These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

A model for soil-vegetation-atmosphere interactions in water-limited ecosystems  

E-print Network

it reaches a wet and cool state when starting from higher initial values of soil moisture and of vegetationA model for soil-vegetation-atmosphere interactions in water-limited ecosystems M. Baudena,1,2 F. D; published 20 December 2008. [1] We study the interaction between atmosphere, soil moisture, and vegetation

D'Andrea, Fabio

2

Modeling the Effect of Vegetation on Passive Microwave Remote Sensing of Soil Moisture  

NASA Technical Reports Server (NTRS)

The effect of vegetation on passive microwave remote sensing of soil moisture is studied. The radiative transfer modeling work of Njoku and Kong is applied to a stratified medium of which the upper layer is treated as a layer of vegetation. An effective dielectric constant for this vegetation layer is computed using estimates of the dielectric constant of individual components of the vegetation layer. The horizontally-polarized brightness temperature is then computed as a function of the incidence angle. Model predictions are used to compare with the data obtained in the Huntsville '96, remote sensing of soil moisture experiment, and with predictions obtained using a correction procedure of Jackson and Schmugge.

Liu, Y. P.; Inguva, R.; Crosson, W. L.; Coleman, T. L.; Laymon, C.; Fahsi, A.

1998-01-01

3

Measuring and modelling water related soil-vegetation feedbacks in a fallow plot  

NASA Astrophysics Data System (ADS)

Land fallowing is one possible response to shortage of water for irrigation. Leaving the soil unseeded implies a change of the soil functioning that has an impact on the water cycle. The development of a soil crust in the open spaces between the patterns of grass weed affects the soil properties and the field scale water balance. The objectives of this study are to test the potential of integrated non invasive geophysical methods and ground-image analysis and to quantify the effect of the soil vegetation interaction on the water balance of a fallow land at the local and plot scale. We measured repeatedly in space and time local soil saturation and vegetation cover over two small plots located in southern Sardinia, Italy, during a controlled irrigation experiment. One plot was left unseeded and the other was cultivated. The comparative analysis of ERT maps of soil moisture evidenced a considerably different hydrologic response to irrigation of the two plots. Local measurements of soil saturation and vegetation cover were repeated in space to evidence a positive feedback between weed growth and infiltration at the fallow plot. A simple bucket model captured the different soil moisture dynamics at the two plots during the infiltration experiment and was used to estimate the impact of the soil vegetation feedback on the yearly water balance at the fallow site.

Ursino, N.; Cassiani, G.; Deiana, R.; Vignoli, G.; Boaga, J.

2013-08-01

4

Soil dynamics and accelerated erosion: a sensitivity analysis of the LPJ Dynamic vegetation model  

NASA Astrophysics Data System (ADS)

It is widely accepted that humans have become a major geomorphic force by disturbing natural vegetation patterns. Land conversion for agriculture purposes removes the protection of soils by the natural vegetation and leads to increased soil erosion by one to two orders of magnitude, breaking the balance that exists between the loss of soils and its production. Accelerated erosion and deposition have a strong influence on evolution and heterogeneity of basic soil characteristics (soil thickness, hydrology, horizon development,…) as well as on organic matter storage and cycling. Yet, since they are operating at a long time scale, those processes are not represented in state-of-art Dynamic Global Vegetation Models, which is a clear lack when exploring vegetation dynamics over past centuries. The main objectives of this paper are (i) to test the sensitivity of a Dynamic Global Vegetation Model, in terms of NPP and organic matter turnover, variations in state variables in response to accelerated erosion and (ii) to assess the performance of the model under the impact of erosion for a case-study in Central Spain. We evaluated the Lund-Postdam-Jena Dynamic Vegetation Model (LPJ DVGM) (Sitch et al, 2003) which simulates vegetation growth and carbon pools at the surface and in the soil based on climatic, pedologic and topographic variables. We assessed its reactions to changes in key soil properties that are affected by erosion such as texture and soil depth. We present the results of where we manipulated soil texture and bulk density while keeping the environmental drivers of climate, slope and altitude constant. For parameters exhibiting a strong control on NPP or SOM, a factorial analysis was conducted to test for interaction effects. The simulations show an important dependence on the clay content, especially for the slow cycling carbon pools and the biomass production, though the underground litter seems to be mostly influenced by the silt content. The fast cycling C pools and/or the surface pools vary with sand and silt richness, the highest values being reached with a combination of 50% silt and 25% sand while the lowest are for a 100% clay soil. Finally, LPJ is run for three cases corresponding to a stable, erosive and depositional soil profile. These simulations show how the model reacts and performs under erosion/deposition conditions which are recreated by changing the soil's texture and soil depth over time. We discuss the performance of the LPJ model in the context of accelerated erosion and conclusions drawn from the sensitivity analysis.

Bouchoms, Samuel; Van Oost, Kristof; Vanacker, Veerle; Kaplan, Jed O.; Vanwalleghem, Tom

2013-04-01

5

Evaluating Climate, Vegetation, and Soil Controls on Groundwater Recharge Using Unsaturated Flow Modeling  

NASA Astrophysics Data System (ADS)

Understanding the relative importance of climate, vegetation, and soils in controlling groundwater recharge is critical for estimating recharge rates and for assessing the importance of these factors in controlling aquifer vulnerability to contamination. Understanding the role of climate and vegetation in controlling recharge will also be valuable in determining impacts of climate change and land use change on recharge. Numerical modeling is a valuable tool for assessing controls on recharge and for developing a predictive understanding of recharge processes. Unsaturated flow modeling was used to simulate recharge for a range of climate (arid - humid), vegetation (shrub, grass, forest, crops), and soils (fine - coarse grained, monolithic - layered) using data from Texas. Data from 10 meteorological stations in the state provided long-term (30 yr) climate forcing ranging from arid to humid conditions. Spatial distribution of dominant vegetation associations provided by the USGS was used to assign vegetation parameters using GIS and including fractional vegetation coverage, leaf area index, root depth, and root length density. Varying levels of soils data were used in the simulations ranging from simple monolithic sand profiles to complex layered soil profiles from the SSURGO database and pedotransfer functions were used to translate soils data to hydraulic parameters for the simulations. The effect of climate was evaluated using monolithic sand profiles without vegetation. Recharge rates varied from 54 mm/yr in arid west Texas to 720 mm/yr in humid east Texas, correlating positively with precipitation (R=0.99, slope = 0.69). These recharge rates represent 24 to 61 percent of long-term average precipitation. High potential recharge rates in monolithic sand profiles indicate that climate is not the limiting factor controlling recharge and that vegetation and soil texture are important in reducing recharge. Addition of vegetation to the monolithic sand profiles reduced recharge rates for most cases by factors ranging from 2 to 11. Soil profile layering reduced recharge rates in most cases relative to recharge rates based on monolithic sand profiles by factors ranging from 2 to 10. Recharge estimates based on nonvegetated, layered soil profiles were quite variable locally depending on soil texture and sequence of layers. However, aerially weighted average recharge rates for the counties analyzed in this study were much less variable and were positively correlated with precipitation (R=0.79; slope = 0.19). The final simulations included vegetation and layered soil profiles and resulted in recharge rates ranging from 0 to 328 mm/yr which represent reductions from potential recharge by factors ranging from 6 to 380. Unsaturated flow modeling proved to be a useful tool in evaluating the effects of climate, soil, and vegetation on recharge because these factors could be isolated in different simulations. Modeling results indicate that long-term average precipitation can be used as a predictor of recharge, but is not the limiting factor; vegetation and soil texture are important in reducing recharge. The results of this study have important implications for estimating recharge and indicate that the role of vegetation and soil texture in reducing recharge could significantly impact aquifer vulnerability to contamination.

Keese, K. E.; Scanlon, B. R.; Reedy, R. C.

2003-12-01

6

Measuring and Modelling water related soil - vegetation feedbacks in a fallow plot  

NASA Astrophysics Data System (ADS)

Land fallowing is one possible response to shortage of water for irrigation. Leaving the soil unseeded implies a change of the soil functioning that has an impact on the water cycle. The development of a soil crust in the open spaces between the patterns of grass weed affects the soil properties and the field scale water balance. The objective of this study was to test the potential of integrated non invasive geophysics and ground-image analysis and to quantify the effect of the soil vegetation interaction on the water balance of a fallow land at the local and plot scale. We measured repeatedly in space and time local soil saturation and vegetation cover over two small plots located in southern Sardinia, Italy, during an infiltration experiment. One plot was left unseeded and the other was cultivated. The comparative analysis of the experimental data evidenced a positive feedback between weed growth and infiltration at the fallow plot. A simple bucket model captured the different soil moisture dynamics at the two plots during the infiltration experiment and was used to estimate the impact of the soil vegetation feedback on the yearly water balance at the site.

Ursino, Nadia; Cassiani, Giorgio; Deiana, Rita; Vignoli, Giulio; Boaga, Jacopo

2013-04-01

7

Modeling carbon dynamics in vegetation and soil under the impact of soil erosion and deposition  

USGS Publications Warehouse

Soil erosion and deposition may play important roles in balancing the global atmospheric carbon budget through their impacts on the net exchange of carbon between terrestrial ecosystem and the atmosphere. Few models and studies have been designed to assess these impacts. In this study, we developed a general ecosystem model, Erosion-Deposition-Carbon-Model (EDCM), to dynamically simulate the influences of rainfall-induced soil erosion and deposition on soil organic carbon (SOC) dynamics in soil profiles. EDCM was applied to several landscape positions in the Nelson Farm watershed in Mississippi, including ridge top (without erosion or deposition), eroding hillslopes, and depositional sites that had been converted from native forests to croplands in 1870. Erosion reduced the SOC storage at the eroding sites and deposition increased the SOC storage at the depositional areas compared with the site without erosion or deposition. Results indicated that soils were consistently carbon sources to the atmosphere at all landscape positions from 1870 to 1950, with lowest source strength at the eroding sites (13 to 24 gC m-2 yr-1), intermediate at the ridge top (34 gC m-2 yr-1), and highest at the depositional sites (42 to 49 gC m-2 yr-1). During this period, erosion reduced carbon emissions via dynamically replacing surface soil with subsurface soil that had lower SOC contents (quantity change) and higher passive SOC fractions (quality change). Soils at all landscape positions became carbon sinks from 1950 to 1997 due to changes in management practices (e.g., intensification of fertilization and crop genetic improvement). The sink strengths were highest at the eroding sites (42 to 44 gC m-2 yr-1 , intermediate at the ridge top (35 gC m-2 yr-1), and lowest at the depositional sites (26 to 29 gC m-2 yr-1). During this period, erosion enhanced carbon uptake at the eroding sites by continuously taking away a fraction of SOC that can be replenished with enhanced plant residue input. Overall, soil erosion and deposition reduced CO2 emissions from the soil into the atmosphere by exposing low carbon-bearing soil at eroding sites and by burying SOC at depositional sites. The results suggest that failing to account for the impact of soil erosion and deposition may potentially contribute to an overestimation of both the total historical carbon released from soils owing to land use change and the contemporary carbon sequestration rates at the eroding sites.

Liu, S.; Bliss, N.; Sundquist, E.; Huntington, T.G.

2003-01-01

8

Vegetation and soils  

USGS Publications Warehouse

Intro paragraph: Characterization of bottomland hardwood vegetation in relatively undisturbed forests can provide critical information for developing effective wetland creation and restoration techniques and for assessing the impacts of management and development. Classification is a useful technique in characterizing vegetation because it summarizes complex data sets, assists in hypothesis generation about factors influencing community variation, and helps refine models of community structure. Hierarchical classification of communities is particularly useful for showing relationships among samples (Gauche 1982).

Burke, M.K.; King, S.L.; Eisenbies, M.H.; Gartner, D.

2000-01-01

9

A climate sensitive model of carbon transfer through atmosphere, vegetation and soil in managed forest ecosystems  

NASA Astrophysics Data System (ADS)

For predicting the future of the forest carbon cycle in forest ecosystems, it is necessary to account for both the climate and management impacts. Climate effects are significant not only at a short time scale but also at the temporal horizon of a forest life cycle e.g. through shift in atmospheric CO2 concentration, temperature and precipitation regimes induced by the enhanced greenhouse effect. Intensification of forest management concerns an increasing fraction of temperate and tropical forests and untouched forests represents only one third of the present forest area. Predicting tools are therefore needed to project climate and management impacts over the forest life cycle and understand the consequence of management on the forest ecosystem carbon cycle. This communication summarizes the structure, main components and properties of a carbon transfer model that describes the processes controlling the carbon cycle of managed forest ecosystems. The model, GO+, links three main components, (i) a module describing the vegetation-atmosphere mass and energy exchanges in 3D, (ii) a plant growth module and a (iii) soil carbon dynamics module in a consistent carbon scheme of transfer from atmosphere back into the atmosphere. It was calibrated and evaluated using observed data collected on coniferous and broadleaved forest stands. The model predicts the soil, water and energy balance of entire rotations of managed stands from the plantation to the final cut and according to a range of management alternatives. It accounts for the main soil and vegetation management operations such as soil preparation, understorey removal, thinnings and clearcutting. Including the available knowledge on the climatic sensitivity of biophysical and biogeochemical processes involved in atmospheric exchanges and carbon cycle of forest ecosystems, GO+ can produce long-term backward or forward simulations of forest carbon and water cycles under a range of climate and management scenarios. This model applications to the prediction and analysis of climate scenarios impacts on southwestern European forests underlines the role of management alternatives, precipitation regime, CO2 concentration and atmospheric humidity .Frequency of soil preparation operations and understorey management play a major role in controlling the net carbon flux into the atmosphere at the juvenile stage ( 0 to 10 y-old) whereas climate and rotation duration control the functioning of adult phase. The model predicts that a drier and warmer climate will reduce the forest productivity and deplete soil and carbon stocks in managed forest from Southwestern Europe within decades, such effects being amplified for most intensive management alternatives. This work was part of the European research project GHG-Europe (EU contract No. 244122) and the French national project FAST co-funded by the Ecology, Agriculture and Forestry Ministries and the Region Aquitaine.

Loustau, D.; Moreaux, V.; Bosc, A.; Trichet, P.; Kumari, J.; Rabemanantsoa, T.; Balesdent, J.; Jolivet, C.; Medlyn, B. E.; Cavaignac, S.; Nguyen-The, N.

2012-12-01

10

Evaluating Climate, Vegetation, and Soil Controls on Groundwater Recharge Using Unsaturated Flow Modeling  

Microsoft Academic Search

Understanding the relative importance of climate, vegetation, and soils in controlling groundwater recharge is critical for estimating recharge rates and for assessing the importance of these factors in controlling aquifer vulnerability to contamination. Understanding the role of climate and vegetation in controlling recharge will also be valuable in determining impacts of climate change and land use change on recharge. Numerical

K. E. Keese; B. R. Scanlon; R. C. Reedy

2003-01-01

11

Soil erosion modelled with USLE and PESERA using QuickBird derived vegetation parameters in an alpine catchment  

NASA Astrophysics Data System (ADS)

The focus of soil erosion research in the Alps has been in two categories: (i) on-site measurements, which are rather small scale point measurements on selected plots often constrained to irrigation experiments or (ii) off-site quantification of sediment delivery at the outlet of the catchment. Results of both categories pointed towards the importance of an intact vegetation cover to prevent soil loss. With the recent availability of high-resolution satellites such as IKONOS and QuickBird options for detecting and monitoring vegetation parameters in heterogeneous terrain have increased. The aim of this study is to evaluate the usefulness of QuickBird derived vegetation parameters in soil erosion models for alpine sites by comparison to Cesium-137 (Cs-137) derived soil erosion estimates. The study site (67 km 2) is located in the Central Swiss Alps (Urseren Valley) and is characterised by scarce forest cover and strong anthropogenic influences due to grassland farming for centuries. A fractional vegetation cover (FVC) map for grassland and detailed land-cover maps are available from linear spectral unmixing and supervised classification of QuickBird imagery. The maps were introduced to the Pan-European Soil Erosion Risk Assessment (PESERA) model as well as to the Universal Soil Loss Equation (USLE). Regarding the latter model, the FVC was indirectly incorporated by adapting the C factor. Both models show an increase in absolute soil erosion values when FVC is considered. In contrast to USLE and the Cs-137 soil erosion rates, PESERA estimates are low. For the USLE model also the spatial patterns improved and showed "hotspots" of high erosion of up to 16 t ha -1 a -1. In conclusion field measurements of Cs-137 confirmed the improvement of soil erosion estimates using the satellite-derived vegetation data.

Meusburger, K.; Konz, N.; Schaub, M.; Alewell, C.

2010-06-01

12

[Advance in researches on vegetation cover and management factor in the soil erosion prediction model].  

PubMed

Vegetation cover and land management are the main limiting factors of soil erosion, and quantitative evaluation on the effect of different vegetation on soil erosion is essential to land use and soil conservation planning. The vegetation cover and management factor (C) in the universal soil loss equation (USLE) is an index to evaluate this effect, which has been studied deeply and used widely. However, the C factor study is insufficient in China. In order to strengthen the research of C factor, this paper reviewed the developing progress of C factor, and compared the methods of estimating C value in different USLE versions. The relative studies in China were also summarized from the aspects of vegetation canopy coverage, soil surface cover, and root density. Three problems in C factor study were pointed out. The authors suggested that cropland C factor research should be furthered, and its methodology should be unified in China to represent reliable C values for soil loss prediction and conservation planning. PMID:12418270

Zhang, Yan; Yuan, Jianping; Liu, Baoyuan

2002-08-01

13

Vegetation and soil respiration: Correlations and controls  

Microsoft Academic Search

Soil respiration rates vary significantly among major plant biomes, suggesting that vegetation type influences the rate of soil respiration. However, correlations among climatic factors, vegetation distributions, and soil respiration rates make cause-effect arguments difficult. Vegetation may affect soil respiration by influencing soil microclimate and structure, the quantity of detritus supplied to the soil, the quality of that detritus, and the

James W. Raich; Aydin Tufekciogul

2000-01-01

14

Impact of improved atmospheric forcing data and soil-vegetation parameters in terrestrial hydrologic modeling over West Africa  

NASA Astrophysics Data System (ADS)

Several recent studies have shown the importance of land surface-atmosphere coupling in the monsoon system of the West Africa. The African Monsoon Multidisciplinary Analysis (AMMA) has provided an opportunity to investigate model deficiencies in land surface processes by providing high-resolution datasets. In participation with the AMMA Land Surface Model Intercomparison Project (ALMIP2), a global land surface model, the Minimal Advanced Treatments of Surface Interaction and Runoff (MATSIRO), is regionalized for conducting a high space-time resolution experiment (0.05°, 30 minutes). Multi-year offline simulations using improved rainfall datasets derived from local rain gauges and radar-based products are compared with relative coarse resolution satellite precipitation products, such as Tropical Rainfall Measuring Mission (TRMM; 0.25°, 3 hourly) and Global Satellite Mapping of Precipitation (GSMaP; 0.1°, hourly) to better understand the effect of precipitation on simulated hydrological responses. Sensitivity experiments are also conducted by incorporating more refined distributions of soil-vegetation parameters accounting for natural grid variability to identify how soil properties and interannual vegetation variability are significantly related to water and energy balances in West Africa. Further examination of individual soil parameter and vegetation type is also performed to identify their proper specification in land surface parameterization schemes. Simulations of surface fluxes, soil temperature and soil moisture in dry months and wet months are verified separately by using observations from the AMMA-CATCH observing system as well as several satellite-based products. In general, this study demonstrates that improved forcing and representation of soil-vegetation parameters can improve land surface model simulations from seasonal to interannual time scale.

HE, X.; Kim, H.; Yeh, P. J.; Oki, T.

2012-12-01

15

Floodplain restoration leads to wetter and more diverse soil water regimes and vegetation types: Insight from an integrated hydroecological model  

NASA Astrophysics Data System (ADS)

Soil moisture availability in the root zone is one of the most important factors affecting plant species composition by creating stress on vegetation both when it is lacking (water stress) and when it is excessive (oxygen stress). Plant species have individual tolerance ranges along a gradient of available soil moisture that can be described as a hydrological niche. Combining a hydrological model and a habitat niche model can provide spatially-extensive predictions of vegetation composition, which would be useful for land management decision-making under changing environmental conditions. Floodplain ecosystem restoration provides an example of the utility of such a predictive tool as a site is hydrologically altered to create a wetter environment. We developed an integrated hydroecological model that links a quasi-3D, variably-saturated, groundwater flow model that simulates soil moisture with several plant habitat niche models. The focus of this research is a floodplain in southwestern Wisconsin where post-settlement alluvium was removed with the expectation of increasing regionally-threatened wetland plant species. Hydrological niche models were created based on simultaneous observations of vegetation composition and surface effective saturation. These models were then used to predict probability of presence for two dominant plant species (Carex vulpinoidea and Elymus canadensis) and composite wetland indicator score based on simulated surface effective saturation across the study site. The model predicts the site to be more wetland-species dominant overall following restoration. However, the soil moisture regime and vegetation types are slightly drier following restoration in zones where a silt-clay confining layer is present that inhibits vertical groundwater flow from a basal gravel aquifer to the near-surface soil zone. This differential response to restoration leads to a mosaic of soil water regimes across the site, which is reflected in a wider distribution of vegetation types. Therefore, the management goal of increasing wetland plant species occurrence is shown to co-occur with an increase in the site-scale diversity of plant community types. This result reveals the unique ability of the presented modeling framework to predict vegetation composition and aid land managers that are faced with difficult management decisions in a complex and uncertain future.

Booth, E. G.; Loheide, S. P.

2011-12-01

16

Thermal remote sensing of surface soil water content with partial vegetation cover for incorporation into climate models  

NASA Technical Reports Server (NTRS)

This study outlines a method for the estimation of regional patterns of surface moisture availability (M(sub 0)) and fractional vegetation (Fr) in the presence of spatially variable vegetation cover. The method requires relating variations in satellite-derived (NOAA, Advanced Very High Resolution Radiometer (AVHRR)) surface radiant temperature to a vegetation index (computed from satellite visible and near-infrared data) while coupling this association to an inverse modeling scheme. More than merely furnishing surface soil moisture values, the method constitues a new conceptual and practical approach for combining thermal infrared and vegetation index measurements for incorporating the derived values of M(sub 0) into hydrologic and atmospheric prediction models. Application of the technique is demonstrated for a region in and around the city of Newcastle upon Tyne situated in the northeast of England. A regional estimate of M(sub 0) is derived and is probabbly good for fractional vegetation cover up to 80% before errors in the estimated soil water content become unacceptably large. Moreover, a normalization scheme is suggested from which a nomogram, `universal triangle,' is constructed and is seen to fit the observed data well. The universal triangle also simplifies the inclusion of remotely derived M(sub 0) in hydrology and meteorological models and is perhaps a practicable step toward integrating derived data from satellite measurements in weather forecasting.

Gillies, Robert R.; Carlson, Toby N.

1995-01-01

17

Hydroecological model predictions indicate wetter and more diverse soil water regimes and vegetation types following floodplain restoration  

NASA Astrophysics Data System (ADS)

Transitions between aquatic and terrestrial ecosystems represent zones where soil moisture is a dominant factor influencing vegetation composition. Niche models based on hydrological and vegetation observations can be powerful tools for guiding management of these zones, especially when they are linked with physically based hydrological models. Floodplain restoration represents a unique opportunity to utilize such a predictive vegetation tool when a site's hydrology is altered to create a wetter environment. A variably saturated groundwater flow model was developed and used to simulate the soil moisture regime across a floodplain in Wisconsin where post-settlement alluvium was removed with the intent of increasing regionally threatened wetland plant species. Hydrological niche models based on simultaneous observations of vegetation composition and surface effective saturation were used to predict probability of presence for two plant species (Carex vulpinoidea (fox sedge) and Elymus canadensis(Canada wildrye)) and wetland indicator score (a composite indicator of relative frequency of species in five habitat categories) based on simulated surface effective saturation. The vegetation predictions following restoration are more wetland-species dominant overall. However, zones of the study site where a confining layer is present that decouples groundwater from the near-surface soil zone tend to be drier following restoration due to restricted upward groundwater flow and less soil water storage above the confining layer. As reflected by an increase in the interquartile range in the predicted wetland indicator score, this restoration technique may increase the site-scale spatial diversity of plant community types while simultaneously accomplishing the goal of increasing wetland plant species occurrence.

Booth, Eric G.; Loheide, Steven P., II

2012-06-01

18

Spatiotemporal analysis of urban environment based on the vegetation-impervious surface-soil model  

NASA Astrophysics Data System (ADS)

This study explores a spatiotemporal comparative analysis of urban agglomeration, comparing the Greater Toronto and Hamilton Area (GTHA) of Canada and the city of Tianjin in China. The vegetation-impervious surface-soil (V-I-S) model is used to quantify the ecological composition of urban/peri-urban environments with multitemporal Landsat images (3 stages, 18 scenes) and LULC data from 1985 to 2005. The support vector machine algorithm and several knowledge-based methods are applied to get the V-I-S component fractions at high accuracies. The statistical results show that the urban expansion in the GTHA occurred mainly between 1985 and 1999, and only two districts revealed increasing trends for impervious surfaces for the period from 1999 to 2005. In contrast, Tianjin has been experiencing rapid urban sprawl at all stages and this has been accelerating since 1999. The urban growth patterns in the GTHA evolved from a monocentric and dispersed pattern to a polycentric and aggregated pattern, while in Tianjin it changed from monocentric to polycentric. Central Tianjin has become more centralized, while most other municipal areas have developed dispersed patterns. The GTHA also has a higher level of greenery and a more balanced ecological environment than Tianjin. These differences in the two areas may play an important role in urban planning and decision-making in developing countries.

Guo, Huadong; Huang, Qingni; Li, Xinwu; Sun, Zhongchang; Zhang, Ying

2014-01-01

19

Vegetation helps microbes clean up contaminated soils  

SciTech Connect

According to research sponsored by DOE's Hazardous Waste Remedial Action Program, chemically contaminated soils may be cleaned up more rapidly by soil microorganisms if vegetation is present. The research was done at ORNL using soils collected from the Savannah River Site. It was found that trichloroethylene was decontaminated faster in soils surrounding plant roots than in soil without vegetation.

Not Available

1990-01-01

20

Climate-Soil-Vegetation Control on Groundwater Table Dynamics and its Feedbacks in a Climate Model  

SciTech Connect

Among the three dynamically linked branches of the water cycle, including atmospheric, surface, and subsurface water, groundwater is the largest reservoir and an active component of the hydrologic system. Because of the inherent slow response time, groundwater may be particularly relevant for long time-scale processes such as multi-years or decadal droughts. This study uses regional climate simulations with and without surface water – groundwater interactions for the conterminous U.S. to assess the influence of climate, soil, and vegetation on groundwater table dynamics, and its potential feedbacks to regional climate. Analysis shows that precipitation has a dominant influence on the spatial and temporal variations of groundwater table depth (GWT). The simulated GWT is found to decrease sharply with increasing precipitation. Our simulation also shows some distinct spatial variations that are related to soil porosity and hydraulic conductivity. Vegetation properties such as minimum stomatal resistance, and root depth and fraction are also found to play an important role in controlling the groundwater table. Comparing two simulations with and without groundwater table dynamics, we find that groundwater table dynamics mainly influences the partitioning of soil water between the surface (0 – 0.5 m) and subsurface (0.5 – 5 m) rather than total soil moisture. In most areas, groundwater table dynamics increases surface soil moisture at the expense of the subsurface, except in regions with very shallow groundwater table. The change in soil water partitioning between the surface and subsurface is found to strongly correlate with the partitioning of surface sensible and latent heat fluxes. The evaporative fraction (EF) is generally higher during summer when groundwater table dynamics is included. This is accompanied by increased cloudiness, reduced diurnal temperature range, cooler surface temperature, and increased cloud top height. Although both convective and non-convective precipitation are enhanced, the higher EF changes the partitioning to favor more non-convective precipitation, but this result could be sensitive to the convective parameterization used. Compared to simulations without groundwater table dynamics, the dry bias in the summer precipitation is slightly reduced over the central and eastern U.S. Groundwater table dynamics can provide important feedbacks to atmospheric processes, and these feedbacks are stronger in regions with deeper groundwater table, because the interactions between surface and subsurface are weak when the groundwater table is deep. This increases the sensitivity of surface soil moisture to precipitation anomalies, and therefore enhances land surface feedbacks to the atmosphere through changes in soil moisture and evaporative fraction. By altering the groundwater table depth, land use change and groundwater withdrawal can alter land surface response and feedback to the climate system.

Leung, Lai-Yung R.; Huang, Maoyi; Qian, Yun; Liang, Xu

2010-01-29

21

Multi-year assessment of soil-vegetation-atmosphere transfer (SVAT) modeling uncertainties over a Mediterranean agricultural site  

NASA Astrophysics Data System (ADS)

Vegetation productivity and water balance of Mediterranean regions will be particularly affected by climate and land-use changes. In order to analyze and predict these changes through land surface models, a critical step is to quantify the uncertainties associated with these models (processes, parameters) and their implementation over a long period of time. Besides, uncertainties attached to the data used to force these models (atmospheric forcing, vegetation and soil characteristics, crop management practices...) which are generally available at coarse spatial resolution (>1-10 km) and for a limited number of plant functional types, need to be evaluated. This paper aims at assessing the uncertainties in water (evapotranspiration) and energy fluxes estimated from a Soil Vegetation Atmosphere Transfer (SVAT) model over a Mediterranean agricultural site. While similar past studies focused on particular crop types and limited period of time, the originality of this paper consists in implementing the SVAT model and assessing its uncertainties over a long period of time (10 years), encompassing several cycles of distinct crops (wheat, sorghum, sunflower, peas). The impacts on the SVAT simulations of the following sources of uncertainties are characterized: - Uncertainties in atmospheric forcing are assessed comparing simulations forced with local meteorological measurements and simulations forced with re-analysis atmospheric dataset (SAFRAN database). - Uncertainties in key surface characteristics (soil, vegetation, crop management practises) are tested comparing simulations feeded with standard values from global database (e.g. ECOCLIMAP) and simulations based on in situ or site-calibrated values. - Uncertainties dues to the implementation of the SVAT model over a long period of time are analyzed with regards to crop rotation. The SVAT model being analyzed in this paper is ISBA in its a-gs version which simulates the photosynthesis and its coupling with the stomata conductance, as well as the time course of the plant biomass and the Leaf Area Index (LAI). The experiment was conducted at the INRA-Avignon (France) crop site (ICOS associated site), for which 10 years of energy and water eddy fluxes, soil moisture profiles, vegetation measurements, agricultural practises are available for distinct crop types. The uncertainties in evapotranspiration and energy flux estimates are quantified from both 10-year trend analysis and selected daily cycles spanning a range of atmospheric conditions and phenological stages. While the net radiation flux is correctly simulated, the cumulated latent heat flux is under-estimated. Daily plots indicate i) an overestimation of evapotranspiration over bare soil probably due to an overestimation of the soil water reservoir available for evaporation and ii) an under-estimation of transpiration for developed canopy. Uncertainties attached to the re-analysis atmospheric data show little influence on the cumulated values of evapotranspiration. Better performances are reached using in situ soil depths and site-calibrated photosynthesis parameters compared to the simulations based on the ECOCLIMAP standard values. Finally, this paper highlights the impact of the temporal succession of vegetation cover and bare soil on the simulation of soil moisture and evapotranspiration over a long period of time. Thus, solutions to account for crop rotation in the implementation of SVAT models are discussed.

