Soil Water Availability Modulation Over Estimated Relative Yield Losses in Wheat (Triticum aestivum L.) Due to Ozone Exposure

PubMed Central

De la Torre, Daniel; Sierra, Maria Jose

2007-01-01

The approach developed by Fuhrer in 1995 to estimate wheat yield losses induced by ozone and modulated by the soil water content (SWC) was applied to the data on Catalonian wheat yields. The aim of our work was to apply this approach and adjust it to Mediterranean environmental conditions by means of the necessary corrections. The main objective pursued was to prove the importance of soil water availability in the estimation of relative wheat yield losses as a factor that modifies the effects of tropospheric ozone on wheat, and to develop the algorithms required for the estimation of relative yield losses, adapted to the Mediterranean environmental conditions. The results show that this is an easy way to estimate relative yield losses just using meteorological data, without using ozone fluxes, which are much more difficult to calculate. Soil water availability is very important as a modulating factor of the effects of ozone on wheat; when soil water availability decreases, almost twice the amount of accumulated exposure to ozone is required to induce the same percentage of yield loss as in years when soil water availability is high. PMID:17619747

Soil Physicochemical and Biological Properties of Paddy-Upland Rotation: A Review

PubMed Central

Lv, Teng-Fei; Chen, Yong; Westby, Anthony P.; Ren, Wan-Jun

2014-01-01

Paddy-upland rotation is an unavoidable cropping system for Asia to meet the increasing demand for food. The reduction in grain yields has increased the research interest on the soil properties of rice-based cropping systems. Paddy-upland rotation fields are unique from other wetland or upland soils, because they are associated with frequent cycling between wetting and drying under anaerobic and aerobic conditions; such rotations affect the soil C and N cycles, make the chemical speciation and biological effectiveness of soil nutrient elements varied with seasons, increase the diversity of soil organisms, and make the soil physical properties more difficult to analyze. Consequently, maintaining or improving soil quality at a desirable level has become a complicated issue. Therefore, fully understanding the soil characteristics of paddy-upland rotation is necessary for the sustainable development of the system. In this paper, we offer helpful insight into the effect of rice-upland combinations on the soil chemical, physical, and biological properties, which could provide guidance for reasonable cultivation management measures and contribute to the improvement of soil quality and crop yield. PMID:24995366

Comparison of evaporative fluxes from porous surfaces resolved by remotely sensed and in-situ temperature and soil moisture data

NASA Astrophysics Data System (ADS)

Wallen, B.; Trautz, A.; Smits, K. M.

2014-12-01

The estimation of evaporation has important implications in modeling climate at the regional and global scale, the hydrological cycle and estimating environmental stress on agricultural systems. In field and laboratory studies, remote sensing and in-situ techniques are used to collect thermal and soil moisture data of the soil surface and subsurface which is then used to estimate evaporative fluxes, oftentimes using the sensible heat balance method. Nonetheless, few studies exist that compare the methods due to limited data availability and the complexity of many of the techniques, making it difficult to understand flux estimates. This work compares different methods used to quantify evaporative flux based on remotely sensed and in-situ temperature and soil moisture data. A series of four laboratory experiments were performed under ambient and elevated air temperature conditions with homogeneous and heterogeneous soil configurations in a small two-dimensional soil tank interfaced with a small wind tunnel apparatus. The soil tank and wind tunnel were outfitted with a suite of sensors that measured soil temperature (surface and subsurface), air temperature, soil moisture, and tank weight. Air and soil temperature measurements were obtained using infrared thermography, heat pulse sensors and thermistors. Spatial and temporal thermal data were numerically inverted to obtain the evaporative flux. These values were then compared with rates of mass loss from direct weighing of the samples. Results demonstrate the applicability of different methods under different surface boundary conditions; no one method was deemed most applicable under every condition. Infrared thermography combined with the sensible heat balance method was best able to determine evaporative fluxes under stage 1 conditions while distributed temperature sensing combined with the sensible heat balance method best determined stage 2 evaporation. The approaches that appear most promising for determining the surface energy balance incorporates soil moisture rate of change over time and atmospheric conditions immediately above the soil surface. An understanding of the fidelity regarding predicted evaporation rates based upon stages of evaporation enables a more deliberate selection of the suite of sensors required for data collection.

Enhancement of acid phosphatase secretion and Pi acquisition in Suaeda fruticosa on calcareous soil by high saline level.

PubMed

Labidi, Nehla; Snoussi, Sana; Ammari, Manel; Metoui, Wissal; Ben Yousfi, N; Hamrouni, Lamia; Abdelly, C

2010-12-01

The aim of this study was to identify the relationship between the adaptive processes of Suaeda fruticosa for Pi acquisition and the physic-chemical and biological characteristics of two soil types under moderate and high saline conditions. Four treatments were established in pots: namely SS100, SS600, CS100 and CS600 where SS stood for sandy soil and CS for calcareous soil, and the indexes 100 and 600 were NaCl concentrations (mM) in irrigation distilled water. Assuming that Pi per g of plant biomass is an indicator of plant efficiency for P acquisition, the results showed that Pi acquisition was easiest on SS100 and was difficult on CS100. The differences in Pi acquisition between plants on SS100 and CS100 could be attributed to the low root surface area (-30%) and to the low alkaline phosphatases (Pases) activities (-50%) in calcareous rhizospheric soil. The high salinity level had no effect on the efficiency of P acquisition on SS but increased this parameter on CS (+50%). In the latter soil type, high acid phosphatase activities were observed in rhizospheric soil at high salinity level. Acid phosphatase seemed to be secreted from the roots. The higher secretion of acid phosphatase in this soil was related to the root lipid peroxidation in response to elevated salinity associated with the augmentation of unsaturated acids which might induce an oxidative damage of the root membrane. Thus we can conclude that in deficient soil such as calcareous, the efficiency of P acquisition in S. fruticosa which was difficult at moderate salinity level can be enhanced by high salinity level.

A soil-plate based pipeline for assessing cereal root growth in response to polyethylene glycol (PEG)-induced water deficit stress

USDA-ARS?s Scientific Manuscript database

Drought is a serious problem that causes losses in crop-yield every year, but the mechanisms underlying how roots respond to water deficit are difficult to study under controlled conditions. Methods for assaying root elongation and architecture, especially for seedlings, are commonly achieved on ar...

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.

Affect of dairy cow manure, urine, and slurry on N<2>O, CO<2>, and CH<4> emissions from Pasture

NASA Astrophysics Data System (ADS)

Dorich, C.; Varner, R. K.; Contosta, A.; Li, C.

2012-12-01

Agriculture is responsible for roughly 25% of total anthropogenic emission of greenhouse gases (GHG) globally. These agricultural emissions are primarily in the form of methane (CH<4>) and nitrous oxide (N<2>O) where they account for roughly 40 and 80 percent of anthropogenic emissions of their gas, respectively. Measuring and modeling of these gases has remained difficult however as management varies between farms and N<2>O fluxes have been difficult to link to climate and site conditions. Most of these N<2>O fluxes occur during soil freeze-thaw and wetting-drying cycles as well as fertilizer addition moments, all of which are difficult to measure and harder yet to model. Thus the N<2>O flux remains poorly understood and may be underestimated in literature. This provides a problem in agriculture emissions as N use efficiency has been suggested as a proxy for farm scale emissions. On a farm scale these large fluxes of N<2>O from soil "hot moments" can account for up to 60% of the total GHG emissions and thus it is essential to capture the full flux. At the University of New Hampshire Agriculture Experiment Station's (NHAES) organic dairy farm a manure fertilizer experiment was conducted. Manure, urine, and slurry from the UNH dairy farms were collected, analyzed, and applied to pasture plots in May 2012 in order to examine N<2>O flux hot moments. Sites were measured at least bi-weekly with manual static flux chambers taken with soil temperature and moisture along with measurements for soil inorganic N, soil C:N, plant biomass and C:N, and soil pH. Gas samples were analyzed for CO<2>, CH<4>, and N<2>O. Emissions were compared with other fluxes from the farm ecosystem including; corn silage, free stall bedding, composting and solid manure, and a manure slurry tank.

Soil erosion and effluent particle size distribution under different initial conditions and rock fragment coverage

NASA Astrophysics Data System (ADS)

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

2012-04-01

It is well known that the presence of rock fragments on the soil surface and the soil's initial characteristics (moisture content, surface roughness, bulk density, etc.) are key factors influencing soil erosion dynamics and sediment delivery. In addition, the interaction of these factors increases the complexity of soil erosion patterns and makes predictions more difficult. The aim of this study was (i) to investigate the effect of soil initial conditions and rock fragment coverage on soil erosion yields and effluent particle size distribution and (ii) to evaluate to what extent the rock fragment coverage controls this relationship. Three laboratory flume experiments with constant precipitation rate of 74 mm/h on a loamy soil parcel with a 2% slope were performed. Experiments with duration of 2 h were conducted using the 6-m × 2-m EPFL erosion flume. During each experiment two conditions were considered, a bare soil and a rock fragment-protected (with 40% coverage) soil. The initial soil surface state was varied between the three experiments, from a freshly re-ploughed and almost dry condition to a compacted soil with a well-developed shield layer and high moisture content. Experiments were designed so that rain splash was the primary driver of soil erosion. Results showed that the amount of eroded mass was highly controlled by the initial soil conditions and whether the steady-state equilibrium was un-, partially- or fully- developed during the previous event. Additionally, results revealed that sediment yields and particle size composition in the initial part of an erosion event are more sensitive to the erosion history than the long-time behaviour. This latter appears to be mainly controlled by rainfall intensity. If steady-state was achieved for a previous event, then the next event consistently produced concentrations for each size class that peaked rapidly, and then declined gradually to steady-state equilibrium. If steady state was not obtained, then different and more complex behaviour was observed in the next event, with large differences found between fine, medium and coarse size classes. The presence of rock fragments on the topsoil reduced the time needed to reach steady state compared with the bare soil. This was attributed to the reduction of rain splash erosion caused by the rapid development of the overland flow, as a result of rock fragments reducing the flow cross-sectional area.

Modeling Recharge - can it be Done?

NASA Astrophysics Data System (ADS)

Verburg, K.; Bond, W. J.; Smith, C. J.; Dunin, F. X.

2001-12-01

In sub-humid areas where rainfall is relatively low and sporadic, recharge (defined as water movement beyond the active root zone) is the small difference between the much larger numbers rainfall and evapotranspiration. It is very difficult to measure and often modeling is resorted to instead. But is modeling this small number any less difficult than measurement? In Australia there is considerable debate over the magnitude of recharge under different agricultural systems because of its contribution to rising saline groundwater levels following the clearing of native vegetation in the last 100 years. Hence the adequacy of measured and modeled estimates of recharge is under close scrutiny. Results will be presented for the water balance of an intensively monitored 8 year sequence of crops and pastures. Measurements included meteorological inputs, evapotranspiration measured with a pair of weighing lysimeters, and soil water content was measured with TDR and neutron moisture meter. Recharge was estimated from the percolate removed from the lysimeters as well as, when conditions were suitable, from soil water measurements and combined soil water and evapotranspiration measurements. This data was simulated using a comprehensive soil-plant-atmosphere model (APSIM). Comparison with field measurements shows that the recharge can be simulated with an accuracy similar to that with which it can be measured. However, is either sufficiently accurate for the applications for which they are required?

Evaporation from soils subjected to natural boundary conditions at the land-atmospheric interface

NASA Astrophysics Data System (ADS)

Smits, K.; Illngasekare, T.; Ngo, V.; Cihan, A.

2012-04-01

Bare soil evaporation is a key process for water exchange between the land and the atmosphere and an important component of the water balance in semiarid and arid regions. However, there is no agreement on the best methodology to determine evaporation under different boundary conditions at the land surface. This becomes critical in developing models that couples land to the atmosphere. Because it is difficult to measure evaporation from soil, with the exception of using lysimeters, numerous formulations have been proposed to establish a relationship between the rate of evaporation and soil moisture and/or soil temperature and thermal properties. Different formulations vary in how they partition available energy. A need exists to systematically compare existing methods to experimental data under highly controlled conditions not achievable in the field. The goal of this work is to perform controlled experiments under transient conditions of soil moisture, temperature and wind at the land/atmospheric interface to test different conceptual and mathematical formulations for the soil surface boundary conditions to develop appropriate numerical models to be used in simulations. In this study, to better understand the coupled water-vapor-heat flow processes in the shallow subsurface near the land surface, we modified a previously developed theory by Smits et al. [2011] that allows non-equilibrium liquid/gas phase change with gas phase vapor diffusion to better account for dry soil conditions. The model did not implement fitting parameters such as a vapor enhancement factor that is commonly introduced into the vapor diffusion coefficient as an arbitrary multiplication factor. In order to experimentally test the numerical formulations/code, we performed a two-dimensional physical model experiment under varying boundary conditions using test sand for which the hydraulic and thermal properties were well characterized. Precision data under well-controlled transient heat and wind boundary conditions was generated and results from numerical simulations were compared with experimental data. Results demonstrate that the boundary condition approaches varied in their ability to capture stage 1- and stage 2- evaporation. Results also demonstrated the importance of properly characterizing soil thermal properties and accounting for dry soil conditions. The contribution of film flow to hydraulic conductivity for the layer above the drying front is dominant compared to that of capillary flow, demonstrating the importance of including film flow in modeling efforts for dry soils, especially for fine grained soils. Comparisons of different formulations of the surface boundary condition validate the need for joint evaluation of heat and mass transfer for better modeling accuracy. This knowledge is applicable to many current hydrologic and environmental problems to include climate modeling and the simulation of contaminant transport and volatilization in the shallow subsurface. Smits, K. M., A. Cihan, T. Sakaki, and T. H. Illangasekare (2011). Evaporation from soils under thermal boundary conditions: Experimental and modeling investigation to compare equilibrium- and nonequilibrium-based approaches, Water Resour. Res., 47, W05540, doi:10.1029/2010WR009533.

An Experimental and Modeling Study of Evaporation from Bare Soils Subjected to Natural Boundary Conditions at the Land-Atmospheric Interface

NASA Astrophysics Data System (ADS)

Smits, K. M.; Ngo, V. V.; Cihan, A.; Sakaki, T.; Illangasekare, T. H.; kathleen m smits

2011-12-01

Bare soil evaporation is a key process for water exchange between the land and the atmosphere and an important component of the water balance in semiarid and arid regions. However, there is no agreement on the best methodology to determine evaporation under different boundary conditions. Because it is difficult to measure evaporation from soil,with the exception of using lysimeters, numerous formulations have been proposed to establish a relationship between the rate of evaporation and soil moisture and/or soil temperature and thermal properties. Different formulations vary in how they partition available energy and include, among others, a classical bulk aerodynamic formulation which requires knowledge of the relative humidity at the soil surface and a more non-traditional heat balance method which requires knowledge of soil temperature and soil thermal properties. A need exists to systematically compare existing methods to experimental data under highly controlled conditions not achievable in the field. The goal of this work is to perform controlled experiments under transient conditions of soil moisture, temperature and wind at the land/atmospheric interface to test different conceptual and mathematical formulations for evaporation rate estimates and to develop appropriate numerical models to be used in simulations. In this study, to better understand the coupled water-vapor-heat flow processes in the shallow subsurface near the land surface, we modified a previously developed theory that allows non-equilibrium liquid/gas phase change with gas phase vapor diffusion to better account for evaporation under dry soil conditions. This theory was used to compare estimates of evaporation based on different formulations of the bulk aerodynamic and heat balance methods. In order to experimentally validate the numerical formulations/code, we performed a series of two-dimensional physical model experiments under varying boundary conditions using test sand for which the hydraulic and thermal properties were well characterized. We developed a unique two dimensional cell apparatus equipped with a network of sensors for automated and continuous monitoring of soil moisture, soil and air temperature and relative humidity, and wind velocity. Precision data under well-controlled transient heat and wind boundary conditions was generated. Results from numerical simulations were compared with experimental data. Results demonstrate the importance of properly characterizing soil thermal properties and accounting for dry soil conditions to properly estimate evaporation. Initial comparisons of various formulations of evaporation demonstrate the need for joint evaluation of heat and mass transfer for better modeling accuracy. Detailed comparisons are still underway. This knowledge is applicable to many current hydrologic and environmental problems to include climate modeling and the simulation of contaminant transport and volatilization in the shallow subsurface.

Microbial Genetic Memory to Study Heterogeneous Soil Processes

NASA Astrophysics Data System (ADS)

Fulk, E. M.; Silberg, J. J.; Masiello, C. A.

2017-12-01

Microbes can be engineered to sense environmental conditions and produce a detectable output. These microbial biosensors have traditionally used visual outputs that are difficult to detect in soil. However, recently developed gas-producing biosensors can be used to noninvasively monitor complex soil processes such as horizontal gene transfer or cell-cell signaling. While these biosensors report on the fraction of a microbial population exposed to a process or chemical signal at the time of measurement, they do not record a "memory" of past exposure. Synthetic biologists have recently developed a suite of genetically encoded memory circuits capable of reporting on historical exposure to the signal rather than just the current state. We will provide an overview of the microbial memory systems that may prove useful to studying microbial decision-making in response to environmental conditions. Simple memory circuits can give a yes/no report of any past exposure to the signal (for example anaerobic conditions, osmotic stress, or high nitrate concentrations). More complicated systems can report on the order of exposure of a population to multiple signals or the experiences of spatially distinct populations, such as those in root vs. bulk soil. We will report on proof-of-concept experiments showing the function of a simple permanent memory system in soil-cultured microbes, and we will highlight additional applications. Finally, we will discuss challenges still to be addressed in applying these memory circuits for biogeochemical studies.

Observational Approach to Chromium Site Remediation - 13266

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

Scott Myers, R.

2013-07-01

Production reactors at the U.S. Department of Energy's (DOE) Hanford Site in Richland, Washington, required massive quantities of water for reactor cooling and material processing. To reduce corrosion and the build-up of scale in pipelines and cooling systems, sodium dichromate was added to the water feedstock. Spills and other releases at the makeup facilities, as well as leaks from miles of pipelines, have led to numerous areas with chromium-contaminated soil and groundwater, threatening fish populations in the nearby Columbia River. Pump-and-treat systems have been installed to remove chromium from the groundwater, but significant contamination remain in the soil column andmore » poses a continuing threat to groundwater and the Columbia River. Washington Closure Hanford, DOE, and regulators are working on a team approach that implements the observational approach, a strategy for effectively dealing with the uncertainties inherent in subsurface conditions. Remediation of large, complex waste sites at a federal facility is a daunting effort. It is particularly difficult to perform the work in an environment of rapid response to changing field and contamination conditions. The observational approach, developed by geotechnical engineers to accommodate the inherent uncertainties in subsurface conditions, is a powerful and appropriate method for site remediation. It offers a structured means of quickly moving into full remediation and responding to the variations and changing conditions inherent in waste site cleanups. A number of significant factors, however, complicate the application of the observational approach for chromium site remediation. Conceptual models of contamination and site conditions are difficult to establish and get consensus on. Mid-stream revisions to the design of large excavations are time-consuming and costly. And regulatory constraints and contract performance incentives can be impediments to the flexible responses required under the observational approach. The WCH project team is working closely with stakeholders and taking a number of steps to meet these challenges in a continuing effort to remediate chromium contaminated soil in an efficient and cost-effective manner. (authors)« less

Desert grassland responses to climate and soil moisture suggest divergent vulnerabilities across the southwestern US

USGS Publications Warehouse

Gremer, Jennifer; Bradford, John B.; Munson, Seth M.; Duniway, Michael C.

2015-01-01

Climate change predictions include warming and drying trends, which are expected to be particularly pronounced in the southwestern United States. In this region, grassland dynamics are tightly linked to available moisture, yet it has proven difficult to resolve what aspects of climate drive vegetation change. In part, this is because it is unclear how heterogeneity in soils affects plant responses to climate. Here, we combine climate and soil properties with a mechanistic soil water model to explain temporal fluctuations in perennial grass cover, quantify where and the degree to which incorporating soil water dynamics enhances our ability to understand temporal patterns, and explore the potential consequences of climate change by assessing future trajectories of important climate and soil water variables. Our analyses focused on long-term (20 to 56 years) perennial grass dynamics across the Colorado Plateau, Sonoran, and Chihuahuan Desert regions. Our results suggest that climate variability has negative effects on grass cover, and that precipitation subsidies that extend growing seasons are beneficial. Soil water metrics, including the number of dry days and availability of water from deeper (>30 cm) soil layers, explained additional grass cover variability. While individual climate variables were ranked as more important in explaining grass cover, collectively soil water accounted for 40 to 60% of the total explained variance. Soil water conditions were more useful for understanding the responses of C3 than C4 grass species. Projections of water balance variables under climate change indicate that conditions that currently support perennial grasses will be less common in the future, and these altered conditions will be more pronounced in the Chihuahuan Desert and Colorado Plateau. We conclude that incorporating multiple aspects of climate and accounting for soil variability can improve our ability to understand patterns, identify areas of vulnerability, and predict the future of desert grasslands.

Desert grassland responses to climate and soil moisture suggest divergent vulnerabilities across the southwestern United States.

PubMed

Gremer, Jennifer R; Bradford, John B; Munson, Seth M; Duniway, Michael C

2015-11-01

Climate change predictions include warming and drying trends, which are expected to be particularly pronounced in the southwestern United States. In this region, grassland dynamics are tightly linked to available moisture, yet it has proven difficult to resolve what aspects of climate drive vegetation change. In part, this is because it is unclear how heterogeneity in soils affects plant responses to climate. Here, we combine climate and soil properties with a mechanistic soil water model to explain temporal fluctuations in perennial grass cover, quantify where and the degree to which incorporating soil water dynamics enhances our ability to understand temporal patterns, and explore the potential consequences of climate change by assessing future trajectories of important climate and soil water variables. Our analyses focused on long-term (20-56 years) perennial grass dynamics across the Colorado Plateau, Sonoran, and Chihuahuan Desert regions. Our results suggest that climate variability has negative effects on grass cover, and that precipitation subsidies that extend growing seasons are beneficial. Soil water metrics, including the number of dry days and availability of water from deeper (>30 cm) soil layers, explained additional grass cover variability. While individual climate variables were ranked as more important in explaining grass cover, collectively soil water accounted for 40-60% of the total explained variance. Soil water conditions were more useful for understanding the responses of C3 than C4 grass species. Projections of water balance variables under climate change indicate that conditions that currently support perennial grasses will be less common in the future, and these altered conditions will be more pronounced in the Chihuahuan Desert and Colorado Plateau. We conclude that incorporating multiple aspects of climate and accounting for soil variability can improve our ability to understand patterns, identify areas of vulnerability, and predict the future of desert grasslands. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

Evidence of qualitative differences between soil-occupancy effects of invasive vs. native grassland plant species

USGS Publications Warehouse

Jordan, Nicholas R.; Larson, Diane L.; Huerd, Sheri C.

2011-01-01

Diversified grasslands that contain native plant species are being recognized as important elements of agricultural landscapes and for production of biofuel feedstocks as well as a variety of other ecosystem services. Unfortunately, establishment of such grasslands is often difficult, unpredictable, and highly vulnerable to interference and invasion by weeds. Evidence suggests that soil-microbial "legacies" of invasive perennial species can inhibit growth of native grassland species. However, previous assessments of legacy effects of soil occupancy by invasive species that invade grasslands have focused on single invasive species and on responses to invasive soil occupancy in only a few species. In this study, we tested the hypothesis that legacy effects of invasive species differ qualitatively from those of native grassland species. In a glasshouse, three invasive and three native grassland perennials and a native perennial mixture were grown separately through three cycles of growth and soil conditioning in soils with and without arbuscular mycorrhizal fungi (AMF), after which we assessed seedling growth in these soils. Native species differed categorically from invasives in their response to soil conditioning by native or invasive species, but these differences depended on the presence of AMF. When AMF were present, native species largely had facilitative effects on invasive species, relative to effects of invasives on other invasives. Invasive species did not facilitate native growth; neutral effects were predominant, but strong soil-mediated inhibitory effects on certain native species occurred. Our results support the hypothesis that successful plant invaders create biological legacies in soil that inhibit native growth, but suggest also this mechanism of invasion will have nuanced effects on community dynamics, as some natives may be unaffected by such legacies. Such native species may be valuable as nurse plants that provide cost-effective restoration of soil conditions needed for efficient establishment of diversified grasslands.

High-resolution soil moisture mapping in Afghanistan

NASA Astrophysics Data System (ADS)

Hendrickx, Jan M. H.; Harrison, J. Bruce J.; Borchers, Brian; Kelley, Julie R.; Howington, Stacy; Ballard, Jerry

2011-06-01

Soil moisture conditions have an impact upon virtually all aspects of Army activities and are increasingly affecting its systems and operations. Soil moisture conditions affect operational mobility, detection of landmines and unexploded ordinance, natural material penetration/excavation, military engineering activities, blowing dust and sand, watershed responses, and flooding. This study further explores a method for high-resolution (2.7 m) soil moisture mapping using remote satellite optical imagery that is readily available from Landsat and QuickBird. The soil moisture estimations are needed for the evaluation of IED sensors using the Countermine Simulation Testbed in regions where access is difficult or impossible. The method has been tested in Helmand Province, Afghanistan, using a Landsat7 image and a QuickBird image of April 23 and 24, 2009, respectively. In previous work it was found that Landsat soil moisture can be predicted from the visual and near infra-red Landsat bands1-4. Since QuickBird bands 1-4 are almost identical to Landsat bands 1- 4, a Landsat soil moisture map can be downscaled using QuickBird bands 1-4. However, using this global approach for downscaling from Landsat to QuickBird scale yielded a small number of pixels with erroneous soil moisture values. Therefore, the objective of this study is to examine how the quality of the downscaled soil moisture maps can be improved by using a data stratification approach for the development of downscaling regression equations for each landscape class. It was found that stratification results in a reliable downscaled soil moisture map with a spatial resolution of 2.7 m.

Use of slope, aspect, and elevation maps derived from digital elevation model data in making soil surveys

USGS Publications Warehouse

Klingebiel, A.A.; Horvath, E.H.; Moore, D.G.; Reybold, W.U.

1987-01-01

Maps showing different classes of slope, aspect, and elevation were developed from U.S. Geological Survey digital elevation model data. The classes were displayed on clear Mylar at 1:24 000-scale and registered with topographic maps and orthophotos. The maps were used with aerial photographs, topographic maps, and other resource data to determine their value in making order-three soil surveys. They were tested on over 600 000 ha in Wyoming, Idaho, and Nevada under various climatic and topographic conditions. Field evaluations showed that the maps developed from digital elevation model data were accurate, except for slope class maps where slopes were <4%. The maps were useful to soil scientists, especially where (i) class boundaries coincided with soil changes, landform delineations, land use and management separations, and vegetation changes, and (ii) rough terrain and dense vegetation made it difficult to traverse the area. In hot, arid areas of sparse vegetation, the relationship of slope classes to kinds of soil and vegetation was less significant.

SITE TECHNOLOGY CAPSULE: TERRA-KLEEN SOLVENT EXTRACTION TECHNOLOGY

EPA Science Inventory

Remediation of PCBs in soils has been difficult to implement on a full-scale, cost-effective basis. The Terra-Kleen solvent extraction system has overcome many of the soil handling, contaminant removal, and regulatory restrictions that have made it difficult to implement a cost-e...

Biological and physical factors controlling aggregate stability under different climatic conditions in Southern Spain.

NASA Astrophysics Data System (ADS)

Ángel Gabarrón-Galeote, Miguel; Damián Ruiz-Sinoga, Jose; Francisco Martinez-Murillo, Juan; Lavee, Hanoch

2013-04-01

Soil aggregation is a key factor determining the soil structure. The presence of stable aggregates is essential to maintain a good soil structure, that in turn plays an important role in sustaining agricultural productivity and preserving environmental quality. A wide range of physical and biological soil components are involved in the aggregate formation and stabilization, namely clay mineral content; the quantity and quality of organic matter, that can be derived from plants, fungal hyphae, microorganism and soil animals; and the soil water content. Climatic conditions, through their effect on soil water content, vegetation cover and organic matter content, are supposed to affect soil aggregation. Thus the main objective of this research is to analyse the effect of organic matter, clay content and soil water content on aggregate stability along a climatic transect in Southern Spain. This study was conducted in four catchments along a pluviometric gradient in the South of Spain (rainfall depth decreases from west to east from more than 1000 mm year-1 to less than 300 mm year-1) and was based on a methodology approximating the climatic gradient in Mediterranean conditions. The selected sites shared similar conditions of geology, topography and soil use, which allowed making comparisons among them and relating the differences to the pluviometric conditions. In February 2007, 250 disturbed and undisturbed samples from the first 5cm of the soil were collected along the transect. We measured the aggregate stability, organic matter, clay content and bulk density of every sample. In the field we measured rainfall, air temperature, relative humidity, wind speed, wind direction, solar radiation, potential evapotranspiration, soil water content, vegetation cover and presence of litter. Our results suggest that aggregate stability is a property determined by a great number of highly variable factors, which can make extremely difficult to predict its behavior taking in account only a few of them. The climate exerted a great influence in aggregate stability and could determine by itself the soil structure along the climate transect. As a result, properties unrelated in a specific point of the climate transect became highly associated if we took it into account completely. Along the climate transect analyzed could be defined two areas, separated by a threshold located between 573.6 mm y-1 and 335.9 mm y-1. In the wettest part soil structure was mainly determined by biotic factors and in the driest part was highly probable that abiotic factors play a key role determining aggregate stability.

Surface Soil Moisture Retrieval Using SSM/I and Its Comparison with ESTAR: A Case Study Over a Grassland Region

NASA Technical Reports Server (NTRS)

Jackson, T.; Hsu, A. Y.; ONeill, P. E.

1999-01-01

This study extends a previous investigation on estimating surface soil moisture using the Special Sensor Microwave/Imager (SSM/I) over a grassland region. Although SSM/I is not optimal for soil moisture retrieval, it can under some conditions provide information. Rigorous analyses over land have been difficult due to the lack of good validation data sets. A scientific objective of the Southern Great Plains 1997 (SGP97) Hydrology Experiment was to investigate whether the retrieval algorithms for surface soil moisture developed at higher spatial resolution using truck-and aircraft-based passive microwave sensors can be extended to the coarser resolutions expected from satellite platform. With the data collected for the SGP97, the objective of this study is to compare the surface soil moisture estimated from the SSM/I data with those retrieved from the L-band Electronically Scanned Thinned Array Radiometer (ESTAR) data, the core sensor for the experiment, using the same retrieval algorithm. The results indicated that an error of estimate of 7.81% could be achieved with SSM/I data as contrasted to 2.82% with ESTAR data over three intensive sampling areas of different vegetation regimes. It confirms the results of previous study that SSM/I data can be used to retrieve surface soil moisture information at a regional scale under certain conditions.

Spectrometry of Pasture Condition and Biogeochemistry in the Central Amazon

NASA Technical Reports Server (NTRS)

Asner, Gregory P.; Townsend, Alan R.; Bustamante, Mercedes M. C.

1999-01-01

Regional analyses of Amazon cattle pasture biogeochemistry are difficult due to the complexity of human, edaphic, biotic and climatic factors and persistent cloud cover in satellite observations. We developed a method to estimate key biophysical properties of Amazon pastures using hyperspectral reflectance data and photon transport inverse modeling. Remote estimates of live and senescent biomass were strongly correlated with plant-available forms of soil phosphorus and calcium. These results provide a basis for monitoring pasture condition and biogeochemistry in the Amazon Basin using spaceborne hyperspectral sensors.

Monitoring rangeland dynamics in Senegal with advanced very high resolution radiometer data

USGS Publications Warehouse

Tappan, G. Gray; Tyler, Dean J.; Wehde, M. E.; Moore, Donald G.

1992-01-01

Time‐series Normalized Difference Vegetation Index (NDVI) data, computed from Advanced Very High Resolution Radiometer data, are being used by regional and national programs in the African Sahel to monitor seasonal rangeland conditions. The data are often used as indicators of grazing conditions and drought. However, distinguishing rangelands from other vegetation cover types on NDVI images is difficult. A second complication is that rangeland types and their associated productivity vary geographically by soil type. To effectively assess rangeland conditions, seasonal fluctuations (due to climatic cycles) must be isolated from long‐term production characteristics associated with vegetation type and soil differences. Rangeland NDVI dynamics, including qualitative assessments of rangeland production, and the timing and length of the growing season in Senegal were examined by using 7.4‐km global area coverage satellite data. Analyses were based on 10‐day NDVI composite image data from 1982 through 1989. The NDVI image data were stratified by rangeland and soil polygons derived from locally available resource maps. Time‐series NDVI statistics were calculated from the resource polygons that had been interpreted into high, medium, and low production rangelands. Analysts monitoring rangeland conditions can better identify seasonal anomalies such as drought by comparing production potential within homogeneous; resource polygons with the current NDVI data.

Bioavailability-Based In Situ Remediation To Meet Future Lead (Pb) Standards in Urban Soils and Gardens.

PubMed

Henry, Heather; Naujokas, Marisa F; Attanayake, Chammi; Basta, Nicholas T; Cheng, Zhongqi; Hettiarachchi, Ganga M; Maddaloni, Mark; Schadt, Christopher; Scheckel, Kirk G

2015-08-04

Recently the Centers for Disease Control and Prevention lowered the blood Pb reference value to 5 μg/dL. The lower reference value combined with increased repurposing of postindustrial lands are heightening concerns and driving interest in reducing soil Pb exposures. As a result, regulatory decision makers may lower residential soil screening levels (SSLs), used in setting Pb cleanup levels, to levels that may be difficult to achieve, especially in urban areas. This paper discusses challenges in remediation and bioavailability assessments of Pb in urban soils in the context of lower SSLs and identifies research needs to better address those challenges. Although in situ remediation with phosphate amendments is a viable option, the scope of the problem and conditions in urban settings may necessitate that SSLs be based on bioavailable rather than total Pb concentrations. However, variability in soil composition can influence bioavailability testing and soil amendment effectiveness. More data are urgently needed to better understand this variability and increase confidence in using these approaches in risk-based decision making, particularly in urban areas.

Bioavailability-Based In Situ Remediation To Meet Future Lead (Pb) Standards in Urban Soils and Gardens

DOE PAGES

Henry, Heather; Naujokas, Marisa F.; Attanayake, Chammi; ...

2015-07-03

Recently the Centers for Disease Control and Prevention lowered the blood Pb reference value to 5 μg/dL. The lower reference value combined with increased repurposing of postindustrial lands are heightening concerns and driving interest in reducing soil Pb exposures. As a result, regulatory decision makers may lower residential soil screening levels (SSLs), used in setting Pb cleanup levels, to levels that may be difficult to achieve, especially in urban areas. This study discusses challenges in remediation and bioavailability assessments of Pb in urban soils in the context of lower SSLs and identifies research needs to better address those challenges. Althoughmore » in situ remediation with phosphate amendments is a viable option, the scope of the problem and conditions in urban settings may necessitate that SSLs be based on bioavailable rather than total Pb concentrations. However, variability in soil composition can influence bioavailability testing and soil amendment effectiveness. Finally, more data are urgently needed to better understand this variability and increase confidence in using these approaches in risk-based decision making, particularly in urban areas.« less

Bioavailability-Based In Situ Remediation To Meet Future Lead (Pb) Standards in Urban Soils and Gardens

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

Henry, Heather; Naujokas, Marisa F.; Attanayake, Chammi

Recently the Centers for Disease Control and Prevention lowered the blood Pb reference value to 5 μg/dL. The lower reference value combined with increased repurposing of postindustrial lands are heightening concerns and driving interest in reducing soil Pb exposures. As a result, regulatory decision makers may lower residential soil screening levels (SSLs), used in setting Pb cleanup levels, to levels that may be difficult to achieve, especially in urban areas. This study discusses challenges in remediation and bioavailability assessments of Pb in urban soils in the context of lower SSLs and identifies research needs to better address those challenges. Althoughmore » in situ remediation with phosphate amendments is a viable option, the scope of the problem and conditions in urban settings may necessitate that SSLs be based on bioavailable rather than total Pb concentrations. However, variability in soil composition can influence bioavailability testing and soil amendment effectiveness. Finally, more data are urgently needed to better understand this variability and increase confidence in using these approaches in risk-based decision making, particularly in urban areas.« less

Moisture-strength-constructability guidelines for subgrade foundation soils found in Indiana.

DOT National Transportation Integrated Search

2016-09-01

Soil moisture is an important indicator of constructability in the field. Construction activities become difficult when the soil moisture content is excessive, especially in fine-grained soils. Change orders caused by excessive soil moisture during c...

Peatlands and potatoes; organic wetland soils in Uganda

NASA Astrophysics Data System (ADS)

Farmer, Jenny; Langan, Charlie; Gimona, Alessandro; Poggio, Laura; Smith, Jo

2017-04-01

Land use change in Uganda's wetlands has received very little research attention. Peat soils dominate the papyrus wetlands of the south west of the country, but the areas they are found in have been increasingly converted to potato cultivation. Our research in Uganda set out to (a) document both the annual use of and changes to these soils under potato cultivation, and (b) the extent and condition of these soils across wetland systems. During our research we found it was necessary to develop locally appropriate protocols for sampling and analysis of soil characteristics, based on field conditions and locally available resources. Over the period of one year we studied the use of the peat soil for potato cultivation by smallholder farmers in Ruhuma wetland and measured changes to surface peat properties and soil nutrients in fields over that time. Farmer's use of the fields changed over the year, with cultivation, harvesting and fallow periods, which impacted on soil micro-topography. Measured soil properties changed over the course of the year as a result of the land use, with bulk density, nitrogen content, potassium and magnesium all reducing. Comparison of changes in soil carbon stocks over the study period were difficult to make as it was not possible to reach the bottom of the peat layer. However, a layer of fallow weeds discarded onto the soil prior to preparation of the raised potato beds provided a time marker which gave insight into carbon losses over the year. To determine the peatland extent, a spatial survey was conducted in the Kanyabaha-Rushebeya wetland system, capturing peat depths and key soil properties (bulk density, organic matter and carbon contents). Generalised additive models were used to map peat depth and soil characteristics across the system, and maps were developed for these as well as drainage and land use classes. Comparison of peat cores between the two study areas indicates spatial variability in peat depths and the influence of neighbouring mineral soil hillslopes. Our work provides valuable insight into the condition and use of these tropical peat soils, which are under-researched yet highly depended upon by local communities, with wider climate impacts. Cultivation of these peat soils has implications for their future sustainability and use, and having insight into the impacts of land management on these soils improves local and national level capacity for better soil management.

Gardening guide for high-desert urban landscapes of Great Basin regions in Nevada and Utah

Treesearch

Heidi Kratsch; Rick Heflebower

2013-01-01

Some Great Basin urban areas in Utah and Nevada exhibit climatic conditions that make it difficult for all but the toughest landscape plants to thrive without providing supplemental water. These areas are found at elevations from 4,000 feet to 6,000 feet in USDA cold-hardiness zones 6 and 7. Soils are often poor and gravelly, containing less than 1 percent organic...

Agricultural Nutrient Cycling at the Strawberry Creek Watershed: Insights Into Processes Using Stable Isotope Analysis

NASA Astrophysics Data System (ADS)

Thuss, E.; English, M. C.; Spoelstra, J.

2009-05-01

When nitrogen availability exceeds biological demand, excess nitrogen, especially nitrate, may subsequently pollute ground and surface water. Agricultural practices in Southern Ontario typically supplement soils with organic and inorganic nutrients to aid in crop development, and employ various management techniques to limit nutrient loss. Excess nitrogen has several potential fates, which are controlled by the net effects of numerous nitrogen cycling reactions in the soil that are often difficult to measure directly. Nitrogen cycling in soils is controlled in large part by soil moisture, as it affects microbial activity and soil redox conditions. Stable isotope geochemistry is a powerful tool that provides information on nitrogen sources and processes. This study uses crop nitrogen and carbon isotope ratios to provide insights into the net effects of soil nitrogen cycling and nitrogen fate. This research was conducted at the Strawberry Creek Watershed (SCW), an agricultural research watershed located between Kitchener-Waterloo and Guelph, Ontario. The SCW exhibits elevated nitrate concentrations in groundwater, tile discharge, and the stream itself. Previous isotopic work revealed that this nitrate is largely derived from chemical fertilizer and manure applications. Field-scale hydrological processes lead to areas where the fate of applied nitrogen differs, which has an isotopic effect on the residual nitrogen that is available to plants. Results of this study indicate significant patterns in the isotopic signature of plant tissue, in both temporal and spatial scales. At the plot-scale where soil conditions are similar, there is little to no variation in foliar isotope values, but at the field-scale there appears to be a significant amount of variability related to soil moisture and nitrogen loss. This relationship can potentially provide insight into ideal conditions for nitrogen uptake efficiency. Reducing agricultural nitrogen leaching to ground and surface water requires a better understanding of nitrogen fate in the soil zone, and will result in more effective agricultural nutrient management.

Growth of chitinolytic dune soil beta-subclass Proteobacteria in response to invading fungal hyphae.

PubMed

De Boer, W; Klein Gunnewiek, P J; Kowalchuk, G A; Van Veen, J A

2001-08-01

It has frequently been reported that chitinolytic soil bacteria, in particular biocontrol strains, can lyse living fungal hyphae, thereby releasing potential growth substrate. However, the conditions used in such assays (high bacterial density, rich media, fragmented hyphae) make it difficult to determine whether mycolytic activity is actually of importance for the growth and survival of chitinolytic bacteria in soils. An unidentified group of beta-subclass Proteobacteria (CbetaPs) was most dominant among the culturable nonfilamentous chitinolytic bacteria isolated from Dutch sand dune soils. Here we demonstrate that the CbetaPs grew at the expense of extending fungal mycelium of three dune soil fungi (Chaetomium globosum, Fusarium culmorum, and Mucor hiemalis) under nutrient-limiting, soil-like conditions. Aggregates of CbetaPs were also often found attached to fungal hyphae. The growth of a control group of dominant nonchitinolytic dune soil bacteria (beta- and gamma-subclass Proteobacteria) was not stimulated in the mycelial zone, indicating that growth-supporting materials were not independently released in appreciable amounts by the extending hyphae. Therefore, mycolytic activities of CbetaPs have apparently been involved in allowing them to grow after exposure to living hyphae. The chitinase inhibitor allosamidin did not, in the case of Mucor, or only partially, in the cases of Chaetomium and Fusarium, repress mycolytic growth of the CbetaPs, indicating that chitinase activity alone could not explain the extent of bacterial proliferation. Chitinolytic Stenotrophomonas-like and Cytophaga-like bacteria, isolated from the same dune soils, were only slightly stimulated by exposure to fungal hyphae.

Constraining Gas Diffusivity-Soil Water Content Relationships in Forest Soils Using Surface Chamber Fluxes and Depth Profiles of Multiple Trace Gases

NASA Astrophysics Data System (ADS)

Dore, J. E.; Kaiser, K.; Seybold, E. C.; McGlynn, B. L.

2012-12-01

Forest soils are sources of carbon dioxide (CO2) to the atmosphere and can act as either sources or sinks of methane (CH4) and nitrous oxide (N2O), depending on redox conditions and other factors. Soil moisture is an important control on microbial activity, redox conditions and gas diffusivity. Direct chamber measurements of soil-air CO2 fluxes are facilitated by the availability of sensitive, portable infrared sensors; however, corresponding CH4 and N2O fluxes typically require the collection of time-course physical samples from the chamber with subsequent analyses by gas chromatography (GC). Vertical profiles of soil gas concentrations may also be used to derive CH4 and N2O fluxes by the gradient method; this method requires much less time and many fewer GC samples than the direct chamber method, but requires that effective soil gas diffusivities are known. In practice, soil gas diffusivity is often difficult to accurately estimate using a modeling approach. In our study, we apply both the chamber and gradient methods to estimate soil trace gas fluxes across a complex Rocky Mountain forested watershed in central Montana. We combine chamber flux measurements of CO2 (by infrared sensor) and CH4 and N2O (by GC) with co-located soil gas profiles to determine effective diffusivity in soil for each gas simultaneously, over-determining the diffusion equations and providing constraints on both the chamber and gradient methodologies. We then relate these soil gas diffusivities to soil type and volumetric water content in an effort to arrive at empirical parameterizations that may be used to estimate gas diffusivities across the watershed, thereby facilitating more accurate, frequent and widespread gradient-based measurements of trace gas fluxes across our study system. Our empirical approach to constraining soil gas diffusivity is well suited for trace gas flux studies over complex landscapes in general.

Soil biota reduce allelopathic effects of the invasive Eupatorium adenophorum.

PubMed

Zhu, Xunzhi; Zhang, Jintun; Ma, Keping

2011-01-01

Allelopathy has been hypothesized to play a role in exotic plant invasions, and study of this process can improve our understanding of how direct and indirect plant interactions influence plant community organization and ecosystem functioning. However, allelopathic effects can be highly conditional. For example allelopathic effects demonstrated in vivo can be difficult to demonstrate in field soils. Here we tested phytotoxicity of Eupatorium adenophorum (croftonweed), one of the most destructive exotic species in China, to a native plant species Brassica rapa both in sand and in native soil. Our results suggested that natural soils from different invaded habitats alleviated or eliminated the efficacy of potential allelochemicals relative to sand cultures. When that soil is sterilized, the allelopathic effects returned; suggesting that soil biota were responsible for the reduced phytotoxicity in natural soils. Neither of the two allelopathic compounds (9-Oxo-10,11-dehydroageraphorone and 9b-Hydroxyageraphorone) of E. adenophorum could be found in natural soils infested by the invader, and when those compounds were added to the soils as leachates, they showed substantial degradation after 24 hours in natural soils but not in sand. Our findings emphasize that soil biota can reduce the allelopathic effects of invaders on other plants, and therefore can reduce community invasibility. These results also suggest that soil biota may have stronger or weaker effects on allelopathic interactions depending on how allelochemicals are delivered.

Soil Biota Reduce Allelopathic Effects of the Invasive Eupatorium adenophorum

PubMed Central

Zhu, Xunzhi; Zhang, Jintun; Ma, Keping

2011-01-01

Allelopathy has been hypothesized to play a role in exotic plant invasions, and study of this process can improve our understanding of how direct and indirect plant interactions influence plant community organization and ecosystem functioning. However, allelopathic effects can be highly conditional. For example allelopathic effects demonstrated in vivo can be difficult to demonstrate in field soils. Here we tested phytotoxicity of Eupatorium adenophorum (croftonweed), one of the most destructive exotic species in China, to a native plant species Brassica rapa both in sand and in native soil. Our results suggested that natural soils from different invaded habitats alleviated or eliminated the efficacy of potential allelochemicals relative to sand cultures. When that soil is sterilized, the allelopathic effects returned; suggesting that soil biota were responsible for the reduced phytotoxicity in natural soils. Neither of the two allelopathic compounds (9-Oxo-10,11-dehydroageraphorone and 9b-Hydroxyageraphorone) of E. adenophorum could be found in natural soils infested by the invader, and when those compounds were added to the soils as leachates, they showed substantial degradation after 24 hours in natural soils but not in sand. Our findings emphasize that soil biota can reduce the allelopathic effects of invaders on other plants, and therefore can reduce community invasibility. These results also suggest that soil biota may have stronger or weaker effects on allelopathic interactions depending on how allelochemicals are delivered. PMID:21980442

Influence of soil properties and soil moisture on the efficacy of indaziflam and flumioxazin on Kochia scoparia L.

PubMed

Sebastian, Derek J; Nissen, Scott J; Westra, Phil; Shaner, Dale L; Butters, Greg

2017-02-01

Kochia (Kochia scoparia L.) is a highly competitive, non-native weed found throughout the western United States. Flumioxazin and indaziflam are two broad-spectrum pre-emergence herbicides that can control kochia in a variety of crop and non-crop situations; however, under dry conditions, these herbicides sometimes fail to control this important weed. There is very little information describing the effect of soil properties and soil moisture on the efficacy of these herbicides. Soil organic matter (SOM) explained the highest proportion of variability in predicting the herbicide dose required for 80% kochia growth reduction (GR 80 ) for flumioxazin and indaziflam (R 2 = 0.72 and 0.79 respectively). SOM had a greater impact on flumioxazin phytotoxicity compared to indaziflam. Flumioxazin and indaziflam kochia phytotoxicity was greatly reduced at soil water potentials below -200 kPa. Kochia can germinate at soil moisture potentials below the moisture required for flumioxazin and indaziflam activation, which means that kochia control is greatly influenced by the complex interaction between soil physical properties and soil moisture. This research can be used to gain a better understanding of how and why some weeds, like kochia, are so difficult to manage even with herbicides that normally provide excellent control. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

Marginality principle

USDA-ARS?s Scientific Manuscript database

Soil is a fragile resource supplying many goods and services. Given the diversity of soil across the world and within a landscape, there are many different capacities among soils to provide the basic soil functions. Marginality of soils is a difficult process to define because the metrics to define ...

Soil mixing design methods and construction techniques for use in high organic soils.

DOT National Transportation Integrated Search

2015-06-01

Organic soils present a difficult challenge for roadway designers and construction due to the high : compressibility of the soil structure and the often associated high water table and moisture content. For : other soft or loose inorganic soils, stab...

Development of Acid Functional Groups and Lactones During the Thermal Degradation of Wood and Wood Components

USGS Publications Warehouse

Rutherford, David W.; Wershaw, Robert L.; Reeves, James B.

2008-01-01

Black carbon (pyrogenic materials including chars) in soils has been recognized as a substantial portion of soil organic matter, and has been shown to play a vital role in nutrient cycling; however, little is known concerning the properties of this material. Previous studies have largely been concerned with the creation of high-surface-area materials for use as sorbents. These materials have been manufactured at high temperature and have often been activated. Chars occurring in the environment can be formed over a wide range of temperature. Because it is extremely difficult to isolate black carbon once it has been incorporated in soils, chars produced in the laboratory under controlled conditions can be used to investigate the range of properties possible for natural chars. This report shows that charring conditions (temperature and time) have substantial impact on the acid functional group and lactone content of chars. Low temperatures (250?C) and long charring times (greater than 72 hours) produce chars with the highest acid functional group and lactone content. The charring of cellulose appears to be responsible for the creation of the acid functional group and lactones. The significance of this study is that low-temperature chars can have acid functional group contents comparable to humic materials (as high as 8.8 milliequivalents per gram). Acid functional group and lactone content decreases as charring temperature increases. The variation in formation conditions expected under natural fire conditions will result in a wide range of sorption properties for natural chars which are an important component of soil organic matter. By controlling the temperature and duration of charring, it is possible to tailor the sorption properties of chars, which may be used as soil amendments.

Improvement of the Assignment Methodology of the Approach Embankment Design to Highway Structures in Difficult Conditions

NASA Astrophysics Data System (ADS)

Chistyy, Y.; Kuzakhmetova, E.; Fazilova, Z.; Tsukanova, O.

2018-03-01

Design issues of junction of bridges and overhead road with approach embankment are studied. The reasons for the formation of deformations in the road structure are indicated. Activities to ensure sustainability and acceleration of the shrinkage of a weak subgrade approach embankment are listed. The necessity of taking into account the man-made impact of the approach embankment on the subgrade behavior is proved. Modern stabilizing agents to improve the properties of used soils in the embankment and the subgrade are suggested. Clarified methodology for determining an active zone of compression in the subgrade under load from the weight of the embankment is described. As an additional condition to the existing methodology for establishing the lower bound of the active zone of compression it is offered to accept the accuracy of evaluation of soil compressibility and determine shrinkage.

Soil washing in combination with homogeneous Fenton-like oxidation for the removal of 2,4,4'-trichlorodiphenyl from soil contaminated with capacitor oil.

PubMed

Ma, Xiao-Hong; Zhao, Ling; Lin, Zhi-Rong; Dong, Yuan-Hua

2016-04-01

Detoxification by chemical oxidation of polychlorinated biphenyls (PCBs) in contaminated soils is very difficult and inefficient because PCBs typically associate with the solid phase or exist as non-aqueous-phase liquids due to their low solubility and slow desorption rates, and thus, they are difficult to remove from soils by using traditional, water-based elution techniques. Surfactant can enhance washing efficiency of PCBs from contaminated soils. This study used Brij 58, Brij 30, Tween 80, and 2-hydroxypropyl-β-cyclodextrin (HPCD) to solubilize 2,4,4'-trichlorodiphenyl (PCB28) from soil contaminated with capacitor oil into solution. The feasibility of PCB28 oxidation in soil washing wastewater through a Fe(3+)-catalyzed Fenton-like reaction was subsequently examined. Washing with 10 g L(-1) Brij 58 solution showed the highest extraction efficiency (up to 61.5 %) compared with that of the three other surfactants. The total concentration of PCB28 in contaminated soil at 25 °C after 48-h extraction was 286 mg L(-1). In contrast to conditions in which no washing agent was added, addition of the four washing agents decreased the efficiency of PCB28 degradation by the Fenton-like reaction, with the decrease due to addition of 10 g L(-1) Brij 58 solution being the smallest. The optimal concentration of H2O2 for preventing its useless decomposition was found to be 50 mM. The efficiency of PCB28 removal was lower when the initial concentration of PCB28 treated in the Fenton-like reaction was higher. The degradation efficiencies of PCB28 at initial concentrations of 0.1, 10, and 176 mg L(-1) in 10 g L(-1) Brij 58 solution at 25 °C and pH 3.0 and 9 h of reaction using 50 mM H2O2 were 64.1, 42.0, and 34.6 %, respectively. This result indicates that soil washing combined with Fenton-like oxidation may be a practical approach for the remediation of PCB-contaminated soil.

Soil physical property estimation from soil strength and apparent electrical conductivity sensor data

USDA-ARS?s Scientific Manuscript database

Quantification of soil physical properties through soil sampling and laboratory analyses is time-, cost-, and labor-consuming, making it difficult to obtain the spatially-dense data required for precision agriculture. Proximal soil sensing is an attractive alternative, but many currently available s...

[Fertility and Environmental Impacts of Urban Scattered Human Feces Used as Organic Granular Fertilizer for Leaf Vegetables].

PubMed

Lü, Wen-zhou; Qiao, Yu-xiang; Yu, Ning; Shi, Rong-hua; Wang, Guang-ming

2015-09-01

The disposal of urban scattered human feces has become a difficult problem for the management of modern city. In present study, the scattered human feces underwent the collection, scum removal, flocculation and dehydration, finally became the granular fertilizer; the effects of the ratio of fertilizer to soil on the growth of the pakchoi and the quality of soil and leaching water were evaluated, and the feasibility of granular fertilizer manuring the pakchoi was discussed by pot experiments. The results showed that the granular fertilizer significantly enhanced the production of the pakchoi which were not polluted by the intestinal microorganisms under the experiment conditions; meanwhile, at the proper ratio of fertilizer to soil, the concentration of these microorganisms in the leaching water was lower than that in the control check. Chemical analyses of soil revealed that the nutrient content of nitrogen, phosphorus, potassium and organic matters in soil became much richer in all treatments. In addition, the granular fertilizer improved the physical- chemical properties of soil, including raising the level of soil porosity and reducing the volume weight of soil. Application of granular fertilizer won't pollute the soil or leaching water; instead, it can also prevent nitrogen, potassium and intestinal microorganisms from leaching inio ground water at the proper ratio of granular fertilizer to soil.

Soil, Water, Plants and Preferred Flow in All Directions: A Biosphere-2 Experiment

NASA Astrophysics Data System (ADS)

McDonnell, J.; Evaristo, J. A.; Kim, M.; Van Haren, J. L. M.; Pangle, L. A.; Harman, C. J.; Troch, P. A. A.

2016-12-01

Measuring, understanding and predicting preferential flow in the critical zone is impossibly difficult, but we must try. While past work has focused on specific features of preferential flow pathways and model parameterizations, the resultant effect of preferential flow is often difficult to detect because we do not know the boundary conditions of our flow domain. Here we take a holistic view of preferential flow at the ecosystem level. We present new results from the tropical rainforest biome at Biosphere 2. We test the null hypothesis that the ecohydrological system is well mixed and that water forming groundwater recharge and plant transpiration is from a common pool. Our specific research question is what is the nature of preferential flow and partitioning of groundwater recharge, soil water recharge, and transpiration water after rainfall events? We performed a 10-week drought experiment and then added 66 mm of labelled rainfall with 152‰ deuterium (D), distributed over four events (mean 16.5 mm per event). This was followed by a total of 87 mm of rainfall (-60‰ D) distributed over 13 events that were spaced every 2-3 days. Our results show that flow in all ecohydrological domains (soil water, groundwater recharge and plant transpiration) was preferential. With known boundary conditions, we found that groundwater recharge was 3-8 times younger ( 8 days) than transpired water (range 24-64 days). The "age" of transpired water showed strong dependence on species and was intimately linked to driving force (difference between soil matric potential and midday leaf water potential). These results suggest that preferential flow in the critical zone is one whereby transpiration is strongly species-dependent, and groundwater recharge is controlled by inherent subsurface heterogeneity. The marked difference in the ages associated with these two fluxes supports the concept of ecohydrological separation—in this case, in a `time-based' context.

When and where does preferential flow matter - from observation to large scale modelling

NASA Astrophysics Data System (ADS)

Weiler, Markus; Leistert, Hannes; Steinbrich, Andreas

2017-04-01

Preferential flow can be of relevance in a wide range of soils and the interaction of different processes and factors are still difficult to assess. As most studies (including our own studies) focusing on the effect of preferential flow are based on relatively high precipitation rates, there is always the question how relevant preferential flow is under natural conditions, considering the site specific precipitation characteristics, the effect of the drying and wetting cycle on the initial soil water condition and shrinkage cracks, the site specific soil properties, soil structure and rock fragments, and the effect of plant roots and soil fauna (e.g. earthworm channels). In order to assess this question, we developed the distributed, process-based model RoGeR (Runoff Generation Research) to include a large number relevant features and processes of preferential flow in soils. The model was developed from a large number of process based research and experiments and includes preferential flow in roots, earthworm channels, along rock fragments and shrinkage cracks. We parameterized the uncalibrated model at a high spatial resolution of 5x5m for the whole state of Baden-Württemberg in Germany using LiDAR data, degree of sealing, landuse, soil properties and geology. As the model is an event based model, we derived typical event based precipitation characteristics based on rainfall duration, mean intensity and amount. Using the site-specific variability of initial soil moisture derived from a water balance model based on the same dataset, we simulated the infiltration and recharge amounts of all event classes derived from the event precipitation characteristics and initial soil moisture conditions. The analysis of the simulation results allowed us to extracts the relevance of preferential flow for infiltration and recharge considering all factors above. We could clearly see a strong effect of the soil properties and land-use, but also, particular for clay rich soils a strong effect of the initial conditions due to the development of soil cracks. Not too surprisingly, the relevance of preferential flow was much lower when considering the whole range of precipitation events as only considering events with a high rainfall intensity. Also, the influence on infiltration and recharge were different. Despite the model can still be improved in particular considering more realistic information about the spatial and temporal variability of preferential flow by soil fauna and plants, the model already shows under what situation we need to be very careful when predicting infiltration and recharge with models considering only longer time steps (daily) or only matrix flow.

Formation of Soil Water Repellency by Laboratory Burning and Its Effect on Soil Evaporation

NASA Astrophysics Data System (ADS)

Ahn, Sujung; Im, Sangjun

2010-05-01

Fire-induced soil water repellency can vary with burning conditions, and may lead to significant changes in soil hydraulic properties. However, isolation of the effects of soil water repellency from other factors is difficult, particularly under field conditions. This study was conducted to (i) investigate the effects of burning using different plant leaf materials and (ii) of different burning conditions on the formation of soil water repellency, and (iii) isolate the effects of the resulting soil water repellency on soil evaporation from other factors. Burning treatments were performed on the surface of homogeneous fully wettable sand soil contained in a steel frame (60 x 60 cm; 40 cm depth). As controls a sample without a heat treatment, and a heated sample without fuel, were also used. Ignition and heat treatments were carried out with a gas torch. For comparing the effects of different burning conditions, fuel types included oven-dried pine needles (fresh needles of Pinus densiflora), pine needle litter (litter on a coniferous forest floor, P. densiflora + P. rigida), and broad-leaf litter (Quercus mongolica + Q. aliena + Prunus serrulata var. spontanea + other species); fuel loads were 200 g, 300 g, and 500 g; and heating duration was 40 s, 90 s and 180 s. The heating duration was adjusted to control the temperature, based on previous experiments. The temperature was measured continuously at 3-second intervals and logged with two thermometers. After burning, undisturbed soil columns were sampled for subsequent experiments. Water Drop Penetration Time (WDPT) test was performed at every 1 mm depth of the soil columns to measure the severity of soil water repellency and its vertical extent. Soil water repellency was detected following all treatments. As the duration of heating increased, the thickness of the water repellent layer increased, whilst the severity of soil water repellency decreased. As regards fuel amount, the most severe soil water repellency was formed at a fuel load of 300 g. Pine needle litter formed the most severe soil water repellency and fresh pine needle formed the thickest water repellent layer, whilst broad-leaf litter did only cause water repellency on the surface of the sand. The soil evaporation rate was measured by a gravitational method at an isothermal condition. Undisturbed soil columns were sealed after adding 50 ml of tap water through the bottom. After twelve hours of stabilization, the columns were opened and covered with filter paper. The rate of soil evaporation through the soil surface was measured by the hourly weight change at 45° C. The initial 65 hours' evaporation rate was analyzed, while the slope of cumulative evaporation over time maintained its linearity. It was found that as the thickness of the water repellent layer increased, the evaporation rate tended to decrease. These two variables showed a good correlation (Pearson's correlation coefficient =-0.8916, p=0.0170) and a large coefficient of determination (R2=0.795) in the linear regression. This suggests that a layer of water repellent soil can affect water evaporation rate and that the rate is negatively correlated with the thickness of the repellent layer.

Evaluation Criteria and Results of Full Scale Testing of Bridge Abutment Made from Reinforced Soil

NASA Astrophysics Data System (ADS)

Hildebrand, Maciej; Rybak, Jarosław

2017-10-01

Structures made of reinforced soil can be evaluated for their safety based on a load testing. Measurement results are essentially evaluated by displacements of surcharge (mainly in vertical direction) and facing elements (mainly in horizontal direction). Displacements are within several tenths to several millimetres and they can be taken by common geodetic equipment. Due to slow soil consolidation (progress of displacements) under constant load, observations should be made over several days or even weeks or months. A standard procedure of heating of geotextiles, used in laboratory conditions to simulate long term behaviour cannot be used in a natural scale. When the load is removed, the soil unloading occurs. Both the progress of displacements and soil unloading after unloading of the structure are the key presumptions for evaluating its safety (stability). Assessment of measuring results must be preceded by assuming even the simplest model of the structure, so as it could be possible to estimate the expected displacements under controlled load. In view of clearly random nature of soil parameters of retaining structure composed of reinforced soil and due to specific erection technology of reinforced soil structure, the assessment of its condition is largely based on expert’s judgment. It is an essential and difficult task to interpret very small displacements which are often enough disturbed by numerous factors like temperature, insolation, precipitation, vehicles, etc. In the presented paper, the authors tried to establish and juxtapose some criteria for a load test of a bridge abutment and evaluate their suitability for decision making. Final remarks are based on authors experience from a real full scale load test.

Predictor variable resolution governs modeled soil types

USDA-ARS?s Scientific Manuscript database

Soil mapping identifies different soil types by compressing a unique suite of spatial patterns and processes across multiple spatial scales. It can be quite difficult to quantify spatial patterns of soil properties with remotely sensed predictor variables. More specifically, matching the right scale...

Latent heat sink in soil heat flux measurements

USDA-ARS?s Scientific Manuscript database

The surface energy balance includes a term for soil heat flux. Soil heat flux is difficult to measure because it includes conduction and convection heat transfer processes. Accurate representation of soil heat flux is an important consideration in many modeling and measurement applications. Yet, the...

Latent Heat in Soil Heat Flux Measurements

USDA-ARS?s Scientific Manuscript database

The surface energy balance includes a term for soil heat flux. Soil heat flux is difficult to measure because it includes conduction and convection heat transfer processes. Accurate representation of soil heat flux is an important consideration in many modeling and measurement applications. Yet, the...

Tracing the source of difficult to settle fine particles which cause turbidity in the Hitotsuse Reservoir, Japan.

PubMed

Murakami, Toshiki; Suzuki, Yoshihiro; Oishi, Hiroyuki; Ito, Kenichi; Nakao, Toshio

2013-05-15

A unique method to trace the source of "difficult-to-settle fine particles," which are a causative factor of long-term turbidity in reservoirs was developed. This method is characterized by cluster analysis of XRD (X-ray diffraction) data and homology comparison of major component compositions between "difficult-to-settle fine particles" contained in landslide soil samples taken from the upstream of a dam, and suspended "long-term turbid water particles" in the reservoir, which is subject to long-term turbidity. The experiment carried out to validate the proposed method, demonstrated a high possibility of being able to make an almost identical match between "difficult-to-settle fine particles" taken from landslide soils at specific locations and "long-term turbid water particles" taken from a reservoir. This method has the potential to determine substances causing long-term turbidity and the locations of soils from which those substances came. Appropriate countermeasures can then be taken at those specific locations. Copyright © 2013 Elsevier Ltd. All rights reserved.

Simulation of crop yield variability by improved root-soil-interaction modelling

NASA Astrophysics Data System (ADS)

Duan, X.; Gayler, S.; Priesack, E.

2009-04-01

Understanding the processes and factors that govern the within-field variability in crop yield has attached great importance due to applications in precision agriculture. Crop response to environment at field scale is a complex dynamic process involving the interactions of soil characteristics, weather conditions and crop management. The numerous static factors combined with temporal variations make it very difficult to identify and manage the variability pattern. Therefore, crop simulation models are considered to be useful tools in analyzing separately the effects of change in soil or weather conditions on the spatial variability, in order to identify the cause of yield variability and to quantify the spatial and temporal variation. However, tests showed that usual crop models such as CERES-Wheat and CERES-Maize were not able to quantify the observed within-field yield variability, while their performance on crop growth simulation under more homogeneous and mainly non-limiting conditions was sufficent to simulate average yields at the field-scale. On a study site in South Germany, within-field variability in crop growth has been documented since years. After detailed analysis and classification of the soil patterns, two site specific factors, the plant-available-water and the O2 deficiency, were considered as the main causes of the crop growth variability in this field. Based on our measurement of root distribution in the soil profile, we hypothesize that in our case the insufficiency of the applied crop models to simulate the yield variability can be due to the oversimplification of the involved root models which fail to be sensitive to different soil conditions. In this study, the root growth model described by Jones et al. (1991) was adapted by using data of root distributions in the field and linking the adapted root model to the CERES crop model. The ability of the new root model to increase the sensitivity of the CERES crop models to different enviromental conditions was then evaluated by means of comparison of the simualtion results with measured data and by scenario calculations.

Sampling Soil CO2 for Isotopic Flux Partitioning: Non Steady State Effects and Methodological Biases

NASA Astrophysics Data System (ADS)

Snell, H. S. K.; Robinson, D.; Midwood, A. J.

2014-12-01

Measurements of δ13C of soil CO2 are used to partition the surface flux into autotrophic and heterotrophic components. Models predict that the δ13CO2 of the soil efflux is perturbed by non-steady state (NSS) diffusive conditions. These could be large enough to render δ13CO2 unsuitable for accurate flux partitioning. Field studies sometimes find correlations between efflux δ13CO2 and flux or temperature, or that efflux δ13CO2 is not correlated as expected with biological drivers. We tested whether NSS effects in semi-natural soil were comparable with those predicted. We compared chamber designs and their sensitivity to changes in efflux δ13CO2. In a natural soil mesocosm, we controlled temperature to generate NSS conditions of CO2 production. We measured the δ13C of soil CO2 using in situ probes to sample the subsurface, and dynamic and forced-diffusion chambers to sample the surface efflux. Over eight hours we raised soil temperature by 4.5 OC to increase microbial respiration. Subsurface CO2 concentration doubled, surface efflux became 13C-depleted by 1 ‰ and subsurface CO2 became 13C-enriched by around 2 ‰. Opposite changes occurred when temperature was lowered and CO2 production was decreasing. Different chamber designs had inherent biases but all detected similar changes in efflux δ13CO2, which were comparable to those predicted. Measurements using dynamic chambers were more 13C-enriched than expected, probably due to advection of CO2 into the chamber. In the mesocosm soil, δ13CO2 of both efflux and subsurface was determined by physical processes of CO2 production and diffusion. Steady state conditions are unlikely to prevail in the field, so spot measurements of δ13CO2 and assumptions based on the theoretical 4.4 ‰ diffusive fractionation will not be accurate for estimating source δ13CO2. Continuous measurements could be integrated over a period suitable to reduce the influence of transient NSS conditions. It will be difficult to disentangle biologically driven changes in soil δ13CO2 from physical controls, particularly as they occur on similar timescales and are driven by the same environmental variables, such as temperature, moisture and daylight.

A case study on the method-induced difference in the chemical properties and biodegradability of soil water extractable organic carbon of a granitic forest soil.

PubMed

Wu, Yue; Jiang, Ying

2016-09-15

Water extractable organic carbon (WEOC) plays important roles in soil dissolved organic matter (DOM) research. In the present study, we have detected the chemical properties and biodegradability of WEOC obtained from one granitic forest soil with four commonly used or suggested extraction methods, to study the potential methodological influence in soil DOM research. Results showed great difference in both chemical properties and biodegradation of WEOC from various methods. For the chosen soil, compared to that from fresh soil, WEOC from dried soil contained large proportion of HIN, Base fractions and labile O-alkyl components which might be derived from microbial cell lysis, and showed low fluorescence characteristics, exhibiting great biodegradability. Similarly, WEOC extracted under low temperature and short time conditions showed low fluorescence characteristics and exhibited considerable biodegradability. Conversely, WEOC, which might be potentially subjected to decomposition and loss during extraction, contained higher percentages of HOA fractions and aromatic alkyl and aryl components, and showed high fluorescence characteristics, exhibiting low biodegradability. WEOC extracted in moderate time and temperature showed moderate biodegradability. These method-induced differences implied the direct comparison of the results from similar works is difficult, as we considered here a specific forest soil and other authors other soil types and uses. However, the complexity in comparison reminds that the methodological influence be paid more attention in future soil WEOC researches. Copyright © 2016 Elsevier B.V. All rights reserved.

Attributing spatial and temporal changes in soil C in the UK to environmental drivers

NASA Astrophysics Data System (ADS)

Thomas, Amy; Cosby, Bernard; Quin, Sam; Henrys, Pete; Robinson, David; Emmett, Bridget

2015-04-01

The largest terrestrial pool of carbon is found in soils. Understanding how soil C responds to drivers of change (land use and management, atmospheric deposition, climate change) and how these responses are modified by inherent soil properties is crucial if we are to manage soils more sustainably in the future. Here we attempt to attribute spatial and temporal changes in UK soil C to environmental drivers using data from the UK Countryside Survey (CS), a national soil survey across England, Scotland and Wales repeated in 1978, 1998 and 2007. A mixed model approach was used to model soil C concentration (g C kg-1) and density (t C ha-1) and their absolute changes for the time periods 1978-1998, 1998-2007 and 1978-2007 across the CS sites using a variety of explanatory variables: soil (parent material, pH, moisture, Olsen-P, Shannon Diversity Index); atmospheric deposition (nitrogen and sulphur); climate (growing degree days and rain); and land use (aggregate vegetation class). Spatially, prediction of soil C concentration was good; soil moisture, pH, vegetation class and dominant grain size were all significant predictors. Field capacity also appeared to be important; however this data was only collected for a fraction of sites. N% was also strongly related to soil C concentration and density, as would be expected due to coupling of C and N in soil OM pools. Although N may drive soil C through impact on plant productivity, this cannot be separated from correlated C and N losses with OM decomposition, and hence N was not included as a driver for modelling. Predictive power for C density is not as strong as for concentration, which may reflect nonlinear relationships not represented by the modelling approach. Temporally, change in soil C is more difficult to explain, and model predictive power was lower. Change in soil pH was important in explaining change in C concentration and density, along with change in atmospheric deposition; decrease in deposition and associated soil acidity (increase in pH) was associated with a decrease in soil C concentration and density. Change in soil moisture or rainfall was also important. Inherent soil and site properties such as soil texture, vegetation class and parent material appeared to contribute most to the prediction of soil C change through modulation of the relationship between change in soil C and change in pH. Including anthropogenic and natural drivers in models of soil C stocks and changes in the UK enables assessment of the relative importance of each across the UK CS sites, however interactions among the drivers are more difficult to disentangle. Given the statistical significance of a number of drivers and soil variables in predicting soil C stocks and changes in the UK, it is important that these continue to be measured to allow better model development and more reliable predictions of future soil C conditions.

Household scale of greenhouse design in Merauke

NASA Astrophysics Data System (ADS)

Alahudin, Muchlis; Widarnati, Indah; Luh Sri Suryaningsih, Ni

2018-05-01

Merauke is one of the areas that still use conventional methods in agriculture, The agricultural business does not run the maximum during the year because agricultural products quite difficult to obtain in the market. In the rainy season, the intensity of rain is very high, the water condition is abundant and hard to be channeled due to topography/soil contour conditions average, otherwise in the dry season the water is quite difficult to obtain. The purpose of this research is to compare the thermal conditions between greenhouse with auvplastic and plastic bottle roof.This research is experimental, measurement of thermal conditions in Greenhouse using measuring weather station.Greenhouse design with Quonset type with area of 24 m2The result of this research are greenhouse with paranet + UV plastic roof has an average temperature of 28.7 °C, 70.4% humidity and 0.5 m/s wind speed, while the greenhouse with paranet + plastic bottle roof has an average temperature of 26, 2 °C, humidity 66.4% and wind speed 0.9 m/s. Conclusion is Greenhouse with paranet + plastic bottle roof more thermally comfortable than greenhouse with paranet + UV plastic roof.

EVALUATION OF EXTRACTION AND SPECTROSCOPIC METHODS FOR PB SPECIATION IN AN AMENDED SOIL

EPA Science Inventory

Immobilization of pyromorphite (Pbs(PO4hCI) via P amendments to Pb contaminated soils is proving to be a viable method of remediation. However, the issue of ascertaining the amount of soil Pb converted to pyromorphite is difficult in heterogeneous soil systems. Previous attempts ...

Estimating Soil Hydraulic Parameters using Gradient Based Approach

NASA Astrophysics Data System (ADS)

Rai, P. K.; Tripathi, S.

2017-12-01

The conventional way of estimating parameters of a differential equation is to minimize the error between the observations and their estimates. The estimates are produced from forward solution (numerical or analytical) of differential equation assuming a set of parameters. Parameter estimation using the conventional approach requires high computational cost, setting-up of initial and boundary conditions, and formation of difference equations in case the forward solution is obtained numerically. Gaussian process based approaches like Gaussian Process Ordinary Differential Equation (GPODE) and Adaptive Gradient Matching (AGM) have been developed to estimate the parameters of Ordinary Differential Equations without explicitly solving them. Claims have been made that these approaches can straightforwardly be extended to Partial Differential Equations; however, it has been never demonstrated. This study extends AGM approach to PDEs and applies it for estimating parameters of Richards equation. Unlike the conventional approach, the AGM approach does not require setting-up of initial and boundary conditions explicitly, which is often difficult in real world application of Richards equation. The developed methodology was applied to synthetic soil moisture data. It was seen that the proposed methodology can estimate the soil hydraulic parameters correctly and can be a potential alternative to the conventional method.

Understanding Dynamic Soil Water Repellency and its Hydrological Implications

NASA Astrophysics Data System (ADS)

Beatty, S. M.; Smith, J. E.

2009-05-01

The adverse effects of water repellent soils on vadose zone hydrology are being increasingly identified worldwide in both rural and urban landscapes. Among the affected landscapes are agricultural fields, forests, effluent application sites, golf greens, wetlands, and wildfire sites. In spite of cross-discipline research efforts put forth in recent years, understanding of fundamental parameters controlling soil water behaviour in these systems is lacking. This is due, in part, to inherent complexities of water repellent soil systems and logistical shortcomings of methods commonly used by researchers in-situ and in the lab. As a result, modeling flow in these systems has further proven to be a difficult task. The objectives of our study were 1) to systematically measure and quantify water infiltration and distribution in dynamic water repellent systems and 2) to identify fundamental hydraulic behaviours that lead to the expression of changes in soil water repellency. To achieve this, we combined techniques to elucidate soil- water interactions at a post-wildfire site. Field tests and subsequent lab work reveal essential hydrological information on fire-affected water repellent soils at variable scales and under different burn conditions. Through the use of traditional and newer techniques, our work shows unique and previously unreported behaviour of soil water in these systems. We also address limitations of current field methods used to study repellency and associated infiltration behaviours.

Should there be a "Wet" Soil Order in Soil Taxonomy?

NASA Astrophysics Data System (ADS)

Rabenhorst, Martin; Wessel, Barret; Stolt, Mark; Lindbo, David

2017-04-01

Early soil classification systems recognized wet soils at the highest categorical level. Among the Intrazonal Soils of the US classification utilized between the 1920s and 1960, were included as Great Soil Groups, the Wiesenboden, Bog, Half-Bog, Ground-Water Podzols and Ground-Water Laterites. In other systems, groups named with such terms as ground water gley and pseudogley were also used. With the advent of Soil Taxonomy and it's precursor (1960, 1975), Histosols (organic soils) were distinguished as one of the initial 10 soil orders, and while many of these organic soils are wet soils, some are not (Folists for example). Thus, for over 50 years, with the exception of Histosols, wet soils (which typically represent the wettest end of subaerial wet soils) have not been collectively recognized within taxa at the highest categorical level (order) in the US soil classification system. Rather, the wettest soils were designated at the second categorical level as wet (Aqu) suborders among the various soil orders, and more recently, subaqueous soils as "Wass" suborders of Entisols and Histosols. Soils with less-wet conditions have been recognized at the subgroup (4th) level. Further, in impoundments and regions of transgressing coastlines, submerged upland soils have been found that still classify in soil orders that do not accommodate subaqueous soils ("Wass" suborders). Notwithstanding, other contemporary soil classification systems do (have continued to) recognize wet soils at the highest level. In the World Reference Base (WRB) for example, wet soils are designated as Gleysols or Stagnosols. As efforts are underway to revisit, simplify, and revise Soil Taxonomy, questions have been raised regarding whether wet soils should again be moved back with a place among taxa at the highest category using a name such as Hydrasols, Aquasols, etc. This paper will explore and consider the questions and arguments for and against such proposals and the difficult question regarding where along the soil wetness continuum would be the best point for recognizing a wet soil order.

Element soil behaviour during pile installation simulated by 2D-DEM

NASA Astrophysics Data System (ADS)

Ji, Xiaohui; Cheng, Yi Pik; Liu, Junwei

2017-06-01

The estimation of the skin friction of onshore or offshore piles in sand is still a difficult problem for geotechnical engineers. It has been accepted by many researchers that the mechanism of driving piles in the soil has shared some similarities with that of an element shear test under the constant normal stiffness (CNS) condition. This paper describes the behaviour of an element of soil next to a pile during the process of pile penetration into dense fine sand using the 2D-DEM numerical simulation software. A new CNS servo was added to the horizontal boundary while maintaining the vertical stress constant. This should simulate the soil in a similar manner to that of a CNS pile-soil interface shear test, but allowing the vertical stress to remain constant which is more realistic to the field situation. Shear behaviours observed in these simulations were very similar to the results from previous researchers' lab shearing tests. With the normal stress and shear stress obtained from the virtual models, the friction angle and the shaft friction factor β mentioned in the API-2007 offshore pile design guideline were calculated and compared with the API recommended values.

Phytoremediation of heavy metal copper (Cu2+) by sunflower (Helianthus annuus l.)

NASA Astrophysics Data System (ADS)

Mahardika, G.; Rinanti, A.; Fachrul, M. F.

2018-01-01

A study in microcosmic condition has been carried out to determine the effectiveness of Helianthus annuus as a hyperaccumulator plant for heavy metal, Copper (Cu2+), that exposed in the soil. Artificial pollutants containing Copper (Cu2+) 0, 60, 120, 180 ppm are exposed to uncontaminated soil. The 12-weeks old H. annuus seedling were grown in Cu2+ contaminated soil, with variations of absorption time 3, 6, and 9 weeks. Analysis of Cu2+ concentration on soil and H. annuus (root, stem, leaf) was analised by Atomic Absorbtion Spectrometry (AAS). H. annuus are capable for Cu2+ removal, and the highest removal of Cu2+ is 85.56%, the highest metal accumulation/bioconcentration factor (BCF) is 0.99 occurred at roots with 9 weeks of exposure time and the highest translocation factor (TF) is 0.71. This highest removal is five times better than absorption by stems and leaves. The results concluded, the use of H. annuus for phytoextraction of heavy metals Cu2+ in contaminated soil can be an alternative to the absorption of heavy metal Cu2+ with low concentration metals which is generally very difficult to do in physical-chemical removal.

Mapping CO2 emission in highly urbanized region using standardized microbial respiration approach

NASA Astrophysics Data System (ADS)

Vasenev, V. I.; Stoorvogel, J. J.; Ananyeva, N. D.

2012-12-01

Urbanization is a major recent land-use change pathway. Land conversion to urban has a tremendous and still unclear effect on soil cover and functions. Urban soil can act as a carbon source, although its potential for CO2 emission is also very high. The main challenge in analysis and mapping soil organic carbon (SOC) in urban environment is its high spatial heterogeneity and temporal dynamics. The urban environment provides a number of specific features and processes that influence soil formation and functioning and results in a unique spatial variability of carbon stocks and fluxes at short distance. Soil sealing, functional zoning, settlement age and size are the predominant factors, distinguishing heterogeneity of urban soil carbon. The combination of these factors creates a great amount of contrast clusters with abrupt borders, which is very difficult to consider in regional assessment and mapping of SOC stocks and soil CO2 emission. Most of the existing approaches to measure CO2 emission in field conditions (eddy-covariance, soil chambers) are very sensitive to soil moisture and temperature conditions. They require long-term sampling set during the season in order to obtain relevant results. This makes them inapplicable for the analysis of CO2 emission spatial variability at the regional scale. Soil respiration (SR) measurement in standardized lab conditions enables to overcome this difficulty. SR is predominant outgoing carbon flux, including autotrophic respiration of plant roots and heterotrophic respiration of soil microorganisms. Microbiota is responsible for 50-80% of total soil carbon outflow. Microbial respiration (MR) approach provides an integral CO2 emission results, characterizing microbe CO2 production in optimal conditions and thus independent from initial difference in soil temperature and moisture. The current study aimed to combine digital soil mapping (DSM) techniques with standardized microbial respiration approach in order to analyse and map CO2 emission and its spatial variability in highly urbanized Moscow region. Moscow region with its variability of bioclimatic conditions and high urbanization level (10 % from the total area) was chosen as an interesting case study. Random soil sampling in different soil zones (4) and land-use types (3 non-urban and 3 urban) was organized in Moscow region in 2010-2011 (n=242). Both topsoil (0-10 cm) and subsoil (10-150 cm) were included. MR for each point was analysed using standardized microbial (basal) respiration approach, including the following stages: 1) air dried soil samples were moisturised up to 55% water content and preincubated (7 days, 22° C) in a plastic bag with air exchange; 2) soil MR (in μg CO2-C g-1) was measured as the rate of CO2 production (22° C, 24 h) after incubating 2g soil with 0.2 μl distilled water; 3) the MR results were used to estimate CO2 emission (kg C m-2 yr-1). Point MR and CO2 emission results obtained were extrapolated for the Moscow region area using regression model. As a result, two separate CO2 maps for topsoil and subsoil were created. High spatial variability was demonstrated especially for the urban areas. Thus standardized MR approach combined with DSM techniques provided a unique opportunity for spatial analysis of soil carbon temporal dynamics at the regional scale.

Clay-cement suspensions - rheological and functional properties

NASA Astrophysics Data System (ADS)

Wojcik, L.; Izak, P.; Mastalska-Poplawska, J.; Gajek, M.

2017-01-01

The piping erosion in soil is highly unexpected in civil engineering. Elimination of such damages is difficult, expensive and time-consuming. One of the possibility is the grouting method. This method is still developed into direction of process automation as well as other useful properties of suspensions. Main way of modernization of the grouting method is connected it with rheology of injection and eventuality of fitting them to specific problems conditions. Very popular and useful became binders based on modified clays (clay-cement suspensions). Important principle of efficiency of the grouting method is using of time-dependent pseudothixotropic properties of the clay-cement suspensions. The pseudo-rheounstability aspect of the suspensions properties should be dedicated and fitted to dynamic changes of soil conditions destructions. Whole process of the modification of the suspension rheology is stimulated by the specific agents. This article contains a description of practical aspects of the rheological parameters managing of the clay-cement suspensions, dedicated to the building damages, hydrotechnic constructions etc.

Computer-Controlled Microwave Drying of Potentially Difficult Organic and Inorganic Soils

DTIC Science & Technology

1990-12-01

materials, fly ash, gypsum rich soils, calcite rich soils, organic clay,, peat, and halloysite rich soils. Because specimen sizes too large to be...measurement Field monitoring equipment User’s manual 19. A3STRACT (Continued). materials, organic clay, fly ash, and calcite rich soils are demonstrated...39 Factors Influencing Dehydration ..................................... 42 PART X: STUDIES OF CALCITE

Soil moisture gradients and controls on a southern Appalachian hillslope from drought through recharge

Treesearch

J.A. Yeakley; W.T. Swank; L.W. Swift; G.M. Hornberger; H.H. Shugart

1998-01-01

Soil moisture gradients along hillslopes in humid watersheds, although indicated by vegetation gradients and by studies using models, have been difficult to confirm empirically. While soil properties and topographic features are the two general physiographic factors controlling soil moisture on hillslopes, studies have shown conflicting results regarding which factor...

An Inexpensive and Simple Method to Demonstrate Soil Water and Nutrient Flow

ERIC Educational Resources Information Center

Nichols, K. A.; Samson-Liebig, S.

