Al and Mn contributed to the formation of macroaggregates. The water-stable aggregates acted as sorption geochemical barriers and accumulated Pb, Zn, Cd, Cs, and other trace elements up to concentrations exceeding their levels in the soil by 5 times and more. The highest correlations were obtained with CEC, Mn, and P rather than with organic carbon and Fe.

Role of Subsurface Physics in the Assimilation of Surface Soil Moisture Observations

NASA Technical Reports Server (NTRS)

Reichle, R. H.

2010-01-01

Root zone soil moisture controls the land-atmosphere exchange of water and energy and exhibits memory that may be useful for climate prediction at monthly scales. Assimilation of satellite-based surface soil moisture observations into a land surface model is an effective way to estimate large-scale root zone soil moisture. The propagation of surface information into deeper soil layers depends on the model-specific representation of subsurface physics that is used in the assimilation system. In a suite of experiments we assimilate synthetic surface soil moisture observations into four different models (Catchment, Mosaic, Noah and CLM) using the Ensemble Kalman Filter. We demonstrate that identical twin experiments significantly overestimate the information that can be obtained from the assimilation of surface soil moisture observations. The second key result indicates that the potential of surface soil moisture assimilation to improve root zone information is higher when the surface to root zone coupling is stronger. Our experiments also suggest that (faced with unknown true subsurface physics) overestimating surface to root zone coupling in the assimilation system provides more robust skill improvements in the root zone compared with underestimating the coupling. When CLM is excluded from the analysis, the skill improvements from using models with different vertical coupling strengths are comparable for different subsurface truths. Finally, the skill improvements through assimilation were found to be sensitive to the regional climate and soil types.

Quantifying vegetation distribution and structure using high resolution drone-based structure-from-motion photogrammetry

NASA Astrophysics Data System (ADS)

Zhang, J.; Okin, G.

2017-12-01

Vegetation is one of the most important driving factors of different ecosystem processes in drylands. The structure of vegetation controls the spatial distribution of moisture and heat in the canopy and the surrounding area. Also, the structure of vegetation influences both airflow and boundary layer resistance above the land surface. Multispectral satellite remote sensing has been widely used to monitor vegetation coverage and its change; however, it can only capture 2D images, which do not contain the vertical information of vegetation. In situ observation uses different methods to measure the structure of vegetation, and their results are accurate; however, these methods are laborious and time-consuming, and susceptible to undersampling in spatial heterogeneity. Drylands are sparsely covered by short plants, which allows the drone fly at a relatively low height to obtain ultra-high resolution images. Structure-from-motion (SfM) is a photogrammetric method that was proved to produce 3D model based on 2D images. Drone-based remote sensing can obtain the multiangle images for one object, which can be used to constructed 3D models of vegetation in drylands. Using these images detected by the drone, the orthomosaics and digital surface model (DSM) can be built. In this study, the drone-based remote sensing was conducted in Jornada Basin, New Mexico, in the spring of 2016 and 2017, and three derived vegetation parameters (i.e., canopy size, bare soil gap size, and plant height) were compared with those obtained with field measurement. The correlation coefficient of canopy size, bare soil gap size, and plant height between drone images and field data are 0.91, 0.96, and 0.84, respectively. The two-year averaged root-mean-square error (RMSE) of canopy size, bare soil gap size, and plant height between drone images and field data are 0.61 m, 1.21 m, and 0.25 cm, respectively. The two-year averaged measure error (ME) of canopy size, bare soil gap size, and plant height between drone images and field data are 0.02 m, -0.03, and -0.1 m, respectively. These results indicate a good agreement between drone-based remote sensing and field measurement.

Does Diffusion Sequester Heavy Metals in Old Contamination Soils?

NASA Astrophysics Data System (ADS)

Ma, J.; Jennings, A. A.

2002-12-01

Old soil contamination refers to soil contamination that has aged over a long period of time. For example, at some brownfields, the soil heavy metal contamination can be one hundred or more years old. When contamination is young, the heavy metals are bound relatively weakly to the soil. However, the speciation and/or mechanisms of association evolve with aging into much more stable forms. It also appears that the metals migrate deeper into the bulk soil matrix where they are less available to participate in surface-related phenomena. Previous research showed elevated heavy metal extraction result after the soil was pulverized, with all other experiment conditions remaining unchanged. This indicates the presence of sequestered heavy metal contamination within the large soil particles (aggregate). The mechanisms of sequestering are uncertain, but diffusion appears to be a major factor. There are two possible pathways of diffusion that can account for heavy metal sequestering: solid-state diffusion through the bulk aggregate or liquid-phase diffusion through micro-pores within the aggregate structure. The second diffusion mechanism can be coupled with sorption (or other surface-related phenomena) on the pore walls. The remediation of sequestered heavy metals is also impacted by diffusion. Grinding a soil significantly reduces its average particle size. This exposes more of its internal bulk volume to extraction and results in much shorter diffusion pathway for the sequestered heavy metals to be released. Evidence has illustrated that this both improves remediation efficiency and provides a method by which the degree of sequestering can be quantified. This paper will present the results of ongoing research that is developing methods to identify the mechanisms of, quantify the magnitude of and determine the relative importance of (i.e. risk analysis) heavy metals sequestered in old contamination soils.

Nanoscale Analysis of Space-Weathering Features in Soils from Itokawa

NASA Technical Reports Server (NTRS)

Thompson, M. S.; Christoffersen, R.; Zega, T. J.; Keller, L. P.

2014-01-01

Space weathering alters the spectral properties of airless body surface materials by redden-ing and darkening their spectra and attenuating characteristic absorption bands, making it challenging to characterize them remotely [1,2]. It also causes a discrepency between laboratory analysis of meteorites and remotely sensed spectra from asteroids, making it difficult to associate meteorites with their parent bodies. The mechanisms driving space weathering include mi-crometeorite impacts and the interaction of surface materials with solar energetic ions, particularly the solar wind. These processes continuously alter the microchemical and structural characteristics of exposed grains on airless bodies. The change of these properties is caused predominantly by the vapor deposition of reduced Fe and FeS nanoparticles (npFe(sup 0) and npFeS respectively) onto the rims of surface grains [3]. Sample-based analysis of space weathering has tra-ditionally been limited to lunar soils and select asteroidal and lunar regolith breccias [3-5]. With the return of samples from the Hayabusa mission to asteroid Itoka-wa [6], for the first time we are able to compare space-weathering features on returned surface soils from a known asteroidal body. Analysis of these samples will contribute to a more comprehensive model for how space weathering varies across the inner solar system. Here we report detailed microchemical and microstructal analysis of surface grains from Itokawa.

Influence of humic substances and iron and aluminum ions on the sorption of acetamiprid to an arable soil.

PubMed

Murano, Hirotatsu; Suzuki, Katsuhiro; Kayada, Saori; Saito, Mitsuhiko; Yuge, Naoya; Arishiro, Takuji; Watanabe, Akira; Isoi, Toshiyuki

2018-02-15

Humic substances (HS) in soil and sediments, and surface water influence the behavior of organic xenobiotics in the environment. However, our knowledge of the effects of specific HS fractions, i.e., humic acids (HAs), fulvic acids (FAs), and humin (HM), on the sorption of organic xenobiotics is limited. The neonicotinoid insecticide acetamiprid is thought to contribute to the collapse of honeybee colonies. To understand the role that soil organic matter plays in the fate of acetamiprid, interactions between acetamiprid and the above HS fractions were examined. Batch experiments were conducted using various combinations of a field soil sample and the above 3 HS fractions prepared from the same soil, and differences in isotherm values for acetamiprid sorption were investigated based on the structural differences among the HS fractions. The sorption of acetamiprid to soil minerals associated with HM (MHM) (Freundlich isotherm constant, K f : 6.100) was reduced when HAs or FAs were added (K f : 4.179 and 4.756, respectively). This can be attributed to hydrophobic interactions between HM and HAs or FAs in which their dissociated carboxyl and phenolic groups become oriented to face the soil solution. The amount of acetamiprid that was adsorbed to (MHM+HA) or (MHM+FA) increased when aluminum ions were added (K f : 6.933 and 10.48, respectively), or iron ions were added (K f : 7.303 and 11.29, respectively). Since acetamiprid has no affinity for inorganic components in soil, the formation of HS-metal complexes by cation bridging may have oriented the hydrophobic moieties in the HAs or FAs to face the soil solution and may also have resulted in the formation of dense structures, resulting in an increase in the amount of acetamiprid that becomes adsorbed to these structures. These results highlight the importance of interactions among soil components in the pedospheric diffusion of acetamiprid. Copyright © 2017 Elsevier B.V. All rights reserved.

Improved Prediction of Quasi-Global Vegetation Conditions Using Remotely-Sensed Surface Soil Moisture

NASA Technical Reports Server (NTRS)

Bolten, John; Crow, Wade

2012-01-01

The added value of satellite-based surface soil moisture retrievals for agricultural drought monitoring is assessed by calculating the lagged rank correlation between remotely-sensed vegetation indices (VI) and soil moisture estimates obtained both before and after the assimilation of surface soil moisture retrievals derived from the Advanced Microwave Scanning Radiometer-EOS (AMSR-E) into a soil water balance model. Higher soil moisture/VI lag correlations imply an enhanced ability to predict future vegetation conditions using estimates of current soil moisture. Results demonstrate that the assimilation of AMSR-E surface soil moisture retrievals substantially improve the performance of a global drought monitoring system - particularly in sparsely-instrumented areas of the world where high-quality rainfall observations are unavailable.

The AMMA-CATCH Gourma observatory site in Mali: Relating climatic variations to changes in vegetation, surface hydrology, fluxes and natural resources

NASA Astrophysics Data System (ADS)

Mougin, E.; Hiernaux, P.; Kergoat, L.; Grippa, M.; de Rosnay, P.; Timouk, F.; Le Dantec, V.; Demarez, V.; Lavenu, F.; Arjounin, M.; Lebel, T.; Soumaguel, N.; Ceschia, E.; Mougenot, B.; Baup, F.; Frappart, F.; Frison, P. L.; Gardelle, J.; Gruhier, C.; Jarlan, L.; Mangiarotti, S.; Sanou, B.; Tracol, Y.; Guichard, F.; Trichon, V.; Diarra, L.; Soumaré, A.; Koité, M.; Dembélé, F.; Lloyd, C.; Hanan, N. P.; Damesin, C.; Delon, C.; Serça, D.; Galy-Lacaux, C.; Seghieri, J.; Becerra, S.; Dia, H.; Gangneron, F.; Mazzega, P.