Garrigues, S.; Olioso, A.; Calvet, J.-C.; Lafont, S.; Martin, E.; Chanzy, A.; Marloie, O.; Bertrand, N.; Desfonds, V.; Renard, D.

2012-04-01

22

Impact of Hillslope-Scale Organization of Topography, Soil Moisture, Soil Temperature, and Vegetation on Modeling Surface Microwave Radiation Emission  

E-print Network

Microwave radiometry will emerge as an important tool for global remote sensing of near-surface soil moisture in the coming decade. In this modeling study, we find that hillslope-scale topography (tens of meters) influences ...

Flores, Alejandro N.

23

Vegetation Effects on Soil Moisture Estimation  

NASA Technical Reports Server (NTRS)

Several successful algorithms have been developed to estimate soil moisture of bare surfaces. We previously reported a new algorithm using the tilted Bragg approximation. However, these algorithms are only applicable to bare surfaces. When vegetation is present, soil moisture is typically underestimated by bare surface algorithms. In order to derive soil moisture under vegetation, we have to understand the complex scattering process due to vegetation. Our main interest is to retrieve the global soil moisture information using Hydros L-band polarimetric radar data. The Hydros mission will provide the first global view of land soil moisture using L-band radar and radiometer. The unique characteristics of the Hydros data are the availability of the low resolution soil moisture information from radiometer data and the continuous time series radar data collected at the same incidence angle. In this paper, we will examine a potential inversion algorithm to retrieve soil moisture under vegetation canopies using Hydros L-band polarimetric radar data.

Kim, Yunjin; van Zyl, Jakob

2004-01-01

24

Modelling the links between vegetation and landforms  

Microsoft Academic Search

Vegetation is the most important intermediate through which climate and land use modify geomorphological processes and landforms. In this paper we explore three types of model which attempt to simulate the links to uncultivated vegetation, all sharing a common basis in hydrology. The first simulates the relationship between climate, vegetation and erosion rates for a fixed topography and soil cover.

Mike Kirkby

1995-01-01

25

Solar radiation signature manifested on the spatial patterns of modeled soil moisture, vegetation, and topography using an ecohydro-geomorphic landscape evolution model  

NASA Astrophysics Data System (ADS)

The role of solar radiation on ecohydrologic fluxes, vegetation dynamics, species composition, and landscape morphology have long been documented in field studies. However a numerical model framework to integrate a range of ecohydrologic and geomorphic processes to explore the integrated ecohydro-geomorphic landscape response have been missing. In this study, our aim is to realistically represent flood generation and solar-radiation-driven echydrologic dynamics in a landscape evolution model (LEM) to investigate how ecohydrologic differences caused by differential irradiance on opposing hillslopes manifest themselves on the organization of modeled topography, soil moisture and plant biomass. We use the CHILD LEM equipped with a spatially-distributed solar-radiation component, leading to spatial patterns of soil moisture; a vegetation dynamics component that explicitly tracks above- and below-ground biomass; and a runoff component that allows for runoff-runon processes along the landscape flow paths. Ecohydrological component has been verified using a detailed data gathered from Sevilleta National Wildlife Refuge in central New Mexico, and Walnut Gulch Experimental Watershed in southern Arizona. LEM scenarios were designed to compare the outcomes of spatially distributed versus spatially uniform solar radiation forced with a constant climate and variable uplift. Modeled spatial patterns of soil moisture confirm empirical observations at the landscape scale and other hydrologic modeling studies. The spatial variability in soil moisture is controlled by aspect prior to the wet season (North American Monsoon, NAM), and by the hydraulic connectivity of the flow network during NAM. Aspect and network connectivity signatures are also manifested on plant biomass with typically denser vegetation cover on north-facing slopes than south facing slopes. Over the long-term, CHILD gives slightly steeper and less dissected north-facing slopes more dissected south facing slopes and an overall asymmetry in the modeled morphology of valleys. The model simulations show how subtle differences in biomass and soil moisture dynamics at annual scale lead to distinct geomorphic differences at both hillslope and catchment scales.

Yetemen, O.; Flores Cervantes, J. H.; Istanbulluoglu, E.; Vivoni, E. R.

2013-12-01

26

Retrieving pace in vegetation growth using precipitation and soil moisture  

NASA Astrophysics Data System (ADS)

The complexity of interactions between the biophysical components of the watershed increases the challenge of understanding water budget. Hence, the perspicacity of the continuum soil-vegetation-atmosphere's functionality still remains crucial for science. This study targeted the Texas Gulf watershed and evaluated the behavior of vegetation covers by coupling precipitation and soil moisture patterns. Growing season's Normalized Differential Vegetation Index NDVI for deciduous forest and grassland were used over a 23 year period as well as precipitation and soil moisture data. The role of time scales on vegetation dynamics analysis was appraised using both entropy rescaling and correlation analysis. This resulted in that soil moisture at 5 cm and 25cm are potentially more efficient to use for vegetation dynamics monitoring at finer time scale compared to precipitation. Albeit soil moisture at 5 cm and 25 cm series are highly correlated (R2>0.64), it appeared that 5 cm soil moisture series can better explain the variability of vegetation growth. A logarithmic transformation of soil moisture and precipitation data increased correlation with NDVI for the different time scales considered. Based on a monthly time scale we came out with a relationship between vegetation index and the couple soil moisture and precipitation [NDVI=a*Log(% soil moisture)+b*Log(Precipitation)+c] with R2>0.25 for each vegetation type. Further, we proposed to assess vegetation green-up using logistic regression model and transinformation entropy using the couple soil moisture and precipitation as independent variables and vegetation growth metrics (NDVI, NDVI ratio, NDVI slope) as the dependent variable. The study is still ongoing and the results will surely contribute to the knowledge in large scale vegetation monitoring. Keywords: Precipitation, soil moisture, vegetation growth, entropy Time scale, Logarithmic transformation and correlation between soil moisture and NDVI, precipitation and NDVI. The analysis is performed by combining both scenes 7 and 8 data. Schematic illustration of the two dimension transinformation entropy approach. T(P,SM;VI) stand for the transinformation contained in the couple soil moisture (SM)/precipitation (P) and explaining vegetation growth (VI).

Sohoulande Djebou, D. C.; Singh, V. P.

2013-12-01

27

Modeling vegetation rooting strategies on a hillslope  

NASA Astrophysics Data System (ADS)

The manner in which water and energy is partitioned and redistributed along a hillslope is the result of complex coupled ecohydrological interactions between the climatic, soils, topography and vegetation operating over a wide range of spatiotemporal scales. Distributed process based modeling creates a framework through which the interaction of vegetation with the subtle differences in the spatial and temporal dynamics of soil moisture that arise under localized abiotic conditions along a hillslope can be simulated and examined. One deficiency in the current dynamic vegetation models is the one sided manner in which vegetation responds to soil moisture dynamics. Above ground, vegetation is given the freedom to dynamically evolve through alterations in fractional vegetation cover and/or canopy height and density; however below ground rooting profiles are simplistically represented and often held constant in time and space. The need to better represent the belowground role of vegetation through dynamic rooting strategies is fundamental in capturing the magnitude and timing of water and energy fluxes between the atmosphere and land surface. In order to allow vegetation to adapt to gradients in soil moisture a dynamic rooting scheme was incorporated into tRIBS+VEGGIE (a physically based distributed ecohydrological model). The dynamic rooting scheme allows vegetation the freedom to adapt their rooting depth and distribution in response abiotic conditions in a way that more closely mimics observed plant behavior. The incorporation of this belowground plasticity results in vegetation employing a suite of rooting strategies based on soil texture, climatic conditions and location on the hillslope.

Sivandran, G.; Bras, R. L.

2011-12-01

28

The Application and Performance of Two Soil-Vegetation-Atmosphere Modelling Platforms to a Real Hydrologic Catchment  

NASA Astrophysics Data System (ADS)

Land surface models are important in providing lower boundary fluxes and moisture for atmospheric models. Despite the increase in complexity and detailed representation of vegetation and root zone, LSMs remain for the most part one-dimensional column models which ignore lateral water flow at the land surface and within the top soil layers. In order to include processes effecting soil moisture variations such as shallow groundwater, runoff, overland flow, and subsurface lateral flow, a number of simulation platforms with varying complexity which couple groundwater, land surface, and atmospheric models have emerged. In this study, we compare two different integrated soil-vegetation-atmosphere modelling platforms: the ParFlow-CLM-COSMO model, developed within the Transregional Collaborative Research Centre (TR32), and the HIRHAM-MIKE SHE model, developed within the HOBE Centre for Hydrology and the HYdrological Modelling for Assessing Climate Change Impacts at differeNT Scales (HYACINTS) project. Both modelling platforms contain distributed, physically based, state-of-the-art components. ParFlow-CLM-COSMO consists of the variably saturated groundwater model ParFlow, the Community Land Model (CLM), and the regional climate and weather forecast model COSMO (German Weather Service, DWD). The HIRHAM-MIKE SHE model consists of the HIRHAM regional climate model (Danish Meteorological Institute), the SWET (Shuttleworth and Wallace Evapotranspiration) land-surface model, and the integrated hydrological model MIKE SHE (DHI). There are differences however between the two platforms in the handling of specific processes within the model components as well as differences in the coupling approach used. During the first part of the comparison study, we focus on the coupled subsurface-landsurface components offline from the atmosphere. One of the main differences in the handling of the subsurface component in both models is the inclusion of lateral flow in the unsaturated zone. In the MIKE SHE model, the 3D Richards' equation is used for the saturated subsurface region, while the 1D Richards' equation is used to simulate water flow in the unsaturated zone using simulated dynamic groundwater levels from its saturated zone module. ParFlow, on the other hand, includes both lateral and vertical flow by using the 3D Richards' equation for the subsurface to calculate the pressure field. This allows for lateral flows in the unsaturated zone. One of the main questions to be investigated by this comparison study is whether such a dynamic approach for the subsurface is needed within a real watershed, and if so, at which locations and times. The simulations for both platforms are established for the HOBE hydrologic observatory catchment in Denmark, the Skjern catchment. During the second part of this study, the comparison is extended to include the atmospheric components, which differ in the exchange of atmospheric forcing variables and surface moisture and energy fluxes, in fully coupled simulations. While ParFlow-CLM-COSMO utilizes an external coupler, HIRHAM-MIKE SHE implements a new OpenMI technology approach. The comparison study will highlight the effects and experiences of using different coupled model approaches on the simulated subsurface-land surface-atmosphere interactions within a real hydrologic catchment.

Rihani, Jehan; Dahl Larsen, Morten Andreas; Stisen, Simon; Refsgaard, Jens Christian; Høgh Jensen, Karsten; Simmer, Clemens

2013-04-01

29

Modeling Spatial Patterns of Soil Respiration in Maize Fields from Vegetation and Soil Property Factors with the Use of Remote Sensing and Geographical Information System  

PubMed Central

To examine the method for estimating the spatial patterns of soil respiration (Rs) in agricultural ecosystems using remote sensing and geographical information system (GIS), Rs rates were measured at 53 sites during the peak growing season of maize in three counties in North China. Through Pearson's correlation analysis, leaf area index (LAI), canopy chlorophyll content, aboveground biomass, soil organic carbon (SOC) content, and soil total nitrogen content were selected as the factors that affected spatial variability in Rs during the peak growing season of maize. The use of a structural equation modeling approach revealed that only LAI and SOC content directly affected Rs. Meanwhile, other factors indirectly affected Rs through LAI and SOC content. When three greenness vegetation indices were extracted from an optical image of an environmental and disaster mitigation satellite in China, enhanced vegetation index (EVI) showed the best correlation with LAI and was thus used as a proxy for LAI to estimate Rs at the regional scale. The spatial distribution of SOC content was obtained by extrapolating the SOC content at the plot scale based on the kriging interpolation method in GIS. When data were pooled for 38 plots, a first-order exponential analysis indicated that approximately 73% of the spatial variability in Rs during the peak growing season of maize can be explained by EVI and SOC content. Further test analysis based on independent data from 15 plots showed that the simple exponential model had acceptable accuracy in estimating the spatial patterns of Rs in maize fields on the basis of remotely sensed EVI and GIS-interpolated SOC content, with R2 of 0.69 and root-mean-square error of 0.51 µmol CO2 m?2 s?1. The conclusions from this study provide valuable information for estimates of Rs during the peak growing season of maize in three counties in North China. PMID:25157827

Huang, Ni; Wang, Li; Guo, Yiqiang; Hao, Pengyu; Niu, Zheng

2014-01-01

30

Modeling spatial patterns of soil respiration in maize fields from vegetation and soil property factors with the use of remote sensing and geographical information system.  

PubMed

To examine the method for estimating the spatial patterns of soil respiration (Rs) in agricultural ecosystems using remote sensing and geographical information system (GIS), Rs rates were measured at 53 sites during the peak growing season of maize in three counties in North China. Through Pearson's correlation analysis, leaf area index (LAI), canopy chlorophyll content, aboveground biomass, soil organic carbon (SOC) content, and soil total nitrogen content were selected as the factors that affected spatial variability in Rs during the peak growing season of maize. The use of a structural equation modeling approach revealed that only LAI and SOC content directly affected Rs. Meanwhile, other factors indirectly affected Rs through LAI and SOC content. When three greenness vegetation indices were extracted from an optical image of an environmental and disaster mitigation satellite in China, enhanced vegetation index (EVI) showed the best correlation with LAI and was thus used as a proxy for LAI to estimate Rs at the regional scale. The spatial distribution of SOC content was obtained by extrapolating the SOC content at the plot scale based on the kriging interpolation method in GIS. When data were pooled for 38 plots, a first-order exponential analysis indicated that approximately 73% of the spatial variability in Rs during the peak growing season of maize can be explained by EVI and SOC content. Further test analysis based on independent data from 15 plots showed that the simple exponential model had acceptable accuracy in estimating the spatial patterns of Rs in maize fields on the basis of remotely sensed EVI and GIS-interpolated SOC content, with R2 of 0.69 and root-mean-square error of 0.51 µmol CO2 m(-2) s(-1). The conclusions from this study provide valuable information for estimates of Rs during the peak growing season of maize in three counties in North China. PMID:25157827

Huang, Ni; Wang, Li; Guo, Yiqiang; Hao, Pengyu; Niu, Zheng

2014-01-01

31

Soil erosion modelled with USLE and PESERA using QuickBird derived vegetation parameters in an alpine catchment  

Microsoft Academic Search

The focus of soil erosion research in the Alps has been in two categories: (i) on-site measurements, which are rather small scale point measurements on selected plots often constrained to irrigation experiments or (ii) off-site quantification of sediment delivery at the outlet of the catchment. Results of both categories pointed towards the importance of an intact vegetation cover to prevent

K. Meusburger; N. Konz; M. Schaub; C. Alewell

2010-01-01

32

Exploring a VIS (vegetation-impervious surface-soil) model for urban ecosystem analysis through remote sensing: comparative anatomy for cities†  

Microsoft Academic Search

Growing interest in urban systems as ecological entities calls for some standards in parameterizing biophysical composition of urban environments. A vegetation-impervious surface-soil ( V-I-S) model is presented as a possible basis for standardization. The V-I-S model may serve as a foundation for characterizing urban\\/near-urban environments universally, and for comparison of urban morphology within and between cities. Inasmuch as the model

M. K. RIDD

1995-01-01

33

Bowen ratio measurements above various vegetation covers and its comparison with actual evapotranspiration estimated by SoilClim model  

NASA Astrophysics Data System (ADS)

The principle of Bowen ratio is one of the available techniques for measurements of actual evapotranspiration (ETa) as one of essential water balance fractions. The main aims of submitted study were: (i) to compare the water balance of selected crops, (ii) to compare outputs of SoilClim model with observed parameters (including ETa on Bowen ratio basis). The measurements were conducted at two experimental stations in the Czech Republic (Polkovice 49°23´ (N), 17°17´ (E), 205 m a.s.l.; Domanínek 49°32´ (N), 16°15´ (E), 544 m a.s.l.) during the years 2009 and 2010. Together with Bowen ratio the global solar radiation, radiation balance, soil heat flux, volumetric soil moisture and temperature within selected depths, precipitation and wind speed were measured. The measurements were conducted simultaneously above various covers within the same soil conditions: spring barley vs. winter wheat, spring barley vs. winter rape; grass vs. poplars; harvested field after tillage vs. harvested field after cereals without any tillage. The observed parameters from different covers were compared with SoilClim estimates. SoilClim model is modular software for water balance and soil temperature modelling and finally could be used for soil Hydric and Thermic regimes (according to USDA classification) identification. The core of SoilClim is based on modified FAO Penman-Monteith methodology. Submitted study proved the applicability of SoilClim model for ETa, soil moisture within two defined layers and soil temperature (in 0.5 m depth) estimates for various crops, covers, selected soil types and climatic conditions. Acknowledgement: We gratefully acknowledge the support of the Grant Agency of the Czech Republic (no. 521/09/P479) and the project NAZV QI91C054. The study was also supported by Research plan No. MSM6215648905 "Biological and technological aspects of sustainability of controlled ecosystems and their adaptability to climate change".

Hlavinka, P.; Trnka, M.; Fischer, M.; Kucera, J.; Mozny, M.; Zalud, Z.

2010-09-01

34

N 2 O and NO emission from agricultural fields and soils under natural vegetation: summarizing available measurement data and modeling of global annual emissions  

Microsoft Academic Search

The number of published N2O and NO emissions measurements is increasing steadily, providing additional information about driving factors of these emissions and allowing an improvement of statistical N-emission models. We summarized information from 1008 N2O and 189 NO emission measurements for agricultural fields, and 207 N2O and 210 NO measurements for soils under natural vegetation. The factors that significantly influence

Elke Stehfest; Lex Bouwman

2006-01-01

35

Correspondence between vegetation and soils in wetlands and nearby uplands  

USGS Publications Warehouse

The association between vegetation and soils from a geographically broad sampling of wetlands and adjoining uplands is reported for 38 hydric and 26 nonhydric soils, as recognized in the hydric soils list of the Soil Conservation Service. Wetlands represented in the study include estuaries, pitcher plant bogs, prairie depressional wetlands, and western riparian lands. The agreement between vegetation and soils is clear with few exceptions. In general, hydric soils support hydrophytic plant communities, and nonhydric soils support upland communities. Only 10% of the hydric soils sampled support upland communities and only 15% of the nonhydric soils support wetland communities. Exceptions to the correspondence between vegetation and soils are discussed; local hydrology, the transitional nature of some soils, and other determinants of wetland vegetation structure (e.g., salinity, disturbance) seem to account for many of the observed discrepancies. A method that simplifies the complexity of soils and vegetation cannot be expected to represent accurately all details of their interrelations.

Scott, Michael L.; Slauson, William L.; Segelquist, Charles A.; Auble, Gregor T.

1989-01-01

36

Harmonic propagation of variability in surface energy balance within a coupled soil-vegetation-atmosphere system  

E-print Network

[1] The response of a soil-vegetation-atmosphere continuum model to incoming radiation forcing is investigated in order to gain insights into the coupling of soil and atmospheric boundary layer (ABL) states and fluxes. The ...

Gentine, P.

37

Soil Respiration Responses to Variation in Temperature Treatment and Vegetation Type  

NASA Astrophysics Data System (ADS)

Complex linkages exist between terrestrial vegetation, soil moisture, soil organic matter (SOM), local climate, and soil microorganisms. Thus, large-scale changes in vegetation, such as the woody plant encroachment observed in many historically semiarid and arid grasslands worldwide, could potentially alter the flux of carbon from soil reserves to the atmosphere. Mathematical models that attempt to project the long-term impact of vegetative shifts on soil fluxes largely rely on assumptions such as first-order donor control rather than incorporate the biological aspects of soil respiration such as microbial activity. To examine the impact of vegetation type on soil physicochemical properties and soil microbial respiration and provide experimental data to refine existing predictive models, we compared soil (ground basalt from northern Arizona) in mesocosms established with no vegetation, velvet mesquites (Prosopis velutina; woody shrub), or sideoats gramas (Bouteloua curtipendula; grass) for 2 years, The temperature sensitivity of soil respiration was examined by incubating soil (0-10 and 10-30 cm depth fractions) from each vegetation treatment at 10, 20, 30, and 40 °C for 24 hours. Vegetated soils contained more SOM (~0.1% for mesquite and grass mesocosms) than non-vegetated soils (~0.02%). Respiration rates were generally highest from grass-established soils, intermediate from mesquite-established soils, and lowest from non-vegetated soils. Respiration rates of samples incubated without the addition of substrate peaked at approximately 30 °C, whereas respiration rates of samples incubated with dextrose were highest at 40 °C. Further, the respiration assays suggest that while respiration rates are overall higher in grass-established soils, mesquite-established soils are more temperature sensitive which may have significant implications in the context of global warming and current fire management practices.

Liu, S.; Pavao-zuckerman, M.

2013-12-01

38

On the spatial and temporal links between vegetation, climate, and soil moisture  

Microsoft Academic Search

The impact of climate fluctuations can be observed in the dynamics of vegetation and most particularly in the sensitive environment of savannas. In this paper we present a model for the local competition for soil moisture among neighboring vegetation. The initial condition for the model is a random field where at each point the soil moisture is the mean water

I. Rodriguez-Iturbe; P. D'Odorico; A. Porporato; L. Ridolfi

1999-01-01

39

Soil and vegetation effects of tropical deforestation  

Microsoft Academic Search

\\u000a The regrowth of vegetation after deforestation provides a paradox: of rapid growth but with species composition and diversity\\u000a at odds with the original primary forest. Secondary species which regenerate from seed in the soil after clearance are totally\\u000a different from the primary species which dominate ‘climax’ tropical rain forests. Regrowth of primary forest after disturbance\\u000a depends on distance and access

S. M. Ross

40

Ecological optimality in water-limited natural soil-vegetation systems. I - Theory and hypothesis  

NASA Technical Reports Server (NTRS)

The solution space of an approximate statistical-dynamic model of the average annual water balance is explored with respect to the hydrologic parameters of both soil and vegetation. Within the accuracy of this model it is shown that water-limited natural vegetation systems are in stable equilibrium with their climatic and pedologic environments when the canopy density and species act to minimize average water demand stress. Theory shows a climatic limit to this equilibrium above which it is hypothesized that ecological pressure is toward maximization of biomass productivity. It is further hypothesized that natural soil-vegetation systems will develop gradually and synergistically, through vegetation-induced changes in soil structure, toward a set of hydraulic soil properties for which the minimum stress canopy density of a given species is maximum in a given climate. Using these hypotheses, only the soil effective porosity need be known to determine the optimum soil and vegetation parameters in a given climate.

Eagleson, P. S.

1982-01-01

41

Modeling Vegetable Oil Viscosity  

Microsoft Academic Search

Vegetable oils have become more attractive recently because of their environmental benefits and the fact that it is made from renewable resources. Vegetable oils do not contain any sulfur, aromatic hydrocarbons, metals, or crude oil residues. Short-term engine tests indicate good potential for vegetable oil fuels. Long-term endurance tests may show serious problems in injector coking, ring sticking, gum formation,

M. Balat

2008-01-01

42

Modelling of vegetation volumes  

NASA Technical Reports Server (NTRS)

The purpose is to describe work that is being done to find theoretical models to describe radar backscatter from vegetation layers. The geometry of the problem is shown. The information that one would like to find through the application of the results of these models would include: the thickness of the layer; the absorption in the layer (i.e., density, moisture content, and biomass); the geometry of the scatterers (i.e., shape and orientation); how much of the received power is due to volume scattering only; and a way to enhance the ratio of scattering that has some interaction with the ground surface. The proposed ways to find this information are discussed.

Vanzyl, J. J.; Papas, C. H.; Engheta, N.; Elachi, C.

1985-01-01

43

Spatial prediction of soil organic matter in northern Kazakhstan based on topographic and vegetation information  

Microsoft Academic Search

This study aimed to improve the accuracy of spatial prediction for soil organic matter, potential mineralizable carbon (PMC) and soil organic carbon (SOC), using secondary information, namely topographic and vegetation information, in northern Kazakhstan. Secondary information included elevation (ELEV), mean curvature (MEANC), compound topographic index (CTI) and slope (SLOPE) obtained from a digital elevation model, and enhanced vegetation index (VI)

Yusuke Takata; Shinya Funakawa; Kanat Akshalov; Norio Ishida; Takashi Kosaki

2007-01-01

44

Coevolution of hydraulic, soil and vegetation processes in estuarine wetlands  

NASA Astrophysics Data System (ADS)

Estuarine wetlands of south eastern Australia, typically display a vegetation zonation with a sequence mudflats - mangrove forest - saltmarsh plains from the seaward margin and up the topographic gradient. Estuarine wetlands are among the most productive ecosystems in the world, providing unique habitats for fish and many terrestrial species. They also have a carbon sequestration capacity that surpasess terrestrial forest. Estuarine wetlands respond to sea-level rise by vertical accretion and horizontal landward migration, in order to maintain their position in the tidal frame. In situations in which buffer areas for landward migration are not available, saltmarsh can be lost due to mangrove encroachment. As a result of mangrove invasion associated in part with raising estuary water levels and urbanisation, coastal saltmarsh in parts of south-eastern Australia has been declared an endangered ecological community. Predicting estuarine wetlands response to sea-level rise requires modelling the coevolving dynamics of water flow, soil and vegetation. This paper presents preliminary results of our recently developed numerical model for wetland dynamics in wetlands of the Hunter estuary of NSW. The model simulates continuous tidal inflow into the wetland, and accounts for the effect of varying vegetation types on flow resistance. Coevolution effects appear as vegetation types are updated based on their preference to prevailing hydrodynamic conditions. The model also considers that accretion values vary with vegetation type. Simulations are driven using local information collected over several years, which includes estuary water levels, accretion rates, soil carbon content, flow resistance and vegetation preference to hydraulic conditions. Model results predict further saltmarsh loss under current conditions of moderate increase of estuary water levels.

Trivisonno, Franco; Rodriguez, Jose F.; Riccardi, Gerardo; Saco, Patricia; Stenta, Hernan

2014-05-01

45

Radiometric Sensitivity to Soil Moisture Relative to Vegetation Canopy Anisotropy, Canopy Temperature,  

E-print Network

Radiometric Sensitivity to Soil Moisture Relative to Vegetation Canopy Anisotropy, Canopy Sensitivity to Soil Moisture Relative to Vegetation Canopy Anisotropy, Canopy Temperature, and Canopy Water of micrometeorology and soil moisture, the radiometric sensi- tivities to vegetation canopy temperature, soil moisture

Sarabandi, Kamal

46

Thermal Remote Sensing of Surface Soil Water Content with Partial Vegetation Cover for Incorporation into Climate Models  

Microsoft Academic Search

This study outlines a method for the estimation of regional patterns of surface moisture availability (M0) and fractional vegetation (Fr) in the presence of spatially variable vegetation cover. The method requires relating variations in satellite-derived (NOAA, Advanced Very High Resolution Radiometer) surface radiant temperature to a vegetation index (computed from satellite visible and near-infrared data) while coupling this association to

Robert R. Gillies; Toby N. Carlson

1995-01-01

47

An Overview of the Use of the SimSphere Soil Vegetation Atmosphere Transfer (SVAT) Model for the Study of Land-Atmosphere Interactions.  

PubMed

Soil Vegetation Atmosphere Transfer (SVAT) models consist of deterministic mathematical representations of the physical processes involved between the land surface and the atmosphere and of their interactions, at time-steps acceptable for the study of land surface processes. The present article provides a comprehensive and systematic review of one such SVAT model suitable for use in mesoscale or boundary layer studies, originally developed by [1]. This model, which has evolved significantly both architecturally and functionally since its foundation, has been widely applied in over thirty interdisciplinary science investigations, and it is currently used as a learning resource for students in a number of educational institutes globally. The present review is also regarded as very timely, since a variation of a method using this specific SVAT model along with satellite observations is currently being considered in a scheme being developed for the operational retrieval of soil surface moisture by the US National Polar-orbiting Operational Environmental Satellite System (NPOESS), in a series of satellites that are due to be launched from 2016 onwards. PMID:22408527

Petropoulos, George; Carlson, Toby N; Wooster, Martin J

2009-01-01

48

Response of spectral vegetation indices to soil moisture in grasslands and shrublands  

USGS Publications Warehouse

The relationships between satellite-derived vegetation indices (VIs) and soil moisture are complicated because of the time lag of the vegetation response to soil moisture. In this study, we used a distributed lag regression model to evaluate the lag responses of VIs to soil moisture for grasslands and shrublands at Soil Climate Analysis Network sites in the central and western United States. We examined the relationships between Moderate Resolution Imaging Spectroradiometer (MODIS)-derived VIs and soil moisture measurements. The Normalized Difference Vegetation Index (NDVI) and Normalized Difference Water Index (NDWI) showed significant lag responses to soil moisture. The lag length varies from 8 to 56 days for NDVI and from 16 to 56 days for NDWI. However, the lag response of NDVI and NDWI to soil moisture varied among the sites. Our study suggests that the lag effect needs to be taken into consideration when the VIs are used to estimate soil moisture. ?? 2011 Taylor & Francis.

Zhang, L.; Ji, L.; Wylie, B.K.

2011-01-01

49

Dual frequency microwave radiometer measurements of soil moisture for bare and vegetated rough surfaces  

NASA Technical Reports Server (NTRS)

Controlled ground-based passive microwave radiometric measurements on soil moisture were conducted to determine the effects of terrain surface roughness and vegetation on microwave emission. Theoretical predictions were compared with the experimental results and with some recent airborne radiometric measurements. The relationship of soil moisture to the permittivity for the soil was obtained in the laboratory. A dual frequency radiometer, 1.41356 GHz and 10.69 GHz, took measurements at angles between 0 and 50 degrees from an altitude of about fifty feet. Distinct surface roughnesses were studied. With the roughness undisturbed, oats were later planted and vegetated and bare field measurements were compared. The 1.4 GHz radiometer was less affected than the 10.6 GHz radiometer, which under vegetated conditions was incapable of detecting soil moisture. The bare surface theoretical model was inadequate, although the vegetation model appeared to be valid. Moisture parameters to correlate apparent temperature with soil moisture were compared.

Lee, S. L.