2011-01-01

Soil quality, soil health, and soil sustainability are concepts that are being widely used but are difficult to define and illustrate, especially to a non-technical audience. The objectives of this manuscript were to develop simple and inexpensive methodologies to both qualitatively and quantitatively estimate water infiltration rates (IR),…

Topographic, edaphic, and vegetative controls on plant-available water

Treesearch

Salli F. Dymond; John B. Bradford; Paul V. Bolstad; Randall K. Kolka; Stephen D. Sebestyen; Thomas M. DeSutter

2017-01-01

Soil moisture varies within landscapes in response to vegetative, physiographic, and climatic drivers, which makes quantifying soil moisture over time and space difficult. Nevertheless, understanding soil moisture dynamics for different ecosystems is critical, as the amount of water in a soil determines a myriad ecosystem services and processes such as net primary...

A conceptual model of the controlling factors of soil organic carbon and nitrogen densities in a permafrost-affected region on the eastern Qinghai-Tibetan Plateau

NASA Astrophysics Data System (ADS)

Wu, Xiaodong; Fang, Hongbing; Zhao, Yonghua; Smoak, Joseph M.; Li, Wangping; Shi, Wei; Sheng, Yu; Zhao, Lin; Ding, Yongjian

2017-07-01

Many investigations of the preservation of soil organic carbon (SOC) in permafrost regions have examined roles of geomorphology, pedogenesis, vegetation cover, and permafrost within particular regions. However, it is difficult to disentangle the effects of multiple factors on the SOC in permafrost regions due to the heterogeneity in environmental conditions. Based on data from 73 soil study sites in permafrost regions of the eastern Qinghai-Tibetan Plateau, we developed a simple conceptual model, which relates SOC to topography, vegetation, and pedogenesis. We summarized the dominant factors and their controls on SOC using 31 measured soil physiochemical variables. Soil texture explains approximately 60% of the variations in the SOC stocks for the upper 0-2 m soil. Soil particle size closely correlates to soil moisture, which is an important determinant of SOC. Soil salinity and cations are important factors as well and can explain about 10% of the variations in SOC. The SOC and total nitrogen (TN) stocks for the 1-2 m depths have larger uncertainties than those of upper 1 m soil layer. The vegetation, pH, and bulk density mainly affects SOC and TN stocks for the upper 1 m soil layers, while the active layer thickness and soil particle size have greater influence on SOC and TN stocks for the 1-2 m soils. Our results suggest that the soil particle size is the most important controller of SOC pools, and the stocks of SOC and TN are strongly effected by soil development processes in the permafrost regions of the eastern Qinghai-Tibetan Plateau.

Soil Parameter Mapping and Ad Hoc Power Analysis to Increase Blocking Efficiency Prior to Establishing a Long-Term Field Experiment.

PubMed

Collins, Doug; Benedict, Chris; Bary, Andy; Cogger, Craig

2015-01-01

The spatial heterogeneity of soil and weed populations poses a challenge to researchers. Unlike aboveground variability, below-ground variability is more difficult to discern without a strategic soil sampling pattern. While blocking is commonly used to control environmental variation, this strategy is rarely informed by data about current soil conditions. Fifty georeferenced sites were located in a 0.65 ha area prior to establishing a long-term field experiment. Soil organic matter (OM) and weed seed bank populations were analyzed at each site and the spatial structure was modeled with semivariograms and interpolated with kriging to map the surface. These maps were used to formulate three strategic blocking patterns and the efficiency of each pattern was compared to a completely randomized design and a west to east model not informed by soil variability. Compared to OM, weeds were more variable across the landscape and had a shorter range of autocorrelation, and models to increase blocking efficiency resulted in less increase in power. Weeds and OM were not correlated, so no model examined improved power equally for both parameters. Compared to the west to east blocking pattern, the final blocking pattern chosen resulted in a 7-fold increase in power for OM and a 36% increase in power for weeds.

A Method for Precision Closed-Loop Irrigation Using a Modified PID Control Algorithm

NASA Astrophysics Data System (ADS)

Goodchild, Martin; Kühn, Karl; Jenkins, Malcolm; Burek, Kazimierz; Dutton, Andrew

2016-04-01

The benefits of closed-loop irrigation control have been demonstrated in grower trials which show the potential for improved crop yields and resource usage. Managing water use by controlling irrigation in response to soil moisture changes to meet crop water demands is a popular approach but requires knowledge of closed-loop control practice. In theory, to obtain precise closed-loop control of a system it is necessary to characterise every component in the control loop to derive the appropriate controller parameters, i.e. proportional, integral & derivative (PID) parameters in a classic PID controller. In practice this is often difficult to achieve. Empirical methods are employed to estimate the PID parameters by observing how the system performs under open-loop conditions. In this paper we present a modified PID controller, with a constrained integral function, that delivers excellent regulation of soil moisture by supplying the appropriate amount of water to meet the needs of the plant during the diurnal cycle. Furthermore, the modified PID controller responds quickly to changes in environmental conditions, including rainfall events which can result in: controller windup, under-watering and plant stress conditions. The experimental work successfully demonstrates the functionality of a constrained integral PID controller that delivers robust and precise irrigation control. Coir substrate strawberry growing trial data is also presented illustrating soil moisture control and the ability to match water deliver to solar radiation.

Influence of throughfall spatial and temporal patterns on soil moisture variability under Downy oak and Scots pine stands in Mediterranean conditions

NASA Astrophysics Data System (ADS)

Llorens, Pilar; Garcia-Estringana, Pablo; Cayuela, Carles; Latron, Jérôme; Molina, Antonio; Gallart, Francesc

2015-04-01

Temporal and spatial variability of throughfall and stemflow patterns, due to differences in forest structure and seasonality of Mediterranean climate, may lead to significant changes in the volume of water that locally reaches the soil, with a potential effect on groundwater recharge and on hydrological response of forested hillslopes. Two forest stands in Mediterranean climatic conditions were studied to explore the role of vegetation on the temporal and spatial redistribution of rainfall. One is a Downy oak forest (Quercus pubescens) and the other is a Scots pine forest (Pinus sylvestris), both located in the Vallcebre research catchments (NE Spain, 42° 12'N, 1° 49'E). These plots are representative of Mediterranean mountain areas with spontaneous afforestation by Scots pine as a consequence of the abandonment of agricultural terraces, formerly covered by Downy oaks. The monitoring design of each plot consists of 20 automatic rain recorders to measuring throughfall, 7 stemflow rings connected to tipping-buckets and 40 automatic soil moisture probes. All data were recorded each 5 min. Bulk rainfall and meteorological conditions above both forest covers were also recorded, and canopy cover and biometric characteristics of the plots were measured. Results indicate a marked temporal stability of throughfall in both stands, and a lower persistence of spatial patterns in the leafless period than in the leafed one in the oaks stand. Moreover, in the oaks plot the ranks of gauges in the leafed and leafless periods were not significantly correlated, indicating different wet and dry hotspots in each season. The spatial distribution of throughfall varied significantly depending on rainfall volume, with small events having larger variability, whereas large events tended to homogenize the relative differences in point throughfall. Soil water content spatial variability increased with increasing soil water content, but direct dependence of soil water content variability on throughfall patterns is difficult to establish.

A highly efficient nonchemical method for isolating live nematodes (Caenorhabditis elegans) from soil during toxicity assays.

PubMed

Kim, Shin Woong; Moon, Jongmin; An, Youn-Joo

2015-01-01

The success of soil toxicity tests using Caenorhabditis elegans may depend in large part on recovering the organisms from the soil. However, it can be difficult to learn the International Organization for Standardization/ASTM International recovery process that uses the colloidal silica flotation method. The present study determined that a soil-agar isolation method provides a highly efficient and less technically demanding alternative to the colloidal silica flotation method. Test soil containing C. elegans was arranged on an agar plate in a donut shape, a linear shape, or a C curve; and microbial food was placed outside the soil to encourage the nematodes to leave the soil. The effects of ventilation and the presence of food on nematode recovery were tested to determine the optimal conditions for recovery. A linear arrangement of soil on an agar plate that was sprinkled with microbial food produced nearly 83% and 90% recovery of live nematodes over a 3-h and a 24-h period, respectively, without subjecting the nematodes to chemical stress. The method was tested using copper (II) chloride dihydrate, and the resulting recovery rate was comparable to that obtained using colloidal silica flotation. The soil-agar isolation method portrayed in the present study enables live nematodes to be isolated with minimal additional physicochemical stress, making it a valuable option for use in subsequent sublethal tests where live nematodes are required. © 2014 SETAC.

Soil Bulk Density by Soil Type, Land Use and Data Source: Putting the Error in SOC Estimates

NASA Astrophysics Data System (ADS)

Wills, S. A.; Rossi, A.; Loecke, T.; Ramcharan, A. M.; Roecker, S.; Mishra, U.; Waltman, S.; Nave, L. E.; Williams, C. O.; Beaudette, D.; Libohova, Z.; Vasilas, L.

2017-12-01

An important part of SOC stock and pool assessment is the assessment, estimation, and application of bulk density estimates. The concept of bulk density is relatively simple (the mass of soil in a given volume), the specifics Bulk density can be difficult to measure in soils due to logistical and methodological constraints. While many estimates of SOC pools use legacy data in their estimates, few concerted efforts have been made to assess the process used to convert laboratory carbon concentration measurements and bulk density collection into volumetrically based SOC estimates. The methodologies used are particularly sensitive in wetlands and organic soils with high amounts of carbon and very low bulk densities. We will present an analysis across four database measurements: NCSS - the National Cooperative Soil Survey Characterization dataset, RaCA - the Rapid Carbon Assessment sample dataset, NWCA - the National Wetland Condition Assessment, and ISCN - the International soil Carbon Network. The relationship between bulk density and soil organic carbon will be evaluated by dataset and land use/land cover information. Prediction methods (both regression and machine learning) will be compared and contrasted across datasets and available input information. The assessment and application of bulk density, including modeling, aggregation and error propagation will be evaluated. Finally, recommendations will be made about both the use of new data in soil survey products (such as SSURGO) and the use of that information as legacy data in SOC pool estimates.

Monitoring, analysis and classification of vegetation and soil data collected by a small and lightweight hyperspectral imaging system

NASA Astrophysics Data System (ADS)

Mönnig, Carsten

2014-05-01

The increasing precision of modern farming systems requires a near-real-time monitoring of agricultural crops in order to estimate soil condition, plant health and potential crop yield. For large sized agricultural plots, satellite imagery or aerial surveys can be used at considerable costs and possible time delays of days or even weeks. However, for small to medium sized plots, these monitoring approaches are cost-prohibitive and difficult to assess. Therefore, we propose within the INTERREG IV A-Project SMART INSPECTORS (Smart Aerial Test Rigs with Infrared Spectrometers and Radar), a cost effective, comparably simple approach to support farmers with a small and lightweight hyperspectral imaging system to collect remotely sensed data in spectral bands in between 400 to 1700nm. SMART INSPECTORS includes the whole remote sensing processing chain of small scale remote sensing from sensor construction, data processing and ground truthing for analysis of the results. The sensors are mounted on a remotely controlled (RC) Octocopter, a fixed wing RC airplane as well as on a two-seated Autogyro for larger plots. The high resolution images up to 5cm on the ground include spectra of visible light, near and thermal infrared as well as hyperspectral imagery. The data will be analyzed using remote sensing software and a Geographic Information System (GIS). The soil condition analysis includes soil humidity, temperature and roughness. Furthermore, a radar sensor is envisaged for the detection of geomorphologic, drainage and soil-plant roughness investigation. Plant health control includes drought stress, vegetation health, pest control, growth condition and canopy temperature. Different vegetation and soil indices will help to determine and understand soil conditions and plant traits. Additional investigation might include crop yield estimation of certain crops like apples, strawberries, pasture land, etc. The quality of remotely sensed vegetation data will be tested with ground truthing tools like a spectrometer, visual inspection and ground control panel. The soil condition will also be monitored with a wireless sensor network installed on the examined plots of interest. Provided with this data, a farmer can respond immediately to potential threats with high local precision. In this presentation, preliminary results of hyperspectral images of distinctive vegetation cover and soil on different pasture test plots are shown. After an evaluation period, the whole processing chain will offer farmers a unique, near real- time, low cost solution for small to mid-sized agricultural plots in order to easily assess crop and soil quality and the estimation of harvest. SMART INSPECTORS remotely sensed data will form the basis for an input in a decision support system which aims to detect crop related issues in order to react quickly and efficiently, saving fertilizer, water or pesticides.

Soil Properties and the Conditions for Recurring Earthflow Failure

NASA Astrophysics Data System (ADS)

Davila Olivera, S.; Nereson, A. L.; Finnegan, N. J.

2017-12-01

In the California Coast Ranges, earthflows are major contributors to sediment transport on hillslopes and have dramatic impacts on rivers and infrastructure. Earthflows are notable for slow-movement (1-10 m/yr) that can be persistent or recurring over long periods of time (102 -103 yrs). While the physical underpinnings for this type of movement remain difficult to determine in natural settings, the slow, steady motion of an earthflow implies that at least two mechanisms must be at work: 1) a mechanism that localizes failure at the same place on the hillslope year-after-year, and 2) a mechanism that arrests the motion of the landslide and prevents runaway acceleration. In this study, we focused on the first mechanism and test the "bathtub model" (Baum and Reid,2000). According to this model, a concentration of fine-grained material in the shear zone of a slide locally reduces soil shear strength and lowers hydraulic conductivity. These effects result in the hydrologic and mechanical isolation of the slide mass, causing the landslide to fill with water (like a bathtub) during precipitation events. We wanted to investigate the role of `bathtub-like" conditions at a long-lived (>80 yrs) earthflow located 20 km northeast of San Jose, CA known as the Oak Ridge Earthflow. Towards that end, we collected and analyzed soil samples. Our work included 1) measurements of the soil particle size distribution in the shear zone, landslide body, and stable ground (given that soil grain size exerts a first-order control on hydraulic conductivity), 2) measurements of water content at the end of the dry season to observe patterns of water retention within the slide and 3) determination of Atterberg limits and soil textures that can be empirically correlated with other useful soil properties, such as strength and hydraulic conductivity, two qualities that define this hypothesis. In the shear zone, we found the soil to be weak, fine-grained (D10 = 0.04 mm), and of low-hydraulic conductivity (calculated K = 6.25x10-8 m/s), relative to the coarse (D10 = 0.14-1.4 mm), permeable (calculated K = 6.0x10-7 m/s) sediments in the slide body and stable slopes adjacent to the earthflow. Overall, soil textural data and soil properties determined by correlation with the Atterberg limits tentatively support the influence of 'bathtub-like" conditions at this site.

Soil characteristics and heavy metal accumulation by native plants in a Mn mining area of Guangxi, South China.

PubMed

Liu, Jie; Zhang, Xue-hong; Li, Tian-yu; Wu, Qing-xin; Jin, Zhen-jiang

2014-04-01

Revegetation and ecological restoration of a Mn mineland are important concerns in southern China. To determine the major constraints for revegetation and select suitable plants for phytorestoration, pedological and botanical characteristics of a Mn mine in Guangxi, southern China were investigated. All the soils were characterized by low pH and low nitrogen and phosphorus levels except for the control soil, suggesting that soil acidity and poor nutrition were disadvantageous to plant growth. In general, the studied mine soils had normal organic matter (OM) and cation exchange capacity (CEC). However, OM (8.9 g/kg) and CEC (7.15 cmol/kg) were very low in the soils from tailing dumps. The sandy texture and nutrient deficiency made it difficult to establish vegetation on tailing dumps. Mn and Cd concentrations in all soils and Cr and Zn concentrations in three soils exceeded the pollution threshold. Soil Mn and Cd were above phytotoxic levels, indicating that they were considered to be the major constraints for phytorestoration. A botanical survey of the mineland showed that 13 plant species grew on the mineland without obvious toxicity symptoms. High Mn and Cd concentrations have been found in the aerial parts of Polygonum pubescens, Celosia argentea, Camellia oleifera, and Solanum nigrum, which would be interesting for soil phytoremediation. Miscanthus floridulus, Erigeron acer, Eleusina indica, and Kummerowia striata showed high resistance to the heavy metal and harsh condition of the soils. These species could be well suited to restore local degraded land in a phytostabilization strategy.

Numerical investigations of triggering mechanisms of shallow landslides due to heterogeneous spatio-temporal hydrological patterns.

NASA Astrophysics Data System (ADS)

Schwarz, Massimiliano; Cohen, Denis

2016-04-01

Rainfall is one of the major triggering factor of shallow landslide around the world. The increase of soil moisture in the soil influences the stability of a slope through the increase of soil bulk density, the reduction of soil apparent cohesion (due to suction stress), and the increase in pore water pressure.The spatio-temporal transformations of such properties of soil are know to be heterogeneous and under constant change. For instance, there may be a condition where, in cracked clay-soil, water, during a rain event, produces a rapid increase of pore water pressure along preferential flow-paths (crack or roots), while soil moisture and suction within the soil matrix change minimally. An another site in a sandy soil, the situation might be very different where the increase of soil moisture and pore water pressure, and the decrease of soil suction take place more or less simultaneously across the entire soil profile. In both of these cases topography plays a major role in determining the accumulation of water along the slope through different subsurface flows intensities and directions. In many documented cases in the Alps, shallow landslides may also be triggered by the punctual exfiltration of water from bedrock or weathered geological strata. The hydro-geological characteristics of the catchment control this mechanism. These different situations aim to give an idea of the large spectrum of hydrological triggering conditions of shallow landslides. The heterogeneities of these hydrological conditions represent a difficult issue in modeling shallow landslide triggering mechanisms. In the simplest models, hydrology is assumed to influence changes in pore water pressure only, mostly using one dimensional vertical infiltration models. More advanced models consider changes in apparent cohesion due to changes in soil moisture or include more complex hydrological models to simulate water flow and distribution during a rainfall event. However, most models at the regional scale rely on the infinite slope assumption for stability calculations and on continuous hydrological properties of the soil. The objective of the present study is to investigate the influence of non-continuos hydrological features (such as ephemeral springs) on the triggering mechanisms of shallow landslides using a discrete element model (SOSlope) in which the stress-strain behavior of soil is explicitly considered. The application of a stress-strain calculation allows for the simulation of local versus global loading due to hydrological processes. In particular, this study investigates the effects of different types of hydrological loading on the force redistribution on a slope associated with local displacements and following failures of soil masses. Strength and stiffness of soil are considered heterogeneous and are calculated based on the assumption of root distributions within a forested hillslope.

Effect of heat on soil color and pH of two forest soils.

Treesearch

Robert F. Tarrant

1953-01-01

Intensity of a slash burn is often judged by the change in soil color. Reddened or yellowed areas of soil and charred patches of organic litter are found on most burned areas, but such color changes are difficult to interpret. A study was therefore made to explore two questions: (1) At what temperature does the color of mineral soil change to the...

Thresholds for soil cover and weathering in mountainous landscapes

NASA Astrophysics Data System (ADS)

Dixon, Jean; Benjaram, Sarah

2017-04-01

The patterns of soil formation, weathering, and erosion shape terrestrial landscapes, forming the foundation on which ecosystems and human civilizations are built. Several fundamental questions remain regarding how soils evolve, especially in mountainous landscapes where tectonics and climate exert complex forcings on erosion and weathering. In these systems, quantifying weathering is made difficult by the fact that soil cover is discontinuous and heterogeneous. Therefore, studies that attempt to measure soil weathering in such systems face a difficult bias in measurements towards more weathered portions of the landscape. Here, we explore current understanding of erosion-weathering feedbacks, and present new data from mountain systems in Western Montana. Using field mapping, analysis of LiDAR and remotely sensed land-cover data, and soil chemical analyses, we measure soil cover and surface weathering intensity across multiple spatial scales, from the individual soil profile to a landscape perspective. Our data suggest that local emergence of bedrock cover at the surface marks a landscape transition from supply to kinetic weathering regimes in these systems, and highlights the importance of characterizing complex critical zone architecture in mountain landscapes. This work provides new insight into how landscape morphology and erosion may drive important thresholds for soil cover and weathering.

Uptake of explosives from contaminated soil by existing vegetation at the Joliet Army Ammunition Plant

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

Schneider, J.F.; Tomczyk, N.A.; Zellmer, S.D.

1994-01-01

This study examines the uptake of explosives by existing vegetation growing in TNT-contaminated soils on Group 61 at the Joliet Army Ammunition Plant (JAAP). The soils in this group were contaminated more than 40 years ago. In this study, existing plant materials and soil from the root zone were sampled from 15 locations and analyzed to determine TNT uptake by plants under natural field conditions. Plant materials were separated by species if more than one species was present at a sampling location. Standard methods were used to determine concentrations of explosives, their derivatives, and metabolites in the soil samples. Plantmore » materials were also analyzed. No. explosives were detected in the aboveground portion of any plant sample. However, the results indicate that TNT, 2-amino DNT, and/or 4-amino DNT were found in some root samples of false boneset (Kuhnia eupatorioides), teasel (Dipsacus sylvestris), and bromegrass (Bromus inermis). It is possible that slight soil contamination remained on the roots, especially in the case of the very fine roots for species like bromegrass, where washing was difficult. The presence of 2-amino DNT and 4-amino DNT, which could be plant metabolites of TNT, increases the likelihood that explosives were taken up by plant roots, as opposed to their presence resulting from external soil contamination.« less

Quantifying Forest Soil Physical Variables Potentially Important for Site Growth Analyses

Treesearch

John S. Kush; Douglas G. Pitt; Phillip J. Craul; William D. Boyer

2004-01-01

Accurate mean plot values of forest soil factors are required for use as independent variables in site-growth analyses. Adequate accuracy is often difficult to attain because soils are inherently widely variable. Estimates of the variability of appropriate soil factors influencing growth can be used to determine the sampling intensity required to secure accurate mean...

Shallow Horizontal GCHP Effectiveness in Arid Climate Soils

NASA Astrophysics Data System (ADS)

North, Timothy James

Ground coupled heat pumps (GCHPs) have been used successfully in many environments to improve the heating and cooling efficiency of both small and large scale buildings. In arid climate regions, such as the Phoenix, Arizona metropolitan area, where the air condi-tioning load is dominated by cooling in the summer, GCHPs are difficult to install and operate. This is because the nature of soils in arid climate regions, in that they are both dry and hot, renders them particularly ineffective at dissipating heat. The first part of this thesis addresses applying the SVHeat finite element modeling soft-ware to create a model of a GCHP system. Using real-world data from a prototype solar-water heating system coupled with a ground-source heat exchanger installed in Menlo Park, California, a relatively accurate model was created to represent a novel GCHP panel system installed in a shallow vertical trench. A sensitivity analysis was performed to evaluate the accuracy of the calibrated model. The second part of the thesis involved adapting the calibrated model to represent an ap-proximation of soil conditions in arid climate regions, using a range of thermal properties for dry soils. The effectiveness of the GCHP in the arid climate region model was then evaluated by comparing the thermal flux from the panel into the subsurface profile to that of the prototype GCHP. It was shown that soils in arid climate regions are particularly inefficient at heat dissipation, but that it is highly dependent on the thermal conductivity inputted into the model. This demonstrates the importance of proper site characterization in arid climate regions. Finally, several soil improvement methods were researched to evaluate their potential for use in improving the effectiveness of shallow horizontal GCHP systems in arid climate regions.

Amplifying the benefits of agroecology by using the right cultivars.

PubMed

Noguera, D; Laossi, K-R; Lavelle, P; De Carvalho, M H Cruz; Asakawa, N; Botero, C; Barot, S

2011-10-01

Tropical soils are particularly vulnerable to fertility losses due to their low capacity to retain organic matter and mineral nutrients. This urges the development of new agricultural practices to manage mineral nutrients and organic matter in a more sustainable way while relying less on fertilizer inputs. Two methods pertaining to ecological engineering and agroecology have been tested with some success: (1) the addition of biochar to the soil, and (2) the maintenance of higher earthworm densities. However, modern crop varieties have been selected to be adapted to agricultural practices and to the soil conditions they lead to and common cultivars might not be adapted to new practices. Using rice as a model plant, we compared the responsiveness to biochar and earthworms of five rice cultivars with contrasted selection histories. These cultivars had contrasted responsivenesses to earthworms, biochar, and the combination of both. The mean relative increase in grain biomass, among all treatments and cultivars, was 94% and 32%, respectively, with and without fertilization. Choosing the best combination of cultivar and treatment led to a more than fourfold increase in this mean benefit (a 437% and a 353% relative increase in grain biomass, respectively, with and without fertilization). Besides, the more rustic cultivar, a local landrace adapted to diverse and difficult conditions, responded the best to earthworms in terms of total biomass, while a modern common cultivar responded the best in term of grain biomass. This suggests that cultivars could be selected to amplify the benefit of biochar- and earthworm-based practices. Overall, selecting new cultivars interacting more closely with soil organisms and soil heterogeneity could increase agriculture sustainability, fostering the positive feedback loop between soils and plants that has evolved in natural ecosystems.

Utilization of data and modeling at multiple scales to compare varying formulations of the soil resistance term affecting evaporative flux from the soil surface.

NASA Astrophysics Data System (ADS)

Smits, K. M.; Forsythe, L.; Riley, W. J.; Bisht, G.

2016-12-01

Land Surface Models (LSMs) are used to predict heat, energy, and momentum fluxesoccurring at the land surface and the resulting effects in the soil and atmosphere at various scales.Evaporation from bare soil is an integral component of the water balance that is very difficult toaccurately predict since it is complexly affected by the coupled effects of atmospheric conditions andsoil properties. Inaccurate or simplifying assumptions can have drastic effects on regional and globalLSM predictions and cause available LSMs to predict conflicting values for the soil moistureconditions and surface fluxes (e.g. evapotranspiration, infiltration, run off). The goal of this work isto see how heterogeneities in soil properties can be properly represented with a soil resistance termthat accounts for physically based parameters of the soil system at the land-atmosphere interface.Utilizing a comprehensive, experimental dataset generated from a soil with known, heterogeneousproperties under highly controlled atmospheric conditions, we are able to compare the effectivenessof various parameterizations in two different models. The first being a multiphase, non-equilibrium,and non-isothermal model that minimizes the dependence on fitting parameters. The effects ofcertain mechanisms are better understood at this fine scale and incorporated into the land surfacecomponent of the Accelerated Climate Modeling for Energy project (ALM), which is focused oncapturing the interactions between the surface and the atmosphere at larger scales. The formulationsof the resistance parameter, soil water retention curve (SWRC), and diffusivity through partiallysaturated porous media are of particular interest. The fine scale model was used in conjunction withthe experimental data to test formulations before implementing them into the ACME Land Model(ALM). Effects of these alterations were compared to the existing mechanisms in ALM and thentested against lab and field scale data sets. Initial findings suggest the Tang and Riley (2013a) soilresistance more accurately reproduces results lab and field results on multiple scales whereheterogeneity is present. Further understanding of soil resistance will lead to more robust landsurface models which decrease the reliance on such empirical relationships.

Nonlinear soil parameter effects on dynamic embedment of offshore pipeline on soft clay

NASA Astrophysics Data System (ADS)

Yu, Su Young; Choi, Han Suk; Lee, Seung Keon; Park, Kyu-Sik; Kim, Do Kyun

2015-06-01

In this paper, the effects of nonlinear soft clay on dynamic embedment of offshore pipeline were investigated. Seabed embedment by pipe-soil interactions has impacts on the structural boundary conditions for various subsea structures such as pipeline, riser, pile, and many other systems. A number of studies have been performed to estimate real soil behavior, but their estimation of seabed embedment has not been fully identified and there are still many uncertainties. In this regards, comparison of embedment between field survey and existing empirical models has been performed to identify uncertainties and investigate the effect of nonlinear soil parameter on dynamic embedment. From the comparison, it is found that the dynamic embedment with installation effects based on nonlinear soil model have an influence on seabed embedment. Therefore, the pipe embedment under dynamic condition by nonlinear parameters of soil models was investigated by Dynamic Embedment Factor (DEF) concept, which is defined as the ratio of the dynamic and static embedment of pipeline, in order to overcome the gap between field embedment and currently used empirical and numerical formula. Although DEF through various researches is suggested, its range is too wide and it does not consider dynamic laying effect. It is difficult to find critical parameters that are affecting to the embedment result. Therefore, the study on dynamic embedment factor by soft clay parameters of nonlinear soil model was conducted and the sensitivity analyses about parameters of nonlinear soil model were performed as well. The tendency on dynamic embedment factor was found by conducting numerical analyses using OrcaFlex software. It is found that DEF was influenced by shear strength gradient than other factors. The obtained results will be useful to understand the pipe embedment on soft clay seabed for applying offshore pipeline designs such as on-bottom stability and free span analyses.

Heat pulse probe measurements of soil water evaporation in a corn field

USDA-ARS?s Scientific Manuscript database

Latent heat fluxes from cropped fields consist of soil water evaporation and plant transpiration. It is difficult to accurately separate evapotranspiration into evaporation and transpiration. Heat pulse probes have been used to measure bare field subsurface soil water evaporation, however, the appl...

On the formation of glide-snow avalanches

NASA Astrophysics Data System (ADS)

Mitterer, C.; Schweizer, J.

2012-12-01

On steep slopes the full snowpack can glide on the ground; tension cracks may open and eventually the slope may fail as a glide-snow avalanche. Due to their large mass they have considerable destructive potential. Glide-snow avalanches typically occur when the snow-soil interface is moist or wet so that basal friction is reduced. The occurrence, however, of glide cracks and their evolution to glide avalanches are still poorly understood. Consequently, glides are difficult to predict as (i) not all cracks develop into an avalanche, and (ii) for those that do, the time between crack opening and avalanche event might vary from hours to weeks - or on the other hand be so short that there is no warning at all by crack opening. To improve our understanding we monitored several slopes and related glide snow activity to meteorological data. In addition, we explored conditions that favor the formation of a thin wet basal snowpack layer with a physical-based model representing water and heat flux at the snow-soil interface. The statistical analyses revealed that glide-snow avalanche activity might be associated to an early season and a spring condition. While early season conditions tend to have warm and dry autumns followed by heavy snowfalls, spring conditions showed good agreement with increasing air temperature. The model indicates that energy (summer heat) stored in the ground might be sufficient to melt snow at the bottom of the snowpack. Due to capillary forces, water will rise for a few centimeters into the snowpack and thereby reduce friction at the interface. Alternatively, we demonstrate that also in the absence of melt water production at the bottom of the snowpack water may accumulate in the bottom layer due to an upward flux into the snowpack if a dry snowpack overlies a wet soil. The particular conditions that are obviously required at the snow-soil interface explain the strong winter-to-winter variations in snow gliding.

Mercury deposition and re-emission pathways in boreal forest soils investigated with Hg isotope signatures.

PubMed

Jiskra, Martin; Wiederhold, Jan G; Skyllberg, Ulf; Kronberg, Rose-Marie; Hajdas, Irka; Kretzschmar, Ruben

2015-06-16

Soils comprise the largest terrestrial mercury (Hg) pool in exchange with the atmosphere. To predict how anthropogenic emissions affect global Hg cycling and eventually human Hg exposure, it is crucial to understand Hg deposition and re-emission of legacy Hg from soils. However, assessing Hg deposition and re-emission pathways remains difficult because of an insufficient understanding of the governing processes. We measured Hg stable isotope signatures of radiocarbon-dated boreal forest soils and modeled atmospheric Hg deposition and re-emission pathways and fluxes using a combined source and process tracing approach. Our results suggest that Hg in the soils was dominantly derived from deposition of litter (∼90% on average). The remaining fraction was attributed to precipitation-derived Hg, which showed increasing contributions in older, deeper soil horizons (up to 27%) indicative of an accumulation over decades. We provide evidence for significant Hg re-emission from organic soil horizons most likely caused by nonphotochemical abiotic reduction by natural organic matter, a process previously not observed unambiguously in nature. Our data suggest that Histosols (peat soils), which exhibit at least seasonally water-saturated conditions, have re-emitted up to one-third of previously deposited Hg back to the atmosphere. Re-emission of legacy Hg following reduction by natural organic matter may therefore be an important pathway to be considered in global models, further supporting the need for a process-based assessment of land/atmosphere Hg exchange.

Basic Aspects of Deep Soil Mixing Technology Control

NASA Astrophysics Data System (ADS)

Egorova, Alexandra A.; Rybak, Jarosław; Stefaniuk, Damian; Zajączkowski, Przemysław

2017-10-01

Improving a soil is a process of increasing its physical/mechanical properties without changing its natural structure. Improvement of soil subbase is reached by means of the knitted materials, or other methods when strong connection between soil particles is established. The method of DSM (Deep Soil Mixing) columns has been invented in Japan in 1970s. The main reason of designing cement-soil columns is to improve properties of local soils (such as strength and stiffness) by mixing them with various cementing materials. Cement and calcium are the most commonly used binders. However new research undertaken worldwide proves that apart from these materials, also gypsum or fly ashes can also be successfully implemented. As the Deep Soil Mixing is still being under development, anticipating mechanical properties of columns in particular soils and the usage of cementing materials in formed columns is very difficult and often inappropriate to predict. That is why a research is carried out in order to find out what binders and mixing technology should be used. The paper presents several remarks on the testing procedures related to quality and capacity control of Deep Soil Mixing columns. Soil improvement methods, their advantages and limitations are briefly described. The authors analyse the suitability of selected testing methods on subsequent stages of design and execution of special foundations works. Chosen examples from engineering practice form the basis for recommendations for the control procedures. Presented case studies concerning testing the on capacity field samples and laboratory procedures on various categories of soil-cement samples were picked from R&D and consulting works offered by Wroclaw University of Science and Technology. Special emphasis is paid to climate conditions which may affect the availability of performing and controlling of DSM techniques in polar zones, with a special regard to sample curing.

Assessing the performance of structure-from-motion photogrammetry and terrestrial lidar 1 at reconstructing soil surface microtopography of naturally vegetated plots

USDA-ARS?s Scientific Manuscript database

Soil microtopography or soil roughness is a property of critical importance in many earth surface processes but is often difficult to measure. Advances in computer vision technologies have made image-based 3D depiction of the soil surface or Structure-from-Motion (SfM) available to many scientists ...

Earth melter and method of disposing of feed materials

DOEpatents

Chapman, Christopher C.

1994-01-01

An apparatus, and method of operating the apparatus, wherein a feed material is converted into a glassified condition for subsequent use or disposal. The apparatus is particularly useful for disposal of hazardous or noxious waste materials which are otherwise either difficult or expensive to dispose of. The apparatus is preferably constructed by excavating a melt zone in a quantity of soil or rock, and lining the melt zone with a back fill material if refractory properties are needed. The feed material is fed into the melt zone and, preferably, combusted to an ash, whereupon the heat of combustion is used to melt the ash to a molten condition. Electrodes may be used to maintain the molten feed material in a molten condition, and to maintain homogeneity of the molten materials.

Earth melter and method of disposing of feed materials

DOEpatents

Chapman, C.C.

1994-10-11

An apparatus, and method of operating the apparatus is described, wherein a feed material is converted into a glassified condition for subsequent use or disposal. The apparatus is particularly useful for disposal of hazardous or noxious waste materials which are otherwise either difficult or expensive to dispose of. The apparatus is preferably constructed by excavating a melt zone in a quantity of soil or rock, and lining the melt zone with a back fill material if refractory properties are needed. The feed material is fed into the melt zone and, preferably, combusted to an ash, whereupon the heat of combustion is used to melt the ash to a molten condition. Electrodes may be used to maintain the molten feed material in a molten condition, and to maintain homogeneity of the molten materials. 3 figs.

Salinity: Electrical conductivity and total dissolved solids

USDA-ARS?s Scientific Manuscript database

The measurement of soil salinity is a quantification of the total salts present in the liquid portion of the soil. Soil salinity is important in agriculture because salinity reduces crop yields by reducing the osmotic potential making it more difficult for the plant to extract water, by causing spe...

Topsoil thickness effects on phosphorus and potassium dynamics on claypan soils

USDA-ARS?s Scientific Manuscript database

Due to variable depth to claypan (DTC) across landscapes, nutrient supply from subsoils, and crop removal, precise P and K fertilizer management on claypan soil fields can be difficult. Therefore, a study was performed to determine if DTC derived from soil apparent electrical conductivity (ECa) coul...

Spectral signature of alpine snow cover from the Landsat Thematic Mapper

NASA Technical Reports Server (NTRS)

Dozier, Jeff

1989-01-01

In rugged terrain, snow in the shadows can appear darker than soil or vegetation in the sunlight, making it difficult to interpret satellite data images of rugged terrains. This paper discusses methods for using Thematic Mapper (TM) and SPOT data for automatic analyses of alpine snow cover. Typical spectral signatures of the Landsat TM are analyzed for a range of snow types, atmospheric profiles, and topographic illumination conditions. A number of TM images of Sierra Nevada are analyzed to distinguish several classes of snow from other surface covers.

A review of combinations of electrokinetic applications.

PubMed

Moghadam, Mohamad Jamali; Moayedi, Hossein; Sadeghi, Masoud Mirmohamad; Hajiannia, Alborz

2016-12-01

Anthropogenic activities contaminate many lands and underground waters with dangerous materials. Although polluted soils occupy small parts of the land, the risk they pose to plants, animals, humans, and groundwater is too high. Remediation technologies have been used for many years in order to mitigate pollution or remove pollutants from soils. However, there are some deficiencies in the remediation in complex site conditions such as low permeability and complex composition of some clays or heterogeneous subsurface conditions. Electrokinetic is an effective method in which electrodes are embedded in polluted soil, usually vertically but in some cases horizontally, and a low direct current voltage gradient is applied between the electrodes. The electric gradient initiates movement of contaminants by electromigration (charged chemical movement), electro-osmosis (movement of fluid), electrolysis (chemical reactions due to the electric field), and diffusion. However, sites that are contaminated with heavy metals or mixed contaminants (e.g. a combination of organic compounds with heavy metals and/or radionuclides) are difficult to remediate. There is no technology that can achieve the best results, but combining electrokinetic with other remediation methods, such as bioremediation and geosynthetics, promises to be the most effective method so far. This review focuses on the factors that affect electrokinetic remediation and the state-of-the-art methods that can be combined with electrokinetic.

A novel experimental procedure to investigate the biodegradation of NAPL under unsaturated conditions

NASA Astrophysics Data System (ADS)

Andre, Laurent; Kedziorek, Monika A. M.; Bourg, Alain C. M.; Haeseler, Frank; Blanchet, Denis

2009-05-01

SummarySoils need to be thoroughly investigated regarding their potential for the natural attenuation of non-aqueous phase liquids (NAPL). Laboratory investigations truly representative of degradation processes in field conditions are difficult to implement for porous media partially saturated with water, NAPL and air. We propose an innovative protocol to investigate degradation processes under steady-state vadose zone conditions. Experiments are carried out in glass columns filled with a sand and, as bacteria source, a soil from a diesel-fuel-polluted site. Water and NAPL ( n-hexadecane diluted in heptamethylnonane (HMN)) are added to the porous medium in a two-step procedure using ceramic membranes placed at the bottom of the column. This procedure results, for appropriate experimental conditions, in a uniform distribution of the two fluids (water and NAPL) throughout the column. In a biodegradation experiment non-biodegradable HMN is used to provide NAPL mass, while keeping biodegradable n-hexadecane small enough to monitor its rapid degradation. Biodegradation is followed as a function of time by measuring oxygen consumption, using a respirometer. Degradative activity is controlled by diffusive transfers in the porous network, of oxygen from the gas phase to the water phase and of n-hexadecane from the NAPL phase to the water phase.

The Effects of Organic Pollutants in Soil on Human Health

NASA Astrophysics Data System (ADS)

Burgess, Lynn

2013-04-01

The soil has always been depository of the organic chemicals produced naturally or anthropogenically. Soil contamination is a serious human and environmental problem. A large body of evidence has shown the risks of adverse health effects with the exposure to contaminated soil due to the large quantities of organic chemicals used in agriculture and urban areas that have a legacy of environmental pollution linked to industrial activities, coal burning, motor vehicle emissions, waste incineration and waste dumping. In agricultural areas, because of the effort to provide adequate quantities of agricultural products, farmers have been using an increasing amount of organic chemicals, but the resulting pollution has enormous potential for environmental damage. The types of organic pollutants commonly found in soils are polychlorinated biphenyls, polybrominated biphenyls, polychlorinated dibenzofurans, polycyclic aromatic hydrocarbons, organophosphorus and carbamate insecticides, herbicides and organic fuels, especially gasoline and diesel. Another source of soil pollution is the complex mixture of organic chemicals, metals and microorganisms in the effluent from septic systems, animal wastes and other sources of biowaste. The soils of the world are a vast mixture of chemicals and although conditions are such that an individual is rarely exposed to a single compound, the great majority of people are exposed to a vast chemical mixture of organics, their metabolites, and other compounds at low concentrations Human exposure to organic pollutants in the soil is an area of toxicology that is very difficult to study due to the low concentration of the pollutants. The toxicological studies of single organic pollutants found in soils are limited and research on the metabolites and of chemical mixtures is very limited. The majority of toxicological studies are conducted at relatively high doses and for short periods of exposure. This makes the application of this data to exposure from soil very difficult, with the exposure from soil usually being chronic and at very low concentrations. The vastness of the soil has led to the dilution of these pollutants and most of the pollutants remain on or near the surface of the soil unless they have moved by the action of water, organisms, or mechanical mixing. This dilution has reduced the toxicity of these pollutants but the unknown factor is the action of the soil, its chemistry, and the combined action of all the microorganisms, plants, and invertebrates that live in the soil. This biological action combined with the influences of the soil components has the potential of creating new metabolites and chemicals. Toxicologists needs expand their studies to include the persistent organic pollutants and the organic pollutants that can bioaccumulate in organisms. We do not know if the addition of organics chemicals to the soil is creating very toxic xenobiotics and at very low concentrations but with important health effects to humans and other organisms. These unknown compounds could be accumulating in plants that we use for food or as forage for our livestock, then bioaccumulating in the livestock and then on into us.

Delineation of major soil associations using ERTS-1 imagery

NASA Technical Reports Server (NTRS)

Parks, W. L.; Bodenheimer, R. E.

1973-01-01

The delineation of a major soil association in the loess region of Obion County has been accomplished using ERTS-1 imagery. Channel 7 provides the clearest differentiation. The separation of other smaller soil associations in an intensive row crop agricultural area is somewhat more difficult. Soil differentiation has been accomplished visually as well as electronically using a scanning microdensitometer. Lower altitude aircraft imagery permits a more refined soil association identification and where imagery is of sufficient scale, even individual soils may be identified.

Soil Parameter Mapping and Ad Hoc Power Analysis to Increase Blocking Efficiency Prior to Establishing a Long-Term Field Experiment

PubMed Central

Collins, Doug; Benedict, Chris; Bary, Andy; Cogger, Craig

2015-01-01

The spatial heterogeneity of soil and weed populations poses a challenge to researchers. Unlike aboveground variability, below-ground variability is more difficult to discern without a strategic soil sampling pattern. While blocking is commonly used to control environmental variation, this strategy is rarely informed by data about current soil conditions. Fifty georeferenced sites were located in a 0.65 ha area prior to establishing a long-term field experiment. Soil organic matter (OM) and weed seed bank populations were analyzed at each site and the spatial structure was modeled with semivariograms and interpolated with kriging to map the surface. These maps were used to formulate three strategic blocking patterns and the efficiency of each pattern was compared to a completely randomized design and a west to east model not informed by soil variability. Compared to OM, weeds were more variable across the landscape and had a shorter range of autocorrelation, and models to increase blocking efficiency resulted in less increase in power. Weeds and OM were not correlated, so no model examined improved power equally for both parameters. Compared to the west to east blocking pattern, the final blocking pattern chosen resulted in a 7-fold increase in power for OM and a 36% increase in power for weeds. PMID:26247056

Use of pyrolysis molecular beam mass spectrometry (py-MBMS) to characterize forest soil carbon: method and preliminary results

Treesearch

K.A. Magrini; R.J. Evans; C.M. Hoover; C.C. Elam; M.F. Davis

2002-01-01

The components of soil organic matter (SOM) and their degradation dynamics in forest soils are difficult to study and thus poorly understood,due to time-consuming sample collection, preparation, and difficulty of analyzing and identifying major components. As a result, changes in soil organic matter chemical composition as a function of age, forest type, or disturbance...

Multi-scale sensitivity analysis of pile installation using DEM

NASA Astrophysics Data System (ADS)

Esposito, Ricardo Gurevitz; Velloso, Raquel Quadros; , Eurípedes do Amaral Vargas, Jr.; Danziger, Bernadete Ragoni

2017-12-01

The disturbances experienced by the soil due to the pile installation and dynamic soil-structure interaction still present major challenges to foundation engineers. These phenomena exhibit complex behaviors, difficult to measure in physical tests and to reproduce in numerical models. Due to the simplified approach used by the discrete element method (DEM) to simulate large deformations and nonlinear stress-dilatancy behavior of granular soils, the DEM consists of an excellent tool to investigate these processes. This study presents a sensitivity analysis of the effects of introducing a single pile using the PFC2D software developed by Itasca Co. The different scales investigated in these simulations include point and shaft resistance, alterations in porosity and stress fields and particles displacement. Several simulations were conducted in order to investigate the effects of different numerical approaches showing indications that the method of installation and particle rotation could influence greatly in the conditions around the numerical pile. Minor effects were also noted due to change in penetration velocity and pile-soil friction. The difference in behavior of a moving and a stationary pile shows good qualitative agreement with previous experimental results indicating the necessity of realizing a force equilibrium process prior to any load-test to be simulated.

Multi-scale sensitivity analysis of pile installation using DEM

NASA Astrophysics Data System (ADS)

Esposito, Ricardo Gurevitz; Velloso, Raquel Quadros; , Eurípedes do Amaral Vargas, Jr.; Danziger, Bernadete Ragoni

2018-07-01

The disturbances experienced by the soil due to the pile installation and dynamic soil-structure interaction still present major challenges to foundation engineers. These phenomena exhibit complex behaviors, difficult to measure in physical tests and to reproduce in numerical models. Due to the simplified approach used by the discrete element method (DEM) to simulate large deformations and nonlinear stress-dilatancy behavior of granular soils, the DEM consists of an excellent tool to investigate these processes. This study presents a sensitivity analysis of the effects of introducing a single pile using the PFC2D software developed by Itasca Co. The different scales investigated in these simulations include point and shaft resistance, alterations in porosity and stress fields and particles displacement. Several simulations were conducted in order to investigate the effects of different numerical approaches showing indications that the method of installation and particle rotation could influence greatly in the conditions around the numerical pile. Minor effects were also noted due to change in penetration velocity and pile-soil friction. The difference in behavior of a moving and a stationary pile shows good qualitative agreement with previous experimental results indicating the necessity of realizing a force equilibrium process prior to any load-test to be simulated.

The persistent environmental relevance of soil phosphorus sorption saturation

USDA-ARS?s Scientific Manuscript database

Controlling phosphorus (P) loss from agricultural soils remains a priority pollution concern in much of the world. Dissolved forms of P loss are amongst the most difficult to manage. The concept of soil P sorption saturation emerged from the Netherlands in the 1990s and has broad appeal as an enviro...

USEPA'S RESEARCH PROGRAM ON REMEDIATION AND CONTAINMENT OF ARSENIC AND MERCURY IN SOILS, INDUSTRIAL WASTES, AND GROUNDWATER

EPA Science Inventory

In the U.S. and around the world, mercury and arsenic contaminated soils, industrial wastes, and groundwater are difficult to effectively and cheaply remediate and contain. Mercury is a serious health concern and has been identified as a contaminant in the air, soil, sediment, su...

Factors influencing the extraction of pharmaceuticals from sewage sludge and soil: an experimental design approach.

PubMed

Ferhi, Sabrina; Bourdat-Deschamps, Marjolaine; Daudin, Jean-Jacques; Houot, Sabine; Nélieu, Sylvie

2016-09-01

Pharmaceuticals can enter the environment when organic waste products are recycled on agricultural soils. The extraction of pharmaceuticals is a challenging step in their analysis. The very different extraction conditions proposed in the literature make the choice of the right method for multi-residue analysis difficult. This study aimed at evaluating, with experimental design methodology, the influence of the nature, pH and composition of the extraction medium on the extraction recovery of 14 pharmaceuticals, including 8 antibiotics, from soil and sewage sludge. Preliminary experimental designs showed that acetonitrile and citrate-phosphate buffer were the best extractants. Then, a response surface design demonstrated that many cross-product and squared terms had significant effects, explaining the shapes of the response surfaces. It also allowed optimising the pharmaceutical recoveries in soil and sludge. The optimal conditions were interpreted considering the ionisation states of the compounds, their solubility in the extraction medium and their interactions with the solid matrix. To perform the analysis, a compromise was made for each matrix. After a QuEChERS purification, the samples were analysed by online SPE-UHPLC-MS-MS. Both methods were simple and economical. They were validated with the accuracy profile methodology for soil and sludge and characterised for another type of soil, digested sludge and composted sludge. Trueness globally ranged between 80 and 120 % recovery, and inter- and intra-day precisions were globally below 20 % relative standard deviation. Various pharmaceuticals were present in environmental samples, with concentration levels ranging from a few micrograms per kilogramme up to thousands of micrograms per kilogramme. Graphical abstract Influence of the extraction medium on the extraction recovery of 14 pharmaceuticals. Influence of the ionisation state, the solubility and the interactions of pharmaceuticals with solid matrix. Analysis of different soils and organic waste products.

Guiding Empirical and Theoretical Explorations of Organic Matter Decay By Synthesizing Temperature Responses of Enzyme Kinetics, Microbes, and Isotope Fluxes

NASA Astrophysics Data System (ADS)

Billings, S. A.; Ballantyne, F.; Lehmeier, C.; Min, K.

2014-12-01

Soil organic matter (SOM) transformation rates generally increase with temperature, but whether this is realized depends on soil-specific features. To develop predictive models applicable to all soils, we must understand two key, ubiquitous features of SOM transformation: the temperature sensitivity of myriad enzyme-substrate combinations and temperature responses of microbial physiology and metabolism, in isolation from soil-specific conditions. Predicting temperature responses of production of CO2 vs. biomass is also difficult due to soil-specific features: we cannot know the identity of active microbes nor the substrates they employ. We highlight how recent empirical advances describing SOM decay can help develop theoretical tools relevant across diverse spatial and temporal scales. At a molecular level, temperature effects on purified enzyme kinetics reveal distinct temperature sensitivities of decay of diverse SOM substrates. Such data help quantify the influence of microbial adaptations and edaphic conditions on decay, have permitted computation of the relative availability of carbon (C) and nitrogen (N) liberated upon decay, and can be used with recent theoretical advances to predict changes in mass specific respiration rates as microbes maintain biomass C:N with changing temperature. Enhancing system complexity, we can subject microbes to temperature changes while controlling growth rate and without altering substrate availability or identity of the active population, permitting calculation of variables typically inferred in soils: microbial C use efficiency (CUE) and isotopic discrimination during C transformations. Quantified declines in CUE with rising temperature are critical for constraining model CUE estimates, and known changes in δ13C of respired CO2 with temperature is useful for interpreting δ13C-CO2 at diverse scales. We suggest empirical studies important for advancing knowledge of how microbes respond to temperature, and ideas for theoretical work to enhance the relevance of such work to the world's soils.

Aqueous processes at Gusev crater inferred from physical properties of rocks and soils along the Spirit traverse

USGS Publications Warehouse

Cabrol, N.A.; Farmer, J.D.; Grin, E.A.; Ritcher, L.; Soderblom, L.; Li, R.; Herkenhoff, K.; Landis, G.A.; Arvidson, R. E.

2006-01-01

Gusev crater was selected as the landing site for Spirit on the basis of morphological evidence of long-lasting water activity, including possibly fluvial and lacustrine episodes. From the Columbia Memorial Station to the Columbia Hills, Spirit's traverse provides a journey back in time, from relatively recent volcanic plains showing little evidence for aqueous processes up to the older hills, where rock and soil composition are drastically different. For the first 156 sols, the only evidence of water action was weathering rinds, vein fillings, and soil crust cementation by salts. The trenches of Sols 112-145 marked the first significant findings of increased concentrations of sulfur and magnesium varying in parallel, suggesting that they be paired as magnesium-sulfate. Spirit's arrival at West Spur coincided with a shift in rock and soil composition with observations hinting at substantial amounts of water in Gusev's past. We used the Microscopic Imager data up to Sol 431 to analyze rock and soil properties and infer plausible types and magnitude of aqueous processes through time. We show the role played early by topography and structure. The morphology, texture, and deep alteration shown by the rocks in West Spur and the Columbia Hills Formation (CHF) suggest conditions that are not met in present-day Mars and required a wetter environment, which could have included transport of sulfur, chlorine, and bromine in water, vapor in volcanic gases, hydrothermal circulation, or saturation in a briny fluid containing the same elements. Changing conditions that might have affected flow circulation are suggested by different textural and morphological characteristics between the rocks in the CHF and those of the plains, with higher porosity proxy, higher void ratio, and higher water storage potential in the CHF. Soils were used to assess aqueous processes and water pathways in the top layers of modern soils. We conclude that infiltration might have become more difficult with time. Copyright 2006 by the American Geophysical Union.

Issues in the inverse modeling of a soil infiltration process

NASA Astrophysics Data System (ADS)

Kuraz, Michal; Jacka, Lukas; Leps, Matej

2017-04-01

This contribution addresses issues in evaluation of the soil hydraulic parameters (SHP) from the Richards equation based inverse model. The inverse model was representing single ring infiltration experiment on mountainous podzolic soil profile, and was searching for the SHP parameters of the top soil layer. Since the thickness of the top soil layer is often much lower than the depth required to embed the single ring or Guelph permeameter device, the SHPs for the top soil layer are very difficult to measure directly. The SHPs for the top soil layer were therefore identified here by inverse modeling of the single ring infiltration process, where, especially, the initial unsteady part of the experiment is expected to provide very useful data for evaluating the retention curve parameters (excluding the residual water content) and the saturated hydraulic conductivity. The main issue, which is addressed in this contribution, is the uniqueness of the Richards equation inverse model. We tried to answer the question whether is it possible to characterize the unsteady infiltration experiment with a unique set of SHPs values, and whether are all SHP parameters vulnerable with the non-uniqueness. Which is an important issue, since we could further conclude whether the popular gradient methods are appropriate here. Further the issues in assigning the initial and boundary condition setup, the influence of spatial and temporal discretization on the values of the identified SHPs, and the convergence issues with the Richards equation nonlinear operator during automatic calibration procedure are also covered here.

Effect of climate on the storage and turnover of carbon in soils

NASA Technical Reports Server (NTRS)

Trumbore, Susan; Chadwick, Oliver; Amundson, Ronald; Brasher, Benny

1994-01-01

Climate is, in many instances, the dominant variable controlling the storage of carbon in soils. It has proven difficult, however, to determine how soil properties influenced by climate, such as soil temperature and soil moisture, actually operate to determine the rates of accumulation and decomposition of soil organic matter. Our approach has been to apply a relatively new tool, the comparison of C-14 in soil organic matter from pre- and post-bomb soils, to quantify carbon turnover rates along climosequences. This report details the progress made toward this end by work under this contract.

Nature and Dynamics of Carbon Accrued in a Forest Soil During Five Years of Atmospheric CO2 Enrichment

NASA Astrophysics Data System (ADS)

Jastrow, J. D.; O'Brien, S. L.; Dria, K. J.; Moran, K. K.; Filley, T. R.; Boutton, T. W.

2004-12-01

The potential for enhanced soil C storage to partially offset rising atmospheric CO2 concentrations is being evaluated by long-term field CO2 enrichment experiments. Although plant productivity is often stimulated in such experiments, the fate of increased detrital inputs to soil has yet to be definitively resolved, in part because detecting changes in soil C against the relatively large, spatially heterogeneous pool of existing soil organic matter has proven difficult. Even when significant changes in whole soil C are evident, predictions of the potential for long-term sequestration will require detailed studies of C dynamics and stability in functionally meaningful soil organic matter pools. In our studies at the free-air CO2 enrichment (FACE) experiment on a sweetgum (Liquidambar styraciflua L.) forest plantation in Oak Ridge, Tennessee, we are using (1) repeated sampling over time, (2) the isotopic tracer provided by the highly depleted 13C signature of the CO2 source used for fumigation, and (3) physical and chemical fractionation procedures to determine the fate and dynamics of FACE-derived C inputs to soil organic matter. After five years of CO2 enrichment, soil C accumulated at a linear rate in both unprotected and aggregate-protected pools, suggesting that additional C inputs were being processed and cycled in much the same manner as under ambient conditions. However, selective analysis of the biopolymer composition (lignin, suberin, and cutin) and oxidation state of the organic matter in physically and chemically isolated soil fractions will be used to assess the source, nature and potential stability of the C accrued in protected and unprotected pools.

Evaluation of a Soil Moisture Data Assimilation System Over West Africa

NASA Astrophysics Data System (ADS)

Bolten, J. D.; Crow, W.; Zhan, X.; Jackson, T.; Reynolds, C.

2009-05-01

A crucial requirement of global crop yield forecasts by the U.S. Department of Agriculture (USDA) International Production Assessment Division (IPAD) is the regional characterization of surface and sub-surface soil moisture. However, due to the spatial heterogeneity and dynamic nature of precipitation events and resulting soil moisture, accurate estimation of regional land surface-atmosphere interactions based sparse ground measurements is difficult. IPAD estimates global soil moisture using daily estimates of minimum and maximum temperature and precipitation applied to a modified Palmer two-layer soil moisture model which calculates the daily amount of soil moisture withdrawn by evapotranspiration and replenished by precipitation. We attempt to improve upon the existing system by applying an Ensemble Kalman filter (EnKF) data assimilation system to integrate surface soil moisture retrievals from the NASA Advanced Microwave Scanning Radiometer (AMSR-E) into the USDA soil moisture model. This work aims at evaluating the utility of merging satellite-retrieved soil moisture estimates with the IPAD two-layer soil moisture model used within the DBMS. We present a quantitative analysis of the assimilated soil moisture product over West Africa (9°N- 20°N; 20°W-20°E). This region contains many key agricultural areas and has a high agro- meteorological gradient from desert and semi-arid vegetation in the North, to grassland, trees and crops in the South, thus providing an ideal location for evaluating the assimilated soil moisture product over multiple land cover types and conditions. A data denial experimental approach is utilized to isolate the added utility of integrating remotely-sensed soil moisture by comparing assimilated soil moisture results obtained using (relatively) low-quality precipitation products obtained from real-time satellite imagery to baseline model runs forced with higher quality rainfall. An analysis of root-zone anomalies for each model simulation suggests that the assimilation of AMSR-E surface soil moisture retrievals can add significant value to USDA root-zone predictions derived from real-time satellite precipitation products.

Continental-scale patterns in soil geochemistry and mineralogy: results from two transects across the United States and Canada

USGS Publications Warehouse

Woodruff, L.G.; Cannon, W.F.; Eberl, D.D.; Smith, D.B.; Kilburn, J.E.; Horton, J.D.; Garrett, R.G.; Klassen, R.A.

2009-01-01

In 2004, the US Geological Survey (USGS) and the Geological Survey of Canada (GSC) initiated a pilot study that involved collection of more than 1500 soil samples from 221 sites along two continental transects across Canada and the United States. The pilot study was designed to test and refine protocols for a soil geochemical survey of North America. The two transects crossed a wide array of soil parent materials, soil ages, climatic conditions, landforms, land covers and land uses. Sample sites were selected randomly at approximately 40-km intervals from a population defined as all soils of the continent. At each site, soils representing 0 to 5 cm depth, and the O, A, and C horizons, if present, were collected and analyzed for their near-total content of over 40 major and trace elements. Soils from 0–5 cm depth were also collected for analysis of organic compounds. Results from the transects confirm that soil samples collected at a 40-km spacing reveal coherent, continental- to subcontinental-scale geochemical and mineralogical patterns that can be correlated to aspects of underlying soil parent material, soil age and climate influence. The geochemical data also demonstrate that at the continental-scale the dominance of any of these major factors that control soil geochemistry can change across the landscape. Along both transects, soil mineralogy and geochemistry change abruptly with changes in soil parent materials. However, the chemical influence of a soil’s parent material can be obscured by changing climatic conditions. For the transects, increasing precipitation from west to east and increasing temperature from north to south affect both soil mineralogy and geochemistry because of climate effects on soil weathering and leaching, and plant productivity. Regional anomalous metal concentrations can be linked to natural variations in soil parent materials, such as high Ni and Cr in soils developed on ultramafic rocks in California or high P in soils formed on weathered Ordovician limestones in central Kentucky. On local scales, anomalous metal concentrations recognized in soil profiles, such as high P in soils from animal confinement sites, are consistent with local anthropogenic disturbances. At a larger scale, the distribution of Hg across the west to east transect demonstrates that it can be difficult to distinguish between natural or anthropogenic contributions and that many factors can contribute to an element’s spatial distribution. Only three samples in a subset of seventy-three 0–5 cm depth soil samples from the north to south transect had organochlorine pesticides values above the method detection limit, apparently related to historic usage of the pesticides DDT and dieldrin.

Port of Seattle breaks the brownfield gridlock

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

Rapaport, D.

Initiatives in brownfields restoration--in which abandoned, contaminated industrial and commercial sites can be revitalized and returned to productive use--many times have been gridlocked by a core problem: how to achieve protective cleanup levels without bankrupting the cost bearers. Barriers to brownfields restoration include: remediation standards, set by regulatory agencies, that are difficult to achieve at complex sites; technical barriers that make it difficult to restore sites to pristine conditions; and liability and cost issues that discourage investors and lenders from properties struggling under an unfinished regulatory process. Each barrier affects the others, creating a maze that is easy to entermore » but difficult to escape. In many cases, money, time and expertise are squandered, and feelings of anger and frustration are vented. Fear of gridlock halts many brownfields projects before they begin. Previous site investigations conducted by property owners revealed that spills, leaks, drips and onsite waste disposal of organic and inorganic preservatives used in wood-treatment processes had contaminated the soil and groundwater. The most toxic contaminants were a group of carcinogenic polycyclic aromatic hydrocarbons, such as benzo(a)pyrene, pentachlorophenol and arsenic.« less

Earth melter

DOEpatents

Chapman, Christopher C.

1995-01-01

An apparatus, and method of operating the apparatus, wherein a feed material is converted into a glassified condition for subsequent use or disposal. The apparatus is particularly useful for disposal of hazardous or noxious waste materials which are otherwise either difficult or expensive to dispose of. The apparatus is preferably constructed either by excavating a melt zone in a quantity of soil or rock, or by constructing a melt zone in an apparatus above grade and lining the melt zone with a back fill material if refractory properties are needed. The feed material is fed into the melt zone and, preferably, combusted to an ash, whereupon the heat of combustion is used to melt the ash to a molten condition. Electrodes may be used to maintain the molten feed material in a molten condition, and to maintain homogeneity of the molten materials.

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.

Modeling soil erosion and transport on forest landscape

Treesearch

Ge Sun; Steven G McNulty

1998-01-01

Century-long studies on the impacts of forest management in North America suggest sediment can cause major reduction on stream water quality. Soil erosion patterns in forest watersheds are patchy and heterogeneous. Therefore, patterns of soil erosion are difficult to model and predict. The objective of this study is to develop a user friendly management tool for land...

Soil carbon sequestration and forest management: challenges and opportunities

Treesearch

Coeli M. Hoover

2003-01-01

The subject of the effects of forest management activities on soil carbon is a difficult one to address, but ongoing discussions of carbon sequestration as an emissions offset and the emergence of carbon-credit-trading systems necessitate that we broaden and deepen our understanding of the response of forest-soil carbon pools to forest management. There have been...

Mapping forest soil organic matter on New Jersey's coastal plain

Treesearch

Brian J. Clough; Edwin J. Green; Richard B. Lathrop

2012-01-01

Managing forest soil organic matter (SOM) stocks is a vital strategy for reducing the impact of anthropogenic carbon dioxide emissions. However, the SOM pool is highly variable, and developing accurate estimates to guide management decisions has remained a difficult task. We present the results of a spatial model designed to map soil organic matter for all forested...

Soil Texture Estimates: A Tool to Compare Texture-by-Feel and Lab Data

ERIC Educational Resources Information Center

Franzmeier, D.P.; Owens, P.R.

2008-01-01

Soil texture is a fundamental soil property that impacts agricultural and engineering land-use. Comparing texture estimates-by-feel to laboratory-known values to calibrate fingers is a common practice. As educators, it is difficult to assess this field skill consistently and fairly. The instructor may give full credit for the correct texture class…

Numerical evaluation of a sensible heat balance method to determine rates of soil freezing and thawing

USDA-ARS?s Scientific Manuscript database

In-situ determination of ice formation and thawing in soils is difficult despite its importance for many environmental processes. A sensible heat balance (SHB) method using a sequence of heat pulse probes has been shown to accurately measure water evaporation in subsurface soil, and it has the poten...

The role of soil weathering and hydrology in regulating chemical fluxes from catchments (Invited)

NASA Astrophysics Data System (ADS)

Maher, K.; Chamberlain, C. P.

2010-12-01

Catchment-scale chemical fluxes have been linked to a number of different parameters that describe the conditions at the Earth’s surface, including runoff, temperature, rock type, vegetation, and the rate of tectonic uplift. However, many of the relationships relating chemical denudation to surface processes and conditions, while based on established theoretical principles, are largely empirical and derived solely from modern observations. Thus, an enhanced mechanistic basis for linking global solute fluxes to both surface processes and climate may improve our confidence in extrapolating modern solute fluxes to past and future conditions. One approach is to link observations from detailed soil-based studies with catchment-scale properties. For example, a number of recent studies of chemical weathering at the soil-profile scale have reinforced the importance of hydrologic processes in controlling chemical weathering rates. An analysis of data from granitic soils shows that weathering rates decrease with increasing fluid residence times and decreasing flow rates—over moderate fluid residence times, from 5 days to 10 years, transport-controlled weathering explains the orders of magnitude variation in weathering rates to a better extent than soil age. However, the importance of transport-controlled weathering is difficult to discern at the catchment scale because of the range of flow rates and fluid residence times captured by a single discharge or solute flux measurement. To assess the importance of transport-controlled weathering on catchment scale chemical fluxes, we present a model that links the chemical flux to the extent of reaction between the soil waters and the solids, or the fluid residence time. Different approaches for describing the distribution of fluid residence times within a catchment are then compared with the observed Si fluxes for a limited number of catchments. This model predicts high solute fluxes in regions with high run-off, relief, and long flow paths suggesting that the particular hydrologic setting of a landscape will be the underlying control on the chemical fluxes. As such, we reinterpret the large chemical fluxes that are observed in active mountain belts, like the Himalaya, to be primarily controlled by the long reactive flow paths created by the steep terrain coupled with high amounts of precipitation.

Crop diversity effects on soil health

USDA-ARS?s Scientific Manuscript database

Concurrent demands for abundant, healthy food, thriving rural economies, and an unpolluted physical environment represents a significant agricultural challenge in the 21st century. Trends in human population growth and changing weather patterns will make this challenge exceedingly difficult. Soil ...

Multimodel Simulation of Water Flow: Uncertainty Analysis

USDA-ARS?s Scientific Manuscript database

Simulations of soil water flow require measurements of soil hydraulic properties which are particularly difficult at the field scale. Laboratory measurements provide hydraulic properties at scales finer than the field scale, whereas pedotransfer functions (PTFs) integrate information on hydraulic pr...

Searching for plant root traits to improve soil cohesion and resist soil erosion

NASA Astrophysics Data System (ADS)

De Baets, Sarah; Smyth, Kevin; Denbigh, Tom; Weldon, Laura; Higgins, Ben; Matyjaszkiewicz, Antoni; Meersmans, Jeroen; Chenchiah, Isaac; Liverpool, Tannie; Quine, Tim; Grierson, Claire

2017-04-01

Soil erosion poses a serious threat to future food and environmental security. Soil erosion protection measures are therefore of great importance for soil conservation and food security. Plant roots have proven to be very effective in stabilizing the soil and protecting the soil against erosion. However, no clear insights are yet obtained into the root traits that are responsible for root-soil cohesion. This is important in order to better select the best species for soil protection. Research using Arabidopsis mutants has made great progress towards explaining how root systems are generated by growth, branching, and responses to gravity, producing mutants that affect root traits. In this study, the performance of selected Arabidopsis mutants is analyzed in three root-soil cohesion assays. Measurements of detachment, uprooting force and soil detachment are here combined with the microscopic analysis of root properties, such as the presence, length and density of root hairs in this case. We found that Arabidopsis seedlings with root hairs (wild type, wer myb23, rsl4) were more difficult to detach from gel media than hairless (cpc try) or short haired (rsl4, rhd2) roots. Hairy roots (wild type, wer myb23) on mature, non-reproductive rosettes were more difficult to uproot from compost or clay soil than hairless roots (cpc try). At high root densities, erosion rates from soils with hairless roots (cpc try) were as much as 10 times those seen from soils occupied by roots with hairs (wer myb23, wild type). We find therefore root hairs play a significant role in root-soil cohesion and in minimizing erosion. This framework and associated suite of experimental assays demonstrates its ability to measure the effect of any root phenotype on the effectiveness of plant roots in binding substrates and reducing erosion.

Soil-release behaviour of polyester fabrics after chemical modification with polyethylene glycol

NASA Astrophysics Data System (ADS)

Miranda, T. M. R.; Santos, J.; Soares, G. M. B.

2017-10-01

The fibres cleanability depends, among other characteristics, on their hydrophilicity. Hydrophilic fibres are easy-wash materials but hydrophobic fibres are difficult to clean due to their higher water-repellent surfaces. This type of surfaces, like polyester (PET), produce an accumulation of electrostatic charges, which favors adsorption and retention of dirt. Thus, the polyester soil-release properties can be increased by finishing processes that improve fiber hydrophilicity. In present study, PET fabric modification was described by using poly(ethylene glycol) (PEG) and N,N´-dimethylol-4,5-dihydroxyethylene urea (DMDHEU) chemically modified resin. Briefly, the modification process was carried out in two steps, one to hydrolyse the polyester and create hydroxyl and carboxylic acid groups on the surface and other to crosslink the PEG chains. The resulting materials were characterized by contact angle, DSC and FTIR-ATR methods. Additionally, the soil release behavior and the mechanical properties of modified PET were evaluated. For the best process conditions, the treated PET presented 0° contact angle, grade 5 stain release and acceptable mechanical performance.

Plant root proliferation in nitrogen-rich patches confers competitive advantage

PubMed Central

Robinson, D.; Hodge, A.; Griffiths, B. S.; Fitter, A. H.

1999-01-01

Plants respond strongly to environmental heterogeneity, particularly below ground, where spectacular root proliferations in nutrient-rich patches may occur. Such 'foraging' responses apparently maximize nutrient uptake and are now prominent in plant ecological theory. Proliferations in nitrogen-rich patches are difficult to explain adaptively, however. The high mobility of soil nitrate should limit the contribution of proliferation to N capture. Many experiments on isolated plants show only a weak relation between proliferation and N uptake. We show that N capture is associated strongly with proliferation during interspecific competition for finite, locally available, mixed N sources, precisely the conditions under which N becomes available to plants on generally infertile soils. This explains why N-induced root proliferation is an important resource-capture mechanism in N-limited plant communities and suggests that increasing proliferation by crop breeding or genetic manipulation will have a limited impact on N capture by well-fertilized monocultures.

The application of ERTS imagery to the FAO/Unesco soil map of the world

NASA Technical Reports Server (NTRS)

Dudal, R. J.; Pecrot, A. J. (Principal Investigator)

1977-01-01

The author has identified the following significant results. It was concluded that direct identification and mapping of the various soil degradation forms and intensities from the color composite imager was generally difficult, if not impossible. The imagery, however, provided valuable information on some main environmental criteria which can be used in connection other available field data to assess actual soil degradation and estimate soil degradation hazards.

Influence of redox fluctuations and rainfall on pedogenic iron alteration and soil magnetic properties (Invited)

NASA Astrophysics Data System (ADS)

Thompson, A.; Rancourt, D.; Chadwick, O.; Chorover, J. D.

2009-12-01

Soil iron mineral composition emerges from a dynamic interplay between processes causing selective mineral addition/removal (both physically and chemically-driven) and processes affecting in situ mineral transformation. Discerning the influence of these pedogenic processes in a temporally integrated manner is fundamentally relevant to many biogeochemical questions. Among them is to what extent the Fe-mineral system can be used to constrain paleo-interpretations of oceanic sediments and geological deposits. Here we describe results from field and laboratory experiments designed to explore the effects of variable redox conditions on soil iron mineral transformation. Our experimental systems include: (1) a climate gradient of basaltic soils from the island of Maui, HI (MCG) with a documented decrease in Eh. and (2) laboratory incubations where we subjected soil slurries to a series of bacterially-driven reduction-oxidation cycles. Our prior work in these systems examining the iron isotopic and mineral composition will be combined with in-progress analysis of magnetic susceptibility. Current results indicate that across the field gradient (MCG) we find average increases of 0.56‰±0.09‰ δ56Fe for the surface and subsurface soils that correlate very well (R2=0.88) with 57Fe Mössbauer-determined Fe-oxyhydroxide fraction. Such a correlation is difficult to explain on the basis of strict parameter co-variation with rainfall, and suggests isotopic and mineral composition may be coupled through in situ mineral transformation processes in these soils. In our soil slurry incubation experiments we reported previously that repeated redox oscillations generate a cumulative increase in Fe mineral crystallinity. Integration of these results with magnetic susceptibility measurements will provide the context for discussing how dynamic redox processes alter soil magnetic properties most often drawn on for paleoclimate interpretations.

Growing up green on serpentine soils: Biogeochemistry of serpentine vegetation in the Central Coast Range of California

USGS Publications Warehouse

Oze, C.; Skinner, C.; Schroth, A.W.; Coleman, R.G.

2008-01-01

Serpentine soils derived from the weathering of ultramafic rocks and their metamorphic derivatives (serpentinites) are chemically prohibitive for vegetative growth. Evaluating how serpentine vegetation is able to persist under these chemical conditions is difficult to ascertain due to the numerous factors (climate, relief, time, water availability, etc.) controlling and affecting plant growth. Here, the uptake, incorporation, and distribution of a wide variety of elements into the biomass of serpentine vegetation has been investigated relative to vegetation growing on an adjacent chert-derived soil. Soil pH, electrical conductivity, organic C, total N, soil extractable elements, total soil elemental compositions and plant digestions in conjunction with spider diagrams are utilized to determine the chemical relationships of these soil and plant systems. Plant available Mg and Ca in serpentine soils exceed values assessed in chert soils. Magnesium is nearly 3 times more abundant than Ca in the serpentine soils; however, the serpentine soils are not Ca deficient with Ca concentrations as high as 2235 mg kg-1. Calcium to Mg ratios (Ca:Mg) in both serpentine and chert vegetation are greater than one in both below and above ground tissues. Soil and plant chemistry analyses support that Ca is not a limiting factor for plant growth and that serpentine vegetation is actively moderating Mg uptake as well as tolerating elevated concentrations of bioavailable Mg. Additionally, results demonstrate that serpentine vegetation suppresses the uptake of Fe, Cr, Ni, Mn and Co into its biomass. The suppressed uptake of these metals mainly occurs in the plants' roots as evident by the comparatively lower metal concentrations present in above ground tissues (twigs, leaves and shoots). This research supports earlier studies that have suggested that ion uptake discrimination and ion suppression in the roots are major mechanisms for serpentine vegetation to tolerate the chemistry of serpentine soils. ?? 2008 Elsevier Ltd.

The past, present, and future of soils and human health studies

NASA Astrophysics Data System (ADS)

Brevik, E. C.; Sauer, T. J.

2015-01-01

The idea that human health is tied to the soil is not a new one. As far back as circa 1400 BC the Bible depicts Moses as understanding that fertile soil was essential to the well-being of his people. In 400 BC the Greek philosopher Hippocrates provided a list of things that should be considered in a proper medical evaluation, including the properties of the local ground. By the late 1700s and early 1800s, American farmers had recognized that soil properties had some connection to human health. In the modern world, we recognize that soils have a distinct influence on human health. We recognize that soils influence (1) food availability and quality (food security), (2) human contact with various chemicals, and (3) human contact with various pathogens. Soils and human health studies include investigations into nutrient supply through the food chain and routes of exposure to chemicals and pathogens. However, making strong, scientific connections between soils and human health can be difficult. There are multiple variables to consider in the soil environment, meaning traditional scientific studies that seek to isolate and manipulate a single variable often do not provide meaningful data. The complete study of soils and human health also involves many different specialties such as soil scientists, toxicologists, medical professionals, anthropologists, etc. These groups do not traditionally work together on research projects, and do not always effectively communicate with one another. Climate change and how it will affect the soil environment/ecosystem going into the future is another variable affecting the relationship between soils and health. Future successes in soils and human health research will require effectively addressing difficult issues such as these.

Quick, Easy Method to Show Living Soil Organisms to High School or Beginning-Level College Students

ERIC Educational Resources Information Center

Loynachan, Thomas E.

2006-01-01

The living component of soil is difficult for students to learn about and understand because students have difficulty relating to things they cannot see (beyond sight, beyond mind). Line drawings from textbooks help explain conceptual relationships but do little to stimulate an active interest in the living component of soil. Alternatively,…

EnKF with closed-eye period - bridging intermittent model structural errors in soil hydrology

NASA Astrophysics Data System (ADS)

Bauser, Hannes H.; Jaumann, Stefan; Berg, Daniel; Roth, Kurt

2017-04-01

The representation of soil water movement exposes uncertainties in all model components, namely dynamics, forcing, subscale physics and the state itself. Especially model structural errors in the description of the dynamics are difficult to represent and can lead to an inconsistent estimation of the other components. We address the challenge of a consistent aggregation of information for a manageable specific hydraulic situation: a 1D soil profile with TDR-measured water contents during a time period of less than 2 months. We assess the uncertainties for this situation and detect initial condition, soil hydraulic parameters, small-scale heterogeneity, upper boundary condition, and (during rain events) the local equilibrium assumption by the Richards equation as the most important ones. We employ an iterative Ensemble Kalman Filter (EnKF) with an augmented state. Based on a single rain event, we are able to reduce all uncertainties directly, except for the intermittent violation of the local equilibrium assumption. We detect these times by analyzing the temporal evolution of estimated parameters. By introducing a closed-eye period - during which we do not estimate parameters, but only guide the state based on measurements - we can bridge these times. The introduced closed-eye period ensured constant parameters, suggesting that they resemble the believed true material properties. The closed-eye period improves predictions during periods when the local equilibrium assumption is met, but consequently worsens predictions when the assumption is violated. Such a prediction requires a description of the dynamics during local non-equilibrium phases, which remains an open challenge.

Hillslope-scale experiment demonstrates role of convergence during two-step saturation

USGS Publications Warehouse

Gevaert, A. I.; Teuling, A. J.; Uijlenhoet, R.; DeLong, Stephen B.; Huxman, T. E.; Pangle, L. A.; Breshears, David D.; Chorover, J.; Pelletier, John D.; Saleska, S. R.; Zeng, X.; Troch, Peter A.

2014-01-01

Subsurface flow and storage dynamics at hillslope scale are difficult to ascertain, often in part due to a lack of sufficient high-resolution measurements and an incomplete understanding of boundary conditions, soil properties, and other environmental aspects. A continuous and extreme rainfall experiment on an artificial hillslope at Biosphere 2's Landscape Evolution Observatory (LEO) resulted in saturation excess overland flow and gully erosion in the convergent hillslope area. An array of 496 soil moisture sensors revealed a two-step saturation process. First, the downward movement of the wetting front brought soils to a relatively constant but still unsaturated moisture content. Second, soils were brought to saturated conditions from below in response to rising water tables. Convergent areas responded faster than upslope areas, due to contributions from lateral subsurface flow driven by the topography of the bottom boundary, which is comparable to impermeable bedrock in natural environments. This led to the formation of a groundwater ridge in the convergent area, triggering saturation excess runoff generation. This unique experiment demonstrates, at very high spatial and temporal resolution, the role of convergence on subsurface storage and flow dynamics. The results bring into question the representation of saturation excess overland flow in conceptual rainfall-runoff models and land-surface models, since flow is gravity-driven in many of these models and upper layers cannot become saturated from below. The results also provide a baseline to study the role of the co-evolution of ecological and hydrological processes in determining landscape water dynamics during future experiments in LEO.

Noninvasive methods for dynamic mapping of microbial populations across the landscape

NASA Astrophysics Data System (ADS)

Meredith, L. K.; Sengupta, A.; Troch, P. A.; Volkmann, T. H. M.

2017-12-01

Soil microorganisms drive key ecosystem processes, and yet characterizing their distribution and activity in soil has been notoriously difficult. This is due, in part, to the heterogeneous nature of their response to changing environmental and nutrient conditions across time and space. These dynamics are challenging to constrain in both natural and experimental systems because of sampling difficulty and constraints. For example, soil microbial sampling at the Landscape Evolution Observatory (LEO) infrastructure in Biosphere 2 is limited in efforts to minimize soil disruption to the long term experiment that aims to characterize the interacting biological, hydrological, and geochemical processes driving soil evolution. In this and other systems, new methods are needed to monitor soil microbial communities and their genetic potential over time. In this study, we take advantage of the well-defined boundary conditions on hydrological flow at LEO to develop a new method to nondestructively characterize in situ microbial populations. In our approach, we sample microbes from the seepage flow at the base of each of three replicate LEO hillslopes and use hydrological models to `map back' in situ microbial populations. Over the course of a 3-month periodic rainfall experiment we collected samples from the LEO outflow for DNA and extraction and microbial community composition analysis. These data will be used to describe changes in microbial community composition over the course of the experiment. In addition, we will use hydrological flow models to identify the changing source region of discharge water over the course of periodic rainfall pulses, thereby mapping back microbial populations onto their geographic origin in the slope. These predictions of in situ microbial populations will be ground-truthed against those derived from destructive soil sampling at the beginning and end of the rainfall experiment. Our results will show the suitability of this method for long-term, non-destructive monitoring of the microbial communities that contribute to soil evolution in this large-scale model system. Furthermore, this method may be useful for other study systems with limitations to destructive sampling including other model infrastructures and natural landscapes.

A new method of fully three dimensional analysis of stress field in the soil layer of a soil-mantled hillslope

NASA Astrophysics Data System (ADS)

Wu, Y. H.; Nakakita, E.

2017-12-01

Hillslope stability is highly related to stress equilibrium near the top surface of soil-mantled hillslopes. Stress field in a hillslope can also be significantly altered by variable groundwater motion under the rainfall influence as well as by different vegetation above and below the slope. The topographic irregularity, biological effects from vegetation and variable rainfall patterns couple with others to make the prediction of shallow landslide complicated and difficult. In an increasing tendency of extreme rainfall, the mountainous area in Japan has suffered more and more shallow landslides. To better assess shallow landslide hazards, we would like to develop a new mechanically-based method to estimate the fully three-dimensional stress field in hillslopes. The surface soil-layer of hillslope is modelled as a poroelastic medium, and the tree surcharge on the slope surface is considered as a boundary input of stress forcing. The modelling of groundwater motion is involved to alter effective stress state in the soil layer, and the tree root-reinforcement estimated by allometric equations is taken into account for influencing the soil strength. The Mohr-Coulomb failure theory is then used for locating possible yielding surfaces, or says for identifying failure zones. This model is implemented by using the finite element method. Finally, we performed a case study of the real event of massive shallow landslides occurred in Hiroshima in August, 2014. The result shows good agreement with the field condition.

Comparing ordinary kriging and inverse distance weighting for soil as pollution in Beijing.

PubMed

Qiao, Pengwei; Lei, Mei; Yang, Sucai; Yang, Jun; Guo, Guanghui; Zhou, Xiaoyong

2018-06-01

Spatial interpolation method is the basis of soil heavy metal pollution assessment and remediation. The existing evaluation index for interpolation accuracy did not combine with actual situation. The selection of interpolation methods needs to be based on specific research purposes and research object characteristics. In this paper, As pollution in soils of Beijing was taken as an example. The prediction accuracy of ordinary kriging (OK) and inverse distance weighted (IDW) were evaluated based on the cross validation results and spatial distribution characteristics of influencing factors. The results showed that, under the condition of specific spatial correlation, the cross validation results of OK and IDW for every soil point and the prediction accuracy of spatial distribution trend are similar. But the prediction accuracy of OK for the maximum and minimum is less than IDW, while the number of high pollution areas identified by OK are less than IDW. It is difficult to identify the high pollution areas fully by OK, which shows that the smoothing effect of OK is obvious. In addition, with increasing of the spatial correlation of As concentration, the cross validation error of OK and IDW decreases, and the high pollution area identified by OK is approaching the result of IDW, which can identify the high pollution areas more comprehensively. However, because the semivariogram constructed by OK interpolation method is more subjective and requires larger number of soil samples, IDW is more suitable for spatial prediction of heavy metal pollution in soils.

Modelling the impact of climatic conditions and plant species on the nitrogen release from mulch of legumes at the soil surface

NASA Astrophysics Data System (ADS)

Gaudinat, Germain; Lorin, Mathieu; Valantin-morison, Muriel; Garnier, Patricia

2015-04-01

Cover crops provide multiple services to the agro ecosystem. Among them, the use of legumes as cover crop is one of the solutions for limiting the use of herbicides, mineral fertilizers, and insecticides. However, the dynamic of mineralization is difficult to understand because of the difficulty of measuring nitrogen release from mulch in field. Indeed, residues are degraded at the soil surface as mulch, while the nitrogen uptake by the main crop occurred simultaneously in the soil. This work aims to study the dynamics of nitrogen mineralization from legume residues through i) the use of a model able to describe the physical and biological dynamic of mulch and ii) a data set from a field experiment of intercropping systems "oilseed rape-legumes" from different species (grass pea, lentil, Berseem clover, field pea, vetch). The objective of the simulations is to identify the variations of expected quantities of nitrogen from different legumes. The soil-plant model of mulch decomposition PASTIS-Mulch was used to determine the nitrogen supply from mulch available for rapeseed. These simulation results were compared to the data collected in the experimental field of Grignon (France). We performed analyzes of biochemical and physical characteristics of legume residues and monitored the evolution of mulches (moisture, density, cover surface, biomass) in fields. PASTIS simulations of soil temperature, soil moisture, mulch humidity and mulch decomposition were close to the experimental results. The PASTIS model was suitable to simulate the dynamic of legume mulches in the case of "rape - legume" associations. The model simulated nitrogen restitution of aerial and root parts. We found a more rapid nitrogen release by grass pea than other species. Vetch released less nitrogen than the other species. The scenarios for climate conditions were : i) a freezing in December that causes the destruction of plants, or a destruction by herbicide in March, ii) a strong or a weak rainy spring. Climatic conditions had a strong impact on the simulated release of nitrogen. Nitrogen supply was higher when degradation begun early with a rainy spring. Conversely, the degradation was lower when the degradation started late with a dry spring. Root release was less sensitive to climate and most of the nitrogen in the roots returned to the soil in a few weeks. The impact of "species" on the decomposition was explained not only by their chemical properties but also by their physical properties. The climatic conditions had different effects according to the species.