2009-08-01

SummaryThe Gourma site in Mali is one of the three instrumented meso-scale sites deployed in West-Africa as part of the African Monsoon Multi-disciplinary Analysis (AMMA) project. Located both in the Sahelian zone sensu stricto, and in the Saharo-Sahelian transition zone, the Gourma meso-scale window is the northernmost site of the AMMA-CATCH observatory reached by the West African Monsoon. The experimental strategy includes deployment of a variety of instruments, from local to meso-scale, dedicated to monitoring and documentation of the major variables characterizing the climate forcing, and the spatio-temporal variability of surface processes and state variables such as vegetation mass, leaf area index (LAI), soil moisture and surface fluxes. This paper describes the Gourma site, its associated instrumental network and the research activities that have been carried out since 1984. In the AMMA project, emphasis is put on the relations between climate, vegetation and surface fluxes. However, the Gourma site is also important for development and validation of satellite products, mainly due to the existence of large and relatively homogeneous surfaces. The social dimension of the water resource uses and governance is also briefly analyzed, relying on field enquiry and interviews. The climate of the Gourma region is semi-arid, daytime air temperatures are always high and annual rainfall amounts exhibit strong inter-annual and seasonal variations. Measurements sites organized along a north-south transect reveal sharp gradients in surface albedo, net radiation, vegetation production, and distribution of plant functional types. However, at any point along the gradient, surface energy budget, soil moisture and vegetation growth contrast between two main types of soil surfaces and hydrologic systems. On the one hand, sandy soils with high water infiltration rates and limited run-off support almost continuous herbaceous vegetation with scattered woody plants. On the other hand, water infiltration is poor on shallow soils, and vegetation is sparse and discontinuous, with more concentrated run-off that ends in pools or low lands within structured endorheic watersheds. Land surface in the Gourma is characterized by rapid response to climate variability, strong intra-seasonal, seasonal and inter-annual variations in vegetation growth, soil moisture and energy balance. Despite the multi-decadal drought, which still persists, ponds and lakes have increased, the grass cover has largely recovered, and there are signs of increased tree cover at least in the low lands.

Solanum lycopersicum (tomato) hosts robust phyllosphere and rhizosphere bacterial communities when grown in soil amended with various organic and synthetic fertilizers.

PubMed

Allard, Sarah M; Walsh, Christopher S; Wallis, Anna E; Ottesen, Andrea R; Brown, Eric W; Micallef, Shirley A

2016-12-15

Due to the intimate association between plants and their microbial symbionts, an examination of the influence of agricultural practices on phytobiome structure and diversity could foster a more comprehensive understanding of plant health and produce safety. Indeed, the impact of upstream crop producti006Fn practices cannot be overstated in their role in assuring an abundant and safe food supply. To assess whether fertilizer type impacted rhizosphere and phyllosphere bacterial communities associating with tomato plants, the bacterial microbiome of tomato cv. 'BHN602' grown in soils amended with fresh poultry litter, commercially available sterilized poultry litter pellets, vermicompost or synthetic fertilizer was described. Culture independent DNA was extracted from bulk and rhizosphere soils, and washes of tomato blossoms and ripe fruit. PCR amplicons of hypervariable regions of the 16S rRNA gene were sequenced and profiled using the QIIME pipeline. Bulk and rhizosphere soil, and blossom and fruit surfaces all supported distinct bacterial communities according to principal coordinate analysis and ANOSIM (R=0.87, p=0.001 in year 1; R=0.93, p=0.001 in year 2). Use of microbiologically diverse organic fertilizers generally did not influence bacterial diversity, community structure or relative abundance of specific taxa on any plant organ surface. However, statistically significant differences in sand and silt contents of soil (p<0.05) across the field and corresponding shifts in water activity were positively (R 2 =0.52, p=0.005) and negatively (R 2 =0.48, p=0.009) correlated with changes in bacterial community structure in the rhizosphere, respectively. Over two harvest seasons, this study demonstrated that the application of raw poultry manure, poultry litter pellets and vermicompost had little effect on the tomato microbiome in the rhizosphere and phyllosphere, when compared to synthetically fertilized plants. Plant anatomy, and other factors related to field location, possibly associated with edaphic and air characteristics, were more influential drivers of different tomato organ microbiomes than were diverse soil amendment applications. Copyright © 2016 Elsevier B.V. All rights reserved.

Clay fractions from a soil chronosequence after glacier retreat reveal the initial evolution of organo-mineral associations

NASA Astrophysics Data System (ADS)

Dümig, Alexander; Häusler, Werner; Steffens, Markus; Kögel-Knabner, Ingrid

2012-05-01

Interactions between organic and mineral constituents prolong the residence time of organic matter in soils. However, the structural organization and mechanisms of organic coverage on mineral surfaces as well as their development with time are still unclear. We used clay fractions from a soil chronosequence (15, 75 and 120 years) in the foreland of the retreating Damma glacier (Switzerland) and from mature soils outside the proglacial area (>700 and <3000 years) to elucidate the evolution of organo-mineral associations during initial soil formation. The chemical composition of the clay-bound organic matter (OM) was assessed by solid-state 13C NMR spectroscopy while the quantities of amino acids and neutral sugar monomers were determined after acid hydrolysis. The mineral phase was characterized by X-ray diffraction, oxalate extraction, specific surface area by N2 adsorption (BET approach), and cation exchange capacity at pH 7 (CECpH7). The last two methods were applied before and after H2O2 treatment. We found pronounced shifts in quantity and quality of OM during aging of the clay fractions, especially within the first one hundred years of soil formation. The strongly increasing organic carbon (OC) loading of clay-sized particles resulted in decreasing specific surface areas (SSA) of the mineral phases and increasing CECpH7. Thus, OC accumulation was faster than the supply of mineral surfaces and cation exchange capacity was mainly determined by the OC content. Clay-bound OC of the 15-year-old soils showed high proportions of carboxyl C and aromatic C. This may point to remnants of ancient OC which were inherited from the recently exposed glacial till. With increasing age (75 and 120 years), the relative proportions of carboxyl and aromatic C decreased. This was associated with increasing O-alkyl C proportions, whereas accumulation of alkyl C was mainly detected in clay fractions from the mature soils. These findings from solid-state 13C NMR spectroscopy are in line with the increasing amounts of microbial-derived carbohydrates with soil age. The large accumulation of proteins, which was comparable to those of carbohydrates, and the very low C/N ratios of H2O2-resistant OM indicated strong and preferential associations between proteinaceous compounds and mineral surfaces. In the acid soils, poorly crystalline Fe oxides were the main providers of mineral surface area and important for the stabilization of OM during aging of the clay fractions. This was indicated by (I) the strong correlations between oxalate soluble Fe and both, SSA of H2O2-treated clay fractions and OC content, and (II) the low formation of expandable clays due to small extents of mineral weathering. Our chronosequence approach provided new insights into the evolution of organo-mineral interactions in acid soils. The formation of organo-mineral associations started with the sorption of proteinaceous compounds and microbial-derived carbohydrates on mineral surfaces which were mainly provided by ferrihydrite. The sequential accumulation of different organic compounds and the large OC loadings point to multiple accretion of OM in distinct zones or layers during the initial evolution of clay fractions.

Distribution of volatile organic compounds (VOCs) in surface water, soil, and groundwater within a chemical industry park in Eastern China.

PubMed

Liu, Benhua; Chen, Liang; Huang, Linxian; Wang, Yongseng; Li, Yuehua

2015-01-01

This paper focuses on the distribution of volatile organic compounds (VOCs) in the surface water, soil, and groundwater within a chemical industry park in Eastern China. At least one VOC was detected in each of the 20 sampling sites, and the maximum number of VOCs detected in the surface water, groundwater, and soil were 13, 16, and 14, respectively. Two of the 10 VOCs with elevated concentrations detected in surface water, groundwater, and soil were chloroform and 1,2-dichloroethane. The characteristics of VOCs, which include volatility, boiling point, and solubility, could significantly affect their distribution in surface water, soil, and groundwater. However, due to the direct discharging of chemical industry wastewater into surface water, higher concentrations of VOCs (except chloroform) were detected in surface water than in soil and groundwater. Fortunately, the higher volatility of VOCs prevents the VOCs from impacting groundwater, which helps to maintain a lower concentration of VOCs in the groundwater than in both surface water and soil. This is because pollutants with relatively higher boiling points and lower solubilities have higher detection frequencies in soil, and contaminants with relatively lower boiling points and higher solubilities have higher detection frequencies in water, notably in surface water.

Surface reactions of iron - enriched smectites: adsorption and transformation of hydroxy fatty acids and phenolic acids

NASA Astrophysics Data System (ADS)

Polubesova, Tamara; Olshansky, Yaniv; Eldad, Shay; Chefetz, Benny

2014-05-01

Iron-enriched smectites play an important role in adsorption and transformation of soil organic components. Soil organo-clay complexes, and in particular humin contain hydroxy fatty acids, which are derived from plant biopolymer cutin. Phenolic acids belong to another major group of organic acids detected in soil. They participate in various soil processes, and are of concern due to their allelopathic activity. We studied the reactivity of iron-enriched smectites (Fe(III)-montmorillonite and nontronite) toward both groups of acids. We used fatty acids- 9(10),16-dihydroxypalmitic acid (diHPA), isolated from curtin, and 9,10,16-trihydroxypalmitic acid (triHPA); the following phenolic acids were used: ferulic, p-coumaric, syringic, and vanillic. Adsorption of both groups of acids was measured. The FTIR spectra of fatty acid-mineral complexes indicated inner-sphere complexation of fatty acids with iron-enriched smectites (versus outer-sphere complexation with Ca(II)-montmorillonite). The LC-MS results demonstrated enhanced esterification of fatty acids on the iron-enriched smectite surfaces (as compared to Ca(II)-montmorillonite). This study suggests that fatty acids can be esterified on the iron-enriched smectite surfaces, which results in the formation of stable organo-mineral complexes. These complexes may serve as a model for the study of natural soil organo-clay complexes and humin. The reaction of phenolic acids with Fe(III)-montmorillonite demonstrated their oxidative transformation by the mineral surfaces, which was affected by molecular structure of acids. The following order of their transformation was obtained: ferulic >syringic >p-coumaric >vanillic. The LC-MS analysis demonstrated the presence of dimers, trimers, and tetramers of ferulic acid on the surface of Fe(III)-montmorillonite. Oxidation and transformation of ferulic acid were more intense on the surface of Fe(III)-montmorillonite as compared to Fe(III) in solution due to stronger complexation on the Fe(III)-motnomrillonite surface. Our study demonstrate the importance of iron-enriched minerals for the abiotic formation of humic materials and for the transformation of aromatic (phenolic) pollutants.