1974-01-01

50

Linking carbon-water- and nitrogen fluxes at forest ecosystems throughout Europe with a coupled soil-vegetation process model "LandscapeDNDC"  

NASA Astrophysics Data System (ADS)

Forest ecosystems in Europe play a key role in the emission reduction commitment agreed in the Kyoto Protocol for mitigating climatic change. Forest ecological functioning and potential services (such as carbon sequestration) are a matter of debate for policy decision makers resulting from the need of identifying affordable strategies for forest management and exploitation against climate change. Forest ecosystem functioning and the linkages governing carbon-, water- and nitrogen fluxes at site scale was evaluated for three dominant tree species (Pinus sylvestris, Picea abies and Fagus sylvatica) grown on 10 different sites across Europe. We did answer in particular the following questions: a) is LandscapeDNDC able to represent NEE, GPP, TER and ET fluxes for dominant forest types in Europe at different sites with only a species specific parameterization? b) What is the relation between carbon input into the ecosystem and on the emission of carbon and nitrogen from the forest soil? Furthermore we analyzed the interaction between carbon-, nitrogen-, and water cycle, in particular the dependence of gaseous fluxes on water and litter availability. LandscapeDNDC is a process based model that integrates modules for carbon, nitrogen and water cycling within terrestrial ecosystems (i.e. forest) on the site and regional scale. Biosphere, atmosphere and hydrosphere processes in forest ecosystems are linked by daily time step integration of the microclimate, water cycle, soil biogeochemistry and tree physiology and dimensional growth modules which balances all three aforementioned cycles. All processes and state variables are considered in a vertically structured one dimensional vertical column that reaches from rooting depth (more than 1 m depth) to the uppermost canopy layer. LandscapeDNDC was tested against long term (about 10 years) field data. The capability of the applied model for reproducing daily derived GPP and TER was accompanied by a high statistical precision (r2), accuracy (r2eff) and agreement (RMSPEn) while for reproducing daily NEE and ET as well as soil moisture was accompanied by a good statistical precision and agreement. In addition, beside C fixation also simulated C allocation into different vegetation compartments agreed well with measured data on biomass development and vegetation structure. Also soil respiration and N2O emissions agreed well with field observations. Soil respiration was driven by GPP and the rates of N2O fluxes depended on soil ecosystem properties and were influenced by litter C/N inputs and weather conditions. In conclusion by use of general tree species parameterizations LandscapeDNDC was capable to simulate and capture impacts of a multitude of environmental drivers on forest ecosystem C-, N-, water dynamics, as well as linking above - and belowground processes across various sites in Europe. Nevertheless, the quality of measured data (e.g. spatial representation, time resolution) as well as the existing description of ecosystem processes in the model should be considered when evaluating the capability of process based models to be used for evaluation of biogeochemical ecosystem functioning.

Molina Herrera, Saul; Grote, Rüdiger; Haas, Edwin; Kiese, Ralf; Butterbach-Bahl, Klaus

2013-04-01

51

Transregional Collaborative Research Centre 32: Patterns in Soil-Vegetation  

NASA Astrophysics Data System (ADS)

The soil, vegetation and the lower atmosphere (SVA) are key compartments of the Earth, where almost all activities of mankind take place. This region is characterized by extremely complex patterns, structures and processes that act at different temporal and spatial scales. While the exchange of energy, water and carbon is continuous between the different compartments, the pertinent fluxes are strongly heterogeneous and variable in space and time. The overarching TR32 paradigm is that the characterisation of structures and patterns will lead to a deeper qualitative and quantitative understanding of the SVA system, and ultimately to better predictions of the SVA state. The TR32 combines research groups in the field of soil and plant science, remote sensing, hydrology, meteorology and mathematics located at the Universities of Aachen, Bonn, Braunschweig and Cologne and the Research Centre Juelich study the soil-vegetation atmosphere system under the novel holistic paradigm of patterns. To understand the mechanisms leading to spatial and temporal patterns in energy and matter fluxes of the SVA system we link experiments and theory via model-observation integration. Focusing our research on the Rur Catchment (Germany), patterns are monitored since 2006 continuously using existing and novel geophysical and remote sensing techniques from the local to the catchment scale based on ground penetrating radar methods, induced polarization, radiomagnetotellurics, electrical resistivity tomography, boundary layer scintillometry, lidar techniques, microwave radiometry, and precipitation radars with polarization diversity. Modeling approaches involve high resolution numerical weather prediction (NWP; 400m) and hydrological models (few meters). Example work from the first phase includes the transfer of laboratory methods to the field; the measurements of patterns of soil-carbon, evapotranspiration and respiration measured in the field; catchment-scale modeling of exchange processes and the setup of an atmospheric boundary layer monitoring network. In the second phase (2011-2014), the focus is on the integration of models from the groundwater to the atmosphere for both the m- and km-scale and the extension of the experimental monitoring in respect to vegetation. The general coupled modeling concept is based on the atmospheric model COSMO, the land surface model CLM and the hydrological model ParFlow. In order to bridge the scale gaps in measurements and modelling an LES model will be validated via a dedicated field campaign.

Kollet, S. J.; Simmer, C.; Masbou, M.; Boessenkool, K.; Crewell, S.; Diekkruger, B.; Huber, K.; Klitzsch, N.; Koyama, C. N.; Vereecken, H.

2011-12-01

52

Soil aggregate stability under different Mediterranean vegetation types  

Microsoft Academic Search

The influence of vegetation type on soil erodibility was studied by means of aggregate stability measurements using the Modified Emerson Water Dispersion Test (MEWDT), water-drop impacts (CND and TDI) and Ultrasonic Disruption (UD) methods on soils from north-facing slopes of the mountain range of La Serra Grossa in the eastern Iberian Peninsula. Soils with similar characteristics but covered by the

A. Cerda

1998-01-01

53

Influences of soil moisture and vegetation on convective precipitation forecasts  

E-print Network

Influences of soil moisture and vegetation on convective precipitation forecasts over the United National Laboratory, Upton, New York, USA Abstract This study investigates the influences of soil moisture (NARR) data were used as initial and boundary conditions. We also used an adjusted soil moisture

Robock, Alan

54

Modeling biophysical exchanges and micro-meteorology in soil-vegetation-atmosphere continuums: Results from a two-story boreal aspen forest  

NASA Astrophysics Data System (ADS)

In this study, a multilayer canopy process model for the exchanges of radiative energy, sensible heat, water vapor and CO2 between vegetation and the atmosphere is developed. The model is designed to be applied to both one-story and two-story canopies. It first predicts profiles of temperature, water vapor and CO2 partial pressures in plant canopies. Then from these predicted profiles, exchanges of sensible heat, water vapor and CO2 in each layer of the canopy are computed. Finally, canopy level fluxes are obtained by integrating these exchanges over the canopy. The model was tested comprehensively against measurements from a two-story boreal aspen forest in the southern study area of the boreal ecosystem-atmosphere study (BOREAS) project. Major findings obtained in this dissertation study can be summarized as follows: (1) The model can make accurate predictions for fluxes of radiative energy, sensible heat, water vapor and CO2 over this two-story forest, and profiles and diurnal patterns of air temperature, water vapor partial pressure and CO2 concentration within and just above the canopy. (2) Energy and mass exchanges in this boreal forest was largely controlled by the above story even through its LAI was smaller than that of the understory. However, to model energy and mass exchanges, it is not sufficient to consider leaves only, and contributions from other elements of the ecosystem can not be neglected in general. In particular, respiration of stems and soil is a significant part of the carbon budget for this forest and must be included in the study of ecosystem productivity. (3) Ecosystem elements can have significantly different roles in determining canopy sensible heat fluxes than in determining canopy evapotranspiration or CO2 assimilation. For example, the understory had a much bigger role in contributing to the fluxes of H2O and CO2 than in contributing to the sensible heat flux. In addition, their roles may change from nighttime to daytime. (4) The results showed that scalar transfers in this boreal forest can be described by the revised localized near-field theory, and problems of soil-vegetation-atmosphere transfers can be solved through a system of non-linear equations.

Gu, Lianhong

55

Statistical modeling of global soil NOx emissions  

Microsoft Academic Search

On the basis of field measurements of NOx emissions from soils, we developed a statistical model to describe the influences of soil organic carbon (SOC) content, soil pH, land-cover type, climate, and nitrogen input on NOx emission. While also considering the effects of soil temperature, soil moisture change-induced pulse emission, and vegetation fire, we simulated NOx emissions from global soils

Xiaoyuan Yan; Toshimasa Ohara; Hajime Akimoto

2005-01-01

56

Soil and vegetation parameter uncertainty on future terrestrial carbon sinks  

NASA Astrophysics Data System (ADS)

We examine the role of the terrestrial carbon cycle in a changing climate at the centennial scale using an intermediate complexity Earth system climate model that includes the effects of dynamic vegetation and the global carbon cycle. We present a series of ensemble simulations to evaluate the sensitivity of simulated terrestrial carbon sinks to three key model parameters: (a) The temperature dependence of soil carbon decomposition, (b) the upper temperature limits on the rate of photosynthesis, and (c) the nitrogen limitation of the maximum rate of carboxylation of Rubisco. We integrated the model in fully coupled mode for a 1200-year spin-up period, followed by a 300-year transient simulation starting at year 1800. Ensemble simulations were conducted varying each parameter individually and in combination with other variables. The results of the transient simulations show that terrestrial carbon uptake is very sensitive to the choice of model parameters. Changes in net primary productivity were most sensitive to the upper temperature limit on the rate of photosynthesis, which also had a dominant effect on overall land carbon trends; this is consistent with previous research that has shown the importance of climatic suppression of photosynthesis as a driver of carbon-climate feedbacks. Soil carbon generally decreased with increasing temperature, though the magnitude of this trend depends on both the net primary productivity changes and the temperature dependence of soil carbon decomposition. Vegetation carbon increased in some simulations, but this was not consistent across all configurations of model parameters. Comparing to global carbon budget observations, we identify the subset of model parameters which are consistent with observed carbon sinks; this serves to narrow considerably the future model projections of terrestrial carbon sink changes in comparison with the full model ensemble.

Kothavala, Z.; Felzer, B. S.

2013-12-01

57

Soil phosphorus forms as quality indicators of soils under different vegetation covers  

Microsoft Academic Search

The type of vegetation cover determines the physicochemical and biological properties of the soil over which they are developing. The objective of this study was to determine the effect of different vegetation covers on the forms of soil phosphorus, in order to know which of these forms can be used as a soil quality indicator. The experimental area was located

María-Belén Turrión; Olga López; Francisco Lafuente; Rafael Mulas; César Ruipérez; Alberto Puyo

2007-01-01

58

Radar reflectivity of bare and vegetation-covered soil  

NASA Technical Reports Server (NTRS)

Radar sensitivity to soil moisture content has been investigated experimentally for bare and vegetation-covered soil using detailed spectral measurements obtained by a truck-mounted radar spectrometer in the 1-8 GHz band and by airborne scatterometer observations at 1.6, 4.75, and 13.3 GHz. It is shown that radar can provide quantitative information on the soil moisture content of both bare and vegetation-covered soil. The observed soil moisture is in the form of the soil matric potential or a related quantity such as the percent of field capacity. The depth of the monitored layer varies from 1 cm for very wet soil to about 15 cm for very dry soil.

Ulaby, F. T.; Dobson, M. C.; Bradley, G. A.

1981-01-01

59

Carbon Dynamics in Vegetation and Soils  

NASA Technical Reports Server (NTRS)

The overall goals of CD-08 team in Phase I were to quantify the contributions of different components of the carbon cycle to overall ecosystem carbon balance in Amazonian tropical forests and to undertake process studies at a number of sites along the eastern LBA transect to understand how and why these fluxes vary with site, season, and year. We divided this work into a number of specific tasks: (1) determining the average rate (and variability) of tree growth over the past 3 decades; (2) determining age demographics of tree populations, using radiocarbon to determine tree age; (3) assessing the rate of production and decomposition of dead wood debris; (4) determining turnover rates for organic matter in soils and the mean age of C respired from soil using radiocarbon measurements; and (5) comparing our results with models and constructing models to predict the potential of tropical forests to function as sources or sinks of C. This report summarizes the considerable progress made towards our original goals, which have led to increased understanding of the potential for central Amazon forests to act as sources or sinks of carbon with altered productivity. The overall picture of tropical forest C dynamics emerging from our Phase I studies suggests that the fraction of gross primary production allocated to growth in these forests is only 25-30%, as opposed to the 50% assumed by many ecosystem models. Consequent slow tree growth rates mean greater mean tree age for a given diameter, as reflected in our measurements and models of tree age. Radiocarbon measurements in leaf and root litter suggest that carbon stays in living tree biomass for several years up to a decade before being added to soils, where decomposition is rapid. The time lags predicted from 14C, when coupled with climate variation on similar time scales, can lead to significant interannual variation in net ecosystem C exchange.

Trumbore, Susan; Chambers, Jeffrey Q.; Camargo, Plinio; Martinelli, Luiz; Santos, Joaquim

2005-01-01

60

Salix vegetation filters for purification of waters and soils  

Microsoft Academic Search

During recent years it has become obvious that it is both environmentally and economically appropriate to use vegetation filters of short rotation willows (Salix spp.) to purify waters and soils. Swedish and Polish experiences of vegetation filter efficiencies have been demonstrated in several laboratory, field lysimeter and full-scale experiments. However, there are still many questions to be answered; for example,

K. L. Perttu; P. J. Kowalik

1997-01-01

61

Soil moisture and vegetation controls on evapotranspiration in a heterogeneous Mediterranean ecosystem on Sardinia, Italy  

Microsoft Academic Search

Micrometeorological measurements of evapotranspiration (ET) can be difficult to interpret and use for validating model calculations in the presence of land cover heterogeneity. Land surface fluxes, soil moisture ($\\\\theta$), and surface temperatures (Ts) data were collected by an eddy correlation-based tower located at the Orroli (Sardinia) experimental field (covered by woody vegetation, grass, and bare soil) from April 2003 to

Matteo Detto; Nicola Montaldo; John D. Albertson; Marco Mancini; Gaby Katul

2006-01-01

62

Soil, water, and vegetation conditions in south Texas  

NASA Technical Reports Server (NTRS)

The author has identified the following significant results. The best wavelengths in the 0.4 to 2.5 micron interval were determined for detecting lead toxicity and ozone damage, distinguishing succulent from woody species, and detecting silverleaf sunflower. A perpendicular vegetation index, a measure of the distance from the soil background line, in MSS 5 and MSS 7 data space, of pixels containing vegetation was developed and tested as an indicator of vegetation development and crop vigor. A table lookup procedure was devised that permits rapid identification of soil background and green biomass or phenological development in LANDSAT scenes without the need for training data.

Wiegand, C. L.; Gausman, H. W.; Leamer, R. W.; Richardson, A. J.; Everitt, J. H.; Gerbermann, A. H. (principal investigators)

1977-01-01

63

Microwave Backscatter Dependence on Surface Roughness, Soil Moisture, and Soil Texture: Part II-Vegetation-Covered Soil  

Microsoft Academic Search

Results are presented of an experimental investigation to determine the relationship between radar backscatter coefficient ¿° and soil moisture for vegetation-covered soil. These results extend a previous report which showed the experimental relationship between ¿° and soil moisture for bare soil [1]. It is shown that the highest correlation between ¿° and soil moisture is 0.92 for the combined response

Fawwaz Ulaby; Gerald Bradley; Myron Dobson

1979-01-01

64

Modeling Feedbacks Between Water and Vegetation in the Climate System  

NASA Technical Reports Server (NTRS)

Not only is water essential for life on earth, but life itself affects the global hydrologic cycle and consequently the climate of the planet. Whether the global feedbacks between life and the hydrologic cycle tend to stabilize the climate system about some equilibrium level is difficult to assess. We use a global climate model to examine how the presence of vegetation can affect the hydrologic cycle in a particular region. A control for the present climate is compared with a model experiment in which the Sahara Desert is replaced by vegetation in the form of trees and shrubs common to the Sahel region. A second model experiment is designed to identify the separate roles of two different effects of vegetation, namely the modified albedo and the presence of roots that can extract moisture from deeper soil layers. The results show that the presence of vegetation leads to increases in precipitation and soil moisture in western Sahara. In eastern Sahara, the changes are less clear. The increase in soil moisture is greater when the desert albedo is replaced by the vegetation albedo than when both the vegetation albedo and roots are added. The effect of roots is to withdraw water from deeper layers during the dry season. One implication of this study is that the insertion of vegetation into the Sahara modifies the hydrologic cycle so that the vegetation is more likely to persist than initially.

Miller, James R.; Russell, Gary L.; Hansen, James E. (Technical Monitor)

2001-01-01

65

On soil moisture–vegetation feedbacks and their possible effects on the dynamics of dryland ecosystems  

Microsoft Academic Search

Soil moisture is the environmental variable synthesizing the effect of climate, soil, and vegetation on the dynamics of water-limited ecosystems. Unlike abiotic factors (e.g., soil texture and rainfall regime), the control exerted by vegetation composition and structure on soil moisture variability remains poorly understood. A number of field studies in dryland landscapes have found higher soil water contents in vegetated

Paolo D'Odorico; Kelly Caylor; Gregory S. Okin; Todd M. Scanlon

2007-01-01

66

Influences of soil moisture and vegetation on convective precipitation forecasts over the United States Great Plains  

NASA Astrophysics Data System (ADS)

study investigates the influences of soil moisture and vegetation on 30 h convective precipitation forecasts using the Weather Research and Forecasting model over the United States Great Plains with explicit treatment of convection. North American Regional Reanalysis (NARR) data were used as initial and boundary conditions. We also used an adjusted soil moisture (uniformly adding 0.10 m3/m3 over all soil layers based on NARR biases) to determine whether using a simple observationally based adjustment of soil moisture forcing would provide more accurate simulations and how the soil moisture addition would impact meteorological parameters for different vegetation types. Current and extreme (forest and barren) land covers were examined. Compared to the current vegetation cover, the complete removal of vegetation produced substantially less precipitation, while conversion to forest led to small differences in precipitation. Adding 0.10 m3/m3 to the soil moisture with the current vegetation cover lowered the near surface temperature and increased the humidity to a similar degree as using a fully forested domain with no soil moisture adjustment. However, these temperature and humidity effects on convective available potential energy and moist enthalpy nearly canceled each other out, resulting in a limited precipitation response. Although no substantial changes in precipitation forecasts were found using the adjusted soil moisture, the similarity found between temperature and humidity forecasts using the increased soil moisture and those with a forested domain highlights the sensitivity of the model to soil moisture changes, reinforcing the need for accurate soil moisture initialization in numerical weather forecasting models.

Collow, Thomas W.; Robock, Alan; Wu, Wei

2014-08-01

67

Application of Soil and Vegetation Reflectance Spectra to Color and Color Infrared Photography,  

National Technical Information Service (NTIS)

Characterizing arid region soil and vegetation conditions from remotely sensed imagery can be limited by the small image tonal contrast between soil vegetation surfaces. Ground-level reflectance spectra of different soil surfaces can be highly variable ov...

J. P. Henley, M. B. Satterwhite

1987-01-01

68

Coupling the Soil-Vegetation-Atmosphere-Transfer Scheme ORCHIDEE to the agronomy model STICS to study the influence of croplands on the European carbon and water budgets  

Microsoft Academic Search

Agriculture is still accounted for in a very simplistic way in the land-surface models which are coupled to climate models, while the area it occupies will significantly increase in the next century according to future scenarios. In order to improve the representation of croplands in a Dynamic Global Vegetation Model named ORCHIDEE (which can be coupled to the IPSL1 climate

Nathalie de NOBLET-DUCOUDRÉa; Philippe Ciais; Nicolas Viovy; Nadine Brisson; Bernard Seguin; Alain Perrier

2004-01-01

69

QuickBird derived vegetation parameters for soil erosion risk assessment in an alpine catchment  

NASA Astrophysics Data System (ADS)

The focus of soil erosion research in the Alps has been in two categories: (i) on-site measurements which are rather small scale point measurements on selected plots often constrained to irrigation experiments or (ii) off-site quantification of sediment delivery at the outlet of the catchment. Results of both categories showed that an intact vegetation cover prevents soil loss. With the recent availability of high-resolution satellites such as IKONOS and QuickBird options for detecting and monitoring of vegetation parameters have increased. The aim of this study is to evaluate the usefulness of QuickBird derived vegetation parameters in soil erosion models by comparison to Cesium-137 (Cs-137) soil erosion estimates. The study site (67km2) is located in the Central Swiss Alps and is dominated by grasslands with strong anthropogenic influences due to farming for centuries. Linear spectral unmixing and supervised classification is applied to produce maps of fractional vegetation cover (FVC) for grasslands and detailed land-cover maps from QuickBird imagery. The maps are used to adapt the C factor, which accounts for land management in the Universal Soil Loss Equation (USLE). Further the data was introduced to the Pan-European Soil Erosion Risk Assessment (PESERA) model. Supervised land-cover classification yielded a total accuracy of 93.3%. Linear spectral unmixing of vegetation abundance showed a significant (at the 0.01 level) correlation to ground truth FVC. Both models yielded higher absolute soil erosion estimates and an improvement of spatial patterns when FVC and a detailed land-cover maps are considered. However, discrepancies between model estimates and Cs-137 erosion estimates remained, especially for the PESERA model. This is leading to the assumption that soil erosion processes not considered in the models, e.g. soil erosion caused by snow gliding, play a decisive role.

Meusburger, Katrin; Konz, Nadine; Schaub, Monika; Alewell, Christine

2010-05-01

70

A Vegetated Urban Canopy Model for Meteorological and Environmental Modelling  

Microsoft Academic Search

An urban canopy model is developed for use in mesoscale meteorological and environmental modelling. The urban geometry is\\u000a composed of simple homogeneous buildings characterized by the canyon aspect ratio (h\\/w) as well as the canyon vegetation characterized by the leaf aspect ratio (?\\u000a l\\u000a ) and leaf area density profile. Five energy exchanging surfaces (roof, wall, road, leaf, soil) are

Sang-Hyun Lee; Soon-Ung Park

2008-01-01

71

Vegetation dynamics and soil water balance in a water-limited Mediterranean ecosystem on Sardinia, Italy  

NASA Astrophysics Data System (ADS)

Mediterranean ecosystems are commonly heterogeneous savanna-like ecosystems, with contrasting plant functional types (PFTs, e.g. grass and woody vegetation) competing for water. Mediterranean ecosystems are also commonly characterized by strong inter-annual rainfall variability, which influences the distributions of PFTs that vary spatially and temporally. An extensive field campaign in a Mediterranean setting was performed with the objective to investigate interactions between vegetation dynamics, soil water budget and land-surface fluxes in a water-limited ecosystem. Also a vegetation dynamic model (VDM) is coupled to a 3-component (bare soil, grass and woody vegetation) Land surface model (LSM). The case study is in Orroli, situated in the mid-west of Sardegna within the Flumendosa river basin. The landscape is a mixture of Mediterranean patchy vegetation types: trees, including wild olives and cork oaks, different shrubs and herbaceous species. Land surface fluxes, soil moisture and vegetation growth were monitored during the May 2003 June 2006 period. Interestingly, hydrometeorological conditions of the monitored years strongly differ, with dry and wet years in turn, such that a wide range of hydrometeorological conditions can be analyzed. The coupled VDM-LSM model is successfully tested for the case study, demonstrating high model performance for the wide range of eco-hydrologic conditions. Results demonstrate also that vegetation dynamics are strongly influenced by the inter-annual variability of atmospheric forcing, with grass leaf area index changing significantly each spring season according to seasonal rainfall amount.

Montaldo, N.; Albertson, J. D.; Mancini, M.

2008-11-01

72

Linking soil biodiversity and vegetation: implications for a changing planet.  

PubMed

Soil biota are intimately tied to plant communities through herbivory and symbiosis and indirectly by the decomposition of dead organic plant material. Through both roots and aboveground organic material (e.g., leaves and wood), plants provide substantial inputs of organic matter to soil systems. Plants are the basis for most biotic soil food webs that comprise an enormous diversity of species whose multiple interactions function to help regulate nutrient cycling, which in turn influences plant growth. Many factors govern the biogeography of soil biota, including the physical and chemical properties of soil, climate, the composition and type of vegetation, and interactions with other soil biota. Despite awareness of factors influencing soil communities, no single factor allows predictions of soil animal diversity or distribution. However, research is showing that plants can have unique soil biotic communities. Degradation of soil, which removes predators and biotic regulation that occurs in less managed ecosystems, can result in increased pathogens and pests that affect humans, other animals and plants. Global changes such as land use, desertification, and soil pollution all have been shown to alter soil animal diversity and abundance. Because of our dependence on soils and plant production, studies linking soil biotic communities to primary productivity are needed to assure long-term soil sustainability. PMID:21613143

Sylvain, Zachary A; Wall, Diana H

2011-03-01

73

Natural and anthropogenic lead in soils and vegetables around Guiyang city, southwest China: a Pb isotopic approach.  

PubMed

Soils, vegetables and rainwaters from three vegetable production bases in the Guiyang area, southwest China, were analyzed for Pb concentrations and isotope compositions to trace its sources in the vegetables and soils. Lead isotopic compositions were not distinguishable between yellow soils and calcareous soils, but distinguishable among sampling sites. The highest (207)Pb/(206)Pb and (208)Pb/(206)Pb ratios were found for rainwaters (0.8547-0.8593 and 2.098-2.109, respectively), and the lowest for soils (0.7173-0.8246 and 1.766-2.048, respectively). The (207)Pb/(206)Pb and (208)Pb/(206)Pb ratios increased in vegetables in the order of rootsmodel for Pb in vegetables. Using deep soils and rainwaters as geogenic and anthropogenic end members in the mixing model, it was estimated that atmospheric Pb contributed 30-77% to total Pb for vegetable roots, 43-71% for stems, 72-85% for leaves, and 90% for capsicum fruits, whereas 10-70% of Pb in all vegetable parts was derived from soils. This research supports that heavy metal contamination in vegetables can result mainly from atmospheric deposition, and Pb isotope technique is useful for tracing the sources of Pb contamination in vegetables. PMID:22705869

Li, Fei-Li; Liu, Cong-Qiang; Yang, Yuan-Gen; Bi, Xiang-Yang; Liu, Tao-Ze; Zhao, Zhi-Qi

2012-08-01

74

Vegetation types alter soil respiration and its temperature sensitivity at the field scale in an estuary wetland.  

PubMed

Vegetation type plays an important role in regulating the temporal and spatial variation of soil respiration. Therefore, vegetation patchiness may cause high uncertainties in the estimates of soil respiration for scaling field measurements to ecosystem level. Few studies provide insights regarding the influence of vegetation types on soil respiration and its temperature sensitivity in an estuary wetland. In order to enhance the understanding of this issue, we focused on the growing season and investigated how the soil respiration and its temperature sensitivity are affected by the different vegetation (Phragmites australis, Suaeda salsa and bare soil) in the Yellow River Estuary. During the growing season, there were significant linear relationships between soil respiration rates and shoot and root biomass, respectively. On the diurnal timescale, daytime soil respiration was more dependent on net photosynthesis. A positive correlation between soil respiration and net photosynthesis at the Phragmites australis site was found. There were exponential correlations between soil respiration and soil temperature, and the fitted Q10 values varied among different vegetation types (1.81, 2.15 and 3.43 for Phragmites australis, Suaeda salsa and bare soil sites, respectively). During the growing season, the mean soil respiration was consistently higher at the Phragmites australis site (1.11 µmol CO2 m(-2) s(-1)), followed by the Suaeda salsa site (0.77 µmol CO2 m(-2) s(-1)) and the bare soil site (0.41 µmol CO2 m(-2) s(-1)). The mean monthly soil respiration was positively correlated with shoot and root biomass, total C, and total N among the three vegetation patches. Our results suggest that vegetation patchiness at a field scale might have a large impact on ecosystem-scale soil respiration. Therefore, it is necessary to consider the differences in vegetation types when using models to evaluate soil respiration in an estuary wetland. PMID:24608636

Han, Guangxuan; Xing, Qinghui; Luo, Yiqi; Rafique, Rashad; Yu, Junbao; Mikle, Nate

2014-01-01

75

Vegetation Types Alter Soil Respiration and Its Temperature Sensitivity at the Field Scale in an Estuary Wetland  

PubMed Central

Vegetation type plays an important role in regulating the temporal and spatial variation of soil respiration. Therefore, vegetation patchiness may cause high uncertainties in the estimates of soil respiration for scaling field measurements to ecosystem level. Few studies provide insights regarding the influence of vegetation types on soil respiration and its temperature sensitivity in an estuary wetland. In order to enhance the understanding of this issue, we focused on the growing season and investigated how the soil respiration and its temperature sensitivity are affected by the different vegetation (Phragmites australis, Suaeda salsa and bare soil) in the Yellow River Estuary. During the growing season, there were significant linear relationships between soil respiration rates and shoot and root biomass, respectively. On the diurnal timescale, daytime soil respiration was more dependent on net photosynthesis. A positive correlation between soil respiration and net photosynthesis at the Phragmites australis site was found. There were exponential correlations between soil respiration and soil temperature, and the fitted Q10 values varied among different vegetation types (1.81, 2.15 and 3.43 for Phragmites australis, Suaeda salsa and bare soil sites, respectively). During the growing season, the mean soil respiration was consistently higher at the Phragmites australis site (1.11 µmol CO2 m?2 s?1), followed by the Suaeda salsa site (0.77 µmol CO2 m?2 s?1) and the bare soil site (0.41 µmol CO2 m?2 s?1). The mean monthly soil respiration was positively correlated with shoot and root biomass, total C, and total N among the three vegetation patches. Our results suggest that vegetation patchiness at a field scale might have a large impact on ecosystem-scale soil respiration. Therefore, it is necessary to consider the differences in vegetation types when using models to evaluate soil respiration in an estuary wetland. PMID:24608636

Han, Guangxuan; Xing, Qinghui; Luo, Yiqi; Rafique, Rashad; Yu, Junbao; Mikle, Nate

2014-01-01

76

Effect of a coupled soil water–plant gas exchange on forest energy fluxes: Simulations with the coupled vegetation–boundary layer model HIRVAC  

Microsoft Academic Search

Long-living plant communities such as forests reduce their transpiration by closing and opening the leaf stomata as a common strategy to save water in dry periods. Meteorological models including vegetation should consider this mechanism to simulate realistic water transport from the plant to the atmosphere. Results of the German network project VERTIKO showed that commonly used meso-models such as Lokalmodell

Björn Fischer; Valeri Goldberg; Christian Bernhofer

2008-01-01

77

A multi-frequency radiometric measurement of soil moisture content over bare and vegetated fields  

NASA Technical Reports Server (NTRS)

An experiment on soil moisture remote sensing was conducted during July to September 1981 on bare, grass, and alfalfa fields at frequencies of 0.6, 1.4, 5.0, and 10.6 GHz with radiometers mounted on mobile towers. The results confirm the frequency dependence of sensitivity reduction due to the presence of vegetation cover. For the type of vegetated fields reported here, the vegetation effect is appreciable even at 0.6 GHz. Measurements over bare soil show that when the soil is wet, the measured brightness temperature is lowest at 5.0 GHz and highest at 0.6 GHz, a result contrary to the expectation based on the estimated dielectric permittivity of soil-water mixtures and the current radiative transfer model in that frequency range.

Wang, J. R.; Schmugge, T. J.; Gould, W. I.; Glazar, W. S.; Fuchs, J. E.; Mcmurtrey, J. E., III

1982-01-01

78

Vegetation-soil spectral mixture analysis  

Microsoft Academic Search

This paper describes the measurement and analysis of laboratory reflectance of green leaf and soil mixtures. Various combinations of leaf area index and percent cover were generated by stacking leaf discs over a dry soil background. Reflectance spectra (400-2500 nm) of these miniature pixels were measured with a spectroradiometer (Fieldspec FR) under laboratory conditions. The measured spectra were then compared

Bisun Datt; Michelle Paterson

2000-01-01

79

SIR-C Measurements of Soil Moisture, Vegetation and Surface Roughness and their Hydrological Application  

NASA Technical Reports Server (NTRS)

The objectives of the study are: (1) Analysis of SIR-C/X-SAR response to soil moisture, vegetation and surface roughness and development of an algorithm to retrieve these parameters; (2) Combination of the visible and near-infrared data and the SIR-C/X-SAR data to improve the range and accuracy of vegetation classification; (3) Testing of theoretical models for microwave propagation with SIR-C/X-SAR and microwave radiometric measurements over rough surfaces; and (4) Evaluation of a water balance model using SIR-C/X-SAR derived soil moisture values and other ancillary data. Progress, significant results and future plans are presented.