Application of time-lapse ERT to characterize soil-water-disease interactions of young citrus trees

NASA Astrophysics Data System (ADS)

Peddinti, S. R.; Kbvn, D. P.; Ranjan, S.; R M, P. G.

2016-12-01

Vidarbha region in Maharashtra, India is witnessing a continuous decrease in orange crop due to the propagation of `Phytopthora root rot', a water mold disease. Under favorable conditions, the disease causing bacteria can attack the plant root system and propagates to the surface (where first visual impression is made), making difficult to regain the plant health. This research aims at co-relating eco-hydrological fluxes with disease sensing parameters of orange trees. Two experimental plots around a healthy-young and declined-young orange trees were selected for our analysis. A 3-dimentional electrical resistivity tomography (ERT) (Figure) was carried at each plot to quantify the soil moisture distribution at a vadose zone. Pedo-electric relations were obtained considering modified Archie's law parameters. ERT derived moisture data was validated with time domain reflectometry (TDR) point observations. Soil moisture profiles derived from ERT were observed to be differ marginally between the two plots. Disease quantification was done by estimating the density of Phytopthora spp. inoculum in soils sampled along the root zone. Identification of Phytopthora spp. was done in the laboratory using taxonomic and morphologic criteria of the colonies. Spatio-temporal profiles of soil moisture and inoculum density were then co-related to comment on the eco-hydrological fluxes contributing to the health propagation of root rot in orange tree for implementing effective water management practices.

Methods to test the interactive effects of drought and plant invasion on ecosystem structure and function using complementary common garden and field experiments.

PubMed

Alba, Christina; NeSmith, Julienne E; Fahey, Catherine; Angelini, Christine; Flory, Stephen Luke

2017-03-01

Abiotic global change drivers affect ecosystem structure and function, but how they interact with biotic factors such as invasive plants is understudied. Such interactions may be additive, synergistic, or offsetting, and difficult to predict. We present methods to test the individual and interactive effects of drought and plant invasion on native ecosystems. We coupled a factorial common garden experiment containing resident communities exposed to drought (imposed with rainout shelters) and invasion with a field experiment where the invader was removed from sites spanning a natural soil moisture gradient. We detail treatments and their effects on abiotic conditions, including soil moisture, light, temperature, and humidity, which shape community and ecosystem responses. Ambient precipitation during the garden experiment exceeded historic norms despite severe drought in prior years. Soil moisture was 48% lower in drought than ambient plots, but the invader largely offset drought effects. Additionally, temperature and light were lower and humidity higher in invaded plots. Field sites spanned up to a 10-fold range in soil moisture and up to a 2.5-fold range in light availability. Invaded and resident vegetation did not differentially mediate soil moisture, unlike in the garden experiment. Herbicide effectively removed invaded and resident vegetation, with removal having site-specific effects on soil moisture and light availability. However, light was generally higher in invader-removal than control plots, whereas resident removal had less effect on light, similar to the garden experiment. Invasion mitigated a constellation of abiotic conditions associated with drought stress in the garden experiment. In the field, where other factors co-varied, these patterns did not emerge. Still, neither experiment suggested that drought and invasion will have synergistic negative effects on ecosystems, although invasion can limit light availability. Coupling factorial garden experiments with field experiments across environmental gradients will be effective for predicting how multiple stressors interact in natural systems.

Correlation of fully-softened shear strength of clay soil with index properties : phase I.

DOT National Transportation Integrated Search

2010-09-01

Shallow slope failures in clay soils cause many millions of dollars of damage annually on highway : embankments and cut slopes and necessitate difficult and expensive repairs that negatively : impact budgets, traffic flow, and the environment. The em...

A Root water uptake model to compensate disease stress in citrus trees

NASA Astrophysics Data System (ADS)

Peddinti, S. R.; Kambhammettu, B. P.; Lad, R. S.; Suradhaniwar, S.

2017-12-01

Plant root water uptake (RWU) controls a number of hydrologic fluxes in simulating unsaturated flow and transport processes. Variable saturated models that simulate soil-water-plant interactions within the rizhosphere do not account for the health of the tree. This makes them difficult to analyse RWU patterns for diseased trees. Improper irrigation management activities on diseased (Phytopthora spp. affected) citrus trees of central India has resulted in a significant reduction in crop yield accompanied by disease escalation. This research aims at developing a quantitative RWU model that accounts for the reduction in water stress as a function of plant disease level (hereafter called as disease stress). A total of four research plots with varying disease severity were considered for our field experimentation. A three-dimensional electrical resistivity tomography (ERT) was performed to understand spatio-temporal distribution in soil moisture following irrigation. Evaporation and transpiration were monitored daily using micro lysimeter and sap flow meters respectively. Disease intensity was quantified (on 0 to 9 scale) using pathological analysis on soil samples. Pedo-physocal and pedo-electric relations were established under controlled laboratory conditions. A non-linear disease stress response function for citrus trees was derived considering phonological, hydrological, and pathological parameters. Results of numerical simulations conclude that the propagation of error in RWU estimates by ignoring the health condition of the tree is significant. The developed disease stress function was then validated in the presence of deficit water and nutrient stress conditions. Results of numerical analysis showed a good agreement with experimental data, corroborating the need for alternate management practices for disease citrus trees.

Application of a process-based shallow landslide hazard model over a broad area in Central Italy

USGS Publications Warehouse

Gioia, Eleonora; Speranza, Gabriella; Ferretti, Maurizio; Godt, Jonathan W.; Baum, Rex L.; Marincioni, Fausto

2015-01-01

Process-based models are widely used for rainfall-induced shallow landslide forecasting. Previous studies have successfully applied the U.S. Geological Survey’s Transient Rainfall Infiltration and Grid-Based Regional Slope-Stability (TRIGRS) model (Baum et al. 2002) to compute infiltration-driven changes in the hillslopes’ factor of safety on small scales (i.e., tens of square kilometers). Soil data input for such models are difficult to obtain across larger regions. This work describes a novel methodology for the application of TRIGRS over broad areas with relatively uniform hydrogeological properties. The study area is a 550-km2 region in Central Italy covered by post-orogenic Quaternary sediments. Due to the lack of field data, we assigned mechanical and hydrological property values through a statistical analysis based on literature review of soils matching the local lithologies. We calibrated the model using rainfall data from 25 historical rainfall events that triggered landslides. We compared the variation of pressure head and factor of safety with the landslide occurrence to identify the best fitting input conditions. Using calibrated inputs and a soil depth model, we ran TRIGRS for the study area. Receiver operating characteristic (ROC) analysis, comparing the model’s output with a shallow landslide inventory, shows that TRIGRS effectively simulated the instability conditions in the post-orogenic complex during historical rainfall scenarios. The implication of this work is that rainfall-induced landslides over large regions may be predicted by a deterministic model, even where data on geotechnical and hydraulic properties as well as temporal changes in topography or subsurface conditions are not available.

Modern Sorters for Soil Segregation on Large Scale Remediation Projects

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

Shonka, J.J.; Kelley, J.E.; O'Brien, J.M.

2008-01-15

In the mid-1940's, Dr. C. Lapointe developed a Geiger tube based uranium ore scanner and picker to replace hand-cobbing. In the 1990's, a modern version of the Lapointe Picker for soil sorting was developed around the need to clean the Johnston Atoll of plutonium. It worked well with sand, but these systems are ineffective with soil, especially with wet conditions. Additionally, several other constraints limited throughput. Slow moving belts and thin layers of material on the belt coupled with the use of multiple small detectors and small sorting gates make these systems ineffective for high throughput. Soil sorting of clay-bearingmore » soils and building debris requires a new look at both the material handling equipment, and the radiation detection methodology. A new class of Super-Sorters has attained throughput of one hundred times that of the old designs. Higher throughput means shorter schedules which reduce costs substantially. The planning, cost, implementation, and other site considerations for these new Super-Sorters are discussed. Modern soil segregation was developed by Ed Bramlitt of the Defense Nuclear Agency for clean up at Johnston Atoll. The process eventually became the Segmented Gate System (SGS). This system uses an array of small sodium iodide (NaI) detectors, each viewing a small volume (segment), that control a gate. The volume in the gate is approximately one kg. This system works well when the material to be processed is sand; however, when the material is wet and sticky (soils with clays) the system has difficulty moving the material through the gates. Super-Sorters are a new class of machine designed to take advantage of high throughput aggregate processing conveyors, large acquisition volumes, and large NaI detectors using gamma spectroscopy. By using commercially available material handling equipment, the system can attain processing rates of up to 400 metric tons/hr with spectrum acquisition approximately every 0.5 sec, so the acquisition volume is 50 kilograms or less. Smaller sorting volumes can be obtained with lower throughput or by re-sorting the diverted material. This equipment can also handle large objects. The use of spectroscopy systems allows several regions of- interest to be set. Super-Sorters can bring waste processing charges down to less than $30/ metric ton on smaller jobs and can save hundreds of dollars per metric ton in disposal charges. The largest effect on the overall project cost occurs during planning and implementation. The overall goal is reduction of the length of the project, which dictates the most efficient soil processing. With all sorting systems the parameters that need to be accounted for are matrix type, soil feed rate, soil pre-processing, site conditions, and regulatory issues. The soil matrix and its ability to flow are extremely crucial to operations. It is also important to consider that as conditions change (i.e., moisture), the flowability of the soil matrix will change. Many soil parameters have to be considered: cohesive strength, internal and wall friction, permeability, and bulk density as a function of consolidating pressure. Clay bearing soils have very low permeability and high cohesive strength which makes them difficult to process, especially when wet. Soil feed speed is dependent on the equipment present and the ability to move the soil in the Super-Sorter processing area. When a Super-Sorter is running at 400 metric tons per hour it is difficult to feed the system. As an example, front-end loaders with large buckets would move approximately 5-10 metric tons of material, and 400 metric tons per hour would require 50-100 bucket-loads per hour to attain. Because the flowability of the soil matrix is important, poor material is often pre-processed before it is added to the feed hopper of the 'survey' conveyor. This pre-processing can consist of a 'grizzly' to remove large objects from the soil matrix, followed screening plant to prepare the soil so that it feeds well. Hydrated lime can be added to improve material properties. Site conditions (site area, typical weather conditions, etc.) also play a large part in project planning. Downtime lengthens project schedule and costs. The system must be configured to handle weather conditions or other variables that affect throughput. The largest single factor that plays into the project design is the regulatory environment. Before a sorter can be utilized, an averaging mass must be established by the regulator(s). There currently are no standards or guidelines in this area. The differences between acquisition mass and averaging mass are very important. The acquisition mass is defined based on the acquisition time and the geometry of the detectors. The averaging mass can then be as small as the acquisition mass or as large as several hundred tons (the averaging mass is simply the sum of a number of acquisitions). It is important to define volumetric limits and any required point-source limits. Super-Sorters handle both of these types of limits simultaneously. The minimum detectable activity for Super- Sorters is a function of speed. The chart below illustrates the detection confidence level for a 0.1 {mu}Ci point source of Ra-226 vs alarm point for three different sorter process rates. The minimal detection activity and diversion volume for a Super-Sorter is also a function of the acquisition mass. The curves were collected using a 0-15 kg acquisition mass. Diversion volumes ranged from 20-30 kg for a point source diversion. Soil Super-Sorters should be considered for every D and D project where it is desirable to reduce the waste stream. A volume reduction of 1:1000 can be gained for each pass through a modern sorter, resulting in significant savings in disposal costs.« less

Bioremediation of diesel and lubricant oil-contaminated soils using enhanced landfarming system.

PubMed

Wang, Sih-Yu; Kuo, Yu-Chia; Hong, Andy; Chang, Yu-Min; Kao, Chih-Ming

2016-12-01

Lubricant and diesel oil-polluted sites are difficult to remediate because they have less volatile and biodegradable characteristics. The goal of this research was to evaluate the potential of applying an enhanced landfarming to bioremediate soils polluted by lubricant and diesel. Microcosm study was performed to evaluate the optimal treatment conditions with the addition of different additives (nutrients, addition of activated sludge from oil-refining wastewater facility, compost, TPH-degrading bacteria, and fern chips) to enhance total petroleum hydrocarbon (TPH) removal. To simulate the aerobic landfarming biosystem, air in the microcosm headspace was replaced once a week. Results demonstrate that the additives of activated sludge and compost could result in the increase in soil microbial populations and raise TPH degradation efficiency (up to 83% of TPH removal with 175 days of incubation) with initial (TPH = 4100 mg/kg). The first-order TPH degradation rate reached 0.01 1/d in microcosms with additive of activated sludge (mass ratio of soil to inocula = 50:1). The soil microbial communities were determined by nucleotide sequence analyses and 16S rRNA-based denatured gradient gel electrophoresis. Thirty-four specific TPH-degrading bacteria were detected in microcosm soils. Chromatograph analyses demonstrate that resolved peaks were more biodegradable than unresolved complex mixture. Results indicate that more aggressive remedial measures are required to enhance the TPH biodegradation, which included the increase of (1) microbial population or TPH-degrading bacteria, (2) biodegradable carbon sources, (3) nutrient content, and (4) soil permeability. Copyright © 2016 Elsevier Ltd. All rights reserved.

Distinct Soil Bacterial Communities Revealed under a Diversely Managed Agroecosystem

PubMed Central

Shange, Raymon S.; Ankumah, Ramble O.; Ibekwe, Abasiofiok M.; Zabawa, Robert; Dowd, Scot E.

2012-01-01

Land-use change and management practices are normally enacted to manipulate environments to improve conditions that relate to production, remediation, and accommodation. However, their effect on the soil microbial community and their subsequent influence on soil function is still difficult to quantify. Recent applications of molecular techniques to soil biology, especially the use of 16S rRNA, are helping to bridge this gap. In this study, the influence of three land-use systems within a demonstration farm were evaluated with a view to further understand how these practices may impact observed soil bacterial communities. Replicate soil samples collected from the three land-use systems (grazed pine forest, cultivated crop, and grazed pasture) on a single soil type. High throughput 16S rRNA gene pyrosequencing was used to generate sequence datasets. The different land use systems showed distinction in the structure of their bacterial communities with respect to the differences detected in cluster analysis as well as diversity indices. Specific taxa, particularly Actinobacteria, Acidobacteria, and classes of Proteobacteria, showed significant shifts across the land-use strata. Families belonging to these taxa broke with notions of copio- and oligotrphy at the class level, as many of the less abundant groups of families of Actinobacteria showed a propensity for soil environments with reduced carbon/nutrient availability. Orders Actinomycetales and Solirubrobacterales showed their highest abundance in the heavily disturbed cultivated system despite the lowest soil organic carbon (SOC) values across the site. Selected soil properties ([SOC], total nitrogen [TN], soil texture, phosphodiesterase [PD], alkaline phosphatase [APA], acid phosphatase [ACP] activity, and pH) also differed significantly across land-use regimes, with SOM, PD, and pH showing variation consistent with shifts in community structure and composition. These results suggest that use of pyrosequencing along with traditional analysis of soil physiochemical properties may provide insight into the ecology of descending taxonomic groups in bacterial communities. PMID:22844402

Distinct soil bacterial communities revealed under a diversely managed agroecosystem.

PubMed

Shange, Raymon S; Ankumah, Ramble O; Ibekwe, Abasiofiok M; Zabawa, Robert; Dowd, Scot E

2012-01-01

Land-use change and management practices are normally enacted to manipulate environments to improve conditions that relate to production, remediation, and accommodation. However, their effect on the soil microbial community and their subsequent influence on soil function is still difficult to quantify. Recent applications of molecular techniques to soil biology, especially the use of 16S rRNA, are helping to bridge this gap. In this study, the influence of three land-use systems within a demonstration farm were evaluated with a view to further understand how these practices may impact observed soil bacterial communities. Replicate soil samples collected from the three land-use systems (grazed pine forest, cultivated crop, and grazed pasture) on a single soil type. High throughput 16S rRNA gene pyrosequencing was used to generate sequence datasets. The different land use systems showed distinction in the structure of their bacterial communities with respect to the differences detected in cluster analysis as well as diversity indices. Specific taxa, particularly Actinobacteria, Acidobacteria, and classes of Proteobacteria, showed significant shifts across the land-use strata. Families belonging to these taxa broke with notions of copio- and oligotrphy at the class level, as many of the less abundant groups of families of Actinobacteria showed a propensity for soil environments with reduced carbon/nutrient availability. Orders Actinomycetales and Solirubrobacterales showed their highest abundance in the heavily disturbed cultivated system despite the lowest soil organic carbon (SOC) values across the site. Selected soil properties ([SOC], total nitrogen [TN], soil texture, phosphodiesterase [PD], alkaline phosphatase [APA], acid phosphatase [ACP] activity, and pH) also differed significantly across land-use regimes, with SOM, PD, and pH showing variation consistent with shifts in community structure and composition. These results suggest that use of pyrosequencing along with traditional analysis of soil physiochemical properties may provide insight into the ecology of descending taxonomic groups in bacterial communities.

Salinity management using an anionic polymer in a pecan field with calcareous-sodic soil.

PubMed

Ganjegunte, Girisha K; Sheng, Zhuping; Braun, Robert J

2011-01-01

Soil salinity and sodicity have long been recognized as the major concerns for irrigated agriculture in the Trans-Pecos Basin, where fields are being flood irrigated with Rio Grande River water that has elevated salinity. Reclamation of these salt-affected lands is difficult due to fine-texture, high shrink-swell soils with low permeability. Conventional practice of subsoiling to improve soil permeability is expensive and has had limited success on the irrigated soils that have appreciable amounts of readily weatherable Ca minerals. If these native Ca sources can be effectively used to counter sodicity, it can improve soil permeability and reduce amelioration costs. This study evaluated the effects of 3 yr of polyacrylamide (PAM) application at 10 mg L concentration during the first irrigation of the season to evaluate soil permeability, in situ Ca mineral dissolution, and leaching of salts from the effective root zone in a pecan field of El Paso County, TX. Results indicated that PAM application improved water movement throughout the effective root zone that resulted in Na leaching. Polymer application significantly decreased CaCO (estimated based on inorganic C analysis) concentrations in the top 45 cm compared with baseline levels, indicating solubilization and redistribution of calcite. The PAM application also reduced soil electrical conductivity (EC) in the top 60 cm (4.64-2.76 dS m) and sodium adsorption ratio (SAR) from 13.1 to 5.7 mmol L in the top 75-cm depths. As evidence of improved soil conditions, pecan nut yields increased by 34% in PAM-treated fields over the control. Results suggested that PAM application helped in effective use of native Ca sources present in soils of the study site and reduced Na by improving soil permeability. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

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.

High-resolution isotope measurements resolve rapid ecohydrological dynamics at the soil-plant interface.

PubMed

Volkmann, Till H M; Haberer, Kristine; Gessler, Arthur; Weiler, Markus

2016-05-01

Plants rely primarily on rainfall infiltrating their root zones - a supply that is inherently variable, and fluctuations are predicted to increase on most of the Earth's surface. Yet, interrelationships between water availability and plant use on short timescales are difficult to quantify and remain poorly understood. To overcome previous methodological limitations, we coupled high-resolution in situ observations of stable isotopes in soil and transpiration water. We applied the approach along with Bayesian mixing modeling to track the fate of (2) H-labeled rain pulses following drought through soil and plants of deciduous tree ecosystems. We resolve how rainwater infiltrates the root zones in a nonequilibrium process and show that tree species differ in their ability to quickly acquire the newly available source. Sessile oak (Quercus petraea) adjusted root uptake to vertical water availability patterns under drought, but readjustment toward the rewetted topsoil was delayed. By contrast, European beech (Fagus sylvatica) readily utilized water from all soil depths independent of water depletion, enabling faster uptake of rainwater. Our results demonstrate that species-specific plasticity and responses to water supply fluctuations on short timescales can now be identified and must be considered to predict vegetation functional dynamics and water cycling under current and future climatic conditions. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

Field sampling of loose erodible material: A new method to consider the full particle-size range

NASA Astrophysics Data System (ADS)

Klose, Martina; Gill, Thomas E.

2017-04-01

The aerodynamic entrainment of sand and dust is determined by the atmospheric forces exerted onto the soil surface and by the soil-surface condition. If aerodynamic forces are strong enough to generate sand and dust lifting, the entrained sediment amount still critically depends on the supply of loose particles readily available for lifting. This loose erodible material (LEM) is sometimes defined as the thin layer of loose particles on top of a crusted surface. Here, we more generally define LEM as loose particles or particle aggregates available for entrainment, which may or may not overlay a soil crust. Field sampling of LEM is difficult and only few attempts have been made. Motivated by saltation as the most efficient process to generate dust emission, methods have focused on capturing LEM in the sand-size range or on determining the potential of a soil surface to be eroded by aerodynamic forces and particle impacts. Here, our focus is to capture the full particle-size distribution of LEM in situ, including the dust and sand-size range, to investigate the potential and likelihood of dust emission mechanisms (aerodynamic entrainment, saltation bombardment, aggregate disintegration) to occur. A new vacuum method is introduced and its capability to sample LEM without significant alteration of the LEM particle-size distribution is investigated.

Modelling landslide liquefaction, mobility bifurcation and the dynamics of the 2014 Oso disaster

USGS Publications Warehouse

Iverson, Richard M.; George, David L.

2016-01-01

Some landslides move slowly or intermittently downslope, but others liquefy during the early stages of motion, leading to runaway acceleration and high-speed runout across low-relief terrain. Mechanisms responsible for this disparate behaviour are represented in a two-phase, depth-integrated, landslide dynamics model that melds principles from soil mechanics, granular mechanics and fluid mechanics. The model assumes that gradually increasing pore-water pressure causes slope failure to nucleate at the weakest point on a basal slip surface in a statically balanced mass. Failure then spreads to adjacent regions as a result of momentum exchange. Liquefaction is contingent on pore-pressure feedback that depends on the initial soil state. The importance of this feedback is illustrated by using the model to study the dynamics of a disastrous landslide that occurred near Oso, Washington, USA, on 22 March 2014. Alternative simulations of the event reveal the pronounced effects of a landslide mobility bifurcation that occurs if the initial void ratio of water-saturated soil equals the lithostatic, critical-state void ratio. They also show that the tendency for bifurcation increases as the soil permeability decreases. The bifurcation implies that it can be difficult to discriminate conditions that favour slow landsliding from those that favour liquefaction and long runout.

Evaluation and determination of soil remediation schemes using a modified AHP model and its application in a contaminated coking plant.

PubMed

Li, Xingang; Li, Jia; Sui, Hong; He, Lin; Cao, Xingtao; Li, Yonghong

2018-07-05

Soil remediation has been considered as one of the most difficult pollution treatment tasks due to its high complexity in contaminants, geological conditions, usage, urgency, etc. The diversity in remediation technologies further makes quick selection of suitable remediation schemes much tougher even the site investigation has been done. Herein, a sustainable decision support hierarchical model has been developed to select, evaluate and determine preferred soil remediation schemes comprehensively based on modified analytic hierarchy process (MAHP). This MAHP method combines competence model and the Grubbs criteria with the conventional AHP. It not only considers the competence differences among experts in group decision, but also adjusts the big deviation caused by different experts' preference through sample analysis. This conversion allows the final remediation decision more reasonable. In this model, different evaluation criteria, including economic effect, environmental effect and technological effect, are employed to evaluate the integrated performance of remediation schemes followed by a strict computation using above MAHP. To confirm the feasibility of this developed model, it has been tested by a benzene workshop contaminated site in Beijing coking plant. Beyond soil remediation, this MAHP model would also be applied in other fields referring to multi-criteria group decision making. Copyright © 2018 Elsevier B.V. All rights reserved.

SURFEX modeling of soil moisture fields over the Valencia Anchor Station and their comparison to different SMOS products and in situ measurements

NASA Astrophysics Data System (ADS)

Coll Pajaron, M. Amparo; Lopez-Baeza, Ernesto; Fernandez-Moran, Roberto; Samiro Khodayar-Pardo, D.

2016-07-01

Soil moisture is a difficult variable to obtain proper representation because of its high temporal and spatial variability. It is a significant parameter in agriculture, hydrology, meteorology and related disciplines. {it SVAT (Soil-Vegetation-Atmosphere-Transfer)} models can be used to simulate the temporal behaviour and spatial distribution of soil moisture in a given area. In this work, we use the {bf SURFEX (Surface Externalisée)} model developed at the {it Centre National de Recherches Météorologiques (CNRM)} at Météo-France (http://www.cnrm.meteo.fr/surfex/) to simulate soil moisture at the {bf Valencia Anchor Station}. SURFEX integrates the {bf ISBA (Interaction Sol-Biosphère-Atmosphère}; surfaces with vegetation) module to describe the land surfaces (http://www.cnrm.meteo.fr/isbadoc/model.html) that have been adapted to describe the land covers of our study area. The Valencia Anchor Station was chosen as a core validation site for the {it SMOS (Soil Moisture and Ocean Salinity)} mission and as one of the hydrometeorological sites for the {it HyMeX (HYdrological cycle in Mediterranean EXperiment)} programme. This site represents a reasonably homogeneous and mostly flat area of about 50x50 km2. The main cover type is vineyards (65%), followed by fruit trees, shrubs, and pine forests, and a few small scattered industrial and urban areas. Except for the vineyard growing season, the area remains mostly under bare soil conditions. In spite of its relatively flat topography, the small altitude variations of the region clearly influence climate. This oscillates between semiarid and dry sub-humid. Annual mean temperatures are between 12 ºC and 14.5 ºC, and annual precipitation is about 400-450 mm. The duration of frost free periods is from May to November, with maximum precipitation in spring and autumn. The first part of this investigation consists in simulating soil moisture fields over the Valencia Anchor Station to be compared with SMOS level-2 (resolution 15 km) and level-3 (resolution 25 km) soil moisture maps and high resolution SMOS pixel-disaggregated soil moisture products, obtained by combining SMOS level-2 with MODIS NDVI and LST data (resolution 1 km) (Piles et al., 2011). In situ measurements from the Valencia Anchor Station network of soil moisture stations are also available as reference covering a reduced number of different vegetation cover and soil types, as well as estimations from the ESA ELBARA-II L-band radiometer installed over a vineyard crop to monitor SMOS validation conditions. Different interpolation methods have been applied to all significant atmospheric forcing parameters from the two met stations available in the area (pressure, temperature, relative humidity and precipitation) in order to obtain a good representation of soil conditions. The period of investigation covers the complete year 2012 of which we will particularly focus on selected periods.

Soil and salinity mobilization and transport in the Colorado River Basin

Treesearch

Cole Green Rossi; Mark A. Weitz; Kossi Nouwakpo; Ken McGwire

2016-01-01

Federally, the evaluated potential of soil loss risk in national reports in the past and ways to adapt to be proactive in preventing accelerated soil loss on rangelands has been incomplete. The areas where it is difficult to measure due to the complexities of multiple interactions (splash, sheet and rill formation, landscape dominated by wind and water processes,...

Emergence of native plant seeds in response to seed pelleting, planting depth, scarification, and soil anti-crusting treatment, 2009

Treesearch

Clint Shock; Erik Feibert; Lamont Saunders; Nancy Shaw

2010-01-01

Seed of native plants is needed to restore rangelands of the Intermountain West. Reliable commercial seed production is desirable to provide the quantity of seed needed for restoration efforts. Establishment of native seed crops has been difficult, because fall-planted seed is susceptible to bird damage, soil crusting, and soil erosion. Fall planting is important for...

Sensing technologies to measure metabolic activities in soil and assess its health conditions

NASA Astrophysics Data System (ADS)

De Cesare, Fabrizio; Macagnano, Antonella

2013-04-01

Soil is a complex ecosystem comprised of several and mutually interacting components, both abiotic (organo-mineral associations) and biotic (microbial and pedofaunal populations and plants), where a single parameter depends on other factors and affects the same and other factors, so that a network of influences among organisms coexists with the reciprocal actions between organisms and their environment. Therefore, it is difficult to undoubtedly determine what is the cause and what the effect within relationships between factors and processes. Soil is commonly studied through the evaluation and measurement of single parameters (e.g. the content of soil organic matter (SOM), microbial biomass, enzyme activities, pH, etc.), events (e.g. soil erosion, compaction, etc.) and processes (e.g. soil respiration, carbon fluxes, nitrification/denitrification, etc.), often carried out in laboratory conditions in order to limit the number of factors acting within the ecosystem under study, but missing the information about the global soil environment that way. In the last decade, several scientists have proposed and suggested the need for a holistic approach to soil ecosystems in different contexts. Recently, we have applied a sensing system developed in the last decades and capable of analysing complex mixtures of gases and volatiles (odours or aromas) in atmospheres, namely called electronic nose (EN). Typically, ENs are devices consisting of an array of differentially and partially specific, despite selective, sensors upon diverse coatings of sensitive films, i.e. interacting with single analytes of the same chemical class, despite not highly specific for a single substance, only, but showing also lower extent of cross-selectivity towards compounds of other chemical classes. ENs can be used in the classifications of odours by processing the collected responses of all sensors in the array through pattern recognition analyses, in order to obtain a chemical fingerprint (olfactory fingerprint) typical of the analysed air sample. Due to these features, we decided to apply such a sensing technology to the analyses of soil atmospheres, because several processes in soil, both abiotic and biotic, result in gas and/or volatile production and the dynamics of such releases may also be affected by several additional environmental factors, such as soil moisture, temperature, gas exchange rates with outer atmosphere, adsorption/desorption processes, etc. Then, the analysis of soil atmosphere may provide information about global soil conditions (e.g. soil quality and health), according to a holistic approach, where several factors are contemporarily taken into account. At the same time, the use of such a technology, if adequately trained on purpose, can supply information about a single or a pool of processes sharing similar features, which occur in soil over a certain period of time and mostly affecting soil atmosphere. According to these premises and hypotheses, we demonstrated that EN is an useful technology to measure soil microbial activity, through its correlation to specific metabolic activities occurring in soil (i.e. global and specific respiration and some enzyme activities), but also soil microbial biomass. On the basis of such evidences, we also were able to use this technology to assess the quality and health conditions of soil ecosystems in terms of metabolic indices previously identified, according to some metabolic parameters and biomass quantification of microbial populations. In other studies, we also applied EN technology, despite using a different set of sensors in the array, to analyse the atmosphere of soil ecosystems in order to assess their environmental conditions after contamination with polycyclic aromatic hydrocarbons (PAHs) (i.e. semivolatile - SVOCs - organic pollutants). In this case, EN technology resulted capable of distinguishing between contaminated and uncontaminated soils, according to the differences in a list of substances, occurring in the atmospheres of differently treated soils, which were identified through SPME-GC/MS analyses and then suggested to be responsible for the different classification. Analysing the EN responses, it was also possible to follow the degradation process of pollutants by resident microbial populations over time, on the basis of the contemporary decrease of contaminant and the increased release of CO2. Then, we suggest that EN technology may be usefully employed in the analyses of soil ecosystems in order to both supply information about global soil environment, according to the holistic approach, and about specific processes occurring therein. Furthermore, since EN technology resulted to be effective and successful in detecting processes in soil, in both natural and perturbed conditions, involving microbial populations, which are commonly considered as the most sensitive and responsive to soil environmental modifications, we suggest it might be reasonably employed in analyses concerning the assessment of soil quality and health. Consequently, such a technology may also be used to study several processes involving soil ecosystems, such as soil management practices, soil restoration, soil contamination and remediation, soil fertility, etc.

Radioisotopes (137Cs, 40K, 210Pb) indicate that cryoturbation processes in Alaskan tussock tundra are accelerated under deeper winter snow: results from short and long-term winter snow depth experiments

NASA Astrophysics Data System (ADS)

Blanc-Betes, E.; Sturchio, N. C.; Taneva, L.; Welker, J. M.; Guilderson, T. P.; Poghosyan, A.; Gonzalez-Meler, M. A.

2010-12-01

Permafrost soils cover 8.6% of the Earth land area and contain up to 50% of the global soil organic carbon (SOC) pool. Amplified warming in northern latitudes has resulted directly and/or indirectly in multiple structural and functional changes in arctic ecosystems which may lead to strong forcing feedbacks on the climate system. Cryoturbation is a dominant soil forming process in permafrost regions that results to the mixing of soil layers during freeze-thaw cycles, and may increase in rates following global warming. As a result, the active layer of cryoturbated soils can average 62% larger C stocks than those from non-cryoturbated ones. Cryoturbation is a critical overlooked driver of C dynamics in permafrost soils that will likely play a pivotal role in the fate of Arctic soil C under climate change conditions. However, cryoturbation phenomena is difficult to quantify. We measured cryoturbation rates using a multiple isotope approach at Toolik Lake, Alaska, in moist acidic tundra soils from short- and long-term snow addition experiments. Shifts in cryoturbation rates as affected by these manipulations were measured by the relative activity of natural and weapon-derived radioisotopes (e.g. 137Cs, 40K, 210Pb). By tracking the vertical distribution of these fallout and natural radioisotopes in soils and calculating soil diffusion coefficients, we were able to quantify cryoturbation mixing rates and sediment transport mechanisms that operate at multiannual time scales. Our results show an apparent uplift of buried organic matter to the surface as a result of soil thermal insulation and subsequent deepening of the active layer. These results sharply contrast with current notions that cryoturbation in Arctic systems results in net burial of organic matter, resulting in increased C storage at depth. Mechanisms of this mechanical mixing and its effects on C redistribution and storage of organic matter will be presented to shed light on this apparent contradiction.

Surface Analysis Evaluation of Handwipe Cleaning for the Space Shuttle RSRM

NASA Technical Reports Server (NTRS)

Lesley, Michael W.; Anderson, Erin L.; McCool, Alex (Technical Monitor)

2001-01-01

In this paper we discuss the role of surface-sensitive spectroscopy (electron spectroscopy for chemical analysis, or ESCA) in the selection of solvents to replace 1,1,1-trichloroethane in handwipe cleaning of bonding surfaces on NASA's Space Shuttle Reusable Solid Rocket Motor (RSRM). Removal of common process soils from a wide variety of metallic and polymeric substrates was characterized. The cleaning efficiency was usually more dependent on the type of substrate being cleaned and the specific process soil than on the solvent used. A few substrates that are microscopically rough or porous proved to be difficult to clean with any cleaner, and some soils were very tenacious and difficult to remove from any substrate below detection limits. Overall, the work showed that a wide variety of solvents will perform at least as well as 1,1,1-trichloroethane.

Soil intake of lactating dairy cows in intensive strip grazing systems.

PubMed

Jurjanz, S; Feidt, C; Pérez-Prieto, L A; Ribeiro Filho, H M N; Rychen, G; Delagarde, R

2012-08-01

Involuntary soil intake by cows on pasture can be a potential route of entry for pollutants into the food chain. Therefore, it appears necessary to know and quantify factors affecting soil intake in order to ensure the food safety in outside rearing systems. Thus, soil intake was determined in two Latin square trials with 24 and 12 lactating dairy cows. In Trial 1, the effect of pasture allowance (20 v. 35 kg dry matter (DM) above ground level/cow daily) was studied for two sward types (pure perennial ryegrass v. mixed perennial ryegrass-white clover) in spring. In Trial 2, the effect of pasture allowance (40 v. 65 kg DM above ground level/cow daily) was studied at two supplementation levels (0 or 8 kg DM of a maize silage-based supplement) in autumn. Soil intake was determined by the method based on acid-insoluble ash used as an internal marker. The daily dry soil intake ranged, between treatments, from 0.17 to 0.83 kg per cow in Trial 1 and from 0.15 to 0.85 kg per cow in Trial 2, reaching up to 1.3 kg during some periods. In both trials, soil intake increased with decreasing pasture allowance, by 0.46 and 0.15 kg in Trials 1 and 2, respectively. In Trial 1, this pasture allowance effect was greater on mixed swards than on pure ryegrass swards (0.66 v. 0.26 kg reduction of daily soil intake between medium and low pasture allowance, respectively). In Trial 2, the pasture allowance effect was similar at both supplementation levels. In Trial 2, supplemented cows ate much less soil than unsupplemented cows (0.20 v. 0.75 kg/day, respectively). Differences in soil intake between trials and treatments can be related to grazing conditions, particularly pre-grazing and post-grazing sward height, determining at least in part the time spent grazing close to the ground. A post-grazing sward height lower than 50 mm can be considered as a critical threshold. Finally, a dietary supplement and a low grazing pressure, that is, high pasture allowance increasing post-grazing sward height, would efficiently limit the risk for high level of soil intake, especially when grazing conditions are difficult. Pre-grazing and post-grazing sward heights, as well as faecal crude ash concentration appear to be simple and practical tools for evaluating the risk for critical soil intake in grazing dairy cows.

THE ARS-MISSOURI SOIL STRENGTH PROFILE SENSOR: CURRENT STATUS AND FUTURE PROSPECTS

USDA-ARS?s Scientific Manuscript database

Soil compaction that is induced by tillage and traction is an ongoing concern in crop production, and also has environmental consequences. Although cone penetrometers provide standardized compaction measurements, the pointwise data collected makes it difficult to obtain enough data to represent with...

Interaction between calcium and phosphate adsorption on goethite.

PubMed

Rietra, R P; Hiemstra, T; van Riemsdijk, W H

2001-08-15

Quantitatively, little is known about the ion interaction processes that are responsible for the binding of phosphate in soil, water, and sediment, which determine the bioavailability and mobility of phosphate. Studies have shown that metal hydroxides are often responsible for the binding of PO4 in soils and sediments, but the binding behavior of PO4 in these systems often differs significantly from adsorption studies on metal hydroxides in laboratory. The interaction between PO4 and Ca adsorption was studied on goethite because Ca can influence the PO4 adsorption equilibria. Since adsorption interactions are very difficult to discriminate from precipitation reactions, conditions were chosen to prevent precipitation of Ca-PO4 solids. Adsorption experiments of PO4 and Ca, individually and in combination, show a strong interaction between adsorbed Ca and PO4 on goethite for conditions below the saturation index of apatite. It is shown that it is possible to predict the adsorption and interaction of PO4 and Ca on electrostatic arguments using the model parameter values derived from the single-ion systems and without invoking ternary complex formation or precipitation. The model enables the prediction of the Ca-PO4 interaction for environmentally relevant calcium and phosphate concentrations.

The relative importance of hydrophobicity in determining runoff-infiltration processes in burned forest soils

NASA Astrophysics Data System (ADS)

Wittenberg, Lea; Malkinson, Dan; Voogt, Annelies; Leska, Danny; Argaman, Eli; Keesstra, Saskia

2010-05-01

Wildfires induce fundamental changes to vegetation and soil structure/texture which conseqeuntly have major impacts on infiltration capacity, overland flow generation, runoff and sediment yields. The relative importance, however, of fire-induced soil water repellency (WR) on hydrological and erosional processes is somewhat controversial, partially, as the direct effects of soil WR in-situ field conditions have been difficult to isolate. It is generally accepted that hydrophobicity is caused by the formation of organic substances in forest soils, while burning is considered to enhance this process. Given the complex response of the soil-vegetation system to burning, soil WR is only one of several affecting soil hydrology. Other factors include the physical sealing of soils triggered by rain drops energy, the increase in soil erodibility due to changes in soil aggregates, and the role of the ash in sealing the burned surface. The degree and spatial distribution of WR burned varies considerably with fire severity, soil and vegetation type, soil moisture content and time since burning. Nevertheless, given the inverse relationship between soil moisture and hydrophobicity, the role of the latter in determining overland flow during wet winters when the soil is mostly inundated, is marginal. Following a 60 ha wildfire, which took place at the Pe'eram catchment during July 2009, we assessed the spatio-temporal distribution of WR in a burned Pinus halepensis forest. The site, located in the Upper Galille, Israel, was severely burned; the combustion removed all understory vegetation and burned down some of the trunks, leaving a thick layer of ash. The soils composed of reddish-brown clay loam forest soil and terra rossa on limestone bedrock, greyish light rendzina characterises the marl and chalk exposures. To consider the effect of distance from trees, in-situ hydrophobicity was assessed within a week, month and five months after the fire, using the WDPT test. Measurements were taken in concentric circles around the burned trees at two soil depths. We complemented this investigation by conducting a series of laboratory simulations. Non-burned soil was taken for laboratory analysis and rainfall simulations. Four treatment types were conducted: non-burned soil, non-burned soil + pine needles, burned soil without ash (300°C/15 min. after adding pine needles) and burned soil with the residue ash (300°C/15 min. after adding pine needles). Hydrophobicity was measured in all trays. Constant rainfall intensity of 30 mm/hr was simulated until terminal infiltration rates were reached. The experimental trays were oven dried and simulated again to imitate the effect of second rainstorm. Preliminary results indicate strong surface WR (60% >180s) at a distance of 1m and at the subsurface (50% >180s) directly by the trunk. In the control non-burned site stronger WR was found in proximity to the trunks. While in the burned sites extreme values (>300s) were apparent (15-35%) and correlated with distance from the trunk, no corresponding patterns were noticed in the control trees. The attempt to create homogeneous layer of WR under controlled laboratory conditions yielded a scattered pattern of repellency, similar to the field conditions. In contrast to expected, the bare soil and bare soil covered by needles exhibited the highest and lowest infiltration rates, respectively, while the burned hydrophobic soils demonstrated intermediate rates. It is thus suggested that in some soils, WR might enhance infiltration capacity by creating a complex mosaic of runoff-generating and runoff-absorbing micro-patches. In the experimental non-burned soil a rapid crusting of the surface provided lateral connectivity whilst the accumulation of litter and organic matter blanket the surface and enhance the vertical conductivity. To better understand the role of WR in generating hydrological response, it is required to consider the 3D 'sponge like' properties of the WR soils.

Messenger RNA transcripts

Treesearch

Dan Cullen

2004-01-01

In contrast to DNA, messenger RNA (mRNA) in complex substrata is rarely analyzed, in large part because labile RNA molecules are difficult to purify. Nucleic acid extractions from fungi that colonize soil are particularly difficult and plagued by humic substances that interfere with Taq polymerase (Tebbe and Vahjen 1993 and references therein). Magnetic capture...

Understanding the Impact of Ground Water Treatment and Evapotranspiration Parameterizations in the NCEP Climate Forecast System (CFS) on Warm Season Predictions

NASA Astrophysics Data System (ADS)

Ek, M. B.; Yang, R.

2016-12-01

Skillful short-term weather forecasts, which rely heavily on quality atmospheric initial conditions, have a fundamental limit of about two weeks owing to the chaotic nature of the atmosphere. Useful forecasts at sub-seasonal to seasonal time scales, on the other hand, require well-simulated large-scale atmospheric response to slowly varying lower boundary forcings from both the ocean and land surface. The critical importance of ocean has been recognized, where the ocean indices have been used in a variety of climate applications. In contrast, the impact of land surface anomalies, especially soil moisture and associated evaporation, has been proven notably difficult to demonstrate. The Noah Land Surface Model (LSM) is the land component of NCEP CFS version 2 (CFSv2) used for seasonal predictions. The Noah LSM originates from the Oregon State University (OSU) LSM. The evaporation control in the Noah LSM is based on the Penman-Monteith equation, which takes into account the solar radiation, relative humidity, air temperature, and soil moisture effects. The Noah LSM is configured with four soil layers with a fixed depth of 2 meters and free drainage at the bottom soil layer. This treatment assumes that the soil water table depth is well within the specified range, and also potentially misrepresents the soil moisture memory effects at seasonal time scales. To overcome the limitation, an unconfined aquifer is attached to the bottom of the soil to allow the water table to move freely up and down. In addition, in conjunction with the water table, an alternative Ball-Berry photosynthesis-based evaporation parameterization is examined to evaluate the impact from using a different evaporation control methodology. Focusing on the 2011 and 2012 intense summer droughts in the central US, seasonal ensemble forecast experiments with early May initial conditions are carried out for the two years using an enhanced version of CFSv2, where the atmospheric component of the CFSv2 is coupled to the Noah Multiple-Parameterization (Noah-MP) land model. The Noah-MP has different options for ground water and evaporation control parameterizations. The differences will be presented and results will be discussed.

A Soil-Plate Based Pipeline for Assessing Cereal Root Growth in Response to Polyethylene Glycol (PEG)-Induced Water Deficit Stress

PubMed Central

Nelson, Sven K.; Oliver, Melvin J.

2017-01-01

Drought is a serious problem that causes losses in crop-yield every year, but the mechanisms underlying how roots respond to water deficit are difficult to study under controlled conditions. Methods for assaying root elongation and architecture, especially for seedlings, are commonly achieved on artificial media, such as agar, moistened filter paper, or in hydroponic systems. However, it has been demonstrated that measuring root characteristics under such conditions does not accurately mimic what is observed when plants are grown in soil. Morphological changes in root behavior occur because of differences in solute diffusion, mechanical impedance, exposure to light (in some designs), and gas exchange of roots grown under these conditions. To address such deficiencies, we developed a quantitative method for assaying seedling root lengths and germination in soil using a plate-based approach with wheat as a model crop. We also further developed the method to include defined water deficits stress levels using the osmotic properties of polyethylene glycol (PEG). Seeds were sown into soil-filled vertical plates and grown in the dark. Root length measurements were collected using digital photography through the transparent lid under green lighting to avoid effects of white light exposure on growth. Photographs were analyzed using the cross-platform ImageJ plugin, SmartRoot, which can detect root edges and partially automate root detection for extraction of lengths. This allowed for quick measurements and straightforward and accurate assessments of non-linear roots. Other measurements, such as root width or angle, can also be collected by this method. An R function was developed to collect exported root length data, process and reformat the data, and output plots depicting root/shoot growth dynamics. For water deficit experiments, seedlings were transplanted side-by-side into well-watered plates and plates containing PEG solutions to simulate precise water deficits. PMID:28785272

A Soil-Plate Based Pipeline for Assessing Cereal Root Growth in Response to Polyethylene Glycol (PEG)-Induced Water Deficit Stress.

PubMed

Nelson, Sven K; Oliver, Melvin J

2017-01-01

Drought is a serious problem that causes losses in crop-yield every year, but the mechanisms underlying how roots respond to water deficit are difficult to study under controlled conditions. Methods for assaying root elongation and architecture, especially for seedlings, are commonly achieved on artificial media, such as agar, moistened filter paper, or in hydroponic systems. However, it has been demonstrated that measuring root characteristics under such conditions does not accurately mimic what is observed when plants are grown in soil. Morphological changes in root behavior occur because of differences in solute diffusion, mechanical impedance, exposure to light (in some designs), and gas exchange of roots grown under these conditions. To address such deficiencies, we developed a quantitative method for assaying seedling root lengths and germination in soil using a plate-based approach with wheat as a model crop. We also further developed the method to include defined water deficits stress levels using the osmotic properties of polyethylene glycol (PEG). Seeds were sown into soil-filled vertical plates and grown in the dark. Root length measurements were collected using digital photography through the transparent lid under green lighting to avoid effects of white light exposure on growth. Photographs were analyzed using the cross-platform ImageJ plugin, SmartRoot, which can detect root edges and partially automate root detection for extraction of lengths. This allowed for quick measurements and straightforward and accurate assessments of non-linear roots. Other measurements, such as root width or angle, can also be collected by this method. An R function was developed to collect exported root length data, process and reformat the data, and output plots depicting root/shoot growth dynamics. For water deficit experiments, seedlings were transplanted side-by-side into well-watered plates and plates containing PEG solutions to simulate precise water deficits.

A technique for estimating seed production of common moist soil plants

USGS Publications Warehouse

Laubhan, Murray K.

1992-01-01

Seeds of native herbaceous vegetation adapted to germination in hydric soils (i.e., moist-soil plants) provide waterfowl with nutritional resources including essential amino acids, vitamins, and minerals that occur only in small amounts or are absent in other foods. These elements are essential for waterfowl to successfully complete aspects of the annual cycle such as molt and reproduction. Moist-soil vegetation also has the advantages of consistent production of foods across years with varying water availability, low management costs, high tolerance to diverse environmental conditions, and low deterioration rates of seeds after flooding. The amount of seed produced differs among plant species and varies annually depending on environmental conditions and management practices. Further, many moist-soil impoundments contain diverse vegetation, and seed production by a particular plant species usually is not uniform across an entire unit. Consequently, estimating total seed production within an impoundment is extremely difficult. The chemical composition of seeds also varies among plant species. For example, beggartick seeds contain high amounts of protein but only an intermediate amount of minerals. In contrast, barnyardgrass is a good source of minerals but is low in protein. Because of these differences, it is necessary to know the amount of seed produced by each plant species if the nutritional resources provided in an impoundment are to be estimated. The following technique for estimating seed production takes into account the variation resulting from different environmental conditions and management practices as well as differences in the amount of seed produced by various plant species. The technique was developed to provide resource managers with the ability to make quick and reliable estimates of seed production. Although on-site information must be collected, the amount of field time required is small (i.e., about 1 min per sample); sampling normally is accomplished on an area within a few days. Estimates of seed production derived with this technique are used, in combination with other available information, to determine the potential number of waterfowl use-days available and to evaluate the effects of various management strategies on a particular site.

Application of IEM model on soil moisture and surface roughness estimation

NASA Technical Reports Server (NTRS)

Shi, Jiancheng; Wang, J. R.; Oneill, P. E.; Hsu, A. Y.; Engman, E. T.

1995-01-01

Monitoring spatial and temporal changes of soil moisture are of importance to hydrology, meteorology, and agriculture. This paper reports a result on study of using L-band SAR imagery to estimate soil moisture and surface roughness for bare fields. Due to limitations of the Small Perturbation Model, it is difficult to apply this model on estimation of soil moisture and surface roughness directly. In this study, we show a simplified model derived from the Integral Equation Model for estimation of soil moisture and surface roughness. We show a test of this model using JPL L-band AIRSAR data.

SPECTROSCOPIC SPECIATION AND QUANTIFICATION OF LEAD IN PHOSPHATE AMENDED SOILS

EPA Science Inventory

The immobilization of Pb in contaminated soils as pyromorphite [Pb₅(PO₄)₃CI, OH, F] through the addition of various phosphate amendments has gained much attention in the remediation community. However, it is difficult to fully determine the specia...

Using the Surface Temperature-Albedo Space to Separate Regional Soil and Vegetation Temperatures from ASTER Data

USDA-ARS?s Scientific Manuscript database

Soil and vegetation component temperatures in non-isothermal pixels encapsulate more physical meaning and are more applicable than composite temperatures. The component temperatures however are difficult to be obtained from thermal infrared (TIR) remote sensing data provided by single view angle obs...

Forest vegetation of eastern Washington and northern Idaho

Treesearch

R. Daubenmire; Jean B. Daubenmire

1968-01-01

The forest vegetation of the northern Rocky Mountains is potentially a rather simple mosaic determined by macroclimate, microclimate, soil fertility and soil drainage. In actuality, however, the vegetation consists mainly of a wide variety of intergrading, disturbance-induced communities that are difficult to treat except as developmental series related to...

Dissecting the Hydrobiogeochemical Box

NASA Astrophysics Data System (ADS)

Wang, Y.; Alves Meira Neto, A.; Sengupta, A.; Root, R. A.; Dontsova, K.; Troch, P. A. A.; Chorover, J.

2015-12-01

Soil genesis is a coupled hydrologic and biogeochemical process that involves the interaction of weathering rock surfaces and water. Due to strong nonlinear coupling, it is extremely difficult to predict biogeochemical changes from hydrological modeling in natural field systems. A fully controlled and monitored system with known initial conditions could be utilized to isolate variables and simplify these natural processes. To investigate the initial weathering of host rock to soil, we employed a 10° sloping soil lysimeter containing one cubic meter of crushed and homogenized basaltic rock. A major experiment of the Periodic Tracer Hierarchy (PERTH) method (Harman and Kim, 2014) coupled with its bonus experiment were performed in the past two years. These experimental applications successfully described the transit-time distribution (TTD) of a tracer-enriched water breakthrough curve in this unique hydrological system (Harman, 2015). With intensive irrigation and high volume of water storage throughout the experiments, rapid biological changes have been observed on the soil surface, such as algal and grass growth. These observations imply that geochemical hotspots may be established within the soil lysimeter. To understand the detailed 2D spatial distribution of biogeochemical changes, 100 selected and undisturbed soil blocks, among a total 1000 sub-gridded equal sized, are tested with several geochemical tools. Each selected soil block was subjected to elemental analysis by pXRF to determine if elemental migration is detectable in the dynamic proto-soil development. Synchrotron XRD quantification with Reitveld refinement will follow to clarify mineralogical transformations in the soil blocks. The combined techniques aim to confirm the development of geochemical hotspots; and link these findings with previous hydrological findings from the PERTH experiment as well as other hydrological modeling, such as conducted with Hydrus and CATHY. This work provides insight to the detailed correlations between hydrological and biogeochemical processes during incipient soil formation, as well as aiding the development of advanced tools and methods to study complex Earth-system dynamics.

Testing the Hole-in-the-Pipe Model of nitric and nitrous oxide emissions from soils using the TRAGNET Database

NASA Astrophysics Data System (ADS)

Davidson, Eric A.; Verchot, Louis V.

2000-12-01

Because several soil properties and processes affect emissions of nitric oxide (NO) and nitrous oxide (N2O) from soils, it has been difficult to develop effective and robust algorithms to predict emissions of these gases in biogeochemical models. The conceptual "hole-in-the-pipe" (HIP) model has been used effectively to interpret results of numerous studies, but the ranges of climatic conditions and soil properties are often relatively narrow for each individual study. The Trace Gas Network (TRAGNET) database offers a unique opportunity to test the validity of one manifestation of the HIP model across a broad range of sites, including temperate and tropical climates, grasslands and forests, and native vegetation and agricultural crops. The logarithm of the sum of NO + N2O emissions was positively and significantly correlated with the logarithm of the sum of extractable soil NH4+ + NO3-. The logarithm of the ratio of NO:N2O emissions was negatively and significantly correlated with water-filled pore space (WFPS). These analyses confirm the applicability of the HIP model concept, that indices of soil N availability correlate with the sum of NO+N2O emissions, while soil water content is a strong and robust controller of the ratio of NO:N2O emissions. However, these parameterizations have only broad-brush accuracy because of unaccounted variation among studies in the soil depths where gas production occurs, where soil N and water are measured, and other factors. Although accurate predictions at individual sites may still require site-specific parameterization of these empirical functions, the parameterizations presented here, particularly the one for WFPS, may be appropriate for global biogeochemical modeling. Moreover, this integration of data sets demonstrates the broad ranging applicability of the HIP conceptual approach for understanding soil emissions of NO and N2O.

Microbial imprint on soil-atmosphere H2, COS, and CO2 fluxes

NASA Astrophysics Data System (ADS)

Meredith, L. K.; Commane, R.; Munger, J. W.; Wofsy, S. C.; Prinn, R. G.

2013-12-01

Microorganisms drive large trace gas fluxes between soil and atmosphere, but the signal can be difficult to detect and quantify in the presence of stronger exchange processes in an ecosystem. Partitioning methods are often needed to estimate trace gas budgets and to develop process-based models to explore the sensitivity of microbe-mediated fluxes. In this study, we test the performance of trace gases with predominantly microbe-mediated soil fluxes as a metric of the soil microbial uptake activity of other trace gases. Using simultaneous, collocated measurements at Harvard Forest, we consider three trace gases with microbe-mediated soil fluxes of various importance relative to their other (mainly plant-mediated) ecosystem fluxes: molecular hydrogen (H2), carbonyl sulfide (COS), and carbon dioxide (CO2). These gases probe different aspects of the soil trace-gas microbiology. Soil H2 uptake is a redox reaction driving the energy metabolism of a portion of the microbial community, while soil CO2 respiration is a partial proxy for the overall soil microbial metabolism. In comparison, very little is understood about the microbiological and environmental drivers of soil COS uptake and emissions. In this study, we find that H2, COS, and CO2 soil uptake rates are often correlated, but the relative soil uptake between gases is not constant, and is influenced by seasonality and local environmental conditions. We also consider how differences in the microbial communities and pathways involved in the soil fluxes may explain differences in the observations. Our results are important for informing previous studies using tracer approaches. For example, H2 has been used to estimate COS soil uptake, which must be accounted for to use COS as a carbon cycle tracer. Furthermore, the global distribution of H2 deposition velocity has been inferred from net primary productivity (CO2). Given that insufficient measurement frequency and spatial distribution exists to partition global net ecosystem fluxes of many climate-relevant trace gases, insight into the use of certain trace gases to estimate rates of more general biogeochemical processes is useful.

Use of fog water to the initial establishment of tree species under conditions of barren Lomas in the Quebrada Topará, Chincha-Perú

NASA Astrophysics Data System (ADS)

Vargas, A.; Cabrera, R.; Bederski, K.; Orellana, A.

2010-07-01

The Quebrada Topara is located in the Peruvian coastal desert (13012'L.S, 76009'L.W.) and is influenced by the fog during the winter months, these conditions of high humidity allows its use to achieve the establishment of a permanent vegetation cover Huaquina hill, which is representative at the place of study. Uncounted fog water can be captured and used for irrigation of plants. Also due to the absence of any tree species coverage in this region is not known which or which could have a better performance under these environmental conditions, We used to native species Caesalpinia spinosa "tara" and Schinus molle "molle" also introduced species Casuarina equisetifolia "Casuarina", as these could have a better adaptation. Soil analysis determined a high salinity and nitrogen poverty, preventing water infiltration into the soil and is not used by the plant so that the saline soil difficult to establish plants. This research can be considered an exploratory phase, the objectives were: to determine the potential for fog water harvesting to capture in the study area, to assess for 20 months the initial performance of the species tara, molle and casuarina, and profit incorporation in the final sowing of organic matter and soil amendments to facilitate a better development of plants. 3 standard fog collector (SFC) proposed by Schemenauer and Cereceda (1993) were installed and we evaluated the capture water during 31 months, from June 2007 to December 2009, finding much water collected in the winter months, the average annual in the 3 SFC was similar (1.1, 1.2 and 1.1 L m -2 day-1) which allows us to plan according to necessary the best way to harness and store water to supply the plants. It was found that native species, tara and molle were more adaptable to extreme conditions of the place that introduced casuarina species. The tara does grow faster in height and stem diameter, also achieves a good coverage to intercept fog water itself making it more viable and capable of being established. It provides statistics that indicate the beneficial effect of improving soil with organic matter and amendments in the survival rate and vegetative growth of tree species.

Estimating the impact of seawater on the production of soil water-extractable organic carbon during coastal erosion.

PubMed

Dou, Fugen; Ping, Chien-Lu; Guo, Laodong; Jorgenson, Torre

2008-01-01

The production of water-extractable organic carbon (WEOC) during arctic coastal erosion and permafrost degradation may contribute significantly to C fluxes under warming conditions, but it remains difficult to quantify. A tundra soil collected near Barrow, AK, was selected to evaluate the effects of soil pretreatments (oven drying vs. freeze drying) as well as extraction solutions (pure water vs. seawater) on WEOC yields. Both oven drying and freeze drying significantly increased WEOC release compared with the original moist soil samples; dried samples released, on average, 18% more WEOC than did original moist samples. Similar results were observed for the production of low-molecular-weight dissolved organic C. However, extractable OC released from different soil horizons exhibited differences in specific UV absorption, suggesting differences in WEOC quality. Furthermore, extractable OC yields were significantly less in samples extracted with seawater compared with those extracted with pure water, likely due to the effects of major ions on extractable OC flocculation. Compared with samples from the active horizons, upper permafrost samples released more WEOC, suggesting that continuously frozen samples were more sensitive than samples that had experienced more drying-wetting cycles in nature. Specific UV absorption of seawater-extracted OC was significantly lower than that of OC extracted using pure water, suggesting more aromatic or humic substances were flocculated during seawater extraction. Our results suggest that overestimation of total terrestrial WEOC input to the Arctic Ocean during coastal erosion could occur if estimations were based on WEOC extracted from dried soil samples using pure water.

Modifying the 'pulse-reserve' paradigm for deserts of North America: precipitation pulses, soil water, and plant responses.

PubMed

Reynolds, James F; Kemp, Paul R; Ogle, Kiona; Fernández, Roberto J

2004-10-01

The 'pulse-reserve' conceptual model--arguably one of the most-cited paradigms in aridland ecology--depicts a simple, direct relationship between rainfall, which triggers pulses of plant growth, and reserves of carbon and energy. While the heuristics of 'pulses', 'triggers' and 'reserves' are intuitive and thus appealing, the value of the paradigm is limited, both as a conceptual model of how pulsed water inputs are translated into primary production and as a framework for developing quantitative models. To overcome these limitations, we propose a revision of the pulse-reserve model that emphasizes the following: (1) what explicitly constitutes a biologically significant 'rainfall pulse', (2) how do rainfall pulses translate into usable 'soil moisture pulses', and (3) how are soil moisture pulses differentially utilized by various plant functional types (FTs) in terms of growth? We explore these questions using the patch arid lands simulation (PALS) model for sites in the Mojave, Sonoran, and Chihuahuan deserts of North America. Our analyses indicate that rainfall variability is best understood in terms of sequences of rainfall events that produce biologically-significant 'pulses' of soil moisture recharge, as opposed to individual rain events. In the desert regions investigated, biologically significant pulses of soil moisture occur in either winter (October-March) or summer (July-September), as determined by the period of activity of the plant FTs. Nevertheless, it is difficult to make generalizations regarding specific growth responses to moisture pulses, because of the strong effects of and interactions between precipitation, antecedent soil moisture, and plant FT responses, all of which vary among deserts and seasons. Our results further suggest that, in most soil types and in most seasons, there is little separation of soil water with depth. Thus, coexistence of plant FTs in a single patch as examined in this PALS study is likely to be fostered by factors that promote: (1) separation of water use over time (seasonal differences in growth), (2) relative differences in the utilization of water in the upper soil layers, or (3) separation in the responses of plant FTs as a function of preceding conditions, i.e., the physiological and morphological readiness of the plant for water-uptake and growth. Finally, the high seasonal and annual variability in soil water recharge and plant growth, which result from the complex interactions that occur as a result of rainfall variability, antecedent soil moisture conditions, nutrient availability, and plant FT composition and cover, call into question the use of simplified vegetation models in forecasting potential impacts of climate change in the arid zones in North America.

Engineered polymeric nanoparticles for soil remediation.

PubMed

Tungittiplakorn, Warapong; Lion, Leonard W; Cohen, Claude; Kim, Ju-Young

2004-03-01

Hydrophobic organic groundwater contaminants, such as polynuclear aromatic hydrocarbons (PAHs), sorb strongly to soils and are difficult to remove. We report here on the synthesis of amphiphilic polyurethane (APU) nanoparticles for use in remediation of soil contaminated with PAHs. The particles are made of polyurethane acrylate anionomer (UAA) or poly(ethylene glycol)-modified urethane acrylate (PMUA) precursor chains that can be emulsified and cross-linked in water. The resulting particles are of colloidal size (17-97 nm as measured by dynamic light scattering). APU particles have the ability to enhance PAH desorption and transport in a manner comparable to that of surfactant micelles, but unlike the surface-active components of micelles, the individual cross-linked precursor chains in APU particles are not free to sorb to the soil surface. Thus, the APU particles are stable independent of their concentration in the aqueous phase. In this paper we show that APU particles can be engineered to achieve desired properties. Our experimental results show that the APU particles can be designed to have hydrophobic interior regions that confer a high affinity for phenanthrene (PHEN) and hydrophilic surfaces that promote particle mobility in soil. The affinity of APU particles for contaminants such as PHEN can be controlled by changing the size of the hydrophobic segment used in the chain synthesis. The mobility of colloidal APU suspensions in soil is controlled by the charge density or the size of the pendent water-soluble chains that reside on the particle surface. Exemplary results are provided illustrating the influence of alternative APU particle formulations with respect to their efficacy for contaminant removal. The ability to control particle properties offers the potential to produce different nanoparticles optimized for varying contaminant types and soil conditions.

Ground beetles in Mediterranean olive agroecosystems: Their significance and functional role as bioindicators (Coleoptera, Carabidae)

PubMed Central

Mazzei, Antonio; Bonacci, Teresa; Scalercio, Stefano; Iannotta, Nino; Brandmayr, Pietro

2018-01-01

The impact of agricultural practices and soil management on the communities of arthropods living in the agricultural landscape is acknowledged as a critical issue by the literature, and it needs to be better investigated to improve the ecological sustainability of agriculture. In the present study, we aimed to study how soil management affect carabid species distribution in one of the most typical agroecosystem of the Mediterranean region, i.e. the olive grove. In South Italy olive plantations feature different types of soil management, from tillage to half- or full-cover cropping. Species distribution has been examined for a total of 10,189 individuals and 62 species collected from 17 sites. Notably from our analysis we have observed that three factors (climax vegetation, soil features and soil management) explained half of the data variability. The composition of species groupings mirrors both bioclimatic conditions (climax vegetation) and soil features, especially watering, while soil management affects the species distribution, with different intensity from site to site. Eleven species have been recognized as the most abundant in the different facets of the studied olive groves and consequently designated as characteristics of the olive agroecosystem. The species traits of the sampled species have been weighted for a compelling evaluation of the effects of agricultural management on biodiversity, showing uniform traits distribution when coping with the ecological factors that characterize the different plantation facets. We have found that carabid beetles can be used as model organisms for studying the effects of agricultural practices. Our study suggests that the interaction of man-induced trasformation with the natural background of the olive agroecosystem may be difficult to disentangle, so that such complexity must be taken into account when carabid beetles are expected to provide an ecosystem service for good agricultural practices. PMID:29558493

Land and atmosphere interactions using satellite remote sensing and a coupled mesoscale/land surface model

NASA Astrophysics Data System (ADS)

Hong, Seungbum

Land and atmosphere interactions have long been recognized for playing a key role in climate and weather modeling. However their quantification has been challenging due to the complex nature of the land surface amongst various other reasons. One of the difficult parts in the quantification is the effect of vegetation which are related to land surface processes such soil moisture variation and to atmospheric conditions such as radiation. This study addresses various relational investigations among vegetation properties such as Normalized Difference Vegetation Index (NDVI), Leaf Area Index (LAI), surface temperature (TSK), and vegetation water content (VegWC) derived from satellite sensors such as Moderate Resolution Imaging Spectroradiometer (MODIS) and EOS Advanced Microwave Scanning Radiometer (AMSR-E). The study provides general information about a physiological behavior of vegetation for various environmental conditions. Second, using a coupled mesoscale/land surface model, we examined the effects of vegetation and its relationship with soil moisture on the simulated land-atmospheric interactions through the model sensitivity tests. The Weather Research and Forecasting (WRF) model was selected for this study, and the Noah land surface model (Noah LSM) implemented in the WRF model was used for the model coupled system. This coupled model was tested through two parameterization methods for vegetation fraction using MODIS data and through model initialization of soil moisture from High Resolution Land Data Assimilation System (HRLDAS). Then, this study evaluates the model improvements for each simulation method.

Using GRACE-Derived Water and Moisture Products as a Predictive Tool for Fire Response in the Contiguous United States

NASA Astrophysics Data System (ADS)

Rousseau, N. J.; Jensen, D.; Zajic, B.; Rodell, M.; Reager, J. T., II

2015-12-01

Understanding the relationship between wildfire activity and soil moisture in the United States has been difficult to assess, with limited ability to determine areas that are at high risk. This limitation is largely due to complex environmental factors at play, especially as they relate to alternating periods of wet and dry conditions, and the lack of remotely-sensed products. Recent drought conditions and accompanying low Fuel Moisture Content (FMC) have led to disastrous wildfire outbreaks causing economic loss, property damage, and environmental degradation. Thus, developing a programmed toolset to assess the relationship between soil moisture, which contributes greatly to FMC and fire severity, can establish the framework for determining overall wildfire risk. To properly evaluate these parameters, we used data assimilated from the Gravity Recovery and Climate Experiment (GRACE) and data from the Fire Program Analysis fire-occurrence database (FPA FOD) to determine the extent soil moisture affects fire activity. Through these datasets, we produced correlation and regression maps at a coarse resolution of 0.25 degrees for the contiguous United States. These fire-risk products and toolsets proved the viability of this methodology, allowing for the future incorporation of more GRACE-derived water parameters, MODIS vegetation indices, and other environmental datasets to refine the model for fire risk. Additionally, they will allow assessment to national-scale early fire management and provide responders with a predictive tool to better employ early decision-support to areas of high risk during regions' respective fire season(s).

New strategies to increase the restoration success of post-mining landscapes: the application of cyanobacteria to seed-based rehabilitation programs

NASA Astrophysics Data System (ADS)

Muñoz-Rojas, Miriam; Raúl Román Fernández, José; Roncero Ramos, Beatriz; Cantón Castilla, Yolanda

2017-04-01

Despite the large efforts and investments to dryland ecosystems restoration worldwide, land rehabilitation in these areas has very low rates of success. Most of the challenges in landscape-scale restoration come from the lack of suitable soil substrates to support plant establishment and to ultimately achieve functional ecosystems. A common practice during extractive operations such as open-cut and strip mining is the removal of the topsoil layer that is subsequently stockpiled and respread in areas targeted for restoration. This topsoil is a crucial source of seeds, nutrients, and microorganisms but is a scarce resource which challenges the success of many restoration programs. In these conditions, the use of direct seeding of key native plant species becomes critical to reinstate biodiverse vegetation communities. Alternative soil substrates such as overburden or waste materials produced in mining operations are increasingly being used as growth media in restoration. However, these soil substrates can have inadequate levels of pH or salinity for plant growth and in most cases are depleted in organic materials and nutrients. In these conditions, the establishment of native plant species can be extremely difficult with a consequent potential loss of biodiversity. Development of appropriate soil structures such as technosols can be extremely expensive and demanding in terms of time and natural resources soils and therefore new approached need to be explored. In the last years, the potential of cyanobacteria biological crust to restore soil functionality in degraded has been highlighted because of their important role in controlling soil structure, preventing soil erosion and N and C fixation. Nevertheless, many research gaps still remain in their application to restore soil functionality in seed-based restoration practices. In this study, we test the potential of cyanobacteria inoculation to restore soil functions of soil materials used in post-mine restoration. Soil substrates consisted of topsoil retrieved from previously stockpiled material, an overburden waste material commonly used in landform reconstruction due to its erosive stability and physical competency, and a mixture of both substrates. These materials were collected from an active mine site in the mining intensive Pilbara region and inoculated with a mixture of soil cyanobacteria from three nitrogen-fixing genera (Nostoc, Scytonema and Tolypothrix). Further analyses need to be undertaken but preliminary results showed that after only 4 weeks, cyanobacteria rapidly colonized the mine substrates as cyanobacteria surface cover significantly increased during the time of study.The output of this research is the first step to effectively address the reconstruction of soil substrates that can provide support to the establishment of biodiverse vegetation communities in landscape-scale seed-based mine restoration.

Multidisciplinary Investigations Regarding the Wear of Machine Tools Operating Into the Soil

NASA Astrophysics Data System (ADS)

Cardei, P.; Vladutoiu, L. C.; Gheorghe, G.; Fechete, T. L. V.; Chisiu, G.

2018-01-01

The paper presents the results obtained by the authors in investigating the problem of wear of work organs of machines working in continuous interaction with the soil. The phenomenon of the interaction of the tools of agricultural machinery for ploughing, and the soil, is a complex of phenomena, one of the most difficult to model. Among the phenomena involved in this interaction, friction and wear (of many types) are the most important. We did not take into account the chemical wear, and by the wear caused by weather conditions. Research has focused on formulating a theory that has more than a descriptive character, for it be used for application purposes. For this we used classical theoretical models, mathematical models based on the theory of continuous bodies, theory of flow of fluids around the profiles, as well as other theories, approached or not, in an attempt to solve as satisfactorily the issue of the wear, for the tools of the agricultural machines for the tillage. We also sought to highlight the fact that wear is a phenomenon on a micro and macro-scale scale, and its generating causes must ultimately be related to observable effects, on the macro-structural scale.

Impact of biotic and a-biotic parameters on structure and function of microbial communities living on sclerotia of the soil-borne pathogenic fungus Rhizoctonia solani

PubMed Central

Zachow, Christin; Grosch, Rita; Berg, Gabriele

2011-01-01

The plant pathogen Rhizoctonia solani is very difficult to control due to its persistent, long-living sclerotial structures in soil. Sclerotia are the main source of infection for Rhizoctonia diseases, which cause high yield losses on a broad host range world-wide. Little is known about micro-organisms associated with sclerotia in soil. Therefore, microbial communities of greenhouse and field incubated Rhizoctonia sclerotia were analysed by a multiphasic approach. Using microbial fingerprints performed by PCR-SSCP, sclerotia-associated bacterial communities showed a high diversity, whereas only a few fungi could be detected. Statistical analysis of fingerprints revealed the influence of soil types, incubation conditions (greenhouse, field), and incubation time (5 and 12 weeks) on the bacterial as well as fungal community. No significant differences were found for the microbial community associated with different Rhizoctonia anastomosis sub-groups (AG 1-IB and AG 1-IC). Rhizoctonia sclerotia are an interesting bio-resource: high proportions of fungal cell-wall degrading isolates as well as those with antagonistic activity towards R. solani were found. While a fraction of 28.4% of sclerotia-associated bacteria (=40 isolates) with antagonistic properties was determined, only 4.4% (=6 isolates) of the fungal isolates were antagonistic. We identified strong antagonists of the genera Bacillus, Enterobacter, Pseudomonas, and Stenotrophomonas, which can be used as biological control agents incorporated in soil or applied to Rhizoctonia host plants. PMID:26109749

Distinct respiratory responses of soils to complex organic substrate are governed predominantly by soil architecture and its microbial community.

PubMed

Fraser, F C; Todman, L C; Corstanje, R; Deeks, L K; Harris, J A; Pawlett, M; Whitmore, A P; Ritz, K

2016-12-01

Factors governing the turnover of organic matter (OM) added to soils, including substrate quality, climate, environment and biology, are well known, but their relative importance has been difficult to ascertain due to the interconnected nature of the soil system. This has made their inclusion in mechanistic models of OM turnover or nutrient cycling difficult despite the potential power of these models to unravel complex interactions. Using high temporal-resolution respirometery (6 min measurement intervals), we monitored the respiratory response of 67 soils sampled from across England and Wales over a 5 day period following the addition of a complex organic substrate (green barley powder). Four respiratory response archetypes were observed, characterised by different rates of respiration as well as different time-dependent patterns. We also found that it was possible to predict, with 95% accuracy, which type of respiratory behaviour a soil would exhibit based on certain physical and chemical soil properties combined with the size and phenotypic structure of the microbial community. Bulk density, microbial biomass carbon, water holding capacity and microbial community phenotype were identified as the four most important factors in predicting the soils' respiratory responses using a Bayesian belief network. These results show that the size and constitution of the microbial community are as important as physico-chemical properties of a soil in governing the respiratory response to OM addition. Such a combination suggests that the 'architecture' of the soil, i.e. the integration of the spatial organisation of the environment and the interactions between the communities living and functioning within the pore networks, is fundamentally important in regulating such processes.

Environmental fate of methyl bromide as a soil fumigant.

PubMed

Yates, Scott R; Gan, Jay; Papiernik, Sharon K

2003-01-01

The great variation among results of recent experiments measuring the total emission of MeBr from fields implies that many factors influence MeBr transport and transformation in the soil-water-air system and its ultimate loss from the soil surface. It has been demonstrated that variables related to application methods (e.g., injection depth, use and type of surface tarp), soil properties (e.g., water content, bulk density, soil organic matter), and climatic conditions (e.g.. air temperature, wind speed, barometric pressure) have pronounced effects on MeBr volatilization following soil injection. The following conclusions can be drawn from this experimental information. Tarping consistently, increased the residence time and concentration of MeBr residing in the soil. Prolonged retention of MeBr in the soil resulted in more extensive degradation and reduced cumulative emissions. Research indicates that the polyethylene film typically used for the surface cover is relatively permeable to MeBr and allows significant emissions compared to virtually impermeable plastic films. This effect is more pronounced during periods of high temperature. Soil type, soil water content, and bulk density are important factors affecting MeBr transport and transformation in soil, which ultimately affect volatilization. The total volatilization from a soil with high organic matter content may be drastically reduced relative to that from a low organic matter soil. Amendment of the surface soil with organic matter or nucleophilic compounds that promote increased degradation may offer another method for reducing volatilization. MeBr volatilization may also be decreased by increasing soil water content and bulk density, mainly because of the reduced gas-phase diffusion resulting from reduced soil air-filled porosity. To minimize volatilization, MeBr should be applied during periods of cool temperature, injected relatively deep in organic-rich, moist soil, and the soil surface packed and tarped immediately after the application. Depending on site-specific conditions, a new high-barrier plastic should be used. Injecting MeBr during periods of warm temperature, at a shallow depth in dry, loose soil without the use of low-permeability plastic barriers, will likely result in maximum volatilization rates and therefore should be discouraged. Before adopting any new emission reduction technology, the pest control characteristics of the new methodology should be assessed under soil and environmental conditions typical of the region to optimize efficacy while minimizing environmental contamination. There is considerable current scientific evidence indicating that eliminating MeBr use for soil fumigation may not have a significant impact on stratospheric ozone depletion. Management practices can and have been developed that essentially eliminate atmospheric emissions of MeBr and other fumigant compounds following soil application. Some scientists have suggested that there are natural buffers and various unknown sources of MeBr that make it impossible to ascertain that eliminating soil fumigation with MeBr will significantly improve stratospheric ozone levels. It is quite certain, however, that the phase-out will make it much more difficult for growers to economically provide an adequate and healthful food supply in the U.S. and elsewhere in the world. As the phase-out date approaches, there remains a great need for information about MeBr and stratospheric ozone depletion. Stratospheric ozone must be protected, but recent experiments suggest that it can be protected while still allowing MeBr to be used for soil fumigation. A new approach may be warranted in which state and federal regulations recognize that every chemical is a potential environmental contaminant, depending on the properties of the chemical and the environmental conditions prevailing following its application. Ideally, regulations should incorporate incentives to develop technology that minimizes the likelihood that a chemical becomes an environmental and/or public health problem. Rather than instituting an irrevocable ban, allowing for a suspension of chemical use until the appropriate technology is developed to control the undesirable characteristic(s) of the chemical use would provide much more flexibility to growers and may enhance environmental protection by adopting a proactive approach in which growers, chemical manufacturers, regulators, and the public can have confidence.

Diagnosing the Sensitivity of Local Land-Atmosphere Coupling via the Soil Moisture-Boundary Layer Interaction

NASA Technical Reports Server (NTRS)

Santanello, Joseph A., Jr.; Peters-Lidard, Christa D.; Kumar, Sujay V.

2011-01-01

The inherent coupled nature of earth s energy and water cycles places significant importance on the proper representation and diagnosis of land atmosphere (LA) interactions in hydrometeorological prediction models. However, the precise nature of the soil moisture precipitation relationship at the local scale is largely determined by a series of nonlinear processes and feedbacks that are difficult to quantify. To quantify the strength of the local LA coupling (LoCo), this process chain must be considered both in full and as individual components through their relationships and sensitivities. To address this, recent modeling and diagnostic studies have been extended to 1) quantify the processes governing LoCo utilizing the thermodynamic properties of mixing diagrams, and 2) diagnose the sensitivity of coupled systems, including clouds and moist processes, to perturbations in soil moisture. This work employs NASA s Land Information System (LIS) coupled to the Weather Research and Forecasting (WRF) mesoscale model and simulations performed over the U.S. Southern Great Plains. The behavior of different planetary boundary layers (PBL) and land surface scheme couplings in LIS WRF are examined in the context of the evolution of thermodynamic quantities that link the surface soil moisture condition to the PBL regime, clouds, and precipitation. Specifically, the tendency toward saturation in the PBL is quantified by the lifting condensation level (LCL) deficit and addressed as a function of time and space. The sensitivity of the LCL deficit to the soil moisture condition is indicative of the strength of LoCo, where both positive and negative feedbacks can be identified. Overall, this methodology can be applied to any model or observations and is a crucial step toward improved evaluation and quantification of LoCo within models, particularly given the advent of next-generation satellite measurements of PBL and land surface properties along with advances in data assimilation schemes.

A Simple Approach for Demonstrating Soil Water Retention and Field Capacity

ERIC Educational Resources Information Center

Howard, A.; Heitman, J. L.; Bowman, D.

2010-01-01

It is difficult to demonstrate the soil water retention relationship and related concepts because the specialized equipment required for performing these measurements is unavailable in most classrooms. This article outlines a low-cost, easily visualized method by which these concepts can be demonstrated in most any classroom. Columns (62.5 cm…

Suppression of annual Bromus tectorum by perennial Agropyon cristatum: roles of soil N availability and biological soil space

USDA-ARS?s Scientific Manuscript database

Worldwide, exotic invasive grasses have caused numerous ecosystem perturbations. Rangelands of the western United States have experienced increases in the size and frequency of wildfires largely due to invasion by the annual grass Bromus tectorum. Rehabilitation of invaded rangelands is difficult; b...

Agricultural drainage pipe detection using ground penetrating radar: Effects of antenna orientation relative to drainage pipe directional trend

USDA-ARS?s Scientific Manuscript database

Locating buried agricultural drainage pipes is a difficult problem confronting farmers and land improvement contractors, especially in the Midwest U.S., where the removal of excess soil water using subsurface drainage systems is a common farm practice. Enhancing the efficiency of soil water removal ...

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

Kolka, R., K.; Trettin, C., C.; Nelson, E., A.

Kolka, R.K., C.C. Trettin, E.A. Nelson, C.D. Barton, and D.E. Fletcher. 2002. Application of the EPA Wetland Research Program Approach to a floodplain wetland restoration assessment. J. Env. Monitoring & Restoration 1(1):37-51. Forested wetland restoration assessment is difficult because of the timeframe necessary for the development of a forest ecosystem. The development of a forested wetland ecosystem includes the recovery of hydrology, soils, vegetation, and faunal communities. To assess forested wetland restoration projects, measures need to be developed that are sensitive to early changes in community development and are predictive of future conditions. In this study we apply the EPS'smore » Wetland Research Program's (WRP) approach to assess the recovery of two thermally altered riparian wetland systems in South Carolina. In one of the altered wetland systems, approximately 75% of the wetland was planted with bottomland tree seedlings in an effort to hasten recovery. Individual studies addressing hydrology, soils, vegetation, and faunal communities indicate variable recovery responses.« less

Basin Wide Erosion and Soil Production Rates of a High Altitude Plateau in the Korean Peninsula Considered as an Uplifted Paleo Erosional Surface: Implications for Its Development Process and the Tectonics

NASA Astrophysics Data System (ADS)

Byun, J.; Seong, Y.

2012-12-01

The development process of High Altitude Plateaus (HAPs) has been a controversial issue in geomorphology. HAPs have been interpreted as uplifted erosional surfaces mainly controlled by fluvial processes. Recent studies, however, argued that the definition of the Paleo Erosional Surfaces (PESs) is ambiguous and HAPs, considered as the uplifted PESs, could be formed under various local lithologic, tectonic and climatic conditions. But these suggestions were severely limited by the lack of quantitative data in the field. Here, we investigate this issue of the development process of HAPs through estimating both basin wide erosion rates and soil production rates of the Daegwanryeong area in the Korean Peninsula (KP), where a HAP with low-relief hilly landscape is found. Study area has been known as a typical one of PESs in the KP, which have been uplifted since the early Miocene. Particularly deeply weathered saprolites, easily found in the study area, have also been believed to be resulted from the Tertiary deep weathering under higher temperature at the paleo sea level. First, analysis of 10Be in saprolite from the base of the soil column, except one under no soil mantle, shows that soil production rates decline linearly with increasing soil depth. These data provide a soil production function with a maximum soil production rate of 70.6m/m.y. under 24cm of soil and a minimum of 22m/m.y. under 75cm of soil. Accordingly it means that the interface between soil and saprolite have gone down maximum 141.2 m since the Quaternary. Thus it suggests that the saprolites are the results under current local climatic and geomorphic conditions rather than the relict of the Tertiary deep weathering. Second, measurements of 10Be in alluvial sediments show that the average erosion rate (70.7m/m.y.) of the study area is close to the maximum soil production rate, thus basin wide erosion rates of the study area are controlled by the current soil production rates. It means that about 1,400m has been eroded off since the early Miocene, when uplift of the KP seems to begin. Consequently it is difficult to think the HAP of the study area as the PES as well as one, which has been eroded keeping the original form of the PES. Furthermore, the erosion rates are lower than the uplift rates during the late Quaternary (about 300m/m.y.), but similar to the uplift rates before the early Miocene (about 100m/m.y.). Therefore, it suggests that the HAP of the study area has been uplifted since the early Miocene, but has not approached the steady state with the neotectonics of the KP. In summary, we suggest that the HAP of the study area is the result of the geomorphic process under current climatic and geomorphic condition rather than the relict of the PES.

Litter decay controlled by temperature, not soil properties, affecting future soil carbon.