Implementation and Validation of an Anisotropic Plasticity Model for Clay and a Two-Scale Micropolar Constitutive Model for Sand

NASA Astrophysics Data System (ADS)

Yonten, Karma

As a multi-phase material, soil exhibits highly nonlinear, anisotropic, and inelastic behavior. While it may be impractical for one constitutive model to address all features of the soil behavior, one can identify the essential aspects of the soil's stress-strainstrength response for a particular class of problems and develop a suitable constitutive model that captures those aspects. Here, attention is given to two important features of the soil stress-strain-strength behavior: anisotropy and post-failure response. An anisotropic soil plasticity model is implemented to investigate the significance of initial and induced anisotropy on the response of geo-structures founded on cohesive soils. The model is shown to produce realistic responses for a variety of over-consolidation ratios. Moreover, the performance of the model is assessed in a boundary value problem in which a cohesive soil is subjected to the weight of a newly constructed soil embankment. Significance of incorporating anisotropy is clearly demonstrated by comparing the results of the simulation using the model with those obtained by using an isotropic plasticity model. To investigate post-failure response of soils, the issue of strain localization in geostructures is considered. Post-failure analysis of geo-structures using numerical techniques such as mesh-based or mesh-free methods is often faced with convergence issues which may, at times, lead to incorrect failure mechanisms. This is due to the fact that majority of existing constitutive models are formulated within the framework of classical continuum mechanics that leads to ill-posed governing equations at the onset of localization. To overcome this challenge, a critical state two-surface plasticity model is extended to incorporate the micro-structural mechanisms that become significant within the shear band. The extended model is implemented to study the strain localization of granular soils in drained and undrained conditions. It is demonstrated that the extended model is capable of capturing salient features of soil behavior in pre- and post-failure regimes. The effects of soil particle size, initial density and confining pressure on the thickness and orientation of shear band are investigated and compared with the observed behavior of soils.

Microbiological assessment of the application of quicklime and limestone as a measure to stabilize the structure of compaction-prone soils

NASA Astrophysics Data System (ADS)

Deltedesco, Evi; Bauer, Lisa-Maria; Unterfrauner, Hans; Peticzka, Robert; Zehetner, Franz; Keiblinger, Katharina Maria

2014-05-01

Compaction of soils is caused by increasing mechanization of agriculture and forestry, construction of pipelines, surface mining and land recultivation. This results in degradation of aggregate stability and a decrease of pore space, esp. of macropores. It further impairs the water- and air permeability, and restricts the habitat of soil organisms. A promising approach to stabilize the structure and improve the permeability of soils is the addition of polyvalent ions like Ca2+ which can be added in form of quicklime (CaO) and limestone (CaCO3). In this study, we conducted a greenhouse pot experiment using these two different sources of calcium ions in order to evaluate their effect over time on physical properties and soil microbiology. We sampled silty and clayey soils from three different locations in Austria and incubated them with and without the liming materials (application 12.5 g) for 3 months in four replicates. In order to assess short-term and medium-term effects, soil samples were taken 2 days, 1 month and 3 months after application of quicklime and limestone, respectively. For these samples, we determined pH, bulk density, aggregate stability and water retention characteristics. Further, we measured microbiological parameters, such as potential enzyme activities (cellulase, phosphatase, chitinase, protease, phenoloxidase and peroxidase activity), PLFAs, microbial biomass carbon and nitrogen, dissolved organic carbon and nitrogen, nitrate nitrogen and ammonium nitrogen. In contrast to limestone, quicklime significantly improved soil aggregate stability in all tested soils only 2 days after application. Initially, soil pH was strongly increased by quicklime; however, after the second sampling (one month) the pH values of all tested soils returned to levels comparable to the soils treated with limestone. Our preliminary microbiological results show an immediate inhibition effect of quicklime on most potential hydrolytic enzyme activities and an increase in oxidative enzyme activities. These effects seem to be less pronounced in the medium term. In summary our results indicate, that the application of quicklime is a feasible measure for immediate stabilization of the structure of compaction-prone soils, showing only short-term impact on most microbial parameters.

Hydrologic and geochemical data collected near Skewed Reservoir, an impoundment for coal-bed natural gas produced water, Powder River Basin, Wyoming

USGS Publications Warehouse

Healy, Richard W.; Rice, Cynthia A.; Bartos, Timothy T.

2012-01-01

The Powder River Structural Basin is one of the largest producers of coal-bed natural gas (CBNG) in the United States. An important environmental concern in the Basin is the fate of groundwater that is extracted during CBNG production. Most of this produced water is disposed of in unlined surface impoundments. A 6-year study of groundwater flow and subsurface water and soil chemistry was conducted at one such impoundment, Skewed Reservoir. Hydrologic and geochemical data collected as part of that study are contained herein. Data include chemistry of groundwater obtained from a network of 21 monitoring wells and three suction lysimeters and chemical and physical properties of soil cores including chemistry of water/soil extracts, particle-size analyses, mineralogy, cation-exchange capacity, soil-water content, and total carbon and nitrogen content of soils.

GPR monitoring for non-uniform infiltration through a high permeable gravel layer in the test sand box

NASA Astrophysics Data System (ADS)

Kuroda, Seiichiro; Ishii, Nobuyuki; Morii, Toshihiro

2017-04-01

Recently capillary barriers have been known as a method to protect subsurface regions against infiltration from soil surface. It has essentially non-uniform structure of permeability or soil physical property. To identify the function of the capillary barrier, the site-characterization technique for non-uniform soil moisture distribution and infiltration process is needed. We built a sand box in which a thin high-permeable gravel layer was embedded and conducted a infiltration test, including non-uniform flow of soil water induced by capillary barrier effects. We monitored this process by various types of GPR measurements, including time-lapsed soundings with multi-frequency antenna and transmission measurements like one using cross-borehole radar. Finally we will discuss the applicability of GPR for monitoring the phenomena around the capillary barrier of soil. This work has partially supported by JSPS Grant-in-aid Scientific Research program, No.16H02580.

On inclusion of ecosystem services in the assessment of damage from land degradation

NASA Astrophysics Data System (ADS)

Tsvetnov, E. V.; Makarov, O. A.; Yakovlev, A. S.; Bondarenko, E. V.

2016-12-01

In the assessment of damage arising from land degradation at the Training and Experimental Soil-Ecological Center of Moscow State University, the cost of unfulfilled and underfulfilled ecosystem surfaces of soils should be taken into account. The following soil services were considered for the territory studied: direct provision with resources, protection, maintenance of ecosystem life and cultural services. A relationship between the concepts of ecosystem services and ecological functions of soils is shown. The concept of function is wider in some respect than the concept associated with it. In the definition of ecosystem service, only the manifestation of the soil function, which can have an economic interpretation, is selected. A simulation of ecosystem services proposed in the ecological and economic evaluation of damage arising from land degradation can be a real mechanism of nature conservation and development of systems of sustainable management at various levels of the administrative structure of the country.

Radon exhalation rates from some soil samples of Kharar, Punjab

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mehta, Vimal; Deptt of Physics, Punjabi University, Patiala- 147 001; Singh, Tejinder Pal, E-mail: tejinders03@gmail.com

Radon and its progeny are major contributors in the radiation dose received by general population of the world. Because radon is a noble gas, a large portion of it is free to migrate away from radium. The primary sources of radon in the houses are soils and rocks source emanations, emanation from building materials, and entry of radon into a structure from outdoor air. Keeping this in mind the study of radon exhalation rate from some soil samples of the Kharar, Punjab has been carried out using Can Technique. The equilibrium radon concentration in various soil samples of Kharar areamore » of district Mohali varied from 12.7 Bqm{sup −3} to 82.9 Bqm{sup −3} with an average of 37.5 ± 27.0 Bqm{sup −3}. The radon mass exhalation rates from the soil samples varied from 0.45 to 2.9 mBq/kg/h with an average of 1.4 ± 0.9 mBq/kg/h and radon surface exhalation rates varied from 10.4 to 67.2 mBq/m{sup 2}/h with an average of 30.6 ± 21.8 mBq/m{sup 2}/h. The radon mass and surface exhalation rates of the soil samples of Kharar, Punjab were lower than that of the world wide average.« less

Savanna Vegetation Dynamics and their Influence on Landscape-Scale C, N, and P Biogeochemistry

NASA Astrophysics Data System (ADS)

Boutton, T. W.; Zhou, Y.; Wu, X. B.; Hyodo, A.

2017-12-01

Soil carbon (C), nitrogen (N) and phosphorus (P) cycles are strongly interlinked and controlled through biological processes, and the P cycle is further controlled through geochemical processes. In grasslands, savannas, and other dryland ecosystems throughout the world, woody plant encroachment often modifies soil C, N, and P stores, although it remains unknown if these three elements change proportionally in response to this vegetation change. We evaluated proportional changes and spatial patterns of soil organic C (SOC), total N (TN), and total P (TP) following woody encroachment by taking spatially-explicit soil cores to a depth of 1.2 m across a subtropical savanna landscape which has undergone encroachment by trees and shrubs during the past century in the Rio Grande Plains, USA. SOC and TN were coupled with respect to increasing magnitudes and spatial patterns along the soil profile following woody encroachment. In contrast, TP increased slower than SOC and TN in surface soils, but faster in subsurface soils. Spatial patterns of TP strongly resembled those of vegetation cover throughout the soil profile, but differed from those of SOC and TN, especially in deeper portions of the profile. The encroachment of woody plants into this P-limited ecosystem resulted in the accumulation of proportionally less soil P compared to C and N in surface soils; however, proportionally more P accrued in deeper portions of the profile beneath woody patches where alkaline soil pH and high carbonate concentrations would favor precipitation of P as relatively insoluble calcium phosphates. Structural equation models (SEM) showed that fine root density explained the greatest proportion of variation in SOC, TN, and TP in the surface soil. In deeper portions of the profile, SEM showed that silt and clay explained much of the variation in SOC and TN, while soil pH strongly controlled TP. This imbalanced relationship highlights that the relative importance of biotic vs. abiotic mechanisms controlling C and N vs. P accumulation following vegetation change may vary with depth in the profile. Our findings suggest that efforts to incorporate the effects of land cover changes into coupled climate-biogeochemical models should attempt to represent C-N-P imbalances that may arise following vegetation change.