Wang, James R.

1996-01-01

80

Combined effect of soil erosion and climate change induces abrupt changes in soil and vegetation properties in semiarid Mediterranean shrublands.  

NASA Astrophysics Data System (ADS)

Semiarid Mediterranean ecosystems are experiencing major alterations as a result of the complex interactions between climatic fluctuations and disturbances caused by human activities. Future scenarios of global change forecast a rapid degradation of these ecosystems, with a reduction of their functionality, as a result of changes in relevant vegetation and soil properties. Some theoretical models indicate that these ecosystems respond non-linearly to regular variations in the external conditions, with an abrupt shift when conditions approach a certain critical level or threshold. Considering these predictions, there is an urgent need to know the effects that these alterations might have on semi-arid ecosystems and their components. In this study, we aim at analyzing the consequences of climate change and increasing soil erosion on soil and vegetation properties and the functional dynamics of semiarid Mediterranean shrublands. We predict that the combined effect of both drivers will be additive or synergistic, increasing the negative effects of each one. We compared vegetation and soil properties of flat areas (low erosion) and steep hillslopes (high erosion) in two climatic areas (484 mm and 10.3°C, and 368mm and 11.9°C, respectively) that reproduce the predicted climate change in temperature and precipitation for the next 40 years. Species richness, vegetal cover, plant life-form composition were determined in 20 m2 plots and soil was sampled in the same plots to determine bulk density, aggregate stability, fertility and water holding capacity. All soil and vegetation properties were negatively affected by soil erosion and climate change. However, contrary to our hypothesis, the joined effect of both drivers on all soil and vegetation properties was antagonistic, except for the vegetal cover that showed an additive response to their interaction. Our results evidence that soil erosion affects more negatively the soil and vegetation properties in the cooler and wetter climatic area than in the warmer and drier one, and support moreover the idea that a functional threshold has been crossed between the two climatic areas.

Bochet, Esther; García-Fayos, Patricio

2013-04-01

81

Vegetation dynamics and soil water balance in a water-limited Mediterranean ecosystem on Sardinia, Italy  

NASA Astrophysics Data System (ADS)

Mediterranean ecosystems are commonly heterogeneous savanna-like ecosystems, with contrasting plant functional types (PFTs, e.g., grass and woody vegetation) competing for the water use. Mediterranean ecosystems are also commonly characterized by strong inter-annual rainfall variability, which influences the distributions of PFTs that vary spatially and temporally. With the objective to investigate interactions between vegetation dynamics, soil water budget and land-surface fluxes in a water-limited ecosystem, an extensive field campaign in a Mediterranean setting was performed. Also a vegetation dynamic model (VDM) is coupled to a 3-component (bare soil, grass and woody vegetation) Land surface model (LSM). The case study is in Orroli, situated in the mid-west of Sardegna within the Flumendosa river basin. The landscape is a mixture of Mediterranean patchy vegetation types: trees, including wild olives and cork oaks, different shrubs and herbaceous species. Land surface fluxes, soil moisture and vegetation growth were monitored during the May 2003-June 2006 period. Interestingly, hydrometeorological conditions of the monitored years strongly differ, with dry and wet years in turn, such that a wide range of hydrometeorological conditions can be analyzed. The coupled VDM-LSM model is successfully tested for the case study, demonstrating high model performance for the wide range of eco-hydrologic conditions. The use of the VDM in the LSM is demonstrated to be essential when studying the climate-soil-vegetation interactions of these water-limited ecosystems. Results demonstrate also that vegetation dynamics are strongly influenced by the inter-annual variability of atmospheric forcing, with grass leaf area index changing significantly each spring season according to seasonal rainfall amount.

Montaldo, N.; Albertson, J. D.; Mancini, M.

2008-01-01

82

Modeling of the interactions between forest vegetation, disturbances, and sediment yields  

Microsoft Academic Search

The controls of forest vegetation, wildfires, and harvest vegetation disturbances on the frequency and magnitude of sediment delivery from a small watershed (?3.9 km2) in the Idaho batholith are investigated through numerical modeling. The model simulates soil development based on continuous bedrock weathering and the divergence of diffusive sediment transport on hillslopes. Soil removal is due to episodic gully erosion,

Erkan Istanbulluoglu; David G. Tarboton; Robert T. Pack; Charles H. Luce

2004-01-01

83

Optimum vegetation characteristics, assimilation, and transpiration during a dry season: 1. Model description  

Microsoft Academic Search

This paper presents a model to predict optimum vegetation characteristics in water stressed conditions. Starting point is the principle of homeostasis of water flow through the soil-vegetation-atmosphere continuum. Combining this with a biochemical model for photosynthesis, a relationship between photosynthetic capacity, stomatal regulation, and hydraulic properties of the vegetation is derived. Optimum photosynthetic capacity and internal carbon dioxide concentration are

C. van der Tol; A. G. C. A. Meesters; A. J. Dolman; M. J. Waterloo

2008-01-01

84

An Intercomparison of Vegetation Products from Satellite-based Observations used for Soil Moisture Retrievals  

NASA Astrophysics Data System (ADS)

Vegetation and its water content affect active and passive microwave soil moisture retrievals and need to be taken into account in such retrieval methodologies. This study compares the vegetation parameterisation that is used in the TU-Wien soil moisture retrieval algorithm to other vegetation products, such as the Vegetation Optical Depth (VOD), Net Primary Production (NPP) and Leaf Area Index (LAI). When only considering the retrieval algorithm for active microwaves, which was developed by the TU-Wien, the effect of vegetation on the backscattering coefficient is described by the so-called slope [1]. The slope is the first derivative of the backscattering coefficient in relation to the incidence angle. Soil surface backscatter normally decreases quite rapidly with the incidence angle over bare or sparsely vegetated soils, whereas the contribution of dense vegetation is fairly uniform over a large range of incidence angles. Consequently, the slope becomes less steep with increasing vegetation. Because the slope is a derivate of noisy backscatter measurements, it is characterised by an even higher level of noise. Therefore, it is averaged over several years assuming that the state of the vegetation doesn't change inter-annually. The slope is compared to three dynamic vegetation products over Australia, the VOD, NPP and LAI. The VOD was retrieved from AMSR-E passive microwave data using the VUA-NASA retrieval algorithm and provides information on vegetation with a global coverage of approximately every two days [2]. LAI is defined as half the developed area of photosynthetically active elements of the vegetation per unit horizontal ground area. In this study LAI is used from the Geoland2 products derived from SPOT Vegetation*. The NPP is the net rate at which plants build up carbon through photosynthesis and is a model-based estimate from the BiosEquil model [3, 4]. Results show that VOD and slope correspond reasonably well over vegetated areas, whereas in arid areas, where the microwave signals mostly stem from the soil surface and deeper soil layers, they are negatively correlated. A second comparison of monthly values of both vegetation parameters to modelled NPP data shows that particularly over dry areas the VOD corresponds better to the NPP, with r=0.79 for VOD-NPP and r=-0.09 for slope-NPP. 1. Wagner, W., et al., A Study of Vegetation Cover Effects on ERS Scatterometer Data. IEEE Transactions on Geoscience and Remote Sensing, 1999. 37(2): p. 938-948. 2. Owe, M., R. de Jeu, and J. Walker, A methodology for surface soil moisture and vegetation optical depth retrieval using the microwave polarization difference index. Geoscience and Remote Sensing, IEEE Transactions on, 2001. 39(8): p. 1643-1654. 3. Raupach, M.R., et al., Balances of Water, Carbon, Nitrogen and Phosphorus in Australian Landscapes: (1) Project Description and Results, 2001, Sustainable Minerals Institute, CSIRO Land and Water. 4. Raupach, M.R., et al., Balances of Water, Carbon, Nitrogen and Phosporus in Australian Landscapes: (2) Model Formulation and Testing, 2001, Sustainable Minerals Institute, CSIRO Land and Water. * These products are the joint property of INRA, CNES and VITO under copyright of Geoland2. They are generated from the SPOT VEGETATION data under copyright CNES and distribution by VITO.

Vreugdenhil, Mariette; de Jeu, Richard; Wagner, Wolfgang; Dorigo, Wouter; Hahn, Sebastian; Bloeschl, Guenter

2013-04-01

85

Vegetation on the Soil Infiltration System Treating Livestock Wastewater  

NASA Astrophysics Data System (ADS)

In the overland flow wastewater treatments and the constructed wetlands, the purification by soil infiltration units is enhanced using vegetation. However, wetland plants (i.e. cattail (Typha latifolia)) and trees, rather than agronomic crops, have been used in conventional systems. We carried out laboratory-scale soil infiltration experiments using two forage crops, tall fescue (Festuca araundinacea) and white clover (Trifolium repens) while using livestock wastewater for irrigation. The purpose of the study was to clarify the amount of accumulation of available phosphorus and exchangeable cations in the soil and its effect on the plant growth. The application of livestock wastewater increased available phosphorus, and exchangeable potassium and sodium in the upper soil. The soil sodification, examined based on exchangeable sodium ratio and plant growth, was not very significant after 10 months of livestock wastewater application. Growing forage crops on the soil infiltration system may be a promising technology to improve crop production and treatment efficacy.

Sakurai, Shinji; Fujikawa, Yoko; Fukui, Masami; Hamasaki, Tastuhide; Sugahara, Masataka

86

Modelling the Congo basin ecosystems with a dynamic vegetation model  

NASA Astrophysics Data System (ADS)

The scarcity of field observations in some parts of the world makes difficult a deep understanding of some ecosystems such as humid tropical forests in Central Africa. Therefore, modelling tools are interesting alternatives to study those regions even if the lack of data often prevents sharp calibration and validation of the model projections. Dynamic vegetation models (DVMs) are process-based models that simulate shifts in potential vegetation and its associated biogeochemical and hydrological cycles in response to climate. Initially run at the global scale, DVMs can be run at any spatial scale provided that climate and soil data are available. In the framework of the BIOSERF project ("Sustainability of tropical forest biodiversity and services under climate and human pressure"), we use and adapt the CARAIB dynamic vegetation model (Dury et al., iForest - Biogeosciences and Forestry, 4:82-99, 2011) to study the Congo basin vegetation dynamics. The field campaigns have notably allowed the refinement of the vegetation representation from plant functional types (PFTs) to individual species through the collection of parameters such as the specific leaf area or the leaf C:N ratio of common tropical tree species and the location of their present-day occurrences from literature and available database. Here, we test the model ability to reproduce the present spatial and temporal variations of carbon stocks (e.g. biomass, soil carbon) and fluxes (e.g. gross and net primary productivities (GPP and NPP), net ecosystem production (NEP)) as well as the observed distribution of the studied species over the Congo basin. In the lack of abundant and long-term measurements, we compare model results with time series of remote sensing products (e.g. vegetation leaf area index (LAI), GPP and NPP). Several sensitivity tests are presented: we assess consecutively the impacts of the level at which the vegetation is simulated (PFTs or species), the spatial resolution and the initial land cover (potential or human-induced). First, we show simulations over the whole Congo basin at a 0.5° spatial resolution. Then, we present high-resolution simulations (1 km) carried out over different areas of the Congo basin, notably the DRC part of the WWF Lake Tele - Lake Tumba Landscape. Studied in the BIOSERF project, this area is characterized by a forest-savannah mosaic but also by swamp and flooded forest. In addition, forward transient projections of the model driven with the outputs of about thirty global climate models (GCMs) from the new Coupled Model Intercomparison Project Phase 5 (CMIP5) will permit to outline the likely response of carbon pools to changing climate over the Congo basin during the 21th century.

Dury, Marie; Hambuckers, Alain; Trolliet, Franck; Huynen, Marie-Claude; Haineaux, Damien; Fontaine, Corentin M.; Fayolle, Adeline; François, Louis

2014-05-01

87

Heterogeneity of Soils and Vegetation in an Eastern Amazonian  

E-print Network

Heterogeneity of Soils and Vegetation in an Eastern Amazonian Rain Forest: Implications for Scaling, Massachusetts 02543, USA; 2 Instituto Nacional de Pesquisas Espaciais, Sa~o Jose´ dos Campos, SP, Brazil; and 3 Institute of Ecology and Resource Management, University of Edinburgh, Edinburgh EH9 3JU, Scotland ABSTRACT

88

Soil and Vegetation Management: Keys to Water Conservation on Rangeland  

E-print Network

The amount of water that soaks into the soil largely determines plant productivity. We can manage and conserve water where and when it falls, and by controlling the kind of vegetation we can make the fullest use of rain water. This publication...

Schuster, Joseph L.

2001-01-11

89

Wetland Soils and Vegetation, Arctic Foothills, Alaska.  

National Technical Information Service (NTIS)

Analyses of relationships between hydric soils and wetland plant species were made at a 22 cu km site in the northern foothills of the Brooks Range, Alaska, as part of a cooperative effort between the FWS and SCS to develop methods for field identificatio...

M. D. Walker, D. A. Walker, K. R. Everett

1989-01-01

90

On soil moisture–vegetation feedbacks and their possible effects on the dynamics of dryland ecosystems  

Microsoft Academic Search

(1) Soil moisture is the environmental variable synthesizing the effect of climate, soil, and vegetation on the dynamics of water-limited ecosystems. Unlike abiotic factors (e.g., soil texture and rainfall regime), the control exerted by vegetation composition and structure on soil moisture variability remains poorly understood. A number of field studies in dryland landscapes have found higher soil water contents in

Paolo D'Odorico; Kelly Caylor; Gregory S. Okin; Todd M. Scanlon

2007-01-01

91

Investigation of soil influences in AVHRR red and near-infrared vegetation index imagery  

NASA Technical Reports Server (NTRS)

The effects of soil optical properties on vegetation index imagery are analyzed with ground-based spectral measurements and both simulated and actual AVHRR data from the NOAA satellites. Soil effects on vegetation indices were divided into primary variations associated with the brightness of bare soils, secondary variations attributed to 'color' differences among bare soils, and soil-vegetation spectral mixing. Primary variations were attributed to shifts in the soil line owing to atmosphere or soil composition. Secondary soil variance was responsible for the Saharan desert 'artefact' areas of increased vegetation index response in AVHRR imagery.

Huete, A. R.; Tucker, C. J.

1991-01-01

92

Reorganization of vegetation, hydrology and soil carbon after permafrost degradation across heterogeneous boreal landscapes  

E-print Network

Reorganization of vegetation, hydrology and soil carbon after permafrost degradation across of vegetation, hydrology and soil carbon after permafrost degradation across heterogeneous boreal landscapes M of ecosystems across boreal landscapes, successional changes after disturbance and complicated permafrost

93

Derivation of a global soil moisture and vegetation database from passive microwave signals  

NASA Astrophysics Data System (ADS)

A series of validation studies for a recently developed soil moisture retrieval algorithm is presented. The approach is largely theoretical, and uses a non-linear iterative optimisation procedure to solve for soil moisture and vegetation optical depth with a radiative transfer model from satellite microwave observations. The new theoretical approach is not dependent on field observations of soil moisture or canopy biophysical measurements and can be used at any wavelength in the microwave region. Details of the model and its development are discussed. Satellite retrievals were derived from 6.6 GHz Nimbus/SMMR brightness temperatures, and were validated with soil moisture data sets from the U.S., Mongolia, and Turkmenistan. Time series of the satellite-derived surface moisture compared well with the available ground observations and precipitation data. The vegetation optical depth showed similar seasonal patterns as the NDVI.

De Jeu, Richard A. M.; Owe, Manfred

2003-03-01

94

Error assessment in decision-tree models applied to vegetation analysis  

Microsoft Academic Search

Methods were developed to evaluate the performance of a decision-tree model used to predict landscape-level patterns of potential forest vegetation in central New York State. The model integrated environmental databases and knowledge on distribution of vegetation. Soil and terrain decision-tree variables were derived by processing state-wide soil geographic databases and digital terrain data. Variables used as model inputs were soil

Henry Lynn; Charles L. Mohler; Stephen D. DeGloria; Charles E. McCulloch

1995-01-01

95

Canopy reflectance modelling of semiarid vegetation  

NASA Technical Reports Server (NTRS)

Three different types of remote sensing algorithms for estimating vegetation amount and other land surface biophysical parameters were tested for semiarid environments. These included statistical linear models, the Li-Strahler geometric-optical canopy model, and linear spectral mixture analysis. The two study areas were the National Science Foundation's Jornada Long Term Ecological Research site near Las Cruces, NM, in the northern Chihuahuan desert, and the HAPEX-Sahel site near Niamey, Niger, in West Africa, comprising semiarid rangeland and subtropical crop land. The statistical approach (simple and multiple regression) resulted in high correlations between SPOT satellite spectral reflectance and shrub and grass cover, although these correlations varied with the spatial scale of aggregation of the measurements. The Li-Strahler model produced estimated of shrub size and density for both study sites with large standard errors. In the Jornada, the estimates were accurate enough to be useful for characterizing structural differences among three shrub strata. In Niger, the range of shrub cover and size in short-fallow shrublands is so low that the necessity of spatially distributed estimation of shrub size and density is questionable. Spectral mixture analysis of multiscale, multitemporal, multispectral radiometer data and imagery for Niger showed a positive relationship between fractions of spectral endmembers and surface parameters of interest including soil cover, vegetation cover, and leaf area index.

Franklin, Janet

1994-01-01

96

Extraction of soil and vegetation parameters from high resolution bi-directional reflectance spectra  

NASA Technical Reports Server (NTRS)

High spectral resolution reflectance spectra were collected over a semi-desert grassland at both dry and wet season periods. Spectral reflectance measurements were made from several viewing angles at both low and high solar zenith angles. A mixture model was used to separate and extract green vegetation from dry/dead vegetation and soil. The extracted vegetation signal varied greatly with view and sun angle variations such that off-nadir viewing and illuminating angles resulted in the highest vegetation loadings. These variations were normalized with cosine functions for both sun and view angle. These results offer a methodology for standardizing multi-temporal and multi-angular satellite measurements of vegetation activity.

Huete, A. R.

1992-01-01

97

Author's personal copy Soil and vegetation as the determinants of lake nitrogen  

E-print Network

Author's personal copy Soil and vegetation as the determinants of lake nitrogen concentrations, to the sediment and by denitrification. Forest vegetation affects lake nitrogen through its impact on soil 12 April 2007 Keywords: Lake Nitrogen Vegetation Soil Forest Watershed a b s t r a c t This study

Mazumder, Asit

98

Soil moisture and vegetation controls on evapotranspiration in a heterogeneous Mediterranean ecosystem on Sardinia, Italy  

NASA Astrophysics Data System (ADS)

Micrometeorological measurements of evapotranspiration (ET) can be difficult to interpret and use for validating model calculations in the presence of land cover heterogeneity. Land surface fluxes, soil moisture (?), and surface temperatures (Ts) data were collected by an eddy correlation-based tower located at the Orroli (Sardinia) experimental field (covered by woody vegetation, grass, and bare soil) from April 2003 to July 2004. Two Quickbird high-resolution images (summer 2003 and spring 2004) were acquired for depicting the contrasting land cover components. A procedure is presented for estimating ET in heterogeneous ecosystems as the residual term of the energy balance using Ts observations, a two-dimensional footprint model, and the Quickbird images. Two variations on the procedure are successfully implemented: a proposed two-source random model (2SR), which treats the heat sources of each land cover component separately but computes the bulk heat transfer coefficient as spatially homogeneous, and a common two-source tile model. For 2SR, new relationships between the interfacial transfer coefficient and the roughness Reynolds number are estimated for the two bare soil-woody vegetation and grass-woody vegetation composite surfaces. The ET versus ? relationships for each land cover component were also estimated, showing that that the woody vegetation has a strong tolerance to long droughts, transpiring at rates close to potential for even the driest conditions. Instead, the grass is much less tolerant to ? deficits, and the switch from grass to bare soil following the rainy season had a significant impact on ET.

Detto, Matteo; Montaldo, Nicola; Albertson, John D.; Mancini, Marco; Katul, Gaby

2006-08-01

99

Soil Moisture and Vegetation Water Content Retrieval Using QuikSCAT data  

NASA Astrophysics Data System (ADS)

Future water resources are a critical societal impact of climate change and hydrological cycles. Current climate models uncertainties result in disagreement on whether there will be more or less water. On a global scale, there are important gaps in knowledge of where water is stored, where it is going, and how fast it is moving. Soil moisture and vegetation water content are key environmental variables on evaporation and transpiration at the land-atmosphere boundary. Radar remote sensing helps to improve our estimate of water resources globally and temporally. SMAP (Soil Moisture Active Passive) and SWOT (Surface Water Ocean Topography) are the two future NASA missions to monitor water resources and their variation spatially and temporally. Li et al. (Li. Et al. 2010) developed a physically based six-channel algorithm, which uses dual-polarization Windsat passive microwave data to retrieve soil moisture and vegetation water content. We use the retrieved soil moisture and vegetation water content using Windsat descending pass (around 6AM), and also simultaneous collocated QuikSCAT dual-polarization backscattered power to estimate different parameters of the land. The backscattered power can be written as ?pi = fbare ?grp(smi,m) + (1-fbare){ Ap ( 1-exp(-Bp Wi) ) + Cp Wi? exp(-Bp Wi) } where ?pi is the ith QuikSCAT backscatter power with polarization p, fbare is the bare surface fraction, m is soil rms. slope, ?grp is the ground backscattered power with polarization p, and smi and Wi are the retrieved soil moisture and vegetation water content using Windsat data. Ap, Cp, and Bp are the backscattering contributions from vegetation volume, canopy ground interaction, and attenuation of the canopy with polarization p, respectively. We assume all parameters remain constant for each month of different years compared to soil moisture and vegetation water content. Therefore for each point, we have 10 unknowns for HH and VV polarizations. We collect all observations of simultaneous QuikSCAT and retrieved smi and Wi for each location during the summer season and retrieve all those 10 parameters. We show how the retrieved global bare surface fraction compares well with the existing maps. These parameters are then used to estimate the soil moisture and vegetation water content for summer days of a different year using QuikSCAT backscattered power and formula above. Although QuikSCAT satellite is designed to capture sea-winds, it also collects data over land globally almost every day. Therefore, we can generate a global map of soil moisture and vegetation water content daily. We compare the retrieved values with Li et al.'s retrieval values.

Oveisgharan, S.; Haddad, Z. S.; Turk, J.; Li, L.; Rodriguez, E.

2013-05-01

100

Distinguishing vegetation from soil background information. [by gray mapping of Landsat MSS data  

NASA Technical Reports Server (NTRS)

In aircraft and satellite multispectral scanner data, soil background signals are superimposed on or intermingled with information about vegetation. A procedure which accounts for soil background would, therefore, make a considerable contribution to an operational use of Landsat and other spectral data for monitoring the productivity of range, forest, and crop lands. A description is presented of an investigation which was conducted to obtain information for the development of such a procedure. The investigation included a study of the soil reflectance that supplies the background signal of vegetated surfaces. Landsat data as recorded on computer compatible tapes were used in the study. The results of the investigation are discussed, taking into account a study reported by Kauth and Thomas (1976). Attention is given to the determination of Kauth's plane of soils, sun angle effects, vegetation index modeling, and the evaluation of vegetation indexes. Graphs are presented which show the results obtained with a gray mapping technique. The technique makes it possible to display plant, soil, water, and cloud conditions for any Landsat overpass.

Richardson, A. J.; Wiegand, C. L.

1977-01-01

101

Spatio-temporal soil moisture patterns across gradients of vegetation and topography  

NASA Astrophysics Data System (ADS)

Soil moisture dynamics control hydrological processes on various scales: changes in local water storage and potential activation of preferential flow paths influence connectivity and runoff from hillslopes and ultimately the discharge response of the stream. The spatio-temporal patterns of soil moisture, however, are dependent on a combination of local parameters such as soil type, vegetation and topography as well as meteorological conditions, antecedent moisture and seasonality. In an integrative monitoring study carried out within the CAOS observatory in Luxemburg (http://www.caos-project.de/), soil moisture was measured at 21 sites with 3 soil moisture profiles each. These sites include grassland as well as forest on the one hand and cover different hillslope positions on the other hand. This setup allows us to study both vegetation and topographic effects. The spatio-temporal patterns of soil moisture were analysed using two approaches: 1) we examined temporal persistence of soil moisture patterns with rank stability plots and addressed the variability within and between sites for contrasting meteorological conditions. 2) In a next step we focused on specific hydrologic events: two periods during summer recession were distinguished, first the drying out of the soils during a period of no precipitation, but also the continuing decline even after summer rains have started. Furthermore, the soil moisture response to three different rainfall events was examined, varying in intensity and antecedent moisture conditions. The emerging contrasts in patterns were put into context of site-specific characteristics such as vegetation and topographical position to identify controls on soil moisture dynamics for our range of sites. Ultimately, linking similarity in soil moisture response in landscapes to these controls can elucidate the hydrological functioning of landscape units and thus facilitate modelling efforts.

Hassler, Sibylle; Weiler, Markus; Blume, Theresa

2014-05-01

102

Modeling vegetation controls on fluvial morphological trajectories  

NASA Astrophysics Data System (ADS)

The role of riparian vegetation in shaping river morphology is widely recognized. The interaction between vegetation growth and riverbed evolution is characterized by complex nonlinear feedbacks, which hinder direct estimates of the role of key elements on the morphological evolutionary trajectories of gravel bed rivers. Adopting a simple theoretical framework, we develop a numerical model which couples hydromorphodynamics with biomass dynamics. We perform a sensitivity analysis considering several parameters as flood intensity, type of vegetation, and groundwater level. We find that the inclusion of vegetation determines a threshold behavior, identifying two possible equilibrium configurations: unvegetated versus vegetated bars. Stable vegetation patterns can establish only under specific conditions, which depend on the different environmental and species-related characteristics. From a management point of view, model results show that relatively small changes in water availability or species composition may determine a sudden shift between dynamic unvegetated conditions to more stable, vegetated rivers.

Bertoldi, Walter; Siviglia, Annunziato; Tettamanti, Stefano; Toffolon, Marco; Vetsch, David; Francalanci, Simona

2014-10-01

103

Development of the IAP Dynamic Global Vegetation Model  

NASA Astrophysics Data System (ADS)

The IAP Dynamic Global Vegetation Model (IAP-DGVM) has been developed to simulate the distribution and structure of global vegetation within the framework of Earth System Models. It incorporates our group's recent developments of major model components such as the shrub sub-model, establishment and competition parameterization schemes, and a process-based fire parameterization of intermediate complexity. The model has 12 plant functional types, including seven tree, two shrub, and three grass types, plus bare soil. Different PFTs are allowed to coexist within a grid cell, and their state variables are updated by various governing equations describing vegetation processes from fine-scale biogeophysics and biogeochemistry, to individual and population dynamics, to large-scale biogeography. Environmental disturbance due to fire not only affects regional vegetation competition, but also influences atmospheric chemistry and aerosol emissions. Simulations under observed atmospheric conditions showed that the model can correctly reproduce the global distribution of trees, shrubs, grasses, and bare soil. The simulated global dominant vegetation types reproduce the transition from forest to grassland (savanna) in the tropical region, and from forest to shrubland in the boreal region, but overestimate the region of temperate forest.

Zeng, Xiaodong; Li, Fang; Song, Xiang

2014-05-01

104

Estimating photosynthetic vegetation, non-photosynthetic vegetation and bare soil fractions using Landsat and MODIS data: Effects of site heterogeneity, soil properties and land cover  

NASA Astrophysics Data System (ADS)

Vegetation fractional cover is a key indicator for land management monitoring, both in pastoral and agricultural settings. Maintaining adequate vegetation cover protects the soil from the effects of water and wind erosion and also ensures that carbon is returned to soil through decomposition. Monitoring vegetation fractional cover across large areas and continuously in time needs good remote sensing techniques underpinned by high quality ground data to calibrate and validate algorithms. In this study we used Landsat and MODIS reflectance data together with field measurements from 1476 observations across Australia to produce estimates of vegetation fractional cover using a linear unmixing technique. Specifically, we aimed at separating fractions of photosynthetic vegetation (PV), non-photosynthetic vegetation (NPV) and bare soil (B). We used Landsat reflectance averaged over a 3x3 pixel window representing the area actually measured on the ground and also a 'degraded' Landsat reflectance 40x40 pixel window to simulate the effect of a coarser sensor. Using these two Landsat reflectances we quantified the heterogeneity of each site. We used data from two MODIS-derived reflectance products: the Nadir BRDF-Adjusted surface Reflectance product (MCD43A4) and the MODIS 8-day surface reflectance (MOD09A1). We derived endmembers from the data and estimated fractional cover using a linear unmixing technique. Log transforms and band interaction terms were added to account for non-linearities in the spectral mixing. For each reflectance source we investigated if the residuals were correlated with site heterogeneity, soil colour, soil moisture and land cover type. As expected, the best model was obtained when Landsat data for a small region around each site was used. We obtained root mean square error (RMSE) values of 0.134, 0.175 and 0.153 for PV, NPV and B respectively. When we degraded the Landsat data to an area of ~1 km2 around each site the model performance decreased to RMSE of 0.142, 0.181 and 0.166 for PV, NPV and B. Using MODIS reflectance data (from the MCD43A4 and MOD09A1 products) we obtained similar results as when using the 'degraded' Landsat reflectance, with no significant differences between them. Model performance decreased (i.e. RMSE increased) with site heterogeneity when coarse resolution reflectance data was used. We did not find any evidence of soil colour or moisture influence on model performance. We speculate that the unmixing models may be insensitive to soil colour and/or that the soil moisture in the top few millimetres of soil, which influence reflectance in optical sensors, is decoupled from the soil moisture in the top layer (i.e. a few cm) as measured by passive microwave sensors or estimated by models. The models tended to overestimate PV in cropping areas, possibly due to a strong red/ near infrared signal in homogeneous crops which do not have a high green cover. This study sets the basis for an operational Landsat/ MODIS combined product which would benefit users with varying requirements of spatial, temporal resolution and latency and could potentially be applied to other regions in the world.

Guerschman, J. P.; Scarth, P.; McVicar, T.; Malthus, T. J.; Stewart, J.; Rickards, J.; Trevithick, R.; Renzullo, L. J.

2013-12-01

105

Effects of vegetation cover on the tendency of soil to crust in South Africa  

Microsoft Academic Search

Tendency to crust is a potentially useful index for assessing soil degradation and for assisting land use planning in South Africa. In this study, the influence of land use, geology and vegetation cover on the tendency of soil to form a surface crust was investigated in six vegetation types. Crusting at all sites was greater in exposed soils than soils

A. J. Mills; M. V. Fey

2004-01-01

106

Soil Ecological Processes in Vegetation Patches ofWell Drained Permafrost Affected Sites (Kangerlussuaq - West Greenland)  

Microsoft Academic Search

Summary: In parts of continental interior areas of West Greenland's fjords, xerocryic vegetation is characteristic and influences soil properties. The objective of the present study was to compare soil chemical and soil ecolo­ gical properties as wel! as soil genesis influenced by three different types of continental arctic climax vegetation (Kobresia myosuroides, Salix glauca and Betula nana) close to the

Ulrich Ozols

2005-01-01

107

Soil phosphorus forms as quality indicators of soils under different vegetation covers.  