PubMed

Gregorich, Edward G; Janzen, Henry; Ellert, Benjamin H; Helgason, Bobbi L; Qian, Budong; Zebarth, Bernie J; Angers, Denis A; Beyaert, Ronald P; Drury, Craig F; Duguid, Scott D; May, William E; McConkey, Brian G; Dyck, Miles F

2017-04-01

Widespread global changes, including rising atmospheric CO 2 concentrations, climate warming and loss of biodiversity, are predicted for this century; all of these will affect terrestrial ecosystem processes like plant litter decomposition. Conversely, increased plant litter decomposition can have potential carbon-cycle feedbacks on atmospheric CO 2 levels, climate warming and biodiversity. But predicting litter decomposition is difficult because of many interacting factors related to the chemical, physical and biological properties of soil, as well as to climate and agricultural management practices. We applied 13 C-labelled plant litter to soil at ten sites spanning a 3500-km transect across the agricultural regions of Canada and measured its decomposition over five years. Despite large differences in soil type and climatic conditions, we found that the kinetics of litter decomposition were similar once the effect of temperature had been removed, indicating no measurable effect of soil properties. A two-pool exponential decay model expressing undecomposed carbon simply as a function of thermal time accurately described kinetics of decomposition. (R 2  = 0.94; RMSE = 0.0508). Soil properties such as texture, cation exchange capacity, pH and moisture, although very different among sites, had minimal discernible influence on decomposition kinetics. Using this kinetic model under different climate change scenarios, we projected that the time required to decompose 50% of the litter (i.e. the labile fractions) would be reduced by 1-4 months, whereas time required to decompose 90% of the litter (including recalcitrant fractions) would be reduced by 1 year in cooler sites to as much as 2 years in warmer sites. These findings confirm quantitatively the sensitivity of litter decomposition to temperature increases and demonstrate how climate change may constrain future soil carbon storage, an effect apparently not influenced by soil properties. © 2016 Her Majesty the Queen in Right of Canada. Global Change Biology. Published by 2016 John Wiley & Sons Ltd.

Revealing structure and assembly cues for Arabidopsis root-inhabiting bacterial microbiota.

PubMed

Bulgarelli, Davide; Rott, Matthias; Schlaeppi, Klaus; Ver Loren van Themaat, Emiel; Ahmadinejad, Nahal; Assenza, Federica; Rauf, Philipp; Huettel, Bruno; Reinhardt, Richard; Schmelzer, Elmon; Peplies, Joerg; Gloeckner, Frank Oliver; Amann, Rudolf; Eickhorst, Thilo; Schulze-Lefert, Paul

2012-08-02

The plant root defines the interface between a multicellular eukaryote and soil, one of the richest microbial ecosystems on Earth. Notably, soil bacteria are able to multiply inside roots as benign endophytes and modulate plant growth and development, with implications ranging from enhanced crop productivity to phytoremediation. Endophytic colonization represents an apparent paradox of plant innate immunity because plant cells can detect an array of microbe-associated molecular patterns (also known as MAMPs) to initiate immune responses to terminate microbial multiplication. Several studies attempted to describe the structure of bacterial root endophytes; however, different sampling protocols and low-resolution profiling methods make it difficult to infer general principles. Here we describe methodology to characterize and compare soil- and root-inhabiting bacterial communities, which reveals not only a function for metabolically active plant cells but also for inert cell-wall features in the selection of soil bacteria for host colonization. We show that the roots of Arabidopsis thaliana, grown in different natural soils under controlled environmental conditions, are preferentially colonized by Proteobacteria, Bacteroidetes and Actinobacteria, and each bacterial phylum is represented by a dominating class or family. Soil type defines the composition of root-inhabiting bacterial communities and host genotype determines their ribotype profiles to a limited extent. The identification of soil-type-specific members within the root-inhabiting assemblies supports our conclusion that these represent soil-derived root endophytes. Surprisingly, plant cell-wall features of other tested plant species seem to provide a sufficient cue for the assembly of approximately 40% of the Arabidopsis bacterial root-inhabiting microbiota, with a bias for Betaproteobacteria. Thus, this root sub-community may not be Arabidopsis-specific but saprophytic bacteria that would naturally be found on any plant root or plant debris in the tested soils. By contrast, colonization of Arabidopsis roots by members of the Actinobacteria depends on other cues from metabolically active host cells.

Techniques for Measurement of Nitrate Movement in Soils

NASA Technical Reports Server (NTRS)

Broadbent, F. E.

1971-01-01

Contamination of surface and ground waters with nitrate usually involves leaching through soil of nitrate produced by mineralization of soil organic matter, decomposition of animal wastes or plant residues, or derived from fertilizers. Nitrate concentrations in the soil solution may be measured by several chemical procedures or by the nitrate electrode. since nitrate is produced throughout the soil mass it is difficult to identify a source of nitrate contamination by conventional means. This problem can be solved by use of N-15-enriched or N-15-depleted materials as tracers. The latter is particularly attractive because of the negligible possibility of the tracer hazardous to health.

Testing the suitability of some endemic and exotic species for eco-engineering applications to control slope processes

NASA Astrophysics Data System (ADS)

Cammeraat, L. H.; van Beek, L. P. H.

2009-04-01

Eco-engineering is a growing, but still under rated field at the interface of landscape ecology and civil engineering. Although the principles are already known for a long period, the attention for green remediation techniques is increasing, especially in slope stabilizing projects as well as in soil erosion protection. This study discusses tests carried out on the effectiveness of plants to stabilize steep slopes. Four different treatments were compared: A naturally vegetated terrace slope (Brachyopodum retusem grass dominated), a slope completely stripped from vegetation, a slope planted with Arrundo donax (Spanish cane) and a slope with vetiver grass (Vetiver zizanioides), the last one being an often successfully applied, but exotic tropical species for erosion and slope protection. The tests were carried out in double, on unarmored steep bench terrace slopes (30-60° slope angle) on homogeneous marl in E Spain (Rio Serpis Basin). Vegetation was planted in summer and irrigated during the first summer period. Precipitation and soil temperature were measured and runoff and erosion was measured at the installed ‘Gerlach troughs'. Soil physical properties were determined such as bulk density and shear strength. The uprooting resistance of the vetiver grass was also determined as well as root density, root depth and other root parameters. Above ground plant characteristic such as plant height and base diameter were also measured. Results showed that within one year the bare slope was completely covered again with natural Brachiopodum grass dominated vegetation and that the planted vetiver and Spanish cane vegetation seemed to develop successfully. However, investigations showed that especially the roots of the vetiver grasses were not as well and deeply developed as could be expected from literature, although their surface cover and above ground biomass were good. All tested species worked well with respect to retaining soil material under overland flow conditions including the vetiver grass slopes. In the second spring after the start of the experiment however, a large rainfall event occurred and one of the test slopes planted with vetiver grass, slumped downwards over a slide plane at 30-40 cm depth, whereas the other vetiver slope remained in position. The other test slopes did not show any downward movement or erosion phenomena. The disappointing effectiveness of vetiver might be attributed to 1) hot and dry summer conditions when root growth is reduced or stops, to 2) low winter temperature conditions, which also hampers biomass production or creating frost damage, 3) the relative dense subsoil, which is difficult to penetrate by roots. Although Spanish cane showed good effectiveness, it spreads very fast and uncontrolled to other places, and is then difficult to remove. The conclusion can be made that despite the wide application of vetiver, also in the Mediterranean, it is not suitable for Mediterranean areas with either too dry conditions or that are too cold in winter. Spanish cane is also not suitable for its uncontrolled expansion. The remaining conclusion is that endemic species that are adapted to the local conditions are more favorable for application in eco-engineering applications, given that the species selected have potential for capturing sediment and increasing infiltration under overland flow conditions, or have well developed deep root systems that increase slope stability.

[Simulation of effects of soil properties and plants on soil water-salt movement with reclaimed water irrigation by ENVIRO-GRO model].

PubMed

Lü, Si-Dan; Chen, Wei-Ping; Wang, Mei-E

2012-12-01

In order to promote safe irrigation with reclaimed water and prevent soil salinisation, the dynamic transport of salts in urban soils of Beijing under irrigation of reclaimed water was simulated by ENVIRO-GRO model in this study. The accumulation trends and profile distribution of soil salinity were predicted. Simultaneously, the effects of different soil properties and plants on soil water-salt movement and salt accumulation were investigated. Results indicated that soil salinity in the profiles reached uniform equilibrium conditions by repeated simulation, with different initial soil salinity. Under the conditions of loam and clay loam soil, salinity in the profiles increased over time until reaching equilibrium conditions, while under the condition of sandy loam soil, salinity in the profiles decreased over time until reaching equilibrium conditions. The saturated soil salinity (EC(e)) under equilibrium conditions followed an order of sandy loam < loam < clay loam. Salt accumulations in Japan euonymus and Chinese pine were less than that in Blue grass. The temporal and spatial distributions of soil salinity were also different in these three types of plants. In addition, the growth of the plants was not influenced by soil salinity (except clay loam), but mild soil salinization occurred under all conditions (except sandy loam).

Polymer tensiometers in a saline environment.

NASA Astrophysics Data System (ADS)

van der Ploeg, Martine; Gooren, H. P. A.; Bakker, G.; Russell, W.; Hoogendam, C. W.; Huiskes, C.; Shouse, P.; de Rooij, G. H.

2010-05-01

It is estimated that 20% of all cultivated land and nearly half of the irrigated land is salt-affected, which pose major economic and environmental problems. Salinity may be the result of two processes; dryland and irrigation salinity. Dryland salinity is caused by a rise in the groundwater table, which occurs as a result of the replacement of deep-rooted, perennial native vegetation by shallow-rooted annual species meant for production. Irrigation salinity may occur as a result of poor water quality, poor drainage, or inefficient use of water. Consequently, new strategies to enhance crop yield stability on saline soils represent a major research priority (Botella et al. 2005). At the same time, native vegetation is capable of thriving under saline and/or dry conditions. The plant physiology of such vegetation has been investigated thoroughly, but the relation with in situ soil properties (soil moisture and salinity) may be more difficult to unravel as soil moisture sensors are less sensitive in dry soil, and the signal of most soil moisture content sensors is strongly attenuated by soil salinity. Recently, polymer tensiometer were developed that are able to measure matric potentials (closely related to a soil's moisture status) in dry soils. Polymer tensiometers consist of a solid ceramic, a stainless steel cup and a pressure transducer. The ceramic consist of a support layer and a membrane with 2 nm pore-size to prevent polymer leakage. Between the ceramic membrane and the pressure transducer a tiny chamber is located, which contains the polymer solution. The polymer's osmotic potential strongly reduces the total water potential inside the polymer tensiometer, which causes build-up of osmotic pressure. Polymer tensiometers would thus be an ideal instrument to measure in dry soil, if the polymer inside the tensiometer is not affected by the salts in the soil solution. We will address some key issues regarding the use of POTs in saline environments by showing results from a field experiment conducted in a very saline soil. This research was funded by the Dutch Technology Foundation (STW).

Effect of soil and cover conditions on soil-water relationships

Treesearch

George R., Jr. Trimble; Charles E. Hale; H. Spencer Potter

1951-01-01

People who make flood-control surveys for the U.S. Department of Agriculture are concerned with the physical condition of the soils in the watersheds. The condition of the soil determines how fast water moves into and through the soil, and how much water is held in storage. The condition of the soil has a great influence on stream flow, erosion, floods and water supply...

Soil column leaching of pesticides.

PubMed

Katagi, Toshiyuki

2013-01-01

In this review, I address the practical and theoretical aspects of pesticide soil mobility.I also address the methods used to measure mobility, and the factors that influence it, and I summarize the data that have been published on the column leaching of pesticides.Pesticides that enter the unsaturated soil profile are transported downwards by the water flux, and are adsorbed, desorbed, and/or degraded as they pass through the soil. The rate of passage of a pesticide through the soil depends on the properties of the pesticide, the properties of the soil and the prevailing environmental conditions.Because large amounts of many different pesticides are used around the world, they and their degradates may sometimes contaminate groundwater at unacceptable levels.It is for this reason that assessing the transport behavior and soil mobility of pesticides before they are sold into commerce is important and is one indispensable element that regulators use to assess probable pesticide safety. Both elementary soil column leaching and sophisticated outdoor lysimeter studies are performed to measure the leaching potential for pesticides; the latter approach more reliably reflects probable field behavior, but the former is useful to initially profile a pesticide for soil mobility potential.Soil is physically heterogeneous. The structure of soil varies both vertically and laterally, and this variability affects the complex flow of water through the soil profile, making it difficult to predict with accuracy. In addition, macropores exist in soils and further add to the complexity of how water flow occurs. The degree to which soil is tilled, the density of vegetation on the surface, and the type and amounts of organic soil amendments that are added to soil further affect the movement rate of water through soil, the character of soil adsorption sites and the microbial populations that exist in the soil. Parameters that most influence the rate of pesticide mobility in soil are persistence (DT50) of the pesticide, and its sorption/desorption(Koc) characteristics. These parameters may vary for the same pesticide from geographic site-to-site and with soil depth. The interactions that normally occur between pesticides and dissolved organic matter (DOM) or WDC are yet other factors that may complicate pesticide leaching behavior.The soil mobility of pesticides is normally tested both in the laboratory and in the field. Lab studies are initially performed to give researchers a preliminary appraisal of the relative mobility of a pesticide. Later, field lysimeter studies can be performed to provide more natural leaching conditions that emulate the actual field use pattern. Lysimeter studies give the most reliable information on the leaching behavior of a pesticide under field conditions, but these studies are time-consuming and expensive and cannot be performed everywhere. It is for this reason that the laboratory soil column leaching approach is commonly utilized to profile the mobility of a pesticide,and appraise how it behaves in different soils, and relative to other pesticides.Because the soil structure is chemically and physically heterogenous, different pesticide tests may produce variable DT50 and Koc values; therefore, initial pesticide mobility testing is undertaken in homogeneously packed columns that contain two or more soils and are eluted at constant flow rates. Such studies are done in duplicate and utilize a conservative tracer element. By fitting an appropriate mathematical model to the breakthrough curve of the conservative tracer selected,researchers determine key mobility parameters, such as pore water velocity, the column-specific dispersion coefficient, and the contribution of non equilibrium transport processes. Such parameters form the basis for estimating the probable transport and degradation rates that will be characteristic of the tested pesticide. Researchers also examine how a pesticide interacts with soil DOM and WDC, and what contribution from facilitated transport to mobility is made as a result of the effects of pH and ionic strength. Other methods are used to test how pesticides may interact with soil components to change mobility. Spectroscopic approaches are used to analyze the nature of soil pesticide complexes. These may provide insight into the mechanism by which interactions occur. Other studies may be performed to determine the effect of agricultural practices (e.g., tillage) on pesticide leaching under controlled conditions using intact soil cores from the field. When preferential flow is suspected to occur, dye staining is used to examine the contribution of macropores to pesticide transport. These methods and others are addressed in the text of this review.

Logging debris matters: better soil, fewer invasive plants

Treesearch

John Kirkland; Timoth B. Harrington; David H. Peter; Robert A. Slesak; Stephen H. Schoenholtz

2012-01-01

The logging debris that remains after timber harvest traditionally has been seen as a nuisance. It can make subsequent tree planting more difficult and become fuel for wildfire. It is commonly piled, burned, or taken off site. Logging debris, however, contains significant amounts of carbon and nitrogen—elements critical to soil productivity. Its physical presence in...

Emerging technologies for removing nonpoint phosphorus from surface water and groundwater: introduction

USDA-ARS?s Scientific Manuscript database

The long-term application of phosphorus (P) to agricultural lands has led to P accumulation in soils around the world. The build-up of soil P, also known as legacy P, poses a continued risk to ground and surface water quality that may be difficult to mitigate using traditional conservation and nutri...

An undergraduate student project to improve mechanical control of perenial nutsedges with a peanut digger in organic crop production

USDA-ARS?s Scientific Manuscript database

Perennial nutsedges are difficult to control in organic crop production systems. Tubers are generally confined to the upper portions of the soil profile and vulnerable to desiccation when on the soil surface. A peanut digger is a common implement found in the coastal plain region of the southeaste...

Climate Change Impacts on Fort Bragg, NC

DTIC Science & Technology

2013-10-15

28 5.8 Soil erosion at Fort Bragg...Rust fungi that attack the plant appear worse during wet sum- mers. Since the summers may be wetter at Fort Bragg, it may become more difficult to...drop zones. This plant requires frequent fires on its sandy soils . All of these species are associated with the Longleaf pine forests of the

Chemical, physical and biological factors affecting wood decomposition in forest soils

Treesearch

Martin Jurgensen; Peter Laks; David Reed; Anne Collins; Deborah Page-Dumroese; Douglas Crawford

2004-01-01

Organic matter (OM) decomposition is an important variable in forest productivity and determining the potential of forest soils to sequester atmospheric CO2 (Grigal and Vance 2000; Kimble et al. 2003). Studies using OM from a particular location gives site-specific decomposition information, but differences in OM type and quality make it difficult to compare results...

Using topsoil thickness to improve site-specific phosphorus and potassium management on claypan soil

USDA-ARS?s Scientific Manuscript database

Precise P and K fertilizer management on claypan soils can be difficult due to variable topsoil thickness, or depth to claypan (DTC), across landscapes, nutrient supply from subsoils, and crop removal. Therefore, a study was performed to determine if DTC could be used to improve P and K management f...

Sweetgum Response to Nitrogen Fertilization on Sites of Different Quality and Land Use History

Treesearch

D. Andrew Scott; Donald J. Kaczmarek; James A. Burger; Michael B. Kane

2002-01-01

Nitrogen (N) fertilizer management in young hardwood plantations is difficult due to our lack of understanding of the site-specific mechanisms that control tree response. Differences in landuse history and soil characteristics can alter the plant response to added N considerably. Foliage biomass, N content, N concentration, resorption, and soil N supply characteristics...

A GPR agricultural drainage pipe detection case study: Effects of antenna orientation relative to drainage pipe directional trend

USDA-ARS?s Scientific Manuscript database

Locating buried drainage pipes is a difficult task confronting farmers and land improvement contractors, especially in the Midwest U.S., where the removal of excess soil water using subsurface drainage systems is a common farm practice. Enhancing the efficiency of soil water removal on land containi...

Using repeat electrical resistivity surveys to assess heterogeneity in soil moisture dynamics under contrasting vegetation types

NASA Astrophysics Data System (ADS)

Dick, Jonathan; Tetzlaff, Doerthe; Bradford, John; Soulsby, Chris

2018-04-01

As the relationship between vegetation and soil moisture is complex and reciprocal, there is a need to understand how spatial patterns in soil moisture influence the distribution of vegetation, and how the structure of vegetation canopies and root networks regulates the partitioning of precipitation. Spatial patterns of soil moisture are often difficult to visualise as usually, soil moisture is measured at point scales, and often difficult to extrapolate. Here, we address the difficulties in collecting large amounts of spatial soil moisture data through a study combining plot- and transect-scale electrical resistivity tomography (ERT) surveys to estimate soil moisture in a 3.2 km2 upland catchment in the Scottish Highlands. The aim was to assess the spatio-temporal variability in soil moisture under Scots pine forest (Pinus sylvestris) and heather moorland shrubs (Calluna vulgaris); the two dominant vegetation types in the Scottish Highlands. The study focussed on one year of fortnightly ERT surveys. The surveyed resistivity data was inverted and Archie's law was used to calculate volumetric soil moisture by estimating parameters and comparing against field measured data. Results showed that spatial soil moisture patterns were more heterogeneous in the forest site, as were patterns of wetting and drying, which can be linked to vegetation distribution and canopy structure. The heather site showed a less heterogeneous response to wetting and drying, reflecting the more uniform vegetation cover of the shrubs. Comparing soil moisture temporal variability during growing and non-growing seasons revealed further contrasts: under the heather there was little change in soil moisture during the growing season. Greatest changes in the forest were in areas where the trees were concentrated reflecting water uptake and canopy partitioning. Such differences have implications for climate and land use changes; increased forest cover can lead to greater spatial variability, greater growing season temporal variability, and reduced levels of soil moisture, whilst projected decreasing summer precipitation may alter the feedbacks between soil moisture and vegetation water use and increase growing season soil moisture deficits.

Laboratory and numerical experiments on water and energy fluxes during freezing and thawing in the unsaturated zone

NASA Astrophysics Data System (ADS)

Holländer, Hartmut; Montasir Islam, Md.; Šimunek, Jirka

2017-04-01

Frozen soil has a major effect in many hydrologic processes, and its effects are difficult to predict. A prime example is flood forecasting during spring snowmelt within the Canadian Prairies. One key driver for the extent of flooding is the antecedent soil moisture and the possibility for water to infiltrate into frozen soils. Therefore, these situations are crucial for accurate flood prediction during every spring. The main objective of this study was to evaluate the water flow and heat transport within HYDRUS-1D version 4.16 and with Hansson's model, which is a detailed freezing/thawing module (Hansson et al., 2004), to predict the impact of frozen and partly frozen soil on infiltration. We developed a standardized data set of water flow and heat transport into (partial) frozen soil by laboratory experiments using fine sand. Temperature, soil moisture, and percolated water were observed at different freezing conditions as well as at thawing conditions. Significant variation in soil moisture was found between the top and the bottom of the soil column at the starting of the thawing period. However, with increasing temperature, the lower depth of the soil column showed higher moisture as the soil became enriched with moisture due to the release of heat by soil particles during the thawing cycle. We applied vadose zone modeling using the results from the laboratory experiments. The simulated water content by HYDRUS-1D 4.16 showed large errors compared to the observed data showing by negative Nash-Sutcliffe Efficiency. Hansson's model was not able to predict soil water fluxes due to its unstable behavior (Šimunek et al., 2016). The soil temperature profile simulated using HYDRUS-1D 4.16 was not able to predict the release of latent heat during the phase change of water that was visible in Hansson's model. Hansson's model includes the energy gain/loss due to the phase change in the amount of latent energy stored in the modified heat transport equation. However, in situations when the thermal heat gradient was large, the latent heat was not the key process, and HYDRUS-1D 4.16 was predicting better soil temperatures compared to Hansson's model. The newly developed data showed their usefulness for the evaluation and validation of the numerical models. We claim that these laboratory results will be useful for the validation of numerical models and for developing scientific knowledge to suggest potential code variations or new code development in numerical models. References: Hansson, K., J. Šimunek, M. Mizoguchi, L.-C. Lundin, and M. T. van Genuchten (2004), Water Flow and Heat Transport in Frozen Soil, Vadose Zone J, 3(2), 693-704. Šimunek, J., M. T. van Genuchten, and M. Sejna (2016), Recent developments and applications of the HYDRUS computer software packages, Vadose Zone J, 15(7).

Effect of soil type and soil management on soil physical, chemical and biological properties in commercial organic olive orchards in Southern Spain

NASA Astrophysics Data System (ADS)

Gomez, Jose Alfonso; Auxiliadora Soriano, Maria; Montes-Borrego, Miguel; Navas, Juan Antonio; Landa, Blanca B.

2014-05-01

One of the objectives of organic agriculture is to maintain and improve soil quality, while simultaneously producing an adequate yield. A key element in organic olive production is soil management, which properly implemented can optimize the use of rainfall water enhancing infiltration rates and controlling competition for soil water by weeds. There are different soil management strategies: eg. weed mowing (M), green manure with surface tillage in spring (T), or combination with animal grazing among the trees (G). That variability in soil management combined with the large variability in soil types on which organic olive trees are grown in Southern Spain, difficult the evaluation of the impact of different soil management on soil properties, and yield as well as its interpretation in terms of improvement of soil quality. This communications presents the results and analysis of soil physical, chemical and biological properties on 58 soils in Southern Spain during 2005 and 2006, and analyzed and evaluated in different studies since them. Those 58 soils were sampled in 46 certified commercial organic olive orchards with four soil types as well as 12 undisturbed areas with natural vegetation near the olive orchards. The four soil types considered were Eutric Regosol (RGeu, n= 16), Eutric Cambisol (CMeu, n=16), Calcaric Regosol (RGca, n=13 soils sampled) and Calcic Cambisol (CMcc), and the soil management systems (SMS) include were 10 light tillage (LT), 16 sheep grazing (G), 10 tillage (T), 10 mechanical mowing (M), and 12 undisturbed areas covered by natural vegetation (NV-C and NV-S). Our results indicate that soil management had a significant effect on olive yield as well as on key soil properties. Among these soil properties are physical ones, such as infiltration rate or bulk density, chemical ones, especially organic carbon concentration, and biological ones such as soil microbial respiration and bacterial community composition. Superimpose to that soil management induced variability, there was a strong interaction with soil type and climate conditions. There was also a relatively high variability within the same soil management and soil type class, indicating farm to farm variability in conditions and history of soil management. Based on this dataset two different approaches were taken to: A) evaluate the risk of soil degradation based on a limited set of soil properties, B) assess the effect of changes in SMS on soil biodiversity by using terminal restriction profiles (TRFs) derived from T-RFLP analysis of amplified 16S rDNA as. The results indicates the potential of both approaches to assess the risk of soil degradation (A) and the impact on soil biodiversity (B) upon appropriate benchmarking to characterize the interaction between soil management and soil type References Álvarez, S., Soriano, M.A., Landa, B.B., and Gómez, J.A. 2007. Soil properties in organic olive orchards compared with that in natural areas in a mountainous landscape in southern Spain. Soil Use Manage 23:404-416. Gómez, J.A., Álvarez, S., and Soriano, M.A. 2009. Development of a soil degradation assessment tool for organic olive groves in southern Spain. Catena 79:9-17. Landa, B.B., Montes-Borrego, M., Aranda, S., Soriano, M.A., Gómez, J.A., and Navas-Cortés, J.A. 2013. Soil factors involved in the diversity and structure of soil bacterial communities in commercial organic olive orchards in Southern Spain. Environmental Microbiology Reports (accepted) Soriano, M.A., Álvarez, S., Landa, B.B., and Gómez, J.A. 2013. Soil properties in organic olive orchards following different weed management in a rolling landscape of Andalusia, Spain. Renew Agr Food Syst (in press), doi:10.1017/S1742170512000361.

Shade treatment affects structure and recovery of invasive C4 African grass Echinochloa pyramidalis.

PubMed

López Rosas, Hugo; Moreno-Casasola, Patricia; Espejel González, Verónica E

2015-03-01

Echinochloa pyramidalis (Lam.) Hitchc. & Chase is an African grass with C4 photosynthesis, high biomass production, and high vegetative propagation that is tolerant to grazing and able to grow in flooded and dry conditions. Thus, it is highly invasive in tropical freshwater marshes where it is intentionally planted by ranchers to increase cattle production. This invasion is reducing plant biodiversity by increasing the invader's aerial coverage, changing wetland hydrology and causing soil physicochemical changes such as vertical accretion. Reducing the dominance of this species and increasing the density of native wetland species is a difficult, expensive, and time-consuming process. We applied a series of disturbance treatments aimed at eliminating E. pyramidalis and recovering the native vegetation of a partially invaded freshwater marsh. Treatments included physical (cutting, soil disking, transplanting individuals of the key native species Sagittaria lancifolia subsp. media (Micheli) Bogin, and/or reducing light with shade mesh) and/or chemical (spraying Round-Up™ herbicide) disturbances. At the end of the experiment, four of the five treatments used were effective in increasing the cover and biomass of native species and reducing that of E. pyramidalis. The combination of these treatments should be used to generate a proposal for the restoration of tropical wetlands invaded by non-native grasses. A promising treatment is using soil disked to soften the soil and destroy belowground structures such as roots and rhizomes. This treatment would be more promising if combined with the use of shade cloth. If it is desirable not to impact the soil or if there is not enough budget to make an effort to include active restoration disking soil, the use of shade cloth will suffice, although the recovery of native vegetation will be slower.

Shade treatment affects structure and recovery of invasive C4 African grass Echinochloa pyramidalis

PubMed Central

López Rosas, Hugo; Moreno-Casasola, Patricia; Espejel González, Verónica E

2015-01-01

Echinochloa pyramidalis (Lam.) Hitchc. & Chase is an African grass with C4 photosynthesis, high biomass production, and high vegetative propagation that is tolerant to grazing and able to grow in flooded and dry conditions. Thus, it is highly invasive in tropical freshwater marshes where it is intentionally planted by ranchers to increase cattle production. This invasion is reducing plant biodiversity by increasing the invader's aerial coverage, changing wetland hydrology and causing soil physicochemical changes such as vertical accretion. Reducing the dominance of this species and increasing the density of native wetland species is a difficult, expensive, and time-consuming process. We applied a series of disturbance treatments aimed at eliminating E. pyramidalis and recovering the native vegetation of a partially invaded freshwater marsh. Treatments included physical (cutting, soil disking, transplanting individuals of the key native species Sagittaria lancifolia subsp. media (Micheli) Bogin, and/or reducing light with shade mesh) and/or chemical (spraying Round-Up™ herbicide) disturbances. At the end of the experiment, four of the five treatments used were effective in increasing the cover and biomass of native species and reducing that of E. pyramidalis. The combination of these treatments should be used to generate a proposal for the restoration of tropical wetlands invaded by non-native grasses. A promising treatment is using soil disked to soften the soil and destroy belowground structures such as roots and rhizomes. This treatment would be more promising if combined with the use of shade cloth. If it is desirable not to impact the soil or if there is not enough budget to make an effort to include active restoration disking soil, the use of shade cloth will suffice, although the recovery of native vegetation will be slower. PMID:25859337

Environmental factors, immune changes and respiratory diseases in troops during military activities.

PubMed

Korzeniewski, Krzysztof; Nitsch-Osuch, Aneta; Chciałowski, Andrzej; Korsak, Jolanta

2013-06-01

Combat operations in contemporary theaters of war, as well as combat training, are carried out in all parts of the world, typically in a harsh environment. Specific environmental conditions, such as heat, cold, high-altitudes, desert climates, as well as chemical and biological pollution of both the atmosphere and soil, together with over-exertion, food restrictions, sleep deprivation, and psychological stress can all result in changes in the immune system and the occurrence of associated diseases. Respiratory diseases are one of the most common health problems among military personnel participating in combat training or deployed to operations in areas characterized by difficult climatic and sanitary conditions. They are, therefore, one of the main reasons for military personnel requiring ambulant and hospital treatment. The aim of the study was to discuss the influence of environmental factors and the conditions in which active duty is performed on changes in the immune system and the occurrence of respiratory tract diseases in a military environment. Copyright © 2013 Elsevier B.V. All rights reserved.

Optimization of a Sample Processing Protocol for Recovery of ...

EPA Pesticide Factsheets

Journal Article Following a release of Bacillus anthracis spores into the environment, there is a potential for lasting environmental contamination in soils. There is a need for detection protocols for B. anthracis in environmental matrices. However, identification of B. anthracis within a soil is a difficult task. Processing soil samples helps to remove debris, chemical components, and biological impurities that can interfere with microbiological detection. This study aimed to optimize a previously used indirect processing protocol, which included a series of washing and centrifugation steps.

Some Remarks on Practical Aspects of Laboratory Testing of Deep Soil Mixing Composites Achieved in Organic Soils

NASA Astrophysics Data System (ADS)

Kanty, Piotr; Rybak, Jarosław; Stefaniuk, Damian

2017-10-01

This paper presents the results of laboratory testing of organic soil-cement samples are presented in the paper. The research program continues previously reported the authors’ experiences with cement-fly ash-soil sample testing. Over 100 of compression and a dozen of tension tests have been carried out altogether. Several samples were waiting for failure test for over one year after they were formed. Several factors, like: the large amount of the tested samples, a long observation time, carrying out the tests in complex cycles of loading and the possibility of registering the loads and deformation in the axial and lateral direction - have made it possible to take into consideration numerous interdependencies, three of which have been presented in this work: the increments of compression strength, the stiffness of soil-cement in relation to strength and the tensile strength. Compressive strength, elastic modulus and tensile resistance of cubic samples were examined. Samples were mixed and stored in the laboratory conditions. Further numerical analysis in the Finite Element Method numerical code Z_Soil, were performed on the basis of laboratory test results. Computations prove that cement-based stabilization of organic soil brings serious risks (in terms of material capacity and stiffness) and Deep Soil Mixing technology should not be recommended for achieving it. The numerical analysis presented in the study below includes only one type of organic and sandy soil and several possible geometric combinations. Despite that, it clearly points to the fact that designing the DSM columns in the organic soil may be linked with a considerable risk and the settlement may reach too high values. During in situ mixing, the organic material surrounded by sand layers surely mixes with one another in certain areas. However, it has not been examined and it is difficult to assume such mixing already at the designing stage. In case of designing the DSM columns which goes through a thin layer of organic soil it is recommended to carry out each time the core drilling which checks the degree of material mixing and their strength.

Heteroaggregation of graphene oxide with minerals in aqueous phase.

PubMed

Zhao, Jian; Liu, Feifei; Wang, Zhenyu; Cao, Xuesong; Xing, Baoshan

2015-03-03

Upon release into waters, sediments, and soils, graphene oxide (GO) may interact with fine mineral particles. We investigated the heteroaggregation of GO with different minerals, including montmorillonite, kaolinite, and goethite, in aqueous phase. GO significantly enhanced the dispersion of positively charged goethite (>50%) via heteroaggregation, while there was no interaction between GO and negatively charged montmorillonite or kaolinite. Electrostatic attraction was the dominant force in the GO-goethite heteroaggregation (pH 4.0-8.5), and the dissolved Fe ions (<0.16 mg/L) from goethite were unable to destabilize GO suspension. The GO-goethite heteroaggregation was further quantitatively investigated through GO adsorption study. All adsorption isotherms of GO at different solution pH (4.0 and 6.5) followed the Linear model. The apparent intercept (1.0-6.9 mg/g) was observed for all the adsorption isotherms, indicating that this fraction of adsorbed GO was difficult to desorb from goethite (defined here as irreversible adsorption) under the tested conditions. Desorption hysteresis was observed, which could be explained by the formation of multilayered GO-goethite complex with high configurational stability. These findings are useful for understanding the interaction of GO with mineral surfaces, and potential fate and toxicity of GO under natural conditions in aquatic environments, as well as in soils and sediments.

The long-term hydrological effect of forest stands on the stability of slopes

NASA Astrophysics Data System (ADS)

Bogaard, T. A.; Meng, W.; van Beek, L. P. H.

2012-04-01

Forest is widely known to improve slope stability as a result of mechanical and hydrological effects. While the mechanics underlying the stabilizing process of root reinforcement are well understood and quantified, the influence of forest on the occurrence of critical hydrological conditions in terms of suction or pore pressure remains uncertain. Due to seasonal and inter-annual fluctuations, the stabilizing influence of evaporation and transpiration is difficult to isolate from the overall noise of the hydrological signal. More long-term effects of forest stands on soil development are highly variable and thus difficult to observe and quantify. Often these effects are ambivalent, having potentially a stabilizing or destabilizing influence on a slope under particular conditions (e.g., more structured soils leading to both rapid infiltration and drainage). Consequently, it can be postulated that forests will hydrologically influence the magnitude-frequency distribution of landsliding, not only at the stand level but also on a regional scale through the groundwater system. The overall aim of this research is to understand and quantify the stabilizing hydrological effect of forests on potentially unstable slopes. To this end, we focus on the changes in the magnitude-frequency distribution of landsliding that arise as a result of variations in evapotranspiration losses over the life cycle of stands. Temporal variations in evapotranspiration comprise first of all the interception that can account for an important amount of evaporation from a forest, and that changes with seasonal and annual variations in the interception capacity of the canopy and forest floor. Transpiration also represents an important loss that varies over the various growth stages of a forest stand. Based on a literature review of water consumption by tree species and water balance studies of forested catchments we defined the potential transpiration for different growth stages. This information we used in a spatially distributed, physical-based, dynamical model to simulate the hydrology and resulting stability for a catchment on a daily scale. The results can be used to identify end members of the hydrological influence of forests on slope stability and the typical variations in stability associated with the various growth stages. They indicate that the influence of forest stand age on the water consumption can be significant and has clear consequences for the antecedent soil moisture condition within a slope and thus on the potential for slope destabilization. The outcome should help to understand the long-term impact of vegetation on slope hydrology and define sustainable and reliable management strategies at the scale of forest stands. Keywords: slope stability, hydrology, vegetation, long-tem effect

The need for ergonomics considerations for the design and development of agricultural machinery in Thailand.

PubMed

Mamansari, D U; Salokhe, V M

1995-06-01

Agriculture plays an important role in developing countries which are mainly located in tropical regions. Agriculture is an industry with tremendous opportunities for the application of ergonomics principles. Working conditions are extremely difficult due to severe environmental conditions, long working hours, strenuous work and the use of mobile equipment. The ignorance of the majority of ergonomics principles in the design of agricultural equipment make the conditions more difficult. Thailand is one of the important suppliers of agricultural products in the world. Mechanization has expanded tremendously during the last 10 years and the number of agricultural machinery has rapidly increased. This paper looks at ergonomics principles which must be considered in the design and development of agricultural machines and equipment used in Thailand. It was identified that the common farming system in Thailand is rice-based cultivation, mostly in swampy conditions with heavy clay soil. It was also found that the most energy-consuming task in agriculture was primary cultivation. The most widely used machine is a power tiller which is suitable for the farm sizes available and can be operated easily. Most of the power tillers and other equipment were found to be locally made, with less than 5% imported. Unfortunately, there was no standardization in power tiller manufacturing which led to increasing farmers' strain. There is still a need to collect more ergonomics data of Thai farmers such as anthropometry, strength and physical work capacity for the design and development of agricultural machines and equipment used in Thailand. Different ergonomic consideration for the design and development of agricultural machinery have been suggested.

Soil-calcium depletion linked to acid rain and forest growth in the eastern United States

USGS Publications Warehouse

Lawrence, Gregory B.; Huntington, T.G.

1999-01-01

Since the discovery of acid rain in the 1970's, scientists have been concerned that deposition of acids could cause depletion of calcium in forest soils. Research in the 1980's showed that the amount of calcium in forest soils is controlled by several factors that are difficult to measure. Further research in the 1990's, including several studies by the U.S. Geological Survey, has shown that (1) calcium in forest soils has decreased at locations in the northeastern and southeastern U.S., and (2) acid rain and forest growth (uptake of calcium from the soil by roots) are both factors contributing to calcium depletion.

Neutral molecular markers support common origin of aluminium tolerance in three congeneric grass species growing in acidic soils.

PubMed

Contreras, Roberto; Figueiras, Ana M; Gallego, F Javier; Benavente, Elena; Manzaneda, Antonio J; Benito, César

2017-11-01

Aluminium (Al) toxicity is the main abiotic stress limiting plant productivity in acidic soils that are widely distributed among arable lands. Plant species differ in the level of Al resistance showing intraspecific and interspecific variation in many crop species. However, the origin of Al-tolerance is not well known. Three annual species, difficult to distinguish phenotypically and that were until recently misinterpreted as a single complex species under Brachypodium distachyon , have been recently separated into three distinct species: the diploids B. distachyon (2 n = 10) and B. stacei (2 n = 20), and B. hybridum (2 n = 30), the allotetraploid derived from the two diploid species. The aims of this work were to know the origin of Al-tolerance in acidic soil conditions within these three Brachypodium species and to develop new DNA markers for species discrimination. Two multiplex SSR-PCRs allowed to genotype a group of 94 accessions for 17 pentanucleotide microsatellite (SSRs) loci. The variability for 139 inter-microsatellite (ISSRs) markers was also examined. The genetic relationships obtained using those neutral molecular markers (SSRs and ISSRs) support that all Al-tolerant allotetraploid accessions of B. hybridum have a common origin that is related with both geographic location and acidic soils. The possibility that the adaptation to acidic soils caused the isolation of the tolerant B. hybridum populations from the others is discussed. We finally describe a new, easy, DNA barcoding method based in the upstream-intron 1 region of the ALMT1 gene, a tool that is 100 % effective to distinguish among these three Brachypodium species.

Neutral molecular markers support common origin of aluminium tolerance in three congeneric grass species growing in acidic soils

PubMed Central

Contreras, Roberto; Figueiras, Ana M; Gallego, F Javier; Benavente, Elena; Manzaneda, Antonio J

2017-01-01

Abstract Aluminium (Al) toxicity is the main abiotic stress limiting plant productivity in acidic soils that are widely distributed among arable lands. Plant species differ in the level of Al resistance showing intraspecific and interspecific variation in many crop species. However, the origin of Al-tolerance is not well known. Three annual species, difficult to distinguish phenotypically and that were until recently misinterpreted as a single complex species under Brachypodium distachyon, have been recently separated into three distinct species: the diploids B. distachyon (2n = 10) and B. stacei (2n = 20), and B. hybridum (2n = 30), the allotetraploid derived from the two diploid species. The aims of this work were to know the origin of Al-tolerance in acidic soil conditions within these three Brachypodium species and to develop new DNA markers for species discrimination. Two multiplex SSR-PCRs allowed to genotype a group of 94 accessions for 17 pentanucleotide microsatellite (SSRs) loci. The variability for 139 inter-microsatellite (ISSRs) markers was also examined. The genetic relationships obtained using those neutral molecular markers (SSRs and ISSRs) support that all Al-tolerant allotetraploid accessions of B. hybridum have a common origin that is related with both geographic location and acidic soils. The possibility that the adaptation to acidic soils caused the isolation of the tolerant B. hybridum populations from the others is discussed. We finally describe a new, easy, DNA barcoding method based in the upstream-intron 1 region of the ALMT1 gene, a tool that is 100 % effective to distinguish among these three Brachypodium species. PMID:29302302

The concurrent use of novel soil surface microclimate measurements to evaluate CO2 pulses in biocrusted interspaces in a cool desert ecosystem

USGS Publications Warehouse

Tucker, Colin; McHugh, Theresa A.; Howell, Armin; Gill, Richard; Weber, Bettina; Belnap, Jayne; Grote, Ed; Reed, Sasha C.

2017-01-01

Carbon cycling associated with biological soil crusts, which occupy interspaces between vascular plants in drylands globally, may be an important part of the coupled climate-carbon cycle of the Earth system. A major challenge to understanding CO2 fluxes in these systems is that much of the biotic and biogeochemical activity occurs in the upper few mm of the soil surface layer (i.e., the ‘mantle of fertility’), which exhibits highly dynamic and difficult to measure temperature and moisture fluctuations. Here, we report a multi-sensor approach to simultaneously measuring temperature and moisture of this biocrust surface layer (0–2 mm), and the deeper soil profile, concurrent with automated measurement of surface soil CO2effluxes. Our results illuminate robust relationships between biocrust water content and field CO2 pulses that have previously been difficult to detect and explain. All observed CO2 pulses over the measurement period corresponded to surface wetting events, including when the wetting events did not penetrate into the soil below the biocrust layer (0–2 mm). The variability of temperature and moisture of the biocrust surface layer was much greater than even in the 0–5 cm layer of the soil beneath the biocrust, or deeper in the soil profile. We therefore suggest that coupling surface measurements of biocrust moisture and temperature to automated CO2flux measurements may greatly improve our understanding of the climatic sensitivity of carbon cycling in biocrusted interspaces in our study region, and that this method may be globally relevant and applicable.

Effect of in-situ aged and fresh biochar on soil hydraulic conditions and microbial C use under drought conditions.

PubMed

Paetsch, Lydia; Mueller, Carsten W; Kögel-Knabner, Ingrid; von Lützow, Margit; Girardin, Cyril; Rumpel, Cornelia

2018-05-01

Biochar (BC) amendments may be suitable to increase the ecosystems resistance to drought due to their positive effects on soil water retention and availability. We investigated the effect of BC in situ ageing on water availability and microbial parameters of a grassland soil. We used soil containing 13 C labeled BC and determined its water holding capacity, microbial biomass and activity during a 3 months incubation under optimum and drought conditions. Our incubation experiment comprised three treatments: soil without BC (Control), soil containing aged BC (BC aged ) and soil containing fresh BC (BC fresh ), under optimum soil water (pF 1.8) and drought conditions (pF 3.5). Under optimum water as well as drought conditions, soils containing BC showed higher soil organic carbon (SOC) mineralization as compared to control soil. Moreover, BC effects on the soil water regime increase upon in situ aging. Native SOC mineralization increased most for soils containing BC aged . The BC aged led to improved C use under drought as compared to the other treatments. We conclude that BC addition to soils can ameliorate their water regime, especially under drought conditions. This beneficial effect of BC increases upon its aging, which also improved native substrate availability.

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).

Influence of understory cover on soil water and evaporation fluxes: a trial

NASA Astrophysics Data System (ADS)

Jiménez-Rodríguez, César; Magdalena Warter, Maria; Coenders-Gerrits, Miriam

2017-04-01

Within a forest ecosystem the litter layer is an important hydrological component and contributes towards the water and energy exchange between the sub-canopy and the soil. Evaporation within a forest is made up of different fractions coming from the dry soil, vegetation and litter layers. The quantification and partitioning of each fraction remains difficult as there is hard to estimate correctly the amount of water moved by evaporation or percolation at ecosystem level. With the aim to determine the influence of forest understory on the evaporation fluxes, four ground cover types were selected from the Speulderbos forest in the Netherlands. The mosses species of "Thamariskmoss" (Thuidium thamariscinum), "Rough Stalked Feathermoss" (Brachythecium rutabulum), and "Haircapmoss" (Polytrichum commune) were compared with a litter layer made up of Douglas-Fir needles (Pseudotsuga menziesii). Four PVC basins with 40cm x 60cm were filled with forest soil and sheltered with the selected ground covers. Each box was equipped with a soil moisture sensor, and a set Temperature and Relative Humidity sensors to determine the VPD during the study period. The study period lasts 4 weeks, while the percolation rates were measured in a daily basis. The rainfall events were simulated in the lab, applying the same rain event to each box at the same time. A total amount of 43.12 mm of rain were added to the boxes during the 4 weeks of the experiment, and distributed in 11 rain events which differ in amount and timing between events. The percolation in all the boxes was more than the 50% of the rain events due to the sandy condition of the soil, while the evaporation rates were affected not only by the room atmospheric conditions, but for the cover type present in each box. Except for the Polytrichum moss, a moss known for its water conducting abilities, all cover types showed a decline before and increase after a rain event. This species showed a steady increase in soil water content over the sampling period due to keeping the water longer in the surface. The evaporation was driven partly by the temperature in the room, while the structural characteristics of the mosses allow the differences in evaporation rates showed along the study period.

An Equipment to Measure the Freezing Point of Soils under Higher Pressure

NASA Astrophysics Data System (ADS)

Wang, Dayan; Guan, Hui; Wen, Zhi; Ma, Wei

2014-05-01

Soil freezing point is the highest temperature at which ice can be presented in the system and soil can be referred to as frozen. The freezing temperature of soil is an important parameter for solving many practical problems in civil engineering, such as evaluation of soil freezing depth, prediction of soil heaving, force of soil suction, etc. However, as the freezing temperature is always affected by many factors like soil particle size, mineral composition, water content and the external pressure endured by soils, to measure soil freezing point is a rather difficult task until now, not to mention the soil suffering higher pressure. But recently, with the artificial freezing technology widely used in the excavation of deep underground space, the frozen wall thickness is a key factor to impact the security and stability of deep frozen wall. To determine the freeze wall thickness, the location of the freezing front must be determined firstly, which will deal with the determination of the soil freezing temperature. So how to measure the freezing temperature of soil suffering higher pressure is an important problem to be solved. This paper will introduce an equipment which was developed lately by State Key Laboratory of Frozen Soil Engineering to measure the freezing-point of soils under higher pressure. The equipment is consisted of cooling and keeping temperature system, temperature sensor and data collection system. By cooling and keeping temperature system, not only can we make the higher pressure soil sample's temperature drop to a discretionary minus temperature, but also keep it and reduce the heat exchange of soil sample with the outside. The temperature sensor is the key part to our measurement, which is featured by high precision and high sensitivity, what is more important is that the temperature sensor can work in a higher pressure condition. Moreover, the major benefit of this equipment is that the soil specimen's loads can be loaded by any microcomputer control electron universal testing machines. All of above mentioned advantages of this equipment ensures one to catch up the moment soil turns from the thawed state into ice and enable one to determine the freezing point experimentally by recording the temperature-time history (cooling curve) at particular points within the sample used for analysis. Therefore, this equipment has excellent characteristics such as compact construction, convenient operation, high reliability and the measuring accuracy. The authors would like to thank the following agents for their financial supports: the National Natural Science Foundation (No.41071048),Hundred Talent Young Scientists program of the Chinese Academy of Sciences granted to Dr. Zhi Wen.

Anoxic conditions drive phosphorus limitation in humid tropical forest soil microorganisms

NASA Astrophysics Data System (ADS)

Gross, A.; Pett-Ridge, J.; Weber, P. K.; Blazewicz, S.; Silver, W. L.

2017-12-01

The elemental stoichiometry of carbon (C), nitrogen (N) and phosphorus (P) of soil microorganisms (C:N:P ratios) regulates transfers of energy and nutrients to higher trophic levels. In humid tropical forests that grow on P-depleted soils, the ability of microbes to concentrate P from their surroundings likely plays a critical role in P-retention and ultimately in forest productivity. Models predict that climate change will cause dramatic changes in rainfall patterns in the humid tropics and field studies have shown these changes can affect the redox state of tropical forest soils, influencing soil respiration and biogeochemical cycling. However, the responses of soil microorganisms to changing environmental conditions are not well known. Here, we incubated humid tropical soils under oxic or anoxic conditions with substrates differing in both C:P stoichiometry and lability, to assess how soil microorganisms respond to different redox regimes. We found that under oxic conditions, microbial C:P ratios were similar to the global optimal ratio (55:1), indicating most microbial cells can adapt to persistent aerated conditions in these soils. However, under anoxic conditions, the ability of soil microbes to acquire soil P declined and their C:P ratios shifted away from the optimal ratio. NanoSIMS elemental imaging of single cells extracted from soil revealed that under anoxic conditions, C:P ratios were above the microbial optimal value in 83% of the cells, in comparison to 41% under oxic conditions. These data suggest microbial growth efficiency switched from being energy limited under oxic conditions to P-limited under anoxic conditions, indicating that, microbial growth in low P humid tropical forests soils may be most constrained by P-limitation when conditions are oxygen-limited. We suggest that differential microbial responses to soil redox states could have important implications for productivity of humid tropical forests under future climate scenarios.

Modeling the Soil Water and Energy Balance of a Mixed Grass Rangeland and Evaluating a Soil Water Based Drought Index in Wyoming

NASA Astrophysics Data System (ADS)

Engda, T. A.; Kelleners, T. J.; Paige, G. B.

2013-12-01

Soil water content plays an important role in the complex interaction between terrestrial ecosystems and the atmosphere. Automated soil water content sensing is increasingly being used to assess agricultural drought conditions. A one-dimensional vertical model that calculates incoming solar radiation, canopy energy balance, surface energy balance, snow pack dynamics, soil water flow, snow-soil heat exchange is applied to calculate water flow and heat transport in a Rangeland soil located near Lingel, Wyoming. The model is calibrated and validated using three years of measured soil water content data. Long-term average soil water content dynamics are calculated using a 30 year historical data record. The difference between long-term average soil water content and observed soil water content is compared with plant biomass to evaluate the usefulness of soil water content as a drought indicator. Strong correlation between soil moisture surplus/deficit and plant biomass may prove our hypothesis that soil water content is a good indicator of drought conditions. Soil moisture based drought index is calculated using modeled and measured soil water data input and is compared with measured plant biomass data. A drought index that captures local drought conditions proves the importance of a soil water monitoring network for Wyoming Rangelands to fill the gap between large scale drought indices, which are not detailed enough to assess conditions at local level, and local drought conditions. Results from a combined soil moisture monitoring and computer modeling, and soil water based drought index soil are presented to quantify vertical soil water flow, heat transport, historical soil water variations and drought conditions in the study area.

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.

Landform and vegetation patch type moderate the effects of grazing-induced disturbance on carbon and nitrogen pools in a semi-arid woodland

USDA-ARS?s Scientific Manuscript database

Background and aims Dryland soil organic carbon (C) pools account for a large portion of soil C globally, but their response to livestock grazing has been difficult to generalize. We hypothesized that some difficulty generalizing was due to spatial heterogeneity in dryland systems. We examined the i...

Experimental Investigation of Soil and Atmospheric Conditions on the Momentum, Mass, and Thermal Boundary Layers Above the Land Atmosphere Interface

NASA Astrophysics Data System (ADS)

Trautz, A.; Smits, K. M.; Illangasekare, T. H.; Schulte, P.

2014-12-01

The purpose of this study is to investigate the impacts of soil conditions (i.e. soil type, saturation) and atmospheric forcings (i.e. velocity, temperature, relative humidity) on the momentum, mass, and temperature boundary layers. The atmospheric conditions tested represent those typically found in semi-arid and arid climates and the soil conditions simulate the three stages of evaporation. The data generated will help identify the importance of different soil conditions and atmospheric forcings with respect to land-atmospheric interactions which will have direct implications on future numerical studies investigating the effects of turbulent air flow on evaporation. The experimental datasets generated for this study were performed using a unique climate controlled closed-circuit wind tunnel/porous media facility located at the Center for Experimental Study of Subsurface Environmental Processes (CESEP) at the Colorado School of Mines. The test apparatus consisting of a 7.3 m long porous media tank and wind tunnel, were outfitted with a sensor network to carefully measure wind velocity, air and soil temperature, relative humidity, soil moisture, and soil air pressure. Boundary layer measurements were made between the heights of 2 and 500 mm above the soil tank under constant conditions (i.e. wind velocity, temperature, relative humidity). The soil conditions (e.g. soil type, soil moisture) were varied between datasets to analyze their impact on the boundary layers. Experimental results show that the momentum boundary layer is very sensitive to the applied atmospheric conditions and soil conditions to a much less extent. Increases in velocity above porous media leads to momentum boundary layer thinning and closely reflect classical flat plate theory. The mass and thermal boundary layers are directly dependent on both atmospheric and soil conditions. Air pressure within the soil is independent of atmospheric temperature and relative humidity - wind velocity and soil moisture effects were observed. This data provides important insight into future work of accurately modeling the exchange processes associated with evaporation under various turbulent atmospheric conditions.

Types, harms and improvement of saline soil in Songnen Plain

NASA Astrophysics Data System (ADS)

Wang, Zhengjun; Zhuang, Jingjing; Zhao, Anping; Li, Xinxin

2018-03-01

Saline soil is an extremely difficult and modified soil, widely distributed around the world. According to UN-UNESCO and FAO, the world’s saline soil area is about 9.54×108hm2, and there is a growing trend, every year in 1.0×106-1.5×106hm2 speed growth, the effective utilization of land resources to the world is the most serious threat. The total area of saline-alkali land in China is about 9.91×107hm2, including the Songnen Plain, which is called one of the three major saline soil concentrations in the world. The Songnen plain is an important grain producing area in China, and the saline soil occupies most of the Songnen plain, so it is of great significance to study the saline soil and improvement in Songnen plain.

Smsynth: AN Imagery Synthesis System for Soil Moisture Retrieval

NASA Astrophysics Data System (ADS)

Cao, Y.; Xu, L.; Peng, J.

2018-04-01

Soil moisture (SM) is a important variable in various research areas, such as weather and climate forecasting, agriculture, drought and flood monitoring and prediction, and human health. An ongoing challenge in estimating SM via synthetic aperture radar (SAR) is the development of the retrieval SM methods, especially the empirical models needs as training samples a lot of measurements of SM and soil roughness parameters which are very difficult to acquire. As such, it is difficult to develop empirical models using realistic SAR imagery and it is necessary to develop methods to synthesis SAR imagery. To tackle this issue, a SAR imagery synthesis system based on the SM named SMSynth is presented, which can simulate radar signals that are realistic as far as possible to the real SAR imagery. In SMSynth, SAR backscatter coefficients for each soil type are simulated via the Oh model under the Bayesian framework, where the spatial correlation is modeled by the Markov random field (MRF) model. The backscattering coefficients simulated based on the designed soil parameters and sensor parameters are added into the Bayesian framework through the data likelihood where the soil parameters and sensor parameters are set as realistic as possible to the circumstances on the ground and in the validity range of the Oh model. In this way, a complete and coherent Bayesian probabilistic framework is established. Experimental results show that SMSynth is capable of generating realistic SAR images that suit the needs of a large amount of training samples of empirical models.

Production of high-resolution forest-ecosite maps based on model predictions of soil moisture and nutrient regimes over a large forested area.

PubMed

Yang, Qi; Meng, Fan-Rui; Bourque, Charles P-A; Zhao, Zhengyong

2017-09-08

Forest ecosite reflects the local site conditions that are meaningful to forest productivity as well as basic ecological functions. Field assessments of vegetation and soil types are often used to identify forest ecosites. However, the production of high-resolution ecosite maps for large areas from interpolating field data is difficult because of high spatial variation and associated costs and time requirements. Indices of soil moisture and nutrient regimes (i.e., SMR and SNR) introduced in this study reflect the combined effects of biogeochemical and topographic factors on forest growth. The objective of this research is to present a method for creating high-resolution forest ecosite maps based on computer-generated predictions of SMR and SNR for an area in Atlantic Canada covering about 4.3 × 10 6 hectares (ha) of forestland. Field data from 1,507 forest ecosystem classification plots were used to assess the accuracy of the ecosite maps produced. Using model predictions of SMR and SNR alone, ecosite maps were 61 and 59% correct in identifying 10 Acadian- and Maritime-Boreal-region ecosite types, respectively. This method provides an operational framework for the production of high-resolution maps of forest ecosites over large areas without the need for data from expensive, supplementary field surveys.

Salinity tolerance and mycorrhizal responsiveness of native xeroriparian plants in semi-arid western USA

USGS Publications Warehouse

Beauchamp, Vanessa B.; Walz, C.; Shafroth, P.B.

2009-01-01

Restoration of salt-affected soils is a global concern. In the western United States, restoration of salinized land, particularly in river valleys, often involves control of Tamarix, an introduced species with high salinity tolerance. Revegetation of hydrologically disconnected floodplains and terraces after Tamarix removal is often difficult because of limited knowledge regarding the salinity tolerance of candidate native species for revegetation. Additionally, Tamarix appears to be non-mycorrhizal. Extended occupation of Tamarix may deplete arbuscular mycorrhizal fungi in the soil, further decreasing the success of revegetation efforts. To address these issues, we screened 42 species, races, or ecotypes native to southwestern U.S. for salinity tolerance and mycorrhizal responsiveness. As expected, the taxa tested showed a wide range of responses to salinity and mycorrhizal fungi. This variation also occurred between ecotypes or races of the same species, indicating that seed collected from high-salinity reference systems is likely better adapted to harsh conditions than seed originating from less saline environments. All species tested had a positive or neutral response to mycorrhizal inoculation. We found no clear evidence that mycorrhizae increased salinity tolerance, but some species were so dependent on mycorrhizal fungi that they grew poorly at all salinity levels in pasteurized soil. ?? 2009 Elsevier B.V.

Reduced transpiration response to precipitation pulses precedes mortality in a piñon-juniper woodland subject to prolonged drought.

PubMed

Plaut, Jennifer A; Wadsworth, W Duncan; Pangle, Robert; Yepez, Enrico A; McDowell, Nate G; Pockman, William T

2013-10-01

Global climate change is predicted to alter the intensity and duration of droughts, but the effects of changing precipitation patterns on vegetation mortality are difficult to predict. Our objective was to determine whether prolonged drought or above-average precipitation altered the capacity to respond to the individual precipitation pulses that drive productivity and survival. We analyzed 5 yr of data from a rainfall manipulation experiment in piñon-juniper (Pinus edulis-Juniperus monosperma) woodland using mixed effects models of transpiration response to event size, antecedent soil moisture, and post-event vapor pressure deficit. Replicated treatments included irrigation, drought, ambient control and infrastructure control. Mortality was highest under drought, and the reduced post-pulse transpiration in the droughted trees that died was attributable to treatment effects beyond drier antecedent conditions and reduced event size. In particular, trees that died were nearly unresponsive to antecedent shallow soil moisture, suggesting reduced shallow absorbing root area. Irrigated trees showed an enhanced response to precipitation pulses. Prolonged drought initiates a downward spiral whereby trees are increasingly unable to utilize pulsed soil moisture. Thus, the additive effects of future, more frequent droughts may increase drought-related mortality. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

Uncertainty in accounting for carbon accumulation following forest harvesting

NASA Astrophysics Data System (ADS)

Lilly, P.; Yanai, R. D.; Arthur, M. A.; Bae, K.; Hamburg, S.; Levine, C. R.; Vadeboncoeur, M. A.

2014-12-01

Tree biomass and forest soils are both difficult to quantify with confidence, for different reasons. Forest biomass is estimated non-destructively using allometric equations, often from other sites; these equations are difficult to validate. Forest soils are destructively sampled, resulting in little measurement error at a point, but with large sampling error in heterogeneous soil environments, such as in soils developed on glacial till. In this study, we report C contents of biomass and soil pools in northern hardwood stands in replicate plots within replicate stands in 3 age classes following clearcut harvesting (14-19 yr, 26-29 yr, and > 100 yr) at the Bartlett Experimental Forest, USA. The rate of C accumulation in aboveground biomass was ~3 Mg/ha/yr between the young and mid-aged stands and <1 Mg/ha/yr between the mid-aged and mature stands. We propagated model uncertainty through allometric equations, and found errors ranging from 3-7%, depending on the stand. The variation in biomass among plots within stands (6-19%) was always larger than the allometric uncertainties. Soils were described by quantitative soil pits in three plots per stand, excavated by depth increment to the C horizon. Variation in soil mass among pits within stands averaged 28% (coefficient of variation); variation among stands within an age class ranged from 9-25%. Variation in carbon concentrations averaged 27%, mainly because the depth increments contained varying proportions of genetic horizons, in the upper part of the soil profile. Differences across age classes in soil C were not significant, because of the high variability. Uncertainty analysis can help direct the design of monitoring schemes to achieve the greatest confidence in C stores per unit of sampling effort. In the system we studied, more extensive sampling would be the best approach to reducing uncertainty, as natural spatial variation was higher than model or measurement uncertainties.

Spatial Data Mining for Estimating Cover Management Factor of Universal Soil Loss Equation

NASA Astrophysics Data System (ADS)

Tsai, F.; Lin, T. C.; Chiang, S. H.; Chen, W. W.

2016-12-01

Universal Soil Loss Equation (USLE) is a widely used mathematical model that describes long-term soil erosion processes. Among the six different soil erosion risk factors of USLE, the cover-management factor (C-factor) is related to land-cover/land-use. The value of C-factor ranges from 0.001 to 1, so it alone might cause a thousandfold difference in a soil erosion analysis using USLE. The traditional methods for the estimation of USLE C-factor include in situ experiments, soil physical parameter models, USLE look-up tables with land use maps, and regression models between vegetation indices and C-factors. However, these methods are either difficult or too expensive to implement in large areas. In addition, the values of C-factor obtained using these methods can not be updated frequently, either. To address this issue, this research developed a spatial data mining approach to estimate the values of C-factor with assorted spatial datasets for a multi-temporal (2004 to 2008) annual soil loss analysis of a reservoir watershed in northern Taiwan. The idea is to establish the relationship between the USLE C-factor and spatial data consisting of vegetation indices and texture features extracted from satellite images, soil and geology attributes, digital elevation model, road and river distribution etc. A decision tree classifier was used to rank influential conditional attributes in the preliminary data mining. Then, factor simplification and separation were considered to optimize the model and the random forest classifier was used to analyze 9 simplified factor groups. Experimental results indicate that the overall accuracy of the data mining model is about 79% with a kappa value of 0.76. The estimated soil erosion amounts in 2004-2008 according to the data mining results are about 50.39 - 74.57 ton/ha-year after applying the sediment delivery ratio and correction coefficient. Comparing with estimations calculated with C-factors from look-up tables, the soil erosion values estimated with C-factors generated from spatial data mining results are more in agreement with the values published by the watershed administration authority.

Impact of groundwater levels on evaporation and water-vapor fluxes in highly saline soils

NASA Astrophysics Data System (ADS)

Munoz, J. F.; Hernández, M. F.; Braud, I.; Gironas, J. A.; Suarez, F. I.

2012-12-01

In aquifers of arid and hyper-arid zones, such as those occurring in the Chilean Andes high plateau, it is important to determine both the quantity and location of water discharges at the temporal scales of interest to close the basin's water budget and thus, to manage the water resource properly. In zones where shallow aquifers are the main source of water, overexploitation of the water resource changes the dynamics of water, heat and solute transport in the vadose zone. As aquifers are exploited, fluctuations in depth to groundwater are exacerbated. These fluctuations modify both soil structure and evaporation from the ground, which is typically the most important discharge from the water budget and is very difficult to estimate. Therefore, a correct quantification of evaporation from these soils is essential to improve the accuracy of the water balance estimation. The objective of this study was to investigate the evaporation processes and water-vapor fluxes in a soil column filled with a saline soil from the Salar del Huasco basin, Chile. Water content, electrical conductivity and temperature at different depths in the soil profile were monitored to determine the liquid and vapor fluxes within the soil column. The results showed that evaporation is negligible when the groundwater table is deeper than 1 m. For shallower groundwater levels, evaporation increases in an exponential fashion reaching a value of 3 mm/day when the groundwater table is near the surface of the ground. These evaporation rates are on the same order of magnitude than the field measurements, but slightly lower due to the controlled conditions maintained in the laboratory. Isothermal fluid fluxes were predominant over the non-isothermal fluid and water vapor fluxes. The net flux for all the phreatic levels tested in the laboratory showed different behaviors, with ascending or descending flows as a consequence of changes in water content and temperature distribution within the soil. It was found that evaporation from bare soils occurs as a consequence of vapor transport due to the thermal gradients. This vapor transport was also influences by the salinity of the soil.

[A site index model for Larix principis-rupprechtii plantation in Saihanba, north China].

PubMed

Wang, Dong-zhi; Zhang, Dong-yan; Jiang, Feng-ling; Bai, Ye; Zhang, Zhi-dong; Huang, Xuan-rui

2015-11-01

It is often difficult to estimate site indices for different types of plantation by using an ordinary site index model. The objective of this paper was to establish a site index model for plantations in varied site conditions, and assess the site qualities. In this study, a nonlinear mixed site index model was constructed based on data from the second class forest resources inventory and 173 temporary sample plots. The results showed that the main limiting factors for height growth of Larix principis-rupprechtii were elevation, slope, soil thickness and soil type. A linear regression model was constructed for the main constraining site factors and dominant tree height, with the coefficient of determination being 0.912, and the baseline age of Larix principis-rupprechtii determined as 20 years. The nonlinear mixed site index model parameters for the main site types were estimated (R2 > 0.85, the error between the predicted value and the actual value was in the range of -0.43 to 0.45, with an average root mean squared error (RMSE) in the range of 0.907 to 1.148). The estimation error between the predicted value and the actual value of dominant tree height for the main site types was in the confidence interval of [-0.95, 0.95]. The site quality of the high altitude-shady-sandy loam-medium soil layer was the highest and that of low altitude-sunny-sandy loam-medium soil layer was the lowest, while the other two sites were moderate.

Enrichment and Molecular Characterization of a Bacterial Culture That Degrades Methoxy-Methyl Urea Herbicides and Their Aniline Derivatives

PubMed Central

El-Fantroussi, Said

2000-01-01

Soil treated with linuron for more than 10 years showed high biodegradation activity towards methoxy-methyl urea herbicides. Untreated control soil samples taken from the same location did not express any linuron degradation activity, even after 40 days of incubation. Hence, the occurrence in the field of a microbiota having the capacity to degrade a specific herbicide was related to the long-term treatment of the soil. The enrichment culture isolated from treated soil showed specific degradation activity towards methoxy-methyl urea herbicides, such as linuron and metobromuron, while dimethyl urea herbicides, such as diuron, chlorotoluron, and isoproturon, were not transformed. The putative metabolic intermediates of linuron and metobromuron, the aniline derivatives 3,4-dichloroaniline and 4-bromoaniline, were also degraded. The temperature of incubation drastically affected degradation of the aniline derivatives. Whereas linuron was transformed at 28 and 37°C, 3,4-dichloroaniline was transformed only at 28°C. Monitoring the enrichment process by reverse transcription-PCR and denaturing gradient gel electrophoresis (DGGE) showed that a mixture of bacterial species under adequate physiological conditions was required to completely transform linuron. This research indicates that for biodegradation of linuron, several years of adaptation have led to selection of a bacterial consortium capable of completely transforming linuron. Moreover, several of the putative species appear to be difficult to culture since they were detectable by DGGE but were not culturable on agar plates. PMID:11097876

Difficulties in the evaluation and measuring of soil water infiltration

NASA Astrophysics Data System (ADS)

Pla-Sentís, Ildefonso

2013-04-01

Soil water infiltration is the most important hydrological parameter for the evaluation and diagnosis of the soil water balance and soil moisture regime. Those balances and regimes are the main regulating factors of the on site water supply to plants and other soil organisms and of other important processes like runoff, surface and mass erosion, drainage, etc, affecting sedimentation, flooding, soil and water pollution, water supply for different purposes (population, agriculture, industries, hydroelectricity), etc. Therefore the evaluation and measurement of water infiltration rates has become indispensable for the evaluation and modeling of the previously mentioned processes. Infiltration is one of the most difficult hydrological parameters to evaluate or measure accurately. Although the theoretical aspects of the process of soil water infiltration are well known since the middle of the past century, when several methods and models were already proposed for the evaluation of infiltration, still nowadays such evaluation is not frequently enough accurate for the purposes being used. This is partially due to deficiencies in the methodology being used for measuring infiltration, including some newly proposed methods and equipments, and in the use of non appropriate empirical models and approaches. In this contribution we present an analysis and discussion about the main difficulties found in the evaluation and measurement of soil water infiltration rates, and the more commonly committed errors, based on the past experiences of the author in the evaluation of soil water infiltration in many different soils and land conditions, and in their use for deducing soil water balances under variable and changing climates. It is concluded that there are not models or methods universally applicable to any soil and land condition, and that in many cases the results are significantly influenced by the way we use a particular method or instrument, and by the alterations in the soil conditions by the land management, but also due to the manipulation of the soil before and during the measurement. Direct "in situ" field evaluations have to be preferred in any case to indirect deductions from other soil characteristics measured under laboratory conditions in the same soils, or in other soils, through the so called "pedo-transfer" functions, or through the use of stochastic models such as the SCS Curve Number Method, or of other models using empirical or physical approaches, which have demonstrated to be of limited value in most of the cases. References Philip, J. R., 1954., An infiltration equation with physical significance: Soil Sci..,v. 77, p. 153-157. Philip, J. R., 1958. The theory of infiltration, pt. 7: Soil Sci., v. 85, no. 6, p. 333-337. Pla, I.1981. Simuladores de lluvia para el estudio de relaciones suelo-agua bajo agricultura de secano en los trópicos. Rev. Fac. Agron. XII(1-2):81-93.Maracay (Venezuela) Pla, I. 1986. A routine laboratory index to predict the effects of soil sealing on soil and water conservation. En "Assesment of Soil Surface Sealing and Crusting". 154-162.State Univ. of Ghent.Gante (Bélgica Pla, I., 1997. A soil water balance model for monitoring soil erosion processes and effects on steep lands in the tropics. Soil Technology. 11(1):17-30. Elsevier Pla, I., M.C. Ramos, S. Nacci, F. Fonseca y X. Abreu. 2005. Soil moisture regime in dryland vineyards of Catalunya (Spain) as influenced by climate, soil and land management. "Integrated Soil and Water Management for Orchard Development". FAO Land and Water Bulletin 10. 41-49. Roma (Italia). Pla, I., 2006. Hydrological approach for assessing desertification processes in the Mediterranean region. In W.G. Kepner et al. (Editors), Desertification in the Mediterranean Region. A Security Issue. 579-600 Springer. Heidelberg (Germany) Pla, I. 2011. Evaluación y Modelización Hidrológica para el Diagnóstico y Prevención de "Desastres Naturales". Gestión y Ambiente 14 (3): 17-22. UN-Medellín (Colombia). ISSN 0124.177X Pla, I. 2011. Medición y evaluación de propiedades físicas de los suelos: dificultades y errores más frecuentes. II-Propiedades hidrológicas. Suelos Ecuatoriales 40 (2): 94-127 Reynolds W.D., B.T. Bowman, R.R. Brunke, C.F. Drury and C.S. Tan. 2000. Comparison of Tension Infiltrometer, Pressure Infiltrometer, and Soil Core Estimates of Saturated Hydraulic Conductivity . Soil Science Society of America Journal 64:478-484 Richards, L. A., 1952. Report of the Subcommittee on Permeability and Infiltration, Committee on Terminology, Soil Science Society of America: Soil Sci. Soc.America Proc., v. 16, p. 85-88. Segal, E., S.A.Bradford, P. Shouse; N. Lazarovich, and D. Corwin. 2008. Integration of Hard and Soft Data to Characterize Field-Scale Hydraulic Properties for Flow and Transport Studies. Vadose Zone J 7:878-889 Young, E. 1991. Infiltration measurements, a review. Hydrological processes 5: 309-320

Characterization of soils from an industrial complex contaminated with elemental mercury

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

Miller, Carrie L., E-mail: millercl@ornl.gov; Watson, David B.; Lester, Brian P.

2013-08-15

Historical use of liquid elemental mercury (Hg(0){sub l}) at the Y-12 National Security Complex in Oak Ridge, TN, USA, resulted in large deposits of Hg(0){sub l} in the soils. The fate and distribution of the spilled Hg(0) are not well characterized. In this study we evaluated analytical tools for characterizing the speciation of Hg in the contaminated soils and then used the analytical techniques to examine the speciation of Hg in two soil cores collected at the site. These include x-ray fluorescence (XRF), soil Hg(0) headspace analysis, and total Hg determination by acid digestion coupled with cold vapor atomic absorptionmore » (HgT). XRF was not found to be suitable for evaluating Hg concentrations in heterogeneous soils containing low concentration of Hg or Hg(0) because Hg concentrations determined using this method were lower than those determined by HgT analysis and the XRF detection limit is 20 mg/kg. Hg(0){sub g} headspace analysis coupled with HgT measurements yielded good results for examining the presence of Hg(0){sub l} in soils and the speciation of Hg. The two soil cores are highly heterogeneous in both the depth and extent of Hg contamination, with Hg concentrations ranging from 0.05 to 8400 mg/kg. In the first core, Hg(0){sub l} was distributed throughout the 3.2 m depth, whereas the second core, from a location 12 m away, contained Hg(0){sub l} in a 0.3 m zone only. Sequential extractions showed organically associated Hg dominant at depths with low Hg concentration. Soil from the zone of groundwater saturation showed reducing conditions and the Hg is likely present as Hg-sulfide species. At this depth, lateral Hg transport in the groundwater may be a source of Hg detected in the soil at the deeper soil depths. Overall, characterization of soils containing Hg(0){sub l} is difficult because of the heterogeneous distribution of Hg within the soils. This is exacerbated in industrial facilities where fill materials make up much of the soils and historical and continued reworking of the subsurface has remobilized the Hg. -- Highlights: • Presence of Hg(0) and chemical transformations control the Hg speciation in soil. • Redox reactions can result in the mobilization and sequestration of Hg in soils. • Analysis of soils containing Hg(0) is complex due to sample heterogeneity.« less

Environmental microbiology as related to planetary quarantine

NASA Technical Reports Server (NTRS)

Iflug, I. J.

1971-01-01

The results of studies to determine the effect of soil particle size on the survival time at 125 C of the microflora associated with these particles are discussed. The data suggest that longer survival times exist for the microflora associated with larger particles. The studies indicate that microorganisms associated with soil are difficult to kill and that organisms associated with large particles are harder to kill than those associated with small particles. Sterlization requirements increase as the level of contamination increases. Soil particles and their accompanying microflora are the most critical contaminants.

Population densities of indigenous Acidobacteria change in the presence of plant growth promoting rhizobacteria (PGPR) in rhizosphere.

PubMed

Kalam, Sadaf; Das, Subha Narayan; Basu, Anirban; Podile, Appa Rao

2017-05-01

Rhizosphere microbial community has diverse metabolic capabilities and plays a crucial role in maintaining plant health. Oligotrophic plant growth promoting rhizobacteria (PGPR), along with difficult-to-culture microbial fractions, might be involved synergistically in microbe-microbe and plant-microbe interactions in the rhizosphere. Among the difficult-to-culture microbial fractions, Acidobacteria constitutes the most dominant phylum thriving in rhizospheric soils. We selected effective PGPR for tomato and black gram and studied their effect on population densities of acidobacterial members. Three facultatively oligotrophic PGPR were identified through 16S rRNA gene sequencing as Sphingobacterium sp. (P3), Variovorax sp. (P4), and Roseomonas sp. (A2); the latter being a new report of PGPR. In presence of selected PGPR strains, the changes in population densities of Acidobacteria were monitored in metagenomic DNA extracted from bulk and rhizospheric soils of tomato and black gram using real time qPCR. A gradual increase in equivalent cell numbers of Acidobacteria members was observed over time along with a simultaneous increase in plant growth promotion by test PGPR. We report characterization of three effective PGPR strains and their effects on indigenous, underexplored difficult-to-culture phylum-Acidobacteria. We suggest that putative interactions between these two bacterial groups thriving in rhizospheric soils could be beneficial for plant growth. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High atmospheric demand for water can limit forest carbon uptake and transpiration as severely as dry soil

Treesearch

Benjamin N. Sulman; Daniel Tyler Roman; Koong Yi; Lixin Wang; Richard P. Phillips; Kimberly A. Novick

2016-01-01

When stressed by low soil water content (SWC) or high vapor pressure deficit (VPD), plants close stomata, reducing transpiration and photosynthesis. However, it has historically been difficult to disentangle the magnitudes of VPD compared to SWC limitations on ecosystem-scale fluxes. We used a 13 year record of eddy covariance measurements from a forest in south...

Nutrient and Rainfall Additions Shift Phylogenetically Estimated Traits of Soil Microbial Communities.

PubMed

Gravuer, Kelly; Eskelinen, Anu

2017-01-01

Microbial traits related to ecological responses and functions could provide a common currency facilitating synthesis and prediction; however, such traits are difficult to measure directly for all taxa in environmental samples. Past efforts to estimate trait values based on phylogenetic relationships have not always distinguished between traits with high and low phylogenetic conservatism, limiting reliability, especially in poorly known environments, such as soil. Using updated reference trees and phylogenetic relationships, we estimated two phylogenetically conserved traits hypothesized to be ecologically important from DNA sequences of the 16S rRNA gene from soil bacterial and archaeal communities. We sampled these communities from an environmental change experiment in California grassland applying factorial addition of late-season precipitation and soil nutrients to multiple soil types for 3 years prior to sampling. Estimated traits were rRNA gene copy number, which contributes to how rapidly a microbe can respond to an increase in resources and may be related to its maximum growth rate, and genome size, which suggests the breadth of environmental and substrate conditions in which a microbe can thrive. Nutrient addition increased community-weighted mean estimated rRNA gene copy number and marginally increased estimated genome size, whereas precipitation addition decreased these community means for both estimated traits. The effects of both treatments on both traits were associated with soil properties, such as ammonium, available phosphorus, and pH. Estimated trait responses within several phyla were opposite to the community mean response, indicating that microbial responses, although largely consistent among soil types, were not uniform across the tree of life. Our results show that phylogenetic estimation of microbial traits can provide insight into how microbial ecological strategies interact with environmental changes. The method could easily be applied to any of the thousands of existing 16S rRNA sequence data sets and offers potential to improve our understanding of how microbial communities mediate ecosystem function responses to global changes.

Fractionation and characterization of soil organic carbon during transition to organic farming

NASA Astrophysics Data System (ADS)

Abdelrahman, H.; Olk, D.; Cocozza, C.; Miano, T.

2012-04-01

The transition from conventional to organic farming is the most difficult period faced by organic growers as it could be characterized by unstable conditions, such as nutrient availability, production reductions, mineralization extents. As soil organic matter (SOM), specifically soil organic carbon (SOC), is known to play important roles in maintenance and improvement of many soil properties, it is important to define its changes during the transition period. Total SOC might not be the suitable tool to track the changes in organically based soil fertility within a 3- to 5-yr transition period. Labile fractions that are important for nutrient cycling and supply are likely to be controlled by management to a much greater extent than is total SOM. Two field experiments, in south of Italy, were established in 2009 to study the changes in SOC during transition to organic farming. Experiments included a cereal/leguminous rotation with triplicates treatments of permitted amendments (compost and fertilizers). Soils were sampled at the beginning of the project, and after each crop harvest in 2010 and 2011. A sequential fractionation procedure was used to separate different SOC-fractions: light fraction (LF), two size classes of particulate organic matter (POM), mobile humic acid (MHA) and Ca++ bound humic acid (CaHA). Isolated fractions were quantified and analyzed for their content of C, N, carbohydrates and amino compounds fingerprints. The obtained results showed that compost application contributed to significantly higher quantities of LF, POM and MHA than did fertilizers application. Carbohydrates content decreased in LF while increased noticeably in POM and slightly in MHA fractions, which indicates that decomposing materials are converted, within the time span of humification, from young fractions into more mature fractions. Amino compounds were found to provide up to 40% of total soil N with a major contribution of the humified fractions, MHA and CaHA. The utilized fractionation procedure was found to be efficient in studying SOC changes in short term course.

Evaluating Lignite-Derived Products (LDPs) for Agriculture - Does Research Inform Practice?

NASA Astrophysics Data System (ADS)

Patti, Antonio; Rose, Michael; Little, Karen; Jackson, Roy; Cavagnaro, Timothy

2014-05-01

Lignite-derived products (LDPs), including humic acids and organo-mineral soil conditioners, are being marketed in many parts of the world. They are promoted as plant growth stimulants, additives that improve plant nutrient uptake as well as providing humic materials to improve soil structure and combat soil degradation. There are mixed views regarding the efficacy of these products and there is a lack of scientific studies that verify the efficacy of these products in the field. Anecdotally, agricultural producers become repeat users of the products when they see economic benefits, such as increases in crop yields, while others abandon repeat use when no benefits were seen. In this paper, we present results from a literature meta-analysis1 and a number of field studies that examine the potential for LDPs to improve soil fertility and plant growth. Our findings suggest that complex interactions between LDPs, soil types, environmental conditions and plant species mean that a 'one-size fits all' product or solution is unlikely; and that changes to soil characteristics brought about by LDPs are more apparent over longer time periods than a single cropping season. Most of these studies have not been undertaken in full field trial conditions, where the crop has been grown to harvest. Limited studies in small plots or glass-house conditions often report early benefits. It is not known if these benefits persist. Moreover, the actual composition of these additives may vary significantly and is rarely specified in full. In a study of our own, a small plot experiment evaluated the effect of a single application of a commercial potassium humate product from Victorian lignite on ryegrass and lucerne grown in a sandy, nutrient deficient, low organic matter soil. Treatment resulted in increased shoot growth (up to 33%) of ryegrass during the pasture establishment phase. Root growth was also improved with a 47% increase at 0-10 cm depth and 122% increase at 10-30 cm depth. However, these growth benefits subsequently diminished over time. Insignificant growth benefits were observed for lucerne. The analysis of the literature and our own work indicates that it is difficult to account for all the possible variables where research is used to inform land management practices. Assisting farmers to conduct localised research in cooperative ventures is likely to bring about the best outcomes where site-specific research directly informs land management practices. 1. Michael T. Rose, Antonio F. Patti, Karen R. Little, Alicia L. Brown, W. Roy Jackson, Timothy R. Cavagnaro, A Meta-Analysis and Review of Plant-Growth Response to Humic Substances: Practical Implications for Agriculture, Advances in Agronomy, 2013, 124, 37-89

Unusually high soil nitrogen oxide emissions influence air quality in a high-temperature agricultural region

PubMed Central

Oikawa, P. Y.; Ge, C.; Wang, J.; Eberwein, J. R.; Liang, L. L.; Allsman, L. A.; Grantz, D. A.; Jenerette, G. D.

2015-01-01

Fertilized soils have large potential for production of soil nitrogen oxide (NOx=NO+NO2), however these emissions are difficult to predict in high-temperature environments. Understanding these emissions may improve air quality modelling as NOx contributes to formation of tropospheric ozone (O3), a powerful air pollutant. Here we identify the environmental and management factors that regulate soil NOx emissions in a high-temperature agricultural region of California. We also investigate whether soil NOx emissions are capable of influencing regional air quality. We report some of the highest soil NOx emissions ever observed. Emissions vary nonlinearly with fertilization, temperature and soil moisture. We find that a regional air chemistry model often underestimates soil NOx emissions and NOx at the surface and in the troposphere. Adjusting the model to match NOx observations leads to elevated tropospheric O3. Our results suggest management can greatly reduce soil NOx emissions, thereby improving air quality. PMID:26556236

Signature simulation of mixed materials

NASA Astrophysics Data System (ADS)

Carson, Tyler D.; Salvaggio, Carl

2015-05-01

Soil target signatures vary due to geometry, chemical composition, and scene radiometry. Although radiative transfer models and function-fit physical models may describe certain targets in limited depth, the ability to incorporate all three signature variables is difficult. This work describes a method to simulate the transient signatures of soil by first considering scene geometry synthetically created using 3D physics engines. Through the assignment of spectral data from the Nonconventional Exploitation Factors Data System (NEFDS), the synthetic scene is represented as a physical mixture of particles. Finally, first principles radiometry is modeled using the Digital Imaging and Remote Sensing Image Generation (DIRSIG) model. With DIRSIG, radiometric and sensing conditions were systematically manipulated to produce and record goniometric signatures. The implementation of this virtual goniometer allows users to examine how a target bidirectional reflectance distribution function (BRDF) will change with geometry, composition, and illumination direction. By using 3D computer graphics models, this process does not require geometric assumptions that are native to many radiative transfer models. It delivers a discrete method to circumnavigate the significant cost of time and treasure associated with hardware-based goniometric data collections.

Fly ash for soil amelioration: A review on the influence of ash blending with inorganic and organic amendments

NASA Astrophysics Data System (ADS)

Ram, L. C.; Masto, R. E.