Results from twelve years of continuous monitoring of the soil CO2 flux at the Ketzin CO2 storage pilot site, Germany

NASA Astrophysics Data System (ADS)

Szizybalski, Alexandra; Zimmer, Martin; Pilz, Peter; Liebscher, Axel

2017-04-01

Under the coordination of the GFZ German Research Centre for Geosciences the complete life-cycle of a geological storage site for CO2 has been investigated and studied in detail over the past 12 years at Ketzin near Berlin, Germany. The test site is located at the southern flank of an anticlinal structure. Beginning with an exploration phase in 2004, drilling of the first three wells took place in 2007. From June 2008 to August 2013 about 67 kt of CO2 were injected into Upper Triassic sandstones at a depth of 630 to 650 m overlain by more than 165 m of shaley cap rocks. A comprehensive operational and scientific monitoring program forms the central part of the Ketzin project targeting at the reservoir itself, its overburden or above-zone and the surface. The surface monitoring is done by continuous soil CO2 flux measurements. These already started in 2005, more than three years prior to the injection phase using a survey chamber from LI-COR Inc. Twenty sampling locations were selected in the area of the anticline covering about 3 x 3 km. In order to obtain information on seasonal trends, measurements are performed at least once a month. The data set obtained prior to the injection serves as a basis for comparison with all further measurements during the injection and storage operations [Zimmer et al., 2010]. To refine the monitoring network, eight automatic, permanent soil CO2 flux stations were additionally installed in 2011 in the direct vicinity of the boreholes. Using this system, the CO2 soil flux is measured on an hourly basis. Over the whole monitoring time, soil temperature and moisture are recorded simultaneously and soil samples down to 70 cm depth were studied for their structure, carbon and nitrogen content. ver the whole monitoring time. Both, diurnal and seasonal flux variations can be detected and hence, provide a basis for interpretation of the measured data. Detailed analysis of the long-term monitoring at each station clearly reveals the influence of the soil composition. As most of the sampling positions are located next to agricultural roads and fields, the use of chemicals and harvesting may have an influence on the soil structure and the biology. Soil temperature, rain events and dry periods additionally affect the CO2 flux. Moreover, the microbial controlled increased CO2 production in early fall is also observed to depend on the actual location. Annual mean values of CO2 fluxes range from 10 to 82 t ha-1 a-1. As the CO2 flux measurements significantly reflect the specific site conditions, which can vary locally and over time, long-term trends must be carefully interpreted. Hence, complementary measurements of the soil gas composition were performed at selected locations. Zimmer, M., Pilz, P., Erzinger, J. (2011): Long-term surface carbon dioxide flux monitoring at the Ketzin carbon dioxide storage test site. Environmental Geosciences, 18, 119-130, doi:10.1306/eg.11181010017.

Composition and Maturity of Apollo 16 Regolith Core 60013/14

NASA Technical Reports Server (NTRS)

Korotev, Randy T.; Morris, Richard V.

1993-01-01

Samples from every half-centimeter dissection interval of double drive tube 60013/14 (sections 60013 and 60014) were analyzed by magnetic techniques for Fe concentration and surface maturity parameter I(sub s)/ Fe(O), and by neutron activation for concentrations of 25 lithophile and siderophile elements. Core 60013/14 is one of three regolith cores taken in a triangular array 40-50 m apart on the Cayley plains during Apollo 16 mission to the Moon. The core can be divided into three zones based both on I(sub s)/FeO and composition. Unit A (0-44 cm depth) is compositionally similar to other soils from the surface of the central region of the site and is mature throughout, although maturity decreases with depth. Unit B (44-59 cm) is submature and compositionally more feldspathic than Unit A. Regions of lowest maturity in Unit B are characterized by lower Sm/Sc ratios than any soil obtained from the Cayley plains as a result of some unidentified lithologic component with low surface maturity. The component is probably some type of mafic anorthosite that does not occur in such high abundance in any of the other returned soils. Unit C (59-62 cm) is more mature than Unit B and compositionally equivalent to an 87: 13 mixture of soil such as that from Unit A and plagioclase such as found in ferroan anorthosite. Similar soils, but containing greater abundances of anorthosite (plagioclase), are found at depth in the other two cores of the array. These units of immature to submature soil enriched to varying degrees (compared to the mature surface soil) in ferroan anorthosite consisting of approx. 99% plagioclase are the only compositionally distinct subsurface similarities among the three cores. Each of the cores contains other units that are compositionally dissimilar to any soil unit in the other two cores. These compositionally distinct units probably derive from local subsurface blocks deposited by the event(s) that formed the Cayley plains. The ferroan anorthosite with approx. 99% plagioclase, however, must represent some subsurface lithology that is significant on the scale of tens of meters. The compositional uniformity of the surface soil (0-10 cm depth) over distances of kilometers reflects the large-scale uniformity of the plains deposits; the fine- structure reflects small-scale nonuniformity and the inefficiency of the impact-mixing process at depths as shallow as even one meter.

The surface area of soil organic matter

USGS Publications Warehouse

Chiou, C.T.; Lee, J.-F.; Boyd, S.A.

1990-01-01

The previously reported surface area for soil organic matter (SOM) of 560-800 m2/g as determined by the ethylene glycol (EG) retention method was reexamined by the standard BET method based on nitrogen adsorption at liquid nitrogen temperature. Test samples consisted of two high organic content soils, a freeze-dried soil humic acid, and an oven-dried soil humic acid. The measured BET areas for these samples were less than 1 m2/g, except for the freeze-dried humic acid. The results suggest that surface adsorption of nonionic organic compounds by SOM is practically insignificant in comparison to uptake by partition. The discrepancy between the surface areas of SOM obtained by BET and EG methods was explained in terms of the 'free surface area' and the 'apparent surface area' associated with these measurements.The previously reported surface area for soil organic matter (SOM) of 560-800 m2/g as determined by the ethylene glycol (EG) retention method was reexamined by the standard BET method based on nitrogen adsorption at liquid nitrogen temperature. Test samples consisted of two high organic content soils, a freeze-dried soil humic acid, and an oven-dried soil humic acid. The measured BET areas for these samples were less than 1 m2/g, except for the freeze-dried humic acid. The results suggest that surface adsorption of nonionic organic compounds by SOM is practically insignificant in comparison to uptake by partition. The discrepancy between the surface areas of SOM obtained by BET and EG methods was explained in terms of the 'free surface area' and the 'apparent surface area' associated with these measurements.

Assessment of model behavior and acceptable forcing data uncertainty in the context of land surface soil moisture estimation

NASA Astrophysics Data System (ADS)

Dumedah, Gift; Walker, Jeffrey P.

2017-03-01

The sources of uncertainty in land surface models are numerous and varied, from inaccuracies in forcing data to uncertainties in model structure and parameterizations. Majority of these uncertainties are strongly tied to the overall makeup of the model, but the input forcing data set is independent with its accuracy usually defined by the monitoring or the observation system. The impact of input forcing data on model estimation accuracy has been collectively acknowledged to be significant, yet its quantification and the level of uncertainty that is acceptable in the context of the land surface model to obtain a competitive estimation remain mostly unknown. A better understanding is needed about how models respond to input forcing data and what changes in these forcing variables can be accommodated without deteriorating optimal estimation of the model. As a result, this study determines the level of forcing data uncertainty that is acceptable in the Joint UK Land Environment Simulator (JULES) to competitively estimate soil moisture in the Yanco area in south eastern Australia. The study employs hydro genomic mapping to examine the temporal evolution of model decision variables from an archive of values obtained from soil moisture data assimilation. The data assimilation (DA) was undertaken using the advanced Evolutionary Data Assimilation. Our findings show that the input forcing data have significant impact on model output, 35% in root mean square error (RMSE) for 5cm depth of soil moisture and 15% in RMSE for 15cm depth of soil moisture. This specific quantification is crucial to illustrate the significance of input forcing data spread. The acceptable uncertainty determined based on dominant pathway has been validated and shown to be reliable for all forcing variables, so as to provide optimal soil moisture. These findings are crucial for DA in order to account for uncertainties that are meaningful from the model standpoint. Moreover, our results point to a proper treatment of input forcing data in general land surface and hydrological model estimation.

A Comparison of delO18 Composition of Water Extracted from Suction Lysimeters, Centrifugation, and Azeotropic Distillation

NASA Astrophysics Data System (ADS)

Figueroa, A.; Tindall, J. A.; Friedel, M. J.

2005-12-01

Concentration of delO18 in water samples extracted by suction lysimeters is compared to samples obtained by methods of centrifugation and azeotropic distillation. Intact soil cores (30 cm diameter by 40 cm height) were extracted from two different sites. Site 1 was rapid infiltration basin number 50, near Altamonte Springs in Seminole County, Florida on properties belonging to the Walt Disney World Resort Complex. Site 2 was the Missouri Management System Evaluation Area (MSEA) near Centralia in Boone County, Missouri. The delO18 water was analyzed on a mass spectrophotometer. Potassium Bromide (KBr) was also used as a tracer and analyzed by ion chromatography. A portion of the data obtained was modeled using CXTFIT. Water collected by centrifugation and azeotropic distillation data were about 2-5% more negative than that collected by suction lysimeter values from the Florida (sandy) soil and about 5-7 % more negative from the Missouri (well structured clay) soil. Results indicate that the majority of soil water in well structured soil is strongly bound to soil grain surfaces and is not easily sampled by suction lysimeters. Also, it is plausible that evaporation caused some delO18 enrichment in the suction lysimeters. Suction lysimeters preferentially sampled water held at lower matric potentials, which may not represent total soil water. In cases where a sufficient volume of water has passed through the soil profile and displaced all previous pore water, suction lysimeters will however collect a representative sample of all the water at that depth interval. It is suggested that for stable isotope studies monitoring precipitation and soil water, suction lysimeters be installed at shallow depths (10 cm). Samples should also be coordinated with precipitation events. The CXTFIT program worked well for Florida soils (a more homogeneous sand), but gave poor performance for Missouri soils (well structured clays) except for deeper depths where clay structure was less variable. The data also suggest that each extraction method samples a separate component of soil-pore water. Consequently, centrifugation can be used with good success, particularly for efficient sampling of large areas. Azeotropic distillation is more appropriate when strict qualitative and quantitative data for desorption, desorption, and various types of kinetic studies are needed.

Why is SMOS Drier than the South Fork In-situ Soil Moisture Network?

NASA Astrophysics Data System (ADS)

Walker, V. A.; Hornbuckle, B. K.; Cosh, M. H.

2014-12-01

Global maps of near-surface soil moisture are currently being produced by the European Space Agency's Soil Moisture and Ocean Salinity (SMOS) satellite mission at 40 km. Within the next few months NASA's Soil Moisture Active Passive (SMAP) satellite mission will begin producing observations of near-surface soil moisture at 10 km. Near-surface soil moisture is the water content of the first 3 to 5 cm of the soil. Observations of near-surface soil moisture are expected to improve weather and climate forecasts. These satellite observations must be validated. We define validation as determining the space/time statistical characteristics of the uncertainty. A standard that has been used for satellite validation is in-situ measurements of near-surface soil moisture made with a network of sensors spanning the extent of a satellite footprint. Such a network of sensors has been established in the South Fork of the Iowa River in Central Iowa by the USDA ARS. Our analysis of data in 2013 indicates that SMOS has a dry bias: SMOS near-surface soil moisture is between 0.05 to 0.10 m^3m^{-3} lower than what is observed by the South Fork network. A dry bias in SMOS observations has also been observed in other regions of North America. There are many possible explanations for this difference: underestimation of vegetation, or soil surface roughness; undetected radio frequency interference (RFI); a retrieval model that is not appropriate for agricultural areas; or the use of an incorrect surface temperature in the retrieval process. We will begin our investigation by testing this last possibility: that SMOS is using a surface temperature that is too low which results in a drier soil moisture that compensates for this error. We will present a comparison of surface temperatures from the European Center for Medium-range Weather Forecasting (ECMWF) used to retrieve near-surface soil moisture from SMOS measurements of brightness temperature, and surface temperatures in the South Fork obtained from both tower and in-situ sensors. We will also use a long-term data set of tower and in-situ sensors collected in agricultural fields to develop a relationship between air temperature and the surface temperature relevant to the terrestrial microwave emission that is detected by SMOS.