PubMed

The type of vegetation cover determines the physicochemical and biological properties of the soil over which they are developing. The objective of this study was to determine the effect of different vegetation covers on the forms of soil phosphorus, in order to know which of these forms can be used as a soil quality indicator. The experimental area was located on the acidic plateau at the North of Palencia (North Spain), where an area was selected vegetation covers very close to each other: pine (Pinus sylvestris), oak (Quercus pyrenaica), and three different shrub species (Arctostaphylos uva-ursi, Erica australis and Halimium alyssoides). The Ah horizon was sampled and pH, total organic C (C(org)), total N (N), cationic exchange capacity (CEC), sum of bases (S) and P forms by a sequential fractionation were analysed. Results showed that oak and A. uva-ursi improve the considered soil parameters (pH, C(org)/N ratio, CEC, and S) and provide soils of better quality. Inorganic soil P forms were influenced in greater extent by the vegetation cover than were P organic forms. Labile inorganic P forms could be used as indicators of soil quality. The organic P forms were less sensitive than inorganic ones to the indicated improvements. PMID:17307240

Turrión, María-Belén; López, Olga; Lafuente, Francisco; Mulas, Rafael; Ruipérez, César; Puyo, Alberto

2007-05-25

108

The effects of vegetation cover on the radar and radiometric sensitivity to soil moisture  

NASA Technical Reports Server (NTRS)

The measured effects of vegetation canopies on radar and radiometric sensitivity to soil moisture are compared to emission and scattering models. The models are found to predict accurately the measured emission and backscattering for various crop canopies at frequencies between 1.4 and 5.0 GHz, especially at theta equal to or less than 30 deg. Vegetation loss factors, L(theta), increase with frequency and are found to be dependent upon canopy type and water content. In addition, the radiometric power absorption coefficient of a mature corn canopy is 1.75 times that calculated for the radar. Comparison of an L-band radiometer with a C-band radar shows the two systems to be complementary in terms of accurate soil moisture sensing over the extreme range of naturally occurring soil moisture conditions.

Ulaby, F. T.; Dobson, M. C.; Brunfeldt, D. R.; Razani, M.

1982-01-01

109

Complex vegetation responses to soil disturbances in mountain grassland  

Microsoft Academic Search

We studied vegetation responses to disturbances originated by ants and voles in subalpine grasslands in the Eastern Pyrenees.\\u000a We compared the effects of these small-scale disturbances with those of a large-scale disturbance caused by ploughing. We\\u000a wanted to know if these soil disturbances promoted species richness through the existence of a specific guild of plants colonizing\\u000a these areas, and if

Maria-Teresa Sebastià; Laura Puig

2008-01-01

110

Prairie vegetation and soil nutrient responses to ungulate carcasses  

Microsoft Academic Search

The impact of large ungulate carcasses on grassland dynamics was investigated by monitoring vegetation and soil nutrients\\u000a in 50-cm circular zones around the center of bison (Bos bison), cattle (B. taurus), and deer (Odocoileus virginianus) carcasses. An ungulate carcass creates an intense localized disturbance that varies with animal size and the season of death.\\u000a Unlike other natural disturbances, carcasses deposit

E. Gene Towne

2000-01-01

111

River basin soil-vegetation condition assessment applying mathematic simulation methods  

NASA Astrophysics Data System (ADS)

Meticulous attention paid nowadays to the problem of vegetation cover productivity changes is connected also to climate global transformation. At the same time ecosystems anthropogenic transformation, basically connected to the changes of land use structure and human impact on soil fertility, is developing to a great extent independently from climatic processes and can seriously influence vegetation cover productivity not only at the local and regional levels but also globally. Analysis results of land use structure and soil cover condition influence on river basin ecosystems productive potential is presented in the research. The analysis is carried out applying integrated characteristics of ecosystems functioning, space images processing results and mathematic simulation methods. The possibility of making permanent functional simulator defining connection between macroparameters of "phytocenosis-soil" system condition on the basis of basin approach is shown. Ecosystems of river catchment basins of various degrees located in European part of Russia were chosen as research objects. For the integrated assessment of ecosystems soil and vegetation conditions the following characteristics have been applied: 1. Soil-productional potential, characterizing the ability of natural and natural-anthropogenic ecosystem in certain soil-bioclimatic conditions for long term reproduction. This indicator allows for specific phytomass characteristics and ecosystem produce, humus content in soil and bioclimatic parameters. 2. Normalized difference vegetation index (NDVI) has been applied as an efficient, remotely defined, monitoring indicator characterizing spatio-temporal unsteadiness of soil-productional potential. To design mathematic simulator functional simulation methods and principles on the basis of regression, correlation and factor analysis have been applied in the research. Coefficients values defining in the designed static model of phytoproductivity distribution has been executed applying non-linear approximation by the smallest squares method with the help of software in Mathcad environment. Mathematic simulation resulted in defining possible permanent conditions of "phytocenosis-soil" system in coordinates of phytomass, phytoproductivity, humus percentage in soil. It has been demonstrated that phytocenosis productivity is determined not only by vegetation photosynthetic activity but by forest and meadow phytocenosis area ratio as well. Local maximums attached to certain phytomass areas and humus content in soil have been determined at basin phytoproductivity distribution diagram. One of such areas lies within specific phytomass values of B = 133,56 t/hectare and humus content of 2,29 % and the most stable "phytocenosis - soil" system condition corresponds to it. Efficient correlation of natural forest and meadow phytocenosis for the Klyazma river has been defined, at which the most stable permanent condition is achieved and it ranks 7:1. It corresponds to the Klyazma basin location in south taiga zone and it is proved by intensive forest over growing of the abandoned agricultural lands.

Mishchenko, Natalia; Trifonova, Tatiana; Shirkin, Leonid

2013-04-01

112

The influence of biological soil crusts on successional vegetation patterns in a revegetated desert area in the Tengger Desert, China  

NASA Astrophysics Data System (ADS)

Biological soil crusts (BSCs) are an important cover in arid desert landscapes, and have a profound effect on the soil water redistribution, plant growth and vegetation succession. Although a large number of studies have focused on the single-process of BSCs experimentally, relatively few studies have examined the eco-hydrological mechanisms of BSCs influence on successional vegetation patterns in revegetated desert areas. In this study, based on the long term monitoring and focused research on sand-binding vegetation in the Shapotou region (southeastern edge of the Tengger Desert, China) since the 1950s, the characteristics of plant community and BSCs at different successional stages, and the soil water dynamics were investigated. Then a simplified mathematical model describing the coupled dynamics of soil moisture and vegetation in drylands was developed. And finally the role of BSCs on soil water dynamics and vegetation patterns were discussed. Results have showed that BSCs was closely associated with the vegetation succession, such as in the Caragana korshinskii community, moss crusts were the dominate species and in the Artemisia ordosica community, algae crusts were the dominate species. BSCs had a significant effect on soil water infiltration and it was one of the main driving forces to vegetation pattern formations, as algae crusts would induced the tiger bush stripes and moss crusts would lead to the leopard bush spots in arid ecosystems.

Lei, Huang; Zhi-shan, Zhang; Xin-rong, Li

2014-05-01

113

Transfer of Cadmium from Soil to Vegetable in the Pearl River Delta area, South China  

PubMed Central

The purpose of this study was to investigate the regional Cadmium (Cd) concentration levels in soils and in leaf vegetables across the Pearl River Delta (PRD) area; and reveal the transfer characteristics of Cadmium (Cd) from soils to leaf vegetable species on a regional scale. 170 paired vegetables and corresponding surface soil samples in the study area were collected for calculating the transfer factors of Cadmium (Cd) from soils to vegetables. This investigation revealed that in the study area Cd concentration in soils was lower (mean value 0.158 mg kg?1) compared with other countries or regions. The Cd-contaminated areas are mainly located in west areas of the Pearl River Delta. Cd concentrations in all vegetables were lower than the national standard of Safe vegetables (0.2 mg kg?1). 88% of vegetable samples met the standard of No-Polluted vegetables (0.05 mg kg?1). The Cd concentration in vegetables was mainly influenced by the interactions of total Cd concentration in soils, soil pH and vegetable species. The fit lines of soil-to-plant transfer factors and total Cd concentration in soils for various vegetable species were best described by the exponential equation (), and these fit lines can be divided into two parts, including the sharply decrease part with a large error range, and the slowly decrease part with a low error range, according to the gradual increasing of total Cd concentrations in soils. PMID:25247431

Zhang, Huihua; Chen, Junjian; Zhu, Li; Yang, Guoyi; Li, Dingqiang

2014-01-01

114

Environmental behavior of technetium in soil and vegetation: implications for radiological impact assessment  

SciTech Connect

Significant radiological exposures have been estimated for hypothetical atmospheric releases of Tc-99 from gaseous diffusion facilities when vegetation-to-soil concentration ratios representative of laboratory experiments are substituted for generic default values assumed in current regulatory models. To test the relevancy of these laboratory ratios, field investigations were conducted to obtain measurements of the vegetation-to-soil concentration ratio for Tc-99 in samples collected near operating gaseous diffusion facilities and to observe the dynamic behavior of technetium in soil and vegetation following a single application of a sprayed solution of /sup 95m/TcO/sub 4//sup -/ Comparison of observed field concentration ratios and calculated steady-state concentration ratios with ratios obtained from previous laboratory experiments indicates that concentration ratios obtained from field data are one to two orders of magnitude less than those obtained from the laboratory. Furthermore, a substantial accumulation of technetium in soil and vegetation may not occur over long periods of time, since concentrations of technetium in both environmental media were observed to decrease with time subsequent to initial application of /sup 95m/TcO/sub 4//sup -/.

Hoffman, F.O.

1982-04-01

115

Vegetation mosaics in arid Australia: linked roles for climate and soils  

NASA Astrophysics Data System (ADS)

It is widely considered that quasi-regular patterns in dryland soils and vegetation reflect a process of self-organisation. In such a view, the spatial patterns emerge from multiple interactions and feedbacks among the elements of the ecogeomorphic system. In arid western NSW, Australia, key elements affecting the self-organisation of strongly banded vegetation appear to include the extreme climatic variability (related to ENSO and other global climate phenomena) and the geomorphic history of the landscape, which involves major glacial-period accessions of exotic aeolian clays of the illite family, which exhibit very marked shrink-swell behaviour. The latter may be a prerequisite for pattern emergence, and the former a key driver of emergence. A cellular model of pattern emergence was driven by a timeseries of annual rainfalls exhibiting occasional marked wet La Niña years and also multi-year El Niño droughts, in order to explore how this climatic driver affects pattern emergence. Importantly, the model incorporated the effects of drying and contraction of the deeper subsoils during multi-year droughts. In the field, extreme soil desiccation is seen to result in widespread tension cracking and collapse of the surface soils into voids in the more clay rich, and more strongly contracted, subsoil. The collapse features maintain the water trapping efficiency of the vegetation groves even when the plant cover has declined greatly. Trapping efficiency remains low within intergroves, because the subsoils there are always relatively dry, owing to their impermeable soil surfaces. Modelling excluding soil collapse during drought showed much greater loss of groves and resultant changes in grove spacing that is not seen in long-term field monitoring data. This suggests that the variability of annual rainfalls (and not just the average climatic aridity) may actually confer stability on the banded vegetation communities via a little-explored linkage of soil and climatic factors.

Dunkerley, D.

2012-04-01

116

Origin and fate of organic matter in sandy soils along a primary vegetation succession  

Microsoft Academic Search

Until now little is known about the role vegetation plays in the organic matter formation, particularly at the molecular level. Most ecosystems have a long history, which is unknown or too complex to find distinct relations between vegetation and the chemical composition of soil organic matter. To gain a better insight in such relationships, the relative simple soil-vegetation system of

K. Nierop

1999-01-01

117

Soil moisture status estimation over Three Gorges area with Landsat TM data based on temperature vegetation dryness index  

NASA Astrophysics Data System (ADS)

Soil moisture is the important indicator of climate, hydrology, ecology, agriculture and other parameters of the land surface and atmospheric interface. Soil moisture plays an important role on the water and energy exchange at the land surface/atmosphere interface. Remote sensing can provide information on large area quickly and easily, so it is significant to do research on how to monitor soil moisture by remote sensing. This paper presents a method to assess soil moisture status using Landsat TM data over Three Gorges area in China based on TVDI. The potential of Temperature- Vegetation Dryness Index (TVDI) from Landsat TM data in assessing soil moisture was investigated in this region. After retrieving land surface temperature and vegetation index a TVDI model based on the features of Ts-NDVI space is established. And finally, soil moisture status is estimated according to TVDI. It shows that TVDI has the advantages of stability and high accuracy to estimating the soil moisture status.

Xu, Lina; Niu, Ruiqing; Li, Jiong; Dong, Yanfang

2011-12-01

118

Vegetation modeled as a water cloud  

Microsoft Academic Search

Because the microwave dielectric constant of dry vegetative matter is much smaller (by an order of magnitude or more) than the dielectric constant of water, and because a vegetation canopy is usually composed of more than 99% air by volume, it is proposed that the canopy can be modeled as a water cloud whose droplets are held in place by

E. P. W. Attema; Fawwaz T. Ulaby

1978-01-01

119

SRTM vegetation removal and hydrodynamic modeling accuracy  

NASA Astrophysics Data System (ADS)

Hydrodynamic modeling of large remote forested floodplains, such as the Amazon, is hindered by the vegetation signal contained within Digital Elevation Models (DEMs) such as the Shuttle Radar Topography Mission (SRTM). Not removing the vegetation signal causes DEMs to be overelevated preventing the correct simulation of overbank inundation. Previous efforts to remove this vegetation signal have either not accounted for its spatial variability or relied upon single assumed error values. As a possible solution, a systematic approach to removing the vegetation signal which accounts for spatial variability using recently published estimates of global vegetation heights is proposed. The proposed approach is applied to a well-studied reach of the Amazon floodplain where previous hydrodynamic model applications were affected by the SRTM vegetation signal. Greatest improvements to hydrodynamic model accuracy were obtained by subtracting 50-60% of the vegetation height from the SRTM. The vegetation signal removal procedure improved the RMSE (Root-Mean-Square Error) accuracy of the hydrodynamic model than when using the original SRTM in three ways: (1) seasonal floodplain water elevation predictions against TOPEX/Poseidon observations improved from 6.61 to 1.84 m; (2) high water inundation extent prediction accuracy improved from 0.52 to 0.07 against a JERS (Japanese Earth Resources Satellite) observation; (3) low water inundation extent accuracy against a JERS observation improved from 0.22 to 0.12. The simple data requirements of this vegetation removal method enable it to be applied to any remote floodplain for which hydrodynamic model accuracy is hindered by vegetation present in the DEM.

Baugh, Calum A.; Bates, Paul D.; Schumann, Guy; Trigg, Mark A.

2013-09-01

120

Biological soil crust and surface soil properties in different vegetation types of Horqin Sand Land, China  

Microsoft Academic Search

Physical and chemical properties (including coverage, thickness, hardness, moisture, particle size distribution, organic matter and nutrient contents etc.) of biological soil crust and 0–5.0cm surface soil under the crust in three types of vegetation (semi-shrub Artemisia frigida, shrub Salix gordejevii and tree Populus simonii) were surveyed in 2005 and 2006 in Horqin Sand Land to understand the effects of different

Ha-Lin Zhao; Yi-Rui Guo; Rui-Lian Zhou; Sam Drake

2010-01-01

121

Use of LANDSAT images of vegetation cover to estimate effective hydraulic properties of soils  

NASA Technical Reports Server (NTRS)

The estimation of the spatially variable surface moisture and heat fluxes of natural, semivegetated landscapes is difficult due to the highly random nature of the vegetation (e.g., plant species, density, and stress) and the soil (e.g., moisture content, and soil hydraulic conductivity). The solution to that problem lies, in part, in the use of satellite remotely sensed data, and in the preparation of those data in terms of the physical properties of the plant and soil. The work was focused on the development and testing of a stochastic geometric canopy-soil reflectance model, which can be applied to the physically-based interpretation of LANDSAT images. The model conceptualizes the landscape as a stochastic surface with bulk plant and soil reflective properties. The model is particularly suited for regional scale investigations where the quantification of the bulk landscape properties, such as fractional vegetation cover, is important on a pixel by pixel basis. A summary of the theoretical analysis and the preliminary testing of the model with actual aerial radiometric data is provided.

Eagleson, Peter S.; Jasinski, Michael F.

1988-01-01

122

A comparative study of soil water movement under different vegetation covers  

Microsoft Academic Search

Vegetation, varying widely floristically, structurally, and in spatial distribution, is a complex phenomenon, delicately adjusted within itself and to its broader environment. To investigate the soil water movement of different vegetation covers, soil physical properties, and pressure head of soil water, have been analysed in a pine forest and adjacent disturbed grassland at the Terrestrial Environmental Research Centre (ERC) of

A. FERNANDO; T. Tanaka

2002-01-01

123

Impacts of vegetation and cold season processes on soil moisture and climate relationships over Eurasia  

E-print Network

Impacts of vegetation and cold season processes on soil moisture and climate relationships over investigate the impacts of vegetation and cold season processes on soil moisture persistence and climate feedbacks. The joint analysis of independent meteorological, soil moisture and land cover measurements

Ni-Meister, Wenge

124

Estimating soil moisture and the relationship with crop yield using surface temperature and vegetation index  

NASA Astrophysics Data System (ADS)

Soil moisture availability affects rainfed crop yield. Therefore, the development of methods for pre-harvest yield prediction is essential for the food security. A study was carried out to estimate regional crop yield using the Temperature Vegetation Dryness Index (TVDI). Triangular scatters from land surface temperature (LST) and enhanced vegetation index (EVI) space from MODIS (Moderate Resolution Imaging Spectroradiometer) were utilized to obtain TVDI and to estimate soil moisture availability. Then soybean and wheat crops yield was estimated on four agro-climatic zones of Argentine Pampas. TVDI showed a strong correlation with soil moisture measurements, with R2 values ranged from 0.61 to 0.83 and also it was in agreement with spatial pattern of soil moisture. Moreover, results showed that TVDI data can be used effectively to predict crop yield on the Argentine Pampas. Depending on the agro-climatic zone, R2 values ranged from 0.68 to 0.79 for soybean crop and 0.76 to 0.81 for wheat. The RMSE values were 366 and 380 kg ha-1 for soybean and they varied between 300 and 550 kg ha-1 in the case of wheat crop. When expressed as percentages of actual yield, the RMSE values ranged from 12% to 13% for soybean and 14% to 22% for wheat. The bias values indicated that the obtained models underestimated soybean and wheat yield. Accurate crop grain yield forecast using the developed regression models was achieved one to three months before harvest. In many cases the results were better than others obtained using only a vegetation index, showing the aptitude of surface temperature and vegetation index combination to reflect the crop water condition. Finally, the analysis of a wide range of soil moisture availability allowed us to develop a generalized model of crop yield and dryness index relationship which could be applicable in other regions and crops at regional scale.

Holzman, M. E.; Rivas, R.; Piccolo, M. C.

2014-05-01

125

Modeling of the interactions between forest vegetation, disturbances, and sediment yields  

Microsoft Academic Search

in the Idaho batholith are investigated through numerical modeling. The model simulates soil development based on continuous bedrock weathering and the divergence of diffusive sediment transport on hillslopes. Soil removal is due to episodic gully erosion, shallow landsliding, and debris flow generation. In the model, forest vegetation provides root cohesion and surface resistance to channel initiation. Forest fires and harvests

Erkan Istanbulluoglu; David G. Tarboton; Robert T. Pack; Charles H. Luce

2004-01-01

126

Vegetation, soil, and flooding relationships in a blackwater floodplain forest  

USGS Publications Warehouse

Hydroperiod is considered the primary determinant of plant species distribution in temperate floodplain forests, but most studies have focused on alluvial (sediment-laden) river systems. Few studies have evaluated plant community relationships in blackwater river systems of the South Atlantic Coastal Plain of North America. In this study, we characterized the soils, hydroperiod, and vegetation communities and evaluated relationships between the physical and chemical environment and plant community structure on the floodplain of the Coosawhatchie River, a blackwater river in South Carolina, USA. The soils were similar to previous descriptions of blackwater floodplain soils but had greater soil N and P availability, substantially greater clay content, and lower soil silt content than was previously reported for other blackwater river floodplains. Results of a cluster analysis showed there were five forest communities on the site, and both short-term (4 years) and long-term (50 years) flooding records documented a flooding gradient: water tupelo community > swamp tupelo > laurel oak = overcup oak > mixed oak. The long-term hydrologic record showed that the floodplain has flooded less frequently from 1994 to present than in previous decades. Detrended correspondence analysis of environmental and relative basal area values showed that 27% of the variation in overstory community structure could be explained by the first two axes; however, fitting the species distributions to the DCA axes using Gaussian regression explained 67% of the variation. Axes were correlated with elevation (flooding intensity) and soil characteristics related to rooting volume and cation nutrient availability. Our study suggests that flooding is the major factor affecting community structure, but soil characteristics also may be factors in community structure in blackwater systems. ?? 2003, The Society of Wetland Scientists.

Burke, M.K.; King, S.L.; Gartner, D.; Eisenbies, M.H.

2003-01-01

127

Soil water and vegetation management for cleanup of selenium contaminated soils  

SciTech Connect

Over the past year scientists have initiatived a new effort aimed at developing a soil water and vegetation management plan for Kesterson Reservoir. The plan is intended to result in a gradual depletion of the inventory of soluble selenium at the Reservoir through a combination agriculturally oriented practices that enhance dissipation of selenium from near surface soils. Agriculturally oriented processes that will contribute to depletion include microbial volatilization from the soils, direct volatilization by living plants, decomposition and volatilization of selenium-bearing vegetation, harvest and removal of seleniferous vegetation, and leaching. The benefits of using this integrated approach are that (1) no single mechanism needs to be relied upon to detoxify the soils, (2) a stable plant community can be established during this period so that impacts to wildlife can be more easily evaluated and controlled, (3) cleanup and management of the site can be carried out in a cost-effective manner. The management plan is also intended to facilitate control over wildlife exposure to selenium contaminated biota by creating a well managed environment. The majority of research associated with this new effort is being carried out at a 200 m by 50 m test plot in Pond 7. A two-line irrigation system , providing local groundwater as an irrigation supply, has been installed. Through an intensive program of soil water sampling, soil gas sampling, vegetation sampling, groundwater monitoring, and soil moisture monitoring, the mass balance for selenium under irrigated conditions is being evaluated. These studies, in conjunction with supplementary laboratory experiments will provide the information needed to develop an optimal management plan for the site. 23 refs., 38 figs., 10 tabs.

Not Available

1989-05-01

128

A comparison between active and passive sensing of soil moisture from vegetated terrains  

NASA Technical Reports Server (NTRS)

A comparison between active and passive sensing of soil moisture over vegetated areas is studied via scattering models. In active sensing three contributing terms to radar backscattering can be identified: (1) the ground surface scatter term; (2) the volume scatter term representing scattering from the vegetation layer; and (3) the surface volume scatter term accounting for scattering from both surface and volume. In emission three sources of contribution can also be identified: (1) surface emission; (2) upward volume emission from the vegetation layer; and (3) downward volume emission scattered upward by the ground surface. As ground moisture increases, terms (1) and (3) increase due to increase in permittivity in the active case. However, in passive sensing, term (1) decreases but term (3) increases for the same reason. This self conpensating effect produces a loss in sensitivity to change in ground moisture. Furthermore, emission from vegetation may be larger than that from the ground. Hence, the presence of vegetation layer causes a much greater loss of sensitivity to passive than active sensing of soil moisture.

Fung, A. K.; Eom, H. J.

1984-01-01

129

Soil Water Balance and Vegetation Dynamics in two Contrasting Water-limited Mediterranean Ecosystems on Sardinia, Italy  

NASA Astrophysics Data System (ADS)

Water limited conditions strongly impacts soil and vegetation dynamics in Mediterranean regions, which are commonly heterogeneous ecosystems, characterized by inter-annual rainfall variability, topography variability and contrasting plant functional types (PFTs) competing for water use. Mediterranean regions are characterized by two main ecosystems, grassland and woodland, which for both natural and anthropogenic causes can grow in soils with different characteristics, highly impacting water resources. Water resources and forestal planning need a deep understanding of the dynamics between PFTs, soil and atmosphere and their impacts on water and CO2 distributions of these two main ecosystems. The first step is the monitoring of land surface fluxes, soil moisture, and vegetation dynamics of the two contrasting ecosystems. Moreover, due to the large percentage of soils with low depth (< 50 cm), and due to the quick hydrologic answer to atmospheric forcing in these soils, there is also the need to understand the impact of the soil depth in the vegetation dynamics, and make measurements in these types of soils. Sardinia island is a very interesting and representative region of Mediterranean ecosystems. It is low urbanized, and is not irrigated, except some plan areas close to the main cities where main agricultural activities are concentrated. The case study sites are within the Flumendosa river basin on Sardinia. Two sites, both in the Flumendosa river and with similar height a.s.l., are investigated. The distance between the sites is around 4 km but the first is a typically grass site located on an alluvial plan valley with a soil depth more than 2m, while the second site is a patchy mixture of Mediterranean vegetation types Oaks, creepers of the wild olive trees and C3 herbaceous species and the soil thickness varies from 15-40 cm, bounded from below by a rocky layer of basalt, partially fractured. In both sites land-surface fluxes and CO2 fluxes are estimated by eddy correlation technique based micrometeorological towers. Soil moisture profiles were also continuously estimated using water content reflectometers and gravimetric method, and periodically leaf area index PFTs are estimated during the Spring-Summer 2005. The following objectives are addressed:1) pointing out the dynamics of land surface fluxes, soil moisture, CO2 and vegetation cover for two contrasting water-limited ecosystems; 2) assess the impact of the soil depth and type on the CO2 and water balance dynamics. For reaching the objectives an ecohydrologic model is also successfully used and applied to the case studies. It couples a vegetation dynamic model, which computes the change in biomass over time for the PFTs, and a 3-component (bare soil, grass and woody vegetation) land surface model.

Montaldo, N.; Albertson, J. D.; Corona, R.

2011-12-01

130

Vegetation stress from soil moisture and chlorophyll fluorescence: synergy between SMAP and FLEX approaches  

NASA Astrophysics Data System (ADS)

Vegetation stress detection continues being a focal objective for remote sensing techniques. It has implications not only for practical applications such as irrigation optimization or precision agriculture, but also for global climate models, providing data to better link water and carbon exchanges between the surface and the atmospheric and improved parameterization of the role of terrestrial vegetation in the coupling of water and carbon cycles. Traditional approaches to map vegetation stress using remote sensing techniques have been based on measurements of soil moisture status, canopy (radiometric) temperature and, to a lesser extent, canopy water content, but new techniques such as the dynamics of vegetation fluorescence emission, are also now available. Within the context of the preparatory activities for the SMAP and FLEX missions, a number of initiatives have been put in place to combine modelling activities and field experiments in order to look for alternative and more efficient ways of detecting vegetation stress, with emphasis on synergistic remote sensing approaches. The potential of solar-induced vegetation fluorescence as an early indicator of stress has been widely demonstrated, for different type of stress conditions: light amount (excess illumination) and conditions (direct/diffuse), temperature extremes (low and high), soil water availability (soil moisture), soil nutrients (nitrogen), atmospheric water vapour and atmospheric CO2 concentration. The effects caused by different stress conditions are sometimes difficult to be decoupled, also because different causes are often combined, but in general they then to change the overall fluorescence emission (modulating amplitude) or changing the relative contributions of photosystems PSI and PSII or the relative fluorescence re-absorption effects caused by modifications in the structure of pigment bed responsible for light absorption, in particular for acclimation for persistent stress conditions. While soil moisture deficit is often the reason for the stress, the capability for an early detection of short-time stress conditions is one of the main advantages of vegetation fluorescence. The combined usage of active and passive techniques is also discussed. In the case of soil moisture, combination of active (radar) and passive (L-band radiometry) approaches are used, while in the case of fluorescence active (laser induced) and passive (solar induced) techniques are used as well. Experience from active techniques in laboratory and field conditions helps the operational usage of passive techniques which are readily applicable to satellite observations. Vegetation fluorescence dynamics, particularly over boreal forest, is characterized by an abrupt change in fluorescence levels in coincidence with the activation and deactivation of the photosynthetic machinery at start/end of growing season, which is also related to freeze/thaw state of soil conditions. The interest of looking at such transitions both on the side of photosynthetic activity (combined fluorescence and temperature measurements) and freeze/thaw conditions (L-band radiometry) can provide an unprecedented description of the soil and vegetation interactions and dynamical feedbacks in the energy and chemical exchanges with the atmosphere. A review of methods and results will be discussed in this paper, including suggestions for synergistic approaches to be exploited in future research priorities in vegetation stress detection.

Moreno, Jose; Moran, Susan

2014-05-01

131

Modeling of soil water content and soil temperature at selected U.S. and central European stations using SoilClim model  

Microsoft Academic Search

Within the presented study the SoilClim model was tested through various climatic and soil conditions. SoilClim model enables to estimate reference and actual evapotranspiration from defined vegetation cover and consequently the soil water content within two defined layers (named as Moisture control section I and II) could be deduced. The soil temperature in 0.5 m depth is also estimated (on

P. Hlavinka; M. Trnka; J. Balek; Z. Zalud; M. Hayes; M. Svoboda; J. Eitzinger

2009-01-01

132

Productivity of wet soils: Biomass of cultivated and natural vegetation  

SciTech Connect

Wet soils, soils which have agronomic limitations because of excess water, comprise 105 million acres of non-federal land in the conterminous United States. Wet soils which support hydrophytic plants are ''wetlands'', and are some of the most productive natural ecosystems in the world. When both above- and belowground productivity are considered, cattail (Typha latifolia) is the most productive temperate wetland species (26.4 Mg/ha/year). Both cattail and reed (Phragmites australis) have aboveground productivities of about 13 Mg/ha/year. Although average aboveground yields of reed canarygrass (Phalaris arundinacea) are lower (9.5 Mg/ha/year), techniques for its establishment and cultivation are well-developed. Other herbaceous wetland species which show promise as biomass crops include sedge (Carex spp.), river bulrush (Scirpus fluviatilis) and prairie cordgrass (Spartina pectinata). About 40% of wet soils in the conterminous US are currently cultivated, and they produce one-quarter of the major US crops. Most of this land is artificially drained for crops such as corn, soybeans, and vegetables. US wetlands are drained for agriculture at the rate of 223,000 ha/yr. Paddies flooded with water are used to grow rice, cranberries, and wild rice. Forage and live sphagnum moss are products of undrained wetlands. A number of federal and state regulations apply to the draining or irrigation of wetlands, but most do not seriously restrict their use for agriculture. 320 refs., 36 tabs.

Johnston, C.A.