2014-01-01

Globally, fly ash (FA), generated in huge quantities from coal fired power plants is a problematic solid waste. Utilization of FA as an ameliorant for improving soil quality has received a great deal of attention over the past four decades, and many studies have been carried out worldwide. The silt-sized particles, low bulk density (BD), higher water holding capacity (WHC), favorable pH, and significant presence of plant nutrients in FA, make it a potential amendment for soils. The studies suggest enormous potential for the use of FA to improve cultivable, degraded/waste land, mine soil, landfills, and also to reclaim abandoned ash ponds, for agriculture and forestry. FA application improves the physical, chemical and biological qualities of soils to which it is applied. However, in some cases, depending on the characteristics of FA, the release of trace elements and soluble salts from FA to a soil-plant-human system could be a constraint. The effect is minimal in the case of weathered FA. The findings reflected the heterogeneity of ash characteristics, soil types, and agro-climatic conditions, thus a generalized conclusion on the impact of FA on plant species and soil quality is difficult. It is very important that the application of FA to soil must be very specific depending on the properties of the FA and soil. A considerable amount of research has been carried out to blend FA with varieties of organic and inorganic materials, like lime, gypsum, red mud, animal manure, poultry manure, sewage sludge, composts, press mud, vermicompost, biochar, bioinoculants, etc. Co-application of FA with these materials has much advantage: enhanced nutrient availability, decreased bioavailability of toxic metals, pH buffering, organic matter addition, microbial stimulation, overall improvement in the general health of the soil, etc. The performance of FA blending with organic and inorganic materials is better than FA alone treatments. Farm manure was found to be the most promising amendment used along with FA. While using FA in agriculture as a soil ameliorant, it is better to seek the locally available fitting blend materials for exploiting the benefits from their synergistic interaction. However, continuous research in parallel for long durations to dispel apprehension, if any, is desirable under well defined regulatory measures.

Soil erosion-runoff relationships: insights from laboratory studies

NASA Astrophysics Data System (ADS)

Mamedov, Amrakh; Warrington, David; Levy, Guy

2016-04-01

Understanding the processes and mechanisms affecting runoff generation and subsequent soil erosion in semi-arid regions is essential for the development of improved soil and water conservation management practices. Using a drip type laboratory rain simulator, we studied runoff and soil erosion, and the relationships between them, in 60 semi-arid region soils varying in their intrinsic properties (e.g., texture, organic matter) under differing extrinsic conditions (e.g., rain properties, and conditions prevailing in the field soil). Both runoff and soil erosion were significantly affected by the intrinsic soil and rain properties, and soil conditions within agricultural fields or watersheds. The relationship between soil erosion and runoff was stronger when the rain kinetic energy was higher rather than lower, and could be expressed either as a linear or exponential function. Linear functions applied to certain limited cases associated with conditions that enhanced soil structure stability, (e.g., slow wetting, amending with soil stabilizers, minimum tillage in clay soils, and short duration exposure to rain). Exponential functions applied to most of the cases under conditions that tended to harm soil stability (e.g., fast wetting of soils, a wide range of antecedent soil water contents and rain kinetic energies, conventional tillage, following biosolid applications, irrigation with water of poor quality, consecutive rain simulations). The established relationships between runoff and soil erosion contributed to a better understanding of the mechanisms governing overland flow and soil loss, and could assist in (i) further development of soil erosion models and research techniques, and (ii) the design of more suitable management practices for soil and water conservation.

Monitoring an Induced Permafrost Warming Experiment Using ERT, Temperature, and NMR in Fairbanks, Alaska

NASA Astrophysics Data System (ADS)

Ulrich, C.; Ajo Franklin, J. B.; Ekblaw, I.; Lindsey, N.; Wagner, A. M.; Saari, S.; Daley, T. M.; Freifeld, B. M.

2016-12-01

As global temperatures continue to rise, permafrost landscapes will experience more rapid changes than other global climate zones. Permafrost thaw is a result of increased temperatures in arctic settings resulting in surface deformation and subsurface hydrology changes. From an engineering perspective, surface deformation poses a threat to the stability of existing infrastructure such as roads, utility piping, and building structures. Preemptively detecting or monitoring subsurface thaw dynamics presents a difficult challenge due to the long time scales as deformation occurs. Increased subsurface moisture content results from permafrost thaw of which electrical resistivity tomography (ERT), soil temperature, and nuclear magnetic resonance (NMR) are directly sensitive. In this experiment we evaluate spatial and temporal changes in subsurface permafrost conditions (moisture content and temperature) at a experimental heating plot in Fairbanks, AK. This study focuses on monitoring thaw signatures using multiple collocated electrical resistivity (ERT), borehole temperature, and borehole nuclear magnetic resonance (NMR) measurements. Timelapse ERT (sensitive to changes in moisture content) was inverted using collocated temperature and NMR to constrain ERT inversions. Subsurface thermal state was monitored with timelapse thermistors, sensitive to soil ice content. NMR was collected in multiple boreholes and is sensitive to changes in moisture content and pore scale distribution. As permafrost thaws more hydrogen, in the form of water, is available resulting in a changing NMR response. NMR requires the availability of liquid water in order to induce spin of the hydrogen molecule, hence, if frozen water molecules will be undetectable. In this study, the permafrost is poised close to 0oC and is mainly silt with small pore dimensions; this combination makes NMR particularly useful due to the possibility of sub-zero thaw conditions within the soil column. Overall this experiment presents a complementary suite of methods that provides feedback on subsurface permafrost state even in cases where soil texture might control unfrozen water content.

Impact of runoff infiltration on contaminant accumulation and transport in the soil/filter media of Sustainable Urban Drainage Systems: A literature review.

PubMed

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

2016-11-01

The increasing use of Sustainable Urban Drainage Systems (SUDS) for stormwater management raises some concerns about the fate of ubiquitous runoff micropollutants in soils and their potential threat to groundwater. This question may be addressed either experimentally, by sampling and analyzing SUDS soil after a given operating time, or with a modeling approach to simulate the fate and transport of contaminants. After briefly reminding the processes responsible for the retention, degradation, or leaching of several urban-sourced contaminants in soils, this paper presents the state of the art about both experimental and modeling assessments. In spite of noteworthy differences in the sampling protocols, the soil parameters chosen as explanatory variables, and the methods used to evaluate the site-specific initial concentrations, most investigations undoubtedly evidenced a significant accumulation of metals and/or hydrocarbons in SUDS soils, which in the majority of the cases appears to be restricted to the upper 10 to 30cm. These results may suggest that SUDS exhibit an interesting potential for pollution control, but antinomic observations have also been made in several specific cases, and the inter-site concentration variability is still difficult to appraise. There seems to be no consensus regarding the level of complexity to be used in models. However, the available data deriving from experimental studies is generally limited to the contamination profiles and a few parameters of the soil, as a result of which "complex" models (including colloid-facilitated transport for example) appear to be difficult to validate before using them for predictive evaluations. Copyright © 2016 Elsevier B.V. All rights reserved.

The effectiveness of ground-penetrating radar surveys in the location of unmarked burial sites in modern cemeteries

NASA Astrophysics Data System (ADS)

Fiedler, Sabine; Illich, Bernhard; Berger, Jochen; Graw, Matthias

2009-07-01

Ground-penetration radar (GPR) is a geophysical method that is commonly used in archaeological and forensic investigations, including the determination of the exact location of graves. Whilst the method is rapid and does not involve disturbance of the graves, the interpretation of GPR profiles is nevertheless difficult and often leads to incorrect results. Incorrect identifications could hinder criminal investigations and complicate burials in cemeteries that have no information on the location of previously existing graves. In order to increase the number of unmarked graves that are identified, the GPR results need to be verified by comparing them with the soil and vegetation properties of the sites examined. We used a modern cemetery to assess the results obtained with GPR which we then compared with previously obtained tachymetric data and with an excavation of the graves where doubt existed. Certain soil conditions tended to make the application of GPR difficult on occasions, but a rough estimation of the location of the graves was always possible. The two different methods, GPR survey and tachymetry, both proved suitable for correctly determining the exact location of the majority of graves. The present study thus shows that GPR is a reliable method for determining the exact location of unmarked graves in modern cemeteries. However, the method did not allow statements to be made on the stage of decay of the bodies. Such information would assist in deciding what should be done with graves where ineffective degradation creates a problem for reusing graves following the standard resting time of 25 years.

Effects of anthropogenic particles on the chemical and geophysical properties of urban soils, Detroit, Michigan

NASA Astrophysics Data System (ADS)

Orlicki, Katharine M.

There is a great need in many cities for a better quality of urban soil maps. This is due to the increasing interest in repurposing vacant land for urban redevelopment, agriculture, and green infrastructure. Mapping vacant urban land in Detroit can be very difficult because anthropogenic soils were often highly variable and frequently contained demolition debris (such as brick), making it difficult to use a hand auger. This study was undertaken in Detroit, MI to create a more efficient way to map urban soils based on their geophysical and chemical properties. This will make the mapping process faster, less labor intensive, and therefore more cost effective. Optical and chemical criteria for the identification and classification of microartifacts (MAs) were made from a set of reference artifacts of a known origin. These MAs were then observed and tested in urban topsoil samples from sites in Detroit, Michigan that represent three different land use types (residential demolition, fly ash-impacted, and industrial). Optical analyses, SEM, EDAX, and XRD showed that reference MAs may be classified into five basic compositional types (carbonaceous, calcareous, siliceous, ferruginous and miscellaneous). Reference MAs were generally distinguishable using optical microscopy by color, luster, fracture and microtexture. MAs that were more difficult to classify were further differentiable when using SEM, EDAX, and XRD. MAs were found in all of the anthropogenic soils studied, but were highly variable. All three study sites had concentrations coal-related wastes were the most common types of MAs observed and often included coal, ash (microspheres, microagglomerate), cinders, and burnt shale. MAs derived from waste building materials such as brick, mortar, and glass, were typically found on residential demolition sites. Manufacturing waste MAs, which included iron-making slag and coked coal were commonly observed on industrial sites. Fly ash-impacted sites were composed of only microspheres and microagglomerate that were concentrated within the soils by airborne deposition, making it widespread. These results support the hypothesis that MA assemblages of distinct composition vary with land use. Therefore, it seems likely that magnetic susceptibility surveying and other geophysical methods will prove effective for mapping anthropogenic soils on vacant urban land. Anthropogenic soils and MAs were assessed for pH, electrical conductivity (EC), and magnetic susceptibility (MS). The A horizons of urban soils at residential demolition, industrial-impacted, and fly ash-impacted sites were found to be distinguishable from those of native soils. Anthropogenic soils were higher by one pH unit or more than the background level, had an EC value two to three times the background level, and had MS measurements up to 20 times greater than the background level. The analysis of reference artifacts suggested that the elevated pH of anthropogenic soils was caused by calcareous building material wastes, the elevated EC were the result of both calcareous and ferruginous wastes, and elevated MS were attributable to ferromagnetic materials. Anthropogenic soils collected at residential demolition sites were differentiable by EC, whereas those at collected form industrial sites were distinguishable using MS. Therefore, anthropogenic soils and native soils have a unique chemical and geophysical signature which can be highly dependent on the concentration of MAs. This suggests that EC and MS surveying methods may be used to remotely sense and map urban soils more effectively than using traditional methods alone.

The Effect of Thermal Convection on Earth-Atmosphere CO2 Gas Exchange in Aggregated Soil

NASA Astrophysics Data System (ADS)

Ganot, Y.; Weisbrod, N.; Dragila, M. I.

2011-12-01

Gas transport in soils and surface-atmosphere gas exchange are important processes that affect different aspects of soil science such as soil aeration, nutrient bio-availability, sorption kinetics, soil and groundwater pollution and soil remediation. Diffusion and convection are the two main mechanisms that affect gas transport, fate and emissions in the soils and in the upper vadose zone. In this work we studied CO2 soil-atmosphere gas exchange under both day-time and night-time conditions, focusing on the impact of thermal convection (TCV) during the night. Experiments were performed in a climate-controlled laboratory. One meter long columns were packed with matrix of different grain size (sand, gravel and soil aggregates). Air with 2000 ppm CO2 was injected into the bottom of the columns and CO2 concentration within the columns was continuously monitored by an Infra Red Gas Analyzer. Two scenarios were compared for each soil: (1) isothermal conditions, representing day time conditions; and (2) thermal gradient conditions, i.e., atmosphere colder than the soil, representing night time conditions. Our results show that under isothermal conditions, diffusion is the major mechanism for surface-atmosphere gas exchange for all grain sizes; while under night time conditions the prevailing mechanism is dependent on the air permeability of the matrix: for sand and gravel it is diffusion, and for soil aggregates it is TCV. Calculated CO2 flux for the soil aggregates column shows that the TCV flux was three orders of magnitude higher than the diffusive flux.

Parametrizing Evaporative Resistance for Heterogeneous Sparse Canopies through Novel Wind Tunnel Experimentation

NASA Astrophysics Data System (ADS)

Sloan, B.; Ebtehaj, A. M.; Guala, M.

2017-12-01

The understanding of heat and water vapor transfer from the land surface to the atmosphere by evapotranspiration (ET) is crucial for predicting the hydrologic water balance and climate forecasts used in water resources decision-making. However, the complex distribution of vegetation, soil and atmospheric conditions makes large-scale prognosis of evaporative fluxes difficult. Current ET models, such as Penman-Monteith and flux-gradient methods, are challenging to apply at the microscale due to ambiguity in determining resistance factors to momentum, heat and vapor transport for realistic landscapes. Recent research has made progress in modifying Monin-Obukhov similarity theory for dense plant canopies as well as providing clearer description of diffusive controls on evaporation at a smooth soil surface, which both aid in calculating more accurate resistance parameters. However, in nature, surfaces typically tend to be aerodynamically rough and vegetation is a mixture of sparse and dense canopies in non-uniform configurations. The goal of our work is to parameterize the resistances to evaporation based on spatial distributions of sparse plant canopies using novel wind tunnel experimentation at the St. Anthony Falls Laboratory (SAFL). The state-of-the-art SAFL wind tunnel was updated with a retractable soil box test section (shown in Figure 1), complete with a high-resolution scale and soil moisture/temperature sensors for recording evaporative fluxes and drying fronts. The existing capabilities of the tunnel were used to create incoming non-neutral stability conditions and measure 2-D velocity fields as well as momentum and heat flux profiles through PIV and hotwire anemometry, respectively. Model trees (h = 5 cm) were placed in structured and random configurations based on a probabilistic spacing that was derived from aerial imagery. The novel wind tunnel dataset provides the surface energy budget, turbulence statistics and spatial soil moisture data under varying atmospheric stability for each sparse canopy configuration. We will share initial data results and progress toward the development of new parametrizations that can account for the evolution of a canopy roughness sublayer on the momentum, heat and vapor resistance terms as a function of a stochastic representation of canopy spacing.

24 CFR 3285.201 - Soil conditions.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 24 Housing and Urban Development 5 2012-04-01 2012-04-01 false Soil conditions. 3285.201 Section... DEVELOPMENT MODEL MANUFACTURED HOME INSTALLATION STANDARDS Site Preparation § 3285.201 Soil conditions. To help prevent settling or sagging, the foundation must be constructed on firm, undisturbed soil or fill...

24 CFR 3285.201 - Soil conditions.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 24 Housing and Urban Development 5 2010-04-01 2010-04-01 false Soil conditions. 3285.201 Section... DEVELOPMENT MODEL MANUFACTURED HOME INSTALLATION STANDARDS Site Preparation § 3285.201 Soil conditions. To help prevent settling or sagging, the foundation must be constructed on firm, undisturbed soil or fill...

24 CFR 3285.201 - Soil conditions.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 24 Housing and Urban Development 5 2011-04-01 2011-04-01 false Soil conditions. 3285.201 Section... DEVELOPMENT MODEL MANUFACTURED HOME INSTALLATION STANDARDS Site Preparation § 3285.201 Soil conditions. To help prevent settling or sagging, the foundation must be constructed on firm, undisturbed soil or fill...

24 CFR 3285.201 - Soil conditions.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 24 Housing and Urban Development 5 2014-04-01 2014-04-01 false Soil conditions. 3285.201 Section... DEVELOPMENT MODEL MANUFACTURED HOME INSTALLATION STANDARDS Site Preparation § 3285.201 Soil conditions. To help prevent settling or sagging, the foundation must be constructed on firm, undisturbed soil or fill...

24 CFR 3285.201 - Soil conditions.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 24 Housing and Urban Development 5 2013-04-01 2013-04-01 false Soil conditions. 3285.201 Section... DEVELOPMENT MODEL MANUFACTURED HOME INSTALLATION STANDARDS Site Preparation § 3285.201 Soil conditions. To help prevent settling or sagging, the foundation must be constructed on firm, undisturbed soil or fill...

Arbuscular mycorrhizal colonization in soil fertilized by organic and mineral fertilizers

NASA Astrophysics Data System (ADS)

Dvořáčková, Helena; Záhora, Jaroslav; Mikajlo, Irina; Elbl, Jakub; Kynický, Jindřich; Hladký, Jan; Brtnický, Martin

2017-04-01

The level of arbuscular mycorrhizal colonization of roots represents one of the best parameters for assessing soil quality. This special type of symbiosis helps plants to obtain nutrients of the distant area which are unavailable without cooperation with arbuscular mycorrhizal fungi. For example the plant available form of phosphorus is of the most important elements in plant nutrition. This element can't move (significantly) throw the soil and it could be unachievable for root system of plant. The same situation also applies to other important nutrients and water. Colonization of individual roots by arbuscular mycorrhizal fungi has a direct effect on the enlargement of the root system but plant needs to invest sugar substance for development of fungi. It's very difficult to understand when fungi colonization represents indicator of good soil condition. And when it provides us with information "about plant stress". The main goal of our work was to compare the effect of different fertilizers application on development of arbuscular mycorrhizal colonization. We worked with organic fertilizers such as biochar from residual biomass, biochar from sewage sludge and ageing biochar and with mineral fertilizer DAM 390 (mixture of ammonium 25 %, nitrate 25 % and urea nitrogen 50 %). Effect of different types of the above fertilizers on development of arbuscular mycorrhizal colonization was tested by pot experiment with indicator plant Lactuca sativa L. The highest (P < 0.05) colonization of roots was found in variant with biochar from sewage sludge. The lower colonization was recognized in control variant and variant with addition of mineral fertilizer. Our results indicate positive effect of modified biochar application to soil on increase in level of arbuscular mycorrhizal colonization of roots.

Quantifying Sediment Transport in a Premontane Transitional Cloud Forest

NASA Astrophysics Data System (ADS)

Waring, E. R.; Brumbelow, J. K.

2013-12-01

Quantifying sediment transport is a difficult task in any watershed, and relatively little direct measurement has occurred in tropical, mountainous watersheds. The Howler Monkey Watershed (2.2 hectares) is located in a premontane transitional cloud forest in San Isidro de Peñas Blancas, Costa Rica. In June 2012, a V-notch stream-gaging weir was built in the catchment with a 8 ft by 6 ft by 4 ft concrete stilling basin. Sediment captured by the weir was left untouched for an 11 month time period. To collect the contents of the weir, the stream was rerouted and the weir was drained. The stilling basin contents were systematically sampled, and samples were taken to a lab and characterized using sieve and hydrometer tests. The wet volume of the remaining sediment was obtained, and dry mass was estimated. Particle size distribution of samples were obtained from lab tests, with 96% of sediment trapped by the weir being sand or coarser. The efficiency of the weir as a sediment collector was evaluated by comparing particle fall velocities to residence time of water in the weir under baseflow conditions. Under these assumptions, only two to three percent of the total mass of soil transported in the stream is thought to have been suspended in the water and lost over the V-notch. Data were compared to the Universal Soil Loss Equation (USLE), a widely accepted method for predicting soil loss in agricultural watersheds. As expected, application of the USLE to a tropical rainforest was problematic with uncertainty in parameters yielding a soil loss estimate varying by a factor of 50. Continued monitoring of sediment transport should yield data for improved methods of soil loss estimation applicable to tropical mountainous forests.

Quantifying the contribution of groundwater on water consumption in arid crop land with shallow groundwater

NASA Astrophysics Data System (ADS)

Huo, Z.; Liu, Z.; Wang, X.; Qu, Z.

2016-12-01

Groundwater from the shallow aquifers can supply substantial water for evapotranspiration of crops. However, it is difficult to quantify to the contribution of groundwater on crop's water consumption. In present study, regional scale evapotranspiration and the groundwater contribution to evapotranspiration were estimated by the soil water balance equation in Hetao irrigation distric with shallow aquifers, China. Estimates used an 8-year (2006-2013) hydrological dataset including soil moisture, the depth to water table, irrigation amounts, rainfall data, and drainage water flow. The 8-year mean evapotranspiration was estimated to be 664 mm. The mean groundwater supported evapotranspiration (ETg) was estimated to be 228 mm, with variation from 145 mm to 412 mm during the crop growth period. Analysis of the positive correlation between evapotranspiration and the sum of irrigation and rainfall, and the analysis of the negative correlation between ETg/ET and the sum of irrigation and rainfall, reflect the need of groundwater to meet the evapotranspiration demand. Approximately 20% to 40% of the evapotranspiration is from the shallow aquifers in the study area. Furthermore, a new method estimating daily ETg during the crop growing season was developed. The effects of crop growth stage, climate condition, groundwater depth and soil moisture are considered in the model. The method was tested with controlled lysimeter experiments of winter wheat including five controlled water table depths and four soil profiles of different textures. The simulated ETg is a good agreement with the measured data for four soil profiles and different depths to groundwater table. These results could be useful for the government to understand the significant role of the groundwater and make reasonable water use policy in the semiarid agricultural regions.

Litter quality versus soil microbial community controls over decomposition: a quantitative analysis

USGS Publications Warehouse

Cleveland, Cory C.; Reed, Sasha C.; Keller, Adrienne B.; Nemergut, Diana R.; O'Neill, Sean P.; Ostertag, Rebecca; Vitousek, Peter M.

2014-01-01

The possible effects of soil microbial community structure on organic matter decomposition rates have been widely acknowledged, but are poorly understood. Understanding these relationships is complicated by the fact that microbial community structure and function are likely to both affect and be affected by organic matter quality and chemistry, thus it is difficult to draw mechanistic conclusions from field studies. We conducted a reciprocal soil inoculum × litter transplant laboratory incubation experiment using samples collected from a set of sites that have similar climate and plant species composition but vary significantly in bacterial community structure and litter quality. The results showed that litter quality explained the majority of variation in decomposition rates under controlled laboratory conditions: over the course of the 162-day incubation, litter quality explained nearly two-thirds (64 %) of variation in decomposition rates, and a smaller proportion (25 %) was explained by variation in the inoculum type. In addition, the relative importance of inoculum type on soil respiration increased over the course of the experiment, and was significantly higher in microcosms with lower litter quality relative to those with higher quality litter. We also used molecular phylogenetics to examine the relationships between bacterial community composition and soil respiration in samples through time. Pyrosequencing revealed that bacterial community composition explained 32 % of the variation in respiration rates. However, equal portions (i.e., 16 %) of the variation in bacterial community composition were explained by inoculum type and litter quality, reflecting the importance of both the meta-community and the environment in bacterial assembly. Taken together, these results indicate that the effects of changing microbial community composition on decomposition are likely to be smaller than the potential effects of climate change and/or litter quality changes in response to increasing atmospheric CO2 concentrations or atmospheric nutrient deposition.

Assessment of tomato and wine processing solid wastes as soil amendments for biosolarization.

PubMed

Achmon, Yigal; Harrold, Duff R; Claypool, Joshua T; Stapleton, James J; VanderGheynst, Jean S; Simmons, Christopher W

2016-02-01

Pomaces from tomato paste and wine production are the most abundant fruit processing residues in California. These residues were examined as soil amendments for solarization to promote conditions conducive to soil disinfestation (biosolarization). Simulated biosolarization studies were performed in both aerobic and anaerobic soil environments and soil temperature elevation, pH, and evolution of CO2, H2 and CH4 gases were measured as metrics of soil microbial activity. Tomato pomace amendment induced conditions associated with soil pest inactivation, including elevation of soil temperature by up to 2°C for a duration of 4days under aerobic conditions and a reduction of soil pH from 6.5 to 4.68 under anaerobic conditions. White wine grape pomace amendment showed similar trends but to a lesser extent. Red wine grape pomace was generally less suitable for biosolarization due to significantly lower soil temperature elevations, reduced acidification relative to the other pomaces and induction of methanogenesis in the soil. Copyright © 2015 Elsevier Ltd. All rights reserved.

Introduced earthworm species exhibited unique patterns of seasonal activity and vertical distribution, and Lumbricus terrestris burrows remained usable for at least 7 years in hardwood and pine stands

Treesearch

Lynette R. Potvin; Erik A. Lilleskov

2017-01-01

It is difficult to obtain non-destructive information on the seasonal dynamics of earthworms in northern forest soils. To overcome this, we used a Rhizotron facility to compile 7 years of data on the activity of anecic (Lumbricus terrestris) and endogeic (Aporrectodea caliginosa complex) earthworms in two contrasting soil/plant...

Linking soils and streams: Response of soil solution chemistry to simulated hurricane disturbance mirrors stream chemistry following a severe hurricane

Treesearch

William H. McDowell; Daniel Liptzin

2014-01-01

Understanding the drivers of forest ecosystem response to major disturbance events is an important topic in forest ecology and ecosystem management. Because of the multiple elements included in most major disturbances such as hurricanes, fires, or landslides, it is often difficult to ascribe a specific driver to the observed response. This is particularly true for the...

Sugar beet factory lime affects the mobilization of Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn under dynamic redox conditions in a contaminated floodplain soil.

PubMed

Shaheen, Sabry M; Rinklebe, Jörg

2017-01-15

The impact of sugar beet factory lime (SBFL) on the release dynamics and mobilization of toxic metals (TMs) under dynamic redox conditions in floodplain soils has not been studied up to date. Therefore, the aim of this study was to verify the scientific hypothesis that SBFL is able to immobilize Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, and Zn under different redox potentials (E H ) in a contaminated floodplain soil. For this purpose, the non-treated contaminated soil (CS) and the same soil treated with SBFL (CS+SBFL) were flooded in the laboratory using a highly sophisticated automated biogeochemical microcosm apparatus. The experiment was conducted stepwise from reducing (-13 mV) to oxidizing (+519 mV) soil conditions. Soil pH decreased under oxic conditions in CS (from 6.9 to 4.0) and in CS+SBFL (from 7.5 to 4.4). The mobilization of Cu, Cr, Pb, and Fe were lower in CS+SBFL than in CS under both reducing/neutral and oxic/acidic conditions. Those results demonstrate that SBFL is able to decrease concentrations of these elements under a wide range of redox and pH conditions. The mobilization of Cd, Co, Mn, Mo, Ni, and Zn were higher in CS+SBFL than in CS under reducing/neutral conditions; however, these concentrations showed an opposite behavior under oxic/acidic conditions and were lower in CS+SBFL than in CS. We conclude that SBFL immobilized Cu, Cr, Pb, and Fe under dynamic redox conditions and immobilized Cd, Co, Mn, Mo, Ni, and Zn under oxic acidic conditions; however, the latter elements were mobilized under reducing neutral conditions in the studied soil. Therefore, the addition of SBFL to acid floodplain soils contaminated with TMs might be an important alternative for ameliorating these soils with view to a sustainable management of these soils. Copyright © 2016 Elsevier Ltd. All rights reserved.

Stable isotope-based approach to validate effects of understory vegetation on shallow soil water movement in a Japanese cypress plantation

NASA Astrophysics Data System (ADS)

Sakashita, W.; Onda, Y.; Boutefnouchet, M. R.; Kato, H.; Gomi, T.

2017-12-01

Evapotranspiration is an important controlling factor of the hydrological cycle in forested watershed. In general, the evapotranspiration is partitioned into three components (evaporation, transpiration, and interception). In a Japanese cypress plantation, our previous work using hydrometric method revealed that total evapotranspiration rate was 47.5% of the total rainfall amount during the growing season. This research also provided the contribution rates of three evapotranspiration components. Our previous study reported the difference of forest floor evaporation between pre-thinning and post-thinning periods (pre-thinning: Nov 2010-Oct 2011; post-thinning: Nov 2011-Oct 2012), indicating that a significant change appeared in the evaporation flux after the thinning. To examine the long-term changes of evapotranspiration, we have to consider the influence of increased understory vegetation. However, hydrometric-based method using such as weighting lysimeter is sensitive to vegetation conditions inside and outside lysimeter. This disadvantage makes it difficult to evaluate the contribution rates of each evapotranspiration components. In this study, we focus on the isotope-based method to obtain each flux of evapotranspiration under the condition including understory vegetation. Our study site is Mt. Karasawa, Tochigi Prefecture, in central Japan (139°36'E, 36°22'N; 198 m a.s.l.), and we prepare both sparse and dense areas of understory vegetation. In these two plots, we collect soil water samples from shallow depth profiles after various intensity precipitation events. Throughfall and understory-intercepted water are also obtained. Stable water isotope measurements of these samples may provide information about (a) effects of understory vegetation on shallow soil water movement and (b) interception flux of understory vegetation. In this paper, we report the results and interpretations of our measurements.

Characterizing hydrology and the importance of ground-water discharge in natural and constructed wetlands

USGS Publications Warehouse

Hunt, Randall J.; Walker, John F.; Krabbenhoft, David P.

1999-01-01

Although considered the most important component for the establishment and persistence of wetlands, hydrology has been hard to characterize and linkages between hydrology and other environmental conditions are often poorly understood. In this work, methods for characterizing a wetland’s hydrology from hydrographs were developed, and the importance of ground water to the physical and geochemical conditions in the root zone was investigated. Detailed sampling of nearly continuous hydrographs showed that sites with greater ground-water discharge had higher water tables and more stable hydrographs. Subsampling of the continuous hydrograph failed to characterize the sites correctly, even though the wetland complex is located in a strong regional ground-water-discharge area. By comparing soil-moisture-potential measurements to the water-table hydrograph at one site, we noted that the amount of root-zone saturation was not necessarily driven by the water-table hydrograph but can be a result of other soil parameters (i.e., soil texture and associated capillary fringe). Ground-water discharge was not a significant determinant of maximum or average temperatures in the root zone. High ground-water discharge was associated with earliest date of thaw and shortest period of time that the root zone was frozen, however. Finally, the direction and magnitude of shallow ground-water flow was found to affect the migration and importance of a geochemical species. Areas of higher ground-water discharge had less downward penetration of CO2 generated in the root zone. In contrast, biotically derived CO2 was able to penetrate the deeper ground-water system in areas of ground-water recharge. Although ground-water flows are difficult to characterize, understanding these components is critical to the success of wetland restoration and creation efforts.

Resampling soil profiles can constrain large-scale changes in the C cycle: obtaining robust information from radiocarbon measurements

NASA Astrophysics Data System (ADS)

Baisden, W. T.; Prior, C.; Lambie, S.; Tate, K.; Bruhn, F.; Parfitt, R.; Schipper, L.; Wilde, R. H.; Ross, C.

2006-12-01

Soil organic matter contains more C than terrestrial biomass and atmospheric CO2 combined, and reacts to climate and land-use change on timescales requiring long-term experiments or monitoring. The direction and uncertainty of soil C stock changes has been difficult to predict and incorporate in decision support tools for climate change policies. Moreover, standardization of approaches has been difficult because historic methods of soil sampling have varied regionally, nationally and temporally. The most common and uniform type of historic sampling is soil profiles, which have commonly been collected, described and archived in the course of both soil survey studies and research. Resampling soil profiles has considerable utility in carbon monitoring and in parameterizing models to understand the ecosystem responses to global change. Recent work spanning seven soil orders in New Zealand's grazed pastures has shown that, averaged over approximately 20 years, 31 soil profiles lost 106 g C m-2 y-1 (p=0.01) and 9.1 g N m{^-2} y-1 (p=0.002). These losses are unexpected and appear to extend well below the upper 30 cm of soil. Following on these recent results, additional advantages of resampling soil profiles can be emphasized. One of the most powerful applications afforded by resampling archived soils is the use of the pulse label of radiocarbon injected into the atmosphere by thermonuclear weapons testing circa 1963 as a tracer of soil carbon dynamics. This approach allows estimation of the proportion of soil C that is `passive' or `inert' and therefore unlikely to respond to global change. Evaluation of resampled soil horizons in a New Zealand soil chronosequence confirms that the approach yields consistent values for the proportion of `passive' soil C, reaching 25% of surface horizon soil C over 12,000 years. Across whole profiles, radiocarbon data suggest that the proportion of `passive' C in New Zealand grassland soil can be less than 40% of total soil C. Below 30 cm, 1 kg C m-2 or more may be reactive on decadal timescales, supporting evidence of soil C losses from throughout the soil profiles. Information from resampled soil profiles can be combined with additional contemporary measurements to test hypotheses about mechanisms for soil C changes. For example, Δ14C in excess of 200‰ in water extractable dissolved organic C (DOC) from surface soil horizons supports the hypothesis that decadal movement of DOC represents an important translocation of soil C. These preliminary results demonstrate that resampling whole soil profiles can support substantial progress in C cycle science, ranging from updating operational C accounting systems to the frontiers of research. Resampling can be complementary or superior to fixed-depth interval sampling of surface soil layers. Resampling must however be undertaken with relative urgency to maximize the potential interpretive power of bomb-derived radiocarbon.

Sensitivity analyses of a colloid-facilitated contaminant transport model for unsaturated heterogeneous soil conditions.

NASA Astrophysics Data System (ADS)

Périard, Yann; José Gumiere, Silvio; Rousseau, Alain N.; Caron, Jean

2013-04-01

Certain contaminants may travel faster through soils when they are sorbed to subsurface colloidal particles. Indeed, subsurface colloids may act as carriers of some contaminants accelerating their translocation through the soil into the water table. This phenomenon is known as colloid-facilitated contaminant transport. It plays a significant role in contaminant transport in soils and has been recognized as a source of groundwater contamination. From a mechanistic point of view, the attachment/detachment of the colloidal particles from the soil matrix or from the air-water interface and the straining process may modify the hydraulic properties of the porous media. Šimůnek et al. (2006) developed a model that can simulate the colloid-facilitated contaminant transport in variably saturated porous media. The model is based on the solution of a modified advection-dispersion equation that accounts for several processes, namely: straining, exclusion and attachement/detachement kinetics of colloids through the soil matrix. The solutions of these governing, partial differential equations are obtained using a standard Galerkin-type, linear finite element scheme, implemented in the HYDRUS-2D/3D software (Šimůnek et al., 2012). Modeling colloid transport through the soil and the interaction of colloids with the soil matrix and other contaminants is complex and requires the characterization of many model parameters. In practice, it is very difficult to assess actual transport parameter values, so they are often calibrated. However, before calibration, one needs to know which parameters have the greatest impact on output variables. This kind of information can be obtained through a sensitivity analysis of the model. The main objective of this work is to perform local and global sensitivity analyses of the colloid-facilitated contaminant transport module of HYDRUS. Sensitivity analysis was performed in two steps: (i) we applied a screening method based on Morris' elementary effects and the one-at-a-time approach (O.A.T); and (ii), we applied Sobol's global sensitivity analysis method which is based on variance decompositions. Results illustrate that ψm (maximum sorption rate of mobile colloids), kdmc (solute desorption rate from mobile colloids), and Ks (saturated hydraulic conductivity) are the most sensitive parameters with respect to the contaminant travel time. The analyses indicate that this new module is able to simulate the colloid-facilitated contaminant transport. However, validations under laboratory conditions are needed to confirm the occurrence of the colloid transport phenomenon and to understand model prediction under non-saturated soil conditions. Future work will involve monitoring of the colloidal transport phenomenon through soil column experiments. The anticipated outcome will provide valuable information on the understanding of the dominant mechanisms responsible for colloidal transports, colloid-facilitated contaminant transport and, also, the colloid detachment/deposition processes impacts on soil hydraulic properties. References: Šimůnek, J., C. He, L. Pang, & S. A. Bradford, Colloid-Facilitated Solute Transport in Variably Saturated Porous Media: Numerical Model and Experimental Verification, Vadose Zone Journal, 2006, 5, 1035-1047 Šimůnek, J., M. Šejna, & M. Th. van Genuchten, The C-Ride Module for HYDRUS (2D/3D) Simulating Two-Dimensional Colloid-Facilitated Solute Transport in Variably-Saturated Porous Media, Version 1.0, PC Progress, Prague, Czech Republic, 45 pp., 2012.

Effects of changing redox conditions on the dynamics of dissolved organic matter and CO2 in paddy soils

NASA Astrophysics Data System (ADS)

Hanke, Alexander; Cao, Zhi Hong; Liu, Qin; Muhr, Jan; Kalbitz, Karsten

2010-05-01

The current knowledge about dissolved organic matter (DOM) dynamics in soils and its dependence on different C pools based mainly on observations and experiments in aerobic environments. We have only a limited understanding about the effects of changing redox conditions on production and composition of DOM although this fraction of soil organic matter is important for greenhouse gas emission and carbon storage in soils. In many ecosystems temporal and spatial changes of oxic and anoxic conditions are evident and might even increase in future. It is assumed that changing redox conditions are the key drivers of DOM dynamics in such ecosystems. More detailed we tested the following hypotheses: Anoxic conditions result in relative DOM accumulation due to less mineralization of already produced DOM Close relationship between DOM production and CO2 emission 14C signature of CO2 enables the identification of different C pools degraded at oxic and anoxic conditions We chose paddy soils as a model ecosystem because these soils are anoxic during the rice growing period and oxic during harvest and growth of other crops. Furthermore, paddy soils have oxic and anoxic horizons. Soils of a unique chronosequence of paddy soil evolution (50 to 2000 years, China) were studied in direct comparison to non-paddy soils of the same age. In these soils, exposed to different redox conditions over defined periods of times, the dynamics of DOM, CO2, 14C of the CO2 and other redox sensitive elements were followed in laboratory experiments. In the latter redox conditions were changed every 3 weeks from oxic to anoxic and vice versa. Besides analysis of the composition of the soil solution and the gas phase we determined differences in C pools being respired at oxic and anoxic conditions by 14C AMS of the CO2. The measured redox potentials of -50 mV to 250mV at anoxic conditions and 350 mV to 550 mV at oxic conditions were in the expected range and proofed the appropriate setting of the chosen incubation method. PH values varied between 5.5 and 7.5, where anoxic samples had higher values than oxic ones. We further observed only small DOC contents of less than 1mg per g C. Under anoxic conditions as well as among the non-paddy soils DOC production was slightly higher than their respective counterparts. However, we could not find large effects of the time of rice cultivation. Nevertheless, the 2000 year old paddy soil showed highest DOC and CO2 production. The increase of DOC and CO2 production was strongest when the oxic period disrupted the anoxic conditions. 14C data revealed that CO2 respired from the 700 year old paddy soil was much older than from the 2000 year old paddy soil independently from redox condition. Furthermore, C mineralized at anoxic conditions was older than at oxic ones. During the incubation experiment the C consumption shifted from older pools to younger ones. We conclude that DOM accumulated at anoxic conditions will be quickly mineralized at oxic conditions. The influence of soil development on the C dynamics was less important than expected, thus fresh organic matter seems to play a more decisive role. The unexpected large decomposition of old organic matter at anoxic conditions hints to changes in the microbial community involved.

Physiological characteristics of tropical rain forest tree species: a basis for the development of silvicultural technology.

PubMed

Sasaki, Satohiko

2008-01-01

The physiological characteristics of the dominant tree species in the tropical rain forest mainly belonging to dipterocarps as well as the environmental conditions especially for the light in the forest were studied to establish the silvicultural system for the forest regeneration in the tropical South Asia. The flowering patterns of the dipterocarp trees are usually irregular and unpredictable, which make difficult to collect sufficient seeds for raising the seedlings. The field survey revealed the diverged features of the so-called gregarious or simultaneous flowering of various species of this group. Appropriate conditions and methods for the storage of the seeds were established according to the detailed analyses of the morphological and physiological characteristics of the seeds such as the low temperature tolerance and the moisture contents. The intensity and spectra of the light in the forest primarily determine the growth and the morphological development of the seedlings under the canopy. Based on the measurements of the diffused light at the sites in the tropical forest in the varying sunlight, the parameters such as "the steady state of the diffuse light" and "the turning point" were defined, which were useful to evaluate the light conditions in the forest. To improve the survival of the transplanted seedlings, a planting method of "the bare-root seedlings", the seedlings easy to be handled by removal of all leaves, soil and pots, was developed. Its marked efficiency was proved with various dipterocarps and other tropical trees by the field trial in the practical scale. Tolerance of the various species to the extreme environmental conditions such as fires, acid soils and drought were examined by the experiments and the field survey, which revealed marked adaptability of Shorea roxburghii as a potential species for regeneration of the tropical forests.

[Response of mineralization of dissolved organic carbon to soil moisture in paddy and upland soils in hilly red soil region].

PubMed

Chen, Xiang-Bi; Wang, Ai-Hua; Hu, Le-Ning; Huang, Yuan; Li, Yang; He, Xun-Yang; Su, Yi-Rong

2014-03-01

Typical paddy and upland soils were collected from a hilly subtropical red-soil region. 14C-labeled dissolved organic carbon (14C-DOC) was extracted from the paddy and upland soils incorporated with 14C-labeled straw after a 30-day (d) incubation period under simulated field conditions. A 100-d incubation experiment (25 degrees C) with the addition of 14C-DOC to paddy and upland soils was conducted to monitor the dynamics of 14C-DOC mineralization under different soil moisture conditions [45%, 60%, 75%, 90%, and 105% of the field water holding capacity (WHC)]. The results showed that after 100 days, 28.7%-61.4% of the labeled DOC in the two types of soils was mineralized to CO2. The mineralization rates of DOC in the paddy soils were significantly higher than in the upland soils under all soil moisture conditions, owing to the less complex composition of DOC in the paddy soils. The aerobic condition was beneficial for DOC mineralization in both soils, and the anaerobic condition was beneficial for DOC accumulation. The biodegradability and the proportion of the labile fraction of the added DOC increased with the increase of soil moisture (45% -90% WHC). Within 100 days, the labile DOC fraction accounted for 80.5%-91.1% (paddy soil) and 66.3%-72.4% (upland soil) of the cumulative mineralization of DOC, implying that the biodegradation rate of DOC was controlled by the percentage of labile DOC fraction.

Regulation of stream water dissolved organic carbon concentrations ([DOC]) during snowmelt in forest streams; the role of discharge, winter climate and memory effects

NASA Astrophysics Data System (ADS)

Ågren, A.; Haei, M.; Öquist, M.; Buffam, I.; Ottosson-Löfvenius, M.; Kohler, S.; Bishop, K.; Blomkvist, P.; Laudon, H.

2011-12-01

Using 15 year stream records from two forested northern boreal catchments, coupled with soil frost experiments in the riparian zone, we demonstrate the complex inter-annual control on [DOC] and export during snowmelt. Stream [DOC] varied by a factor of 2 during those 15 years with no consistent trend. Based on our long-term analysis, we demonstrate, for the first time, that stream water [DOC] is strongly linked to the climatic conditions during the preceding winter, but that there is also a long-term memory effect in the catchment soils, related to the extent of the previous export from the catchment. Hydrology had a first order control on the inter-annual variation in concentrations, and the length of the winter was more important than the memory effect. By removing the effect of discharge on [DOC], using a conceptual hydrological model, we could detect processes that would otherwise have been overshadowed. A short and intense snowmelt gave higher [DOC] in the stream. During a prolonged snowmelt, one soil layer at the time might have been "flushed" from easily exported DOC, resulting in slightly lower stream [DOC] during such years. We found that longer and colder winters resulted in higher [DOC] during the subsequent snowmelt. A soil frost manipulation experiment in the riparian soils of the study catchment showed that the DOC concentrations in the soil water increased with the duration of the soil frost. A high antecedent DOC export during the preceding summer and autumn resulted in lower concentrations during the following spring, indicating a long-term "memory effect" of the catchment soils. In a nearby stream draining mire, we found a different response to hydrology but similar response to climate and memory effect. The inter-annual variation in snowmelt DOC exports was mostly controlled by the amount of runoff, but the variability in [DOC] also exerted a significant control on the exports, accounting for 15% of the variance in exports. We conclude that winter climatic conditions can play a substantial role in controlling stream [DOC] in ways not previously understood. These findings are especially important for northern latitude regions expected to be most affected by climate change. It's difficult to directly translate this to a future climate change prediction. If warmer winters with less insulating snow cover increase the soil frost, the results from the soil frost manipulation experiment then suggest increasing [DOC] in a future climate. At the same time the statistical analysis of the stream records suggest that a shorter and warmer winter would decrease the [DOC]. Our results do, however, highlight the role of winter climate for regulating DOC in areas with seasonally frozen soils which should be considered when resolving the sensitivity of stream [DOC] to global environmental change.

Effects of redox conditions on the adsorption of dissolved organic matter to soil minerals and differently aged paddy soils

NASA Astrophysics Data System (ADS)

Sauerwein, Meike; Hanke, Alexander; Kaiser, Klaus; Kalbitz, Karsten

2010-05-01

Effects of redox conditions on the adsorption of dissolved organic matter to soil minerals and differently aged paddy soils Meike Sauerwein1, Alexander Hanke2, Klaus Kaiser3, Karsten Kalbitz2 1) Dept. of Soil Ecology, Bayreuth Centre of Ecology and Environmental Research (BayCEER), University of Bayreuth, 95440 Bayreuth, Germany, meike.sauerwein@gmail.com 2) Institute of ecosystem dynamics and biodiversity, University of Amsterdam, 1018 WV, Netherlands, a.hanke@uva.nl, k.kalbitz@uva.nl 3) Soil Sciences, Martin Luther University Halle, 06099 Halle, Germany, klaus.kaiser@landw.uni-halle.de Current knowledge on dissolved organic matter (DOM) in soils is based mainly on observations and experiments in aerobic environments. Adsorption to soil minerals is an important mechanism of DOM retention and stabilization against microbial decay under oxic conditions. Under anoxic conditions where hydrous iron oxides, the potential main adsorbents of DOM, possibly dissolve, the importance of adsorption seems questionable. Therefore, we studied the adsorption of DOM to selected soil minerals and to mineral soils under oxic and anoxic conditions. In detail, we tested the following hypotheses: 1. Minerals and soils adsorb less DOM under anoxic conditions than under oxic ones. 2. The reduced adsorption under anoxic conditions is result of the smaller adsorption to hydrous Fe oxides whereas adsorption to clay minerals and Al hydroxides is not sensitive to changes in redox conditions 3. DOM adsorption will increase with the number of redox cycles, thus time of soil formation, due to increasing contents of poorly crystalline Fe oxides. This will, however, cause a stronger sensitivity to redox changes as poor crystalline Fe oxides are more reactive. 4. Aromatic compounds, being preferentially adsorbed under oxic conditions, will be less strongly adsorbed under anoxic conditions. We chose paddy soils as models because their periodically and regular exposure to changing redox cycles, with anoxic conditions during the rice growing period and oxic conditions during harvest and growth of other crops. Soils of a unique chronosequence of paddy soils (50, 300, 700 and 2000 years) in China were studied in direct comparison to non-paddy soils of the same age. In additions, selected soil minerals (goethite, ferrihydrite, amorphous Al hydroxide, hydrobiotite, nontronite and ripodolite), differing in their response to changes in redox conditions, were studied in order to indentify those mineral constituents responsible for redox-induced changes in DOM adsorption to the test soils. The DOM for the adsorption was extracted from composted rice straw as a surrogate for DOM percolating in paddy soils. Batch adsorption experiments were carried out with DOM pre-incubated to give oxic and anoxic conditions and maintaining these redox conditions during the whole procedure. The redox potential resulting from anoxic pre-incubation was about 100 mV, thus in the range of Fe reduction. Besides of dissolved organic carbon (DOC), we determined changes in the composition of DOM by the specific UV absorbance. We also analyzed main cations, anions and redox-sensitive elements to give a comprehensive picture of the effects of changing redox conditions on the dynamics of organic C, N, P, S, Fe and Al. First results indicated indeed less adsorption of DOM to Fe oxides under anoxic than under oxic conditions, with a more pronounced effect for ferrihydrite than for goethite. Maximum adsorption of DOM was more than 50% larger under oxic than under anoxic conditions. The effect was less pronounced but still detectable for clay minerals such as hydrobiotite, nontronite, and ripodolite. The specific UV absorbance of DOM contact with minerals was 20-50% stronger under anoxic than under oxic conditions. These changes in DOM composition indicated that preferential adsorption of aromatic compounds might be limited to aerated soils. We conclude that adsorption, although less strong than under oxic conditions, is an important mechanism of DOM retention also under anoxic conditions. Decreasing amounts of adsorbed DOM and changes in its composition might result in a less effective sorptive stabilization against microbial decay under anoxic than under oxic conditions.

Long-term experiments to better understand soil-human interactions

NASA Astrophysics Data System (ADS)

Bormann, B. T.; Homann, P. S.

2011-12-01

Interactions between soils and people may be transforming global conditions, but the interactions are poorly understood. Changes in soils have proven difficult to quantify, especially in complex ecosystems manifesting large spatiotemporal variability. Long-term ecosystem experiments that evaluate soil change and demonstrate alternative choices are important to understanding changes, discovering new controls and drivers, and influencing decisions. Inspired by agriculture studies, like Rothamsted, the US Forest Service established in 1990 a network of operational-scale experiments across the Pacific Northwest to evaluate long-term effects of different forest management and disturbance regimes. With a strong experimental design, these experiments are now helping to better understand the long-term effects of managing tree harvesting (clearcutting and thinning), woody debris, and tree and understory species composition, and-serendipitously-the effects of fire. Initial results from the Southern Oregon experimental site indicate surprisingly rapid soil changes in some regimes but not others. We've also learned that rapid change presents challenges to repeat sampling. We present our sample-archive and comparable-layer approaches that seek to accommodate changes in surface elevation, aggregation and disaggregation, and mineral-soil exports. Thinning mature forest stands (80-100 yrs old) did not significantly change soil C in 11-yrs. A small upper-layer C increase was observed after thinning, but it was similar to the control. Significant increases in upper-layer soil N were observed with most treatments, but all increases were similar to the control. Leaving woody debris had little effect. The most remarkable change occurred when mature stands were clearcut and Douglas-firs were planted and tended. Associated with rapid growth of Douglas-fir, an average of 8 Mg C ha-1 was lost from weathered soil 4-18 cm deep. This contrasts with clearcuts where early-seral hardwoods and knobcone pines were established, that trended positively with 2 Mg C ha-1. Soil changes resulting from wild and prescribed fire were substantial. About 50% of the soil C (3-21 Mg ha-1) and 36% of soil N (41-650 kg ha-1) were lost from the upper profile (0-6.2 cm) compared to pre-fire conditions. Intense wildfire that killed most forest trees had about double the losses of C and N than forests burned at lower temperature with fewer trees killed. Average wildfire C losses were more than twice prescribed-fire losses. A long-term perspective is needed to compare episodic influences on soils, like harvesting and wildfire, to day-in, day-out effects of different species mixtures. Especially important is the effect of shrubs, that can rapidly achieve full leaf area but that lack the woody stem structure to store captured C as well as conifers. In theory, therefore, extending shrub cover will increase soil C. The annual profile soil C loss in Douglas-fir (-0.8 Mg ha-1yr-1), if continued beyond 11 yrs, would be similar to the effects of a fire-return interval of less than a third of the historical interval of about 100 years. National and regional soil-C monitoring would benefit from being grounded in existing experimental studies to help integrate large-scale changes with an unfolding understanding of processes in ways useful to decisionmakers.

Plan of research for integrated soil moisture studies. Recommendations of the Soil Moisture Working Group

NASA Technical Reports Server (NTRS)

1980-01-01

Soil moisture information is a potentially powerful tool for applications in agriculture, water resources, and climate. At present, it is difficult for users of this information to clearly define their needs in terms of accuracy, resolution and frequency because of the current sparsity of data. A plan is described for defining and conducting an integrated and coordinated research effort to develop and refine remote sensing techniques which will determine spatial and temporal variations of soil moisture and to utilize soil moisture information in support of agricultural, water resources, and climate applications. The soil moisture requirements of these three different application areas were reviewed in relation to each other so that one plan covering the three areas could be formulated. Four subgroups were established to write and compile the plan, namely models, ground-based studies, aircraft experiments, and spacecraft missions.

An analysis of soil moisture and vegetation conditions during a period of rapid subseasonal oscillations between drought and pluvials over Texas during 2015

NASA Astrophysics Data System (ADS)

Hunt, E. D.; Otkin, J.; Zhong, Y.

2017-12-01

Flash drought, characterized by the rapid onset of abnormally warm and dry weather conditions that leads to the rapid depletion of soil moisture and rapid deteriorations in vegetation health. Flash recovery, on the other hand, is characterized by a period(s) of intense precipitation where drought conditions are quickly eradicated and may be replaced by saturated soils and flooding. Both flash drought and flash recovery are closely tied to the rapid depletion or recharge of root zone soil moisture; therefore, soil moisture observations are very useful for monitoring their evolution. However, in-situ soil moisture observations tend to be concentrated over small regions and thus other methods are needed to provide a spatially continuous depiction of soil moisture conditions. One option is to use top soil moisture retrievals from the Soil Moisture Active Passive (SMAP) sensor. SMAP provides routine coverage of surface soil moisture (0-5 cm) over most of the globe, including the timespan (2015) and region of interest (Texas) that are the focus of our study. This region had an unusual sequence of flash recovery-flash drought-flash recovery during an six-month period during 2015 that provides a valuable case study of rapid transitions between extreme soil moisture conditions. During this project, SMAP soil moisture retrievals are being used in combination with in-situ soil moisture observations and assimilated into the Land Information System (LIS) to provide information about soil moisture content. LIS also provides greenness vegetation fraction data over large regions. The relationship between soil moisture and vegetation conditions and the response of the vegetation to the rapidly changing conditions are also assessed using the satellite thermal infrared based Evaporative Stress Index (ESI) that depicts anomalies in evapotranspiration, along with other vegetation datasets (leaf area index, greenness fraction) derived using MODIS observations. Preliminary results with the Noah land surface model (inside of LIS) shows that it broadly captured the soil moisture evolution during the 2015 sequence but tended to underestimate the magnitude of soil moisture anomalies. The ESI also showed negative anomalies during the drought. These and other results will be presented at the annual meeting.

Evaluating time dynamics of topographic threshold relations for gully initiation

NASA Astrophysics Data System (ADS)

Hayas, Antonio; Vanwalleghem, Tom; Poesen, Jean

2016-04-01

Gully erosion is one of the most important soil degradation processes at global scale. However, modelling of gully erosion is still difficult. Despite advances in the modelling of gully headcut rates and incision rates, it remains difficult to predict the location of gully initiation points and trajectories. In different studies it has been demonstrated that a good method of predicting gully initiation is by using a slope (S) - area (A) threshold. Such an S-A relation is a simple way of estimating the critical discharges needed to generate a critical shear stress that can incise a particular soil and initiate a gully. As such, the simple S-A threshold will vary if the rainfall-runoff behaviour of the soil changes or if the soil's erodibility changes. Over the past decades, important agronomic changes have produced significant changes in the soil use and soil management in SW Spain. It is the objective of this research to evaluate how S-A relations for gully initiation have changed over time and for two different land uses, cereal and olive. Data was collected for a gully network in the Cordoba Province, SW Spain. From photo-interpretation of historical air photos between 1956 and 2013, the gully network and initiation points were derived. In total 10 different time steps are available (1956; 1977; 1984; 1998; 2001; 2004; 2006; 2008; 2010; 2013). Topographical thresholds were extracted by combining the digitized gully network with the DEM. Due to small differences in the alignment of ortophotos and DEM, an optimization technique was developed in GIS to extract the correct S-A value for each point. With the S-A values for each year, their dynamics was evaluated as a function of land use (olive or cereal) and in function of the following variables in each of the periods considered: • soil management • soil cover by weeds, where weed growth was modeled from the daily soil water balance • rainfall intensity • root cohesion, , where root growth was modeled from the daily soil water balance We found important differences between cereal and olive and significant changes in the S-A relation over time.

Effects of Long-Term CO2 Enrichment on Soil-Atmosphere CH4 Fluxes and the Spatial Micro-Distribution of Methanotrophic Bacteria.

PubMed

Karbin, Saeed; Guillet, Cécile; Kammann, Claudia I; Niklaus, Pascal A

2015-01-01

Effects of elevated atmospheric CO2 concentrations on plant growth and associated C cycling have intensively been studied, but less is known about effects on the fluxes of radiatively active trace gases other than CO2. Net soil-atmosphere CH4 fluxes are determined by the balance of soil microbially-driven methane (CH4) oxidation and methanogenesis, and both might change under elevated CO2. Here, we studied CH4 dynamics in a permanent grassland exposed to elevated CO2 for 14 years. Soil-atmosphere fluxes of CH4 were measured using large static chambers, over a period of four years. The ecosystem was a net sink for atmospheric CH4 for most of the time except summer to fall when net CH4 emissions occurred. We did not detect any elevated CO2 effects on CH4 fluxes, but emissions were difficult to quantify due to their discontinuous nature, most likely because of ebullition from the saturated zone. Potential methanotrophic activity, determined by incubation of fresh sieved soil under standardized conditions, also did not reveal any effect of the CO2 treatment. Finally, we determined the spatial micro-distribution of methanotrophic activity at less than 5× atmospheric (10 ppm) and elevated (10000 ppm) CH4 concentrations, using a novel auto-radiographic technique. These analyses indicated that domains of net CH4 assimilation were distributed throughout the analyzed top 15 cm of soils, with no dependence on CH4 concentration or CO2 treatment. Our investigations suggest that elevated CO2 exerts no or only minor effects on CH4 fluxes in the type of ecosystem we studied, at least as long as soil moisture differences are small or absent as was the case here. The autoradiographic analyses further indicate that the spatial niche of CH4 oxidation does not shift in response to CO2 enrichment or CH4 concentration, and that the same type of methanotrophs may oxidize CH4 from atmospheric and soil-internal sources.

Experimental and numerical study of two dimensional heat and mass transfer in unsaturated soil with and application to soil thermal energy storage (SBTES) systems

NASA Astrophysics Data System (ADS)

Moradi, A.; Smits, K. M.

2014-12-01

A promising energy storage option to compensate for daily and seasonal energy offsets is to inject and store heat generated from renewable energy sources (e.g. solar energy) in the ground, oftentimes referred to as soil borehole thermal energy storage (SBTES). Nonetheless in SBTES modeling efforts, it is widely recognized that the movement of water vapor is closely coupled to thermal processes. However, their mutual interactions are rarely considered in most soil water modeling efforts or in practical applications. The validation of numerical models that are designed to capture these processes is difficult due to the scarcity of experimental data, limiting the testing and refinement of heat and water transfer theories. A common assumption in most SBTES modeling approaches is to consider the soil as a purely conductive medium with constant hydraulic and thermal properties. However, this simplified approach can be improved upon by better understanding the coupled processes at play. Consequently, developing new modeling techniques along with suitable experimental tools to add more complexity in coupled processes has critical importance in obtaining necessary knowledge in efficient design and implementation of SBTES systems. The goal of this work is to better understand heat and mass transfer processes for SBTES. In this study, we implemented a fully coupled numerical model that solves for heat, liquid water and water vapor flux and allows for non-equilibrium liquid/gas phase change. This model was then used to investigate the influence of different hydraulic and thermal parameterizations on SBTES system efficiency. A two dimensional tank apparatus was used with a series of soil moisture, temperature and soil thermal properties sensors. Four experiments were performed with different test soils. Experimental results provide evidences of thermally induced moisture flow that was also confirmed by numerical results. Numerical results showed that for the test conditions applied here, moisture flow is more influenced by thermal gradients rather than hydraulic gradients. The results also demonstrate that convective fluxes are higher compared to conductive fluxes indicating that moisture flow has more contribution to the overall heat flux than conductive fluxes.

Deployment Area Selection and Land Withdrawal/Acquisition. M-X/MPS (M-X/Multiple Protective Shelter) Environmental Technical Report. Mitigations.

DTIC Science & Technology

1981-10-02

structure. Compacted soils are difficult to revegetate without adequate treatment . In addition, compacted soils have lower infiltration rates * which result...Reno, Nevada. August 1976). Erosion and sediment can be controlled on construction sites if certain principles are followed in the use of treatment of...If successful erosion control treatment is applied to the land in the watershed, sediment production can be reduced to

Transpiration and root development of urban trees in structural soil stormwater reservoirs.

PubMed

Bartens, Julia; Day, Susan D; Harris, J Roger; Wynn, Theresa M; Dove, Joseph E

2009-10-01

Stormwater management that relies on ecosystem processes, such as tree canopy interception and rhizosphere biology, can be difficult to achieve in built environments because urban land is costly and urban soil inhospitable to vegetation. Yet such systems offer a potentially valuable tool for achieving both sustainable urban forests and stormwater management. We evaluated tree water uptake and root distribution in a novel stormwater mitigation facility that integrates trees directly into detention reservoirs under pavement. The system relies on structural soils: highly porous engineered mixes designed to support tree root growth and pavement. To evaluate tree performance under the peculiar conditions of such a stormwater detention reservoir (i.e., periodically inundated), we grew green ash (Fraxinus pennsylvanica Marsh.) and swamp white oak (Quercus bicolor Willd.) in either CUSoil or a Carolina Stalite-based mix subjected to three simulated below-system infiltration rates for two growing seasons. Infiltration rate affected both transpiration and rooting depth. In a factorial experiment with ash, rooting depth always increased with infiltration rate for Stalite, but this relation was less consistent for CUSoil. Slow-drainage rates reduced transpiration and restricted rooting depth for both species and soils, and trunk growth was restricted for oak, which grew the most in moderate infiltration. Transpiration rates under slow infiltration were 55% (oak) and 70% (ash) of the most rapidly transpiring treatment (moderate for oak and rapid for ash). We conclude this system is feasible and provides another tool to address runoff that integrates the function of urban green spaces with other urban needs.

Characterization of Trapped Lignin-Degrading Microbes in Tropical Forest Soil

PubMed Central

DeAngelis, Kristen M.; Allgaier, Martin; Chavarria, Yaucin; Fortney, Julian L.; Hugenholtz, Phillip; Simmons, Blake; Sublette, Kerry; Silver, Whendee L.; Hazen, Terry C.

2011-01-01

Lignin is often the most difficult portion of plant biomass to degrade, with fungi generally thought to dominate during late stage decomposition. Lignin in feedstock plant material represents a barrier to more efficient plant biomass conversion and can also hinder enzymatic access to cellulose, which is critical for biofuels production. Tropical rain forest soils in Puerto Rico are characterized by frequent anoxic conditions and fluctuating redox, suggesting the presence of lignin-degrading organisms and mechanisms that are different from known fungal decomposers and oxygen-dependent enzyme activities. We explored microbial lignin-degraders by burying bio-traps containing lignin-amended and unamended biosep beads in the soil for 1, 4, 13 and 30 weeks. At each time point, phenol oxidase and peroxidase enzyme activity was found to be elevated in the lignin-amended versus the unamended beads, while cellulolytic enzyme activities were significantly depressed in lignin-amended beads. Quantitative PCR of bacterial communities showed more bacterial colonization in the lignin-amended compared to the unamended beads after one and four weeks, suggesting that the lignin supported increased bacterial abundance. The microbial community was analyzed by small subunit 16S ribosomal RNA genes using microarray (PhyloChip) and by high-throughput amplicon pyrosequencing based on universal primers targeting bacterial, archaeal, and eukaryotic communities. Community trends were significantly affected by time and the presence of lignin on the beads. Lignin-amended beads have higher relative abundances of representatives from the phyla Actinobacteria, Firmicutes, Acidobacteria and Proteobacteria compared to unamended beads. This study suggests that in low and fluctuating redox soils, bacteria could play a role in anaerobic lignin decomposition. PMID:21559391

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

Phytostabilization of arsenic in soils with plants of the genus Atriplex established in situ in the Atacama Desert.

PubMed

Fernández, Yasna Tapia; Diaz, O; Acuña, E; Casanova, M; Salazar, O; Masaguer, A

2016-04-01

In the ChiuChiu village (Atacama Desert, Chile), there is a high concentration of arsenic (As) in the soil due to natural causes related to the presence of volcanoes and geothermal activity. To compare the levels of As and the growth parameters among plants of the same genus, three species of plants were established in situ: Atriplex atacamensis (native of Chile), Atriplex halimus, and Atriplex nummularia. These soils have an As concentration of 131.2 ± 10.4 mg kg(-1), a pH of 8.6 ± 0.1, and an electrical conductivity of 7.06 ± 2.37 dS m(-1). Cuttings of Atriplex were transplanted and maintained for 5 months with periodic irrigation and without the addition of fertilizers. The sequential extraction of As indicated that the metalloid in these soils has a high bioavailability (38 %), which is attributed to the alkaline pH, low organic matter and Fe oxide content, and sandy texture. At day 90 of the assay, the As concentrations in the leaves of A. halimus (4.53 ± 1.14 mg kg(-1)) and A. nummularia (3.85 ± 0.64 mg kg(-1)) were significantly higher than that in A. atacamensis (2.46 ± 1.82 mg kg(-1)). However, the three species accumulated higher levels of As in their roots, indicating a phytostabilization capacity. At the end of the assay, A. halimus and A. nummularia generated 30 % more biomass than A. atacamensis without significant differences in the As levels in the leaves. Despite the difficult conditions in these soils, the establishment of plants of the genus Atriplex is a recommended strategy to generate a vegetative cover that prevents the metalloid from spreading in this arid area through the soil or by wind.

Better to light a candle than curse the darkness: illuminating spatial localization and temporal dynamics of rapid microbial growth in the rhizosphere

PubMed Central

Herron, Patrick M.; Gage, Daniel J.; Arango Pinedo, Catalina; Haider, Zane K.; Cardon, Zoe G.

2013-01-01

The rhizosphere is a hotbed of microbial activity in ecosystems, fueled by carbon compounds from plant roots. Basic questions about the location and dynamics of plant-spurred microbial growth in the rhizosphere are difficult to answer with standard, destructive soil assays mixing a multitude of microbe-scale microenvironments in a single, often sieved, sample. Soil microbial biosensors designed with the luxCDABE reporter genes fused to a promoter of interest enable continuous imaging of the microbial perception of (and response to) environmental conditions in soil. We used the common soil bacterium Pseudomonas putida KT2440 as host to plasmid pZKH2 containing a fusion between the strong constitutive promoter nptII and luxCDABE (coding for light-emitting proteins) from Vibrio fischeri. Experiments in liquid media demonstrated that high light production by KT2440/pZKH2 was associated with rapid microbial growth supported by high carbon availability. We applied the biosensors in microcosms filled with non-sterile soil in which corn (Zea mays L.), black poplar (Populus nigra L.), or tomato (Solanum lycopersicum L.) was growing. We detected minimal light production from microbiosensors in the bulk soil, but biosensors reported continuously from around roots for as long as six days. For corn, peaks of luminescence were detected 1–4 and 20–35 mm along the root axis behind growing root tips, with the location of maximum light production moving farther back from the tip as root growth rate increased. For poplar, luminescence around mature roots increased and decreased on a coordinated diel rhythm, but was not bright near root tips. For tomato, luminescence was dynamic, but did not exhibit a diel rhythm, appearing in acropetal waves along roots. KT2440/pZKH2 revealed that root tips are not always the only, or even the dominant, hotspots for rhizosphere microbial growth, and carbon availability is highly variable in space and time around roots. PMID:24032034

The effect of environmental conditions and soil physicochemistry on phosphate stabilisation of Pb in shooting range soils.

PubMed

Sanderson, Peter; Naidu, Ravi; Bolan, Nanthi

2016-04-01

The stabilisation of Pb in the soil by phosphate is influenced by environmental conditions and physicochemical properties of the soils to which it is applied. Stabilisation of Pb by phosphate was examined in four soils under different environmental conditions. The effect of soil moisture and temperature on stabilisation of Pb by phosphate was examined by measurement of water extractable and bioaccessible Pb, sequential fractionation and X-ray absorption spectroscopy. The addition of humic acid, ammonium nitrate and chloride was also examined for inhibition or improvement of Pb stability with phosphate treatment. The effect of moisture level varied between soils. In soil MB and DA a soil moisture level of 50% water holding capacity was sufficient to maximise stabilisation of Pb, but in soil TV and PE reduction in bioaccessible Pb was inhibited at this moisture level. Providing moisture at twice the soil water holding capacity did not enhance the effect of phosphate on Pb stabilisation. The difference of Pb stability as a result of incubating phosphate treated soils at 18 °C and 37 °C was relatively small. However wet-dry cycles decreased the effectiveness of phosphate treatment. The reduction in bioaccessible Pb obtained was between 20 and 40% with the most optimal treatment conditions. The reduction in water extractable Pb by phosphate was substantial regardless of incubation conditions and the effect of different temperature and soil moisture regimes was not significant. Selective sequential extraction showed phosphate treatment converted Pb in fraction 1 (exchangeable, acid and water soluble) to fraction 2 (reducible). There were small difference in fraction 4 (residual) Pb and fraction 1 as a result of treatment conditions. X-ray absorption spectroscopy of stabilised PE soil revealed small differences in Pb speciation under varying soil moisture and temperature treatments. The addition of humic acid and chloride produced the greatest effect on Pb speciation in phosphate treated soils. Crown Copyright © 2016. Published by Elsevier Ltd. All rights reserved.

Selective Separation and Determination of Heavy Metals (Cd, Pb, Cr) Speciation Forms from Hortic Antrosols

NASA Astrophysics Data System (ADS)

Bulgariu, D.; Bulgariu, L.

2009-04-01

The speciation, inter-phases distribution and biodisponibility of heavy metals in soils represent one of main problem of environmental geochemistry and agro-chemistry. This problem is very important in case of hortic antrosols (soils from glasshouses) for the elimination of agricultural products (fruits, vegetables) contamination with heavy metals. In soils from glass houses, the speciation and inter-phases distribution processes of heavy metals have a particular dynamic, different in comparison with those from non-protected soils. The predominant distribution forms of heavy metals in such soils types are: complexes with low mass organic molecules, organic-mineral complexes, complexes with inorganic ligands (hydroxide-complexes, carbonate-complexes, sulphate-complexes, etc.) and basic salts. All of these have high stabilities in conditions of soils from glass houses, and in consequence, the separation and determination of speciation forms (which is directly connected with biodisponibility of heavy metals) by usual methods id very difficult and has a high uncertain degree. In this study is presented an original method for the selective separation and differentiation of speciation forms of heavy metals from glass houses soils, which is based by the combination of solid-liquid sequential extraction (SPE) with the extraction in aqueous polymer-inorganic salt two-phase systems (ABS). The soil samples used for this study have been sampled from three different locations (glass houses from Iasi, Barlad and Bacau - Romania) where the vegetables cultivation have bee performed by three different technologies. In this way was estimated the applicability and the analytical limits of method proposed by as, in function of the chemical-mineralogical and physical-chemical characteristics of soils. As heavy metals have been studied cadmium, lead and chromium, all being known for their high toxicity. The procedure used for the selective separation and differentiation of speciation forms of heavy metals from glass houses soils has two main steps: (i) non-destructive separation of chemical-mineralogical associations and aggregates from soils samples - for this the separation method with heavy liquids (bromophorme) and isodynamic magnetic method have been used; (ii) sequential extraction of heavy metals from soil fractions separated in the first step, by using combined SPE-ABS procedure. For the preparation of combined extraction systems was used polyethylene glycol (with different molecular mass: 2000, 4000 and 8000). As phase-forming inorganic salts and as selective extracting agents we have used different usual inorganic reagents. The type and concentration of phase-forming salts have been selected in function of, both nature of extracted heavy metals and chemical-mineralogical characteristics of soil samples. The experimental parameters investigated in this study are: molecular mass of polyethylene glycol and the concentration of polymeric solutions, nature and concentration of phase-forming salts, nature and concentration of extracting agents, pH in extraction system phase, type of extracted heavy metals, type of speciation forms of heavy metals and their concentrations. All these factors can influence significantly the efficiency and the selectivity of separation process. The experimental results have indicate that the combined SPE-ABS extraction systems have better separation efficiency, in comparison with traditional SPE systems and ca realized a accurate discrimination between speciation forms of heavy metals from soils. Under these conditions, the estimation of inter-phases distribution and biodisponibility of heavy metals has a high precision. On the other hand, when the combined SPE-ABS systems are used, the concomitant extraction of the elements from the same geochemical association with studied heavy metals (inevitable phenomena in case of separation by SPE procedures) is significant diminished. This increases the separation selectivity and facilitated the more accurate determination of speciation forms concentration. By adequate selection of extraction conditions can be realized the selective separation of organic-mineral complexes, which will permit to perform detailed studies about the structure and chemical composition of these. Acknowledgments The authors would like to acknowledge the financial support from Romanian Ministry of Education and Research (Project PNCDI 2-D5 no. 51045/07).

Repression of fungal plant pathogens and fungal-related contaminants: Selected ecosystem services by soil fauna communities in agroecosystems

NASA Astrophysics Data System (ADS)

Meyer-Wolfarth, Friederike; Schrader, Stefan; Oldenburg, Elisabeth; Brunotte, Joachim; Weinert, Joachim

2017-04-01

In agroecosystems soil-borne fungal plant diseases are major yield-limiting factors which are difficult to control. Fungal plant pathogens, like Fusarium species, survive as a saprophyte in infected tissue like crop residues and endanger the health of the following crop by increasing the infection risk for specific plant diseases. In infected plant organs, these pathogens are able to produce mycotoxins. Mycotoxins like deoxynivalenol (DON) persist during storage, are heat resistant and of major concern for human and animal health after consumption of contaminated food and feed, respectively. Among fungivorous soil organisms, there are representatives of the soil fauna which are obviously antagonistic to a Fusarium infection and the contamination with mycotoxins. Specific members of the soil macro-, meso-, and microfauna provide a wide range of ecosystem services including the stimulation of decomposition processes which may result in the regulation of plant pathogens and the degradation of environmental contaminants. Investigations under laboratory conditions and in field were conducted to assess the functional linkage between soil faunal communities and plant pathogenic fungi (Fusarium culmorum). The aim was to examine if Fusarium biomass and the content of its mycotoxin DON decrease substantially in the presence of soil fauna (earthworms: Lumbricus terrestris, collembolans: Folsomia candida and nematodes: Aphelenchoides saprophilus) in a commercial cropping system managed with conservation tillage located in Northern Germany. The results of our investigations pointed out that the degradation performance of the introduced soil fauna must be considered as an important contribution to the biodegradation of fungal plant diseases and fungal-related contaminants. Different size classes within functional groups and the traits of keystone species appear to be significant for soil function and the provision of ecosystem services as in particular L. terrestris revealed to be the driver of the degradation process. Thus, earthworms contribute to a sustainable control of fungal pathogens like Fusarium and its mycotoxins in wheat straw by reducing the risk of plant diseases and environmental pollution as ecosystem services. Further studies are planned within the EU-project SoilMan under the BiodivERsA network. In context of the suppression of fungal plant pathogens and the detoxification of their mycotoxins by soil organisms in agroecosystems it is hypothesised that (1) processes related to services or disservices are induced and directed by abundance and activity of functional groups of soil biota; (2) dynamics and interaction in the soil biota community control ecosystem function and services.

Isotopologue signatures of nitrous oxide produced by nitrate-ammonifying bacteria isolated from soil

NASA Astrophysics Data System (ADS)

Behrendt, Undine; Well, Reinhard; Giesemann, Anette; Ulrich, Andreas; Augustin, Jürgen

2015-04-01

Agricultural soils are the largest single source of anthropogenic N2O to the atmosphere, primarily driven by microbiological processes such as denitrification and dissimilatory nitrate reduction to ammonium (DNRA). Both processes occur under similar conditions of low oxygen concentration and therefore, source partitioning of emitted N2O is difficult. Understanding what controls the dynamics and reaction equilibrium of denitrification and DNRA is important and may allow the development of more effective mitigation strategies. 15N site preference (SP), i.e. the difference between 15N of the central and peripheral N-position of the asymmetric N2O molecule, differs depending on processes involved in N2O formation. Hence investigation of the isotopomer ratios of formed N2O potentially presents a reliable mean to identify its source. In this study, bacterial isolates obtained from organic soils were screened for their ability to reduce nitrate/nitrite to ammonium and to release N2O to the atmosphere. Taxonomic characterisation of the strains revealed that N2O formation was only detected in ammonifying strains affiliated to several genera of the family Enterobacteriaceae and strains belonging to the genus Bacillus and Paenibacillus. Sampling of N2O was conducted by incubation of strains under oxic and anoxic conditions. Investigation of the 15N site preference showed SP values in the range of 39 to 57 o . Incubation conditions had no influence on the SP. The lowest values were achieved by a strain of the species Escherichia coli which was included in this study as a DNRA reference bacterium harbouring the NrfA gene that is coding the nitrite reductase, associated with respiratory nitrite ammonification. Soil isolates showed SP-values higher than 40 o . Comparison of these results with SP-values of N2O produced by denitrifying bacteria in pure cultures (-5 to 0 o )^[1, 2]revealedsignificantdifferences.Incontrast,N_2OproducedbydenitrifyingfungidisplayedSP - valuesinarangeof21to36o [3] ,which are much closer to the values of N2O from the investigated DNRA bacteria. However, the N2O formed under denitrifying conditions by organisms investigated so far can be distinguished with respect to its source (DNRA or denitrification) but a broader database is needed which cover a larger spectrum of taxa. [1] Sutka et al. Distinguishing nitrous oxide production from nitrification and denitrification on the basis of isotopomer abundances. Appl. Env. Microbiol. 2006, 72, 638. [2] Toyoda et al. Fractionation of N2O isotopomers during production by denitrifier. Soil Biol. Biochem. 2005, 37, 1535. [3] Rohe et al. Dual isotope and isotopomer signatures of nitrous oxide from fungal denitrification - a pure culture study. Rapid Commun. Mass Spectrom. 2014, 28, 1893

Enhancement of the Automated Quality Control Procedures for the International Soil Moisture Network

NASA Astrophysics Data System (ADS)

Heer, Elsa; Xaver, Angelika; Dorigo, Wouter; Messner, Romina

2017-04-01

In-situ soil moisture observations are still trusted to be the most reliable data to validate remotely sensed soil moisture products. Thus, the quality of in-situ soil moisture observations is of high importance. The International Soil Moisture Network (ISMN; http://ismn.geo.tuwien.ac.at/) provides in-situ soil moisture data from all around the world. The data is collected from individual networks and data providers, measured by different sensors in various depths. The data sets which are delivered in different units, time zones and data formats are then transformed into homogeneous data sets. An erroneous behavior of soil moisture data is very difficult to detect, due to annual and daily changes and most significantly the high influence of precipitation and snow melting processes. Only few of the network providers have a quality assessment for their data sets. Therefore, advanced quality control procedures have been developed for the ISMN (Dorigo et al. 2013). Three categories of quality checks were introduced: exceeding boundary values, geophysical consistency checks and a spectrum based approach. The spectrum based quality control algorithms aim to detect erroneous measurements which occur within plausible geophysical ranges, e.g. a sudden drop in soil moisture caused by a sensor malfunction. By defining several conditions which have to be met by the original soil moisture time series and their first and second derivative, such error types can be detected. Since the development of these sophisticated methods many more data providers shared their data with the ISMN and new types of erroneous measurements were identified. Thus, an enhancement of the automated quality control procedures became necessary. In the present work, we introduce enhancements of the existing quality control algorithms. Additionally, six completely new quality checks have been developed, e.g. detection of suspicious values before or after NAN-values, constant values and values that lie in a spectrum where a high majority of values before and after is flagged and therefore a sensor malfunction is certain. For the evaluation of the enhanced automated quality control system many test data sets were chosen, and manually validated to be compared to the existing quality control procedures and the new algorithms. Improvements will be shown that assure an appropriate assessment of the ISMN data sets, which are used for validations of soil moisture data retrieved by satellite data and are the foundation many other scientific publications.

Constitutive Soil Properties for Mason Sand and Kennedy Space Center

NASA Technical Reports Server (NTRS)

Thomas, Michael A.; Chitty, Daniel E.

2011-01-01

Accurate soil models are required for numerical simulations of land landings for the Orion Crew Exploration Vehicle (CEV). This report provides constitutive material models for two soil conditions at Kennedy Space Center (KSC) and four conditions of Mason Sand. The Mason Sand is the test sand for LaRC s drop tests and swing tests of the Orion. The soil models are based on mechanical and compressive behavior observed during geotechnical laboratory testing of remolded soil samples. The test specimens were reconstituted to measured in situ density and moisture content. Tests included: triaxial compression, hydrostatic compression, and uniaxial strain. A fit to the triaxial test results defines the strength envelope. Hydrostatic and uniaxial tests define the compressibility. The constitutive properties are presented in the format of LSDYNA Material Model 5: Soil and Foam. However, the laboratory test data provided can be used to construct other material models. The soil models are intended to be specific to the soil conditions they were tested at. The two KSC models represent two conditions at KSC: low density dry sand and high density in-situ moisture sand. The Mason Sand model was tested at four conditions which encompass measured conditions at LaRC s drop test site.

Nature versus nurture: functional assessment of restoration effects on wetland services using Nuclear Magnetic Resonance Spectroscopy

USGS Publications Warehouse

Sundareshwar, P.V.; Richardson, C.J.; Gleason, R.A.; Pellechia, P.J.; Honomichl, S.

2009-01-01

Land-use change has altered the ability of wetlands to provide vital services such as nutrient retention. While compensatory practices attempt to restore degraded wetlands and their functions, it is difficult to evaluate the recovery of soil biogeochemical functions that are critical for restoration of ecosystem services. Using solution 31P Nuclear Magnetic Resonance Spectroscopy, we examined the chemical forms of phosphorus (P) in soils from wetlands located across a land-use gradient. We report that soil P diversity, a functional attribute, was lowest in farmland, and greatest in native wetlands. Soil P diversity increased with age of restoration, indicating restoration of biogeochemical function. The trend in soil P diversity was similar to documented trends in soil bacterial taxonomic composition but opposite that of soil bacterial diversity at our study sites. These findings provide insights into links between ecosystem structure and function and provide a tool for evaluating the success of ecosystem restoration efforts. Copyright 2009 by the American Geophysical Union.

Bidirectional Reflectance Modeling of Non-homogeneous Plant Canopies

NASA Technical Reports Server (NTRS)

Norman, J. M. (Principal Investigator)

1985-01-01

The objective of this research is to develop a 3-dimensional radiative transfer model for predicting the bidirectional reflectance distribution function (BRDF) for heterogeneous vegetation canopies. The model (named BIGAR) considers the angular distribution of leaves, leaf area index, the location and size of individual subcanopies such as widely spaced rows or trees, spectral and directional properties of leaves, multiple scattering, solar position and sky condition, and characteristics of the soil. The model relates canopy biophysical attributes to down-looking radiation measurements for nadir and off-nadir viewing angles. Therefore, inversion of this model, which is difficult but practical should provide surface biophysical pattern; a fundamental goal of remote sensing. Such a model also will help to evaluate atmospheric limitations to satellite remote sensing by providing a good surface boundary condition for many different kinds of canopies. Furthermore, this model can relate estimates of nadir reflectance, which is approximated by most satellites, to hemispherical reflectance, which is necessary in the energy budget of vegetated surfaces.

Spectral Unmixing of Vegetation, Soil and Dry Carbon in Arid Regions: Comparing Multispectral and Hyperspectral Observations

NASA Technical Reports Server (NTRS)

Asner, Gregory P.; Heidebrecht, Kathleen B.

2001-01-01

Remote sensing of vegetation cover and condition is critically needed to understand the impacts of land use and climate variability in and and semi-arid regions. However, remote sensing of vegetation change in these environments is difficult for several reasons. First, individual plant canopies are typically small and do not reach the spatial scale of typical Landsat-like satellite image pixels. Second, the phenological status and subsequent dry carbon (or non-photosynthetic) fraction of plant canopies varies dramatically in both space and time throughout and and semi-arid regions. Detection of only the 'green' part of the vegetation using a metric such as the normalized difference vegetation index (NDVI) thus yields limited information on the presence and condition of plants in these ecosystems. Monitoring of both photosynthetic vegetation (PV) and non-photosynthetic vegetation (NPV) is needed to understand a range of ecosystem characteristics including vegetation presence, cover and abundance, physiological and biogeochemical functioning, drought severity, fire fuel load, disturbance events and recovery from disturbance.

Dielectric Constant Measurements on Lunar Soils and Terrestrial Minerals

NASA Technical Reports Server (NTRS)

Anderson, R. C.; Buehler, M. G.; Seshardri, S.; Schaap, M. G.

2004-01-01

The return to the Moon has ignited the need to characterize the lunar regolith using in situ methods. An examination of the lunar regolith samples collected by the Apollo astronauts indicates that only a few minerals (silicates and oxides) need be considered for in situ resource utilization (ISRU). This simplifies the measurement requirements and allows a detailed analysis using simple methods. Characterizing the physical properties of the rocks and soils is difficult because of many complex parameters such as soil temperature, mineral type, grain size, porosity, and soil conductivity. In this presentation, we will show that the dielectric constant measurement can provide simple detection for oxides such as TiO2, FeO, and water. Their presence is manifest by an unusually large imaginary permittivity.

Soil spectral characterization

NASA Technical Reports Server (NTRS)

Stoner, E. R.; Baumgardner, M. F.

1981-01-01

The spectral characterization of soils is discussed with particular reference to the bidirectional reflectance factor as a quantitative measure of soil spectral properties, the role of soil color, soil parameters affecting soil reflectance, and field characteristics of soil reflectance. Comparisons between laboratory-measured soil spectra and Landsat MSS data have shown good agreement, especially in discriminating relative drainage conditions and organic matter levels in unvegetated soils. The capacity to measure both visible and infrared soil reflectance provides information on other soil characteristics and makes it possible to predict soil response to different management conditions. Field and laboratory soil spectral characterization helps define the extent to which intrinsic spectral information is available from soils as a consequence of their composition and field characteristics.