Combined effect of capillary barrier and layered slope on water, solute and nanoparticle transfer in an unsaturated soil at lysimeter scale.

PubMed

Prédélus, Dieuseul; Coutinho, Artur Paiva; Lassabatere, Laurent; Bien, Le Binh; Winiarski, Thierry; Angulo-Jaramillo, Rafael

2015-10-01

It is well recognized that colloidal nanoparticles are highly mobile in soils and can facilitate the transport of contaminants through the vadose zone. This work presents the combined effect of the capillary barrier and soil layer slope on the transport of water, bromide and nanoparticles through an unsaturated soil. Experiments were performed in a lysimeter (1×1×1.6m(3)) called LUGH (Lysimeter for Urban Groundwater Hydrology). The LUGH has 15 outputs that identify the temporal and spatial evolution of water flow, solute flux and nanoparticles in relation to the soil surface conditions and the 3D system configuration. Two different soil structures were set up in the lysimeter. The first structure comprises a layer of sand (0-0.2cm, in diameter) 35cm thick placed horizontally above a layer of bimodal mixture also 35cm thick to create a capillary barrier at the interface between the sand and bimodal material. The bimodal material is composed of a mixture 50% by weight of sand and gravel (0.4-1.1cm, in diameter). The second structure, using the same amount of sand and bimodal mixture as the first structure represents an interface with a 25% slope. A 3D numerical model based on Richards equation for flow and the convection dispersion equations coupled with a mechanical module for nanoparticle trapping was developed. The results showed that under the effect of the capillary barrier, water accumulated at the interface of the two materials. The sloped structure deflects flow in contrast to the structure with zero slope. Approximately 80% of nanoparticles are retained in the lysimeter, with a greater retention at the interface of two materials. Finally, the model makes a good reproduction of physical mechanisms observed and appears to be a useful tool for identifying key processes leading to a better understanding of the effect of capillary barrier on nanoparticle transfer in an unsaturated heterogeneous soil. Copyright © 2015 Elsevier B.V. All rights reserved.

Soil heterogeneity in Mojave Desert shrublands: Biotic and abiotic processes

NASA Astrophysics Data System (ADS)

Caldwell, Todd G.; Young, Michael H.; McDonald, Eric V.; Zhu, Jianting

2012-09-01

Geological and ecological processes play critical roles in the evolution of desert piedmonts. Feedback between fast cyclic biotic and slow cumulative pedogenic processes on arid alluvial fan systems results in a heterogeneous landscape of interspace and canopy microsites. Defining the spatial extent between these processes will allow a better connection to ecosystem service and climate change. We use a soil chronosequence in the Mojave Desert and high spatial resolution infiltrometer measurements along transects radiating from canopies of perennial shrubs to assess the extent of biotic and abiotic processes and the heterogeneity of soil properties in arid shrublands. Results showed higher saturated conductivity under vegetation regardless of surface age, but it was more conspicuous on older, developed soils. At proximal locations to the shrub, bulk density, soil structure grade, silt, and clay content significantly increased radially from the canopy, while sand and organic material decreased. Soil properties at distal locations 2-5 times the canopy radius had no significant spatial correlation. The extent of the biotic influence of the shrub was 1.34 ± 0.32 times the canopy radius. Hydraulic properties were weakly correlated in space, but 75% of the variance could be attributed to sand content, soil structure grade, mean-particle diameter, and soil organic material, none of which are exclusively biotic or abiotic. The fast cyclic biotic processes occurring under vegetation are clearly overprinted on slow cumulative abiotic processes, resulting in the deterministic variability observed at the plant scale.

Estimating surface soil moisture from SMAP observations using a neural network technique

USDA-ARS?s Scientific Manuscript database

A Neural Network (NN) algorithm was developed to estimate global surface soil moisture for April 2015 to June 2016 with a 2-3 day repeat frequency using passive microwave observations from the Soil Moisture Active Passive (SMAP) satellite, surface soil temperatures from the NASA Goddard Earth Observ...

Soil strength response of select soil disturbance classes on a wet pine flat in South Carolina

Treesearch

Emily A. Carter; W. Michael Aust; James A. Burger

2007-01-01

Harvest operations conducted under conditions of high soil moisture on a et pine flat in South Carolina resulted in a high degree of soil surface disturbance. Less soil surface disturbance occurred when soil moisture content was lower. Soil strength varied by soil disturbance class in wet harvested locations and highly disturbed areas were associated with low soil...

Inoculation of soil native cyanobacteria to restore arid degraded soils

NASA Astrophysics Data System (ADS)

Raúl Román Fernández, José; Roncero Ramos, Beatriz; Chamizo de la Piedra, Sonia; Rodríguez Caballero, Emilio; Ángeles Muñoz Martín, M.; Mateo, Pilar; Cantón Castilla, Yolanda

2017-04-01

Restoration projects in semiarid lands often yield poor results. Water scarcity, low soil fertility, and poor soil structure strongly limit the survival and growth of planted seedlings in these areas. Under these conditions, a previous stage that improves edaphic conditions would turn out to a successful plant restoration. By successfully colonizing arid soils, cyanobacteria naturally provide suitable edaphic conditions, enhancing water availability, soil fertility and soil stability. Furthermore, cyanobacteria can be easily isolated and cultured ex-situ to produce high quantities of biomass, representing a potential tool to restore large areas efficiently. The objective of this study was to test the effect of inoculated cyanobacteria on degraded soils at three different semiarid areas from southeast Spain: Tabernas badlands, a limestone quarry located in Gádor, and grazed grassland in Las Amoladeras (Cabo de Gata). Soil native cyanobacteria belonging to three representative N-fixing genera (Nostoc, Scytonema and Tolypothrix) were isolated from such soils and cultured in BG110 medium. Each strain was inoculated (6 g m-2), separately and mixed (all in the same proportion), on Petri dishes with 80 g of each soil. Biocrust development was monitored during 3 months in these soils under laboratory conditions, at a constant temperature of 25oC. During the experiment, two irrigation treatments were applied simulating a dry (180 mm) and a wet (360 mm) rainfall year (average recorded in the study sites). After 3 months, net CO2 flux, spectral response and soil surface microtopography (1 mm spatial resolution) of inoculated and control soils was measured under wet conditions, all of them as a surrogate of biocrust development. Samples of the surface crust were collected in order to determine total soil organic carbon (SOC) content. The inoculated soils showed positive values of net CO2 flux, thus indicating a net CO2 uptake, whereas control soils showed CO2 fluxes closed to zero. This higher CO2 fixation in the inoculated soils was reflected in the higher SOC content found in these soils with respect to the non-inoculated soils. Soil surface roughness increased with biocrust development in the inoculated soils as compared to control soils. From the different treatments, soil inoculation with the mixture of the three strains promoted the highest SOC contents and absorbance at 680 nm (indicative of higher chlorophyll a content) on the three soil types. Therefore, using a consortium of cyanobacteria to inoculate degraded soils seems to be a more promising strategy to restore soils than inoculating individual species. Finally, differences between irrigation treatments were no significant, suggesting that water availability was not a key driver for cyanobacteria development under control laboratory conditions. Our results underline the viability of cyanobacteria inoculation to form an artificial developed biocrust that contribute to CO2 uptake and increase soil fertility which could facilitate further plant cover establishment. However, more studies are necessaries to test the effectiveness of inoculated crust development under field conditions.

Analysis shear wave velocity structure obtained from surface wave methods in Bornova, Izmir

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pamuk, Eren, E-mail: eren.pamuk@deu.edu.tr; Akgün, Mustafa, E-mail: mustafa.akgun@deu.edu.tr; Özdağ, Özkan Cevdet, E-mail: cevdet.ozdag@deu.edu.tr

2016-04-18

Properties of the soil from the bedrock is necessary to describe accurately and reliably for the reduction of earthquake damage. Because seismic waves change their amplitude and frequency content owing to acoustic impedance difference between soil and bedrock. Firstly, shear wave velocity and depth information of layers on bedrock is needed to detect this changing. Shear wave velocity can be obtained using inversion of Rayleigh wave dispersion curves obtained from surface wave methods (MASW- the Multichannel Analysis of Surface Waves, ReMi-Refraction Microtremor, SPAC-Spatial Autocorrelation). While research depth is limeted in active source study, a passive source methods are utilized formore » deep depth which is not reached using active source methods. ReMi method is used to determine layer thickness and velocity up to 100 m using seismic refraction measurement systems.The research carried out up to desired depth depending on radius using SPAC which is utilized easily in conditions that district using of seismic studies in the city. Vs profiles which are required to calculate deformations in under static and dynamic loads can be obtained with high resolution using combining rayleigh wave dispersion curve obtained from active and passive source methods. In the this study, Surface waves data were collected using the measurements of MASW, ReMi and SPAC at the İzmir Bornova region. Dispersion curves obtained from surface wave methods were combined in wide frequency band and Vs-depth profiles were obtained using inversion. Reliability of the resulting soil profiles were provided by comparison with theoretical transfer function obtained from soil paremeters and observed soil transfer function from Nakamura technique and by examination of fitting between these functions. Vs values are changed between 200-830 m/s and engineering bedrock (Vs>760 m/s) depth is approximately 150 m.« less

Land use and surface process domains on alpine hillslopes

NASA Astrophysics Data System (ADS)

Kuhn, Nikolaus J.; Caviezel, Chatrina; Hunziker, Matthias

2015-04-01

Shrubs and trees are generally considered to protect hillslopes from erosion. As a consequence, shrub encroachment on mountain pastures after abandoning grazing is not considered a threat to soils. However, the abandonment of mown or grazed grasslands causes a shift in vegetation composition and thus a change in landscape ecology and geomorphology. On many alpine slopes, current changes in land use and vegetation cover are accompanied by climate change, potentially generating a new geomorphic regime. Most of the debate focuses on the effect of land abandonment on water erosion rates. Generally, an established perennial vegetation cover improves the mechanical anchoring of the soil and the regulation of the soil water budget, including runoff generation and erosion. However, changing vegetation composition affects many other above- and below-ground properties like root density, -diversity and -geometry, soil structure, pore volume and acidity. Each combination of these properties can lead to a distinct scenario of dominating surface processes, often not reflected by common erosion risk assessment procedures. The study of soil properties along a chronosequence of green alder (alnusviridis) encroachment on the Unteralptal in central Switzerland reveals that shrub encroachment changes soil and vegetation properties towards an increase of resistance to run-off related erosion processes, but a decrease of slope stability against shallow landslides. The latter are a particular threat because of the currently increasing frequency of slide-triggering high magnitude rainfalls. The potential change of process domain on alpine pastures highlights the need for a careful use of erosion models when assessing future land use and climate scenarios. In mountains, but also other intensively managed agricultural landscapes, risk assessment without the appropriate reflection on the shifting relevance of surface processes carries the risk of missing future threats to environmental quality, services and hazards.