1988-12-01

133

Studying the Relationship Between Vegetation and PhysicoChemical Properties of Soil, Case Study: Tabas Region, Iran  

Microsoft Academic Search

In order to study the relationship between vegetation and physico-chemical properties of soil of the margins of Tabas Kavir (salty desert), vegetation and soil components were surveyed. Regarding to the soil and vegetation distribution and land use in this region, four distinct areas were selected and classified covering all factors. Then, based on different vegetation cover percentage, the minimum plots

2006-01-01

134

Use of Radar Vegetation Index (RVI) in Passive Microwave Algorithms for Soil Moisture Estimates  

NASA Astrophysics Data System (ADS)

The Soil Moisture Active Passive (SMAP) satellite will provide a unique opportunity for the estimation of soil moisture by having simultaneous radar and radiometer measurements available. As with the Soil Moisture and Ocean Salinity (SMOS) satellite, the soil moisture algorithms will need to account for the contribution of vegetation to the brightness temperature. Global maps of vegetation volumetric water content (VWC) are difficult to obtain, and the SMOS mission has opted to estimate the optical depth of standing vegetation by using a relationship between the VWC and the leaf area index (LAI). LAI is estimated from optical remote sensing or through soil-vegetation-atmosphere transfer modeling. During the growing season, the VWC of agricultural crops can increase rapidly, and if cloud cover exists during an optical acquisition, the estimation of LAI may be delayed, resulting in an underestimation of the VWC and overestimation of the soil moisture. Alternatively, the radar vegetation index (RVI) has shown strong correlation and linear relationship with VWC for rice and soybeans. Using the SMAP radar to produce RVI values that are coincident to brightness temperature measurements may eliminate the need for LAI estimates. The SMAP Validation Experiment 2012 (SMAPVEX12) was a cal/val campaign for the SMAP mission held in Manitoba, Canada, during a 6-week period in June and July, 2012. During this campaign, soil moisture measurements were obtained for 55 fields with varying soil texture and vegetation cover. Vegetation was sampled from each field weekly to determine the VWC. Soil moisture measurements were taken coincident to overpasses by an aircraft carrying the Passive and Active L-band System (PALS) instrumentation. The aircraft flew flight lines at both high and low altitudes. The low altitude flight lines provided a footprint size approximately equivalent to the size of the SMAPVEX12 field sites. Of the 55 field sites, the low altitude flight lines provided measurements for 15 fields. One field was planted in corn; three were pasture; six were soybeans; three were wheat; and two were winter wheat. The average RVI for each field was determined for each PALS overpass, with sampled radar data confined to the field dimensions. A linear interpolation was conducted between measured values of VWC to estimate a daily VWC value. A linear regression was conducted between the average VWC and the RVI, for each vegetation type. A positive linear relationship was found for all crops, with the exception of pasture. The correlation between the RVI and VWC was strong for corn and pasture, but moderate for soybeans and winter wheat; however, the correlation for corn was not significant. The developed models were utilized to provide a calculated VWC which was inputted into a modified version of the Land Parameter Retrieval Model (LPRM) to determine the error associated with using a calculated VWC from the RVI versus measured VWC data. The LPRM outputs for both scenarios were compared to the PALS radiometer measurements of brightness temperature.

Rowlandson, T. L.; Berg, A. A.

2013-12-01

135

Land-use history has a stronger impact on soil microbial community composition than aboveground vegetation and soil properties  

Microsoft Academic Search

The response of soil microbial communities following changes in land-use is governed by multiple factors. The objectives of this study were to investigate (i) whether soil microbial communities track the changes in aboveground vegetation during succession; and (ii) whether microbial communities return to their native state over time. Two successional gradients with different vegetation were studied at the W. K.

Kamlesh Jangid; Mark A. Williams; Alan J. Franzluebbers; Thomas M. Schmidt; David C. Coleman; William B. Whitman

2011-01-01

136

Microwave model prediction and verifications for vegetated terrain  

NASA Technical Reports Server (NTRS)

To understand the scattering properties of a deciduous and a coniferous type vegetation scattering models were developed assuming either a disc type leaf or a needle type leaf. The major effort is to calculate the corresponding scattering phase functions and then each of the functions is used in a radiative transfer formulation to compute the scattering intensity and consequently the scattering coefficient. The radiative transfer formulation takes into account the irregular ground surface by including the rough soil surface in the boundary condition. Thus, the scattering model accounts for volume scattering inside the vegetation layer, the surface scattering from the ground and the interaction between scattering from the soil surface and the vegetation volume. The contribution to backscattering by each of the three scattering mechanisms is illustrated along with the effects of each layer or surface parameter. The major difference between the two types of vegetation is that when the incident wavelength is comparable to the size of the leaf there is a peak appearing in the mid angular region of the backscattering curve for the disc type leaf whereas it is a dip in the same region for a needle type leaf.

Fung, A. K.

1985-01-01

137

The role of soil-surface sealing, microtopography, and vegetation patches in rainfall-runoff processes in semiarid areas  

NASA Astrophysics Data System (ADS)

The hydrological response of semiarid watersheds to short but intense rainfall events is complex due to feedbacks among water fluxes, vegetation patches, topography, and soil properties. This paper seeks to quantify the combined impact of soil-surface sealing, microtopography, and vegetation patches on surface hydrologic processes on a semiarid hillslope. A modeling approach using a two-layer conceptual infiltration model and two-dimensional surface runoff model was developed to study rainfall-runoff relationships. This combined model is applicable to heterogeneous areas with spatially varying soil properties, landscape, and land-cover characteristics. Data from a semiarid site in southern Israel was used to evaluate the model and analyze fundamental hydrologic mechanisms. Our results indicate that seal layer, microtopography, and vegetation play important roles in dry land runoff processes: seal layer controls runoff generation; vegetation patches affect overland flow by enhancing local infiltration rates; microtopography has a small impact on the total amount of runoff, but shapes the spatial pattern of overland flow. The presence of vegetation patches amplifies the effect of microtopography by increasing spatial variability of infiltration and runoff. Results also show that water resource allocation favors vegetation patches through surface runoff, with maximum local cumulative infiltration one order of magnitude higher than the amount of water available from rainfall. This suggests a sophisticated system of water resource distribution in semiarid ecosystems through complex interactions among environmental factors.

Chen, L.; Sela, S.; Svoray, T.; Assouline, S.

2013-09-01

138

Dynamics of deep soil moisture in response to vegetational restoration on the Loess Plateau of China  

NASA Astrophysics Data System (ADS)

The limitation of soil water in semiarid regions restricts the formation of a good cover of vegetation. The Loess Plateau in China, well known for its severe soil erosion, has a thick loessial soil that holds substantial volumes of water and provides the basis of a sustainable restoration of vegetation. Our limited understanding of the dynamics of deep soil moisture, however, could lead to the mismanagement of soil-water resources or could even misguide the policies of vegetational reconstruction. To evaluate the temporal response of deep soil moisture in different types of revegetation, we observed soil moisture to a depth of 340 cm in four plots, planted with Korshinsk peashrub (KOP), purple alfalfa (ALF), native plants (natural fallow, NAF), and millet (MIL), on 15 measurement events from 2010 to 2012. Our analysis provided four main conclusions. (1) The quantitative difference of potential evapotranspiration and actual precipitation resulted in natural deficits of soil moisture. The dynamics of deep soil moisture, however, were mainly dominated by the type of vegetation. Deep soils in plots of KOP and ALF became drier than the soil in plots of NAF and MIL. (2) Deep soil moisture in KOP and ALF was weakly variable. Correlations of time series of soil moisture between the upper and lower layers tended not to be significant. Dried soil layer, a special hydrological phenomenon, had formed in the plots. (3) The correlation between variances of soil moisture and the corresponding mean values were not always significantly positive due to the influence of vegetational type, observational depth, and date. (4) Fallow may be the best cover for achieving adequate hydrological sustainability of the soil. These results are expected to help improve the understanding of the response of deep soil moisture to vegetational restoration and to provide insight into the dynamics of deep soil moisture influenced by vegetation on loessial slopes.

Jia, Yu-Hua; Shao, Ming-An

2014-11-01

139

Soil eco-hydrological characteristics of typical vegetation community in Yellow River Delta  

Microsoft Academic Search

To study the eco-hydrological characteristics of typical vegetation community (Robinia pseudoacacia, Populus euramericana, Fraxinus chinensis) in lowlands of the Yellow River Delta, taking bare area as the control. Soil hydro-physical properties, soil water infiltration and soil water-storage capacity of three kinds of vegetation community were determined in field and laboratory. The results were showed that:1) Compared with bare area, soil

Jiangbao Xia; Zhaohua Lu; Chuanrong Li; Peng Gao

2011-01-01

140

The Aggregate Description of Semi-Arid Vegetation with Precipitation-Generated Soil Moisture Heterogeneity  

NASA Technical Reports Server (NTRS)

Meteorological measurements in the Walnut Gulch catchment in Arizona were used to synthesize a distributed, hourly-average time series of data across a 26.9 by 12.5 km area with a grid resolution of 480 m for a continuous 18-month period which included two seasons of monsoonal rainfall. Coupled surface-atmosphere model runs established the acceptability (for modelling purposes) of assuming uniformity in all meteorological variables other than rainfall. Rainfall was interpolated onto the grid from an array of 82 recording rain gauges. These meteorological data were used as forcing variables for an equivalent array of stand-alone Biosphere-Atmosphere Transfer Scheme (BATS) models to describe the evolution of soil moisture and surface energy fluxes in response to the prevalent, heterogeneous pattern of convective precipitation. The calculated area-average behaviour was compared with that given by a single aggregate BATS simulation forced with area-average meteorological data. Heterogeneous rainfall gives rise to significant but partly compensating differences in the transpiration and the intercepted rainfall components of total evaporation during rain storms. However, the calculated area-average surface energy fluxes given by the two simulations in rain-free conditions with strong heterogeneity in soil moisture were always close to identical, a result which is independent of whether default or site-specific vegetation and soil parameters were used. Because the spatial variability in soil moisture throughout the catchment has the same order of magnitude as the amount of rain failing in a typical convective storm (commonly 10% of the vegetation's root zone saturation) in a semi-arid environment, non-linearitv in the relationship between transpiration and the soil moisture available to the vegetation has limited influence on area-average surface fluxes.

White, Cary B.; Houser, Paul R.; Arain, Altaf M.; Yang, Zong-Liang; Syed, Kamran; Shuttleworth, W. James

1997-01-01

141

Variability in apparent soil organic carbon turnover times across climate zones and vegetation classes  

NASA Astrophysics Data System (ADS)

Our understanding about the climatic controls on the rate of soil organic carbon (SOC) decomposition is still limited and greatly debated, especially the temperature sensitivity of SOC decomposition. Some argue that SOC turnover time (TO) decreases exponentially with increasing temperatures, while others disagree. Based on a number of assumptions, we calculated the ratio between soil CO2 efflux and soil bulk carbon stocks, from which we obtained an estimate of apparent TO for bulk soils across a selection of forested sites around the globe. We used data collected from site-PIs and from recently-available databases of: soil chamber flux measurements (Global soil respiration database: code.google.com/p/srdb/), ecosystem carbon flux measurements (FLUXNET LaThuile dataset: www.fluxdata.org), and global soil carbon stock estimates (Harmonized world soil database: www.iiasa.ac.at/Research/LUC/External-World-soil-database/HTML/). We investigated across-site variability of these apparent TO values in relation to climate (i.e. site's mean annual temperature, MAT, and total annual precipitation, TAP) and vegetation classes (i.e. broadleaf deciduous, needle-leaf deciduous, broadleaf evergreen, and needle-leaf evergreen). We found that, when all data points were considered, TO decreased exponentially with increasing MAT and TAP, in accordance with past studies, although the relationship with TAP was not as strong as with MAT. The overall negative exponential relationship was maintained even when the data was analyzed under the combined effects of MAT and TAP and vegetation class. TO at sites with low annual precipitation and low mean annual temperatures were high (i.e. the rate of decomposition was low). However, we also found that this overall global exponential relationship was largely driven by the difference in TO between sites located in the boreal climate zone and sites located in the other climate zones considered (i.e. tropical, Mediterranean and temperate climate zones, combined). Furthermore, the range of computed TO values in the boreal zone was statistically higher compared to the rest of the climatic zones studied. We also found that accounting for foliage type improved the model fit. However, there was a strong correlation between climate and vegetation class. Results from this study add to our understanding of the spatial variability of SOM decomposition. The trends and relationships we obtained could help to constrain current models of global soil carbon dynamics.

Khomik, M.; Reichstein, M.; Schrumpf, M.; Beer, C.; Curiel Yuste, J.; Janssens, I.; Luyssaert, S.; Subke, J.; Trumbore, S.; Wutzler, T.; Fluxnet Lathuile: Www. Fluxdata. Org

2011-12-01

142

Constructing vegetation productivity equations by employing undisturbed soils data: An Oliver County, North Dakota case study  

SciTech Connect

Surface mine reclamation specialists have been searching for predictive methods to assess the capability of disturbed soils to support vegetation growth. We conducted a study to develop a vegetation productivity equation for reclaiming surface mines in Oliver County, North Dakota, thereby allowing investigators to quantitatively determine the plant growth potential of a reclaimed soil. The study examined the predictive modeling potential for both agronomic crops and woody plants, including: wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), oat (Avena sativa L.), corn (Zea mays L.), grass and legume mixtures, Eastern red cedar (Juniperus virginiana L.), Black Hills spruce (Picea glauca var. densata Bailey), Colorado spruce (Picea pungens Engelm.), ponderosa pine (Pinus ponderosa var. scope Engelm.), green ash (Fraxinus pennsylvanica Marsh.), Eastern cottonwood Populus deltoides (Bart. ex Marsh.), Siberian elm (Ulmus pumila L.), Siberian peashrub (Caragana arborescens Lam), American plum (Prunus americans Marsh.), and chokecherry ( Prunus virginiana L.). An equation was developed which is highly significant (p<0.0001), explaining 81.08% of the variance (coefficient of multiple determination=0.8108), with all regressors significant (p{le}0.048, Type II Sums of Squares). The measurement of seven soil parameters are required to predict soil vegetation productivity: percent slope, available water holding capacity, percent rock fragments, topographic position, electrical conductivity, pH, and percent organic matter. While the equation was developed from data on undisturbed soils, the equation`s predictions were positively correlated (0.71424, p{le}0.0203) with a small data set (n=10) from reclaimed soils.

Burley, J.B. [Michigan State Univ., East Lansing, MI (United States); Polakowski, K.J.; Fowler, G. [Univ. of Michigan, Ann Arbor, MI (United States)

1996-12-31

143

Inclusion of vegetation in the Town Energy Balance model for modeling urban green areas  

NASA Astrophysics Data System (ADS)

Cities impact both local climate, through urban heat islands, and global climate, because they are an area of heavy greenhouse gas release into the atmosphere due to heating, air conditioning and traffic. Including more vegetation into cities is a planning strategy having possible positive impacts for both concerns. Improving vegetation representation into urban models will allow to address more accurately these questions. This paper presents an improvement of the TEB urban canopy model. Vegetation is directly included inside the canyon, allowing shadowing of grass by buildings, better representation of urban canopy form, and, a priori, a more accurate simulation of canyon air microclimate. The development is performed so that any vegetation model can be used to represent the vegetation part. Here the ISBA model is used. The model results are compared to microclimatic and evaporation measurements performed in small courtyards in a very arid region of Israel. Two experimental landscaping strategies - bare soil or irrigated grass in the courtyard - are observed and simulated. The new version of the model with integrated vegetation performs better than if vegetation is treated outside the canyon. Surface temperatures are closer to the observations, especially at night when radiative trapping is important. The integrated vegetation version simulates a more humid air inside the canyon. The microclimatic quantities are better simulated with this new version. This opens opportunities to study with better accuracy the urban microclimate, down to the micro (or canyon) scale.

Lemonsu, A.; Masson, V.; Shashua-Bar, L.; Erell, E.; Pearlmutter, D.

2012-05-01

144

MAGE, a dynamic model of alkaline grassland ecosystems with variable soil characteristics  

Microsoft Academic Search

An area-based process model for alkaline grassland ecosystem, MAGE, was developed to address the problems associated with the soil alkalization\\/dealkalization processes coupled with surface vegetation on Songnen Plain, northeast China. The model gave special consideration to the variation of soil characteristics such as water retentivity and hydraulic conductivity as functions of surface vegetation. Soil within 1 m depth was divided

Qiong Gao; Xiusheng Yang; Rui Yun; Chunping Li

1996-01-01

145

MANAGING VEGETABLE GARDEN SOIL FERTILITY IN VERMONT Vern Grubinger, Extension Professor, University of Vermont  

E-print Network

and its availability to soil microbes for decomposition. Soil pH affects the availability of plant1 MANAGING VEGETABLE GARDEN SOIL FERTILITY IN VERMONT Vern Grubinger, Extension Professor, University of Vermont Soil fertility is determined by the chemical, physical and biological characteristics

Hayden, Nancy J.

146

Locating Amazonian Dark Earths (ADE) using vegetation vigour as a surrogate for soil type  

Microsoft Academic Search

Amazonian Dark Earths (ADE) are patches of archaeological soils scattered throughout the Amazon Basin. These soils are a mixture of charcoal, nutrient vegetable matter and the underlying Oxisol soil. ADE are extremely fertile in comparison to the surrounding soils and they are sought after by local residents for agricultural food production. Research is being conducted to learn how ADE were

Jonathan B. Thayn; Kevin P. Price; William I. Woods

2011-01-01

147

Winter Soil Respiration from Different Vegetation Patches in the Yellow River Delta, China  

NASA Astrophysics Data System (ADS)

Vegetation type and density exhibited a considerable patchy distribution at very local scales in the Yellow River Delta, due to the spatial variation of soil salinity and water scarcity. We proposed that soil respiration is affected by the spatial variations in vegetation type and soil chemical properties and tested this hypothesis in three different vegetation patches ( Phragmites australis, Suaeda heteroptera and bare soil) in winter (from November 2010 to April 2011). At diurnal scale, soil respiration all displayed single-peak curves and asymmetric patterns in the three vegetation patches; At seasonal scale, soil respiration all declined steadily until February, and then increased to a peak in next April. But, the magnitude of soil respiration showed significant differences among the three sites. Mean soil respiration rates in winter were 0.60, 0.45 and 0.17 ?mol CO2 m-2 s-1 for the Phragmites australis, Suaeda heteroptera and bare soil, respectively. The combined effect of soil temperature and soil moisture accounted for 58-68 % of the seasonal variation of winter soil respiration. The mean soil respiration revealed positive and linear correlations with total N, total N and SOC storages at 0-20 cm depth, and plant biomass among the three sites. We conclude that the patchy distribution of plant biomass and soil chemical properties (total C, total N and SOC) may affect decomposition rate of soil organic matter in winter, thereby leading to spatial variations in soil respiration.

Han, Guangxuan; Yu, Junbao; Li, Huabing; Yang, Liqiong; Wang, Guangmei; Mao, Peili; Gao, Yongjun

2012-07-01

148

[Effects of strong reductive approach on remediation of degraded facility vegetable soil].  

PubMed

High application rate of chemical fertilizers and unreasonable rotation in facility vegetable cultivation can easily induce the occurrence of soil acidification, salinization, and serious soil-borne diseases, while to quickly and effectively remediate the degraded facility vegetable soil can considerably increase vegetable yield and farmers' income. In this paper, a degraded facility vegetable soil was amended with 0, 3.75, 7.50, and 11.3 t C x hm(-2) of air-dried alfalfa and flooded for 31 days to establish a strong reductive environment, with the variations of soil physical and chemical properties and the cucumber yield studied. Under the reductive condition, soil Eh dropped quickly below 0 mV, accumulated soil NO3(-) was effectively eliminated, soil pH was significantly raised, and soil EC was lowered, being more evident in higher alfalfa input treatments. After treated with the strong reductive approach, the cucumber yield in the facility vegetable field reached 53.3-57.9 t x hm(-2), being significantly higher than that in un-treated facility vegetable field in last growth season (10.8 t x hm(-2)). It was suggested that strong reductive approach could effectively remediate the degraded facility vegetable soil in a short term. PMID:24417122

Zhu, Tong-Bin; Meng, Tian-Zhu; Zhang, Jin-Bo; Cai, Zu-Cong

2013-09-01

149

Terrestrial biogeochemical cycling and vegetation response to climate in an earth system model  

SciTech Connect

We are developing (1) a seasonal model of terrestrial productivity and biogeochemical cycling (TERRA) and (2) a model of vegetation response to climate (HABITAT). Both of these models are designed to be components of an Earth System Model being developed at Lawrence Livermore National Laboratory (LLNL). We have implemented the grid-cell model of TERRA and have calibrated it for the 17 vegetation types that it simulates. In a sensitivity analysis, we have found that total system response is most sensitive to parameters affecting soil moisture content which, in turn, affects soil respiration. Albedo was found to be an important factor in tundra systems. Carbon sequestration was strongly influenced by only a handful of parameters for each of the five types discussed in this paper. Parameters affecting soil respiration, soil moisture, littefall rate, CO[sub 2] assimilation, C:N ratio in litterfall, and nitrogen uptake were, in most circumstances, found to be the most important parameters. As an initial phase in constructing the vegetation response model, we have investigated an existing method of classifying vegetation life zones based on total annual precipitation and average monthly temperature to determine if this method discriminates between vegetation types. We used global vegetation and climatic data sets for this analysis. We found that these variables lack power to resolve vegetation types.

Kercher, J.R.; Axelrod, M.C.; MacCracken, M.C. (Lawrence Livermore National Lab., CA (United States)); Chambers, J.Q. (Lawrence Livermore National Lab., CA (United States) California Univ., Santa Barbara, CA (United States). Dept. of Biological Sciences)

1992-10-01

150

Terrestrial biogeochemical cycling and vegetation response to climate in an earth system model  

SciTech Connect

We are developing (1) a seasonal model of terrestrial productivity and biogeochemical cycling (TERRA) and (2) a model of vegetation response to climate (HABITAT). Both of these models are designed to be components of an Earth System Model being developed at Lawrence Livermore National Laboratory (LLNL). We have implemented the grid-cell model of TERRA and have calibrated it for the 17 vegetation types that it simulates. In a sensitivity analysis, we have found that total system response is most sensitive to parameters affecting soil moisture content which, in turn, affects soil respiration. Albedo was found to be an important factor in tundra systems. Carbon sequestration was strongly influenced by only a handful of parameters for each of the five types discussed in this paper. Parameters affecting soil respiration, soil moisture, littefall rate, CO{sub 2} assimilation, C:N ratio in litterfall, and nitrogen uptake were, in most circumstances, found to be the most important parameters. As an initial phase in constructing the vegetation response model, we have investigated an existing method of classifying vegetation life zones based on total annual precipitation and average monthly temperature to determine if this method discriminates between vegetation types. We used global vegetation and climatic data sets for this analysis. We found that these variables lack power to resolve vegetation types.

Kercher, J.R.; Axelrod, M.C.; MacCracken, M.C. [Lawrence Livermore National Lab., CA (United States); Chambers, J.Q. [Lawrence Livermore National Lab., CA (United States)]|[California Univ., Santa Barbara, CA (United States). Dept. of Biological Sciences

1992-10-01

151

A new offline dust cycle model that includes dynamic vegetation  

NASA Astrophysics Data System (ADS)

Current offline dust cycle models are unable to predict variability in the extent of arid and semi-arid regions caused by the transient response of vegetation cover to the climate. As a consequence, it is not possible to test whether inter-annual variability in the dust loading is caused by vegetation changes or other processes. A new dust cycle model is presented which uses the Lund-Potsdam-Jena dynamic global vegetation model (Sitch et al., 2003) to calculate time varying dust sources. Surface emissions are calculated by simulating the processes of saltation and sandblasting (Tegen et al., 2002). Dust particles are transported as independent tracers within the TOMCAT chemical transport (Chipperfield, 2006). Dust is removed from the atmosphere by gravitational settling and sub-cloud scavenging. To improve the performance of the model, threshold values for vegetation cover, soil moisture, snow depth and threshold friction velocity, used to determine surface emissions are tuned. The effectiveness of three sub-cloud scavenging schemes are also tested. The tuning experiments are evaluated against multiple measurement datasets. The tuned model is used to investigate whether changes in vegetation cover in the Sahel can explain the four-fold increase in dust concentrations measured at Barbados during the 1980s relative to the 1960s (Prospero and Nees, 1986). Results show there was an expansion of the Sahara in 1984 relative to 1966 resulting in a doubling of emissions from the Sahel. However, this alone is not enough to account for the high dust concentrations measured at Barbados. This finding adds strength to the hypothesis that human induced soil degradation in North Africa may be responsible for the increase in high dust concentrations at Barbados during the 1980s relative to the 1960s. Chipperfield, M. P. (2006). "New version of the TOMCAT/SLIMCAT off-line chemical transport model: Intercomparison of stratospheric tracer experiments." Quarterly Journal of the Royal Meteorological Society 132(617): 1179-1203. Prospero, J. M. and R. T. Nees (1986). "Impact of the North African drought and El Nino on mineral dust in the Barbados trade winds." Nature 320(6064): 735-738. Sitch, S., B. Smith, et al. (2003). "Evaluation of ecosystem dynamics, plant geography and terrestrial carbon cycling in the LPJ dynamic global vegetation model." Global Change Biology 9: 161-185. Tegen, I., S. P. Harrison, et al. (2002). "Impact of vegetation and preferential source areas on global dust aerosol: Results from a model study." Journal of Geophysical Research-Atmospheres 107(D21).

Shannon, Sarah; Lunt, Daniel

2010-05-01

152

A soil water-balance ‘bucket’ model for paleoclimatic purposes 1. Model structure and validation  

Microsoft Academic Search

Models currently used to describe soil water content in paleoclimatic settings develop evapotranspiration equations which do not vary with soil type and vegetation cover and which do not separate percolation from runoff. The paper describes the selection of one model (SWBBM\\/B) predicting soil moisture at daily scale, using a limited number of input parameters (precipitation, insolation and temperature). The models

Samuel P. Evans; Marco Trevisan

1995-01-01

153

Evaluation of soil and vegetation response to drought using SMOS soil moisture satellite observations  

NASA Astrophysics Data System (ADS)

Soil moisture plays an important role in determining the likelihood of droughts and floods that may affect an area. Knowledge of soil moisture distribution as a function of time and space is highly relevant for hydrological, ecological and agricultural applications, especially in water-limited or drought-prone regions. However, measuring soil moisture is challenging because of its high variability; point-scale in-situ measurements are scarce being remote sensing the only practical means to obtain regional- and global-scale soil moisture estimates. The ESA's Soil Moisture and Ocean Salinity (SMOS) is the first satellite mission ever designed to measuring the Earth's surface soil moisture at near daily time scales with levels of accuracy previously not attained. Since its launch in November 2009, significant efforts have been dedicated to validate and fine-tune the retrieval algorithms so that SMOS-derived soil moisture estimates meet the standards required for a wide variety of applications. In this line, the SMOS Barcelona Expert Center (BEC) is distributing daily, monthly, and annual temporal averages of 0.25-deg global soil moisture maps, which have proved useful for assessing drought and water-stress conditions. In addition, a downscaling algorithm has been developed to combine SMOS and NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) data into fine-scale (< 1km) soil moisture estimates, which permits extending the applicability of the data to regional and local studies. Fine-scale soil moisture maps are currently limited to the Iberian Peninsula but the algorithm is dynamic and can be transported to any region. Soil moisture maps are generated in a near real-time fashion at BEC facilities and are used by Barcelona's fire prevention services to detect extremely dry soil and vegetation conditions posing a risk of fire. Recently, they have been used to explain drought-induced tree mortality episodes and forest decline in the Catalonia region. These soil moisture products can also be a useful tool to monitor the effectiveness of land restoration management practices. The aim of this work is to demonstrate the feasibility of using SMOS soil moisture maps for monitoring drought and water-stress conditions. In previous research, SMOS-derived Soil Moisture Anomalies (SSMA), calculated in a ten-day basis, were shown to be in close relationship with well-known drought indices (the Standardized Precipitation Index and the Standardized Precipitation Evapotranspiration Index). In this work, SSMA have been calculated for the period 2010-2013 in representative arid, semi-arid, sub-humid and humid areas across global land biomes. The SSMA reflect the cumulative precipitation anomalies and is known to provide 'memory' in the climate and hydrological system; the water retained in the soil after a rainfall event is temporally more persistent than the rainfall event itself, and has a greater persistence during periods of low precipitation. Besides, the Normalized Difference Vegetation Index (NDVI) from MODIS is used as an indicator of vegetation activity and growth. The NDVI time series are expected to reflect the changes in surface vegetation density and status induced by water-deficit conditions. Understanding the relationships between SSMA and NDVI concurrent time series should provide new insight about the sensitivity of land biomes to drought.

Piles, Maria; Sánchez, Nilda; Vall-llossera, Mercè; Ballabrera, Joaquim; Martínez, Justino; Martínez-Fernández, José; Camps, Adriano; Font, Jordi

2014-05-01

154

Mapping Soils, Vegetation, and Landforms: An Integrative Physical Geography Field Experience*  

E-print Network

Mapping Soils, Vegetation, and Landforms: An Integrative Physical Geography Field Experience, and landform maps of a 1.5-square-mile (3.9 km2 ) study area in southwest Lower Michigan. The learning outcomes the soils, vegetation, and landforms of a complex area would engender a number of learning outcomes as well

Schaetzl, Randall

155

Beryllium7 in soils and vegetation along an arid precipitation gradient in Owens Valley, California  

E-print Network

Beryllium7 in soils and vegetation along an arid precipitation gradient in Owens Valley, California; revised 29 March 2011; accepted 1 April 2011; published 7 May 2011. [1] Beryllium7 is a potentially potential as a sediment tracer in desert environments. Beryllium7 in vegetation and the upper few cm of soil

Elmore, Andrew J.

156

The estimation of the surface moisture of a vegetated soil using aerial infrared photography  

Microsoft Academic Search

The bidirectional reflectance of near infrared wavelengths of electromagnetic radiation from a vegetation canopy is primarily determined by the relative area and reflectance of the canopy and canopy dependent components: leaves, non-green vegetation, soil and shadow. It has been shown that when the percentage cover of leaves and non-green vegetation are both known and constant and the effect of shadow

PAUL J. CURRAN

1981-01-01

157

Monte Carlo simulation model for electromagnetic scattering from vegetation and inversion of vegetation parameters  

E-print Network

In this thesis research, a coherent scattering model for microwave remote sensing of vegetation canopy is developed on the basis of Monte Carlo simulations. An accurate model of vegetation structure is essential for the ...

Wang, Li-Fang, Ph. D. Massachusetts Institute of Technology

2007-01-01

158

Vegetation study in support of the design and optimization of vegetative soil covers, Sandia National Laboratories, Albuquerque, New Mexico.  

SciTech Connect

A vegetation study was conducted in Technical Area 3 at Sandia National Laboratories, Albuquerque, New Mexico in 2003 to assist in the design and optimization of vegetative soil covers for hazardous, radioactive, and mixed waste landfills at Sandia National Laboratories/New Mexico and Kirtland Air Force Base. The objective of the study was to obtain site-specific, vegetative input parameters for the one-dimensional code UNSAT-H and to identify suitable, diverse native plant species for use on vegetative soil covers that will persist indefinitely as a climax ecological community with little or no maintenance. The identification and selection of appropriate native plant species is critical to the proper design and long-term performance of vegetative soil covers. Major emphasis was placed on the acquisition of representative, site-specific vegetation data. Vegetative input parameters measured in the field during this study include root depth, root length density, and percent bare area. Site-specific leaf area index was not obtained in the area because there was no suitable platform to measure leaf area during the 2003 growing season due to severe drought that has persisted in New Mexico since 1999. Regional LAI data was obtained from two unique desert biomes in New Mexico, Sevilletta Wildlife Refuge and Jornada Research Station.