Soils as records of past and present environments

NASA Astrophysics Data System (ADS)

Sauer, Daniela

2015-04-01

This contribution reflects selected pedological concepts that are helpful for interpreting soil properties related to past and present environments. These concepts are illustrated by examples from various landscapes, and their combination finally leads to some further conclusions. The concept of Targulian and Gerasimova (2009) distinguishes soil system and soil body. Soil system is defined as "open multiphase system functioning in any solid-phase substrate at its interface with the atmosphere, hydrosphere and biota", and soil body as "solid-phase part of a soil system produced by its long-term functioning and composed of a vertical sequence of genetic horizons". Soil system functioning corresponds to the recent environmental factors and includes heat and moisture dynamics, biomass production, biogeochemical cycles, and other processes. In contrast, a soil body is a record of the long-term functioning of a soil system. It thus provides a record not only of the functioning of the soil system under the present environmental conditions but also under past, possibly different, conditions. Hence, Targulian and Goryachkin (2004) called it the "memory" of the landscape. Richter and Yaalon (2012) argued that most soils comprise both, features that developed under the present environmental conditions and features that reflect different conditions that the soils experienced in the past; they concluded that most soils are polygenetic. Although the current functioning of the soil system in the concept of Targulian and Gerasimova (2009) is mainly controlled by the present-day combination of environmental factors, it should be added that past processes also influence the soil system, because past processes changed the soil properties in a way that also the present-day functioning of the soil system is affected by these changes. Earlier, Yaalon (1971) had categorised soil properties according to the time-span required for their adjustment to the actual environment, distinguishing (i) rapidly adjusting soil properties (adjusting within some hundreds of years), (ii) slowly adjusting soil properties (adjusting within some thousands of years), and (iii) persistent soil properties (showing no changes over ten thousands to millions of years). In a polygenetic soil, rapidly adjusting soil properties may already be in equilibrium with the present conditions, whereas slowly adjusting soil properties may still reflect past conditions. Thus, the lower the rate at which a certain soil property in a polygenetic soil adjusts, the larger is the extent to which this property is still determined by earlier environmental conditions. Knowledge on the rates at which soil properties adjust may hence be used to estimate the time at which a significant environmental change took place, based on the degree of overprinting of the different kinds of soil properties adjusting at different rates in a polygenetic soil. References: Richter, D. de B., Yaalon, D.H., 2012. "The changing model of soil" revisited. Soil Sci. Soc. Am. J. 76, 766-778. Targulian, V. O., Goryachkin, S. V., 2004. Soil memory: Types of records, carriers, hierarchy and diversity. Revista Mexicana Ciencias Geol. 21, 1-8. Targulian, V.O., Gerasimova, M., 2009. Soil geography: geography of soil systems and soil bodies. Soil Geography: New Horizons. International Conference, 16-20 November 2009 in Huatulco, Mexico. Book of abstracts, 39. Yaalon, D.H., 1971. Soil forming processes in time and space. In: Yaalon, D.H. (Ed.), Paleopedology-origin, nature and dating of paleosols. Int. Soc. Soil Sci. and Israel Univ. Press, Jerusalem, pp. 29-39.

Remote sensing for environmental protection of the eastern Mediterranean rugged mountainous areas, Lebanon

NASA Astrophysics Data System (ADS)

Khawlie, M.; Awad, M.; Shaban, A.; Bou Kheir, R.; Abdallah, C.

Lying along the eastern Mediterranean coast with elevated mountain chains higher than 2500 m straddling its terrain, Lebanon is a country of natural beauty and is thus attracting tourism. However, with a population density exceeding 800/km 2 and a rugged steep sloping land, problems abound in the country calling for holistic-approach studies. Only remote sensing, whose use is new in Lebanon can secure such needed studies within a scientific and pragmatic framework. The paper demonstrates for the concerned themes, the innovative use of remote sensing in such a difficult terrain, giving three examples of major environmental problems in the coastal mountains. Only few studies have so far focused on those mountains, notably application of remote sensing. The rugged mountainous terrain receives considerable rain, but the water is quickly lost running on the steep slopes, or infiltrating through fractures and the karstic conduits into the subsurface. Field investigations are difficult to achieve, therefore, remote sensing helps reveal various surface land features important in reflecting water feeding into the subsurface. Optical, radar and thermal infrared remotely sensed data cover a wide spectrum serving that purpose. A map of preferential groundwater accumulation potential is produced. It can serve for better water exploitation as well as protection. Because the terrain is karstic and rugged, the subsurface water flow is difficult to discern. Any pollution at a certain spot would certainly spread around. This constitutes the second example of environmental problems facing the mountainous areas in Lebanon. An integrated approach using remote sensing and geographic information systems (GIS) gives good results in finding out the likelihood of how pollution, or contaminants, can selectively move in the subsurface. A diagnostic analysis with a GIS-type software acts as a guide producing indicative maps for the above purpose. The third example given deals with the problem of losing soil, which is a very vital source in such mountainous land. With steep slopes, torrential rain and improper human interference, run-off is high and water-soil erosion is continuously deteriorating the land cover. Remote sensing can facilitate studying the factors enhancing the process, such as soil type, slope gradient, drainage, geology and land cover. Digital elevation models created from SAR imagery contribute significantly to assessing vulnerability of hydric-soil erosion over such a difficult terrain. GIS layers of the above factors are integrated with erosional criteria to produce a risk map of soil erosion. Results indicate that 36% of the Lebanese terrain is under threat of high-level erosion, and 52% of that is concentrated in the rugged mountainous regions.

Assessing the humus status and CO2 production in soils of anthropogenic and agrogenic landscapes in southern regions of the Russian Far East

NASA Astrophysics Data System (ADS)

Purtova, L. N.; Kostenkov, N. M.; Shchapova, L. N.

2017-01-01

The humus status and CO2 production have been assessed in soils of natural and anthropogenic landscapes in southern regions of the Far East with different types of redox conditions. A higher production of CO2 is typical of burozems and soddy-eluvial-metamorphic soils with oxidative and contrast redox conditions. These are soils with medium or high humus content, high potential humification capacity, and medium enrichment with catalase. A decrease in the content of humus in the plow horizons of soils in agrogenic landscapes is revealed compared to their natural analogues. The studied soils mainly have humus of the fulvate-humate type. The fractions strongly bound to the mineral soil component prevail in humic acids. In waterlogged mucky-humus gley soils, the anaerobic conditions hamper the biological activity and transformation of organic matter, which favors its accumulation. A low production of CO2 is observed in soils with reducing conditions. To determine the differences between the CO2 emission parameters in soils of agrogenic and natural landscapes, monitoring studies should be extended.

Temporal and spatial variations of soil carbon dioxide, methane, and nitrous oxide fluxes in a Southeast Asian tropical rainforest

NASA Astrophysics Data System (ADS)

Itoh, M.; Kosugi, Y.; Takanashi, S.; Hayashi, Y.; Kanemitsu, S.; Osaka, K.; Tani, M.; Nik, A. R.

2010-09-01

To clarify the factors controlling temporal and spatial variations of soil carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) fluxes, we investigated these gas fluxes and environmental factors in a tropical rainforest in Peninsular Malaysia. Temporal variation of CO2 flux in a 2-ha plot was positively related to soil water condition and rainfall history. Spatially, CO2 flux was negatively related to soil water condition. When CO2 flux hotspots were included, no other environmental factors such as soil C or N concentrations showed any significant correlation. Although the larger area sampled in the present study complicates explanations of spatial variation of CO2 flux, our results support a previously reported bipolar relationship between the temporal and spatial patterns of CO2 flux and soil water condition observed at the study site in a smaller study plot. Flux of CH4 was usually negative with little variation, resulting in the soil at our study site functioning as a CH4 sink. Both temporal and spatial variations of CH4 flux were positively related to the soil water condition. Soil N concentration was also related to the spatial distribution of CH4 flux. Some hotspots were observed, probably due to CH4 production by termites, and these hotspots obscured the relationship between both temporal and spatial variations of CH4 flux and environmental factors. Temporal variation of N2O flux and soil N2O concentration was large and significantly related to the soil water condition, or in a strict sense, to rainfall history. Thus, the rainfall pattern controlled wet season N2O production in soil and its soil surface flux. Spatially, large N2O emissions were detected in wet periods at wetter and anaerobic locations, and were thus determined by soil physical properties. Our results showed that, even in Southeast Asian rainforests where distinct dry and wet seasons do not exist, variation in the soil water condition related to rainfall history controlled the temporal variations of soil CO2 flux, CH4 uptake, and N2O emission. The soil water condition associated with soil hydraulic properties was also the important controlling factor of the spatial distributions of these gas fluxes.

Revealing spatial distribution of soil organic carbon contents and stocks of a disturbed bog relict by in-situ NIR and apparent EC mapping

NASA Astrophysics Data System (ADS)

Bechtold, Michel; Tiemeyer, Bärbel; Don, Axel; Altdorff, Daniel; van der Kruk, Jan; Huisman, Johan A.

2013-04-01

Previous studies showed that in-situ visible near-infrared (vis-NIR) spectroscopy can overcome the limitations of conventional soil sampling. Costs can be reduced and spatial resolution enhanced when mapping field-scale variability of soil organic carbon (SOC). Detailed maps can help to improve SOC management and lead to better estimates of field-scale total carbon stocks. Knowledge of SOC field patterns may also help to reveal processes and factors controlling SOC variability. In this study, we apply in situ vis-NIR and apparent electrical conductivity (ECa) mapping to a disturbed bog relict. The major question of this application study was how field-scale in-situ vis-NIR mapping performs for a very heterogeneous area and under difficult grassland conditions and under highly-variable water content conditions. Past intensive peat cutting and deep ploughing in some areas, in combination with a high background heterogeneity of the underlying mineral sediments, have led to a high variability of SOC content (5.6 to 41.3 %), peat layer thickness (25 to 60 cm) and peat degradation states (from nearly fresh to amorphous). Using a field system developed by Veris Technologies (Salina KS, USA), we continuously collected vis-NIR spectra at 10 cm depth (measurement range: 350 nm to 2200 nm) over an area of around 12 ha with a line spacing of about 12 m. The system includes a set of discs for measuring ECa of the first 30 and 90 cm of the soil. The same area was also mapped with a non-invasive electro-magnetic induction (EMI) setup that provided ECa data of the first 25, 50 and 100 cm. For calibration and validation of the spatial data, we took 30 representative soil samples and 15 soil cores of about 90 cm depth, for which peat thickness, water content, pore water EC, bulk density (BD), as well as C and N content were determined for various depths. Preliminary results of the calibration of the NIR spectra to the near-surface SOC contents indicate good data quality despite the challenging site conditions. Bore hole data indicates that the peat layer is characterized by lower BD, higher pore water EC, higher SOC content, and higher water contents compared to the underlying mineral sediments. This ECa contrast at the peat-sand interface is promising for using the various ECa investigation depths as predictors for peat thickness. Preliminary EMI results also show a correlation between ECa and SOC content, most strongly for the 25 cm EMI signal. We evaluate how vis-NIR and ECa data can be used in a joined approach to estimate SOC content as well as SOC stock distribution.

Positive responses of coastal dune plants to soil conditioning by the invasive Lupinus nootkatensis

NASA Astrophysics Data System (ADS)

Hanslin, Hans Martin; Kollmann, Johannes

2016-11-01

Invasive nitrogen-fixing plants drive vegetation dynamics and may cause irreversible changes in nutrient-limited ecosystems through increased soil resources. We studied how soil conditioning by the invasive alien Lupinus nootkatensis affected the seedling growth of co-occurring native plant species in coastal dunes, and whether responses to lupin-conditioned soil could be explained by fertilisation effects interacting with specific ecological strategies of the native dune species. Seedling performance of dune species was compared in a greenhouse experiment using field-collected soil from within or outside coastal lupin stands. In associated experiments, we quantified the response to nutrient supply of each species and tested how addition of specific nutrients affected growth of the native grass Festuca arundinacea in control and lupin-conditioned soil. We found that lupin-conditioned soil increased seedling biomass in 30 out of 32 native species; the conditioned soil also had a positive effect on seedling biomass of the invasive lupin itself. Increased phosphorus mobilisation by lupins was the major factor driving these positive seedling responses, based both on growth responses to addition of specific elements and analyses of plant available soil nutrients. There were large differences in growth responses to lupin-conditioned soil among species, but they were unrelated to selected autecological indicators or plant strategies. We conclude that Lupinus nootkatensis removes the phosphorus limitation for growth of native plants in coastal dunes, and that it increases cycling of other nutrients, promoting the growth of its own seedlings and a wide range of dune species. Finally, our study indicates that there are no negative soil legacies that prevent re-establishment of native plant species after removal of lupins.

Redox-induced mobilization of copper, selenium, and zinc in deltaic soils originating from Mississippi (U.S.A.) and Nile (Egypt) River Deltas: A better understanding of biogeochemical processes for safe environmental management.

PubMed

Shaheen, Sabry M; Frohne, Tina; White, John R; DeLaune, Ron D; Rinklebe, Jörg

2017-01-15

Studies about the mobilization of potentially toxic elements (PTEs) in deltaic soils can be challenging, provide critical information on assessing the potential risk and fate of these elements and for sustainable management of these soils. The impact of redox potential (E H ), pH, iron (Fe), manganese (Mn), sulfate (SO 4 2- ), chloride (Cl - ), aliphatic dissolved organic carbon (DOC), and aromatic dissolved organic carbon (DAC) on the mobilization of copper (Cu), selenium (Se), and zinc (Zn) was studied in two soils collected from the Nile and Mississippi Rivers deltaic plains focused on increasing our understanding of the fate of these toxic elements. Soils were exposed to a range of redox conditions stepwise from reducing to oxidizing soil conditions using an automated biogeochemical microcosm apparatus. Concentrations of DOC and Fe were high under reducing conditions as compared to oxidizing conditions in both soils. The proportion of DAC in relation to DOC in solution (aromaticity) was high in the Nile Delta soil (NDS) and low in the Mississippi Delta soil (MDS) under oxidizing conditions. Mobilization of Cu was low under reducing conditions in both soils which was likely caused by sulfide precipitation and as a result of reduction of Cu 2+ to Cu 1+ . Mobilization of Se was high under low E H in both soils. Release of Se was positively correlated with DOC, Fe, Mn, and SO 4 2- in the NDS, and with Fe in the MDS. Mobilization of Zn showed negative correlations with E H and pH in the NDS while these correlations were non-significant in the MDS. The release dynamics of dissolved Zn could be governed mainly by the chemistry of Fe and Mn in the NDS and by the chemistry of Mn in the MDS. Our findings suggest that a release of Se and Zn occurs under anaerobic conditions, while aerobic conditions favor the release of Cu in both soils. In conclusion, the release of Cu, Se, and Zn under different reducing and oxidizing conditions in deltaic wetland soils should be taken into account due to increased mobilization and the potential environmental risks associated with food security in utilizing these soils for flooded agricultural and fisheries systems. Copyright © 2016 Elsevier Ltd. All rights reserved.

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.

Ecological and geographical regularities of changes in the biological activity of automorphic soils on the foothills and adjacent plains of the Central Caucasus region (Kabardino-Balkarian Republic)

NASA Astrophysics Data System (ADS)

Gorobtsova, O. N.; Khezheva, F. V.; Uligova, T. S.; Tembotov, R. Kh.

2015-03-01

The biochemical properties inherent to the main types of automorphic soils developed in different bioclimatic conditions of Elbrus and Terek variants of the vertical zonality within Kabardino-Balkaria were compared. The natural-climatic conditions of these variants noticeably affect the soil cover pattern. The ratio of the oxidase and hydrolase activities is sensitive to the moisture conditions in which these soils are formed. The redox processes are more active in drier conditions, whereas hydrolytic processes are more active under higher moisture. The level of the biological activity of the automorphic soils is estimated using the integral index of the ecological-biological soil status.

Lignin decomposition and microbial community in paddy soils: effects of alternating redox conditions

NASA Astrophysics Data System (ADS)

Cerli, Chiara; Liu, Qin; Hanke, Alexander; Kaiser, Klaus; Kalbitz, Karsten

2013-04-01

Paddy soils are characterised by interchanging cycles of anaerobic and aerobic conditions. Such fluctuations cause continuous changes in soil solution chemistry as well as in the composition and physiological responses of the microbial community. Temporary deficiency in oxygen creates conditions favourable to facultative or obligates anaerobic bacteria, while aerobic communities can thrive in the period of water absence. These alterations can strongly affect soil processes, in particular organic matter (OM) accumulation and mineralization. In submerged soils, lignin generally constitutes a major portion of the total OM because of hampered degradation under anoxic conditions. The alternating redox cycles resulting from paddy soil management might promote both degradation and preservation of lignin, affecting the overall composition and reactivity of total and dissolved OM. We sampled soils subjected to cycles of anoxic (rice growing period) and oxic (harvest and growth of other crops) conditions since 700 and 2000 years. We incubated suspended Ap material, sampled from the two paddy plus two corresponding non-paddy control soils under oxic and anoxic condition, for 3 months, interrupted by a short period of three weeks (from day 21 to day 43) with reversed redox conditions. At each sampling time (day 2, 21, 42, 63, 84), we determined lignin-derived phenols (by CuO oxidation) as well as phospholipids fatty acids contents and composition. We aimed to highlight changes in lignin decomposition as related to the potential rapid changes in microbial community composition. Since the studied paddy soils had a long history of wet rice cultivation, the microbial community should be well adapted to interchanging oxic and anoxic cycles, therefore fully expressing its activity at both conditions. In non-paddy soil changes in redox conditions caused modification of quantity and composition of the microbial community. On the contrary, in well-established paddy soils the microbial community appeared to be affected by alternating redox conditions more in quantity that in quality. Bacteria represented the largest portion of the living microorganisms, responding promptly to changes in soil redox status. However we did not detect any sign of lignin biodegradation. Relative short (3 weeks) changes in redox conditions had no effect on lignin decomposition or oxidation state. Also, lignin was not altered during oxic incubation. Since fungi represented only small portion of the microbial biomass in the studied soils, they were obviously not capable to cause much degradation, even under favourable conditions. On the contrary, changes in redox conditions strongly affected lignin extractability, regardless of the initial content and direction of change in both paddy and non-paddy soils. This was likely a result of (partial) dissolution and/or pH-induced changes of the surface properties of Fe and Mn hydrous oxides causing the release of mineral-associated lignin-derived phenols. Thus, we speculate that oxidised lignin fragments produced during the (oxic) dry period do not remain in the soils but percolate with water drainage during the flooding period.

Carbon Budgets for Four Forests in Northern California

NASA Astrophysics Data System (ADS)

Mattson, K. G.; Zhang, J.; Cohn, E. P.

2016-12-01

Carbon pools and fluxes are being measured in the first two years in four forest types in Northern California as part of a long-term experiment where canopies will be experimentally thinned to test the effects of forest canopy on carbon cycling. All major pools of carbon have been quantified along with most fluxes between pools. The pools are not techincally difficult to measure or estimate, the fluxes can be more difficult. But using our field measures are in a bookkeeping model of carbon pools and annual fluxes we can develop reasonably accurate carbon cycles in these four forests. We use direct measures as much as possible (litterfall, soil CO2 efflux, wood decay, harvests, etc), then make reasonable assumptions for more difficult measures (e.g., annual gross primary production, tree mortality, root decomposition, soil carbon turnover), and finally make some estimates by difference (root mortality or soil carbon turnover). We are able to construct models that balance carbon pools similar to our measures. The four forest types range considerably in their carbon budgets and cycles. Above ground live biomass carbon pool ranges from 104Mg C ha-1 for the 50 year old Ponderosa Pine conversion stands to more than double that 265 for the True Fir stand found at higher elevation (greater than 6,000 feet). The Mixed Conifer (the most representative forest type) and the Oak Stand (up to 60 % basal area California black oak) are both mid way between at 140 and 155, respectively. The detrital carbon pools generally follow the above ground biomass trends and contain greater pool sizes (down to 100 cm soil depths). Approximately 2/3rds of the detrital carbon is stored in the mineral soil but significant amounts are also stored in the forest floors and woody debris. Live small roots are relatively small pools of about 5 Mg C ha-1 but active and nearly turnover each year. Live roots produce about half the soil CO2 efflux. Dead roots are generally twice the size of live roots and turnover at half the rate. Woody debris appears to be an important contributor to below ground carbon. We have derived a humification coefficient where 2/3 of the decomposed carbon leaves the system as CO2 but more importantly up 1/3 remains behind to enter the next pool.

Influences of evergreen gymnosperm and deciduous angiosperm tree species on the functioning of temperate and boreal forests.

PubMed

Augusto, Laurent; De Schrijver, An; Vesterdal, Lars; Smolander, Aino; Prescott, Cindy; Ranger, Jacques

2015-05-01

It has been recognized for a long time that the overstorey composition of a forest partly determines its biological and physical-chemical functioning. Here, we review evidence of the influence of evergreen gymnosperm (EG) tree species and deciduous angiosperm (DA) tree species on the water balance, physical-chemical soil properties and biogeochemical cycling of carbon and nutrients. We used scientific publications based on experimental designs where all species grew on the same parent material and initial soil, and were similar in stage of stand development, former land use and current management. We present the current state of the art, define knowledge gaps, and briefly discuss how selection of tree species can be used to mitigate pollution or enhance accumulation of stable organic carbon in the soil. The presence of EGs generally induces a lower rate of precipitation input into the soil than DAs, resulting in drier soil conditions and lower water discharge. Soil temperature is generally not different, or slightly lower, under an EG canopy compared to a DA canopy. Chemical properties, such as soil pH, can also be significantly modified by taxonomic groups of tree species. Biomass production is usually similar or lower in DA stands than in stands of EGs. Aboveground production of dead organic matter appears to be of the same order of magnitude between tree species groups growing on the same site. Some DAs induce more rapid decomposition of litter than EGs because of the chemical properties of their tissues, higher soil moisture and favourable conditions for earthworms. Forest floors consequently tend to be thicker in EG forests compared to DA forests. Many factors, such as litter lignin content, influence litter decomposition and it is difficult to identify specific litter-quality parameters that distinguish litter decomposition rates of EGs from DAs. Although it has been suggested that DAs can result in higher accumulation of soil carbon stocks, evidence from field studies does not show any obvious trend. Further research is required to clarify if accumulation of carbon in soils (i.e. forest floor + mineral soil) is different between the two types of trees. Production of belowground dead organic matter appears to be of similar magnitude in DA and EG forests, and root decomposition rate lower under EGs than DAs. However there are some discrepancies and still are insufficient data about belowground pools and processes that require further research. Relatively larger amounts of nutrients enter the soil-plant biogeochemical cycle under the influence of EGs than DAs, but recycling of nutrients appears to be slightly enhanced by DAs. Understanding the mechanisms underlying forest ecosystem functioning is essential to predicting the consequences of the expected tree species migration under global change. This knowledge can also be used as a mitigation tool regarding carbon sequestration or management of surface waters because the type of tree species affects forest growth, carbon, water and nutrient cycling. © 2014 Institut National de la Recherche Agronomique. Biological Reviews © 2014 Cambridge Philosophical Society.

A monitoring of environmental effects from household greywater reuse for garden irrigation.

PubMed

Mohamed, Radin Maya Saphira Radin; Kassim, Amir Hashim Mohd; Anda, Martin; Dallas, Stewart

2013-10-01

The option of reusing greywater is proving to be increasingly attractive to address the water shortage issue in many arid and semiarid countries. Greywater represents a constant resource, since an approximately constant amount of greywater is generated from kitchen, laundries, bathroom in every household daily, independent of the weather. However, the use of greywater for irrigation in particular for household gardening may pose major hazards that have not been studied thoroughly. In this study, a 1-year monitoring was conducted in four selected households in Perth, Western Australia. The aim of the monitoring works is to investigate the variability in the greywater flow and quality, and to understand its impact in the surrounding environments. Case studies were selected based on different family structure including number, ages of the occupants, and greywater system they used. Samples of greywater effluent (showers, laundries, bathtub, and sinks), leachate, soil, and plants at each case study were collected between October 2008 and December 2009 which covered the high (spring/summer) and low (autumn/winter) production of greywater. Physical and chemical tests were based on the literature and expected components of laundry and bathroom greywater particularly on greywater components likely to have detrimental impacts on soils, plants, and other water bodies. Monitoring results showed the greywater quality values for BOD, TSS, and pH which sometimes fell outside the range as stipulated in the guidelines. The soil analyses results showed that salinity, SAR, and the organic content of the soil increased as a function of time and affected the plant growth. Nutrient leaching or losses from soil irrigated with greywater shows the movement of nutrients and the sole impact from greywater in uncontrolled plots in case studies is difficult to predicted due to the influence of land dynamics and activities. Investigative and research monitoring was used to understand greywater irrigation in households. Greywater quality is very site specific and difficult to predetermine or control except for the use of some recommended household products when using greywater. Investigative and research monitoring was indicated that greywater quality is very site specific and difficult to predetermine or control except for the use of some recommended household products when using greywater.

Effect of land use change on soil properties and functions

NASA Astrophysics Data System (ADS)

Tonutare, Tonu; Kõlli, Raimo; Köster, Tiina; Rannik, Kaire; Szajdak, Lech; Shanskiy, Merrit

2014-05-01

For good base of sustainable land management and ecologically sound protection of soils are researches on soil properties and functioning. Ecosystem approach to soil properties and functioning is equally important in both natural and cultivated land use conditions. Comparative analysis of natural and agro-ecosystems formed on similar soil types enables to elucidate principal changes caused by land use change (LUC) and to elaborate the best land use practices for local pedo-ecological conditions. Taken for actual analysis mineral soils' catena - rendzina → brown soils → pseudopodzolic soils → gley-podzols - represent ca 1/3 of total area of Estonian normal mineral soils. All soils of this catena differ substantially each from other by calcareousness, acidity, nutrition conditions, fabric and humus cover type. This catena (representative to Estonian pedo-ecological conditions) starts with drought-prone calcareous soils. Brown (distributed in northern and central Estonia) and pseudopodzolic soils (in southern Estonia) are the most broadly acknowledged for agricultural use medium-textured high-quality automorphic soils. Dispersedly distributed gley-podzols are permanently wet and strongly acid, low-productivity sandy soils. In presentation four complex functions of soils are treated: (1) being a suitable soil environment for plant cover productivity (expressed by annual increment, Mg ha-1 yr-1); (2) forming adequate conditions for decomposition, transformation and conversion of fresh falling litter (characterized by humus cover type); (3) deposition of humus, individual organic compounds, plant nutrition elements, air and water, and (4) forming (bio)chemically variegated active space for soil type specific edaphon. Capacity of soil cover as depositor (3) depends on it thickness, texture, calcareousness and moisture conditions. Biological activity of soil (4) is determined by fresh organic matter influx, quality and quantity of biochemical substances and humus, and pedo-ecological conditions. LUC from natural to arable is accompanied by different regulations: (1) regular restoration of plant available nutrition elements' stocks in soil, (2) regulation (if needed) of water regime of gleyed and gley soils, (3) optimizing of soil actual acidity by liming, and (4) forming a suitable for crops seed bed instead of natural epipedon. Principal changes are occurred in fabric and agrochemical properties of topsoil and in soil functioning. The connected with LUC changes in soil functioning are: (1) increase of openness level of chemical elements cycling and nutrition elements concentration in phytomass, and (2) decrease of total phytomass, species diversity, amount of annual falling litter and content of mortmass in soil cover. These changes lead to decreasing of biological control on soil resources, flux of energy and substances to soil processes, and volume of cycling. At the same time the intensity of organic matter decomposition and outflow of nutrition elements are increased. All these changes are resulted by alteration of food chains and exhausting of nutrition elements' stocks. The changes in soil functioning (decrease or increase of productivity) depend much on soil type. The aspects of functioning, which do not changed with LUC are chemical-textural potential of soil cover and functioning character of subsoil. The sound matching of soil and plant cover is of decisive importance for sustainable functioning of ecosystem and in attaining a good environmental status of the area.

Using magnetic susceptibility to facilitate more rapid, reproducible and precise delineation of hydric soils in the midwestern USA

USGS Publications Warehouse

Grimley, D.A.; Arruda, N.K.; Bramstedt, M.W.

2004-01-01

Standard field indicators, currently used for hydric soil delineations [USDA-NRCS, 1998. Field indicators of hydric soils in the United States, Version 4.0. In: G.W. Hurt et al. (Ed.), United States Department of Agriculture-NRCS, Fort Worth, TX], are useful, but in some cases, they can be subjective, difficult to recognize, or time consuming to assess. Magnetic susceptibility (MS) measurements, acquired rapidly in the field with a portable meter, have great potential to help soil scientists delineate and map areas of hydric soils more precisely and objectively. At five sites in Illinois (from 5 to 15 ha in area) with contrasting soil types and glacial histories, the MS values of surface soils were measured along transects, and afterwards mapped and contoured. The MS values were found to be consistently higher in well-drained soils and lower in hydric soils, reflecting anaerobic deterioration of both detrital magnetite and soil-formed ferrimagnetics. At each site, volumetric MS values were statistically compared to field indicators to determine a critical MS value for hydric soil delineation. Such critical values range between 22??10-5 and 33??10-5 SI in silty loessal or alluvial soils in Illinois, but are as high as 61??10-5 SI at a site with fine sandy soil. A higher magnetite content and slower dissolution rate in sandy soils may explain the difference. Among sites with silty parent material, the lowest critical value (22??10-5 SI) occurs in soil with low pH (4.5-5.5) since acidic conditions are less favorable to ferrimagnetic mineral neoformation and enhance magnetite dissolution. Because of their sensitivity to parent material properties and soil pH, critical MS values must be determined on a site specific basis. The MS of studied soil samples (0-5 cm depth) is mainly controlled by neoformed ultrafine ferrimagnetics and detrital magnetite concentrations, with a minor contribution from anthropogenic fly ash. Neoformed ferrimagnetics are present in all samples but, based on high ??FD% (???5% to 10%), are most prevalent in high pH Mollisols of northeastern Illinois. Scanning electron microscope images display significantly more detrital magnetite alteration in hydric soils, substantiating that reductive dissolution of magnetite (aided by microorganisms) is a primary cause for lower MS. Fly ash comprises 8-50% of the >5 ??m strongly magnetic particles and typically accounts for 5-15% of the total MS signal. The proportion of fly ash in >5 ??m strongly magnetic fractions is greater in hydric soils because of lower natural magnetite contents, possibly combined with historical topsoil accumulation in lower landscapes. Magnetic fly ash particles are also more altered in low MS soils, implying that significant magnetite dissolution can occur in less than 150 years. ?? 2004 Elsevier B.V. All rights reserved.

Simulation and analysis of soil-water conditions in the Great Plains and adjacent areas, central United States, 1951-80

USGS Publications Warehouse

Dugan, Jack T.; Zelt, Ronald B.

2000-01-01

Ground-water recharge and consumptive-irrigation requirements in the Great Plains and adjacent areas largely depend upon an environment extrinsic to the ground-water system. This extrinsic environment, which includes climate, soils, and vegetation, determines the water demands of evapotranspiration, the availability of soil water to meet these demands, and the quantity of soil water remaining for potential ground-water recharge after these demands are met. The geographic extent of the Great Plains contributes to large regional differences among all elements composing the extrinsic environment, particularly the climatic factors. A soil-water simulation program, SWASP, which synthesizes selected climatic, soil, and vegetation factors, was used to simulate the regional soil-water conditions during 1951-80. The output from SWASP consists of several soil-water characteristics, including surface runoff, infiltration, consumptive water requirements, actual evapotranspiration, potential recharge or deep percolation under various conditions, consumptive irrigation requirements, and net fluxes from the ground-water system under irrigated conditions. Simulation results indicate that regional patterns of potential recharge, consumptive irrigation requirements, and net fluxes from the ground-water system under irrigated conditions are largely determined by evapotranspiration and precipitation. The local effects of soils and vegetation on potential recharge cause potential recharge to vary by more than 50 percent in some areas having similar climatic conditions.

Assessment of bioavailability of heavy metal pollutants using soil isolates of Chlorella sp.

PubMed

Krishnamurti, Gummuluru S R; Subashchandrabose, Suresh R; Megharaj, Mallavarapu; Naidu, Ravi

2015-06-01

Biotests conducted with plants are presently used to estimate metal bioavailability in contaminated soils. But when plants are grown in soils, especially the plants with fine roots, root collection is easily biased and tedious. Indeed, at harvest, small amounts of soil can adhere to roots, resulting in overestimation of root metal content, and the finest roots are often discarded from the analysis because of their difficult and almost impossible recovery. This report presents a novel method for assessing the bioavailability of heavy metals in soils using microalgae. Two species of green unicellular microalgae were isolated from two highly contaminated soils and identified by phylogenetic and molecular evolutionary analyses as Chlorella sp. RBM and Chlorella sp. RHM. These two cultures were used to determine the metal uptake from metal-contaminated soils of South Australia as a novel, cost-effective, simple and rapid method for assessing the bioavailability of heavy metals in soils. The suggested method is an attempt to achieve a realistic estimate of bioavailability which overcomes the inherent drawback of root metal contamination in the bioavailability indices so far reported.

Increased ambient air temperature alters the severity of soil water repellency

NASA Astrophysics Data System (ADS)

van Keulen, Geertje; Sinclair, Kat; Hallin, Ingrid; Doerr, Stefan; Urbanek, Emilia; Quinn, Gerry; Matthews, Peter; Dudley, Ed; Francis, Lewis; Gazze, S. Andrea; Whalley, Richard

2017-04-01

Soil repellency, the inability of soils to wet readily, has detrimental environmental impacts such as increased runoff, erosion and flooding, reduced biomass production, inefficient use of irrigation water and preferential leaching of pollutants. Its impacts may exacerbate (summer) flood risks associated with more extreme drought and precipitation events. In this study we have tested the hypothesis that transitions between hydrophobic and hydrophilic soil particle surface characteristics, in conjunction with soil structural properties, strongly influence the hydrological behaviour of UK soils under current and predicted UK climatic conditions. We have addressed the hypothesis by applying different ambient air temperatures under controlled conditions to simulate the effect of predicted UK climatic conditions on the wettability of soils prone to develop repellency at different severities. Three UK silt-loam soils under permanent vegetation were selected for controlled soil perturbation studies. The soils were chosen based on the severity of hydrophobicity that can be achieved in the field: severe to extreme (Cefn Bryn, Gower, Wales), intermediate to severe (National Botanical Garden, Wales), and subcritical (Park Grass, Rothamsted Research near London). The latter is already highly characterised so was also used as a control. Soils were fully saturated with water and then allowed to dry out gradually upon exposure to controlled laboratory conditions. Soils were allowed to adapt for a few hours to a new temperature prior to initiation of the controlled experiments. Soil wettability was determined at highly regular intervals by measuring water droplet penetration times. Samples were collected at four time points: fully wettable, just prior to and after the critical soil moisture concentrations (CSC), and upon reaching air dryness (to constant weight), for further (ultra)metaproteomic and nanomechanical studies to allow integration of bulk soil characterisations with functional expression and nanoscale studies to generate deep mechanistic understanding of the roles of microbes in soil ecosystems. Our controlled soil pertubation studies have shown that an increase in ambient temperature has consistently affected the severity of soil water repellency. Surprisingly, a higher ambient air temperature impacts soils that in the field develop subcritical and extreme repellency, differently under controlled laboratory conditions. We will discuss the impact of these results in relation to predicted UK climatic conditions. Soil metaproteomics will provide mechanistic insight at the molecular level whether differential microbial adaptation is correlated with the apparent different response to a higher ambient air temperature.

SOIL AND SEDIMENT SAMPLING METHODS

EPA Science Inventory

The EPA Office of Solid Waste and Emergency Response's (OSWER) Office of Superfund Remediation and Technology Innovation (OSRTI) needs innovative methods and techniques to solve new and difficult sampling and analytical problems found at the numerous Superfund sites throughout th...

Using soil isotopes as an indicator of denitrification in weetlands

EPA Science Inventory

Denitrification is an important ecosystem service provided by wetlands, which results in removal of excess nitrogen that can threaten aquatic systems. Unfortunately, direct measurement of denitrification has traditionally been expensive, time intensive, and difficult. However, ...

Germination of Blue Wildrye in Biochar Treated Mining Impacted Soils

EPA Science Inventory

Stabilization of mine sites with vegetation is an important management strategy to reduce metal movement off-site. Plant growth, however, is often hampered by poor soil conditions. Biochar is a novel soil amendment that may improve soil health conditions and improve plant growt...

Transformation of humus substances in the long-drained surface-gleyed soddy-podzolic soils under conditions of pronounced microrelief and different agrogenic loads

NASA Astrophysics Data System (ADS)

Ovchinnikova, M. F.

2016-08-01

The transformation of humus substances resulting from artificial drainage of the surface-gleyed soddy-podzolic soils under conditions of pronounced microtopography and different agrogenic loads was studied. The studied soil characteristics included acid-base conditions, the content and group composition of humus, the ratios between the fractions of humus acids, and optical density of humic acids. The features attesting to humus degradation were found in the soils of microdepressions periodically subjected to excessive surface moistening, in the soils of different landforms upon the construction of drainage trenches, and in the plowed non-fertilized soils. The response of humus characteristics to the changes in the ecological situation in the period of active application of agrochemicals for reclamation of the agrotechnogenically disturbed soils was traced. It was shown that the long-term dynamics of the particular parameters of the biological productivity of the soil depend on the hydrological and agrogenic factors, as well as on the weather conditions.

The Impact of Organo-Mineral Complexation on Mineral Weathering in the Soil Zone under Unsaturated Conditions

NASA Astrophysics Data System (ADS)

Michael, H. A.; Tan, F.; Yoo, K.; Imhoff, P. T.

2017-12-01

While organo-mineral complexes can protect organic matter (OM) from biodegradation, their impact on soil mineral weathering is not clear. Previous bench-scale experiments that focused on specific OM and minerals showed that the adsorption of OM to mineral surfaces accelerates the dissolution of some minerals. However, the impact of natural organo-mineral complexes on mineral dissolution under unsaturated conditions is not well known. In this study, soil samples prepared from an undisturbed forest site were used to determine mineral weathering rates under differing conditions of OM sorption to minerals. Two types of soil samples were generated: 1) soil with OM (C horizon soil from 84-100cm depth), and 2) soil without OM (the same soil as in 1) but with OM removed by heating to 350°for 24 h). Soil samples were column-packed and subjected to intermittent infiltration and drainage to mimic natural rainfall events. Each soil sample type was run in duplicate. The unsaturated condition was created by applying gas pressure to the column, and the unsaturated chemical weathering rates during each cycle were calculated from the effluent concentrations. During a single cycle, when applying the same gas pressure, soils with OM retained more moisture than OM-removed media, indicating increased water retention capacity under the impact of OM. This is consistent with the water retention data measured by evaporation experiments (HYPROP) and the dew point method (WP4C Potential Meter). Correspondingly, silicon (Si) denudation rates indicated that dissolution of silicate minerals was 2-4 times higher in OM soils, suggesting that organo-mineral complexes accelerate mineral dissolution under unsaturated conditions. When combining data from all cycles, the results showed that Si denudation rates were positively related to soil water content: denundation rate increased with increasing water content. Therefore, natural mineral chemical weathering under unsaturated conditions, while widely considered to be facilitated by biological and chemical activities, may also be affected by soil retention properties.

Enzyme dynamics in paddy soils of the rice district (NE Italy) under different cropping patterns

NASA Astrophysics Data System (ADS)

Bini, Claudio; Nadimi-Goki, Mandana; Kato, Yoichi; Fornasier, Flavio; Wahsha, Mohammad; Spiandorello, Massimo

2014-05-01

The recent widespread interest on soil enzymes is due to the need to develop sensitive indicators of soil quality that reflect the effects of land management on soil and assist land managers in promoting long-term sustainability of terrestrial ecosystems. The activities of six important enzymes involved in C, N, P, and S cycling were investigated in a paddy soil from the Veneto region, Italy, in four different rotation systems (rice-rice-rice: R-R-R; soya-rice-rice: S-R-R; fallow-rice: F-R; pea-soya-rice: P-S-R) with three replications in April (after field preparation, field moist condition), June (after seedling, waterlogged soil condition), August (after tillering stage of rice, waterlogged soil condition) and October (after rice harvesting, drained soil condition) over the 2012 growing season. Our results demonstrated that enzyme activities varied with rotation systems and growth stages in paddy soil. Compared with field moist soil, drained soil condition resulted in a significant increase (P < 0.05) of β-glucosidase, arylsulfatase, alkaline and acid phosphatases, leucine aminopeptidase (except of fallow-rice), and chitinase activities in all rotations, while compared with drained soil, early waterlogging (in month of June) significantly decreased (P moist soil> late waterlogged>early waterlogged. There was an inhibitory effect of waterlogging (except P-S-R rotation) for both alkaline and acid phosphatases due to high pH and redox conditions. However, the response of enzymes to waterlogging differed with the chemical species and the cropping pattern. The best rotation system for chitinase, leucine aminopeptidase and β-glucosidase activity (C and N cycles) proved R-R-R, while for arylsulfatase, alkaline and acid phosphatases (P and S cycles) it was the S-R-R. Key Words: enzyme activity, paddy soil, Crop Rotation System, Italy __ Corresponding Author: Mandana Nadimi-Goki, Tel.: +39 3891356251 E-mail address: mandy.nadimi@gmail.com

Temporal variability of soil water repellency in field conditions under humid Mediterranean climate (South of Spain)

NASA Astrophysics Data System (ADS)

Martinez-Murillo, Juan F.; Gabarron-Galeote, Miguel A.; Ruiz-Sinoga, Jose D.

2013-04-01

Soil water repellency (SWR) has become an important field of scientific study because of its effects on soil hydrological behavior, including reduced matrix infiltration, development of fingered flow in structural or textural preferential flow paths, irregular wetting fronts, and increased runoff generation and soil erosion. The aim of this study is to evaluate the temporal variability of SWR in Mediterranean rangeland under humid Mediterranean climatic conditions (Tª=14.5 °C; P=1,010 mm y-1) in South of Spain. Every month from September 2008 to May 2009 (rainy season), soil moisture and SWR was measured in field conditions by means of gravimetric method and Water Drop Penetration Test, respectively. The entire tests were performed in differente eco-geomorphological conditions in the experimental site: North and South aspect hillslopes and beneath shrub and bare soil in every of them. The results indicate that: i) climatic conditions seem to be more transcendent than the vegetal cover for explaining the temporal variability of SWR in field conditions; ii) thus, SWR appears to be controlled by the antecedent rainfall and soil moisture; iii) more severity SWR were observed in patches characterized by sandier soils and/or greater organic matter contents; and iv) the factor 'hillslope aspect' was not found very influential in the degree of SWR.

A modelling approach to evaluate the long-term effect of soil texture on spring wheat productivity under a rain-fed condition.

PubMed

He, Yong; Hou, Lingling; Wang, Hong; Hu, Kelin; McConkey, Brian

2014-07-30

Soil surface texture is an important environmental factor that influences crop productivity because of its direct effect on soil water and complex interactions with other environmental factors. Using 30-year data, an agricultural system model (DSSAT-CERES-Wheat) was calibrated and validated. After validation, the modelled yield and water use (WU) of spring wheat (Triticum aestivum L.) from two soil textures (silt loam and clay) under rain-fed condition were analyzed. Regression analysis showed that wheat grown in silt loam soil is more sensitive to WU than wheat grown in clay soil, indicating that the wheat grown in clay soil has higher drought tolerance than that grown in silt loam. Yield variation can be explained by WU other than by precipitation use (PU). These results demonstrated that the DSSAT-CERES-Wheat model can be used to evaluate the WU of different soil textures and assess the feasibility of wheat production under various conditions. These outcomes can improve our understanding of the long-term effect of soil texture on spring wheat productivity in rain-fed condition.

Pore-scale investigation on the response of heterotrophic respiration to moisture conditions in heterogeneous soils

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

Yan, Zhifeng; Liu, Chongxuan; Todd-Brown, Katherine E.

The relationship between microbial respiration rate and soil moisture content is an important property for understanding and predicting soil organic carbon degradation, CO 2 production and emission, and their subsequent effects on climate change. This paper reports a pore-scale modeling study to investigate the response of heterotrophic respiration to moisture conditions in soils and to evaluate various factors that affect this response. X-ray computed tomography was used to derive soil pore structures, which were then used for pore-scale model investigation. The pore-scale results were then averaged to calculate the effective respiration rates as a function of water content in soils.more » The calculated effective respiration rate first increases and then decreases with increasing soil water content, showing a maximum respiration rate at water saturation degree of 0.75 that is consistent with field and laboratory observations. The relationship between the respiration rate and moisture content is affected by various factors, including pore-scale organic carbon bioavailability, the rate of oxygen delivery, soil pore structure and physical heterogeneity, soil clay content, and microbial drought resistivity. Simulations also illustrates that a larger fraction of CO 2 produced from microbial respiration can be accumulated inside soil cores under higher saturation conditions, implying that CO 2 flux measured on the top of soil cores may underestimate or overestimate true soil respiration rates under dynamic moisture conditions. Overall, this study provides mechanistic insights into the soil respiration response to the change in moisture conditions, and reveals a complex relationship between heterotrophic microbial respiration rate and moisture content in soils that is affected by various hydrological, geochemical, and biophysical factors.« less

A deep learning framework to discern and count microscopic nematode eggs.

PubMed

Akintayo, Adedotun; Tylka, Gregory L; Singh, Asheesh K; Ganapathysubramanian, Baskar; Singh, Arti; Sarkar, Soumik

2018-06-14

In order to identify and control the menace of destructive pests via microscopic image-based identification state-of-the art deep learning architecture is demonstrated on the parasitic worm, the soybean cyst nematode (SCN), Heterodera glycines. Soybean yield loss is negatively correlated with the density of SCN eggs that are present in the soil. While there has been progress in automating extraction of egg-filled cysts and eggs from soil samples counting SCN eggs obtained from soil samples using computer vision techniques has proven to be an extremely difficult challenge. Here we show that a deep learning architecture developed for rare object identification in clutter-filled images can identify and count the SCN eggs. The architecture is trained with expert-labeled data to effectively build a machine learning model for quantifying SCN eggs via microscopic image analysis. We show dramatic improvements in the quantification time of eggs while maintaining human-level accuracy and avoiding inter-rater and intra-rater variabilities. The nematode eggs are correctly identified even in complex, debris-filled images that are often difficult for experts to identify quickly. Our results illustrate the remarkable promise of applying deep learning approaches to phenotyping for pest assessment and management.

Environmental challenges threatening the growth of urban agriculture in the United States.

PubMed

Wortman, Sam E; Lovell, Sarah Taylor

2013-09-01

Urban agriculture, though often difficult to define, is an emerging sector of local food economies in the United States. Although urban and agricultural landscapes are often integrated in countries around the world, the establishment of mid- to large-scale food production in the U.S. urban ecosystem is a relatively new development. Many of the urban agricultural projects in the United States have emerged from social movements and nonprofit organizations focused on urban renewal, education, job training, community development, and sustainability initiatives. Although these social initiatives have traction, critical knowledge gaps exist regarding the science of food production in urban ecosystems. Developing a science-based approach to urban agriculture is essential to the economic and environmental sustainability of the movement. This paper reviews abiotic environmental factors influencing urban cropping systems, including soil contamination and remediation; atmospheric pollutants and altered climatic conditions; and water management, sources, and safety. This review paper seeks to characterize the limited state of the science on urban agricultural systems and identify future research questions most relevant to urban farmers, land-use planners, and environmental consultants. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

An Overview of the Geological and Geotechnical Aspects of the New Railway Line in the Lower Inn Valley

NASA Astrophysics Data System (ADS)

Eder, Stefan; Poscher, Gerhard; Sedlacek, Christoph

The new railway line in the lower Inn-valley is part of the Brenner railway axis from Munich to Verona (feeder north). The first section between the villages of Kundl and Radfeld, west of Wörgl, and the village of Baumkirchen, east of Innsbruck, will become one of the biggest infrastructure projects ever built in Austria, with a length of approx. 43 km and an underground portion of approx. 80%. The article gives an overview of the various geologic formations - hard rock sections in the valley slopes, different water-saturated gravel and sand formations in the valley floor and geotechnically difficult conditions in sediments of Quaternary terraces. It also describes the methodology of the soil reconnaissance using groundwater models for hydrogeologic estimations, core drillings for evaluating geologic models and describes the experiences gained from the five approx. 7.5 km long reconnaissance tunnels for geotechnical and hydrogeological testing. The results of the soil reconnaissance were used to plan different construction methods, such as excavation in soft rock under a jet grouting roof and compressed-air, as well as mechanised shield with fluid support.

Development of near-zero water consumption cement materials via the geopolymerization of tektites and its implication for lunar construction

PubMed Central

Wang, Kai-tuo; Tang, Qing; Cui, Xue-min; He, Yan; Liu, Le-ping

2016-01-01

The environment on the lunar surface poses some difficult challenges to building long-term lunar bases; therefore, scientists and engineers have proposed the creation of habitats using lunar building materials. These materials must meet the following conditions: be resistant to severe lunar temperature cycles, be stable in a vacuum environment, have minimal water requirements, and be sourced from local Moon materials. Therefore, the preparation of lunar building materials that use lunar resources is preferred. Here, we present a potential lunar cement material that was fabricated using tektite powder and a sodium hydroxide activator and is based on geopolymer technology. Geopolymer materials have the following properties: approximately zero water consumption, resistance to high- and low-temperature cycling, vacuum stability and good mechanical properties. Although the tektite powder is not equivalent to lunar soil, we speculate that the alkali activated activity of lunar soil will be higher than that of tektite because of its low Si/Al composition ratio. This assumption is based on the tektite geopolymerization research and associated references. In summary, this study provides a feasible approach for developing lunar cement materials using a possible water recycling system based on geopolymer technology. PMID:27406467

Development of near-zero water consumption cement materials via the geopolymerization of tektites and its implication for lunar construction.

PubMed

Wang, Kai-Tuo; Tang, Qing; Cui, Xue-Min; He, Yan; Liu, Le-Ping

2016-07-13

The environment on the lunar surface poses some difficult challenges to building long-term lunar bases; therefore, scientists and engineers have proposed the creation of habitats using lunar building materials. These materials must meet the following conditions: be resistant to severe lunar temperature cycles, be stable in a vacuum environment, have minimal water requirements, and be sourced from local Moon materials. Therefore, the preparation of lunar building materials that use lunar resources is preferred. Here, we present a potential lunar cement material that was fabricated using tektite powder and a sodium hydroxide activator and is based on geopolymer technology. Geopolymer materials have the following properties: approximately zero water consumption, resistance to high- and low-temperature cycling, vacuum stability and good mechanical properties. Although the tektite powder is not equivalent to lunar soil, we speculate that the alkali activated activity of lunar soil will be higher than that of tektite because of its low Si/Al composition ratio. This assumption is based on the tektite geopolymerization research and associated references. In summary, this study provides a feasible approach for developing lunar cement materials using a possible water recycling system based on geopolymer technology.

Microbial denitrification dominates nitrate losses from forest ecosystems

PubMed Central

Fang, Yunting; Koba, Keisuke; Makabe, Akiko; Takahashi, Chieko; Zhu, Weixing; Hayashi, Takahiro; Hokari, Azusa A.; Urakawa, Rieko; Bai, Edith; Houlton, Benjamin Z.; Xi, Dan; Zhang, Shasha; Matsushita, Kayo; Tu, Ying; Liu, Dongwei; Zhu, Feifei; Wang, Zhenyu; Zhou, Guoyi; Chen, Dexiang; Makita, Tomoko; Toda, Hiroto; Liu, Xueyan; Chen, Quansheng; Zhang, Deqiang; Li, Yide; Yoh, Muneoki

2015-01-01

Denitrification removes fixed nitrogen (N) from the biosphere, thereby restricting the availability of this key limiting nutrient for terrestrial plant productivity. This microbially driven process has been exceedingly difficult to measure, however, given the large background of nitrogen gas (N2) in the atmosphere and vexing scaling issues associated with heterogeneous soil systems. Here, we use natural abundance of N and oxygen isotopes in nitrate (NO3−) to examine dentrification rates across six forest sites in southern China and central Japan, which span temperate to tropical climates, as well as various stand ages and N deposition regimes. Our multiple stable isotope approach across soil to watershed scales shows that traditional techniques underestimate terrestrial denitrification fluxes by up to 98%, with annual losses of 5.6–30.1 kg of N per hectare via this gaseous pathway. These N export fluxes are up to sixfold higher than NO3− leaching, pointing to widespread dominance of denitrification in removing NO3− from forest ecosystems across a range of conditions. Further, we report that the loss of NO3− to denitrification decreased in comparison to leaching pathways in sites with the highest rates of anthropogenic N deposition. PMID:25605898

Natural recovery of biological soil crusts after disturbance

USGS Publications Warehouse

Weber, Bettina; Bowker, Matthew A.; Zhang, Yuanming; Belnap, Jayne

2016-01-01

Natural recovery of biological soil crusts (biocrusts) is influenced by a number of different parameters, such as climate, soil conditions, the severity of disturbance, and the timing of disturbance relative to the climatic conditions. In recent studies, it has been shown that recovery is often not linear, but a highly dynamic process directly influenced by non-linear external parameters as extraordinary climatic conditions (e.g., particularly dry or wet year). Natural recovery often follows a general succession pattern, starting out with cyanobacteria and algae, which is then followed by lichens and bryophytes at a later stage. However, this general sequence can be altered by parameters like dust deposition, fire effects, and special climatic conditions as in fog deserts and under mesic climates. Recent studies have proposed that under favorable, stable soil conditions, the initial soil-stabilizing cyanobacteria-dominated succession stages may be omitted and moss-dominated biocrusts can develop in the initial phases of biocrust development. During natural recovery of biocrusts, soil properties change, e.g., soil nutrient and organic matter contents increase. Also, silt and clay contents of encrusted soils increase with biocrust maturity, which may be caused by two mechanisms, i.e. entrapment of fine soil particles by biocrusts and the new formation of smaller particles by weathering of the existing substrate.

Analysis of the adhesion of Pseudomonas putida NCIB 9816-4 to a silica gel as a model soil using extended DLVO theory.

PubMed

Hwang, Geelsu; Lee, Chang-Ha; Ahn, Ik-Sung; Mhin, Byung Jin

2010-07-15

The extended Derjaguin-Landau-Verwey-Overbeek (DLVO) theory was applied to explain the hydrophobic interaction-mediated adhesion of Pseudomonas putida NCIB 9816-4 to soil. Soil particles are heterogeneous, and it is difficult to define consistent physico-chemical properties such as a contact angle and zeta potential. Hence, a silica gel and a silanized (3-aminopropyltriethoxysilane-coated) silica gel, which showed greater hydrophobicity than the unmodified silica gel, were used as model soils. Gibbs energies for the cell adhesion to the silica gels were calculated with the physico-chemical properties of the microbes and the silica gels and then plotted as a function of the separation distance. The extended DLVO theory successfully explained that the adhesion of P. putida NCIB 9816-4 to the silica gel, a model soil, was primarily caused by hydrophobic interaction. 2010 Elsevier B.V. All rights reserved.

Successful implementation of biochar carbon sequestration in European soils requires additional benefits and close collaboration with the bioenergy sector

NASA Astrophysics Data System (ADS)

Hauggaard-Nielsen, Henrik; Müller-Stöver, Dorette; Bruun, Esben W.; Petersen, Carsten T.

2014-05-01

Biochar soil application has been proposed as a measure to mitigate climate change and on the same time improve soil fertility by increased soil carbon sequestration. However, while on tropical soils the beneficial effects of biochar application on crop growth often become immediately apparent, it has been shown to be more difficult to demonstrate these effects on the more fertile soils in temperate regions. Therefore and because of the lack of carbon credits for farmers, it is necessary to link biochar application to additional benefits, both related to agricultural as well as to bioenergy production. Thermal gasification of biomass is an efficient (95% energy efficiency) and flexible way (able to cope with many different and otherwise difficult-to-handle biomass fuels) to generate bioenergy, while producing a valuable by-product - gasification biochar, containing recalcitrant carbon and essential crop nutrients. The use of the residual char product in agricultural soils will add value to the technology as well as result in additional soil benefits such as providing plant nutrients and improving soil water-holding capacity while reducing leaching risks. From a soil column (30 x 130 cm) experiment with gasification straw biochar amendment to coarse sandy subsoil increased root density of barley at critical depths in the soil profile reducing the mechanical resistance was shown, increasing yields, and the soil's capacity to store plant available water. Incorporation of residuals from a bioenergy technology like gasification show great potentials to reduce subsoil constraints increasing yield potentials on poor soils. Another advantage currently not appropriately utilized is recovery of phosphorus (P). In a recent pot experiments char products originating from low-temperature gasification of various biofuels were evaluated for their suitability as P fertilizers. Wheat straw gasification biochar generally had a low P content but a high P plant availability. To improve the fertilizer value while keeping a high carbon content in the char, the gasification of a combination of sewage sludge and wheat straw was implemented, resulting in a char product with a promising performance as a fertilizer and soil amendment. To implement gasification-biochar as a promising soil improver on the marked, independently of potential carbon market developments and CO2 certificates, stakeholder involvement is strongly required. In a newly established project consortium Bregentved Estate (one of Europe's largest agriculture companies) and the DONG Energy company (one of the leading energy groups in Northern Europe) are in a joint effort trying to integrate the economic matrix of i) biomass needed for bioenergy, ii) profit from energy generation and iii) soil advantages gained from biochar application. Experiments are conducted with a 6MW biomass gasification demonstration plant producing straw biochar used in field plots (12 m x 250 m).

Calibration of the soil conditioning index (SCI) to soil organic carbon in the southeastern USA

USDA-ARS?s Scientific Manuscript database

Prediction of soil organic C sequestration with adoption of various conservation agricultural management approaches is needed to meet the emerging market for environmental services provided by agricultural land stewardship. The soil conditioning index (SCI) is a relatively simple model used by the ...

Status of the World's Soil Resources Report, Intergovernmental Technical Panel on Soils

EPA Science Inventory

The scope of main objectives of the report are: (a) to provide a global scientific assessment of current and projected soil conditions built on regional data analysis and expertise (b) to explore the implications of these soil conditions for food security, climate change, water q...

Innovative bio-mediated particulate materials for sustainable maritime transportation infrastructure.

DOT National Transportation Integrated Search

2017-08-15

The mechanical properties of sandy soils in the coastal area and beach sands often do not satisfy construction expectation for maritime transportation infrastructure. The salty, loose sand makes it difficult for quick construction of port, building a...

Environmental Pollutants

USDA-ARS?s Scientific Manuscript database

Managing animal production systems to reduce environmental impacts is most difficult for air quality. Water and soil quality responses to animal production can be managed through planning and understanding the risk of spills, overapplication, or improper use of manure. Escape of gaseous or particula...

HORIZONTAL LASAGNA TO BIOREMEDIATE TCE

EPA Science Inventory

Removal of TCE from these tight clay soils has been technically difficult and expensive. However, the LASAGNATM technique allows movement of the TCE into treatment zones for biodegradation or dechlorination in place, lessening the costs and exposure to TCE. Electroosmosis was c...

Application of X-ray computed microtomography to soil craters formed by raindrop splash

NASA Astrophysics Data System (ADS)

Beczek, Michał; Ryżak, Magdalena; Lamorski, Krzysztof; Sochan, Agata; Mazur, Rafał; Bieganowski, Andrzej

2018-02-01

The creation of craters on the soil surface is part of splash erosion. Due to the small size of these craters, they are difficult to study. The main aim of this paper was to test X-ray computed microtomography to investigate craters formed by raindrop impacts. Measurements were made on soil samples moistened to three different levels corresponding with soil water potentials of 0.1, 3.16 and 16 kPa. Using images obtained by X-ray microtomography, geometric parameters of the craters were recorded and analysed. X-ray computed microtomography proved to be a useful and efficient tool for the investigation of craters formed on the soil surface after the impact of water drops. The parameters of the craters changed with the energy of the water drops and were dependent on the initial moisture content of the soil. Crater depth is more dependent on the increased energy of the water drop than crater diameter.

Genomic analysis of differentiation between soil types reveals candidate genes for local adaptation in Arabidopsis lyrata.

PubMed

Turner, Thomas L; von Wettberg, Eric J; Nuzhdin, Sergey V

2008-09-11

Serpentine soil, which is naturally high in heavy metal content and has low calcium to magnesium ratios, comprises a difficult environment for most plants. An impressive number of species are endemic to serpentine, and a wide range of non-endemic plant taxa have been shown to be locally adapted to these soils. Locating genomic polymorphisms which are differentiated between serpentine and non-serpentine populations would provide candidate loci for serpentine adaptation. We have used the Arabidopsis thaliana tiling array, which has 2.85 million probes throughout the genome, to measure genetic differentiation between populations of Arabidopsis lyrata growing on granitic soils and those growing on serpentinic soils. The significant overrepresentation of genes involved in ion transport and other functions provides a starting point for investigating the molecular basis of adaptation to soil ion content, water retention, and other ecologically and economically important variables. One gene in particular, calcium-exchanger 7, appears to be an excellent candidate gene for adaptation to low CaratioMg ratio in A. lyrata.

Petrographic characterization of lunar soils: Application of x ray digital-imaging to quantitative and automated analysis

NASA Technical Reports Server (NTRS)

Higgins, Stefan J.; Patchen, Allan; Chambers, John G.; Taylor, Lawrence A.; Mckay, David S.

1994-01-01

The rocks and soils of the moon will be the raw materials for various engineering needs at a lunar base, such as sources of hydrogen, oxygen, metals, etc. The material of choice for most of the bulk needs is the regolith and its less than 1 cm fraction, the soil. For specific mineral resources it may be necessary to concentrate minerals from either rocks or soils. Therefore, quantitative characterizations of these rocks and soils are necessary in order to better define their mineral resource potential. However, using standard point-counting microscopic procedures, it is difficult to quantitatively determine mineral abundances and virtually impossible to obtain data on mineral distributions within grains. As a start to fulfilling these needs, Taylor et al. and Chambers et al. have developed a procedure for characterization of crushed lunar rocks using x ray digital imaging. The development of a similar digital imaging procedure for lunar soils as obtained from a spectrometer is described.

Biological technologies for the remediation of co-contaminated soil.

PubMed

Ye, Shujing; Zeng, Guangming; Wu, Haipeng; Zhang, Chang; Dai, Juan; Liang, Jie; Yu, Jiangfang; Ren, Xiaoya; Yi, Huan; Cheng, Min; Zhang, Chen

2017-12-01

Compound contamination in soil, caused by unreasonable waste disposal, has attracted increasing attention on a global scale, particularly since multiple heavy metals and/or organic pollutants are entering natural ecosystem through human activities, causing an enormous threat. The remediation of co-contaminated soil is more complicated and difficult than that of single contamination, due to the disparate remediation pathways utilized for different types of pollutants. Several modern remediation technologies have been developed for the treatment of co-contaminated soil. Biological remediation technologies, as the eco-friendly methods, have received widespread concern due to soil improvement besides remediation. This review summarizes the application of biological technologies, which contains microbial technologies (function microbial remediation and composting or compost addition), biochar, phytoremediation technologies, genetic engineering technologies and biochemical technologies, for the remediation of co-contaminated soil with heavy metals and organic pollutants. Mechanisms of these technologies and their remediation efficiencies are also reviewed. Based on this study, this review also identifies the future research required in this field.

Peatland water repellency: Importance of soil water content, moss species, and burn severity

NASA Astrophysics Data System (ADS)

Moore, P. A.; Lukenbach, M. C.; Kettridge, N.; Petrone, R. M.; Devito, K. J.; Waddington, J. M.

2017-11-01

Wildfire is the largest disturbance affecting peatlands, with northern peat reserves expected to become more vulnerable to wildfire as climate change enhances the length and severity of the fire season. Recent research suggests that high water table positions after wildfire are critical to limit atmospheric carbon losses and enable the re-establishment of keystone peatland mosses (i.e. Sphagnum). Post-fire recovery of the moss surface in Sphagnum-feathermoss peatlands, however, has been shown to be limited where moss type and burn severity interact to result in a water repellent surface. While in situ measurements of moss water repellency in peatlands have been shown to be greater for feathermoss in both a burned and unburned state in comparison to Sphagnum moss, it is difficult to separate the effect of water content from species. Consequently, we carried out a laboratory based drying experiment where we compared the water repellency of two dominant peatland moss species, Sphagnum and feathermoss, for several burn severity classes including unburned samples. The results suggest that water repellency in moss is primarily controlled by water content, where a sharp threshold exists at gravimetric water contents (GWC) lower than ∼1.4 g g-1. While GWC is shown to be a strong predictor of water repellency, the effect is enhanced by burning. Based on soil water retention curves, we suggest that it is highly unlikely that Sphagnum will exhibit strong hydrophobic conditions under field conditions.

Anthropogenic Disturbance of Montane Meadows May Cause Substantial Loss of Soil Carbon to the Atmosphere

NASA Astrophysics Data System (ADS)

Reed, C. C.; Sullivan, B. W.; Hart, S. C.; Drew, M.; Merrill, A.

2016-12-01

High-elevation meadows are biological hotspots that contain high densities of soil carbon (C). The capacity of these ecosystems to sequester C depends on a combination of high primary productivity, seasonally low temperatures, and anaerobic soil conditions associated with water tables at or near the soil surface. However, anthropogenic disturbances in many montane meadows in California's Sierra Nevada have lowered water tables, decreased primary productivity, and created aerobic soil conditions - changes that may alter the balance of greenhouse gas (GHG) emissions and reverse meadows from a net C sink to a net source. Recently, C policy in California has spurred interest in the potential of hydrologic restoration to increase C sequestration in meadows. However, soil C pools and fluxes in degraded meadows must be quantified before the impacts of restoration can accurately be assessed. In this study, we measured soil C stocks in surface soil (1 m) and annual soil GHG fluxes (carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O)) in three degraded, northern Sierra Nevada meadows. In a parallel laboratory incubation, we manipulated meadow soil water content to determine target goals for restoration of anaerobic conditions. Our results suggest that degraded meadows contain large reservoirs of existing C, but that this C may be vulnerable to decomposition under current conditions. Soil CO2 fluxes ranged from 26.7-33.1 Mg of CO2 ha-1 y-1, roughly equivalent to the amount of C sequestered annually by 70 acres of U.S. forests. These high rates of soil respiration, combined with low primary productivity, resulted in substantial losses of soil C with implications for climate change, ecosystem function, and restoration. Soils from these meadows were a net source of N2O and a net sink of CH4, but these fluxes were 4 orders of magnitude smaller than CO2. Also, we found substantial GHG emissions persist in these organic soils at peak soil moisture, suggesting that restoration may need to sustain soil water holding capacities in excess of 115%, and possibly 200%, for anaerobic soil conditions to return. These findings highlight the need to conserve properly functioning meadows and provide target conditions for optimal restoration of degraded meadows.

Cultural Resources Intensive Survey, With Testing, of the Millington, Naval Base Levee Construction Site, Millington Shelby County, Tennessee.

DTIC Science & Technology

1990-01-01

terraces, and fall and spring migratory waterfowl in areas of seasonally standing water . Hickory nuts thus appear to be the most strategic resource, * in...for agriculture . Such soils are difficult to work until late in the planting season, are subject to wet-year moisture damage to crops, and provide an...effective barrier to root growth during dry years. Prehistoric agricultural activities tend to focus on better-drained soils such as Collins, Memphis

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.

NASA SMAP Images Show Texas Soil Moisture Conditions Before/After Hurricane Harvey's Landfall

NASA Image and Video Library

2017-08-29

Images of soil moisture conditions in Texas near Houston, generated by NASA's Soil Moisture Active Passive (SMAP) satellite before and after the landfall of Hurricane Harvey can be used to monitor changing ground conditions due to Harvey's rainfall. As seen in the left panel, SMAP observations show that soil surface conditions were already very wet a few days before the hurricane made landfall (August 21/22), with moisture levels in the 20 to 40 percent range. Such saturated soil surfaces contributed to the inability of water to infiltrate more deeply into soils, thereby increasing the likelihood of flooding. After Harvey made landfall, the southwest portion of Houston became exceptionally wet, as seen in the right panel image from August 25/26, signaling the arrival of heavy rains and widespread flooding. https://photojournal.jpl.nasa.gov/catalog/PIA21926

Using growth-based methods to determine direct effects of salinity on soil microbial communities

NASA Astrophysics Data System (ADS)

Rath, Kristin; Rousk, Johannes

2015-04-01

Soil salinization is a widespread agricultural problem and increasing salt concentrations in soils have been found to be correlated with decreased microbial activity. A central challenge in microbial ecology is to link environmental factors, such as salinity, to responses in the soil microbial community. That is, it can be difficult to distinguish direct from indirect effects. In order to determine direct salinity effects on the community we employed the ecotoxicological concept of Pollution-Induced Community Tolerance (PICT). This concept is built on the assumption that if salinity had an ecologically relevant effect on the community, it should have selected for more tolerant species and strains, resulting in an overall higher community tolerance to salt in communities from saline soils. Growth-based measures, such as the 3H-leucine incorporation into bacterial protein , provide sensitive tools to estimate community tolerance. They can also provide high temporal resolution in tracking changes in tolerance over time. In our study we used growth-based methods to investigate: i) at what levels of salt exposure and over which time scales salt tolerance can be induced in a non-saline soil, and (ii) if communities from high salinity sites have higher tolerance to salt exposure along natural salinity gradients. In the first part of the study, we exposed a non-saline soil to a range of salinities and monitored the development of community tolerance over time. We found that community tolerance to intermediate salinities up to around 30 mg NaCl per g soil can be induced at relatively short time scales of a few days, providing evidence that microbial communities can adapt rapidly to changes in environmental conditions. In the second part of the study we used soil samples originating from natural salinity gradients encompassing a wide range of salinity levels, with electrical conductivities ranging from 0.1 dS/m to >10 dS/m. We assessed community tolerance to salt by measuring the bacterial growth response to added NaCl in a soil suspension. The bacterial community tolerance to salt increased along the salt gradients with higher in situ soil salinity. In samples from the low-saline end of the gradient, bacterial growth rates in the soil suspension showed a clear concentration-response relationship to NaCl resulting in inhibition curves. This relationship gradually changed toward higher salt concentrations. In soil samples from high salinity sites, bacterial growth was no longer inhibited by adding high concentrations of NaCl to the bacterial soil suspension. In fact, adding NaCl even promoted bacterial growth rates. These results show that salinity played an ecologically significant role in shaping communities at the highly saline end of the gradients and provide evidence for a direct salt effect on the microbial community

The Earth on the Other Side of Life (Invited)

NASA Astrophysics Data System (ADS)

Amundson, R.; Ewing, S. A.; Owen, J. J.

2010-12-01

There are important reasons for examining the role of life on Earth surface processes, including better understanding the long term feedbacks between the geosphere and biosphere that maintain Earth habitability, and bracing for the cumulative impact of the Earth’s most invasive species (Homo sapiens) on the earth system. Coming to grips with the importance of life is simply a matter of recognizing the obvious: life mantles most of the planet’s surface and the planet’s climatic boundary conditions would be profoundly different if life on Earth had not evolved. Nearly every process on this planet is mediated in some way by biology . The most difficult aspect of deciphering the exact role of life on Earth surface processes is observationally identifying a “control experiment”- e.g. one where life does not exist. Planetary habitability is linked to the presence of liquid water. Thus, there are two regions on Earth that largely fall outside the rainfall limits of life and that have maintained nearly abiotic conditions for millions of years: the Atacama Desert of northern Chile (warm and very dry) and the Dry Valleys of Antarctica (very cold and dry). Here, we examine the Atacama Desert for the reason that it is the dry end of a continuous decline in rainfall with decreasing latitude in western South America, such that (almost imperceptibly) one eventually crosses a rainfall threshold beyond which most life ceases to exist. The consequence of soil and geomorphic studies along this rainfall gradient have revealed that several important earth surface processes vary montonically with declining rainfall up to the point where vascular plants disappear. At this point, the rates or types of key processes appear to undergo fundamental changes. Geomorphically, soil production/hillslope denudation rates vary within a window of rates over broad ranges in rainfall. However, at the biotic abiotic boundary, erosion rates decline in concert with rainfall. This pattern appears to be related to the feedbacks between soil thickness and soil production rates, and the impact of biology on both reducing surface erosion, and in enhancing the conversion of saprolite to soil. Once plants no longer exist, soil is rapidly stripped as the biological controls are removed. As aridity increases further, soils reappear on the hillslopes due to dust/salt accumulation, but the processes of both soil production and transport shift to slow abiotic mechanisms. Geochemically, N content in soils declines monotonically with rainfall up to the point that plants diappear. At that point, N cycling shifts to entirely abiotic mechanisms, allowing the accumulation of the unusal nitrate deposits that characterize this desert. While the parts of earth without life are unusually dry and/or cold, they offer unique, but also complex, perspectives into the sometimes overwhelming role that life plays on the earth surface. The true challenge to the geosciences is to rapidly acquire this knowledge in order to predict the trajectory of a changing world.

Improved quantification of microbial CH4 oxidation efficiency in arctic wetland soils using carbon isotope fractionation

NASA Astrophysics Data System (ADS)

Preuss, I.; Knoblauch, C.; Gebert, J.; Pfeiffer, E.-M.

2013-04-01

Permafrost-affected tundra soils are significant sources of the climate-relevant trace gas methane (CH4). The observed accelerated warming of the arctic will cause deeper permafrost thawing, followed by increased carbon mineralization and CH4 formation in water-saturated tundra soils, thus creating a positive feedback to climate change. Aerobic CH4 oxidation is regarded as the key process reducing CH4 emissions from wetlands, but quantification of turnover rates has remained difficult so far. The application of carbon stable isotope fractionation enables the in situ quantification of CH4 oxidation efficiency in arctic wetland soils. The aim of the current study is to quantify CH4 oxidation efficiency in permafrost-affected tundra soils in Russia's Lena River delta based on stable isotope signatures of CH4. Therefore, depth profiles of CH4 concentrations and δ13CH4 signatures were measured and the fractionation factors for the processes of oxidation (αox) and diffusion (αdiff) were determined. Most previous studies employing stable isotope fractionation for the quantification of CH4 oxidation in soils of other habitats (such as landfill cover soils) have assumed a gas transport dominated by advection (αtrans = 1). In tundra soils, however, diffusion is the main gas transport mechanism and diffusive stable isotope fractionation should be considered alongside oxidative fractionation. For the first time, the stable isotope fractionation of CH4 diffusion through water-saturated soils was determined with an αdiff = 1.001 ± 0.000 (n = 3). CH4 stable isotope fractionation during diffusion through air-filled pores of the investigated polygonal tundra soils was αdiff = 1.013 ± 0.003 (n = 18). Furthermore, it was found that αox differs widely between sites and horizons (mean αox = 1.017 ± 0.009) and needs to be determined on a case by case basis. The impact of both fractionation factors on the quantification of CH4 oxidation was analyzed by considering both the potential diffusion rate under saturated and unsaturated conditions and potential oxidation rates. For a submerged, organic-rich soil, the data indicate a CH4 oxidation efficiency of 50% at the anaerobic-aerobic interface in the upper horizon. The improved in situ quantification of CH4 oxidation in wetlands enables a better assessment of current and potential CH4 sources and sinks in permafrost-affected ecosystems and their potential strengths in response to global warming.

Improved quantification of microbial CH4 oxidation efficiency in Arctic wetland soils using carbon isotope fractionation

NASA Astrophysics Data System (ADS)

Preuss, I.; Knoblauch, C.; Gebert, J.; Pfeiffer, E.-M.

2012-12-01

Permafrost-affected tundra soils are significant sources of the climate-relevant trace gas methane (CH4). The observed accelerated warming of the Arctic will cause a deeper permafrost thawing followed by increased carbon mineralization and CH4 formation in water saturated tundra soils which might cause a positive feedback to climate change. Aerobic CH4 oxidation is regarded as the key process reducing CH4 emissions from wetlands, but quantification of turnover rates has remained difficult so far. The application of carbon stable isotope fractionation enables the in situ quantification of CH4 oxidation efficiency in arctic wetland soils. The aim of the current study is to quantify CH4 oxidation efficiency in permafrost-affected tundra soils in Russia's Lena River Delta based on stable isotope signatures of CH4. Therefore, depth profiles of CH4 concentrations and δ13CH4-signatures were measured and the fractionation factors for the processes of oxidation (αox) and diffusion (αdiff) were determined. Most previous studies employing stable isotope fractionation for the quantification of CH4 oxidation in soils of other habitats (e.g. landfill cover soils) have assumed a gas transport dominated by advection (αtrans = 1). In tundra soils, however, diffusion is the main gas transport mechanism, aside from ebullition. Hence, diffusive stable isotope fractionation has to be considered. For the first time, the stable isotope fractionation of CH4 diffusion through water-saturated soils was determined with an αdiff = 1.001 ± 0.000 (n = 3). CH4 stable isotope fractionation during diffusion through air-filled pores of the investigated polygonal tundra soils was αdiff = 1.013 ± 0.003 (n = 18). Furthermore, it was found that αox differs widely between sites and horizons (mean αox, = 1.017 ± 0.009) and needs to be determined individually. The impact of both fractionation factors on the quantification of CH4 oxidation was analyzed by considering both the potential diffusion rate under saturated and unsaturated conditions and potential oxidation rates. For a submerged organic rich soil, the data indicate a CH4 oxidation efficiency of 50% at the anaerobic-aerobic interface in the upper horizon. The improved in situ quantification of CH4 oxidation in wetlands enables a better assessment of current and potential CH4 sources and sinks in permafrost affected ecosystems and their potential strengths in response to global warming.

A Field and Laboratory Based Assessment of the Potential of High Frequency Ground Penetrating Radar (HFGPR) to Evaluate the Presence and Spatial Variabilty of Hydrophobic Soil Layers

NASA Astrophysics Data System (ADS)

Weirich, F. H.; Neumann, W.; Campbell, D.

2017-12-01

The presence of fire related hydrophobic (water repellant) soil layers in a wide range of environmental settings can result in greatly increased rates of storm runoff and erosion. In many situations this can contribute to the generation of debris and/or hyperconcentrated flows. While the role of hydrophobic soils in greatly increasing sediment production in such situations is known, the ability to predict the volume of sediment that will be generated by specific storm events has been limited, in part, by limits on the ability to assess the characteristics of hydrophobic soil layers. At present, the most widely accepted method of assessing the presence, strength, extent and persistence of hydrophobic soil layers requires the performance of an in situ water drop penetration test (WDPT). This approach, while effective on a local site, is labor and time intensive and can be difficult to employ on a watershed or even slope wide basis. As part of a wider research effort to develop more effective methods of evaluating the characteristics of hydrophobic soils a combined field and laboratory based program has been undertaken to evaluate the capability of higher frequency ground penetrating radar (HFGPR) to detect and map out the spatial extent, strength, and persistence of hydrophobic soil layers. This has involved the testing of HFGPR systems at several field site in burnt watersheds in Southern California as well as a program of laboratory tests on samples of fire impacted soils collected from the same watersheds. The field tests were undertaken on sites ranging from a location that had burnt a few weeks earlier to locations where over 5 years had passed since a burn took place. Laboratory samples of soils were taken from the same range of sites and used in the laboratory tests. In parallel with the HFGPR testing WDPT's were used to confirm the findings of the HFGPR approach. Both the field and laboratory results indicate that the use of HFGPR, under appropriate soil moisture conditions, is capable of mapping out the presence, spatial extent, and persistence of hydrophobic soil layers. Layers at depth ranging from 1-6 cm were successfully mapped. The persistence of layers on some sites 5 years after a burn were also able to be measured using this approach. Work to further refine both the approach and its limitations is ongoing.

A dynamic organic soil biogeochemical model for simulating the effects of wildfire on soil environmental conditions and carbon dynamics of black spruce forests

Treesearch

Shuhua Yi; A. David McGuire; Eric Kasischke; Jennifer Harden; Kristen Manies; Michelle Mack; Merritt Turetsky

2010-01-01

Ecosystem models have not comprehensively considered how interactions among fire disturbance, soil environmental conditions, and biogeochemical processes affect ecosystem dynamics in boreal forest ecosystems. In this study, we implemented a dynamic organic soil structure in the Terrestrial Ecosystem Model (DOS-TEM) to investigate the effects of fire on soil temperature...

Soil Oxidation-Reduction in Wetlands and Its Impact on Plant Functioning

PubMed Central

Pezeshki, S. R.; DeLaune, R. D.

2012-01-01

Soil flooding in wetlands is accompanied by changes in soil physical and chemical characteristics. These changes include the lowering of soil redox potential (Eh) leading to increasing demand for oxygen within the soil profile as well as production of soil phytotoxins that are by-products of soil reduction and thus, imposing potentially severe stress on plant roots. Various methods are utilized for quantifying plant responses to reducing soil conditions that include measurement of radial oxygen transport, plant enzymatic responses, and assessment of anatomical/morphological changes. However, the chemical properties and reducing nature of soil environment in which plant roots are grown, including oxygen demand, and other associated processes that occur in wetland soils, pose a challenge to evaluation and comparison of plant responses that are reported in the literature. This review emphasizes soil-plant interactions in wetlands, drawing attention to the importance of quantifying the intensity and capacity of soil reduction for proper evaluation of wetland plant responses, particularly at the process and whole-plant levels. Furthermore, while root oxygen-deficiency may partially account for plant stress responses, the importance of soil phytotoxins, produced as by-products of low soil Eh conditions, is discussed and the need for development of methods to allow differentiation of plant responses to reduced or anaerobic soil conditions vs. soil phytotoxins is emphasized. PMID:24832223

Plant-soil feedbacks: a comparative study on the relative importance of soil feedbacks in the greenhouse versus the field.

PubMed

Heinze, Johannes; Sitte, M; Schindhelm, A; Wright, J; Joshi, J

2016-06-01

Interactions between plants and soil microorganisms influence individual plant performance and thus plant-community composition. Most studies on such plant-soil feedbacks (PSFs) have been performed under controlled greenhouse conditions, whereas no study has directly compared PSFs under greenhouse and natural field conditions. We grew three grass species that differ in local abundance in grassland communities simultaneously in the greenhouse and field on field-collected soils either previously conditioned by these species or by the general grassland community. As soils in grasslands are typically conditioned by mixes of species through the patchy and heterogeneous plant species' distributions, we additionally compared the effects of species-specific versus non-specific species conditioning on PSFs in natural and greenhouse conditions. In almost all comparisons PSFs differed between the greenhouse and field. In the greenhouse, plant growth in species-specific and non-specific soils resulted in similar effects with neutral PSFs for the most abundant species and positive PSFs for the less abundant species. In contrast, in the field all grass species tested performed best in non-specific plots, whereas species-specific PSFs were neutral for the most abundant and varied for the less abundant species. This indicates a general beneficial effect of plant diversity on PSFs in the field. Controlled greenhouse conditions might provide valuable insights on the nominal effects of soils on plants. However, the PSFs observed in greenhouse conditions may not be the determining drivers in natural plant communities where their effects may be overwhelmed by the diversity of abiotic and biotic above- and belowground interactions in the field.

Soil microbial respiration (CO2) of natural and anthropogenically-transformed ecosystems in Moscow region, Russia

NASA Astrophysics Data System (ADS)

Ivashchenko, Kristina; Ananyeva, Nadezhda; Rogovaya, Sofia; Vasenev, Viacheslav

2016-04-01

The CO2 concentration in modern atmosphere is increasing and one of the most reasons of it is land use changing. It is related not only with soil plowing, but also with growing urbanization and, thereby, forming the urban ecosystems. Such conversion of soil cover might be affected by efflux CO2 from soil into atmosphere. The soil CO2 efflux mainly supplies by soil microorganisms respiration (contribution around 70-90%) and plant roots respiration. Soil microbial respiration (MR) is determined in the field (in situ) and laboratory (in vitro) conditions. The measurement of soil MR in situ is labour-consuming, and for district, region and country areas it is difficult carried. We suggest to define the MR of the upper highest active 10 cm mineral soil layer (in vitro) followed by the accounting of area for different ecosystems in large region of Russia. Soils were sampled (autumn, 2011) in natural (forest, meadow) and anthropogenically-transformed (arable, urban) ecosystems of Sergiev-Posad, Taldom, Voskresenk, Shatura, Serpukhov and Serbryanye Prudy districts in Moscow region. In soil samples (total 156) the soil MR (24 h, 22°C, 60% WHC) were measured after preincubation procedure (7 d., 22°C, 55% WHC). The soil MR ranged from 0.13 (urban) to 5.41 μg CO2-C g-1 h-1 (meadow), the difference between these values was 42 times. Then, the soil MR values (per unit soil weight) were calculated per unit soil area (1 m2), the layer thickness of which was 0.1 m (soil volume weight was equaled 1 g cm-3). The high MR values were noted for forests soil (832-1410 g CO2-C m-2 yr-1) of studied districts, and the low MR values were for arable and urban soils (by 1.6-3.2 and 1.3-2.7 times less compared to forests, respectively). The MR rate of urban soil in Voskresenk district was comparable to that of corresponding meadows and it was even higher (in average by 2.3 times) in Serpukhov district. The soil MR rate of studied cities was higher by 20%, than in corresponding arable soils (438-517 g CO2-C m-2 yr-1). Furthermore, we took into account the area of different ecosystems, which achieves 47% for forests, 6, 30 and 5% for meadows, arable and cities, respectively, of total area in studied districts. It turns that the soil MR of forests area was highest reaching 281-1391 thousand tons CO2-C yr-1. The soil MR of meadows area was reached 15-76 thousand tons CO2-C yr-1, that was by 1.6-2.7 times lower than those in cities of the most urbanized districts (Sergiev-Posad, Voskresenk and Serpukhov). Suggested approach allows us to compare soil MR (main biogenic CO2 source) of different ecosystems' area in Moscow region. It was shown that urban soils might be significant source of CO2 in atmosphere, therefore they should be taken into account for balance calculation of carbon cycle, and especially at regional level. This approach might useful for express assessment of microbial soil CO2 efflux, soil ecological monitoring, and predictive estimation of soil CO2 efflux for a wide range of ecosystems, including human activities disturbed ones.

Interactions with soils conditioned by different vegetation: a potential explanation of bromus tectorum L. invasion into salt-deserts?