Habitat complexity influences fine scale hydrological processes and the incidence of stormwater runoff in managed urban ecosystems.

PubMed

Ossola, Alessandro; Hahs, Amy Kristin; Livesley, Stephen John

2015-08-15

Urban ecosystems have traditionally been considered to be pervious features of our cities. Their hydrological properties have largely been investigated at the landscape scale and in comparison with other urban land use types. However, hydrological properties can vary at smaller scales depending upon changes in soil, surface litter and vegetation components. Management practices can directly and indirectly affect each of these components and the overall habitat complexity, ultimately affecting hydrological processes. This study aims to investigate the influence that habitat components and habitat complexity have upon key hydrological processes and the implications for urban habitat management. Using a network of urban parks and remnant nature reserves in Melbourne, Australia, replicate plots representing three types of habitat complexity were established: low-complexity parks, high-complexity parks, and high-complexity remnants. Saturated soil hydraulic conductivity in low-complexity parks was an order of magnitude lower than that measured in the more complex habitat types, due to fewer soil macropores. Conversely, soil water holding capacity in low-complexity parks was significantly higher compared to the two more complex habitat types. Low-complexity parks would generate runoff during modest precipitation events, whereas high-complexity parks and remnants would be able to absorb the vast majority of rainfall events without generating runoff. Litter layers on the soil surface would absorb most of precipitation events in high-complexity parks and high-complexity remnants. To minimize the incidence of stormwater runoff from urban ecosystems, land managers could incrementally increase the complexity of habitat patches, by increasing canopy density and volume, preserving surface litter and maintaining soil macropore structure. Copyright © 2015 Elsevier Ltd. All rights reserved.

Study of microarthopod communities to assess soil quality in different managed vineyards

NASA Astrophysics Data System (ADS)

Gagnarli, E.; Goggioli, D.; Tarchi, F.; Guidi, S.; Nannelli, R.; Vignozzi, N.; Valboa, G.; Lottero, M. R.; Corino, L.; Simoni, S.

2015-01-01

Land use influences the abundance and diversity of soil arthropods. The evaluation of the impact of different management strategies on soil quality is increasingly requested. The determination of communities' structures of edaphic fauna can represent an efficient tool. In this study, in some vineyards in Piedmont (Italy), the effects of two different management systems, organic and integrated pest management (IPM), on soil biota were evaluated. As microarthropods living in soil surface are an important component of soil ecosystem interacting with all the other system components, a multi disciplinary approach was adopted by characterizing also some soil physical and chemical characteristics (soil texture, soil pH, total organic carbon, total nitrogen, calcium carbonate). Soil samplings were carried out on Winter 2011 and Spring 2012. All specimens were counted and determined up to the order level. The biological quality of the soil was defined through the determination of ecological indices, such as QBS-ar, species richness and indices of Shannon-Weaver, Pielou, Margalef and Simpson. The mesofauna abundance was affected by both the type of management and the soil texture. The analysis of microarthropod communities by QBS-ar showed higher values in organic than in IPM managed vineyards; in particular, the values registered in organic vineyards were similar to those characteristic of preserved soils.

Effects of forest conversion on soil microbial communities depend on soil layer on the eastern Tibetan Plateau of China.

PubMed

He, Ruoyang; Yang, Kaijun; Li, Zhijie; Schädler, Martin; Yang, Wanqin; Wu, Fuzhong; Tan, Bo; Zhang, Li; Xu, Zhenfeng

2017-01-01

Forest land-use changes have long been suggested to profoundly affect soil microbial communities. However, how forest type conversion influences soil microbial properties remains unclear in Tibetan boreal forests. The aim of this study was to explore variations of soil microbial profiles in the surface organic layer and subsurface mineral soil among three contrasting forests (natural coniferous forest, NF; secondary birch forest, SF and spruce plantation, PT). Soil microbial biomass, activity and community structure of the two layers were investigated by chloroform fumigation, substrate respiration and phospholipid fatty acid analysis (PLFA), respectively. In the organic layer, both NF and SF exhibited higher soil nutrient levels (carbon, nitrogen and phosphorus), microbial biomass carbon and nitrogen, microbial respiration, PLFA contents as compared to PT. However, the measured parameters in the mineral soils often did not differ following forest type conversion. Irrespective of forest types, the microbial indexes generally were greater in the organic layer than in the mineral soil. PLFAs biomarkers were significantly correlated with soil substrate pools. Taken together, forest land-use change remarkably altered microbial community in the organic layer but often did not affect them in the mineral soil. The microbial responses to forest land-use change depend on soil layer, with organic horizons being more sensitive to forest conversion.

Ekspansif soil solution in the villages at Trenggalek

NASA Astrophysics Data System (ADS)

Triastuti, Nusa Setiani

2017-11-01

District 2/3 hills with easy sliding and land survey results showed the soil because it consists of expansive soil Survey some villages who experience insatiability or failure, a secondary analysis of the data gathered from the expert on geology, Trenggalek geological map, Trenggalek geography. Ground location researched several villages, the Terbis village of focus discussion of the landslides and plan of relocation. In the watching a black. Colored soil and easily slide, showed very expansive soil due to montmorrelite. While soil relocation contour relative is more stable because the land of kaolin and invisible water sources that could push the land. Expansive soil in the village of solution should be cheap, easily obtainable, not damaging the fertility of the soil, groundwater should be awake to the source of life, ease of implementation, utilizing local materials and use modest tools and equipment. Under the soil surface do not get there water stored in the soil until deep the water because it will slide the ground. The analysis must meet the 7 items above and steady the contour. Design of building installed sub drain, the shallow bore foundations tied tie beam, floor plate into the unity of the structure.

Geographic variations of soil phosphorus induced by long-term land and manure nutrient management practices

NASA Astrophysics Data System (ADS)

Dao, Thanh

2014-05-01

Most natural and agricultural ecosystems are deficient in phosphorus (P), and supplemental P must be provided to attain optimal levels of agronomic production. Animal manure is often used to supply needed plant nutrients to enhance production of feed and fiber crops for human and livestock consumption. Soils have been treated with large amounts of P-enriched manure, and have shown elevated P levels in watersheds where there is a high density of intensive confined animal agriculture. Long-term additions can have lasting effects on the geographic distribution of soil microbes associated with the turnover of major soil nutrients, in particular non-mobile one such as P. We determined the distribution of soil P forms in a 10-ha no-till field that received annual additions of dairy manure at 0, 15, and 30 kg P ha-1 at the field scale for 16 consecutive years. Spectroscopic analyses of the near-surface zone were performed by X-ray fluorescence in soil cores taken to a depth of 0.2 m. Geostatistical methods were used to determine the spatial structure of the soil compositional data. Soil X-ray fluorescence spectral attributes were obtained based on a set of five parallel transects established across five experimental blocks, i.e., a 5 × 5 rectangular grid pattern. Three subsets of each soil attribute were identified for the three rates of manure addition. Long-term manure addition, albeit liquid manure, resulted in significant variability in soil P distribution in the near surface zone. The heterogeneity persisted over years of continuous no-tillage management. Therefore, a high density of geo-referenced soil measurements must be made to estimate the status of a required plant nutrient, especially a non-mobile nutrient in soil. A large number of timely measurements would require a rapid geo-referenced soil sensing spectroscopic method such as X-ray fluorescence to manage in near real-time the observed spatial variability of manure-treated fields.

Soil food web changes during spontaneous succession at post mining sites: a possible ecosystem engineering effect on food web organization?

PubMed

Frouz, Jan; Thébault, Elisa; Pižl, Václav; Adl, Sina; Cajthaml, Tomáš; Baldrián, Petr; Háněl, Ladislav; Starý, Josef; Tajovský, Karel; Materna, Jan; Nováková, Alena; de Ruiter, Peter C

2013-01-01

Parameters characterizing the structure of the decomposer food web, biomass of the soil microflora (bacteria and fungi) and soil micro-, meso- and macrofauna were studied at 14 non-reclaimed 1- 41-year-old post-mining sites near the town of Sokolov (Czech Republic). These observations on the decomposer food webs were compared with knowledge of vegetation and soil microstructure development from previous studies. The amount of carbon entering the food web increased with succession age in a similar way as the total amount of C in food web biomass and the number of functional groups in the food web. Connectance did not show any significant changes with succession age, however. In early stages of the succession, the bacterial channel dominated the food web. Later on, in shrub-dominated stands, the fungal channel took over. Even later, in the forest stage, the bacterial channel prevailed again. The best predictor of fungal bacterial ratio is thickness of fermentation layer. We argue that these changes correspond with changes in topsoil microstructure driven by a combination of plant organic matter input and engineering effects of earthworms. In early stages, soil is alkaline, and a discontinuous litter layer on the soil surface promotes bacterial biomass growth, so the bacterial food web channel can dominate. Litter accumulation on the soil surface supports the development of the fungal channel. In older stages, earthworms arrive, mix litter into the mineral soil and form an organo-mineral topsoil, which is beneficial for bacteria and enhances the bacterial food web channel.

Soil Food Web Changes during Spontaneous Succession at Post Mining Sites: A Possible Ecosystem Engineering Effect on Food Web Organization?

PubMed Central

Frouz, Jan; Thébault, Elisa; Pižl, Václav; Adl, Sina; Cajthaml, Tomáš; Baldrián, Petr; Háněl, Ladislav; Starý, Josef; Tajovský, Karel; Materna, Jan; Nováková, Alena; de Ruiter, Peter C.