Peace, Gerald (Jerry) L.; Goering, Timothy James (GRAM inc., Albuquerque, NM); Knight, Paul J. (Marron and Associates, Albuquerque, NM); Ashton, Thomas S. (Marron and Associates, Albuquerque, NM)

2004-11-01

159

Reflectance of vegetation, soil, and water. [in Hidalgo County, Texas  

NASA Technical Reports Server (NTRS)

The author has identified the following significant results. A study was conducted in a 340-acre (139 hectares) field of grain sorghum (Sorghum bicolor (L.) Moench) to determine if multispectral data from ERTS-1 could be used to detect differences in chlorophyll concentration between iron-deficient (chlorotic) and apparently normal (green) grain sorghum. Chlorotic sorghum areas 2.8 acres (1.1 hectares) or larger in size were identified on a computer printout of band 5 data which contains the chlorophyll absorption band at the 0.65 micron wavelength. ERTS resolution is sufficient for practical applications in detecting iron-deficient sorghum in otherwise uniform fields. The first classification map of the study county has been produced. Vegetation (crops), rangeland, bare soil, water, and an undefined (all other) category occupied 15.2, 45.0, 19.1, 0.02, and 20.6% of the land area, respectively.

Wiegand, C. L. (principal investigator)

1973-01-01

160

Soil, water, and vegetation conditions in south Texas  

NASA Technical Reports Server (NTRS)

The author has identified the following significant results. Field spectral measurements and laboratory densitometric measurements showed that tree canopy reflectance differences among the Marrs, Redblush, and Valencia varieties in the visible spectral region were due to their different leaf chlorophyll concentrations. Field measurements of visible light reflectance were directly related to the tonal responses on infrared color photos of the varietal tree canopies. Consequently, densitometric measurements of the foliage on the infrared color transparency with red-filtered light successfully discriminated among the three varieties. Reflectance measurements with a field spectroradiometer on nine dates the growing season of two wheat varieties, Milam and Penjamo, documented their spectra over the 0.45 to 2.50 micron wavelength interval associated with plant cover and physiological development. An image analyzer system was used to optically planimeter the percentage of soil background, vegetation and shadow in the vertical photographs taken within the FOV of the spectroradiometer on each measurement date.

Wiegand, C. L.; Gausman, H. W.; Leamer, R. W.; Richardson, A. J.; Everitt, J. H.; Gerbermann, A. H. (principal investigators)

1976-01-01

161

The suitability of using leaf area index to quantify soil loss under vegetation cover  

Microsoft Academic Search

Soil erosion by water under forest cover is a serious problem in southern China. A comparative study was carried out on the\\u000a use of leaf area index (LAI) and vegetation fractional coverage (VFC) in quantifying soil loss under vegetation cover. Five\\u000a types of vegetation with varied LAI and VFC under field conditions were exposed to two rainfall rates (40 mm

Wentai Zhang; Dongsheng Yu; Xuezheng Shi; Hongjie Wang; Zhujun Gu; Xiangyan Zhang; Manzhi Tan

2011-01-01

162

Soil Organic Carbon mapping of partially vegetated agricultural fields with imaging spectroscopy  

NASA Astrophysics Data System (ADS)

Soil Organic Carbon (SOC) is one of the key soil properties, but the large spatial variation makes continuous mapping a complex task. Imaging spectroscopy has proven to be an useful technique for mapping of soil properties, but the applicability decreases rapidly when fields are partially covered with vegetation. In this paper we show that with only a few percent fractional maize cover the accuracy of a Partial Least Square Regression (PLSR) based SOC prediction model drops dramatically. However, this problem can be solved with the use of spectral unmixing techniques. First, the fractional maize cover is determined with linear spectral unmixing, taking the illumination and observation angles into account. In a next step the influence of maize is filtered out from the spectral signal by a new procedure termed Residual Spectral Unmixing (RSU). The residual soil spectra resulting from this procedure are used for mapping of SOC using PLSR, which could be done with accuracies comparable to studies performed on bare soil surfaces (Root Mean Standard Error of Calibration = 1.34 g/kg and Root Mean Standard Error of Prediction = 1.65 g/kg). With the presented RSU approach it is possible to filter out the influence of maize from the mixed spectra, and the residual soil spectra contain enough information for mapping of the SOC distribution within agricultural fields. This can improve the applicability of airborne imaging spectroscopy for soil studies in temperate climates, since the use of the RSU approach can extend the flight-window which is often constrained by the presence of vegetation.

Bartholomeus, Harm; Kooistra, Lammert; Stevens, Antoine; van Leeuwen, Martin; van Wesemael, Bas; Ben-Dor, Eyal; Tychon, Bernard

2011-02-01

163

Infiltration in Icelandic Andisols: the Role of Vegetation and Soil Frost  

Microsoft Academic Search

Soil frost formation, snow distribution, and winter\\/spring\\/summer terminal infiltration rates (TIRs) were quantified in Icelandic Andisols with contrasting vegetation cover types (grassland, spruce and birch woodland, lupine, and sparsely vegetated lava site). TIRs (mm h21; determined with double-ring infiltrometers) were generally higher in unfrozen than in frozen soils (102-369 vs. 9-306, respectively in sandy soils; 28-94 vs. 3-72 in finer-textured

B. Orradottir; S. R. Archer; O. Arnalds; L. P. Wilding; T. L. Thurow

2008-01-01

164

Influence of a parking area on soils and vegetation in an urban nature reserve  

Microsoft Academic Search

We studied the influence of a car park on soil and vegetation within Richmond Park, UK, before and after imposition of fenced\\u000a boundaries restricted public access. Soil and vegetation samples were taken before (once) and after (twice) access restrictions\\u000a were enforced. The over-riding trend in all the data was for soil adjacent to the car park to be less acidic

Peter Shaw; Nigel Reeve

2008-01-01

165

Effects of Salmon-Borne Nutrients on Riparian Soils and Vegetation in Southwest Alaska  

Microsoft Academic Search

Spawning Pacific salmon (Oncorhynchus spp.) contribute marine-derived nutrients to riparian ecosystems, potentially affecting characteristics of the associated soils and vegetation. We quantified these effects by comparing soil and vegetative characteristics upstream and downstream of natural migratory barriers on ten spawning streams in southwest Alaska. Mean ?15N values—indicative of salmon-borne nutrients—were significantly higher in the O horizon and surface mineral soils

Krista K. Bartz; Robert J. Naiman

2005-01-01

166

Influence of vegetation changes on soil organic matter  

NASA Astrophysics Data System (ADS)

In a heath region at Hjelm Hede in Denmark oak trees are invading a Calluna/Empetrum vegetation. In less than a century the oak invasion has caused considerable changes in the soil: what was once an O-horizon under Calluna has changed to an A-horizon under oak; the Calluna E-horizon has lost its distinct appearance; and the sharp boundary between E and Bh has been obliterated. The directly visible changes are associated with a rise in pH of about one unit in the top horizon under the oaks, an increasing content of organic matter in the E-horizon, a decreasing content of organic matter in the Bh-horizon, and a fall in the C/N ratio. In order to estimate the total microbiological activity, cotton strips were placed in the upper soil horizons. The loss in tensile strength during two summer months was 10-15% under Calluna, but more than 50% under oaks. Initial attempts to find differences in the type and content of organic matter showed that the most abundant low-molecular organic acids extracted from the Of-horizons were 3,4-dihydroxybenzoic acid (protocatechuic acid), 4-hydroxybenzoic acid and 4-hydroxy-3-methoxybenzoic acid (vanillic acid). The extraction was done in 0.1 M sodium pyrophosphate at pH 10.2. The organic compounds were determined by HPLC. The 3,4-dihydroxybenzoic acid was relatively the most important compound under the Calluna heath, whereas 4-hydroxy-3-methoxybenzoic acid was most important under oaks. Extractions were performed on water samples from field lysimeter experiments to determine whether the substituted benzoic acids in the soil water arose under transport. These extractions exposed a ppm concentration of 2,4-dichlorobenzoic acid, a compound believed to originate from microbial decomposition of lysimeter material.

Nørnberg, Per

167

Coupling of snow distribution, soil moisture, and vegetation on two subalpine hillslopes  

NASA Astrophysics Data System (ADS)

Subalpine forests are subject to extreme gradients in temperature and soil moisture. This study explores how dynamics of snowmelt and soil moisture relate to tree distribution on two subalpine hillslopes in the Loch Vale watershed in Rocky Mountain National Park, USA. The hillslopes are at approximately 3200 m elevation with 30% average slope. Near tree-line, the hillslopes have a patchy distribution of trees, with Engelmann spruce and subalpine fir covering only about 50% of the hillslope surface area. To determine how forest patch characteristics relate to hydrologic dynamics in these hillslopes, we set up two-hundred meter transects, each extending from a bedrock cliff face upslope to a stream downslope. One transect has a northeast-facing aspect, and the other has a southeast-facing aspect. During summer 2008, we collected weekly or bi-weekly measurements of snow depth, surface soil moisture, and surface soil temperature at 10 m increments along these transects. Under seasonal snow cover, the hillslopes were not completely snow- free until mid July. Snow distribution was highly variable along the hillslopes, with snow persisting longest in clearings between forest patches. Except during the days immediately following snow melt, hillslope soil moisture distributions were uncorrelated with snow distribution and instead reflected localized downslope subsurface flow paths. Trees cluster in segments of the hillslope with the lowest slope gradients, and the largest trees in both hillslopes were located mid-slope, just below steep slope breaks. Although surface soil moisture was consistently higher on the northeast-facing hillslope, trees are on average larger on the southeast-facing slope, which has warmer average temperatures and deeper soils. Results suggest a complex coupling between tree distribution and snowmelt runoff in this transitional environment, and future work will continue to explore these feedbacks by combining more detailed vegetation and soil depth characterization with soil water chemistry and subsurface flow modeling.

Kampf, S. K.; Markus, J.

2008-12-01

168

Modeling Vegetation Amount Using Bandwise Regression and Ecological Site Descriptions as an Alternative to Vegetation Indices  

Microsoft Academic Search

Ecological site descriptions (ESDs) based on soil maps, Landsat 7 ETM+ band values, and vegetation index data from 12 scenes were used as predictive variables in linear regression estimates of total biomass using field data from five Montana ranches. Bandwise regression explained the most variability (53%) when ESDs were not included, followed by tasseled cap components (51%), the soil adjusted

Catherine Lee Maynard; Rick L. Lawrence; Gerald A. Nielsen; Gordon Decker

2006-01-01

169

Hysteresis of soil moisture spatial heterogeneity and the "homogenizing" effect of vegetation  

E-print Network

Hysteresis of soil moisture spatial heterogeneity and the "homogenizing" effect of vegetation 16 September 2010. [1] By partitioning mass and energy fluxes, soil moisture exerts a fundamental experiment, this study investigates aspects of soil moisture spatial and temporal variability in a zeroorder

Troch, Peter

170

Evolution of soil moisture spatial structure in a mixed vegetation pixel during the Southern Great Plains  

E-print Network

Evolution of soil moisture spatial structure in a mixed vegetation pixel during the Southern Great moisture variability at different space scales and timescales, including soil properties, topography-season (intraseasonal) spatiotemporal variability of surface (0­6 cm depth) soil moisture in a quarter section (800 m

Mohanty, Binayak P.

171

NITRATE MOVEMENT IN SOUTHEASTERN COASTAL PLAIN SOILS UNDER CONSERVATION-TILLED VEGETABLE PRODUCTION  

E-print Network

NITRATE MOVEMENT IN SOUTHEASTERN COASTAL PLAIN SOILS UNDER CONSERVATION-TILLED VEGETABLE PRODUCTION G.D. Hoyt1 , D.C. Sanders2 , J.T. D.R. Decoteau3 , ABSTRACT Movement of soil nitrates by leaching. This study measured soil nitrate-N with depth at planting and after cucumber harvest at Clinton, NC, Florence

Decoteau, Dennis R.

172

The influence of variations of vegetation and soil moisture on surface weather and atmospheric circulation  

SciTech Connect

The influence of variations of vegetation and soil moisture on surface weather and atmospheric circulation is studied through the use of the Simple Biosphere Model (SiB) and the Center for Ocean-Land-Atmosphere interactions (COLA) GCM. Tests for the SiB sensitivity to the conversion of the forest to other short vegetation or bare soil were performed at Amazonian and Great Plains sites, and a North Wales spruce forest site respectively. The results show that deforestation has a significant influence on the local surface energy budget and surface weather. The influence is especially prominent at the Amazon and Great Plains sites, and larger in summer than in other seasons. The influence on the partitioning of surface incoming radiative energy is generally constrained by the local atmospheric boundary condition. The sensitivity of the COLA GCM to changes in initial soil wetness (ISW) is determined by repeating three 10-day model integrations with the same initial and boundary conditions as the control runs except the values of ISW, which are revised at 69 model grid points covering much of the continental U.S. It is found that the relations between the changes in the 5-day mean forecast surface air temperature/surface specific humidity and the changes in ISW depend upon vegetation type and the values of ISW, and can be approximated by regression equations. These relations are also confirmed with independent data. With the ISW revised based on these regression equations the surface forecasts of the revised runs are consistently improved. The spatial scale of the ISW anomaly determines the degree and range of the influence. The influence of a small regional ISW change is mainly confined to the local region and to low atmospheric levels. The influence on surface fluxes is strong and persists for more than one month, but the effects on precipitation are relatively weak, changeable, and complex, particularly when an interactive cloud scheme is used.

Yang, R.

1992-01-01

173

Integrated analysis of climate, soil, topography and vegetative growth in iberian viticultural regions.  

PubMed

The Iberian viticultural regions are convened according to the Denomination of Origin (DO) and present different climates, soils, topography and management practices. All these elements influence the vegetative growth of different varieties throughout the peninsula, and are tied to grape quality and wine type. In the current study, an integrated analysis of climate, soil, topography and vegetative growth was performed for the Iberian DO regions, using state-of-the-art datasets. For climatic assessment, a categorized index, accounting for phenological/thermal development, water availability and grape ripening conditions was computed. Soil textural classes were established to distinguish soil types. Elevation and aspect (orientation) were also taken into account, as the leading topographic elements. A spectral vegetation index was used to assess grapevine vegetative growth and an integrated analysis of all variables was performed. The results showed that the integrated climate-soil-topography influence on vine performance is evident. Most Iberian vineyards are grown in temperate dry climates with loamy soils, presenting low vegetative growth. Vineyards in temperate humid conditions tend to show higher vegetative growth. Conversely, in cooler/warmer climates, lower vigour vineyards prevail and other factors, such as soil type and precipitation acquire more important roles in driving vigour. Vines in prevailing loamy soils are grown over a wide climatic diversity, suggesting that precipitation is the primary factor influencing vigour. The present assessment of terroir characteristics allows direct comparison among wine regions and may have great value to viticulturists, particularly under a changing climate. PMID:25251495

Fraga, Helder; Malheiro, Aureliano C; Moutinho-Pereira, José; Cardoso, Rita M; Soares, Pedro M M; Cancela, Javier J; Pinto, Joaquim G; Santos, João A

2014-01-01

174

Integrated Analysis of Climate, Soil, Topography and Vegetative Growth in Iberian Viticultural Regions  

PubMed Central

The Iberian viticultural regions are convened according to the Denomination of Origin (DO) and present different climates, soils, topography and management practices. All these elements influence the vegetative growth of different varieties throughout the peninsula, and are tied to grape quality and wine type. In the current study, an integrated analysis of climate, soil, topography and vegetative growth was performed for the Iberian DO regions, using state-of-the-art datasets. For climatic assessment, a categorized index, accounting for phenological/thermal development, water availability and grape ripening conditions was computed. Soil textural classes were established to distinguish soil types. Elevation and aspect (orientation) were also taken into account, as the leading topographic elements. A spectral vegetation index was used to assess grapevine vegetative growth and an integrated analysis of all variables was performed. The results showed that the integrated climate-soil-topography influence on vine performance is evident. Most Iberian vineyards are grown in temperate dry climates with loamy soils, presenting low vegetative growth. Vineyards in temperate humid conditions tend to show higher vegetative growth. Conversely, in cooler/warmer climates, lower vigour vineyards prevail and other factors, such as soil type and precipitation acquire more important roles in driving vigour. Vines in prevailing loamy soils are grown over a wide climatic diversity, suggesting that precipitation is the primary factor influencing vigour. The present assessment of terroir characteristics allows direct comparison among wine regions and may have great value to viticulturists, particularly under a changing climate. PMID:25251495

Fraga, Helder; Malheiro, Aureliano C.; Moutinho-Pereira, Jose; Cardoso, Rita M.; Soares, Pedro M. M.; Cancela, Javier J.; Pinto, Joaquim G.; Santos, Joao A.

2014-01-01

175

Phytoavailability of thallium - A model soil experiment  

NASA Astrophysics Data System (ADS)

The study deals with the environmental stability of Tl-modified phases (ferrihydrite, goethite, birnessite, calcite and illite) and phytoavailability of Tl in synthetically prepared soils used in a model vegetation experiment. The obtained data clearly demonstrate a strong relationship between the mineralogical position of Tl in the model soil and its uptake by the plant (Sinapis alba L.). The maximum rate of Tl uptake was observed for plants grown on soil containing Tl-modified illite. In contrast, soil enriched in Ksat-birnessite had the lowest potential for Tl release and phytoaccumulation. Root-induced dissolution of synthetic calcite and ferrihydrite in the rhizosphere followed by Tl mobilization was detected. Highly crystalline goethite was more stable in the rhizosphere, compared to ferrihydrite, leading to reduced biological uptake of Tl. Based on the results, the mineralogical aspect must be taken into account prior to general environmental recommendations in areas affected by Tl.

Vanek, Ales; Mihaljevic, Martin; Galuskova, Ivana; Komarek, Michael

2013-04-01

176

Calculation set for design and optimization of vegetative soil covers Sandia National Laboratories, Albuquerque, New Mexico.  

SciTech Connect

This study demonstrates that containment of municipal and hazardous waste in arid and semiarid environments can be accomplished effectively without traditional, synthetic materials and complex, multi-layer systems. This research demonstrates that closure covers combining layers of natural soil, native plant species, and climatic conditions to form a sustainable, functioning ecosystem will meet the technical equivalency criteria prescribed by the U. S. Environmental Protection Agency. In this study, percolation through a natural analogue and an engineered cover is simulated using the one-dimensional, numerical code UNSAT-H. UNSAT-H is a Richards. equation-based model that simulates soil water infiltration, unsaturated flow, redistribution, evaporation, plant transpiration, and deep percolation. This study incorporates conservative, site-specific soil hydraulic and vegetation parameters. Historical meteorological data are used to simulate percolation through the natural analogue and an engineered cover, with and without vegetation. This study indicates that a 3-foot (ft) cover in arid and semiarid environments is the minimum design thickness necessary to meet the U. S. Environmental Protection Agency-prescribed technical equivalency criteria of 31.5 millimeters/year and 1 x 10{sup -7} centimeters/second for net annual percolation and average flux, respectively. Increasing cover thickness to 4 or 5 ft results in limited additional improvement in cover performance.

Peace, Gerald L.; Goering, Timothy James (GRAM, Inc., Albuquerque, NM)

2005-02-01

177

The Changing Model of Soil  

NASA Astrophysics Data System (ADS)

The contemporary genetic model of soil is changing rapidly in response to advances in soil science and to human and environmental forcings in the 21st century (Richter and Yaalon, 2012). Three ongoing changes in the model of soil include that: (1) lower soil boundaries are much deeper than the solum, historically the O to B horizons, (2) most soils are polygenetic paleosols, products of soil-forming processes that have ranged widely over soils' lifetimes, and (3) soils are globally human-natural bodies, no longer natural bodies. Together, these changes in the model of soil mean that human forcings are a global wave of soil polygenesis altering fluxes of matter and energy and transforming soil thermodynamics as potentially very deep systems. Because soils are non-linear systems resulting from high-order interactions of physics, chemistry, and biology, trajectories of how human forcings alter soils over decades are not readily predictable and require long-term soil observations. There is much to learn about how soils are changing internally as central components of management systems and externally in relation to wider environments. To be critical, research has been remarkably superficial in studies of soil, reductionist in approach, and lacking in time-series observations of responses to soil management. While this criticism may sound negative, it creates significant opportunities for contemporary soil scientists.

Richter, D. D.; Yaalon, D.

2012-12-01

178

Effects of changing channel morphology on vegetation, groundwater, and soil moisture regimes in groundwater dependent ecosystems  

NASA Astrophysics Data System (ADS)

Channel incision and excessive floodplain sedimentation are major causes of riparian degradation across the country. Though the causes and consequences of these processes vary significantly, the resulting morphology in both cases is steep streambanks and a stream that is less connected with the floodplain. A case study from semi-arid, wet meadows with snow-melt driven hydrology in the Sierra Nevada of CA will be compared with one from a riparian wet prairie in the humid environment of the Driftless Area of southern Wisconsin. In the mountain meadows, 80 years of logging and overgrazing led to more flashy runoff and downcutting of the stream. This led to drainage of groundwater from the meadow and a shift in vegetation composition from sedges and rushes to dryland grasses and sagebrush in this groundwater dependent ecosystem. In the Driftless Area of WI, the introduction of agricultural practices by European settlers in the 1830s resulted in severe erosion from the cropped areas in the uplands. This sediment was transported to the stream valleys where it was deposited on the floodplain, raising this surface relative to the streambed. As a result, the water table is at a greater depth from this elevated land surface. In this ecosystem, the vegetation has shifted from wet prairie and sedge meadow communities to grasses and lowland forests dominated by box elder trees. The geomorphic result at both sites was a channel bounded by tall banks with reduced hydrologic connectivity with the floodplain. In both cases, the slope of the water table towards the stream is greater than the topographic slope across the riparian zone and the greatest depth to the water table is found adjacent to the channel. Transects exhibit a decreasing trend in soil moisture with increasing variability toward the channel. Remotely sensed imagery shows trends of drier vegetation communities adjacent to channels and wetter vegetation communities toward the margin of the riparian zones. Coupled hydrologic and vegetation models describing the effects following channel incision or excessive floodplain sedimentation are consistent with water table, soil moisture and vegetation observations. These case studies illustrate the role channel morphology plays in controlling vegetation patterning of riparian zones via the groundwater hydrologic linkage.

Loheide, S. P.; Booth, E. G.

2008-12-01

179

Effects of detailed soil spatial information on watershed modeling across different model scales  

Microsoft Academic Search

Hydro-ecological modelers often use spatial variation of soil information derived from conventional soil surveys in simulation of hydro-ecological processes over watersheds at mesoscale (10–100km2). Conventional soil surveys are not designed to provide the same level of spatial detail as terrain and vegetation inputs derived from digital terrain analysis and remote sensing techniques. Soil property layers derived from conventional soil surveys

Trevor Quinn; A.-Xing Zhu; James E. Burt

2005-01-01

180

Direct leaf wetness measurements and its numerical analysis using a multi-layer atmosphere-soil-vegetation model at a grassland site in pre-alpine region in Germany  

NASA Astrophysics Data System (ADS)

The wetness of plant leaf surfaces (leaf wetness) is important in meteorological, agricultural, and environmental studies including plant disease management and the deposition process of atmospheric trace gases and particles. Although many models have been developed to predict leaf wetness, wetness data directly measured at the leaf surface for model validations are still limited. In the present study, the leaf wetness was monitored using seven electrical sensors directly clipped to living leaf surfaces of thin and broad-leaved grasses. The measurements were carried out at the pre-alpine grassland site in TERestrial ENvironmental Observatories (TERENO) networks in Germany from September 20 to November 8, 2013. Numerical simulations of a multi-layer atmosphere-SOiL-VEGetation model (SOLVEG) developed by the authors were carried out for analyzing the data. For numerical simulations, the additional routine meteorological data of wind speed, air temperature and humidity, radiation, rainfall, long-wave radiative surface temperature, surface fluxes, ceilometer backscatter, and canopy or snow depth were used. The model reproduced well the observed leaf wetness, net radiation, momentum and heat, water vapor, and CO2 fluxes, surface temperature, and soil temperature and moisture. In rain-free days, a typical diurnal cycle as a decrease and increase during the day- and night-time, respectively, was observed in leaf wetness data. The high wetness level was always monitored under rain, fog, and snowcover conditions. Leaf wetness was also often high in the early morning due to thawing of leaf surface water frozen during a cold night. In general, leaf wetness was well correlated with relative humidity (RH) in condensation process, while it rather depended on wind speed in evaporation process. The comparisons in RH-wetness relations between leaf characteristics showed that broad-leaved grasses tended to be wetter than thin grasses.

Katata, Genki; Held, Andreas; Mauder, Matthias

2014-05-01

181

An Idealized Model of Plant and Soil Dynamics  

NASA Astrophysics Data System (ADS)

Following wildfire events the landscape commonly becomes denuded of vegetation cover, resulting in systems prone to soil loss and degradation. In this context soil dynamics are an intricate process balanced between pedogenesis, which is a relatively slow process and erosion which depends on many inert (e.g. soil texture, slope, precipitation and wind) and biological factors such as vegetation properties, grazing intensity, and human disturbance. We develop a simple homogenous, spatially implicit, theoretical model of the global dynamics of the interactions between vegetation and soil using a system of two nonlinear differential equations describing this interdependence, assuming a double feedback between them - plants control erosion and soil availability facilitates plants growth: ( ) dV- -K-- dt = rV K - 1+ aS - V (1) dS-= ? - ?Se-cT dt (2) where V and S represent vegetation cover and soil availability, respectively. Vegetation growth is similar to the classical logistic model with a growth rate of r(yr1), however, the "carrying capacity" (K) is dependent on soil availability (a1 is the amount of soil where V is reduced by half). Soil influxes at a constant rate ?(mm×yr1) and is eroded at a constant rateg? (yr-1), while vegetation abates this process modeled as a decreasing exponent as the effectiveness of vegetation in reducing soil erosion (c). Parameter values were chosen from a variable range found in the literature: r=0.01 yr1, K=75%, a1=1, ?=1 mm×yr1, ?=0.1 yr1, c=0.08. Complex properties emerge from this model. At certain parameter values (cK?4) the model predicts one of two steady states - full recovery of vegetation cover or a degraded barren system. However, at certain boundary conditions (cK>4 and ?1 ? ?/? ? ?2, see Article for terms of ?1 and ?2) bistability may be observed. We also show that erosion seems to be the determining factor in this system, and we identify the threshold values from which beyond the systems become unstable. The model predicts that certain ecosystems will be highly stable in one of two states, while others might be bistable transitioning between these two states through perturbations. This is an indicator of hysteresis, possibly indicating the ability of the system to shift leading to sudden and dramatic changes; formalizing the conceptual model shown by Davenport et al. (1998) and others. Following the establishment of these interrelationships, the role of repeated disturbances, such as wildfires, was assessed with numerical analysis in determining the long term dynamics of coupled soil-vegetation systems.

Burg, David; Malkinson, Dan; Wittenberg, Lea

2014-05-01

182

Improving Thermal IR Sensor-Derived Soil Moisture Mapping of the Walnut Gulch Experimental Watershed, SE Arizona using Soil Texture and Vegetation Data  

NASA Astrophysics Data System (ADS)

Soil moisture studies, especially those in semi-arid environments, are critical in understanding weather, climate, agricultural productivity, society impact, and national security. However, studying this type of environment is often difficult and costly due to remote locations, rapid dry-down following precipitation events, and required specialized equipment. In order to overcome these obstacles, remotely sensed data has been employed with limited success, as these measurements are at coarse spatial resolutions on the order of 10 km or more [e.g, 1]. Recent approaches of retrieving soil moisture have shown promise by utilizing the sensor-derived apparent thermal inertia (ATI) of the surface from higher spatial resolution imagers, including the Moderate Resolution Imaging Spectroradiometer (MODIS; 1 km) and the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER; 90 m) [e.g, 2]. We attempt to improve the ATI algorithm by analyzing comparisons between the sensor-derived values and in-situ field data from the Walnut Gulch Experimental Watershed (WGEW) in southeastern Arizona. Modeled soil moisture was derived from a 10-year time series of archival MODIS data and 2 day/night acquisitions of ASTER data, accommodating for differences in scale. To accomplish this task: 1) high spatial resolution soil moisture maps were created, 2) the algorithm results were validated with an extensive open-source network of in-situ rain and 5 cm depth soil moisture gauge data, and 3) the soil moisture retrievals were adjusted for heterogeneous soils and vegetation cover. A proxy for soil texture is derived from associated mineral maps, produced by linear spectral deconvolution of emissivity [3 and 4] and validated by the open source WGEW soil maps. Vegetation influence is determined from VNIR data using standard band ratios. The results of this analysis will aim to improve the algorithm, and more accurately derive soil moisture by accounting for soil texture and vegetation. Future work will provide spectral ground truth of targeted areas using a handheld, portable FTIR spectrometer, accounting for the effects of atmospheric attenuation and vegetation type. These field activities will validate soil composition maps produced from ASTER TIR and improve proxy data for soil texture. The results of this study will not only provide high spatial resolution soil moisture maps for semi-arid environments, it will also show the importance of amalgamating multiple remote sensing techniques to solve problems occurring in similar environments worldwide. (1) Distribution Statement A -- Approved for public release; distribution is unlimited.

Rose, S.; Scheidt, S. P.; Tischler, M.

2011-12-01

183

Effects of Wastewater Irrigation on Physicochemical Properties of Soil and Availability of Heavy Metals in Soil and Vegetables  

Microsoft Academic Search

The present study investigated the impact of irrigation with wastewater on nutritional property and heavy?metal concentrations in the soil and consequent accumulation in vegetables at sites having long?term uses of wastewater for irrigation. Samples of irrigation water, soil, and root and shoot parts of palak plants were analyzed to determine the concentration of heavy metals. Wastewater irrigation led to increases

Anita Singh; Rajesh K. Sharma; Madhoolika Agrawal; F. Marshall

2009-01-01

184

Soil-vegetation correlations in selected wetlands and uplands of North-Central Florida  

USGS Publications Warehouse

Vegetation on four hydric and two nonhydric soils series in north-central Florida was sampled as part of a national study examining the correspondence between wetland vegetation and soils. The wetland character of the vegetation was estimated by weighted average calculations using published wetland indicator values for individual plant species. The weighted averages produced an ordering of plant communities in general agreement with the hydric character of the soils. However, the two nonhydric soils has weighted average scores slightly below 3, normally considered the lowest end of the range of nonhydric vegetation. There was no clear or consistent effect of fire management on the weighted average scores. Vegetation strata (herbaceous, low shrub, tall shrub, and trees) were generally similar in weighted average values, with the wettest of the hydric soils tending to be low in all strata and the nonhydric soils tending to be high in all strata. However, strata differed considerably in the specific values for a single soil and in the specific rank ordering of soils in different strata.

Best, G. Ronnie; Wolfe, Charlotte; Segal, Debra S.

1990-01-01

185

Dual frequency microwave radiometer measurements of soil moisture for bare and vegetated rough surfaces  

E-print Network

DUAL FREQUENCY MICROWAVE RADIOMETER MEASUREMENTS OF SOIL MOISTURE FOR BARE AND VEGETATED ROUGH SURFACES A Thesis by SIU LIM LEE Submitted to the Graduate College of Texas A(M University in partial fulfillment of the requirement for the degree... of MASTER OF SCIENCE August 1974 Major Subject: Electrical Engineering DUAL FREQUENCY MICROWAVE RADIOMETER MEASUREMENTS OF' SOIL MOISTURE FOR BARE AND VEGETATED ROUGH SURFACES A Thesis by SIU LIM LEE Approved as to style and content by: (C rman...