USDA-ARS?s Scientific Manuscript database

Invasion by Bromus tectorum L. may condition the soil and increase nutrient availability. We hypothesized that nutrient poor soils of the arid Honey Lake Valley of northeastern California U.S.A., similar in physical and chemical properties, but conditioned by either B. tectorum, Krascheninniko...

Selective determination of heavy metals (Cd, Pb, Cr) speciation forms from hortic anthrosols

NASA Astrophysics Data System (ADS)

Bulgariu, Dumitru; Bulgariu, Laura; Filipov, Feodor; Astefanei, Dan; Stoleru, Vasile

2010-05-01

In soils from glass houses, the speciation and inter-phases distribution processes of heavy metals have a particular dynamic, different in comparison with those from non-protected soils. The predominant distribution forms of heavy metals in such soils types are: complexes with low mass organic molecules, organic-mineral complexes, complexes with inorganic ligands (hydroxide-complexes, carbonate-complexes, sulphate-complexes, etc.) and basic salts. All of these have high stabilities in conditions of soils from glass houses, and in consequence, the separation and determination of speciation forms (which is directly connected with biodisponibility of heavy metals) by usual methods id very difficult and has a high uncertain degree. In this study is presented an original method for the selective separation and differentiation of speciation forms of heavy metals from glass houses soils, which is based by the combination of solid-liquid sequential extraction (SPE) with the extraction in aqueous polymer-inorganic salt two-phase systems (ABS). The soil samples used for this study have been sampled from three different locations (glass houses from Iasi, Barlad and Bacau - Romania) where the vegetables cultivation have been performed by three different technologies. In this way was estimated the applicability and the analytical limits of method proposed by as, in function of the chemical-mineralogical and physical-chemical characteristics of soils. As heavy metals have been studied cadmium, lead and chromium, all being known for their high toxicity. The procedure used for the selective separation and differentiation of speciation forms of heavy metals from glass houses soils has two main steps: (i) non-destructive separation of chemical-mineralogical associations and aggregates from soils samples - for this the separation method with heavy liquids (bromophorme) and isodynamic magnetic method have been used; (ii) sequential extraction of heavy metals from soil fractions separated in the first step, by using combined SPE-ABS procedure. For the preparation of combined extraction systems was used polyethylene glycol (with different molecular mass: 2000, 4000 and 8000). As phase-forming inorganic salts and as selective extracting agents we have used different usual inorganic reagents. The type and concentration of phase-forming salts have been selected in function of, both nature of extracted heavy metals and chemical-mineralogical characteristics of soil samples. The experimental parameters investigated in this study are: molecular mass of polyethylene glycol and the concentration of polymeric solutions, nature and concentration of phase-forming salts, nature and concentration of extracting agents, pH in extraction system phase, type of extracted heavy metals, type of speciation forms of heavy metals and their concentrations. All these factors can influence significantly the efficiency and the selectivity of separation process. The experimental results have indicate that the combined SPE-ABS extraction systems have better separation efficiency, in comparison with traditional SPE systems and ca realized a accurate discrimination between speciation forms of heavy metals from soils. Under these conditions, the estimation of inter-phases distribution and biodisponibility of heavy metals has a high precision. On the other hand, when the combined SPE-ABS systems are used, the concomitant extraction of the elements from the same geochemical association with studied heavy metals (inevitable phenomena in case of separation by SPE procedures) is significant diminished. This increases the separation selectivity and facilitated the more accurate determination of speciation forms concentration. By adequate selection of extraction conditions can be realized the selective separation of organic-mineral complexes, which will permit to perform detailed studies about the structure and chemical composition of these. Acknowledgments The authors would like to acknowledge the financial support from Romanian Ministry of Education and Research (Project PNCDI 2-D5 no. 51045/07 and project PNCDI 2 - D5 no. 52-141 / 2008).

Seasonal reversal of temperature-moisture response of net carbon exchange of biocrusted soils in a cool desert ecosystem.

NASA Astrophysics Data System (ADS)

Tucker, C.; Reed, S.; Howell, A.

2017-12-01

Carbon cycling associated with biological soil crusts, which occur in interspaces between vascular plants in drylands globally, may be an important part of the coupled climate-carbon cycle of the Earth system. A major challenge to understanding CO2 fluxes in these systems is that much of the biotic and biogeochemical activity occurs in the upper few mm of the soil surface layer (i.e., the `mantle of fertility'), which exhibits highly dynamic and difficult to measure temperature and moisture fluctuations. Here, we report data collected in a cool desert ecosystem over one year using a multi-sensor approach to simultaneously measuring temperature and moisture of the biocrust surface layer (0-2 mm), and the deeper soil profile (5-20 cm), concurrent with automated measurement of surface soil CO2 effluxes. Our results illuminate robust relationships between microclimate and field CO2 pulses that have previously been difficult to detect and explain. The temperature of the biocrust surface layer was highly variable, ranging from minimum of -9 °C in winter to maximum of 77 °C in summer with a maximum diurnal range of 61 °C. Temperature cycles were muted deeper in the soil profile. During summer, biocrust and soils were usually hot and dry and CO2 fluxes were tightly coupled to pulse wetting events experienced at the biocrust surface, which consistently resulted in net CO2 efflux (i.e., respiration). In contrast, during the winter, biocrust and soils were usually cold and moist, and there was sustained net CO2 uptake via photosynthesis by biocrust organisms, although during cold dry periods CO2 fluxes were minimal. During the milder spring and fall seasons, short wetting events drove CO2 loss, while sustained wetting events resulted in net CO2 uptake. Thus, the upper and lower bounds of net CO2 exchange at a point in time were functions of the seasonal temperature regime, while the actual flux within those bounds was determined by the magnitude and duration of biocrust and soil wetting events. These patterns reflect both the low temperature sensitivity and slow initiation in response to wetting of photosynthesis compared to respiration by biocrust organisms. Our study highlights the importance of cool and cold periods for C uptake in biocrusted soils of the Colorado Plateau.

Variable Charge Soils: Mineralogy and Chemistry

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

Qafoku, Nik; Van Ranst, Eric; Noble, Andrew

2003-11-01

Soils rich in particles with amphoteric surface properties in the Oxisols, Ultisols, Alfisols, Spodosols and Andisols orders (1) are considered variable charge soils (2). The term “variable charge” is used to describe organic and inorganic soil constituents with reactive surface groups whose charge varies with pH, ionic concentration and composition of the soil solution. Such groups are the surface carboxyl, phenolic and amino functional groups of organic materials in soils, and surface hydroxyl groups of Fe and Al oxides, allophane and imogolite. The hydroxyl surface groups are also present on edges of some phyllosilicate minerals such as kaolinite, mica, andmore » hydroxyl-interlayered vermiculite. The variable charge is developed on the surface groups as a result of adsorption or desorption of ions that are constituents of the solid phase, i.e., H+, and the adsorption or desorption of solid-unlike ions that are not constituents of the solid. Highly weathered soils usually undergo isoeletric weathering and reach a “zero net charge” stage during their development. They have a slightly acidic to acidic soil solution pH, which is close to either point of zero net charge (PZNC) (3) or point of zero salt effect (PZSE) (3). They are characterized by high abundances of minerals with a point of zero net proton charge (PZNPC) (3) at neutral and slightly basic pHs; the most important being Fe and Al oxides and allophane. Under acidic conditions, the surfaces of these minerals are net positively charged. In contrast, the surfaces of permanent charge phyllosilicates are negatively charged regardless of ambient conditions. Variable charge soils therefore, are heterogeneous charge systems. The coexistence and interactions of oppositely charged surfaces or particles confers a different pattern of physical and chemical behavior on the soil, relatively to a homogeneously charged system of temperate regions. In some variable charge soils (Oxisols and some Ultisols developed on ferromagnesian-rich parent materials) the surfaces of phyllosilicates are coated to a lesser or greater extent by amorphous or crystalline, oppositely charged nanoparticles of Fe and Al oxides. These coatings exhibit a high reactive surface area and help cementing larger particles with one another. As a result of these electrostatic interactions, stable microaggregates that are difficult to disperse are formed in variable charge soils. Most of highly weathered soils have reached the “advanced stage” of Jackson-Sherman weathering sequence that is characterized by the removal of Na, K, Ca, Mg, and Fe(II), the presence of Fe and Al polymers, and very dilute soil solutions with an ionic strength (IS) of less than 1 mmol L-1. The inter-penetration or overlapping of the diffuse double layers on oppositely charged surfaces may occur in these dilute systems. These diffuse layer interactions may affect the magnitude of the effective charge, i.e., the counter-ion charge (4). In addition, salt adsorption, which is defined as the simultaneous adsorption in equivalent amounts of the cation and anion of an electrolyte with no net release of other ions into the soil solution, appears to be a common phenomenon in these soils. They act as cation- and anion-exchangers and as salt-sorbers. The magnitude of salt adsorption depends strongly on initial IS in the soil solution and the presence in appreciable amounts of oppositely charged surfaces. Among the authors that have made illustrious contributions towards a better understanding of these fascinating soil systems are S. Matson, R.K. Schofield, van Olphen, M.E. Sumner, G.W. Thomas, G.P. Gillman, G. Uehara, B.K.G. Theng, K. Wada, N.J. Barrow, J.W. Bowden, R.J. Hunter and G. Sposito. This entry is mainly based on publications by these authors.« less

The sensitivity of numerically simulated climates to land-surface boundary conditions

NASA Technical Reports Server (NTRS)

Mintz, Y.

1982-01-01

Eleven sensitivity experiments that were made with general circulation models to see how land-surface boundary conditions can influence the rainfall, temperature, and motion fields of the atmosphere are discussed. In one group of experiments, different soil moistures or albedos are prescribed as time-invariant boundary conditions. In a second group, different soil moistures or different albedos are initially prescribed, and the soil moisture (but not the albedo) is allowed to change with time according to the governing equations for soil moisture. In a third group, the results of constant versus time-dependent soil moistures are compared.

Temporal and spatial variability of soil biological activity at European scale

NASA Astrophysics Data System (ADS)

Mallast, Janine; Rühlmann, Jörg

2015-04-01

The CATCH-C project aims to identify and improve the farm-compatibility of Soil Management Practices including to promote productivity, climate change mitigation and soil quality. The focus of this work concentrates on turnover conditions for soil organic matter (SOM). SOM is fundamental for the maintenance of quality and functions of soils while SOM storage is attributed a great importance in terms of climate change mitigation. The turnover conditions depend on soil biological activity characterized by climate and soil properties. Soil biological activity was investigated using two model concepts: a) Re_clim parameter within the ICBM (Introductory Carbon Balance Model) (Andrén & Kätterer 1997) states a climatic factor summarizing soil water storage and soil temperature and its influence on soil biological activity. b) BAT (biological active time) approach derived from model CANDY (CArbon and Nitrogen Dynamic) (Franko & Oelschlägel 1995) expresses the variation of soil moisture, soil temperature and soil aeration as a time scale and an indicator of biological activity for soil organic matter (SOM) turnover. During an earlier stage both model concepts, Re_clim and BAT, were applied based on a monthly data to assess spatial variability of turnover conditions across Europe. This hampers the investigation of temporal variability (e.g. intra-annual). The improved stage integrates daily data of more than 350 weather stations across Europe presented by Klein Tank et al. (2002). All time series data (temperature, precipitation and potential evapotranspiration and soil texture derived from the European Soil Database (JRC 2006)), are used to calculate soil biological activity in the arable layer. The resulting BAT and Re_clim values were spatio-temporal investigated. While "temporal" refers to a long-term trend analysis, "spatial" includes the investigation of soil biological activity variability per environmental zone (ENZ, Metzger et al. 2005 representing similar conditions for precipitation, temperature and relief) to identify ranges and hence turnover conditions for each ENZ. We will discuss the analyzed results of both concepts to assess SOM turnover conditions across Europe for historical weather data and for Spain focusing on climate scenarios. Both concepts help to separate different turnover activities and to indicate organic matter input in order to maintain the given SOM. The assessment could provide recommendations for adaptations of soil management practices. CATCH-C is funded within the 7th Framework Programme for Research, Technological Development and Demonstration, Theme 2 - Biotechnologies, Agriculture & Food (Grant Agreement N° 289782).

Estimating Soil Cation Exchange Capacity from Soil Physical and Chemical Properties

NASA Astrophysics Data System (ADS)

Bateni, S. M.; Emamgholizadeh, S.; Shahsavani, D.

2014-12-01

The soil Cation Exchange Capacity (CEC) is an important soil characteristic that has many applications in soil science and environmental studies. For example, CEC influences soil fertility by controlling the exchange of ions in the soil. Measurement of CEC is costly and difficult. Consequently, several studies attempted to obtain CEC from readily measurable soil physical and chemical properties such as soil pH, organic matter, soil texture, bulk density, and particle size distribution. These studies have often used multiple regression or artificial neural network models. Regression-based models cannot capture the intricate relationship between CEC and soil physical and chemical attributes and provide inaccurate CEC estimates. Although neural network models perform better than regression methods, they act like a black-box and cannot generate an explicit expression for retrieval of CEC from soil properties. In a departure with regression and neural network models, this study uses Genetic Expression Programming (GEP) and Multivariate Adaptive Regression Splines (MARS) to estimate CEC from easily measurable soil variables such as clay, pH, and OM. CEC estimates from GEP and MARS are compared with measurements at two field sites in Iran. Results show that GEP and MARS can estimate CEC accurately. Also, the MARS model performs slightly better than GEP. Finally, a sensitivity test indicates that organic matter and pH have respectively the least and the most significant impact on CEC.

Estimation of Rainfall Erosivity via 1-Minute to Hourly Rainfall Data from Taipei, Taiwan

NASA Astrophysics Data System (ADS)

Huang, Ting-Yin; Yang, Ssu-Yao; Jan, Chyan-Deng

2017-04-01

Soil erosion is a natural process on hillslopes that threats people's life and properties, having a considerable environmental and economic implications for soil degradation, agricultural activity and water quality. The rainfall erosivity factor (R-factor) in the Universal Soil Loss Equation (USLE), composed of total kinetic energy (E) and the maximum 30-min rainfall intensity (I30), is widely used as an indicator to measure the potential risks of soil loss caused by rainfall at a regional scale. This R factor can represent the detachment and entrainment involved in climate conditions on hillslopes, but lack of 30-min rainfall intensity data usually lead to apply this factor more difficult in many regions. In recent years, fixed-interval, hourly rainfall data is readily available and widely used due to the development of automatic weather stations. Here we assess the estimations of R, E, and I30 based on 1-, 5-, 10-, 15-, 30-, 60-minute rainfall data, and hourly rainfall data obtained from Taipei weather station during 2004 to 2010. Results show that there is a strong correlation among R-factors estimated from different interval rainfall data. Moreover, the shorter time-interval rainfall data (e.g., 1-min) yields larger value of R-factor. The conversion factors of rainfall erosivity (ratio of values estimated from the resolution lower than 30-min rainfall data to those estimated from 60-min and hourly rainfall data, respectively) range from 1.85 to 1.40 (resp. from 1.89 to 1.02) for 60-min (resp. hourly) rainfall data as the time resolution increasing from 30-min to 1-min. This paper provides useful information on estimating R-factor when hourly rainfall data is only available.

Characterization of Trapped Lignin-Degrading Microbes in Tropical Forest Soil

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

DeAngelis, Kristen M.; Allgaier, Martin; Chavarria, Yaucin

2011-04-29

Lignin is often the most difficult portion of plant biomass to degrade, with fungi generally thought to dominate during late stage decomposition. Lignin in feedstock plant material represents a barrier to more efficient plant biomass conversion and can also hinder enzymatic access to cellulose, which is critical for biofuels production. Tropical rain forest soils in Puerto Rico are characterized by frequent anoxic conditions and fluctuating redox, suggesting the presence of lignin-degrading organisms and mechanisms that are different from known fungal decomposers and oxygen-dependent enzyme activities. We explored microbial lignin-degraders by burying bio-traps containing lignin-amended and unamended biosep beads in themore » soil for 1, 4, 13 and 30 weeks. At each time point, phenol oxidase and peroxidase enzyme activity was found to be elevated in the lignin-amended versus the unamended beads, while cellulolytic enzyme activities were significantly depressed in lignin-amended beads. Quantitative PCR of bacterial communities showed more bacterial colonization in the lignin-amended compared to the unamended beads after one and four weeks, suggesting that the lignin supported increased bacterial abundance. The microbial community was analyzed by small subunit 16S ribosomal RNA genes using microarray (PhyloChip) and by high-throughput amplicon pyrosequencing based on universal primers targeting bacterial, archaeal, and eukaryotic communities. Community trends were significantly affected by time and the presence of lignin on the beads. Lignin-amended beads have higher relative abundances of representatives from the phyla Actinobacteria, Firmicutes, Acidobacteria and Proteobacteria compared to unamended beads. This study suggests that in low and fluctuating redox soils, bacteria could play a role in anaerobic lignin decomposition.« less

Characterization of trapped lignin-degrading microbes in tropical forest soil

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

DeAngelis, K.M.; Allgaier, M.; Chavarria, Y.

2011-03-01

Lignin is often the most difficult portion of plant biomass to degrade, with fungi generally thought to dominate during late stage decomposition. Lignin in feedstock plant material represents a barrier to more efficient plant biomass conversion and can also hinder enzymatic access to cellulose, which is critical for biofuels production. Tropical rain forest soils in Puerto Rico are characterized by frequent anoxic conditions and fluctuating redox, suggesting the presence of lignin-degrading organisms and mechanisms that are different from known fungal decomposers and oxygen-dependent enzyme activities. We explored microbial lignin-degraders by burying bio-traps containing lignin-amended and unamended biosep beads in themore » soil for 1, 4, 13 and 30 weeks. At each time point, phenol oxidase and peroxidase enzyme activity was found to be elevated in the lignin-amended versus the unamended beads, while cellulolytic enzyme activities were significantly depressed in lignin-amended beads. Quantitative PCR of bacterial communities showed more bacterial colonization in the lignin-amended compared to the unamended beads after one and four weeks, suggesting that the lignin supported increased bacterial abundance. The microbial community was analyzed by small subunit 16S ribosomal RNA genes using microarray (PhyloChip) and by high-throughput amplicon pyrosequencing based on universal primers targeting bacterial, archaeal, and eukaryotic communities. Community trends were significantly affected by time and the presence of lignin on the beads. Lignin-amended beads have higher relative abundances of representatives from the phyla Actinobacteria, Firmicutes, Acidobacteria and Proteobacteria compared to unamended beads. This study suggests that in low and fluctuating redox soils, bacteria could play a role in anaerobic lignin decomposition.« less

Characterization of Trapped Lignin-Degrading Microbes in Tropical Forest Soil

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

DeAngelis, Kristen; Allgaier, Martin; Chavarria, Yaucin

2011-07-14

Lignin is often the most difficult portion of plant biomass to degrade, with fungi generally thought to dominate during late stage decomposition. Lignin in feedstock plant material represents a barrier to more efficient plant biomass conversion and can also hinder enzymatic access to cellulose, which is critical for biofuels production. Tropical rain forest soils in Puerto Rico are characterized by frequent anoxic conditions and fluctuating redox, suggesting the presence of lignin-degrading organisms and mechanisms that are different from known fungal decomposers and oxygen-dependent enzyme activities. We explored microbial lignin-degraders by burying bio-traps containing lignin-amended and unamended biosep beads in themore » soil for 1, 4, 13 and 30 weeks. At each time point, phenol oxidase and peroxidase enzyme activity was found to be elevated in the lignin-amended versus the unamended beads, while cellulolytic enzyme activities were significantly depressed in lignin-amended beads. Quantitative PCR of bacterial communities showed more bacterial colonization in the lignin-amended compared to the unamended beads after one and four weeks, suggesting that the lignin supported increased bacterial abundance. The microbial community was analyzed by small subunit 16S ribosomal RNA genes using microarray (PhyloChip) and by high-throughput amplicon pyrosequencing based on universal primers targeting bacterial, archaeal, and eukaryotic communities. Community trends were significantly affected by time and the presence of lignin on the beads. Lignin-amended beads have higher relative abundances of representatives from the phyla Actinobacteria, Firmicutes, Acidobacteria and Proteobacteria compared to unamended beads. This study suggests that in low and fluctuating redox soils, bacteria could play a role in anaerobic lignin decomposition.« less

Method for the Preparation of Hazard Map in Urban Area Using Soil Depth and Groundwater Level

NASA Astrophysics Data System (ADS)

Kim, Sung-Wook; Choi, Eun-Kyeong; Cho, Jin Woo; Lee, Ju-Hyoung

2017-04-01

The hazard maps for predicting collapse on natural slopes consists of a combination of topographic, hydrological, and geological factors. Topographic factors are extracted from DEM, including aspect, slope, curvature, and topographic index. Hydrological factors, such as distance to drainage, drainage density, stream-power index, and wetness index are most important factors for slope instability. However, most of the urban areas are located on the plains and it is difficult to apply the hazard map using the topography and hydrological factors. In order to evaluate the risk of collapse of flat and low slope areas, soil depth and groundwater level data were collected and used as a factor for interpretation. In addition, the reliability of the hazard map was compared with the disaster history of the study area (Gangnam-gu and Yeouido district). In the disaster map of the disaster prevention agency, the urban area was mostly classified as the stable area and did not reflect the collapse history. Soil depth, drainage conditions and groundwater level obtained from boreholes were added as input data of hazard map, and disaster vulnerability increased at the location where the actual collapse points. In the study area where damage occurred, the moderate and low grades of the vulnerability of previous hazard map were 12% and 88%, respectively. While, the improved map showed 2% high grade, moderate grade 29%, low grade 66% and very low grade 2%. These results were similar to actual damage. Keywords: hazard map, urban area, soil depth, ground water level Acknowledgement This research was supported by a Grant from a Strategic Research Project (Horizontal Drilling and Stabilization Technologies for Urban Search and Rescue (US&R) Operation) funded by the Korea Institute of Civil Engineering and Building Technology.

Harnessing long-term flux records to better understand ecosystem response to drought

NASA Astrophysics Data System (ADS)

Novick, K. A.; Ficklin, D. L.; Stoy, P. C.; Williams, C. A.; Bohrer, G.; Oishi, A. C.; Papuga, S. A.; Blanken, P.; Noormets, A.; Scott, R. L.; Wang, L.; Roman, D. T.; Yi, K.; Sulman, B. N.; Phillips, R.

2016-12-01

While ongoing climate change affects a number of meteorological drivers relevant to plant functioning, the predicted increase in the frequency and severity of droughts may ultimately have the biggest impact on ecosystem carbon cycling. Because it is difficult to experimentally manipulate all of the meteorological drivers that change during drought (including precipitation, light, temperature, and humidity), our understanding of the mechanisms by which plants respond to drought is generally limited to an understanding of how plants respond to variable soil moisture. As flux tower records grow in length and number, they permit us to harness natural spatial and temporal variability in hydrologic condition to better understand how ecosystems respond to the full suite of meteorological drivers that change during drought stress. Here, a series of case studies are presented that illustrate how long term flux data can be used to disentangle limitations to ecosystem functioning imposed by declining soil moisture as compared to rising atmospheric demand for water during drought. At the site-level, we pair observations from the Morgan-Monroe State Forest Ameriflux tower (active since 1999) with eco-physiological datasets collected during the severe 2012 Midwestern drought. We show that vapor pressure deficit (VPD) limits ecosystem carbon uptake and transpiration as much as soil moisture, but that individual species vary in their sensitivity to these drivers. We then present results from two cross-site Ameriflux syntheses that quantify how VPD as compared to soil moisture limitations to carbon and water cycling vary across broad climate gradients spanning semi-arid to mesic biomes. Informed by these results, we end by highlighting ways that flux network data may be leveraged together with other eco-physiological networks and databases to further expand our understanding of the mechanisms determining ecosystem response to drought.

Determination of Matric Suction and Saturation Degree for Unsaturated Soils, Comparative Study - Numerical Method versus Analytical Method

NASA Astrophysics Data System (ADS)

Chiorean, Vasile-Florin

2017-10-01

Matric suction is a soil parameter which influences the behaviour of unsaturated soils in both terms of shear strength and permeability. It is a necessary aspect to know the variation of matric suction in unsaturated soil zone for solving geotechnical issues like unsaturated soil slopes stability or bearing capacity for unsaturated foundation ground. Mathematical expression of the dependency between soil moisture content and it’s matric suction (soil water characteristic curve) has a powerful character of nonlinearity. This paper presents two methods to determine the variation of matric suction along the depth included between groundwater level and soil level. First method is an analytical approach to emphasize one direction steady state unsaturated infiltration phenomenon that occurs between the groundwater level and the soil level. There were simulated three different situations in terms of border conditions: precipitations (inflow conditions on ground surface), evaporation (outflow conditions on ground surface), and perfect equilibrium (no flow on ground surface). Numerical method is finite element method used for steady state, two-dimensional, unsaturated infiltration calculus. Regarding boundary conditions there were simulated identical situations as in analytical approach. For both methods, was adopted the equation proposed by van Genuchten-Mualen (1980) for mathematical expression of soil water characteristic curve. Also for the unsaturated soil permeability prediction model was adopted the equation proposed by van Genuchten-Mualen. The fitting parameters of these models were adopted according to RETC 6.02 software in function of soil type. The analyses were performed in both methods for three major soil types: clay, silt and sand. For each soil type were concluded analyses for three situations in terms of border conditions applied on soil surface: inflow, outflow, and no flow. The obtained results are presented in order to highlight the differences/similarities between the methods and the advantages / disadvantages of each one.

Selenium inhibits sulfate-mediated methylmercury production in rice paddy soil.

PubMed

Wang, Yong-Jie; Dang, Fei; Zhao, Jia-Ting; Zhong, Huan

2016-06-01

There is increasing interest in understanding factors controlling methylmercury (MeHg) production in mercury-contaminated rice paddy soil. Sulfate has been reported to affect MeHg biogeochemistry under anoxic conditions, and recent studies revealed that selenium (Se) could evidently reduce MeHg production in paddy soil. However, the controls of sulfate and Se on net MeHg production in paddy soil under fluctuating redox conditions remain largely unknown. Microcosm experiments were conducted to explore the effects of sulfate and Se on net MeHg production in rice paddy soil. Soil was added with 0-960 mg/kg sulfate, in the presence or absence of 3.0 mg/kg selenium (selenite or selenate), and incubated under anoxic (40 days) or suboxic conditions (5 days), simulating fluctuating redox conditions in rice paddy field. Sulfate addition moderately affected soil MeHg concentrations under anoxic conditions, while reoxidation resulted in evidently higher (18-40%) MeHg levels in sulfate amended soils than the control. The observed changes in net MeHg production were related to dynamics of sulfate and iron. However, Se could inhibit sulfate-mediated MeHg production in the soils: Se addition largely reduced net MeHg production in the soils (23-86%, compared to the control), despite of sulfate addition. Similarly, results of the pot experiments (i.e., rice cultivation in amended soils) indicated that soil MeHg levels were rather comparable in Se-amended soils during rice growth period, irrespective of added sulfate doses. The more important role of Se than sulfate in controlling MeHg production was explained by the formation of HgSe nanoparticles irrespective of the presence of sulfate, confirmed by TEM-EDX and XANES analysis. Our findings regarding the effects of sulfate and Se on net MeHg production in rice paddy soil together with the mechanistic explanation of the processes advance our understanding of MeHg dynamics and risk in soil-rice systems. Copyright © 2016 Elsevier Ltd. All rights reserved.

Examining the effect of altered redox conditions on deep soil organic matter stability

NASA Astrophysics Data System (ADS)

Gabriel, C.; Kellman, L. M.; Ziegler, S. E.

2013-12-01

Since subsoil horizons contribute significantly to terrestrial carbon (C) budgets, understanding the influence of disturbances such as forest harvesting on subsoil C stability is critical. Clearcut harvesting leads to changes in the soil physico-chemical environment, including altering redox conditions arising from changes in soil hydrology that increase soil saturation, soil temperature, and pH. These physico-chemical changes have the potential to alter the adsorption of soil organic matter (SOM) to minerals, particularly at depth where SOM is primarily associated with mineral phases. The objective of this study was to determine the effect of differing redox states (aerobic vs. anaerobic) and temperature upon SOM stability of forested soils representative of the Acadian Forest Region of Eastern North America. Composite soil samples through depth (0-10, 10-20, 20-35, and 35-50 cm) from a mature red spruce forest (110 years) were incubated under optimum (aerobic) or saturated (anaerobic) conditions for 1 or 4 months at two temperatures (5 and 15 C). Following incubation, soil leachate was analyzed for dissolved organic carbon (DOC), and UV-vis absorbance in order to determine soil C losses and its optical character. Specific UV-vis absorbance SUVA (254 nm) and spectral slope ratios were calculated in order to assess the composition of chromophoric dissolved organic matter (CDOM). Preliminary results from the 1 month incubation indicate that under anaerobic conditions, all depths released DOC with a higher SUVA than under aerobic conditions, with the largest change observed in the 0-10 cm depth increment. Soil incubated at 5 C produced leachate with significantly less DOC and with a lower absorbance compared to 15 C under both redox conditions. These results suggest that both temperature and redox state are important in determining the aromaticity of DOC released from soils. Spectral slope ratios revealed that a greater proportion of CDOM of lower molecular weight (MW) compounds were released from deep mineral podzolic soils when saturated (high SUVA, low spectral slope), while higher MW CDOM were released from shallow soil strata (low SUVA, high spectral slope). This is consistent with research that indicates plant-derived SOM and microbial products each dominate in shallow and deep mineral soils, respectively. These preliminary results suggest that alterations to the redox state of a forested podzolic soil may have the potential to alter the mobilization of SOM, its composition and associated soil carbon stores.

Contemporary and long-term erosion in the Kruger National Park, Lowveld Savanna, South Africa. First results.

NASA Astrophysics Data System (ADS)

Baade, Jussi; Rheinwarth, Bastian; Glotzbach, Christoph

2017-04-01

Human-induced soil erosion as a consequence of the transformation of landscapes to pasture or arable land is a function of natural conditions (relief and soil properties), natural drivers (climate) as well as land use and management. It is common understanding that humans have accelerated erosion of landscapes by modifying land surface characteristics, like vegetation cover and soil properties, among others. But the magnitude of the acceleration is not yet well established. Partly, the uncertainty about the magnitude of the problem is due to the fact that baseline values, i.e., data on rates of natural erosion from uncultivated land under current climate conditions, are difficult to find. Against this background, we conducted an assessment of contemporary and long-term erosion in the Kruger National Park (KNP), South Africa. The KNP has been set aside for the recovery of wildlife in the early 20th century and was spared from agricultural practices even before that. Concerning soil properties and vegetation cover the KNP can thus be considered to represent a rather pristine savanna environment. In order to secure water provision to wildlife a number of reservoirs was established in the 1930s to 1970s with catchment areas entirely within the KNP boundaries. The size of the catchments varies from 4 to 100 km2. Volumetric mapping and dry bulk density measurements of reservoir deposits provided average minimum sediment yield rates for observation periods of 30 to 80 years. Hydrological modelling was used to assess the trap efficiency of the reservoirs and to estimate the most likely sediment yield rates. At the same time this exercise provided evidence for the stochastic nature of runoff and erosion events in this semi-arid environment and the need to evaluate contemporary erosion based on long observation periods. Measuring cosmogenic 10Be in quartz sand samples collected at the inlet of the reservoirs provided the corresponding average long-term erosion rates for periods of a few 100,000 years. This presentation provides first results based on more than 10 investigated reservoirs and compares contemporary and long-term erosion rates.

7 CFR 12.32 - Converted wetland identification criteria.

Code of Federal Regulations, 2012 CFR

2012-01-01

... hydric soils have been used for production of an agricultural commodity and the effect of the drainage or... containing the same hydric soils in a natural condition to determine if the hydric soils can or cannot be used to produce an agricultural commodity under natural conditions. If the soil on the comparison site...

7 CFR 12.32 - Converted wetland identification criteria.

Code of Federal Regulations, 2011 CFR

2011-01-01

... hydric soils have been used for production of an agricultural commodity and the effect of the drainage or... containing the same hydric soils in a natural condition to determine if the hydric soils can or cannot be used to produce an agricultural commodity under natural conditions. If the soil on the comparison site...

7 CFR 12.32 - Converted wetland identification criteria.

Code of Federal Regulations, 2010 CFR

2010-01-01

... hydric soils have been used for production of an agricultural commodity and the effect of the drainage or... containing the same hydric soils in a natural condition to determine if the hydric soils can or cannot be used to produce an agricultural commodity under natural conditions. If the soil on the comparison site...

7 CFR 12.32 - Converted wetland identification criteria.

Code of Federal Regulations, 2013 CFR

2013-01-01

... hydric soils have been used for production of an agricultural commodity and the effect of the drainage or... containing the same hydric soils in a natural condition to determine if the hydric soils can or cannot be used to produce an agricultural commodity under natural conditions. If the soil on the comparison site...

7 CFR 12.32 - Converted wetland identification criteria.

Code of Federal Regulations, 2014 CFR

2014-01-01

... hydric soils have been used for production of an agricultural commodity and the effect of the drainage or... containing the same hydric soils in a natural condition to determine if the hydric soils can or cannot be used to produce an agricultural commodity under natural conditions. If the soil on the comparison site...

Changes of microbial activities and soil aggregation in rhizosphere soil of lettuce plants by drought and the possible influence of inoculation with AM fungi and/or PGPR

NASA Astrophysics Data System (ADS)

Kohler, J.; Caravaca, F.; Roldán, A.

2009-04-01

The effect of different arbuscular mycorrhizal (AM) fungi, Glomus intraradices (Schenk & Smith) or Glomus mosseae (Nicol & Gerd.) Gerd. & Trappe, and plant growth-promoting rhizobacteria (PGPR) (Pseudomonas mendocina Palleroni), alone or in combination, on structural stability and microbial activity in the rhizosphere soil of Lactuca sativa L. was assessed under well-watered conditions and two levels of drought. Desiccation caused an increase in aggregate stability and water-soluble and total carbohydrates but there were no significant differences among treated soils and the control soil. The glomalin-related soil protein (GRSP) levels in both the <2 mm and 0.2-4 mm soil fractions increased with medium water stress, whereas under severe water stress they did not differ with respect to those of well-watered soils. The values of GRSP in soils inoculated with PGPR and AM fungi were higher than in the control or fertilised soil under well-watered and severe-drought conditions, while under medium-drought conditions all soils showed similar GRSP values. Soils inoculated with AM fungi and PGPR generally presented higher dehydrogenase and phosphatase activities than the control soil, independent of the water regime.

[Environmental safety assessment on the new super absorbent polymers applied into a soil-Chinese cabbage system].

PubMed

Li, Xi; He, Ji-Zheng; Zheng, Yuan-Ming; Zheng, Ming-Lan

2014-02-01

Super absorbent polymers (SAPs), a new water retention material, have a potential for application in water-saving agricultural production. In this study, we investigated the effects of SAPs, synthesized from natural plant extracts, on Chinese cabbage fresh weight, soil water content, soil water stable aggregates, soil microbial biomass (carbon) and soil microbial respiration under three water conditions (excessive, normal and deficient) and two SAPs application strategies (bulk treatment and spraying treatment). The results showed that the SAPs significantly promoted the soil water content, water-stable aggregates (> 0.25 mm) and the soil microbial activities, especially under the water deficient conditions. Meanwhile, SAP application strategy was of great significance to the effects on Chinese cabbage and soil properties. Compared with the control treatment under normal water condition, spraying treatment of Jaguar C (S-JC) could reduce irrigation water amount by about 25% without reducing the crop production. Furthermore, compared with the control treatment under the same water condition with S-JC (deficient), it could increase Chinese cabbage production by 287%. Thus, SAPs is an environmental friendly water-saving technique in agricultural production.

Validation of a station-prototype designed to integrate temporally soil N2O fluxes: IPNOA Station prototype.

NASA Astrophysics Data System (ADS)

Laville, Patricia; Volpi, Iride; Bosco, Simona; Virgili, Giorgio; Neri, Simone; Continanza, Davide; Bonari, Enrico

2016-04-01

Nitrous oxide (N2O) flux measurements from agricultural soil surface still accounts for the scientific community as major challenge. The evaluations of integrated soil N2O fluxes are difficult because these emissions are lower than for the other greenhouse gases sources (CO2, CH4). They are also sporadic, because highly dependent on few environmental conditions acting as limiting factors. Within a LIFE project (IPNOA: LIFE11 ENV/IT/00032) a station prototype was developed to integrate annually N2O and CO2 emissions using automatically chamber technique. Main challenge was to develop a device enough durable to be able of measuring in continuous way CO2 and N2O fluxes with sufficient sensitivity to allow make reliable assessments of soil GHG measurements with minimal technical field interventions. The IPNOA station prototype was developed by West System SRL and was set up during 2 years (2014 -2015) in an experimental maize field in Tuscan. The prototype involved six automatic chambers; the complete measurement cycle was of 2 hours. Each chamber was closing during 20 min and biogas accumulations were monitoring in line with IR spectrometers. Auxiliary's measurements including soil temperatures and water contents as weather data were also monitoring. All data were managed remotely with the same acquisition software installed in the prototype control unit. The operation of the prototype during the two cropping years allowed testing its major features: its ability to evaluate the temporal variation of N2O soil fluxes during a long period with weather conditions and agricultural managements and to prove the interest to have continuous measurements of fluxes. The temporal distribution of N2O fluxes indicated that emissions can be very large and discontinuous over short periods less ten days and that during about 70% of the time N2O fluxes were around detection limit of the instrumentation, evaluated to 2 ng N ha-1 day-1. N2O emission factor assessments were 1.9% in 2014 and 1.7 % in 2015, in the range of IPCC ones. The instrumentation was working almost permanently during these two years. The proximity sensors fitted on the chambers allowed showing that the chambers were functioning normally for about 90% of the time. A cross-comparison carried out in September 2015 with the "mobile IPNOA prototype"; a high-sensibility transportable instrument (previously validated), allowed showing a good agreement between the 2 instrumentations.

Soil mixing of stratified contaminated sands.

PubMed

Al-Tabba, A; Ayotamuno, M J; Martin, R J

2000-02-01

Validation of soil mixing for the treatment of contaminated ground is needed in a wide range of site conditions to widen the application of the technology and to understand the mechanisms involved. Since very limited work has been carried out in heterogeneous ground conditions, this paper investigates the effectiveness of soil mixing in stratified sands using laboratory-scale augers. This enabled a low cost investigation of factors such as grout type and form, auger design, installation procedure, mixing mode, curing period, thickness of soil layers and natural moisture content on the unconfined compressive strength, leachability and leachate pH of the soil-grout mixes. The results showed that the auger design plays a very important part in the mixing process in heterogeneous sands. The variability of the properties measured in the stratified soils and the measurable variations caused by the various factors considered, highlighted the importance of duplicating appropriate in situ conditions, the usefulness of laboratory-scale modelling of in situ conditions and the importance of modelling soil and contaminant heterogeneities at the treatability study stage.

Enhancing Bioremediation of Oil-contaminated Soils by Controlling Nutrient Transport using Dual Characteristics of Soil Pore Structure

NASA Astrophysics Data System (ADS)

Mori, Y.; Suetsugu, A.; Matsumoto, Y.; Fujihara, A.; Suyama, K.; Miyamoto, T.

2012-12-01

Soil structure is heterogeneous with cracks or macropores allowing bypass flow, which may lead to applied chemicals avoiding interaction with soil particles or the contaminated area. We investigated the bioremediation efficiency of oil-contaminated soils by applying suction at the bottom of soil columns during bioremediation. Unsaturated flow conditions were investigated so as to avoid bypass flow and achieve sufficient dispersion of chemicals in the soil column. The boundary conditions at the bottom of the soil columns were 0 kPa and -3 kPa, and were applied to a volcanic ash soil with and without macropores. Unsaturated flow was achieved with -3 kPa and an injection rate of 1/10 of the saturated hydraulic conductivity. The resultant biological activities of the effluent increased dramatically in the unsaturated flow with macropores condition. Unsaturated conditions prevented bypass flow and allowed dispersion of the injected nutrients. Unsaturated flow achieved 60-80% of saturation, which enhanced biological activity in the soil column. Remediation results were better for unsaturated conditions because of higher biological activity. Moreover, unsaturated flow with macropores achieved uniform remediation efficiency from upper through lower positions in the column. Finally, taking the applied solution volume into consideration, unsaturated flow with -3 kPa achieved 10 times higher efficiency when compared with conventional saturated flow application. These results suggest that effective use of nutrients or remediation chemicals is possible by avoiding bypass flow and enhancing biological activity using relatively simple and inexpensive techniques.

Long-term monitoring of stream bank stability under different vegetation cover

NASA Astrophysics Data System (ADS)

Krzeminska, Dominika; Skaalsveen, Kamilla; Kerkhof, Tjibbe

2017-04-01

Vegetated buffer zones are common environmental measures in many countries, including Norway. The presence of riparian vegetation on stream banks not only provides ecological benefits but also influence bank slope stability, through several complex interactions between riparian vegetation and hydro - mechanical processes. The hydrological processes associated with slope stability are complex and yet difficult to quantify, especially because their transient effects (e.g. changes throughout the vegetation life cycle). Additionally, there is very limited amount of field scale research focusing on investigation of coupled hydrological and mechanical influence of vegetation on stream bank behavior, accounting for both seasonal time scale and different vegetation type, and none dedicated to marine clay soils (typically soil for Norway). In order to fill this gap we established continues, long term hydrogeological monitoring o selected cross - section within stream bank, covered with different types of vegetation, typical for Norwegian agriculture areas (grass, shrubs, and trees). The monitoring involves methods such as spatial and temporal monitoring of soil moisture conditions, ground water level and fluctuation of water level in the stream. Herein we will present first 10 months of monitoring data: observed hydrological trends and differences between three cross - sections. Moreover, we will present first modelling exercises that aims to estimate stream banks stability with accounting on presence of different vegetation types using BSTEM and HYDRUS models. With this presentation, we would like to stimulate the discussion and get feedback that could help us to improve both, our experimental set up and analysis approach.

Preferential flow from pore to landscape scales

NASA Astrophysics Data System (ADS)

Koestel, J. K.; Jarvis, N.; Larsbo, M.

2017-12-01

In this presentation, we give a brief personal overview of some recent progress in quantifying preferential flow in the vadose zone, based on our own work and those of other researchers. One key challenge is to bridge the gap between the scales at which preferential flow occurs (i.e. pore to Darcy scales) and the scales of interest for management (i.e. fields, catchments, regions). We present results of recent studies that exemplify the potential of 3-D non-invasive imaging techniques to visualize and quantify flow processes at the pore scale. These studies should lead to a better understanding of how the topology of macropore networks control key state variables like matric potential and thus the strength of preferential flow under variable initial and boundary conditions. Extrapolation of this process knowledge to larger scales will remain difficult, since measurement technologies to quantify macropore networks at these larger scales are lacking. Recent work suggests that the application of key concepts from percolation theory could be useful in this context. Investigation of the larger Darcy-scale heterogeneities that generate preferential flow patterns at the soil profile, hillslope and field scales has been facilitated by hydro-geophysical measurement techniques that produce highly spatially and temporally resolved data. At larger regional and global scales, improved methods of data-mining and analyses of large datasets (machine learning) may help to parameterize models as well as lead to new insights into the relationships between soil susceptibility to preferential flow and site attributes (climate, land uses, soil types).

Fraction of the global water cycle observed by SMAP

NASA Astrophysics Data System (ADS)

Mccoll, K. A.; Entekhabi, D.; Alemohammad, S. H.; Akbar, R.; Konings, A. G.; Yueh, S. H.

2016-12-01

Sparse and uneven observations have made it difficult to quantify the global distribution and dynamics of surface soil moisture (SSM). Using a full year of global observations from NASA's Soil Moisture Active Passive (SMAP) mission, we show here that SSM - 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 very significant role in the water cycle, retaining a median 16% of precipitation falling on land after 3 days. Furthermore, the retained fraction of the SSM storage after 3 days is highest (lowest) over arid (wet) regions, and in regions where drainage to groundwater storage is lowest (highest). The retained fraction decreases monotonically with increasing mean SSM. Regions of low retained fraction broadly correspond spatially with regions where groundwater recharge and groundwater storage are both largest. These analyses are the first global estimates - derived from measurements rather than models - of both the mean magnitude and memory time scales of the SSM storage. Beyond the fundamental importance of characterizing the magnitude and response time scales of Earth's water storages, a key application of these results is in identifying regions with strong land-atmosphere coupling. Significant soil moisture memory is a necessary condition for land-atmosphere feedbacks. These results may therefore have particularly important implications for short-term weather forecasting of extreme precipitation events and floods.

ADVANCED MIXED OXIDATION AND INCLUSION TECHNOLOGY - PHASE I

EPA Science Inventory

Coal tar contaminants, such as polycyclic aromatic hydrocarbons (PAH) currently are difficult to treat in a timely and cost-efficient manner. The generally poor performance of conventional PAH treatment schemes, such as soil flushing or bioremediation, has led to research ...

HORIZONTAL LASAGNA^TM TO BIOREMEDIATE TCE

EPA Science Inventory

Removal of TCE from these tight clay soils has been technically difficult and expensive. However, the LASAGNA technique allows movement of the TCE into treatment zones for biodegradation or dechlorination in place, lessening the costs and exposure to TCE.

Electroosmosis wa...

Soil microbial diversity, site conditions, shelter forest land, saline water drip-irrigation, drift desert.

PubMed

Jin, Zhengzhong; Lei, Jiaqiang; Li, Shengyu; Xu, Xinwen

2013-10-01

Soil microbes in forest land are crucial to soil development in extreme areas. In this study, methods of conventional culture, PLFA and PCR-DGGE were utilized to analyze soil microbial quantity, fatty acids and microbial DNA segments of soils subjected to different site conditions in the Tarim Desert Highway forest land. The main results were as follows: the soil microbial amount, diversity indexes of fatty acid and DNA segment differed significantly among sites with different conditions (F < F0.05 ). Specifically, the values were higher in the middle and base of dunes than the top part of dunes and hardened flat sand, but all values for dunes were higher than for drift sand. Bacteria was dominant in the soil microbial community (>84%), followed by actinomycetes and then fungi (<0.05%). Vertical differences in the soil microbial diversity were insignificant at 0-35 cm. Correlation analysis indicated that the forest trees grew better as the soil microbial diversity index increased. Therefore, construction of the Tarim Desert Highway shelter-forest promoted soil biological development; however, for enhancing sand control efficiency and promoting sand development, we should consider the effects of site condition in the construction and regeneration of shelter-forest ecological projects. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Surface runoff and soil erosion by difference of surface cover characteristics using by an oscillating rainfall simulator

NASA Astrophysics Data System (ADS)

Kim, J. K.; Kim, M. S.; Yang, D. Y.

2017-12-01

Sediment transfer within hill slope can be changed by the hydrologic characteristics of surface material on hill slope. To better understand sediment transfer of the past and future related to climate changes, studies for the changes of soil erosion due to hydrological characteristics changes by surface materials on hill slope are needed. To do so, on-situ rainfall simulating test was conducted on three different surface conditions, i.e. well covered with litter layer condition (a), undisturbed bare condition (b), and disturbed bare condition (c) and these results from rainfall simulating test were compared with that estimated using the Limburg Soil Erosion Model (LISEM). The result from the rainfall simulating tests showed differences in the infiltration rate (a > b > c) and the highest soil erosion rate was occurred on c condition. The result from model also was similar to those from rainfall simulating tests, however, the difference from the value of soil erosion rate between two results was quite large on b and c conditions. These results implied that the difference of surface conditions could change the surface runoff and soil erosion and the result from the erosion model might significantly underestimate on bare surface conditions rather than that from rainfall simulating test.

Toxicity of a metal(loid)-polluted agricultural soil to Enchytraeus crypticus changes under a global warming perspective: Variations in air temperature and soil moisture content.

PubMed

González-Alcaraz, M Nazaret; van Gestel, Cornelis A M

2016-12-15

This study aimed to assess how the current global warming perspective, with increasing air temperature (20°C vs. 25°C) and decreasing soil moisture content (50% vs. 30% of the soil water holding capacity, WHC), affected the toxicity of a metal(loid)-polluted agricultural soil to Enchytraeus crypticus. Enchytraeids were exposed for 21d to a dilution series of the agricultural soil with Lufa 2.2 control soil under four climate situations: 20°C+50% WHC (standard conditions), 20°C+30% WHC, 25°C+50% WHC, and 25°C+30% WHC. Survival, reproduction and bioaccumulation of As, Cd, Co, Cu, Fe, Mn, Ni, Pb and Zn were obtained as endpoints. Reproduction was more sensitive to both climate factors and metal(loid) pollution. High soil salinity (electrical conductivity~3dSm -1 ) and clay texture, even without the presence of high metal(loid) concentrations, affected enchytraeid performance especially at drier conditions (≥80% reduction in reproduction). The toxicity of the agricultural soil increased at drier conditions (10% reduction in EC10 and EC50 values for the effect on enchytraeid reproduction). Changes in enchytraeid performance were accompanied by changes in As, Fe, Mn, Pb and Zn bioaccumulation, with lower body concentrations at drier conditions probably due to greater competition with soluble salts in the case of Fe, Mn, Pb and Zn. This study shows that apart from high metal(loid) concentrations other soil properties (e.g. salinity and texture) may be partially responsible for the toxicity of metal(loid)-polluted soils to soil invertebrates, especially under changing climate conditions. Copyright © 2016 Elsevier B.V. All rights reserved.

The impact of nitrification inhibitor DMPP on N2O, NO and N2 emissions at different soil moisture conditions in grassland soil

NASA Astrophysics Data System (ADS)

Wu, D.; Cardenas, L. M.; Sanz, S. C.; Brueggemann, N.; Loick, N.; Liu, S.; Bol, R.

2016-12-01

Emissions of gaseous forms of nitrogen from soil, such as nitrous oxide (N2O) and nitric oxide (NO), have shown great impact on global warming and atmospheric chemistry. Although in soil both nitrification and denitrification could cause N2O and NO emissions, most recent studies demonstrated that denitrification is the dominant process responsible for the increase of atmospheric N2O, while nitrification produces most of NO. The use of nitrification inhibitors (NI) has repeatedly been shown to lower both N2O and NO emissions from agricultural soils; nevertheless, the efficiency of the mitigation effect varies greatly. It is generally assumed that nitrification inhibitors have no direct effect on denitrification. However, the indirect impact, due to the reduced substrate delivery (NO3-) to microsites where denitrification occurs, may have significant effects on denitrification product stoichiometry that may significantly lower soil born N2O emissions. In the present study, soil incubation experiments were carried out in a fully automated continuous-flow incubation system under a He/O2 atmosphere. Ammonium sulfate was applied with and without NI (DMPP) to a UK grassland soil under three different soil moisture conditions (50% WFPS, 65% WFPS, 80% WFPS). With every treatment glucose was applied to supply enough carbon for denitrification. We examined the effect of DMPP on NO, N2O and N2 emissions at different soil moisture conditions which favor nitrification, a mixture of both nitrification and denitrification, or denitrification, respectively. Generally cumulative NO emissions were about 17% of cumulative N2O emissions, while N2 emissions were only detected at high soil moisture condition (80% WFPS). Higher soil moisture increased both N2O and NO emissions. DMPP application increased N2 emissions at soil moisture condition favoring denitrification. Although the application of DMPP significantly mitigated both N2O and NO emissions in all DMPP treatments, the efficiency of the mitigation effect varied with different soil moisture conditions. Overall, DMPP application mitigated about 40- 60% N2O emissions and 50-70% NO emissions during the 44-day incubation period.

Soil biological activity at European scale - two calculation concepts

NASA Astrophysics Data System (ADS)

Krüger, Janine; Rühlmann, Jörg

2014-05-01

The CATCH-C project aims to identify and improve the farm-compatibility of Soil Management Practices including to promote productivity, climate change mitigation and soil quality. The focus of this work concentrates on turnover conditions for soil organic matter (SOM). SOM is fundamental for the maintenance of quality and functions of soils while SOM storage is attributed a great importance in terms of climate change mitigation. The turnover conditions depend on soil biological activity characterized by climate and soil properties. To assess the turnover conditions two model concepts are applied: (I) Biological active time (BAT) regression approach derived from CANDY model (Franko & Oelschlägel 1995) expresses the variation of air temperature, precipitation and soil texture as a timescale and an indicator of biological activity for soil organic matter (SOM) turnover. (II) Re_clim parameter within the Introductory Carbon Balance Model (Andrén & Kätterer 1997) states the soil temperature and soil water to estimate soil biological activity. The modelling includes two strategies to cover the European scale and conditions. BAT was calculated on a 20x20 km grid basis. The European data sets of precipitation and air temperature (time period 1901-2000, monthly resolution), (Mitchell et al. 2004) were used to derive long-term averages. As we focus on agricultural areas we included CORINE data (2006) to extract arable land. The resulting BATs under co-consideration of the main soil textures (clay, silt, sand and loam) were investigated per environmental zone (ENZs, Metzger et al. 2005) that represents similar conditions for precipitation, temperature and relief to identify BAT ranges and hence turnover conditions for each ENZ. Re_clim was quantified by climatic time series of more than 250 weather stations across Europe presented by Klein Tank et al. (2002). Daily temperature, precipitation and potential evapotranspiration (maximal thermal extent) were used to calculate soil temperature and water storage in the arable layer thereby differentiating soil textures exclusively in main types (clay, silt, sand and loam). Similar to the BAT investigation it was of further interest to investigate how the re_clim parameter range behaves per ENZ. We will discuss the analyzed results of both strategies in a comparative manner to assess SOM turnover conditions across Europe. Both concepts help to separate different turnover activities and to indicate organic matter input in order to maintain the given SOM. The assessment could provide local recommendations for local adaptations of soil management practices. CATCH-C is funded within the 7th Framework Programme for Research, Technological Development and Demonstration, Theme 2 - Biotechnologies, Agriculture & Food (Grant Agreement N° 289782).

The Past, Present, and Future of Soils and Human Health Studies

NASA Astrophysics Data System (ADS)

Brevik, E. C.; Sauer, T. J.

2012-04-01

The idea that human health is tied to the soil is not a new one. As far back as approximately 1400 B.C. the Bible depicts Moses as understanding that fertile soil was essential to the well-being of his people. While exploring Canaan, Moses charged the men he sent to evaluate the fertility of the soil. In 400 B.C. the Greek philosopher Hippocrates provided a list of things that should be considered in a proper medical evaluation, including the ground. By the late 1700 and early 1800s, American farmers had recognized that soil properties had some connection to human health. In "Letters from an American Farmer", published in 1792, J. Hector St. John De Crèvecoeur stated "Men are like plants; the goodness and flavor of the fruit proceeds from the peculiar soil and exposition in which they grow". And in "Larding the Lean Earth", published in 2002, S. Stoll noted that North American farmers in the early 1800s recognized a link between an enduring agriculture and an enduring society, leading them to become concerned about the fertility of their soils and to seek ways of improving the soil in order to insure a healthy society. Continuing into the first half of the 20th Century, a 1940 publication by the International Harvester Company noted that poor soils lead to "stoop-shouldered, poverty-stricken people." Then, in 1947, Sir Albert Howard published his landmark work "The Soil and Health: A Study of Organic Agriculture", a work that took a critical look at modern production agriculture and at the link between soil fertility and health. Despite these various lines of evidence of some earlier level of understanding that healthy soils are required for healthy people, the scientific study of the relationship between soils and human health is a fairly new undertaking. In his 1997 work "Soil and Human Health: A Review", M.A. Oliver states "… there is a dearth of quantitative information on the relations between elements in the soil and human health;…there is much speculation and anecdotal evidence." So, the scientific study of soils and human health is a recent undertaking, but the idea that healthy soils are required for healthy people is not a particularly new one. In the modern world, we recognize that soils have a distinct influence on human health. We recognize that soils influence 1) food availability and quality (food security), 2) human contact with various chemicals, and 3) human contact with various pathogens. Soils and human health studies include investigations into nutrient supply through the food web and routes of exposure to chemicals and pathogens. However, making strong, scientific connections between soils and human health can be difficult. There are multiple variables to consider in the soil environment, meaning traditional scientific studies that seek to isolate and manipulate a single variable often do not provide meaningful data. The complete study of soils and human health also involves many different specialties such as soil scientists, toxicologists, medical professionals, anthropologists, etc. These groups do not traditionally work together on research projects, and do not always effectively communicate with one another. Climate change and how it will affect the soil environment/ecosystem going into the future is another variable we need to get a better understanding of. Future successes in soils and human health research will require effectively addressing difficult issues such as these.

Disaggregation of remotely sensed soil moisture under all sky condition using machine learning approach in Northeast Asia

NASA Astrophysics Data System (ADS)

Kim, S.; Kim, H.; Choi, M.; Kim, K.

2016-12-01

Estimating spatiotemporal variation of soil moisture is crucial to hydrological applications such as flood, drought, and near real-time climate forecasting. Recent advances in space-based passive microwave measurements allow the frequent monitoring of the surface soil moisture at a global scale and downscaling approaches have been applied to improve the spatial resolution of passive microwave products available at local scale applications. However, most downscaling methods using optical and thermal dataset, are valid only in cloud-free conditions; thus renewed downscaling method under all sky condition is necessary for the establishment of spatiotemporal continuity of datasets at fine resolution. In present study Support Vector Machine (SVM) technique was utilized to downscale a satellite-based soil moisture retrievals. The 0.1 and 0.25-degree resolution of daily Land Parameter Retrieval Model (LPRM) L3 soil moisture datasets from Advanced Microwave Scanning Radiometer 2 (AMSR2) were disaggregated over Northeast Asia in 2015. Optically derived estimates of surface temperature (LST), normalized difference vegetation index (NDVI), and its cloud products were obtained from MODerate Resolution Imaging Spectroradiometer (MODIS) for the purpose of downscaling soil moisture in finer resolution under all sky condition. Furthermore, a comparison analysis between in situ and downscaled soil moisture products was also conducted for quantitatively assessing its accuracy. Results showed that downscaled soil moisture under all sky condition not only preserves the quality of AMSR2 LPRM soil moisture at 1km resolution, but also attains higher spatial data coverage. From this research we expect that time continuous monitoring of soil moisture at fine scale regardless of weather conditions would be available.

Numerical and Experimental Investigation of Soil Heterogeneity around Landmines in Natural Soil

NASA Astrophysics Data System (ADS)

Wallen, B.; Smits, K. M.; Howington, S. E.

2015-12-01

The environment in which landmines are placed is oftentimes highly heterogeneous. These heterogeneities such as differences in soil type, packing and moisture, combined with changes in surface and climate conditions can oftentimes mask the presence of the mine. Understanding the impact of heterogeneity on heat and mass transfer behavior in the vicinity of landmines is paramount to properly identifying landmine locations for demining operations. This study investigates the impact of soil heterogeneity on soil moisture and temperature distributions around buried objects with the goal of increasing our ability to model and predict the environmental conditions that are most dynamic to mine detection performance. A ten-day field experiment was conducted in which two anti-personnel landmines at different depths and a limestone block of comparable size were buried. The site was instrumented with a series of sensors, monitoring atmospheric, surface and subsurface conditions to include measurements of soil moisture, soil and air temperature, relative humidity, vapor concentration, and meteorological conditions such as wind speed and net radiation. Infrared thermal imaging was used to provide continuous profiles of surface temperature conditions. The soil was well characterized in the laboratory to provide good understanding of field conditions for numerical modeling efforts. Experimental results demonstrate the strongest thermal contrast between shallow landmine emplacement and the surrounding soil occurring as the sun approaches its zenith and two hours after sunset until the sun directly impacts the soil above the landmine. A finite-element model of fluid flow and heat transport through porous media is compared against experimental observations, capturing the diurnal variation. A validated model, like this one, offers the opportunity to improve landmine detection probabilities and reduce false alarms caused by environmental variability.

Microbial C:P stoichiometry is shaped by redox conditions along an elevation gradient in humid tropical rainforests

NASA Astrophysics Data System (ADS)

Lin, Y.; Gross, A.; Silver, W. L.

2017-12-01

Elemental stoichiometry of microorganisms is intimately related to ecosystem carbon and nutrient fluxes and is ultimately controlled by the chemical (plant tissue, soil, redox) and physical (temperature, moisture, aeration) environment. Previous meta-analyses have shown that the C:P ratio of soil microbial biomass exhibits significant variations among and within biomes. Little is known about the underlying causes of this variability. We examined soil microbial C:P ratios along an elevation gradient in the Luquillo Experimental Forest in Puerto Rico. We analyzed soils from mixed forest paired with monodominant palm forest every 100 m from 300 m to 1000 m a.s.l.. Mean annual precipitation increased with increasing elevation, resulting in stronger reducing conditions and accumulation of soil Fe(II) at higher elevations. The mean value and variability of soil microbial C:P ratios generally increased with increasing elevation except at 1000 m. At high elevations (600-900 m), the average value of microbial C:P ratio (108±10:1) was significantly higher than the global average ( 55:1). We also found that soil organic P increased with increasing elevation, suggesting that an inhibition of organic P mineralization, not decreased soil P availability, may cause the high microbial C:P ratio. The soil microbial C:P ratio was positively correlated with soil HCl-extractable Fe(II), suggesting that reducing conditions may be responsible for the elevational changes observed. In a follow-up experiment, soils from mixed forests at four elevation levels (300, 500, 700, and 1000 m) were incubated under aerobic and anaerobic conditions for two weeks. We found that anaerobic incubation consistently increased the soil microbial C:P ratio relative to the aerobic incubation. Overall, our results indicate that redox conditions can shift the elemental composition of microbial biomass. The high microbial C:P ratios induced under anoxic conditions may reflect inhibition of microbial P mineralization and/or immobilization under reducing conditions. These results will help us to better understand the patterns of nutrient cycling and microbial activity across macro-scale environmental gradients.

Changes in the enzymatic activity of soil samples upon their storage

NASA Astrophysics Data System (ADS)

Dadenko, E. V.; Kazeev, K. Sh.; Kolesnikov, S. I.; Val'Kov, V. F.

2009-12-01

The influence of the duration and conditions of storage of soil samples on the activity of soil enzymes (catalase, β-fructofuranosidase, and dehydrogenase) was studied for the main soils of southern Russia (different subtypes of chernozems, chestnut soils, brown forest soils, gray forest soils, solonetzes, and solonchaks). The following soil storage conditions were tested: (1) the air-dry state at room temperature, (2) the airdry state at a low positive (in a refrigerator, +4°C) temperature, (3) naturally moist samples at a low positive temperature, and (4) naturally moist samples at a negative (in a freezer, -5°C) temperature. It was found that the sample storing caused significant changes in the enzymatic activities, which depended on the soil type, the land use, the type of enzyme, and the duration and conditions of the sample storage. In the course of the storage, the changes in the enzymatic activity had a nonlinear character. The maximum changes were observed in the initial period (up to 12 weeks). Then, a very gradual decrease in the activity of the studied enzymes was observed. Upon the long-term (>12 weeks) storage under the different conditions, the difference in the activities of the soil enzymes became less pronounced. The storage of soil samples in the air-dried state at room temperature can be recommended for mass investigations.

[Removal of volatile organic compounds in soils by soil vapor extraction (SVE)].

PubMed

Yin, Fu-xiang; Zhang, Sheng-tian; Zhao, Xin; Feng, Ke; Lin, Yu-suo

2011-05-01

An experiment study has been carried out to investigate effects of the diameter of soil columns, the size of soil particulate and different contaminants on efficiency of simulated soil vapor extraction (SVE). Experiments with benzene, toluene, ethylbenzene and n-propylbenzene contaminated soils showed that larger bottom area/soil height (S/H) of the columns led to higher efficiency on removal of contaminants. Experiments with contaminated soils of different particulate size showed that the efficiency of SVE decreased with increases in soil particulate size, from 10 mesh to between 20 mesh and 40 mesh and removal of contaminants in soils became more difficult. Experiments with contaminated soils under different ventilation rates suggested that soil vapor extraction at a ventilation rate of 0.10 L x min(-1) can roughly remove most contaminants from the soils. Decreasing of contaminants in soils entered tailing stages after 12 h, 18 h and 48 h for benzene, toluene and ethylbenzene, respectively. Removal rate of TVOCs (Total VOCs) reached a level as high as 99.52%. The results of the experiment have indicated that molecule structure and properties of the VOCs are also important factors which have effects on removal rates of the contaminants. Increases in carbon number on the benzene ring, decreases in vapor pressure and volatile capability resulted in higher difficulties in soil decontamination. n-propylbenzene has a lower vapor pressure than toluene and ethylbenzene which led to a significant retard effect on desorption and volatilization of benzene and ethylbenzene.

Soil-ecological conditions of Korean pine growth in its natural area and upon introduction in the European part of Russia

NASA Astrophysics Data System (ADS)

Voityuk, M. M.

2015-05-01

Socioeconomic expediency and soil-ecological potential of introducing Korean pine ( Pinus koraiensis) in the forest zone of the European part of Russia are discussed. The specificity of soil-ecological conditions and technologies applied for growing Korean pine in some tree farms in the Far East region and in the European part of Russia are compared. The main soil-ecological factors and optimum soil parameters for the successful development of Korean pine in its natural and introduction areas are determined. It is shown that development of Korean pine seedlings on well-drained soils depends on the contents of potassium, humus, and physical clay in the soils. The seedlings gain maximum size upon their growing on soddypodzolic soils (Retisols). The analysis of mineral nutrition of pine seedlings of different ages, soil conditions, and seasonal growth phases shows that the contents of potassium and some microelements play the leading role in the successful growth of introduced Korean pine.

Laboratory simulations of Martian surface parameters and the biological response of terrestrial model organisms to 'extreme' environments

NASA Astrophysics Data System (ADS)

Rettberg, P.; Moller, R.; Pogoda de La Vega, U.; Rabbow, E.; Panitz, C.; Mohlmann, D.; Reitz, G.

For the development of adequate instruments and methods for in situ life detection analysis and for the avoidance of contaminating of Mars by terrestrial life forms introduced to it's surface unintentionally, it is necessary to understand the potential and limits of life on Earth. Whereas it is possible to test most of the environmental parameters of Mars separately in the laboratory, like diurnal and seasonal temperature cyles, pressure, atmospheric composition, and to investigate their biological effects in detail, it is technically more difficult to simulate two or more parameters at the same time. The realistic simulation of a complete Martian surface environment is a considerable technical challenge. It is especially difficult to reproduce the Martian UV climate realistically. Up to now no total Mars simulation was performed in one single experiment which should include diurnal cycles of temperature, UV radiation and humidity in a simulated Martian atmosphere and at Martian pressure, with Martian soil analogues, dust particles, and ionising radiation. However, it is absolutely essential to investigate the biological effects of combined environmental parameters, because it is already known for some cases that biological effects might not necessarily be additive, but can be synergistic or antagonistic. A prominent example is the synergistic effect of vacuum and UV radiation on the survivability of B. subtilis spores. From several investigations in the last decades the Martian UV climate with it's energy-rich short-wavelength radiation down to 200 nm turned out to be the most important deleterious environmental parameter on Mars. Direct UV exposure caused a rapid and nearly complete inactivation of spores. However, thin layers of Martian soil analogue material, like simulated standard Mars JSC-1 or Fe-montmorillonite, are sufficient to shield spores from the deleterious effects of UV radiation. From these results it can be concluded that in spite of the destructive UV climate at least a part of a microbial population might be able to escape the inactiviation by UV radiation, if covered accidentally by Martian dust and soil particles. Up to now the molecular basis of the strong oxidizing properties of Martian soil found 1 by the Viking landers is not completely understood. This chemical reactivity capable of decomposing organic molecules was attributed to the presence of one or more as- yet-unidentified inorganic superoxides or peroxides in the Martian soil. The biological consequences of these photochemical reactions are not yet investigated in detail, although it is known that B. subtilis spores are able to withstand oxidative conditions to a certain degree. The determination of the survival of microorganisms under the physical and chemical `extremes' of Mars will provide detailed insights into the potential for contamination that will allow the development and improvement of planetary protection measures. 2

Improving root-zone soil properties for Trembling Aspen in a reconstructed mine-site soil

NASA Astrophysics Data System (ADS)

Dyck, M. F.; Sabbagh, P.; Bockstette, S.; Landhäusser, S.; Pinno, B.

2014-12-01

Surface mining activities have significantly depleted natural tree cover, especially trembling aspen (Populus tremuloides), in the Boreal Forest and Aspen Parkland Natural Regions of Alberta. The natural soil profile is usually destroyed during these mining activities and soil and landscape reconstruction is typically the first step in the reclamation process. However, the mine tailings and overburden materials used for these new soils often become compacted during the reconstruction process because they are subjected to high amounts of traffic with heavy equipment. Compacted soils generally have low porosity and low penetrability through increased soil strength, making it difficult for roots to elongate and explore the soil. Compaction also reduces infiltration capacity and drainage, which can cause excessive runoff and soil erosion. To improve the pore size distribution and water transmission, subsoil ripping was carried out in a test plot at Genesee Prairie Mine, Alberta. Within the site, six replicates with two treatments each, unripped (compacted) and ripped (decompacted), were established with 20-m buffers between them. The main objective of this research was to characterize the effects of subsoil ripping on soil physical properties and the longevity of those effects.as well as soil water dynamics during spring snowmelt. Results showed improved bulk density, pore size distribution and water infiltration in the soil as a result of the deep ripping, but these improvements appear to be temporary.

Comparative reduction of Norwalk virus, poliovirus type 1, F+ RNA coliphage MS2 and Escherichia coli in miniature soil columns.

PubMed

Meschke, J S; Sobsey, M D

2003-01-01

Norwalk-like viruses (NLVs) are important agents of waterborne illness and have been linked to several groundwater-related outbreaks. The presence of human enteric viruses, in particular the presence of NLVs, is difficult to detect in the environment. Consequently, surrogate organisms are typically used as indicators of viruses from faecal contamination. Whether traditional bacterial indicators are reliable indicators for viral pathogens remains uncertain. Few studies have directly compared mobility and reduction of bacterial indicators (e.g. coliforms, Escherichia coli) and other surrogate indicators (coliphages) with pathogenic human viruses in soil systems. In this study the mobility and comparative reduction of the prototype NLV, Norwalk Virus (NV), was compared to poliovirus 1 (PV1), a bacterial indicator (E coli, EC) and a viral indicator (coliphage MS2) through miniature soil columns. Replicate, 10 cm deep, miniature columns were prepared using three soils representing a range of soil textures (sand, organic muck, and clay). Columns were initially conditioned, then incubated at 10-14 degrees C, dosed twice weekly for 8 weeks with one column pore volume of virus-seeded groundwater per dose, followed by 8 weeks of dosing with one column pore volume per dose of unseeded, simulated rainwater. Columns were allowed to drain after each dosing until an effluent volume equivalent to an applied dose was collected. Column effluents and doses were assayed for all viruses and EC. Rapid mobility with minimal reduction was observed for all organisms in the sand. Similar reductions were observed in organic muck for most organisms but NV showed a greater reduction. No organisms were shown to pass through the clay columns. Elution of viruses, in particular PV1, from the columns was gradual. After cessation of microbe dosing, E. coli was less detectable than viruses in column effluents and, therefore, unreliable as a virus indicator.

Soil Science self-learning based on the design and conduction of experiments

NASA Astrophysics Data System (ADS)

Jordán, A.; Bárcenas-Moreno, G.; Zavala, L. M.

2012-04-01

This paper presents an experience for introducing the methodology of project-based learning (PBL) in the area of Soil Science in the University of Sevilla (Spain). Currently, teachers try to enhance practical experience of university students in a complementary manner to theoretical knowledge. However, many times this is a difficult process. Practice is an important part of personal work in the vast majority of subjects that degree students receive, since the implementation of the EHEA. In most cases, these experiences are presented as partial small experiments or projects, assigned to the area-specific knowledge agenda. Certain sciences, such as Soil Science, however, require synthesis and integration capabilities of previous knowledge. It is therefore necessary to develop practical programs that address the student not only to the performance of laboratory determinations, but to the formulation of hypotheses, experimental design and problem solving, whether in groups or individually, situated in a wide context and allowing students to make connections with other areas of knowledge. This project involves the development of teamwork experiments, for the study real cases and problems and making decisions in the field of Soil Science. The results of the experimental work were publicly exposed as posters and oral presentations and were discussed during a mini-congress open to students and a general audience. The open and dynamic nature of the project substantially improves student motivation, which adds value to our project. Due to the multidisciplinary character of Soil Science it is relatively easy to propose projects of some complexity, and therefore, provides good conditions for introducing the PBL methodology. The teacher's role is also important and is not limited to observe or qualify the students, but it is a catalyst for learning. It is important that teacher give the leadership of the process and make the students themselves feel the protagonists of the project.

A new field method to characterise the runoff generation potential of burned hillslopes

NASA Astrophysics Data System (ADS)

Sheridan, Gary; Lane, Patrick; Langhans, Christoph

2016-04-01

The prediction of post fire runoff generation is critical for the estimation of post fire erosion processes and rates. Typical field measures for determining infiltration model parameters include ring infiltrometers, tension infiltrometers, rainfall simulators and natural runoff plots. However predicting the runoff generating potential of post-fire hillslopes is difficult due to the high spatial variability of soil properties relative to the size of the measurement method, the poorly understood relationship between water repellence and runoff generation, known scaling issues with all the above hydraulic measurements, and logistical limitations for measurements in remote environments. In this study we tested a new field method for characterizing surface runoff generation potential that overcomes these limitations and is quick, simple and cheap to apply in the field. The new field method involves the manual application of a 40mm depth of Brilliant Blue FCF food dye along a 10cm wide and 5m long transect along the contour under slightly-ponded conditions. After 24 hours the transect is excavated to a depth of 10cm and the percentage dyed area within the soil profile recorded manually. The dyed area is an index of infiltration potential of the soil during intense rainfall events, and captures both spatial variability and water repellence effects. The dye measurements were made adjacent to long term instrumented post fire rainfall-runoff plots on 7 contrasting soil types over a 6 month period, and the results show surprisingly strong correlations (r2 = 0.9) between the runoff-ratio from the plots and the dyed area. The results are used to develop an initial conceptual model that links the dye index with an infiltration model and parameters suited to burnt hillslopes. The capacity of this method to provide a simple, and reliable indicator of post fire runoff potential from different fire severities, soil types and treatments is explored in this presentation.

Belowground plant development measured with magnetic resonance imaging (MRI): exploiting the potential for non-invasive trait quantification using sugar beet as a proxy

PubMed Central

Metzner, Ralf; van Dusschoten, Dagmar; Bühler, Jonas; Schurr, Ulrich; Jahnke, Siegfried

2014-01-01

Both structural and functional properties of belowground plant organs are critical for the development and yield of plants but, compared to the shoot, much more difficult to observe due to soil opacity. Many processes concerning the belowground plant performance are not fully understood, in particular spatial and temporal dynamics and their interrelation with environmental factors. We used Magnetic Resonance Imaging (MRI) as a noninvasive method to evaluate which traits can be measured when a complex plant organ is monitored in-vivo while growing in the soil. We chose sugar beet (Beta vulgaris ssp. vulgaris) as a model system. The beet consists mainly of root tissues, is rather complex regarding tissue structure and responses to environmental factors, and thereby a good object to test the applicability of MRI for 3D phenotyping approaches. Over a time period of up to 3 months, traits such as beet morphology or anatomy were followed in the soil and the effect of differently sized pots on beet fresh weight calculated from MRI data was studied. There was a clear positive correlation between the pot size and the increase in fresh weight of a sugar beet over time. Since knowledge of the development of internal beet structures with several concentric cambia, vascular and parenchyma rings is still limited, we consecutively acquired 3D volumetric images on individual plants using the MRI contrast parameter T2 to map the development of rings at the tissue level. This demonstrates that MRI provides versatile protocols to non-invasively measure plant traits in the soil. It opens new avenues to investigate belowground plant performance under adverse environmental conditions such as drought, nutrient shortage, or soil compaction to seek for traits of belowground organs making plants more resilient to stress. PMID:25278947

Adjustment of corn nitrogen in-season fertilization based on soil texture and weather conditions: a Meta-analysis of North American trials

USDA-ARS?s Scientific Manuscript database

Soil properties and weather conditions are known to affect soil nitrogen (N) availability and plant N uptake. However, studies examining N response as affected by soil and weather sometimes give conflicting results. Meta-analysis is a statistical method for estimating treatment effects in a series o...

Spatial and Temporal Influences on Carbon Storage in Hydric Soils of the Conterminous United States

NASA Astrophysics Data System (ADS)

Sundquist, E. T.; Ackerman, K.; Bliss, N.; Griffin, R.; Waltman, S.; Windham-Myers, L.

2016-12-01

Defined features of hydric soils persist over extensive areas of the conterminous United States (CUS) long after their hydric formation conditions have been altered by historical changes in land and water management. These legacy hydric features may represent previous wetland environments in which soil carbon storage was significantly higher before the influence of human activities. We hypothesize that historical alterations of hydric soil carbon storage can be approximated using carefully selected estimates of carbon storage in currently identified hydric soils. Using the Soil Survey Geographic (SSURGO) database, we evaluate carbon storage in identified hydric soil components that are subject to discrete ranges of current or recent conditions of flooding, ponding, and other indicators of hydric and non-hydric soil associations. We check our evaluations and, where necessary, adjust them using independently published soil data. We compare estimates of soil carbon storage under various hydric and non-hydric conditions within proximal landscapes and similar biophysical settings and ecosystems. By combining these setting- and ecosystem-constrained comparisons with the spatial distribution and attributes of wetlands in the National Wetlands Inventory, we impute carbon storage estimates for soils that occur in current wetlands and for hydric soils that are not associated with current wetlands. Using historical data on land use and water control structures, we map the spatial and temporal distribution of past changes in land and water management that have affected hydric soils. We combine these maps with our imputed carbon storage estimates to calculate ranges of values for historical and present-day carbon storage in hydric soils throughout the CUS. These estimates may provide useful constraints for projections of potential carbon storage in hydric soils under future conditions.

Soil pathogen-aphid interactions under differences in soil organic matter and mineral fertilizer.

PubMed

van Gils, Stijn; Tamburini, Giovanni; Marini, Lorenzo; Biere, Arjen; van Agtmaal, Maaike; Tyc, Olaf; Kos, Martine; Kleijn, David; van der Putten, Wim H

2017-01-01

There is increasing evidence showing that microbes can influence plant-insect interactions. In addition, various studies have shown that aboveground pathogens can alter the interactions between plants and insects. However, little is known about the role of soil-borne pathogens in plant-insect interactions. It is also not known how environmental conditions, that steer the performance of soil-borne pathogens, might influence these microbe-plant-insect interactions. Here, we studied effects of the soil-borne pathogen Rhizoctonia solani on aphids (Sitobion avenae) using wheat (Triticum aestivum) as a host. In a greenhouse experiment, we tested how different levels of soil organic matter (SOM) and fertilizer addition influence the interactions between plants and aphids. To examine the influence of the existing soil microbiome on the pathogen effects, we used both unsterilized field soil and sterilized field soil. In unsterilized soil with low SOM content, R. solani addition had a negative effect on aphid biomass, whereas it enhanced aphid biomass in soil with high SOM content. In sterilized soil, however, aphid biomass was enhanced by R. solani addition and by high SOM content. Plant biomass was enhanced by fertilizer addition, but only when SOM content was low, or in the absence of R. solani. We conclude that belowground pathogens influence aphid performance and that the effect of soil pathogens on aphids can be more positive in the absence of a soil microbiome. This implies that experiments studying the effect of pathogens under sterile conditions might not represent realistic interactions. Moreover, pathogen-plant-aphid interactions can be more positive for aphids under high SOM conditions. We recommend that soil conditions should be taken into account in the study of microbe-plant-insect interactions.

Moisture rivals temperature in limiting photosynthesis by trees establishing beyond their cold-edge range limit under ambient and warmed conditions.

PubMed

Moyes, Andrew B; Germino, Matthew J; Kueppers, Lara M

2015-09-01

Climate change is altering plant species distributions globally, and warming is expected to promote uphill shifts in mountain trees. However, at many cold-edge range limits, such as alpine treelines in the western United States, tree establishment may be colimited by low temperature and low moisture, making recruitment patterns with warming difficult to predict. We measured response functions linking carbon (C) assimilation and temperature- and moisture-related microclimatic factors for limber pine (Pinus flexilis) seedlings growing in a heating × watering experiment within and above the alpine treeline. We then extrapolated these response functions using observed microclimate conditions to estimate the net effects of warming and associated soil drying on C assimilation across an entire growing season. Moisture and temperature limitations were each estimated to reduce potential growing season C gain from a theoretical upper limit by 15-30% (c. 50% combined). Warming above current treeline conditions provided relatively little benefit to modeled net assimilation, whereas assimilation was sensitive to either wetter or drier conditions. Summer precipitation may be at least as important as temperature in constraining C gain by establishing subalpine trees at and above current alpine treelines as seasonally dry subalpine and alpine ecosystems continue to warm. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

Identification of biogeochemical hot spots using time-lapse hydrogeophysics

NASA Astrophysics Data System (ADS)

Franz, T. E.; Loecke, T.; Burgin, A.

2016-12-01

The identification and monitoring of biogeochemical hot spots and hot moments is difficult using point based sampling techniques and sensors. Without proper monitoring and accounting of water, energy, and trace gas fluxes it is difficult to assess the environmental footprint of land management practices. One key limitation is optimal placement of sensors/chambers that adequately capture the point scale fluxes and thus a reasonable integration to landscape scale flux. In this work we present time-lapse hydrogeophysical imaging at an old agricultural field converted into a wetland mitigation bank near Dayton, Ohio. While the wetland was previously instrumented with a network of soil sensors and surface chambers to capture a suite of state variables and fluxes, we hypothesize that time-lapse hydrogeophysical imaging is an underutilized and critical reconnaissance tool for effective network design and landscape scaling. Here we combine the time-lapse hydrogeophysical imagery with the multivariate statistical technique of Empirical Orthogonal Functions (EOF) in order to isolate the spatial and temporal components of the imagery. Comparisons of soil core information (e.g. soil texture, soil carbon) from around the study site and organized within like spatial zones reveal statistically different mean values of soil properties. Moreover, the like spatial zones can be used to identify a finite number of future sampling locations, evaluation of the placement of existing sensors/chambers, upscale/downscale observations, all of which are desirable techniques for commercial use in precision agriculture. Finally, we note that combining the EOF analysis with continuous monitoring from point sensors or remote sensing products may provide a robust statistical framework for scaling observations through time as well as provide appropriate datasets for use in landscape biogeochemical models.

Atomic Force Microscopy for Soil Analysis

NASA Astrophysics Data System (ADS)

gazze, andrea; doerr, stefan; dudley, ed; hallin, ingrid; matthews, peter; quinn, gerry; van keulen, geertje; francis, lewis

2016-04-01

Atomic Force Microscopy (AFM) is a high-resolution surface-sensitive technique, which provides 3-dimensional topographical information and material properties of both stiff and soft samples in their natural environments. Traditionally AFM has been applied to samples with low roughness: hence its use for soil analysis has been very limited so far. Here we report the optimization settings required for a standardization of high-resolution and artefact-free analysis of natural soil with AFM: soil immobilization, AFM probe selection, artefact recognition and minimization. Beyond topography, AFM can be used in a spectroscopic mode to evaluate nanomechanical properties, such as soil viscosity, stiffness, and deformation. In this regards, Bruker PeakForce-Quantitative NanoMechanical (QNM) AFM provides a fast and convenient way to extract physical properties from AFM force curves in real-time to obtain soil nanomechanical properties. Here we show for the first time the ability of AFM to describe the topography of natural soil at nanometre resolution, with observation of micro-components, such as clays, and of nano-structures, possibly of biotic origin, the visualization of which would prove difficult with other instrumentations. Finally, nanomechanical profiling has been applied to different wettability states in soil and the respective physical patterns are discussed.

Optimization of a sample processing protocol for recovery of Bacillus anthracis spores from soil

USGS Publications Warehouse

Silvestri, Erin E.; Feldhake, David; Griffin, Dale; Lisle, John T.; Nichols, Tonya L.; Shah, Sanjiv; Pemberton, A; Schaefer III, Frank W

2016-01-01

Following a release of Bacillus anthracis spores into the environment, there is a potential for lasting environmental contamination in soils. There is a need for detection protocols for B. anthracis in environmental matrices. However, identification of B. anthracis within a soil is a difficult task. Processing soil samples helps to remove debris, chemical components, and biological impurities that can interfere with microbiological detection. This study aimed to optimize a previously used indirect processing protocol, which included a series of washing and centrifugation steps. Optimization of the protocol included: identifying an ideal extraction diluent, variation in the number of wash steps, variation in the initial centrifugation speed, sonication and shaking mechanisms. The optimized protocol was demonstrated at two laboratories in order to evaluate the recovery of spores from loamy and sandy soils. The new protocol demonstrated an improved limit of detection for loamy and sandy soils over the non-optimized protocol with an approximate matrix limit of detection at 14 spores/g of soil. There were no significant differences overall between the two laboratories for either soil type, suggesting that the processing protocol will be robust enough to use at multiple laboratories while achieving comparable recoveries.

Behavior of nonplastic silty soils under cyclic loading.

PubMed

Ural, Nazile; Gunduz, Zeki

2014-01-01

The engineering behavior of nonplastic silts is more difficult to characterize than is the behavior of clay or sand. Especially, behavior of silty soils is important in view of the seismicity of several regions of alluvial deposits in the world, such as the United States, China, and Turkey. In several hazards substantial ground deformation, reduced bearing capacity, and liquefaction of silty soils have been attributed to excess pore pressure generation during dynamic loading. In this paper, an experimental study of the pore water pressure generation of silty soils was conducted by cyclic triaxial tests on samples of reconstituted soils by the slurry deposition method. In all tests silty samples which have different clay percentages were studied under different cyclic stress ratios. The results have showed that in soils having clay content equal to and less than 10%, the excess pore pressure ratio buildup was quicker with an increase in different cyclic stress ratios. When fine and clay content increases, excess pore water pressure decreases constant cyclic stress ratio in nonplastic silty soils. In addition, the applicability of the used criteria for the assessment of liquefaction susceptibility of fine grained soils is examined using laboratory test results.