2013-01-01

Parameters characterizing the structure of the decomposer food web, biomass of the soil microflora (bacteria and fungi) and soil micro-, meso- and macrofauna were studied at 14 non-reclaimed 1– 41-year-old post-mining sites near the town of Sokolov (Czech Republic). These observations on the decomposer food webs were compared with knowledge of vegetation and soil microstructure development from previous studies. The amount of carbon entering the food web increased with succession age in a similar way as the total amount of C in food web biomass and the number of functional groups in the food web. Connectance did not show any significant changes with succession age, however. In early stages of the succession, the bacterial channel dominated the food web. Later on, in shrub-dominated stands, the fungal channel took over. Even later, in the forest stage, the bacterial channel prevailed again. The best predictor of fungal bacterial ratio is thickness of fermentation layer. We argue that these changes correspond with changes in topsoil microstructure driven by a combination of plant organic matter input and engineering effects of earthworms. In early stages, soil is alkaline, and a discontinuous litter layer on the soil surface promotes bacterial biomass growth, so the bacterial food web channel can dominate. Litter accumulation on the soil surface supports the development of the fungal channel. In older stages, earthworms arrive, mix litter into the mineral soil and form an organo-mineral topsoil, which is beneficial for bacteria and enhances the bacterial food web channel. PMID:24260281

State Paths of Clay Dominated Soils of Coastal Marshland: Scale Effect and Hydrodynamic Behaviour

NASA Astrophysics Data System (ADS)

Tojo Radimy, Raymond; Dudoignon, Patrick

2017-12-01

The paper is focused on clayey dominated sediments of coastal marshes of the West Atlantic coast of France because of their homogeneity in texture and mineralogy, and their vertical structure evolution from dried and solid state in surface down to saturated plastic-to-liquid state in depth. It proposes a “review” of the complementary petrographic and hydromechanical data obtained on theses clay dominated soils and a method of calculation for the relationships prevailing between the hydro-mechanical properties and microstructure behaviour of the clay matrices. This tool, based on the shrinkage curve of the clay matrix is applied as aid to the hydraulic management of marshlands regarding the soil-plant interactions.

Can we manipulate root system architecture to control soil erosion?

NASA Astrophysics Data System (ADS)

Ola, A.; Dodd, I. C.; Quinton, J. N.

2015-03-01

Soil erosion is a major threat to soil functioning. The use of vegetation to control erosion has long been a topic for research. Much of this research has focused on the above ground properties of plants, demonstrating the important role that canopy structure and cover plays in the reduction of water erosion processes. Less attention has been paid to plant roots. Plant roots are a crucial yet under-researched factor for reducing water erosion through their ability to alter soil properties, such as aggregate stability, hydraulic function and shear strength. However, there have been few attempts to manipulate plant root system properties to reduce soil erosion. Therefore, this review aims to explore the effects that plant roots have on soil erosion and hydrological processes, and how plant root architecture might be manipulated to enhance its erosion control properties. We clearly demonstrate the importance of root system architecture for the control of soil erosion. We also demonstrate that some plant species respond to nutrient enriched patches by increasing lateral root proliferation. The soil response to root proliferation will depend upon its location: at the soil surface dense mats of roots may block soil pores thereby limiting infiltration, enhancing runoff and thus erosion; whereas at depth local increases in shear strength may reinforce soils against structural failure at the shear plane. Additionally, in nutrient deprived regions, root hair development may be stimulated and larger amounts of root exudates released, thereby improving aggregate stability and decreasing erodibility. Utilising nutrient placement at depth may represent a potentially new, easily implemented, management strategy on nutrient poor agricultural land or constructed slopes to control erosion, and further research in this area is needed.

Comparison of SWAT and GeoWEPP model in predicting the impact of stone bunds on runoff and erosion processes in the Northern Ethiopian Highlands

NASA Astrophysics Data System (ADS)

Demelash, Nigus; Flagler, Jared; Renschler, Chris; Strohmeier, Stefan; Holzmann, Hubert; Feras, Ziadat; Addis, Hailu; Zucca, Claudio; Bayu, Wondimu; Klik, Andreas

2017-04-01

Soil degradation is a major issue in the Ethiopian highlands which are most suitable for agriculture and, therefore, support a major part of human population and livestock. Heavy rainstorms during the rainy season in summer create soil erosion and runoff processes which affect soil fertility and food security. In the last years programs for soil conservation and afforestation were initiated by the Ethiopian government to reduce erosion risk, retain water in the landscape and improve crop yields. The study was done in two adjacent watersheds in the Northwestern highlands of Ethiopia. One of the watersheds is developed by soil and water conservation structures (stone bunds) in 2011 and the other one is without soil and water conservation structures. Spatial distribution of soil textures and other soil properties were determined in the field and in the laboratory and a soil map was derived. A land use map was evaluated based on satellite images and ground truth data. A Digital Elevation Model of the watershed was developed based on conventional terrestrial surveying using a total station. At the outlet of the watersheds weirs with cameras were installed to measure surface runoff. During each event runoff samples were collected and sediment concentration was analyzed. The objective of this study is 1) to assess the impact of stone bunds on runoff and erosion processes by using simulation models, and 2) to compare the performance of two soil erosion models in predicting the measurements. The selected erosion models were the Soil and Water Assessment Tool (SWAT) and the Geospatial Interface to the Water Erosion Prediction Project (GeoWEPP). The simulation models were calibrated/verified for the 2011-2013 periods and validated with 2014-2015 data. Results of this comparison will be presented.

Root architecture and wind-firmness of mature Pinus pinaster.

PubMed

Danjon, Frédéric; Fourcaud, Thierry; Bert, Didier

2005-11-01

This study aims to link three-dimensional coarse root architecture to tree stability in mature timber trees with an average of 1-m rooting depth. Undamaged and uprooted trees were sampled in a stand damaged by a storm. Root architecture was measured by three-dimensional (3-D) digitizing. The distribution of root volume by root type and in wind-oriented sectors was analysed. Mature Pinus pinaster root systems were organized in a rigid 'cage' composed of a taproot, the zone of rapid taper of horizontal surface roots and numerous sinkers and deep roots, imprisoning a large mass of soil and guyed by long horizontal surface roots. Key compartments for stability exhibited strong selective leeward or windward reinforcement. Uprooted trees showed a lower cage volume, a larger proportion of oblique and intermediate depth horizontal roots and less wind-oriented root reinforcement. Pinus pinaster stability on moderately deep soils is optimized through a typical rooting pattern and a considerable structural adaptation to the prevailing wind and soil profile.

Liquefaction and soil failure during 1994 northridge earthquake

USGS Publications Warehouse

Holzer, T.L.

1999-01-01

The 1994 Northridge, Calif., earthquake caused widespread permanent ground deformation on the gently sloping alluvial fan surface of the San Fernando Valley. The ground cracks and distributed deformation damaged both pipelines and surface structures. To evaluate the mechanism of soil failure, detailed subsurface investigations were conducted at four sites. Three sites are underlain by saturated sandy silts with low standard penetration test and cone penetration test values. These soils are similar to those that liquefied during the 1971 San Fernando earthquake, and are shown by widely used empirical relationships to be susceptible to liquefaction. The remaining site is underlain by saturated clay whose undrained shear strength is approximately half the value of the earthquake-induced shear stress at this location. This study demonstrates that the heterogeneous nature of alluvial fan sediments in combination with variations in the ground-water table can be responsible for complex patterns of permanent ground deformation. It may also help to explain some of the spatial variability of strong ground motion observed during the 1994 earthquake. ?? ASCE,.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reardon, Patrick N.; Chacon, Stephany S.; Walter, Eric D.

Proteins facilitate a wide range of chemical transformations important in soil as well as being a major reservoir of soil nitrogen themselves. The interactions and reactions of proteins with soils and minerals are of key importance to our understanding of their functional persistence in the environment. We combined NMR and EPR spectroscopies to distinguish the reaction of a model protein with a redox active mineral surface (Birnessite, MnO 2) from its response to a redox neutral phyllosilicate (Kaolinite). Our data demonstrate that birnessite fragments the model protein while kaolinite has little impact on the protein structure. NMR and EPR spectroscopiesmore » are shown to be valuable tools to observe these reactions and capture the extent of protein transformation together with the extent of mineral response. These data suggest that mineral surfaces can have both promoting and retarding roles in terrestrial nitrogen cycling, with redox active minerals acting as accelerators by catalyzing the breakdown of proteins and proteinaceous materials while phyllosilicates are more likely to act as preservative media.« less

SMERGE: A multi-decadal root-zone soil moisture product for CONUS

NASA Astrophysics Data System (ADS)

Crow, W. T.; Dong, J.; Tobin, K. J.; Torres, R.

2017-12-01

Multi-decadal root-zone soil moisture products are of value for a range of water resource and climate applications. The NASA-funded root-zone soil moisture merging project (SMERGE) seeks to develop such products through the optimal merging of land surface model predictions with surface soil moisture retrievals acquired from multi-sensor remote sensing products. This presentation will describe the creation and validation of a daily, multi-decadal (1979-2015), vertically-integrated (both surface to 40 cm and surface to 100 cm), 0.125-degree root-zone product over the contiguous United States (CONUS). The modeling backbone of the system is based on hourly root-zone soil moisture simulations generated by the Noah model (v3.2) operating within the North American Land Data Assimilation System (NLDAS-2). Remotely-sensed surface soil moisture retrievals are taken from the multi-sensor European Space Agency Climate Change Initiative soil moisture data set (ESA CCI SM). In particular, the talk will detail: 1) the exponential smoothing approach used to convert surface ESA CCI SM retrievals into root-zone soil moisture estimates, 2) the averaging technique applied to merge (temporally-sporadic) remotely-sensed with (continuous) NLDAS-2 land surface model estimates of root-zone soil moisture into the unified SMERGE product, and 3) the validation of the SMERGE product using long-term, ground-based soil moisture datasets available within CONUS.

Seed reserves diluted during surface soil reclamation in eastern Mojave Desert

USGS Publications Warehouse

Scoles-Sciulla, S. J.; DeFalco, L.A.

2009-01-01

Surface soil reclamation is used to increase the re-establishment of native vegetation following disturbance through preservation and eventual replacement of the indigenous seed reserves. Employed widely in the mining industry, soil reclamation has had variable success in re-establishing native vegetation in arid and semi-arid regions. We tested whether variable success could be due in part to a decrease of seed reserves during the reclamation process by measuring the change in abundance of germinable seed when surface soil was mechanically collected, stored in a soil pile for 4 months, and reapplied upon completion of a roadway. Overall seed reserve declines amounted to 86% of the original germinable seed in the soil. The greatest decrease in seed reserves occurred during soil collection (79% of original reserves), compared to the storage and reapplication stages. At nearby sites where stored surface soil had been reapplied, no perennial plant cover occurred from 0.5 to 5 years after application and <1% cover after 7 years compared to 5% cover in nearby undisturbed areas. The reduction in abundance of germinable seed during reclamation was primarily due to dilution of seed reserves when deeper soil fractions without seed were mixed with the surface soil during collection. Unless more precise techniques of surface soil collection are utilized, soil reclamation alone as a means for preserving native seed reserves is a method ill-suited for revegetating disturbed soils with a shallow seed bank, such as those found in the Mojave Desert. Copyright ?? Taylor & Francis Group, LLC.