Behavior of Nonplastic Silty Soils under Cyclic Loading

PubMed Central

Ural, Nazile; Gunduz, Zeki

2014-01-01

The engineering behavior of nonplastic silts is more difficult to characterize than is the behavior of clay or sand. Especially, behavior of silty soils is important in view of the seismicity of several regions of alluvial deposits in the world, such as the United States, China, and Turkey. In several hazards substantial ground deformation, reduced bearing capacity, and liquefaction of silty soils have been attributed to excess pore pressure generation during dynamic loading. In this paper, an experimental study of the pore water pressure generation of silty soils was conducted by cyclic triaxial tests on samples of reconstituted soils by the slurry deposition method. In all tests silty samples which have different clay percentages were studied under different cyclic stress ratios. The results have showed that in soils having clay content equal to and less than 10%, the excess pore pressure ratio buildup was quicker with an increase in different cyclic stress ratios. When fine and clay content increases, excess pore water pressure decreases constant cyclic stress ratio in nonplastic silty soils. In addition, the applicability of the used criteria for the assessment of liquefaction susceptibility of fine grained soils is examined using laboratory test results. PMID:24672343

Biological Soil Crusts: Webs of Life in the Desert

USGS Publications Warehouse

Belnap, Jayne

2001-01-01

Although the soil surface may look like dirt to you, it is full of living organisms that are a vital part of desert ecosystems. This veneer of life is called a biological soil crust. These crusts are found throughout the world, from hot deserts to polar regions. Crusts generally cover all soil spaces not occupied by green plants. In many areas, they comprise over 70% of the living ground cover and are key in reducing erosion, increasing water retention, and increasing soil fertility. In most dry regions, these crusts are dominated by cyanobacteria (previously called blue-green algae), which are one of the oldest known life forms. Communities of soil crusts also include lichens, mosses, microfungi, bacteria, and green algae. These living organisms and their by-products create a continuous crust on the soil surface. The general color, surface appearance, and amount of coverage of these crusts vary depending on climate and disturbance patterns. Immature crusts are generally flat and the color of the soil, which makes them difficult to distinguish from bare ground. Mature crusts, in contrast, are usually bumpy and dark-colored due to the presence of lichens, mosses, and high densities of cyanobacteria and other organisms.

Irrigation Signals Detected From SMAP Soil Moisture Retrievals

NASA Astrophysics Data System (ADS)

Lawston, Patricia M.; Santanello, Joseph A.; Kumar, Sujay V.

2017-12-01

Irrigation can influence weather and climate, but the magnitude, timing, and spatial extent of irrigation are poorly represented in models, as are the resulting impacts of irrigation on the coupled land-atmosphere system. One way to improve irrigation representation in models is to assimilate soil moisture observations that reflect an irrigation signal to improve model states. Satellite remote sensing is a promising avenue for obtaining these needed observations on a routine basis, but to date, irrigation detection in passive microwave satellites has proven difficult. In this study, results show that the new enhanced soil moisture product from the Soil Moisture Active Passive satellite is able to capture irrigation signals over three semiarid regions in the western United States. This marks an advancement in Earth-observing satellite skill and the ability to monitor human impacts on the water cycle.

Predicting hydrological and erosional risks in fire-affected watersheds: recent advances and research gaps

NASA Astrophysics Data System (ADS)

Nunes, João Pedro; Keizer, Jan Jacob

2017-04-01

Models can be invaluable tools to assess and manage the impacts of forest fires on hydrological and erosion processes. Immediately after fires, models can be used to identify priority areas for post-fire interventions or assess the risks of flooding and downstream contamination. In the long term, models can be used to evaluate the long-term implications of a fire regime for soil protection, surface water quality and potential management risks, or determine how changes to fire regimes, caused e.g. by climate change, can impact soil and water quality. However, several challenges make post-fire modelling particularly difficult: • Fires change vegetation cover and properties, such as by changing soil water repellency or by adding an ash layer over the soil; these processes, however are not described in currently used models, so that existing models need to be modified and tested. • Vegetation and soils recover with time since fire, changing important model parameters, so that the recovery processes themselves also need to be simulated, including the role of post-fire interventions. • During the window of vegetation and soil disturbance, particular weather conditions, such as the occurrence of severe droughts or extreme rainfall events, can have a large impact on the amount of runoff and erosion produced in burnt areas, so that models that smooth out these peak responses and rather simulate "long-term" average processes are less useful. • While existing models can simulate reasonable well slope-scale runoff generation and associated sediment losses and their catchment-scale routing, few models can accommodate the role of the ash layer or its transport by overland flow, in spite of its importance for soil fertility losses and downstream contamination. This presentation will provide an overview of the importance of post-fire hydrological and erosion modelling as well as of the challenges it faces and of recent efforts made to overcome these challenges. It will illustrate these challenges with two examples: probabilistic approaches to simulate the impact of different vegetation regrowth and post-fire climate combinations on runoff and erosion; and model developments for post-fire soil water repellency with different levels of complexity. It will also present an inventory of the current state-of-the-art and propose future research directions, both on post-fire models themselves and on their integration with other models in large-scale water resource assessment management.

Using semi-variogram analysis for providing spatially distributed information on soil surface condition for land surface modeling

NASA Astrophysics Data System (ADS)

Croft, Holly; Anderson, Karen; Kuhn, Nikolaus J.

2010-05-01

The ability to quantitatively and spatially assess soil surface roughness is important in geomorphology and land degradation studies. Soils can experience rapid structural degradation in response to land cover changes, resulting in increased susceptibility to erosion and a loss of Soil Organic Matter (SOM). Changes in soil surface condition can also alter sediment detachment, transport and deposition processes, infiltration rates and surface runoff characteristics. Deriving spatially distributed quantitative information on soil surface condition for inclusion in hydrological and soil erosion models is therefore paramount. However, due to the time and resources involved in using traditional field sampling techniques, there is a lack of spatially distributed information on soil surface condition. Laser techniques can provide data for a rapid three dimensional representation of the soil surface at a fine spatial resolution. This provides the ability to capture changes at the soil surface associated with aggregate breakdown, flow routing, erosion and sediment re-distribution. Semi-variogram analysis of the laser data can be used to represent spatial dependence within the dataset; providing information about the spatial character of soil surface structure. This experiment details the ability of semi-variogram analysis to spatially describe changes in soil surface condition. Soil for three soil types (silt, silt loam and silty clay) was sieved to produce aggregates between 1 mm and 16 mm in size and placed evenly in sample trays (25 x 20 x 2 cm). Soil samples for each soil type were exposed to five different durations of artificial rainfall, to produce progressively structurally degraded soil states. A calibrated laser profiling instrument was used to measure surface roughness over a central 10 x 10 cm plot of each soil state, at 2 mm sample spacing. The laser data were analysed within a geostatistical framework, where semi-variogram analysis quantitatively represented the change in soil surface structure during crusting. The laser data were also used to create digital surface models (DSM) of the soil states for visual comparison. This research has shown that aggregate breakdown and soil crusting can be shown quantitatively by a decrease in sill variance (silt soil: 11.67 (control) to 1.08 (after 90 mins rainfall)). Features present within semi-variograms were spatially linked to features at the soil surface, such as soil cracks, tillage lines and areas of deposition. Directional semi-variograms were used to provide a spatially orientated component, where the directional sill variance associated with a soil crack was shown to increase from 7.95 to 19.33. Periodicity within semi-variogram was also shown to quantify the spatial scale of soil cracking networks and potentially surface flowpaths; an average distance between soil cracks of 37 mm closely corresponded to the distance of 38 mm shown in the semi-variogram. The results provide a strong basis for the future retrieval of spatio-temporal variations in soil surface condition. Furthermore, the presence of process-based information on hydrological pathways within semi-variograms may work towards an inclusion of geostatisically-derived information in land surface models and the understanding of complex surface processes at different spatial scales.

Bioremediation of coal contaminated soil under sulfate-reducing condition.

PubMed

Kuwano, Y; Shimizu, Y

2006-01-01

The objective of this study was to investigate the biodegradation of coal-derived hydrocarbons, especially high molecular weight (HMW) components, under anaerobic conditions. For this purpose biodegradation experiments were performed, using specifically designed soil column bioreactors. For the experiment, coal-contaminated soil was prepared, which contains high molecular weight hydrocarbons at high concentration (approx. 55.5 mgC g-drysoil(-1)). The experiment was carried out in two different conditions: sulfate reducing (SR) condition (SO4(2-) = 10 mmol l(-1) in the liquid medium) and control condition (SO4(2-)<0.5 mmol l(-1)). Although no degradation was observed under the control condition, the resin fraction decreased to half (from 6,541 to 3,386 mgC g-soil(-1)) under SR condition, with the concomitant increase of two PAHs (phenanthrene and fluoranthene, 9 and 2.5 times, respectively). From these results, we could conclude that high molecular hydrocarbons were biodegradable and transformed to low molecular weight PAHs under the sulfate-reducing condition. Since these PAHs are known to be biologically degraded under aerobic condition, a serial combination of anaerobic (sulfate reducing) and then aerobic bioremediations could be effective and useful for the soil pollution by petroleum and/or coal derived hydrocarbons.

A water balance approach to enhance national (GB) Daily Landslide Hazard Assessments

NASA Astrophysics Data System (ADS)

Dijkstra, Tom; Reeves, Helen; Freeborough, Katy; Dashwood, Claire; Pennington, Catherine; Jordan, Hannah; Hobbs, Peter; Richardson, Jennifer; Banks, Vanessa; Cole, Steven; Wells, Steven; Moore, Robert

2017-04-01

The British Geological Survey (BGS) is a member of the Natural Hazards Partnership (NHP) and delivers a national (GB) daily landslide hazard assessment (DLHA). The DLHA is based largely on 'expert' driven evaluations of the likelihood of landslides in response to antecedent ground conditions, adverse weather and reported landslide events. It concentrates on shallow translational slides and debris flows - events that most frequently have societal consequences by disrupting transport infrastructure and affecting buildings. Considerable experience with the issuing of DLHAs has been gained since 2012. However, it remains very difficult to appropriately assess changing ground conditions throughout GB even when good quality precipitation forecasts are available. Soil moisture sensors are available, but the network is sparse and not yet capable of covering GB to the detail required to underpin the forecasts. Therefore, we developed an approach where temporal and spatial variations in soil moisture can be obtained from a water balance model, representing processes in the near-surface and configured on a relatively coarse grid of 1 km2. Model outputs are not intended to be relevant to the slope scale. The assumption is that the likelihood of landslides being triggered by rainfall is dependent upon the soil moisture conditions of the near-surface, in combination with how much rain is forecast to occur for the following day. These variables form the basis for establishing thresholds to guide the issuing of DLHA and early warnings. The main aim is to obtain an insight into regional patterns of change and threshold exceedance. The BGS water balance model is still in its infancy and it requires substantial work to fine-tune and validate it. To test the performance of the BGS model we focused on an analysis of Scottish landslides (2004-2015) comprising translational slides and debris flows where the BGS model is conditionally evaluated against the Grid-to-Grid (G2G) Model. G2G is a physical-conceptual distributed hydrological model developed by the Centre for Ecology & Hydrology, also an NHP member. G2G is especially suited to simulate river flows over ungauged areas and has the capability to forecast fluvial river flows at any location across a gridded model domain. This is achieved by using spatial datasets on landscape properties - terrain, land-cover, soil and geology - in combination with gridded time-series of rainfall to shape a rainfall pattern into a river flow response over the model domain. G2G is operational on a 1 km2 grid over the GB and outputs soil moisture estimates that take some account of terrain slope in its water balance calculation. This research is part of an evolutionary process where capabilities of establishing the likelihood of landslides will develop as datasets are becoming increasingly detailed (and accessible) and the representation of hydrogeological and geotechnical processes continues to develop.

Forty years experience in developing and using rainfall simulators under tropical and Mediterranean conditions

NASA Astrophysics Data System (ADS)

Pla-Sentís, Ildefonso; Nacci, Silvana

2010-05-01

Rainfall simulation has been used as a practical tool for evaluating the interaction of falling water drops on the soil surface, to measure both stability of soil aggregates to drop impact and water infiltration rates. In both cases it is tried to simulate the effects of natural rainfall, which usually occurs at very different, variable and erratic rates and intensities. One of the main arguments against the use of rainfall simulators is the difficulty to reproduce the size, final velocity and kinetic energy of the drops in natural rainfall. Since the early 70´s we have been developing and using different kinds of rainfall simulators, both at laboratory and field levels, and under tropical and Mediterranean soil and climate conditions, in flat and sloping lands. They have been mainly used to evaluate the relative effects of different land use and management, including different cropping systems, tillage practices, surface soil conditioning, surface covers, etc. on soil water infiltration, on runoff and on erosion. Our experience is that in any case it is impossible to reproduce the variable size distribution and terminal velocity of raindrops, and the variable changes in intensity of natural storms, under a particular climate condition. In spite of this, with the use of rainfall simulators it is possible to obtain very good information, which if it is properly interpreted in relation to each particular condition (land and crop management, rainfall characteristics, measurement conditions, etc.) may be used as one of the parameters for deducing and modelling soil water balance and soil moisture regime under different land use and management and variable climate conditions. Due to the possibility for a better control of the intensity of simulated rainfall and of the size of water drops, and the possibility to make more repeated measurements under very variable soil and land conditions, both in the laboratory and specially in the field, the better results have been obtained with small size 500-1000 cm2, easily dismantled, drop former simulators, than with larger, nozzle, or more sophisticated equipments. In this contribution there are presented some of the rainfall simulators developed and used by the main author, and some of the results obtained in different studies of practical problems under tropical and Mediterranean conditions. References Pla, I.,G.Campero, y R.Useche.1974.Physical degradación of agricultural soils in the Western Plains of Venezuela. "Trans.10th Int.Cong.Soil.Sci.Soc". 1:231-240. .Moscú Pla, I. 1975.Effects of bitumen emulsion and polyacrilamide on some physical properties of Venezuelan soils. En "Soil Sci. Soc. Am. Special Publication"• 7. 35-46. Madison. Wisconsin . (USA). Pla, I. 1977.Aggregate size and erosion control on sloping land treated with hydrophobic bitumen emulsion."Soil Conservation and Management in the Humid Tropics".109-115. John Wiley & Sons. Pla, I.1981.Simuladores de lluvia para el estudio de relaciones suelo-agua bajo agricultura de secano en los trópicos. Rev. Fac. Agron. XII(1-2):81-93.Maracay (Venezuela) Pla, I. 1986.A routine laboratory index to predict the effects of soil sealing on soil and water conservation. En "Assesment of Soil Surface Sealing and Crusting". 154-162.State Univ. of Ghent.Gante (Bélgica Pla, I., M.C. Ramos, S. Nacci, F. Fonseca y X. Abreu. 2005. Soil moisture regime in dryland vineyards of Catalunya (Spain) as influenced by climate, soil and land management. "Integrated Soil and Water Management for Orchard Development". FAO Land and Water Bulletin 10. 41-49. Roma (Italia).

Estonian soil classification as a tool for recording information on soil cover and its matching with local site types, plant covers and humus forms classifications

NASA Astrophysics Data System (ADS)

Kõlli, Raimo; Tõnutare, Tõnu; Rannik, Kaire; Krebstein, Kadri

2015-04-01

Estonian soil classification (ESC) has been used successfully during more than half of century in soil survey, teaching of soil science, generalization of soil databases, arrangement of soils sustainable management and others. The Estonian normally developed (postlithogenic) mineral soils (form 72.4% from total area) are characterized by mean of genetic-functional schema, where the pedo-ecological position of soils (ie. location among other soils) is given by means of three scalars: (i) 8 stage lithic-genetic scalar (from rendzina to podzols) separates soils each from other by parent material, lithic properties, calcareousness, character of soil processes and others, (ii) 6 stage moisture and aeration conditions scalar (from aridic or well aerated to permanently wet or reductic conditions), and (iii) 2-3 stage soil development scalar, which characterizes the intensity of soil forming processes (accumulation of humus, podzolization). The organic soils pedo-ecological schema, which links with histic postlithogenic soils, is elaborated for characterizing of peatlands superficial mantle (form 23.7% from whole soil cover). The position each peat soil species among others on this organic (peat) soil matrix schema is determined by mean of 3 scalars: (i) peat thickness, (ii) type of paludification or peat forming peculiarities, and (iii) stage of peat decomposition or peat type. On the matrix of abnormally developed (synlithogenic) soils (all together 3.9%) the soil species are positioned (i) by proceeding in actual time geological processes as erosion, fluvial processes (at vicinity of rivers, lakes or sea) or transforming by anthropogenic and technological processes, and (ii) by 7 stage moisture conditions (from aridic to subaqual) of soils. The most important functions of soil cover are: (i) being a suitable environment for plant productivity; (ii) forming adequate conditions for decomposition, transformation and conversion of falling litter (characterized by humus cover type); (iii) being compartment for deposition of humus, individual organic compounds, plant nutrition elements, air and water, and (iv) forming (bio)chemically variegated active space for soil type specific edaphon. For studying of ESC matching with others ecosystem compartments classifications the comparative analysis of corresponding classification schemas was done. It may be concluded that forest and natural grasslands site types as well the plant associations of forests and grasslands correlate (match) well with ESC and therefore these compartments may be adequately expressed on soil cover matrixes. Special interest merits humus cover (in many countries known as humus form), which is by the issue natural body between plant and soil or plant cover and soil cover. The humus cover, which lied on superficial part of soil cover, has been formed by functional interrelationships of plants and soils, reflects very well the local pedo-ecological conditions (both productivity and decomposition cycles) and, therefore, the humus cover types are good indicators for characterizing of local pedo-ecological conditions. The classification of humus covers (humus forms) should be bound with soil classifications. It is important to develop a pedocentric approach in treating of fabric and functioning of natural and agro-ecosystems. Such, based on soil properties, ecosystem approach to management and protection natural resources is highly recommended at least in temperate climatic regions. The sound matching of soil and plant cover is of decisive importance for sustainable functioning of ecosystem and in attaining a good environmental status of the area.

Effect of addition of organic materials and irrigation conditions on soil quality in olive groves in the region of Messinia, Greece.

NASA Astrophysics Data System (ADS)

Kavvadias, Victor; Papadopoulou, Maria; Vavoulidou, Evangelia; Theocharopoulos, Sideris; Repas, Spiros; Koubouris, Georgos; Psaras, Georgios

2017-04-01

Intensive cultivation practices are associated to soil degradation mainly due to low soil organic matter content. The application of organic materials to land is a common practice in sustainable agriculture in the last years. However, its implementation in olive groves under different irrigation regimes has not been systematically tested under the prevailing Mediterranean conditions. The aim of this work was to study the effect of alternative carbon input techniques (i.e. wood shredded, pruning residues, returning of olive mill wastes the field with compost) and irrigation conditions (irrigated and rainfed olive orchards) on spatial distribution of soil chemical (pH, EC, total organic carbon, total nitrogen, inorganic nitrogen, humic and fulvic acids, available P, and exchangeable K) and microbial properties (soil basal microbial respiration and microbial biomass carbon) in two soil depths (0-10 cm and 10-40 cm). The study took place in the region of Messinia, South western Peloponnese, Greece during three year soil campaigns. Forty soil plots of olive groves were selected (20 rainfed and 20 irrigated) and carbon input practices were applied on the half of the irrigated and rainfed soil parcels (10 rainfed and 10 irrigated), while the remaining ones were used as controls. The results showed significant changes of chemical and biological properties of soil in olive orchards due to carbon treatments. However, these changes were depended on irrigation conditions. Microbial parameters appeared to be reliable indicators of changes in soil management. Proper management of alternative soil carbon inputs in olive orchards can positively affect soil fertility.

Habitat Fragmentation can Modulate Drought Effects on the Plant-soil-microbial System in Mediterranean Holm Oak (Quercus ilex) Forests.

PubMed

Flores-Rentería, Dulce; Curiel Yuste, Jorge; Rincón, Ana; Brearley, Francis Q; García-Gil, Juan Carlos; Valladares, Fernando

2015-05-01

Ecological transformations derived from habitat fragmentation have led to increased threats to above-ground biodiversity. However, the impacts of forest fragmentation on soils and their microbial communities are not well understood. We examined the effects of contrasting fragment sizes on the structure and functioning of soil microbial communities from holm oak forest patches in two bioclimatically different regions of Spain. We used a microcosm approach to simulate the annual summer drought cycle and first autumn rainfall (rewetting), evaluating the functional response of a plant-soil-microbial system. Forest fragment size had a significant effect on physicochemical characteristics and microbial functioning of soils, although the diversity and structure of microbial communities were not affected. The response of our plant-soil-microbial systems to drought was strongly modulated by the bioclimatic conditions and the fragment size from where the soils were obtained. Decreasing fragment size modulated the effects of drought by improving local environmental conditions with higher water and nutrient availability. However, this modulation was stronger for plant-soil-microbial systems built with soils from the northern region (colder and wetter) than for those built with soils from the southern region (warmer and drier) suggesting that the responsiveness of the soil-plant-microbial system to habitat fragmentation was strongly dependent on both the physicochemical characteristics of soils and the historical adaptation of soil microbial communities to specific bioclimatic conditions. This interaction challenges our understanding of future global change scenarios in Mediterranean ecosystems involving drier conditions and increased frequency of forest fragmentation.

PC-BASED SUPERCOMPUTING FOR UNCERTAINTY AND SENSITIVITY ANALYSIS OF MODELS

EPA Science Inventory

Evaluating uncertainty and sensitivity of multimedia environmental models that integrate assessments of air, soil, sediments, groundwater, and surface water is a difficult task. It can be an enormous undertaking even for simple, single-medium models (i.e. groundwater only) descr...

The soil sulphate effect and maize plant (Zea mays L.) growth of sulphate reducing bacteria (SRB) inoculation in acid sulfate soils with the different soil water condition

NASA Astrophysics Data System (ADS)

Asmarlaili, S.; Rauf, A.; Hanafiah, D. S.; Sudarno, Y.; Abdi, P.

2018-02-01

The objective of the study was to determine the potential application of sulphate reducing bacteria on acid sulfate soil with different water content in the green house. The research was carried out in the Laboratory and Green House, Faculty of Agriculture, Universitas Sumatera Utara. This research used Randomized Block Design with two treatments factors, ie sulphate reducing bacteria (SRB) isolate (control, LK4, LK6, TSM4, TSM3, AP4, AP3, LK4 + TSM3, LK4 + AP4, LK4 + AP3, LK6 + TSM3, LK6 + AP4, LK6 + AP3, TSM4 + TSM3, TSM4 + AP4, TSM4 + AP3) and water condition (100% field capacity and 110% field capacity). The results showed that application of isolate LK4 + AP4 with water condition 110% field capacity decreased the soil sulphate content (27.38 ppm) significantly after 6 weeks. Application of isolate LK4 + AP3 with water condition 110% field capacity increased soil pH (5.58) after-week efficacy 6. Application of isolate LK4 with water condition 110% field capacity increased plant growth (140 cm; 25.74 g) significantly after week 6. The best treatment was application isolate LK4 with water condition 110% field Capacity (SRB population 2.5x108; soil sulphate content 29.10ppm; soil acidity 4.78; plant height 140cm; plant weight 25.74g).

Warmer and drier conditions and nitrogen fertilizer application altered methanotroph abundance and methane emissions in a vegetable soil.

PubMed

Ran, Yu; Xie, Jianli; Xu, Xiaoya; Li, Yong; Liu, Yapeng; Zhang, Qichun; Li, Zheng; Xu, Jianming; Di, Hongjie

2017-01-01

Methane (CH 4 ) is a potent greenhouse gas, and soil can both be a source and sink for atmospheric CH 4 . It is not clear how future climate change may affect soil CH 4 emissions and related microbial communities. The aim of this study was to determine the interactive effects of a simulated warmer and drier climate scenarios and the application of different nitrogen (N) sources (urea and manure) on CH 4 emissions and related microbial community abundance in a vegetable soil. Greenhouses were used to control simulated climate conditions which gave 2.99 °C warmer and 6.2% lower water content conditions. The field experiment was divided into two phases. At the beginning of phase II, half of the greenhouses were removed to study possible legacy effects of the simulated warmer and drier conditions. The responses in methanogen and methanotroph abundance to a simulated climate change scenario were determined using real-time PCR. The results showed that the simulated warmer and drier conditions in the greenhouses significantly decreased CH 4 emissions largely due to the lower soil moisture content. For the same reason, CH 4 emissions of treatments in phase I were much lower than the same treatments in phase II. The abundance of methanotrophs showed a more significant response than methanogens to the simulated climate change scenario, increasing under simulated drier conditions. Methanogenic community abundance remained low, except where manure was applied which provided a source of organic C that stimulated methanogen growth. Soil moisture content was a major driver for methanotroph abundance and strongly affected CH 4 emissions. The application of N source decreased CH 4 emissions probably because of increased methanotrophic activity. CH 4 emissions were positively correlated to methanogenic abundance and negatively correlated to methanotrophic abundance. These results demonstrate that projected future climate change conditions can have a feedback impact on CH 4 emissions from the soil by altering soil conditions (particularly soil moisture) and related microbial communities.

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.

Contribution of calcium oxalate to soil-exchangeable calcium

USGS Publications Warehouse

Dauer, Jenny M.; Perakis, Steven S.

2013-01-01

Acid deposition and repeated biomass harvest have decreased soil calcium (Ca) availability in many temperate forests worldwide, yet existing methods for assessing available soil Ca do not fully characterize soil Ca forms. To account for discrepancies in ecosystem Ca budgets, it has been hypothesized that the highly insoluble biomineral Ca oxalate might represent an additional soil Ca pool that is not detected in standard measures of soil-exchangeable Ca. We asked whether several standard method extractants for soil-exchangeable Ca could also access Ca held in Ca oxalate crystals using spike recovery tests in both pure solutions and soil extractions. In solutions of the extractants ammonium chloride, ammonium acetate, and barium chloride, we observed 2% to 104% dissolution of Ca oxalate crystals, with dissolution increasing with both solution molarity and ionic potential of cation extractant. In spike recovery tests using a low-Ca soil, we estimate that 1 M ammonium acetate extraction dissolved sufficient Ca oxalate to contribute an additional 52% to standard measurements of soil-exchangeable Ca. However, in a high-Ca soil, the amount of Ca oxalate spike that would dissolve in 1 M ammonium acetate extraction was difficult to detect against the large pool of exchangeable Ca. We conclude that Ca oxalate can contribute substantially to standard estimates of soil-exchangeable Ca in acid forest soils with low soil-exchangeable Ca. Consequently, measures of exchangeable Ca are unlikely to fully resolve discrepancies in ecosystem Ca mass balance unless the contribution of Ca oxalate to exchangeable Ca is also assessed.

Analysis of the coexisting pathways for NO and N2O formation in Chernozem using the (15)N-tracer SimKIM-Advanced model.

PubMed

Stange, Claus Florian; Spott, Oliver; Russow, Rolf

2013-01-01

The nitrogen (N) cycle consists of a variety of microbial processes. These processes often occur simultaneously in soils, but respond differently to local environmental conditions due to process-specific biochemical restrictions (e.g. oxygen levels). Hence, soil nitrogen cycling (e.g. soil N gas production through nitrification and denitrification) is individually affected through these processes, resulting in the complex and highly dynamic behaviour of total soil N turnover. The development and application of methods that facilitate the quantification of individual contributions of coexisting processes is a fundamental prerequisite for (i) understanding the dynamics of soil N turnover and (ii) implementing these processes in ecosystem models. To explain the unexpected results of the triplet tracer experiment (TTE) of Russow et al. (Role of nitrite and nitric oxide in the processes of nitrification and denitrification in soil: results from (15)N tracer experiments. Soil Biol Biochem. 2009;41:785-795) the existing SimKIM model was extended to the SimKIM-Advanced model through the addition of three separate nitrite subpools associated with ammonia oxidation, oxidation of organic nitrogen (Norg), and denitrification, respectively. For the TTE, individual treatments with (15)N ammonium, (15)N nitrate, and (15)N nitrite were conducted under oxic, hypoxic, and anoxic conditions, respectively, to clarify the role of nitric oxide as a denitrification intermediate during N2O formation. Using a split nitrite pool, this analysis model explains the observed differences in the (15)N enrichments in nitric oxide (NO) and nitrous oxide (N2O) which occurred in dependence on different oxygen concentrations. The change from oxic over hypoxic to anoxic conditions only marginally increased the NO and N2O release rates (1.3-fold). The analysis using the model revealed that, under oxic and hypoxic conditions, Norg-based N2O production was the dominant pathway, contributing to 90 and 50 % of the total soil N2O release. Under anoxic conditions, denitrification was the dominant process for soil N2O release. The relative contribution of Norg to the total soil NO release was small. Ammonia oxidation served as the major pathway of soil NO release under oxic and hypoxic conditions, while denitrification was dominant under anoxic conditions. The model parameters for soil with moderate soil organic matter (SOM) content were not scalable to an additional data set for soil with higher SOM content, indicating a strong influence of SOM content on microbial N turnover. Thus, parameter estimation had to be re-calculated for these conditions, highlighting the necessity of individual soil-dependent parameter estimations.

An advanced process-based distributed model for the investigation of rainfall-induced landslides: The effect of process representation and boundary conditions

NASA Astrophysics Data System (ADS)

Anagnostopoulos, Grigorios G.; Fatichi, Simone; Burlando, Paolo

2015-09-01

Extreme rainfall events are the major driver of shallow landslide occurrences in mountainous and steep terrain regions around the world. Subsurface hydrology has a dominant role on the initiation of rainfall-induced shallow landslides, since changes in the soil water content affect significantly the soil shear strength. Rainfall infiltration produces an increase of soil water potential, which is followed by a rapid drop in apparent cohesion. Especially on steep slopes of shallow soils, this loss of shear strength can lead to failure even in unsaturated conditions before positive water pressures are developed. We present HYDROlisthisis, a process-based model, fully distributed in space with fine time resolution, in order to investigate the interactions between surface and subsurface hydrology and shallow landslides initiation. Fundamental elements of the approach are the dependence of shear strength on the three-dimensional (3-D) field of soil water potential, as well as the temporal evolution of soil water potential during the wetting and drying phases. Specifically, 3-D variably saturated flow conditions, including soil hydraulic hysteresis and preferential flow phenomena, are simulated for the subsurface flow, coupled with a surface runoff routine based on the kinematic wave approximation. The geotechnical component of the model is based on a multidimensional limit equilibrium analysis, which takes into account the basic principles of unsaturated soil mechanics. A series of numerical simulations were carried out with various boundary conditions and using different hydrological and geotechnical components. Boundary conditions in terms of distributed soil depth were generated using both empirical and process-based models. The effect of including preferential flow and soil hydraulic hysteresis was tested together with the replacement of the infinite slope assumption with the multidimensional limit equilibrium analysis. The results show that boundary conditions play a crucial role in the model performance and that the introduced hydrological (preferential flow and soil hydraulic hysteresis) and geotechnical components (multidimensional limit equilibrium analysis) significantly improve predictive capabilities in the presented case study.

Ecophysiological responses of young mangrove species Rhizophora apiculata (Blume) to different chromium contaminated environments.

PubMed

Nguyen, Kim Linh; Nguyen, Hoang Anh; Richter, Otto; Pham, Minh Thinh; Nguyen, Van Phuoc

2017-01-01

Many mangrove forests have suffered from the contaminated environments near industrial areas. This study addresses the question how these environments influence the renewal of mangrove forests. To this end ecophysiological responses of the young mangrove species Rhizophora apiculata (Blume) grown under combinations of the factors heavy metals (here chromium), nutrition and soil/water environment were analyzed. We tested the hypothesis that soil/water conditions and nutrient status of the soil strongly influence the toxic effect of chromium. Seedlings of R. apiculata were grown in three different soil/water environments (natural saline soil with brackish water, salt-leached soil with fresh water and salt-leached-sterilized soil with fresh water) treated with different levels of chromium and NPK fertilizer. The system was inundated twice a day as similar to natural tidal condition in the mangrove wetland in the south of Vietnam. The experiments were carried out for 6months. Growth data of root, leaf and stem, root cell number and stomata number were recorded and analyzed. Results showed that growth of R. apiculata is slower in natural saline soil/water condition. The effect of chromium and of nutrients respectively depends on the soil/water condition. Under high concentrations of chromium, NPK fertilizer amplifies the toxic effect of chromium. Stomata density increases under chromium stress and is largest under the combination of chromium and salty soil/water condition. From the data a nonlinear multivariate regression model was derived capturing the toxicity threshold of R. apiculata under different treatment combinations. Copyright © 2016 Elsevier B.V. All rights reserved.

Sensitivity of Polygonum aviculare Seeds to Light as Affected by Soil Moisture Conditions

PubMed Central

Batlla, Diego; Nicoletta, Marcelo; Benech-Arnold, Roberto

2007-01-01

Background and Aims It has been hypothesized that soil moisture conditions could affect the dormancy status of buried weed seeds, and, consequently, their sensitivity to light stimuli. In this study, an investigation is made of the effect of different soil moisture conditions during cold-induced dormancy loss on changes in the sensitivity of Polygonum aviculare seeds to light. Methods Seeds buried in pots were stored under different constant and fluctuating soil moisture environments at dormancy-releasing temperatures. Seeds were exhumed at regular intervals during storage and were exposed to different light treatments. Changes in the germination response of seeds to light treatments during storage under the different moisture environments were compared in order to determine the effect of soil moisture on the sensitivity to light of P. aviculare seeds. Key Results Seed acquisition of low-fluence responses during dormancy release was not affected by either soil moisture fluctuations or different constant soil moisture contents. On the contrary, different soil moisture environments affected seed acquisition of very low fluence responses and the capacity of seeds to germinate in the dark. Conclusions The results indicate that under field conditions, the sensitivity to light of buried weed seeds could be affected by the soil moisture environment experienced during the dormancy release season, and this could affect their emergence pattern. PMID:17430979

Seasonal-to-Interannual Variability and Land Surface Processes

NASA Technical Reports Server (NTRS)

Koster, Randal

2004-01-01

Atmospheric chaos severely limits the predictability of precipitation on subseasonal to interannual timescales. Hope for accurate long-term precipitation forecasts lies with simulating atmospheric response to components of the Earth system, such as the ocean, that can be predicted beyond a couple of weeks. Indeed, seasonal forecasts centers now rely heavily on forecasts of ocean circulation. Soil moisture, another slow component of the Earth system, is relatively ignored by the operational seasonal forecasting community. It is starting, however, to garner more attention. Soil moisture anomalies can persist for months. Because these anomalies can have a strong impact on evaporation and other surface energy fluxes, and because the atmosphere may respond consistently to anomalies in the surface fluxes, an accurate soil moisture initialization in a forecast system has the potential to provide additional forecast skill. This potential has motivated a number of atmospheric general circulation model (AGCM) studies of soil moisture and its contribution to variability in the climate system. Some of these studies even suggest that in continental midlatitudes during summer, oceanic impacts on precipitation are quite small relative to soil moisture impacts. The model results, though, are strongly model-dependent, with some models showing large impacts and others showing almost none at all. A validation of the model results with observations thus naturally suggests itself, but this is exceedingly difficult. The necessary contemporaneous soil moisture, evaporation, and precipitation measurements at the large scale are virtually non-existent, and even if they did exist, showing statistically that soil moisture affects rainfall would be difficult because the other direction of causality - wherein rainfall affects soil moisture - is unquestionably active and is almost certainly dominant. Nevertheless, joint analyses of observations and AGCM results do reveal some suggestions of land-atmosphere feedback in the observational record, suggestions that soil moisture can affect precipitation over seasonal timescales and across certain large continental areas. The strength of this observed feedback in nature is not large but is still significant enough to be potentially useful, e.g., for forecasts. This talk will address all of these issues. It will begin with a brief overview of land surface modeling in atmospheric models but will then focus on recent research - using both observations and models - into the impact of land surface processes on variability in the climate system.

Nitroglycerin degradation mediated by soil organic carbon under aerobic conditions.

PubMed

Bordeleau, Geneviève; Martel, Richard; Bamba, Abraham N'Valoua; Blais, Jean-François; Ampleman, Guy; Thiboutot, Sonia

2014-10-01

The presence of nitroglycerin (NG) has been reported in shallow soils and pore water of several military training ranges. In this context, NG concentrations can be reduced through various natural attenuation processes, but these have not been thoroughly documented. This study aimed at investigating the role of soil organic matter (SOM) in the natural attenuation of NG, under aerobic conditions typical of shallow soils. The role of SOM in NG degradation has already been documented under anoxic conditions, and was attributed to SOM-mediated electron transfer involving different reducing agents. However, unsaturated soils are usually well-oxygenated, and it was not clear whether SOM could participate in NG degradation under these conditions. Our results from batch- and column-type experiments clearly demonstrate that in presence of dissolved organic matter (DOM) leached from a natural soil, partial NG degradation can be achieved. In presence of particulate organic matter (POM) from the same soil, complete NG degradation was achieved. Furthermore, POM caused rapid sorption of NG, which should result in NG retention in the organic matter-rich shallow horizons of the soil profile, thus promoting degradation. Based on degradation products, the reaction pathway appears to be reductive, in spite of the aerobic conditions. The relatively rapid reaction rates suggest that this process could significantly participate in the natural attenuation of NG, both on military training ranges and in contaminated soil at production facilities. Copyright © 2014 Elsevier B.V. All rights reserved.

Interactive effects of compost and pre-planting soil moisture on plant biomass, nutrition and formation of mycorrhizas: a context dependent response.

PubMed

Ngo, H T T; Cavagnaro, T R

2018-01-24

We aimed to investigate the combined impacts of compost addition and pre-planting soil moisture conditions, on plant-available nutrients, and subsequent impacts on the biomass, nutrition and formation of AM by two important crop species. A glasshouse study was undertaken in which wheat and tomato plants were grown in compost amended or un-amended soil that was subjected to different moisture regimes prior to planting. The availability of P was strongly influenced by compost addition, but not pre-planting moisture conditions. In contrast, mineral N pools were affected by compost addition and pre-planting soil moisture conditions in complex ways. These changes in nutrient availability affected plant biomass, nutrient uptake and formation of AM. In general, plant performance was better where pre-planting soil moisture conditions were wet or dry, and worse where they involved a wet/dry cycle, and mycorrhizal colonisation was lower where compost was added to the soil. That pre-planting moisture conditions affect the biomass of subsequent crops is an important finding, the potential implications of which are considered here.

Sensitivity of convective precipitation to soil moisture and vegetation during break spell of Indian summer monsoon

NASA Astrophysics Data System (ADS)

Kutty, Govindan; Sandeep, S.; Vinodkumar; Nhaloor, Sreejith

2017-07-01

Indian summer monsoon rainfall is characterized by large intra-seasonal fluctuations in the form of active and break spells in rainfall. This study investigates the role of soil moisture and vegetation on 30-h precipitation forecasts during the break monsoon period using Weather Research and Forecast (WRF) model. The working hypothesis is that reduced rainfall, clear skies, and wet soil condition during the break monsoon period enhance land-atmosphere coupling over central India. Sensitivity experiments are conducted with modified initial soil moisture and vegetation. The results suggest that an increase in antecedent soil moisture would lead to an increase in precipitation, in general. The precipitation over the core monsoon region has increased by enhancing forest cover in the model simulations. Parameters such as Lifting Condensation Level, Level of Free Convection, and Convective Available Potential Energy indicate favorable atmospheric conditions for convection over forests, when wet soil conditions prevail. On spatial scales, the precipitation is more sensitive to soil moisture conditions over northeastern parts of India. Strong horizontal gradient in soil moisture and orographic uplift along the upslopes of Himalaya enhanced rainfall over the east of Indian subcontinent.

Effectiveness of T. harzianum and Humate Amendment in Soil Salinity Restoration

NASA Astrophysics Data System (ADS)

Apostolakis, Antonios; Daliakopoulos, Ioannis; Tsanis, Ioannis

2017-04-01

Soil salinity is a major soil degradation threat, especially for the water stressed parts of the Mediterranean region, where it hinders soil fertility and thus agricultural productivity. Soil salinity management can be complex and expensive, often resorting to the use of chemical amendments thus risking soil and aquifer pollution. This study quantifies the beneficial effects of (a) a commercial strain of the beneficial fungus Trichoderma harzianum (TH), and (b) a commercial humate fertilizer enhancer (HFE) approved for organic farming, against soil salinization. The treatments are tested in the context of a Solanum lycopersicum (tomato) greenhouse simulation of the cultivation conditions typical for the semi-arid coastal Timpaki basin in south-central Crete. 20 vigorous 20-day-old Solanum lycopersicum L. cv Elpida seedlings are treated either with TH or HFE, using soil substrates and irrigation treatments of two degradation states. 20 additional plants serve either as controls or guard rows. All plants are transplanted into 35 L pots under greenhouse conditions. Preliminary analysis of soil salinity and crop yield indicators suggest that both treatments are beneficial for the soil-plant system, each to a different extent depending on initial soil conditions.

Corrosion and Coatings Review of Specifications and Drawings of Facilities for the Oman Military Construction Program at Masirah Island, Oman.

DTIC Science & Technology

1984-12-01

5 Background Objective Approach Scope of Work Organization 2 SUMMARY OF ENVIRONMENTAL CONDITIONS AT MASIRAH ISLAND ................. 7 Soil ...CONDITIONS AT MASIRAH ISLAND Soil Resistivity Values for the soil resistivity at this location are not readily avail- able. It is, however, considered...to be a very aggressive soil with high amounts of chlorides and sulfates, which can be converted to corrosive sul- -. fides. Soil samples will be

An approach for using general soil physical condition-root growth relationships to predict seedling growth response to site preparation tillage in loblolly pine plantations

Treesearch

L.A. Morris; K.H. Ludovici; S.J. Torreano; E.A. Carter; M.C. Lincoln; R.E. Will

2006-01-01

Tree seedling root growth rate can be limited by any one of three soil physical factors: mechanical resistance, water potential or soil aeration. All three factors vary with soil water content and, under field conditions, root growth rate will depend on the soil water content as a result of its relationship to each factor. For a specific site, the relationship between...

Stress, deformation and micromorphological aspects of soil freezing under laboratory conditions

NASA Astrophysics Data System (ADS)

Jetchick, Elizabeth

In this thesis, frost heave is viewed as a process resulting from the interactions between thermodynamic conditions, soil environment controls such as texture, stress/deformation conditions and soil microstructure. A series of laboratory experiments was devised to investigate the links between these aspects. Because a limited number of studies exist on the development of internal stresses and strains in freezing soil, the work focussed on obtaining rheological data using conventional soil strain gauges and prototype stress transducers. A fine-grained unstructured silt was placed in a column (30 cm diameter by 100 cm length) and subjected to freezing and freeze-thaw cycles from the top down, lasting up to three months. Heat and water flows, as well as stresses and strains were monitored. The frozen soil was sectioned at the end of four of the experiments to examine the soil fabrics that had developed. From the experimental results, schematic stress and strain curves are proposed. For a single freeze cycle, compressive normal and tensile normal stresses were recorded simultaneously by the measuring devices within the freezing soil profile. Ice lens inception took place when the stress field changed, a condition which occurred either at the frost front level or at the base of the growing ice lens. Negative and positive strains reflected the different stress states that were sustained below and above the freezing front. Negative strains or soil consolidation took place as stresses increased before the passage of the frost line. Negligible soil strains were recorded as maximum soil consolidation was attained, before soil expansion. Distinct positive strain patterns indicating secondary and continuing heave, were recorded simultaneously throughout a thickness of soil, over a range of temperatures. Ice lens growth mostly took place as secondary frost heave, but continuing heave was measured, and the temperature conditions for both types of heave were determined. During subsequent freeze-thaw cycles, the stress patterns upon freezing were more complex in the second and third cycles due to previous soil structuration. At thaw, the stress pattern was uniform although positive strains in excess of those generated at freezing were recorded over the course of a few hours. Specific soil fabrics and features were evident from a single freeze cycle and for freeze-thaw conditions. Formation mechanisms are proposed for certain fabrics and features. A zonation with depth of these fabrics can be linked to the stress strain history of the soil, revealing the links and feedbacks between rheological processes and cryogenic soil structures.

Influence of Potassium on Sapric Peat under Different Environmental Conditions

NASA Astrophysics Data System (ADS)

Tajuddin, Syafik Akmal Mohd; Rahman, Junita Abdul; Rahim, Nor Haakmal Abd; Saphira Radin Mohamed, Radin Maya; Saeed Abduh Algheethi, Adel Ali, Dr

2018-04-01

Potassium is mainly present in soil in the natural form known as the K-bearing mineral. Potassium is also available in fertilizer as a supplement to plants and can be categorized as macronutrient. The application of potassium improves the texture and structure of the soil beside to improves plant growth. The main objective of this study was to determine the concentration of potassium in sapric peat under different conditions. Physical model was used as a mechanism for the analysis of the experimental data using a soil column as an equipment to produce water leaching. In this investigation, there were four outlets in the soil column which were prepared from the top of the column to the bottom with the purpose of identifying the concentration of potassium for each soil level. The water leaching of each outlet was tested using atomic absorption spectroscopy (AAS). The results obtained showed that the highest concentrations of potassium for flush condition at outlet 4 was 13.58 ppm. Similarly, sapric under rainwater condition recorded the highest value of 13.32 and 12.34 ppm respectively at outlet 4 for wet and dry condition. However, the difference in Sapric, rainwater and fertilizer category showed that the highest value for the wet condition was achieved at outlet 2 with 13.99 ppm while highest value of 14.82 ppm was obtained for the dry condition at the outlet 3. It was concluded that the outlets in the soil column gave a detailed analysis of the concentration of potassium in the soil which was influenced by the environmental conditions.

Insight into litter decomposition driven by nutrient demands of symbiosis system through the hypha bridge of arbuscular mycorrhizal fungi.

PubMed

Kong, Xiangshi; Jia, Yanyan; Song, Fuqiang; Tian, Kai; Lin, Hong; Bei, Zhanlin; Jia, Xiuqin; Yao, Bei; Guo, Peng; Tian, Xingjun

2018-02-01

Arbuscular mycorrhizal fungi (AMF) play an important role in litter decomposition. This study investigated how soil nutrient level affected the process. Results showed that AMF colonization had no significant effect on litter decomposition under normal soil nutrient conditions. However, litter decomposition was accelerated significantly under lower nutrient conditions. Soil microbial biomass in decomposition system was significantly increased. Especially, in moderate lower nutrient treatment (condition of half-normal soil nutrient), litters exhibited the highest decomposition rate, AMF hypha revealed the greatest density, and enzymes (especially nitrate reductase) showed the highest activities as well. Meanwhile, the immobilization of nitrogen (N) in the decomposing litter remarkably decreased. Our results suggested that the roles AMF played in ecosystem were largely affected by soil nutrient levels. At normal soil nutrient level, AMF exhibited limited effects in promoting decomposition. When soil nutrient level decreased, the promoting effect of AMF on litter decomposition began to appear, especially on N mobilization. However, under extremely low nutrient conditions, AMF showed less influence on decomposition and may even compete with decomposer microorganisms for nutrients.

Climate legacies drive global soil carbon stocks in terrestrial ecosystems

PubMed Central

Delgado-Baquerizo, Manuel; Eldridge, David J.; Maestre, Fernando T.; Karunaratne, Senani B.; Trivedi, Pankaj; Reich, Peter B.; Singh, Brajesh K.

2017-01-01

Climatic conditions shift gradually over millennia, altering the rates at which carbon (C) is fixed from the atmosphere and stored in the soil. However, legacy impacts of past climates on current soil C stocks are poorly understood. We used data from more than 5000 terrestrial sites from three global and regional data sets to identify the relative importance of current and past (Last Glacial Maximum and mid-Holocene) climatic conditions in regulating soil C stocks in natural and agricultural areas. Paleoclimate always explained a greater amount of the variance in soil C stocks than current climate at regional and global scales. Our results indicate that climatic legacies help determine global soil C stocks in terrestrial ecosystems where agriculture is highly dependent on current climatic conditions. Our findings emphasize the importance of considering how climate legacies influence soil C content, allowing us to improve quantitative predictions of global C stocks under different climatic scenarios. PMID:28439540

A new approach for remediation of As-contaminated soil: ball mill-based technique.

PubMed

Shin, Yeon-Jun; Park, Sang-Min; Yoo, Jong-Chan; Jeon, Chil-Sung; Lee, Seung-Woo; Baek, Kitae

2016-02-01

In this study, a physical ball mill process instead of chemical extraction using toxic chemical agents was applied to remove arsenic (As) from contaminated soil. A statistical analysis was carried out to establish the optimal conditions for ball mill processing. As a result of the statistical analysis, approximately 70% of As was removed from the soil at the following conditions: 5 min, 1.0 cm, 10 rpm, and 5% of operating time, media size, rotational velocity, and soil loading conditions, respectively. A significant amount of As remained in the grinded fine soil after ball mill processing while more than 90% of soil has the original properties to be reused or recycled. As a result, the ball mill process could remove the metals bound strongly to the surface of soil by the surface grinding, which could be applied as a pretreatment before application of chemical extraction to reduce the load.

Pyrogenic Carbon in forest soils across climate and soil property gradients in Switzerland

NASA Astrophysics Data System (ADS)

Reisser, Moritz; González Domínguez, Beatriz R.; Hagedorn, Frank; Abiven, Samuel

2016-04-01

Soil organic carbon (SOC) is an important measure for soil quality. Usually a high organic matter content in soils is favourable for most ecosystems. As a very stable component, pyrogenic organic carbon (PyC) can be of major interest to investigate to potential of organic matter, to persist very long in soils. Recent studies have shown, that the mean residence time of organic matter is not only due to its intrinsic chemical nature, but also to a variety of abiotic and biotic variables set by the ecosystem. Especially for PyC it is unclear, whether its content is related to fire regime, soil properties or other climatic conditions. In this study we wanted to investigate, how climatic and soil-related conditions are influencing the persistence of PyC in soils. Therefore we used a sample set from Swiss forest soil (n = 54), which was designed for the purpose of having most differing climatic conditions (aridity and temperature) and a large range of soil properties (pH between 3.4 and 7.6; clay content between 4.7 % and 60 %). The soils were sampled in the first 20 cm of the mineral horizon on a representative plot area of 40 x 40 m. The soils were sieved to 2 mm and dried prior to the analysis. We used the benzene polycarboxylic acids (BPCA) molecular marker method to quantify and characterize PyC in these soil samples. Despite the large span in environmental conditions, we observed rather small differences in the contribution of PyC to SOC between warmer and colder, as well as between wetter and dryer soils. The PyC content in SOC lies well in range with a global average for forest soils estimated in other studies. Stocks of PyC vary more than the content, because of the large range of SOC contents in the samples. The influence of other parameters like soil properties is still under investigation. Qualitative investigation of the BPCAs showed that the degree of condensation, defined by the relative amount of B6CA in the total BPCA, was higher in warmer soils. This might be explained by the fact that warmer conditions favour decomposition of organic matter and leave a higher relative amount of the most condensed and therefore also stable molecules.

Natural abiotic formation of oxalic acid in soils: results from aromatic model compounds and soil samples.

PubMed

Studenroth, Sabine; Huber, Stefan G; Kotte, Karsten; Schöler, Heinz F

2013-02-05

Oxalic acid is the smallest dicarboxylic acid and plays an important role in soil processes (e.g., mineral weathering and metal detoxification in plants). We have first proven its abiotic formation in soils and investigated natural abiotic degradation processes based on the oxidation of soil organic matter, enhanced by Fe(3+) and H(2)O(2) as hydroxyl radical suppliers. Experiments with the model compound catechol and further hydroxylated benzenes were performed to examine a common degradation pathway and to presume a general formation mechanism of oxalic acid. Two soil samples were tested for the release of oxalic acid and the potential effects of various soil parameters on oxalic acid formation. Additionally, the soil samples were treated with different soil sterilization methods to prove the oxalic acid formation under abiotic soil conditions. Different series of model experiments were conducted to determine a range of factors including Fe(3+), H(2)O(2), reaction time, pH, and chloride concentration on oxalic acid formation. Under certain conditions, catechol is degraded up to 65.6% to oxalic acid referring to carbon. In serial experiments with two soil samples, oxalic acid was produced, and the obtained results are suggestive of an abiotic degradation process. In conclusion, Fenton-like conditions with low Fe(3+) concentrations and an excess of H(2)O(2) as well as acidic conditions were required for an optimal oxalic acid formation. The presence of chloride reduced oxalic acid formation.

Mercury critical concentrations to Enchytraeus crypticus (Annelida: Oligochaeta) under normal and extreme conditions of moisture in tropical soils - Reproduction and survival.

PubMed

Buch, Andressa Cristhy; Schmelz, Rüdiger M; Niva, Cintia Carla; Correia, Maria Elizabeth Fernandes; Silva-Filho, Emmanoel Vieira

2017-05-01

Soil provides many ecosystem services that are essential to maintain its quality and healthy development of the flora, fauna and human well-being. Environmental mercury levels may harm the survival and diversity of the soil fauna. In this respect, efforts have been made to establish limit values of mercury (Hg) in soils to terrestrial fauna. Soil organisms such as earthworms and enchytraeids have intimate contact with trace metals in soil by their oral and dermal routes, reflecting the potentially adverse effects of this contaminant. The main goal of this study was to obtain Hg critical concentrations under normal and extreme conditions of moisture in tropical soils to Enchytraeus crypticus to order to assess if climate change may potentiate their acute and chronic toxicity effects. Tropical soils were sampled from of two Forest Conservation Units of the Rio de Janeiro State - Brazil, which has been contaminated by Hg atmospheric depositions. Worms were exposed to three moisture conditions, at 20%, 50% and 80% of water holding capacity, respectively, and in combination with different Hg (HgCl 2 ) concentrations spiked in three types of tropical soil (two natural soils and one artificial soil). The tested concentrations ranged from 0 to 512mg Hg kg -1 dry weight. Results indicate that the Hg toxicity is higher under increased conditions of moisture, significantly affecting survival and reproduction rate. Copyright © 2017 Elsevier Inc. All rights reserved.

Local adaptation in migrated interior Douglas-fir seedlings is mediated by ectomycorrhizas and other soil factors.

PubMed

Pickles, Brian J; Twieg, Brendan D; O'Neill, Gregory A; Mohn, William W; Simard, Suzanne W

2015-08-01

Separating edaphic impacts on tree distributions from those of climate and geography is notoriously difficult. Aboveground and belowground factors play important roles, and determining their relative contribution to tree success will greatly assist in refining predictive models and forestry strategies in a changing climate. In a common glasshouse, seedlings of interior Douglas-fir (Pseudotsuga menziesii var. glauca) from multiple populations were grown in multiple forest soils. Fungicide was applied to half of the seedlings to separate soil fungal and nonfungal impacts on seedling performance. Soils of varying geographic and climatic distance from seed origin were compared, using a transfer function approach. Seedling height and biomass were optimized following seed transfer into drier soils, whereas survival was optimized when elevation transfer was minimised. Fungicide application reduced ectomycorrhizal root colonization by c. 50%, with treated seedlings exhibiting greater survival but reduced biomass. Local adaptation of Douglas-fir populations to soils was mediated by soil fungi to some extent in 56% of soil origin by response variable combinations. Mediation by edaphic factors in general occurred in 81% of combinations. Soil biota, hitherto unaccounted for in climate models, interacts with biogeography to influence plant ranges in a changing climate. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

Adsorption and desorption characteristics of endosulfan in two typical agricultural soils in Southwest China.

PubMed

Qian, Sheng; Zhu, Heng; Xiong, Bailian; Zheng, Guocan; Zhang, Jinzhong; Xu, Weihong

2017-04-01

Endosulfan is an organochlorine pesticide widely used in Southwest China. In this paper, the adsorption and desorption characteristics of endosulfan in two typical agricultural soils (latosol and lateritic red soil) in this area were studied. The results showed that Langmuir isothermal equation could well describe the adsorption thermodynamic characteristics of endosulfan in latosol and lateritic red soil, and the maximum adsorption capacities of α-endosulfan were 0.186 and 0.209 mg/g, while those of β-endosulfan were 0.140 and 0.148 mg/g, respectively. Endosulfan adsorption in the two soils was an exothermic physicochemical process, but dominated by physical process. The adsorption kinetic characteristics of endosulfan in the two soils could be well described by second-order kinetic equation, and the initial rate constants were 0.228 and 0.325 mg/(g min) for α-endosulfan, while those were 0.119 and 0.125 mg/(g min) for β-endosulfan, respectively. The adsorbed endosulfan in the two soils was difficult to be desorbed into the liquid phase, and showed weak desorption hysteresis. These results implied that endosulfan could be firmly adsorbed by the two soils, and their adsorption and desorption abilities may be related to the contents of soil clay and organic matter.

Ground penetrating radar for underground sensing in agriculture: a review

NASA Astrophysics Data System (ADS)

Liu, Xiuwei; Dong, Xuejun; Leskovar, Daniel I.

2016-10-01

Belowground properties strongly affect agricultural productivity. Traditional methods for quantifying belowground properties are destructive, labor-intensive and pointbased. Ground penetrating radar can provide non-invasive, areal, and repeatable underground measurements. This article reviews the application of ground penetrating radar for soil and root measurements and discusses potential approaches to overcome challenges facing ground penetrating radar-based sensing in agriculture, especially for soil physical characteristics and crop root measurements. Though advanced data-analysis has been developed for ground penetrating radar-based sensing of soil moisture and soil clay content in civil engineering and geosciences, it has not been used widely in agricultural research. Also, past studies using ground penetrating radar in root research have been focused mainly on coarse root measurement. Currently, it is difficult to measure individual crop roots directly using ground penetrating radar, but it is possible to sense root cohorts within a soil volume grid as a functional constituent modifying bulk soil dielectric permittivity. Alternatively, ground penetrating radarbased sensing of soil water content, soil nutrition and texture can be utilized to inversely estimate root development by coupling soil water flow modeling with the seasonality of plant root growth patterns. Further benefits of ground penetrating radar applications in agriculture rely on the knowledge, discovery, and integration among differing disciplines adapted to research in agricultural management.

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.

Physiological characteristics of tropical rain forest tree species: A basis for the development of silvicultural technology

PubMed Central

SASAKI, Satohiko

2008-01-01

The physiological characteristics of the dominant tree species in the tropical rain forest mainly belonging to dipterocarps as well as the environmental conditions especially for the light in the forest were studied to establish the silvicultural system for the forest regeneration in the tropical South Asia. The flowering patterns of the dipterocarp trees are usually irregular and unpredictable, which make difficult to collect sufficient seeds for raising the seedlings. The field survey revealed the diverged features of the so-called gregarious or simultaneous flowering of various species of this group. Appropriate conditions and methods for the storage of the seeds were established according to the detailed analyses of the morphological and physiological characteristics of the seeds such as the low temperature tolerance and the moisture contents. The intensity and spectra of the light in the forest primarily determine the growth and the morphological development of the seedlings under the canopy. Based on the measurements of the diffused light at the sites in the tropical forest in the varying sunlight, the parameters such as “the steady state of the diffuse light” and “the turning point” were defined, which were useful to evaluate the light conditions in the forest. To improve the survival of the transplanted seedlings, a planting method of “the bare-root seedlings”, the seedlings easy to be handled by removal of all leaves, soil and pots, was developed. Its marked efficiency was proved with various dipterocarps and other tropical trees by the field trial in the practical scale. Tolerance of the various species to the extreme environmental conditions such as fires, acid soils and drought were examined by the experiments and the field survey, which revealed marked adaptability of Shorea roxburghii as a potential species for regeneration of the tropical forests. PMID:18941286

Assessment of soil toxicity from an antitank firing range using Lumbricus terrestris and Eisenia andrei in mesocosms and laboratory studies.

PubMed

Robidoux, Pierre Yves; Dubois, Charles; Hawari, Jalal; Sunahara, Geoffrey I

2004-08-01

Earthworm mesocosms studies were carried out on a explosives-contaminated site at an antitank firing range. Survival of earthworms and the lysosomal neutral red retention time (NRRT), a biomarker of lysosomal membrane stability, were used in these studies to assess the effect of explosives-contaminated soils on the earthworms Lumbricus terrestris and Eisenia andrei under field conditions. Toxicity of the soils samples for E. andrei was also assessed under laboratory conditions using the earthworms reproduction test and the NRRT. Results indicate that the survival was reduced up to 40% in certain explosive-contaminated soil mesocosms following 10 days of exposure under field conditions, whereas survival was reduced up to 100% following 28 days of exposure under laboratory conditions. Reproduction parameters such as number of cocoons and number of juveniles were reduced in many of the selected contaminated soils. Compared to the reference, NRRT was significantly reduced for E. andrei exposed to explosive-contaminated soils under both field and laboratory conditions, whereas for L. terrestris NRRT was similar compared to the reference mesocosm. Analyses showed that HMX was the major polynitro-organic compound in soils. HMX was also the only explosive detected in earthworm tissues. Thus, results from both field mesocosms and laboratory studies, showed lethal and sub-lethal effects associated to soil from the contaminated area of the antitank firing range.

Quantification of mitigation potentials of agricultural practices for Europe

NASA Astrophysics Data System (ADS)

Lesschen, J. P.; Kuikman, P. J.; Smith, P.; Schils, R. L.; Oudendag, D.

2009-04-01

Agriculture has a significant impact on climate, with a commonly estimated contribution of 9% of total greenhouse gases (GHG) emissions. Besides, agriculture is the main source of nitrous oxide and methane emissions to the atmosphere. On the other hand, there is a large potential for climate change mitigation in agriculture through carbon sequestration into soils. Within the framework of the PICCMAT project (Policy Incentives for Climate Change Mitigation Agricultural Techniques) we quantified the mitigation potential of 11 agricultural practices at regional level for the EU. The focus was on smaller-scale measures towards optimised land management that can be widely applied at individual farm level and which can have a positive climate change mitigating effect and be beneficial to soil conditions, e.g. cover crops and reduced tillage. The mitigation potentials were assessed with the MITERRA-Europe model, a deterministic and static N cycling model which calculates N emissions on an annual basis, using N emission factors and N leaching fractions. For the PICCMAT project the model was extended with a soil carbon module, to assess changes in soil organic carbon according to the IPCC Tier1 approach. The amount of soil organic carbon (SOC) is calculated by multiplying the soil reference carbon content, which depends on soil type and climate, by coefficients for land use, land management and input of organic matter. By adapting these coefficients changes in SOC as result of the measures were simulated. We considered both the extent of agricultural area across Europe on which a measure could realistically be applied (potential level of implementation), and the current level of implementation that has already been achieved . The results showed that zero tillage has the highest mitigation potential, followed by adding legumes, reduced tillage, residue management, rotation species, and catch crops. Optimising fertiliser application and fertiliser type are the measures with the largest positive effect on N2O emissions. Overall the results showed that the additional mitigation potential of each individual measure is limited, but taken together they have a significant mitigation potential of about 10 percent of the current GHG emissions from agriculture. Besides, most of the measures with high mitigation potentials are associated with no or low implementation costs. Although CH4 and N2O are the most important GHG emitted from agricultural activities, it is more difficult to mitigate these emissions than increasing soil organic carbon (SOC) stocks and thus compensate them through carbon sequestration. However, the effect on carbon is only temporary and sequestered SOC stocks can easily be lost again, while for N2O the emission reduction is permanent and non-saturating. Another important implication that follows from our results is the large regional difference with regard to mitigation potential and feasibility of implementation. Policy measures to support agricultural mitigation should therefore be adjusted to regional conditions.

Modeling soil heating and moisture transport under extreme conditions: Forest fires and slash pile burns

NASA Astrophysics Data System (ADS)

Massman, W. J.

2012-10-01

Heating any soil during a sufficiently intense wildfire or prescribed burn can alter it irreversibly, causing many significant, long-term biological, chemical, and hydrological effects. Given the climate-change-driven increasing probability of wildfires and the increasing use of prescribed burns by land managers, it is important to better understand the dynamics of the coupled heat and moisture transport in soil during these extreme heating events. Furthermore, improved understanding and modeling of heat and mass transport during extreme conditions should provide insights into the associated transport mechanisms under more normal conditions. The present study describes a numerical model developed to simulate soil heat and moisture transport during fires where the surface heating often ranges between 10,000 and 100,000 W m-2 for several minutes to several hours. Basically, the model extends methods commonly used to model coupled heat flow and moisture evaporation at ambient conditions into regions of extreme dryness and heat. But it also incorporates some infrequently used formulations for temperature dependencies of the soil specific heat, thermal conductivity, and the water retention curve, as well as advective effects due to the large changes in volume that occur when liquid water is rapidly volatilized. Model performance is tested against laboratory measurements of soil temperature and moisture changes at several depths during controlled heating events. Qualitatively, the model agrees with the laboratory observations, namely, it simulates an increase in soil moisture ahead of the drying front (due to the condensation of evaporated soil water at the front) and a hiatus in the soil temperature rise during the strongly evaporative stage of the soil drying. Nevertheless, it is shown that the model is incapable of producing a physically realistic solution because it does not (and, in fact, cannot) represent the relationship between soil water potential and soil moisture at extremely low soil moisture contents (i.e., residual or bound water: θ < 0.01 m3 m-3, for example). Diagnosing the model's performance yields important insights into how to make progress on modeling soil evaporation and heating under conditions of high temperatures and very low soil moisture content.

Current status, uncertainty and future needs in soil organic carbon monitoring.

PubMed

Jandl, Robert; Rodeghiero, Mirco; Martinez, Cristina; Cotrufo, M Francesca; Bampa, Francesca; van Wesemael, Bas; Harrison, Robert B; Guerrini, Iraê Amaral; Richter, Daniel Deb; Rustad, Lindsey; Lorenz, Klaus; Chabbi, Abad; Miglietta, Franco

2014-01-15

Increasing human demands on soil-derived ecosystem services requires reliable data on global soil resources for sustainable development. The soil organic carbon (SOC) pool is a key indicator of soil quality as it affects essential biological, chemical and physical soil functions such as nutrient cycling, pesticide and water retention, and soil structure maintenance. However, information on the SOC pool, and its temporal and spatial dynamics is unbalanced. Even in well-studied regions with a pronounced interest in environmental issues information on soil carbon (C) is inconsistent. Several activities for the compilation of global soil C data are under way. However, different approaches for soil sampling and chemical analyses make even regional comparisons highly uncertain. Often, the procedures used so far have not allowed the reliable estimation of the total SOC pool, partly because the available knowledge is focused on not clearly defined upper soil horizons and the contribution of subsoil to SOC stocks has been less considered. Even more difficult is quantifying SOC pool changes over time. SOC consists of variable amounts of labile and recalcitrant molecules of plant, and microbial and animal origin that are often operationally defined. A comprehensively active soil expert community needs to agree on protocols of soil surveying and lab procedures towards reliable SOC pool estimates. Already established long-term ecological research sites, where SOC changes are quantified and the underlying mechanisms are investigated, are potentially the backbones for regional, national, and international SOC monitoring programs. © 2013.

Persistence and dioxin-like toxicity of carbazole and chlorocarbazoles in soil.

PubMed

Mumbo, John; Henkelmann, Bernhard; Abdelaziz, Ahmed; Pfister, Gerd; Nguyen, Nghia; Schroll, Reiner; Munch, Jean Charles; Schramm, Karl-Werner

2015-01-01

Halogenated carbazoles have recently been detected in soil and water samples, but their environmental effects and fate are unknown. Eighty-four soil samples obtained from a site with no recorded history of pollution were used to assess the persistence and dioxin-like toxicity of carbazole and chlorocarbazoles in soil under controlled conditions for 15 months. Soil samples were divided into two temperature conditions, 15 and 20 °C, both under fluctuating soil moisture conditions comprising 19 and 44 drying-rewetting cycles, respectively. This was characterized by natural water loss by evaporation and rewetting to -15 kPa. Accelerated solvent extraction (ASE) and cleanup were performed after incubation. Identification and quantification were done using high-resolution gas chromatogram/mass spectrometer (HRGC/MS), while dioxin-like toxicity was determined by ethoxyresorufin-O-deethylase (EROD) induction in H4IIA rat hepatoma cells assay and multidimensional quantitative structure-activity relationships (mQSAR) modelling. Carbazole, 3-chlorocarbazole and 3,6-dichlorocarbazole were detected including trichlorocarbazole not previously reported in soils. Carbazole and 3-chlorocarbazole showed significant dissipation at 15 °C but not at 20 °C incubating conditions indicating that low temperature could be suitable for dissipation of carbazole and chlorocarbazoles. 3,6-Dichlorocarbazole was resistant at both conditions. Trichlorocarbazole however exhibited a tendency to increase in concentration with time. 3-Chlorocarbazole, 3,6-dibromocarbazole and selected soil extracts exhibited EROD activity. Dioxin-like toxicity did not decrease significantly with time, whereas the sum chlorocarbazole toxic equivalence concentrations (∑TEQ) did not contribute significantly to the soil assay dioxin-like toxicity equivalent concentrations (TCDD-EQ). Carbazole and chlorocarbazoles are persistent with the latter also toxic in natural conditions.

Soils of mountainous forest-steppe in the southwestern part of Khentei Ridge (Mongolia)

NASA Astrophysics Data System (ADS)

Ubugunova, V. I.; Baldanov, B. Ts.; Gunin, P. D.; Bazha, S. N.

2017-09-01

The study of soil cover in the mountainous forest-steppe on the southwestern macroslope of Khentei Ridge has shown that the spatial distribution of soils is controlled by the ruggedness of topography, slope aspects, geocryological conditions, and the thickness of loose deposits. The soils belong to the orders of lithozems and organo-accumulative soils (Mollic Leptosols) of the postlithogenic trunk of pedogenesis. Dark-humus and mucky-dark-humus horizons of the organic matter accumulation are characteristic features of these soils. The investigated area is differentiated according to the soil moistening conditions on the slopes of different aspects. Favorable growth conditions for dwarf birch and Siberian larch at the southern boundary of the boreal forests in Mongolia are explained by the relatively high moistening of mucky-darkhumus lithozems and mucky-dark-humus soils developed on windward northern slopes and on mountain terraces in places of the local snow accumulation by wind. An important role in preservation of forest vegetation belongs to permafrost in small cirque-like depressions.

Pupal development of Ceratitis capitata (Diptera: Tephritidae) and Diachasmimorpha longicaudata (Hymenoptera: Braconidae) at different moisture values in four soil types.

PubMed

Bento, F de M M; Marques, R N; Costa, M L Z; Walder, J M M; Silva, A P; Parra, J R P

2010-08-01

This study aimed to evaluate adult emergence and duration of the pupal stage of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), and emergence of the fruit fly parasitoid, Diachasmimorpha longicaudata (Ashmead), under different moisture conditions in four soil types, using soil water matric potential. Pupal stage duration in C. capitata was influenced differently for males and females. In females, only soil type affected pupal stage duration, which was longer in a clay soil. In males, pupal stage duration was individually influenced by moisture and soil type, with a reduction in pupal stage duration in a heavy clay soil and in a sandy clay, with longer duration in the clay soil. As matric potential decreased, duration of the pupal stage of C. capitata males increased, regardless of soil type. C. capitata emergence was affected by moisture, regardless of soil type, and was higher in drier soils. The emergence of D. longicaudata adults was individually influenced by soil type and moisture factors, and the number of emerged D. longicaudata adults was three times higher in sandy loam and lower in a heavy clay soil. Always, the number of emerged adults was higher at higher moisture conditions. C. capitata and D. longicaudata pupal development was affected by moisture and soil type, which may facilitate pest sampling and allow release areas for the parasitoid to be defined under field conditions.

Flood effects on efflux and net production of nitrous oxide in river floodplain soils

NASA Astrophysics Data System (ADS)

Riaz, Muhammad; Bruderer, Christian; Niklaus, Pascal A.; Luster, Jörg

2016-04-01

Floodplain soils are often rich in nutrients and exhibit high spatial heterogeneity in terms of geomorphology, soil environmental conditions and substrate availability for processes involved in carbon and nutrient cycling. In addition, fluctuating water tables lead to temporally changing redox conditions. In such systems, there are ideal conditions for the occurrence of hot spots and moments of nitrous oxide emissions, a potent greenhouse gas. The factors that govern the spatial heterogeneity and dynamics of N2O formation in floodplain soils and the surface efflux of this gas are not fully understood. A particular issue is the contribution of N2O formation in the subsoil to surface efflux. We studied this question in the floodplain of a restored section of the Thur river (NE Switzerland) which is characterized by a flashy flow regime. As a consequence, the floodplain soils are unsaturated most of the time. We showed earlier that saturation during flood pulses leads to short phases of generally anoxic conditions followed by a drying phase with anoxic conditions within aggregates and oxic conditions in larger soil pores. The latter conditions are conducive for spatially closely-coupled nitrification-denitrification and related hot moments of nitrous oxide formation. In a floodplain zone characterized by about one meter of young, sandy sediments, that are mostly covered by the tall grass Phalaris arundinacea, we measured at several time points before and after a small flood event N2O surface efflux with the closed-chamber method, and assessed N2O concentrations in the soil air at four different depths using gas-permeable tubings. In addition, we calculated the N2O diffusivity in the soil from Radon diffusivity. The latter was estimated in-situ from the recovery of Radon concentration in the gas-permeable tubings after purging with ambient air. All these data were then used to calculate net N2O production rates at different soil depths with the gradient method. In addition, temperature, volumetric water content, as well as ammonium, nitrate and dissolved organic carbon in the soil solution were monitored at different depths in the observation plots. During not flood-affected conditions we observed weak diffusive gradients between subsoil and top soil, and net N2O production was maximum in the top soil. During the drying phase after a flood, diffusive gradients between subsoil and topsoil were more pronounced, and net N2O production in the subsoil increased. At all conditions, N2O efflux was more strongly correlated with N2O concentrations in the subsoil than those in the top soil. The complex interactions between soil moisture on one hand, and C and N substrate limitation on the other hand in determining N2O production at different soil depths will be discussed. Finally, the results will be put into the context of our earlier and ongoing studies that aim at elucidating the governing factors of spatial heterogeneity and dynamics of N2O emissions in floodplain soils.

About soil cover heterogeneity of agricultural research stations' experimental fields

NASA Astrophysics Data System (ADS)

Rannik, Kaire; Kõlli, Raimo; Kukk, Liia

2013-04-01

Depending on local pedo-ecological conditions (topography, (geo) diversity of soil parent material, meteorological conditions) the patterns of soil cover and plant cover determined by soils are very diverse. Formed in the course of soil-plant mutual relationship, the natural ecosystems are always influenced to certain extent by the other local soil forming conditions or they are site specific. The agricultural land use or the formation of agro-ecosystems depends foremost on the suitability of soils for the cultivation of feed and food crops. As a rule, the most fertile or the best soils of the area, which do not present any or present as little as possible constraints for agricultural land use, are selected for this purpose. Compared with conventional field soils, the requirements for the experimental fields' soil cover quality are much higher. Experimental area soils and soil cover composition should correspond to local pedo-ecological conditions and, in addition to that, represent the soil types dominating in the region, whereas the fields should be as homogeneous as possible. The soil cover heterogeneity of seven arable land blocks of three research stations (Jõgeva, Kuusiku and Olustvere) was studied 1) by examining the large scale (1:10 000) digital soil map (available via the internet), and 2) by field researches using the transect method. The stages of soils litho-genetic and moisture heterogeneities were estimated by using the Estonian normal soils matrix, however, the heterogeneity of top- and subsoil texture by using the soil texture matrix. The quality and variability of experimental fields' soils humus status, was studied more thoroughly from the aspect of humus concentration (g kg-1), humus cover thickness (cm) and humus stocks (Mg ha-1). The soil cover of Jõgeva experimental area, which presents an accumulative drumlin landscape (formed during the last glacial period), consist from loamy Luvisols and associated to this Cambisols. In Kuusiku area, which landscape is characterized by till and limestone plains with thin Quaternary cover, the soil cover is more heterogeneous than in previous area. Kuusiku soil cover is more variegated by the soil texture and as well as by the genesis of soils. In addition to Cambisols, Leptosols, Gleysols and Luvisols may be found here as well. The dominating soils in Olustvere research area, which is situated on wavy upland plateau, are Albeluvisols.

A Portable, Low-Power Analyzer and Automated Soil Flux Chamber System for Measuring Wetland GHG Emissions

NASA Astrophysics Data System (ADS)

Nickerson, Nick; Kim-Hak, David; McArthur, Gordon

2017-04-01

Preservation and restoration of wetlands has the potential to help sequester large amounts of carbon due to the naturally high primary productivity and slow turnover of stored soil carbon. However, the anoxic environmental conditions present in wetland soils are also the largest natural contributor to global methane emissions. While it is well known that wetlands are net carbon sinks over long time scales, given the high global warming potential of methane, the short-term balances between C uptake and storage and loss as CO2 and CH4 need to be carefully considered when evaluating the climate effects of land-use change. It is relatively difficult to measure methane emissions from wetlands with currently available techniques given the temporally and spatially sporadic nature of the processes involved (methanogenesis, methane oxidation, ebullition, etc.). For example, using manual soil flux chambers can often only capture a portion of either the spatial or temporal variability, and often have other disadvantages associated with soil atmosphere disturbance during deployment in these relatively compressible wetland soils. Automated chamber systems offer the advantage of collecting high-resolution time series of gaseous fluxes while reducing some human and method induced biases. Additionally, new laser-based analyzers that can be used in situ alongside automated chambers offer a greater minimum detectable flux than can be achieved using alternative methods such as Gas Chromatography. Until recently these types of automated measurements were limited to areas that had good power coverage, as laser based systems were power intensive and could not easily be supplemented with power from field-available sources such as solar. Recent advances in laser technology has reduced the power needed and made these systems less power intensive and more field portable in the process. Here we present data using an automated chamber system coupled to a portable laser based greenhouse gas analyzer (Picarro G4301). We will present on the methodological and field deployment benefits of the system with a strong emphasis on the enhanced minimum detectable flux limits offered by this fully automated design. These advantages will be demonstrated through two deployments of the system in wetland and peatland ecosystems in Nova Scotia, Canada.

Late Triassic tropical climate of Pangea: Carbon isotopic and other insights into the rise of dinosaurs

NASA Astrophysics Data System (ADS)

Whiteside, J. H.; Lindström, S.; Irmis, R. B.; Glasspool, I.; Schaller, M. F.; Dunlavey, M.; Nesbitt, S. J.; Smith, N. D.; Turner, A. H.

2015-12-01

The rarity and species-poor nature of early dinosaurs and their relatives at low paleolatitudes persisted for 30 million years after their origin and 10-15 million years after they became abundant and speciose at higher latitudes. New environmental reconstructions from stable carbon isotope ratios of preserved organic matter (δ13Corg), atmospheric pCO2 data based on the δ13C of soil carbonate, palynological, and wildfire data from charcoal from early dinosaur-bearing strata at low paleolatitudes in western North America show that variations in δ13Corg and palynomorph ecotypes are tightly correlated, displaying large and high-frequency excursions. These variations occurred within an environment characterized by elevated and increasing atmospheric pCO2, pervasive wildfires, and rapidly fluctuating extreme climatic conditions. Whereas pseudosuchian archosaur-dominated communities were able to persist in these same regions until the end-Triassic, the large-bodied, fast-growing tachymetabolic dinosaurian herbivores were not. We hypothesize that the greater resources required by the herbivores made it difficult from them to adapt to the unstable conditions at low paleolatitudes in the Late Triassic.

Effect of soil conditions on predicted ground motion: Case study from Western Anatolia, Turkey

NASA Astrophysics Data System (ADS)

Gok, Elcin; Chávez-García, Francisco J.; Polat, Orhan

2014-04-01

We present a site effect study for the city of Izmir, Western Anatolia, Turkey. Local amplification was evaluated using state-of-practice tools. Ten earthquakes recorded at 16 sites were analysed using spectral ratios relative to a reference site, horizontal-to-vertical spectral ratios, and an inversion scheme of the Fourier amplitude spectra of the recorded S-waves. Seismic noise records were also used to estimate site effects. The different estimates are in good agreement among them, although a basic uncertainty of a factor of 2 seems difficult to decrease. We used our site effect estimates to predict ground motion in Izmir for a possible M6.5 earthquake close to the city using stochastic modelling. Site effects have a large impact on PSV (pseudospectral velocity), where local amplification increases amplitudes by almost a factor of 9 at 1 Hz relative to the firm ground condition. Our results allow identifying the neighbourhoods of Izmir where hazard mitigation measurements are a priority task and will also be useful for planning urban development.

2008 Volunteer Potato Outlook

USDA-ARS?s Scientific Manuscript database

Potato tubers left in the ground following a potato harvest often over winter in regions with mild winter temperatures resulting in a serious and difficult to manage weed problem in the ensuing crop rotation. Potatoes normally are killed when they reach temperatures below 28° F. Winter soil tempera...

Field Scale Monitoring and Modeling of Water and Chemical Transfer in the Vadose Zone

USDA-ARS?s Scientific Manuscript database

Natural resource systems involve highly complex interactions of soil-plant-atmosphere-management components that are extremely difficult to quantitatively describe. Computer simulations for prediction and management of watersheds, water supply areas, and agricultural fields and farms have become inc...

Evaluation of different field methods for measuring soil water infiltration

NASA Astrophysics Data System (ADS)

Pla-Sentís, Ildefonso; Fonseca, Francisco

2010-05-01

Soil infiltrability, together with rainfall characteristics, is the most important hydrological parameter for the evaluation and diagnosis of the soil water balance and soil moisture regime. Those balances and regimes are the main regulating factors of the on site water supply to plants and other soil organisms and of other important processes like runoff, surface and mass erosion, drainage, etc, affecting sedimentation, flooding, soil and water pollution, water supply for different purposes (population, agriculture, industries, hydroelectricity), etc. Therefore the direct measurement of water infiltration rates or its indirect deduction from other soil characteristics or properties has become indispensable for the evaluation and modelling of the previously mentioned processes. Indirect deductions from other soil characteristics measured under laboratory conditions in the same soils, or in other soils, through the so called "pedo-transfer" functions, have demonstrated to be of limited value in most of the cases. Direct "in situ" field evaluations have to be preferred in any case. In this contribution we present the results of past experiences in the measurement of soil water infiltration rates in many different soils and land conditions, and their use for deducing soil water balances under variable climates. There are also presented and discussed recent results obtained in comparing different methods, using double and single ring infiltrometers, rainfall simulators, and disc permeameters, of different sizes, in soils with very contrasting surface and profile characteristics and conditions, including stony soils and very sloping lands. It is concluded that there are not methods universally applicable to any soil and land condition, and that in many cases the results are significantly influenced by the way we use a particular method or instrument, and by the alterations in the soil conditions by the land management, but also due to the manipulation of the surface soil before and during the measurement. Due to the commonly found high variability, natural or induced by land management, of the soil surface and subsurface hydrological properties, and to the limitations imposed by the requirements of water for the measurements, there is proposed a simple and handy method, which do not use high volumes of water, adaptable to very different soil and land conditions, and that allow many repeated measurements with acceptable accuracy for most of the purposes. References Pla, I., 1997. A soil water balance model for monitoring soil erosion processes and effects on steep lands in the tropics. Soil Technology. 11(1):17-30. Elsevier Pla, I., 2006. Hydrological approach for assessing desertification processes in the Mediterranean region. In W.G. Kepner et al. (Editors), Desertification in the Mediterranean Region. A Security Issue. 579-600 Springer. Heidelberg (Germany) Reynolds W.D., B.T. Bowman, R.R. Brunke, C.F. Drury and C.S. Tan. 2000. Comparison of Tension Infiltrometer, Pressure Infiltrometer, and Soil Core Estimates of Saturated Hydraulic Conductivity . Soil Science Society of America Journal 64:478-484 Segal, E., S.A.Bradford, P. Shouse; N. Lazarovich, and D. Corwin. 2008. Integration of Hard and Soft Data to Characterize Field-Scale Hydraulic Properties for Flow and Transport Studies. Vadose Zone J 7:878-889 Young, E. 1991. Infiltration measurements, a review. Hydrological processes 5: 309-320.

Soils conditioned by native vegetation and by the exotic invasive annual grass Bromus tectorum: do a native perennial and two exotic grasses sense the substrates similarly

USDA-ARS?s Scientific Manuscript database

Invasion by the exotic annual grass Bromus tectorum often increases soil nutrient availability. It is unclear, however, if other grasses benefit from this higher nutrient status. Soil from three sites in the northern Great Basin U.S.A. conditioned by B. tectoruminvasion (BTCS=B. tectorum conditioned...

Effect of management and soil moisture regimes on wetland soils total carbon and nitrogen in Tanzania

NASA Astrophysics Data System (ADS)

Kamiri, Hellen; Kreye, Christine; Becker, Mathias

2013-04-01

Wetland soils play an important role as storage compartments for water, carbon and nutrients. These soils implies various conditions, depending on the water regimes that affect several important microbial and physical-chemical processes which in turn influence the transformation of organic and inorganic components of nitrogen, carbon, soil acidity and other nutrients. Particularly, soil carbon and nitrogen play an important role in determining the productivity of a soil whereas management practices could determine the rate and magnitude of nutrient turnover. A study was carried out in a floodplain wetland planted with rice in North-west Tanzania- East Africa to determine the effects of different management practices and soil water regimes on paddy soil organic carbon and nitrogen. Four management treatments were compared: (i) control (non weeded plots); (ii) weeded plots; (iii) N fertilized plots, and (iv) non-cropped (non weeded plots). Two soil moisture regimes included soil under field capacity (rainfed conditions) and continuous water logging compared side-by-side. Soil were sampled at the start and end of the rice cropping seasons from the two fields differentiated by moisture regimes during the wet season 2012. The soils differed in the total organic carbon and nitrogen between the treatments. Soil management including weeding and fertilization is seen to affect soil carbon and nitrogen regardless of the soil moisture conditions. Particularly, the padddy soils were higher in the total organic carbon under continuous water logged field. These findings are preliminary and a more complete understanding of the relationships between management and soil moisture on the temporal changes of soil properties is required before making informed decisions on future wetland soil carbon and nitrogen dynamics. Keywords: Management, nitrogen, paddy soil, total carbon, Tanzania,