Accumulation of Polycyclic Aromatic Hydrocarbons in Soils and Mosses of Southern Tundra at Different Distances from the Thermal Power Plant

NASA Astrophysics Data System (ADS)

Yakovleva, E. V.; Gabov, D. N.; Beznosikov, V. A.; Kondratenok, B. M.

2018-05-01

A number of polycyclic aromatic hydrocarbon (PAH) structures have been identified in organic horizons of surface-gley tundra soils (Stagnic Cambisols) and the moss Pleurozium schreberi. The total content of polyarenes in soils and P. schreberi exceeds the background values in 3.5-5 times. A tendency of increasing content of polyarenes with the distance from the source to 1 km has been revealed. High coefficients of variation have been found between the contents of PAHs in snow cover, organic soil horizons, and mosses. Light hydrocarbons dominate in the composition of PAHs from the snow and ground covers and mosses. Naphthalene dominates on the surface of mosses in all of the studied plots, which is largely related to its intensive uptake by mosses under pollution conditions. It has been found that when the input of polyarenes onto the surface of tundra phytocenoses increases, the bioaccumulation of PAHs by P. schreberi is intensified, and PAHs begin to penetrate into moss. The increase in the concentration of high-molecularweight polyarenes in the environment plays the key role in the activation of PAH bioaccumulation by moss. It has been shown that P. schreberi can be used as an indicator species for monitoring the contamination of tundra phytocenoses by polyarenes. Both living and dead parts of P. schreberi are suitable for the environmental monitoring of PAH contamination.

Water on Mars: Evidence from MER Mission Results

NASA Technical Reports Server (NTRS)

Landis, Geoffrey A.

2004-01-01

The Viking and the Mars Exploration Rover missions observed that the surface of Mars is encrusted by a thinly cemented layer, or "duricrust". Elemental analyzes at five sites on Mars show that these soils have sulfur content and chlorine content consistent with the presence of sulfates and halides as mineral cements. The soil is highly enriched in the salt-forming elements compared with rock. Analysis of the soil cementation indicates some features which may be evidence of liquid water. At both MER sites, duricrust textures revealed by the Microscopic Imager show features including the presence of fine sand-sized grains, some of which may be aggregates of fine silt and clay, surrounded by a pervasive light colored material that is associated with microtubular structures and networks of microfractures. Stereo views of undisturbed duricrust surfaces reveal rugged microrelief between 2-3 mm and minimal loose material. Comparisons of microscopic images of duricrust soils obtain before and after placement of the Mossbauer spectrometer indicate differing degrees of compaction and cementation. Two models of a transient water hypothesis are offered, a "top down" hypothesis that emphasizes the surface deposition of frost, melting and downward migration of liquid water and a "bottom up" alternative that proposes the presence of interstitial ice/brine, with the upward capillary migration of liquid water. The viability of both of these models ultimately hinges on the availability of seasonally transient liquid water for brief periods.

Scale and processes dominating soil erosion and sediment transport: case studies from Indonesia and Australia

NASA Astrophysics Data System (ADS)

van Dijk, A. I. J. M.; Bruijnzeel, L. A.

2009-04-01

Soil erosion and sediment transport at different scales of space and time are dominated by a variable set of landscape properties and processes. Research results from West Java (Indonesia) and southeast Australia are presented, taking a natural resources management perspective. The dominant role of vegetation and soil health, rainfall infiltration, and connectivity between hillslope and stream are elaborated on. In humid volcanic upland West Java, vegetative cover and associated infiltration capacity are the dominant control on surface runoff and sediment generation, with additional variation attributed to slope and soil surface structure. Use of process models to replicate and upscale field measurements highlighted that a predictive theory to link vegetative cover and infiltration capacity is lacking, and that full knowledge of the covariance between terrain attributes that promote sediment generation is needed for process based modelling. At the hillslope to catchment scale, slope gradient and a less erodible substrate became additional constraints on sediment yield. A conceptual framework relating processes, scale and sediment delivery ratio was developed. In water-limited southeast Australia, measures to reduce erosion and sediment production generally aim to intercept surface runoff, allowing runoff to infiltrate and sediment to settle on vegetated buffer strips or roadsides or in leaky dams. It is illustrated how remote sensing can help to assess the sources of sediment and hydrological connectivity at different scales and to identify opportunities for mitigation.

Range Condition Assessment Report for Naval Surface Warfare Center, Dahlgren Laboratory Ranges, Dahlgren, Virginia

DTIC Science & Technology

2010-09-01

following alternative: vegetative soil cap, offsite disposal of sediments, and phytoremediation to control groundwater levels beneath the landfill. The...cap. These issues include poor condition of the phytoremediation trees on the surface of the landfill cap and blockage of the pond outfall structure...to be completed in January 2009. Based on the poor condition of the phytoremediation trees on the landfill cap, a supplemental tree planting

Estimation of surface soil moisture and roughness from multi-angular ASAR imagery in the Watershed Allied Telemetry Experimental Research (WATER)

NASA Astrophysics Data System (ADS)

Wang, S. G.; Li, X.; Han, X. J.; Jin, R.

2010-06-01

Radar remote sensing has demonstrated its applicability to the retrieval of basin-scale soil moisture. The mechanism of radar backscattering from soils is complicated and strongly influenced by surface roughness. Furthermore, retrieval of soil moisture using AIEM-like models is a classic example of the underdetermined problem due to a lack of credible known soil roughness distributions at a regional scale. Characterization of this roughness is therefore crucial for an accurate derivation of soil moisture based on backscattering models. This study aims to directly obtain surface roughness information along with soil moisture from multi-angular ASAR images. The method first used a semi-empirical relationship that connects the roughness slope (Zs) and the difference in backscattering coefficient (Δσ) from ASAR data in different incidence angles, in combination with an optimal calibration form consisting of two roughness parameters (the standard deviation of surface height and the correlation length), to estimate the roughness parameters. The deduced surface roughness was then used in the AIEM model for the retrieval of soil moisture. An evaluation of the proposed method was performed in a grassland site in the middle stream of the Heihe River Basin, where the Watershed Allied Telemetry Experimental Research (WATER) was taken place. It has demonstrated that the method is feasible to achieve reliable estimation of soil water content. The key challenge to surface soil moisture retrieval is the presence of vegetation cover, which significantly impacts the estimates of surface roughness and soil moisture.

Role of organic matter on aggregate stability and related mechanisms through organic amendments

NASA Astrophysics Data System (ADS)

Zaher, Hafida

2010-05-01

To date, only a few studies have tried to simultaneously compare the role of neutral and uronic sugars and lipids on soil structural stability. Moreover, evidence for the mechanisms involved has often been established following wetting of moist aggregates after various pre-treatments thus altering aggregate structure and resulting in manipulations on altered aggregates on which the rapid wetting process may not be involved anymore. To the best of our knowledge, the objective of this work was to study the role of neutral and uronic sugars and lipids in affecting key mechanisms (swelling rate, pressure evolution) involved in the stabilization of soil structure. A long-term incubation study (48-wk) was performed on a clay loam and a silty-clay loam amended with de-inking-secondary sludge mix at three rates (8, 16 and 24 Mg dry matter ha-1), primary-secondary sludge mix at one rate (18 Mg oven-dry ha-1) and composted de-inking sludge at one rate (24 Mg ha-1). Different structural stability indices (stability of moist and dry aggregates, the amount of dispersible clay and loss of soil material following sudden wetting) were measured on a regular basis during the incubation, along with CO2 evolved, neutral and uronic sugar, and lipid contents. During the course of the incubations, significant increases in all stability indices were measured for both soil types. In general, the improvements in stability were proportional to the amount of C added as organic amendments. These improvements were linked to a very intense phase of C mineralization and associated with increases in neutral and uronic sugars as well as lipid contents. The statistical relationships found between the different carbonaceous fractions and stability indices were all highly significant and indicated no clear superiority of one fraction over another. Paper sludge amendments also resulted in significant decreases in maximum internal pressure of aggregate and aggregate swelling following immersion in water, two mechanisms affecting structural stability. Overall, the results suggest that reduction in maximum internal pressure induced by organic amendments most likely resulted from increases in pore surface roughness and pore occlusion rather than by increase in surface wetting angles. This study also supports the view of a non specific action of the lipids, neutral and uronic sugars on aggregate stability to rapid wetting. Key words: soil aggregate stability, polysaccharides, lipids, mechanisms, organic matter

Assimilation of Passive and Active Microwave Soil Moisture Retrievals

NASA Technical Reports Server (NTRS)

Draper, C. S.; Reichle, R. H.; DeLannoy, G. J. M.; Liu, Q.

2012-01-01

Root-zone soil moisture is an important control over the partition of land surface energy and moisture, and the assimilation of remotely sensed near-surface soil moisture has been shown to improve model profile soil moisture [1]. To date, efforts to assimilate remotely sensed near-surface soil moisture at large scales have focused on soil moisture derived from the passive microwave Advanced Microwave Scanning Radiometer (AMSR-E) and the active Advanced Scatterometer (ASCAT; together with its predecessor on the European Remote Sensing satellites (ERS. The assimilation of passive and active microwave soil moisture observations has not yet been directly compared, and so this study compares the impact of assimilating ASCAT and AMSR-E soil moisture data, both separately and together. Since the soil moisture retrieval skill from active and passive microwave data is thought to differ according to surface characteristics [2], the impact of each assimilation on the model soil moisture skill is assessed according to land cover type, by comparison to in situ soil moisture observations.

Physical properties, structure, and shape of radioactive Cs from the Fukushima Daiichi Nuclear Power Plant accident derived from soil, bamboo and shiitake mushroom measurements.

PubMed

Niimura, Nobuo; Kikuchi, Kenji; Tuyen, Ninh Duc; Komatsuzaki, Masakazu; Motohashi, Yoshinobu

2015-01-01

We conducted an elution experiment with contaminated soils using various aqueous reagent solutions and autoradiography measurements of contaminated bamboo shoots and shiitake mushrooms to determine the physical and chemical characteristics of radioactive Cs from the Fukushima Daiichi Nuclear Power Plant accident. Based on our study results and data in the literature, we conclude that the active Cs emitted by the accident fell to the ground as granular non-ionic materials. Therefore, they were not adsorbed or trapped by minerals in the soil, but instead physically adhere to the rough surfaces of the soil mineral particles. Granular Cs* can be transferred among media, such as soils and plants. The physical properties and dynamic behavior of the granular Cs* is expected to be helpful in considering methods for decontamination of soil, litter, and other media. Copyright © 2013 The Authors. Published by Elsevier Ltd.. All rights reserved.