Lee, Siu Lim

2012-06-07

186

Characteristic of soil hydro-physical properties and water dynamics under different vegetation restoration types  

Microsoft Academic Search

By combining the observation of the soil profile at field and the chemical and physical analysis in laboratory, a study on\\u000a the hydro-physical properties of soil in six different vegetation types and the dynamics of water content after rain was conducted\\u000a in Wanchanggou, Guangyuan City to find out the vegetation types with effective water-conservation functions in order to serve\\u000a the

Ma Zelong; Gong Yuanbo; Hu Tingxing

2006-01-01

187

Precontact vegetation and soil nutrient status in the shadow of Kohala Volcano, Hawaii  

Microsoft Academic Search

Humans colonized Hawaii about 1200 years ago and have progressively modified vegetation, particularly in mesic to dry tropical forests. We use ?13C to evaluate the contribution of C3 and C4 plants to deep soil organic matter to reconstruct pre-human contact vegetation patterns along a wet to dry climate transect on Kohala Mountain, Hawaii Island. Precontact vegetation assemblages fall into three distinct

Oliver A. Chadwick; Eugene F. Kelly; Sara C. Hotchkiss; Peter M. Vitousek

2007-01-01

188

Variability of soil microbial respiration under different vegetation succession stages in Jiuduansha wetland  

Microsoft Academic Search

The soil microbial respiration (SMR) and physicochemical characteristics of Jiuduansha wetland at the Yangtze Estuary were analyzed in order to clarify the variability of SMR under different vegetation succession stages and its influencing factors. The results indicated that SMR of different vegetation succession stages are significantly various (P < 0.05). The SMR of the Spartina alterniflora (S. alterniflora) zone (0.43

Yushu Tang; Lei Wang; Jianwei Jia; Yanli Li; Wenquan Zhang; Hongli Wang; Xiaohua Fu; Yiquan Le

2011-01-01

189

Vegetation and its relation to soil nutrient and salinity in the Calabar mangrove swamp, Nigeria  

Microsoft Academic Search

The study examines vegetation – environment relationships. Vegetation measurements included species frequency, density, diameter and tree height, while environmental measurements were soil particle size distribution, acid properties (pH, Al, SO4), nutrient cations (Ca, Na, Mg, K), organic carbon, nitrogen, phosphorus and chloride content. Nypa fruticans was the dominant species in the A stratum (> 3 m tall) while Rhizophora mangle

Imoh E. Ukpong

1997-01-01

190

Fertility Element Storage in Chaparral Vegetation, Leaf Litter, and Soil1  

E-print Network

Fertility Element Storage in Chaparral Vegetation, Leaf Litter, and Soil1 Paul J. Zinke2 Gen. Tech; and Ceanothus cuneatus, & C. crassifolius. Data for elemental composition, total vegetation and leaf litter weights, and elemental storage weights for each of these species were determined. These data

Standiford, Richard B.

191

Chemical evaluation of vegetables grown with conventional or organic soil amendments  

Microsoft Academic Search

Garden vegetables were grown with “organic”; or “commercial”; fertilizer amendments to the soil. Plot preparation and other general cultural practices were identical. Tomatoes, potatoes, peppers, lettuce, onions and peas were planted, and leaf tissue and edible produce were harvested. N, P, K, Ca and Mg and content of ascorbic acid were determined in some of the produce. Certain vegetables were

L. V. Svec; C. A. Thoroughgood; Hyo Chung S. Mok

1976-01-01

192

Effects of Woody Vegetation Removal on Soil Water Dynamics in a South Texas Shrubland  

E-print Network

the root zone of plants. Water moving beyond the root zone is referred to as deep drainage, and has potential to become aquifer recharge. A vegetation manipulation project was designed to understand the effects of woody vegetation removal on soil water...

Mattox, April Marie

2013-07-30

193

Capturing Vegetation Diversity in the Ent Terrestrial Biosphere Model  

NASA Astrophysics Data System (ADS)

We present preliminary results from data mining to develop parameter sets and global vegetation structure datasets to set boundary conditions for the Ent Terrestrial Biosphere Model (Ent TBM) for improved representation of diversity and to propagate uncertainty in simulations of land carbon dynamics in the 20th century and under future climate change. The Ent TBM is the only dynamic global vegetation model (DGVM) developed for coupling with general circulation models (GCMs) to account for the height structure of mixed canopies, including a canopy radiative transfer scheme that accounts for foliage clumping in dynamically changing canopies. It is flexibly programmed to incorporate any number of "plant functional types" (PFTs). It is now a coupled component of the ModelE2 version of the NASA Goddard Institute for Space Studies (GISS) general circulation model (GCM). We demonstrate a data mining method, linear manifold clustering, to be used with several very recently compiled large databases of plant traits and phenology combined with climate and satellite data, to identify new PFT groupings, and also conduct customized parameter fits of PFT traits already defined in Ent. These parameter sets are used together with satellite-derived global forest height structure and land cover derived from a combination of satellite and inventory sources and bioclimatic relations to provide a new estimate and uncertainty bounds on vegetation biomass carbon stocks. These parameter sets will also be used to reproduce atmospheric CO2 time series over the flask observational period, to evaluate the impact of improved representation of vegetation dynamics on soil carbon stocks, and finally to produce a projection of the land carbon sink under future climate change. This research is timely in taking advantage of new, globally ranging vegetation databases, satellite-derived forest heights, and the advanced framework of the Ent TBM. It will advance understanding of and reduce uncertainty in land carbon dynamics and stocks through development, implementation, and evaluation of new parameterizations for a DGVM, parameterizations which will expand and or revise representation of vegetation diversity in the Earth system or replace modules or static parameters with more continuous, functional schemes.

Kiang, N. Y.; Haralick, R. M.; Cook, B.; Aleinov, I. D.

2013-12-01

194

Soil Reflectance Modeling With A Global Spectral Library: Refinement of The Price Soil Reflectance Model  

NASA Astrophysics Data System (ADS)

Modeling soil reflectance is important to describe the soil-vegetation radiation field and to retrieve canopy characteristics from remote sensing data. The Price soil reflectance model has been widely used in canopy reflectance modeling thanks to its simplicity and effectiveness. In order to improve the model generality and applicability, this study refines the Price soil reflectance model using a global spectral library and further proposes a novel soil reflectance model. The global soil spectral library was combined from six datasets, containing 6,971 soil samples around the world, with a 10nm interval from 450 to 2350 nm. A recalibrated Price model (CPM) was developed using the same algorithm used by standard Price model (SPM) to obtain globally representative fitting functions. Moreover, a new matrix decomposition method (MDM) was developed to decrease the reflectance simulation errors by considering the spectra curve shapes. Three tune parameters are sufficient to model global soil spectra using MDM, which achieves the highest accuracy with an absolute error less than 0.02 and relative error less than 5%. CPM and SPM have larger simulation errors, for which the RMSE/RRMSE are 0.029/7.5% and 0.068/16.8%, respectively. For both SPM and CPM, relatively large error variations are shown over wavelengths, because only three selected bands are used in the models. MDM exhibits a relatively stable performance in the whole spectral domain. Moreover, MDM reconstructs very well the general shapes of the five types of soil reflectance curves, and thus leads to a lower misclassification rate. Overall, both CPM and MDM outperform SPM and have a potential for global soil reflectance modeling. Density scatter plots between the measured reflectances in the global soil spectral library and the simulated reflectances using SPM (a), CPM (b) and MDM (c). Comparison of measured and simulated reflectances for five typical curves.

Jiang, C.; Fang, H.

2012-12-01

195

Changes in regional boreal climate due to historic and future structural vegetation changes and variations in soil moisture memory  

NASA Astrophysics Data System (ADS)

Amplified warming at high latitudes over the past decades already has led to, and will continue to lead to, changes in the boreal and arctic part of the climate system. Climate change induced alterations include structural shifts in high latitude ecosystems such as boreal forest expansion towards higher latitudes and altitudes, and shrub-ecosystems replacing tundra in large areas of the arctic. These shifts affect surface physical qualities such as albedo, roughness length, and soil properties. Shifts in vegetation species may also lead to alterations in soil- and boundary layer moisture. Resultant changes in land surface properties and processes provide important feedbacks to regional climate by changes in radiation, and water and energy fluxes. Structural vegetation changes that appear on local scale may through these feedback mechanisms also propagate to affect large scale climatic features. In this study, the Weather Research and Forecasting model (WRF) with the Noah Land surface model is used in a series of experiments in order to investigate the influence of observed and anticipated structural changes in the boreal ecosystem on changes in the land-atmosphere feedbacks. MODIS land surface data are used together with observational data and dynamical vegetation model output from the CMIP5 database, to simulate the influence of historical and future structural vegetation changes over the Northern European Boreal domain. In a series of three experiments the MODIS dataset is manually altered in order to reflect observed and anticipated changes in Boreal forest geography on summer water and energy fluxes at the surface, including Bowen ratio changes. As results are highly sensitive to soil moisture variations, experiments are conducted under wet and dry soil moisture regimes, to take into account uncertainties in future soil state projections and to estimate sensitivity to soil moisture memory in surface flux estimates.

Rydsaa, Johanne H.; Stordal, Frode; Tallaksen, Lena M.

2014-05-01

196

Spatial heterogeneity of soil properties and vegetation–soil relationships following vegetation restoration of mobile dunes in Horqin Sandy Land, Northern China  

Microsoft Academic Search

Quantitative methods were used to examine soil properties and their spatial heterogeneity in a 0-year fenced mobile dune (MD0),\\u000a an 11-year fenced mobile dune (MD11) and a 20-year fenced mobile dune (MD20) in Horqin Sandy Land, Northern China. The objective\\u000a of the study was to assess the effect of vegetation restoration on heterogeneity of soil properties in sand dunes and

Xiaoan Zuo; Xueyong Zhao; Halin Zhao; Tonghui Zhang; Yirui Guo; Yuqiang Li; Yingxin Huang

2009-01-01

197

Static headspace analysis of volatile organic compounds in soil and vegetation samples for site characterization.  

SciTech Connect

Traditional methodologies for the characterization of volatile organic compounds (VOCs) in subsurface soil are expensive, time-consuming processes that are often conducted on samples collected at random. The determination of VOCs in near-surface soils and vegetation is the foundation for a more efficient sampling strategy to characterize subsurface soil and improve understanding of environmental problems. In the absence of a standard methodology for the determination of VOCs in vegetation and in view of the high detection limits of the method for soils, we developed a methodology using headspace gas chromatography with an electron capture detector for the determination of low levels (parts-per-billion to parts-per-trillion) of VOCs in soils and vegetation. The technique demonstrates good sensitivity, good recoveries of internal standards and surrogate compounds, good performance, and minimal waste. A case study involving application of this technique as a first-step vadose-zone characterization methodology is presented.

Alvarado, J. S.; Rose, C. M.; Environmental Research

2004-01-09

198

Assessing the soil texture specific sensitivity of simulated soil moisture to projected climate change by SVAT modelling  

NASA Astrophysics Data System (ADS)

Climate change is assumed to have a regionally specific impact on the soil moisture regime. The impact of climate change on the soil moisture can be expected to depend on the soil texture. Since soil moisture observations are not available operationally, models can be used to elaborate such sensitivity. In this study, a soil vegetation atmosphere transfer scheme (SVAT) was applied to virtual soil columns to assess the soil texture specific sensitivity of simulated soil moisture to projected climate change. For each of the 31 soil texture classes of the German soil texture classification, long term simulations were carried out based on observed and scenario based climate data representing five different climate regions in Germany. The simulation results indicate that soil moisture regimes considerably differ from region to region and among different soil texture classes. Different soil texture classes showed different sensitivities of soil moisture with respect to projected climate change. While differences in soil moisture between current conditions and SRES climate scenarios were largest for silt soils, they were smallest for clay soils for continental as well as humid climates. Sand and loam soils behaved intermediately, showing a moderate sensitivity. The results also showed that soil texture specific sensitivity of soil moisture to climate change was largest for soils which were not affected by groundwater (no capillary rise). With an increasing influence of groundwater, differences between soil texture classes decreased. In contrast, increasing vegetation density, rooting depths and transpiration demand induced an increasing sensitivity of soil moisture to climate change except for continental climates. This study indicates that validated, physical based soil hydrological models serve as suitable tools to assess the response of soil moisture to changing climate conditions. Based on virtual soil columns, modelling experiments systematically reveal soil texture dependent sensitivities which can hardly be identified in real world studies due to limited availability and accessibility of the wide spectrum of different soil textures.

Bormann, H.

2012-04-01

199

Bioremediation of petroleum contaminated soil using vegetation: A microbial study  

Microsoft Academic Search

The degradation of selected petroleum hydrocarbons in the rhizosphere of alfalfa was investigated in a greenhouse experiment. Petroleum contaminated and uncontaminated soils were spiked with 100 ppm of polynuclear aromatic and aliphatic hydrocarbons. Unspiked, uncontaminated soil was used as a control. Microbial counts for soils with and without plants for each soil treatment were performed 4, 8, 16, and 24

Euisang Lee; M. K. Banks

1993-01-01

200

Modeled, climate-induced vegetation change at landscape, continental and global scales  

SciTech Connect

A vegetation distribution model has been constructed based on a mechanistic simulation of site water balance and vegetation leaf area index (LAI). Transpiration is deterministically related to LAI and stomatal conductance. The model predicts leaf area indices of woody and grass vegetation, such that soil water is just utilized during the growing season. The model (MAPSS) has been successfully calibrated to regional, continental and global vegetation patterns and is currently being implemented at a landscape scale. At the global scale, over thirty unique vegetation types are simulated. Under most 2XCO[sub 2] climatic scenarios, global forests undergo drought-induced decline, with decline being most severe in temperate and boreal regions. Increased drought stress is largely imparted by increases in Potential evapotranspiration that more than offset regional increases in precipitation. CO[sub 2]-induced, increased water-use-efficiency is more than negated under most future scenarios.

Neilson, R.P. (Forest Service, Corvallis, OR (United States))

1993-06-01

201

Multi-discipline resource inventory of soils, vegetation and geology  

NASA Technical Reports Server (NTRS)

The author has identified the following significant results. Computer classification of natural vegetation, in the vicinity of Big Summit Prairie, Crook County, Oregon was carried out using MSS digital data. Impure training sets, representing eleven vegetation types plus water, were selected from within the area to be classified. Close correlations were visually observed between vegetation types mapped from the large scale photographs and the computer classification of the ERTS data (Frame 1021-18151, 13 August 1972).

Simonson, G. H. (principal investigator); Paine, D. P.; Lawrence, R. D.; Norgren, J. A.; Pyott, W. Y.; Herzog, J. H.; Murray, R. J.; Rogers, R.

1973-01-01

202

Soil chemistry of local vegetation gradients in sandy calcareous grasslands  

Microsoft Academic Search

Acidification and N-deposition are continuous processes that alter the composition of plant communities. We investigated vegetation\\u000a transitions in sandy grasslands and tested two hypotheses: (1) a shift from vegetation dominated by Koeleria glauca to one dominated by Corynephorus canescens is due to acidification and (2) a shift from vegetation dominated by K. glauca to one dominated by Arrhenatherum elatius is

Linda-Maria Mårtensson; Pål Axel Olsson

2010-01-01

203

A multi-frequency radiometric measurement of soil moisture content over bare and vegetated fields  

NASA Technical Reports Server (NTRS)

A USDA Beltsville Agricultural Research Center site was used for an experiment in which soil moisture remote sensing over bare, grass, and alfalfa fields was conducted over a three-month period using 0.6 GHz, 1.4 GHz, and 10.6 GHz Dicke-type microwave radiometers mounted on mobile towers. Ground truth soil moisture content and ambient air and sil temperatures were obtained concurrently with the radiometric measurements. Biomass of the vegetation cover was sampled about once a week. Soil density for each of the three fields was measured several times during the course of the experiment. Results of the radiometric masurements confirm the frequency dependence of moisture sensing sensitivity reduction reported earlier. Observations over the bare, wet field show that the measured brightness temperature is lowest at 5.0 GHz and highest of 0.6 GHz frequency, a result contrary to expectation based on the estimated dielectric permittivity of soil water mixtures and current radiative transfer model in that frequency range.

Wang, J. R.; Schmugge, T. J.; Mcmurtrey, J. E., III; Gould, W. I.; Glazar, W. S.; Fuchs, J. E. (principal investigators)

1981-01-01

204

Soil vulnerability to future climate in the southwestern USA, with implications for vegetation change and water cycle  

NASA Astrophysics Data System (ADS)

Understanding soil response to changes in precipitation/snow cover and increasing temperatures is essential to predicting changes in riparian, wetland, and aquatic as well as terrestrial communities in the coming decades. Changes in precipitation and snowmelt are affecting streamflow seasonality and magnitude, and rising air temperatures and declining precipitation affect aquatic habitats directly by causing increases in stream temperatures and evapo-transpiration causing lower streamflow. The water resources of the Colorado River system are projected to be strained due to runoff losses of 7 to 20% this century, and a reduction of approximately 5% of the annual average runoff is due to increased evapotranspiration from early exposure of vegetation and soils. We are developing a spatially-explicit soil vulnerability index of high, moderate and low sensitivity soils for the southwestern USA and comparing it to projections of vegetation dieback under future climate change scenarios to provide 1) a measure of uncertainty of the model skill and 2) a warning that vegetation shifts may increase soil vulnerability in areas where it is still protected by current plant cover, thus enabling a preliminary estimate of the future location of sources of aeolian dust.

Peterman, W. L.; Bachelet, D. M.

2011-12-01

205

[Characteristics of soil microelements contents in the rhizospheres of different vegetation in hilly-gully region of Loess Plateau].  

PubMed

To explore the rhizosphere effect of the microelements in the soils under different vegetation types in Loess Plateau, this paper analyzed the organic C, total N, Mn, Cu, Fe, and Zn contents in the rhizosphere soil and bulk soil of six vegetation types in hilly-gully region of Loess Plateau. Among the six vegetation types, Caragana korshinskii, Heteropappus altaicus, and Artemisia capillaries had higher organic C and total N contents in rhizosphere soil than in bulk soil. With the exception of C. korshinskii and H. rhamnoides, all the six vegetation types had a significantly lower pH in rhizosphere soil than in bulk soil. The six vegetation types had a lower available Mn content in rhizosphere soil than in bulk soil, and the C. korshinskii, Astragalus adsurgen, and Panicum virgatum had a significantly higher available Cu content in rhizosphere soil than in bulk soil. The six vegetation types except A. adsurgens had a slightly higher available Fe content in rhizosphere soil than in bulk soil, and A. adsurgens, P. virgatum, H. altaicus, and A. capillaries had a significant accumulation of available Zn in rhizosphere soil. There existed significant positive correlations between the rhizosphere soil and bulk soil of the six vegetation types in the relationships between the organic C and total N contents and the available Mn and Zn contents and between the contents of available Mn and Zn. In rhizosphere soil, available Mn and Zn contents were significantly negative- ly correlated with pH value. Due to the differences in root growth characteristics, rhizosphere pH value, and microbial structure composition, the microelements contents in the rhizosphere soil of the six vegetation types differed, with the contents of Mn, Cu, Fe, and Zn being higher in the rhizosphere soil of H. altaicus than in that of the other vegetation types. PMID:22720606

Zhang, Chao; Liu, Guo-Bin; Xue, Sha; Zhang, Chang-Sheng

2012-03-01

206

Irrigation Requirement Estimation Using Vegetation Indices and Inverse Biophysical Modeling  

NASA Technical Reports Server (NTRS)

We explore an inverse biophysical modeling process forced by satellite and climatological data to quantify irrigation requirements in semi-arid agricultural areas. We constrain the carbon and water cycles modeled under both equilibrium, balance between vegetation and climate, and non-equilibrium, water added through irrigation. We postulate that the degree to which irrigated dry lands vary from equilibrium climate conditions is related to the amount of irrigation. The amount of water required over and above precipitation is considered as an irrigation requirement. For July, results show that spray irrigation resulted in an additional amount of water of 1.3 mm per occurrence with a frequency of 24.6 hours. In contrast, the drip irrigation required only 0.6 mm every 45.6 hours or 46% of that simulated by the spray irrigation. The modeled estimates account for 87% of the total reported irrigation water use, when soil salinity is not important and 66% in saline lands.

Bounoua, Lahouari; Imhoff, Marc L.; Franks, Shannon

2010-01-01

207

Reclaiming Hard Rock Mines: An In Depth Look at Vegetation, Soil, and Water on the Bullion  

E-print Network

with tailings piles, waste rock and acid mine drainage (AMD; Figure 1). Waste rock, the soil and rock material of contamination on abandoned mine sites. One of the most difficult problems to address in mine reclamation is AMDReclaiming Hard Rock Mines: An In Depth Look at Vegetation, Soil, and Water on the Bullion Mine

Maxwell, Bruce D.

208

The vegetation of ultrabasic soils on the Isle of Rhum II. The causes of the debris  

Microsoft Academic Search

The relationship between the Rhum ultrabasic skeletal soils and their debris vegetation was investigated by plant analyses and field and laboratory experiments. Samples of Agrostis vinealis, Arenaria norvegica ssp norvegica, Calluna vulgaris, Festuca vivipara, Plantago maritima and Racomitrium lanuginosum from these soils usually had low concentrations of potassium and calcium, and high concentrations of sodium, magnesium (and high Mg\\/Ca quotients),

John Henry H. Looney; John Proctor

1989-01-01

209

Structural dynamics of a vegetative soil cover for waste rock dumps  

Microsoft Academic Search

Most waste rock dumps of Uranium mining in the Eastern German Ore Mountains near Schlema site are covered with an 80 cm compacted loam sublayer and a vegetated 20 cm top layer by mixing of compost and mineral soil (vol. 50%\\/vol. 50%). The cover is quite fertile and leads to a considerable reduction of water infiltration into the heaps. However, soil forming

Dirk Knoche

2006-01-01

210

Carbon in the Vegetation and Soils of Great Britain  

Microsoft Academic Search

•The total amount of carbon held by vegetation in Great Britain is estimated to be 114 Mtonnes. •Woodlands and forests hold 80% of the G.B. total although they occupy only about 11% of the rural land area. Broadleaf species hold about 50% of the carbon in woodlands and forests. •A map of carbon in the vegetation of Great Britain at

R. Milne; T. A. Brown

1997-01-01

211

Effect of vegetation on soil moisture sensing observed from orbiting microwave radiometers  

NASA Technical Reports Server (NTRS)

The microwave radiometric measurements made by the Skylab 1.4 GHz radiometer and by the 6.6 GHz and 10.7 GHz channels of the Nimbus-7 Scanning Multichannel Microwave Radiometer were analyzed to study the large-area soil moisture variations of land surfaces. Two regions in Texas, one with sparse and the other with dense vegetation covers, were selected for the study. The results gave a confirmation of the vegetation effect observed by ground-level microwave radiometers. Based on the statistics of the satellite data, it was possible to estimate surface soil moisture in about five different levels from dry to wet conditions with a 1.4 GHz radiometer, provided that the biomass of the vegetation cover could be independently measured. At frequencies greater than about 6.6 GHz, the radiometric measurements showed little sensitivity to moisture variation for vegetation-covered soils. The effects of polarization in microwave emission were studied also.

Wang, J. R.

1985-01-01

212

A mathematical model of soil moisture spatial distribution on the hill slopes of the Loess Plateau  

Microsoft Academic Search

Based on important factors that affect soil moisture spatial distribution, such as the slope gradients, land use, vegetation\\u000a cover, and surface water diffusion characteristics together with field measurements of soil moisture data obtained from the\\u000a surface soil under different land use structures, a soil moisture spatial distribution model was established. The diffusion\\u000a degree coefficient of surface water for different vegetations

Bojie Fu; Zhijian Yang; Yanglin Wang; Pingwen Zhang

2001-01-01

213

Effect of vegetation on rock and soil type discrimination  

NASA Technical Reports Server (NTRS)

The effect of naturally occurring vegetation on the spectral reflectance of earth materials in the wavelength region of 0.45 to 2.4 microns is determined by computer averaging of in situ acquired spectral data. The amount and type of vegetation and the spectral reflectance of the ground are considered. Low albedo materials may be altered beyond recognition with only ten per cent green vegetation cover. Dead or dry vegetation does not greatly alter the shape of the spectral reflectance curve and only changes the albedo with minimum wavelength dependency. With increasing amounts of vegetation the Landsat MSS band ratios 4/6, 4/7, 5/6, and 5/7 are significantly decreased whereas MSS ratios 4/5 and 6/7 remain entirely constant.

Siegal, B. S.; Goetz, A. F. H.

1977-01-01

214

[Characteristics of soil nematode communities in coastal wetlands with different vegetation types].  

PubMed

An investigation was conducted on the characteristics of soil nematode communities in different vegetation belts (Spartina alterniflora belt, Sa; Suaeda glauca belt, Sg; bare land, B1; Phragmites australis belt, Pa; and wheat land, Wl) of Yancheng Wetland Reserve, Jiangsu Province of East China. A total of 39 genera and 20 families of soil nematodes were identified, and the individuals of dominant genera and common genera occupied more than 90% of the total. The total number of the nematodes differed remarkably with vegetation belts, ranged from 79 to 449 individuals per 100 grams of dry soil. Wheat land had the highest number of soil nematodes, while bare land had the lowest one. The nematode ecological indices responded differently to the vegetation belts. The Shannon index (H) and evenness index (J) decreased in the order of Pa > Sg > Wl > Sa > Bl, and the dominance index (lambda) was in the order of Bl > Sa > Wl > Sg > Pa, suggesting that the diversity and stability of the nematode community in bare land were lower than those in the other vegetation belts, and the nematode community in the bare land tended to be simplified. The maturity index (MI) was higher in uncultivated vegetation belts than in wheat land, suggesting that the wheat land was disturbed obviously. The nematode community structure differed significantly with vegetation belts, and the main contributing species in different vegetation belts also differed. There existed significant correlations between the soil physical and chemical characteristics and the nematode numbers, trophic groups, and ecological indices. Our results demonstrated that the changes of soil nematode community structure could be used as an indicator well reflecting the diversity of vegetation belt habitat, and an important bio-indicator of coastal wetland ecosystem. PMID:23431791

Liu, Bei-Bei; Ye, Cheng-Long; Yu, Li; Jiao, Jia-Guo; Liu, Man-Qiang; Hu, Feng; Li, Hui-Xin

2012-11-01

215

Fluoride Accumulation in Soil and Vegetation in the Vicinity of Brick Fields  

Microsoft Academic Search

Fluoride in the soil and vegetation in the vicinity of brick field in the suburb of Lucknow, India was estimated. The water\\u000a soluble fluoride (1:1) in the surface soil ranged from 0.59 ppm to 2.74 ppm where as CaCl2 extractable fluoride ranged from 0.69 ppm to 3.18 ppm. The mean total fluoride concentration in surface soil varied from\\u000a 322 ?g g?1 to 456 ?g g?1. The local vegetations

S. K. Jha; A. K. Nayak; Y. K. Sharma; V. K. Mishra; D. K. Sharma

2008-01-01

216

Comparisons among a new soil index and other two- and four-dimensional vegetation indices  

NASA Technical Reports Server (NTRS)

The 2-D difference vegetation index (DVI) and perpendicular vegetation index (PVI), and the 4-D green vegetation index (GVI) are compared in Landsat MSS data from grain sorghum (Sorghum bicolor, L. Moench) fields for the years 1973 to 1977. PVI and DVI were more closely related to LAI than was GVI. A new 2-D soil line index (SLI), the vector distance from the soil line origin to the point of intersection of PVI with the soil line, is defined and compared with the 4-D soil brightness index, SBI. SLI (based on MSS and MSS7) and SL16 (based on MSS5 and MSS6) were smaller in magnitude than SBI but contained similar information about the soil background. These findings indicate that vegetation and soil indices calculated from the single visible and reflective infrared band sensor systems, such as the AVHRR of the TIROS-N polar orbiting series of satellites, will be meaningful for synoptic monitoring of renewable vegetation. Previously announced in STAR as N83-14567

Wiegand, C. L.; Richardson, A. J.

1982-01-01

217

The influence of annual precipitation, topography, and vegetative cover on soil moisture and summer drought in southern California  

Microsoft Academic Search

The influence of annual precipitation and vegetation cover on soil moisture and on the length of the summer drought was estimated quantitatively using 9 years of soil moisture data collected at Echo Valley in southern California. The measurements support the conclusions that in the semi-arid mediterranean climate a soil drought will occur regardless of vegetation cover and annual precipitation, but

P. C. Miller; D. K. Poole

1983-01-01

218

Characterising Vegetation Canopies by means of optical data and Microwave Scattering models  

NASA Astrophysics Data System (ADS)

One of the main strengths of active microwave remote sensing, in relation to frequency, is its capacity to penetrate vegetation canopies, and reach the ground surface, so that information about the vegetation and hydrological properties of the surface can be drawn. All this infor-mation is gathered in the so called backscattering coefficient (? 0 ), and in a vegetated medium, this coefficient reveals important information on the vegetation water content, geometry and/or structure of the canopy elements, above ground biomass, and soil roughness and moisture. In the scope of microwave frequencies, modeling the backscattering coefficient of vegetated terrain, involves taking into account scattering models that simulate the soil surface contribution by means of its physical variables, and the vegetation layer, through the knowledge of its biophys-ical properties. Soil surface scattering models require describing parameters of roughness, like soil profile height displacement standard deviation and correlation length, and moisture, which determines sur-face reflective properties. The knowledge of these parameters, allows to establishing surface scattering models with different validity ranges. Some frequently used models are divided into theoretical and empirical models. The vegetation canopy is usually regarded as a homogeneous, or random layer, at a certain height above terrain surface, and it is used to compute the attenuation through this layer. This requires a geometric generalization of the vegetation layer and its constituents, specifying additionally its electromagnetic properties. The main simulation models are based on Radiative Transfer theory, which allows for different approaches and simplifications. In this sense, somo of these models, can be efficiently adapted to any vegetated medium, and the constituents can by approximated by more general variables like Leaf Area Index (LAI), or Water total Content (WTC) of Vegetation. Moreover, in the microwave region, it is also possible to relate radar measurements to the above ground biomass. Several studies have shown that the assessment of this variable is also closely related to the operating radar system frequency. In turn, the already mentioned LAI, can be estimated from indirect methods based on Gap Fraction mathematical theory. For measuring this biophysical variable, and some other associated variables, there are a certain number of recently developed instruments, like digital hemispherical photography, which is a very promising technology, due to its suitability and quality of the derived results. These studies have provided a basis to set up a methodology to model the backscattering coef-ficient of vegetation canopies. In this work, it is investigated, which kind of physical variables can be derived by optical sensors and integrated or assimilated by these scattering models. For this particular purpose, soil roughness and moisture filed measurements have been used to sim-ulate the soil surface effect of the canopy. Additionally, by means of hemispherical photographs of the vegetation cover and gap fraction procedures, biophysical variables, like effective and true Leaf Area Indices have been estimated for the same locations of the previous variables. In order to characterize the vegetation canopy, first, a biomass scattering model has been assessed. This model is independent of surface parameters, however it takes into account all polarimetric states of the backscattering coefficient. As second approximation, two models based on Ra-diative Transfer theory have been applied and analyzed. For this purpose, a generalized two layer geometry made up of homogeneous layers of soil and vegetation has been considered for the canopy. All these simulations have been assessed with radar measurements acquired by the full polarimetric radar system on board RADARSAT 2 satellite. All data values, were properly calibrated in order to derive the corresponding polarimetric backscattering coefficients. Keywords: active remote sensing, polarimetric radar, synthetic aperture radar,

Molina, Iñigo; Gonzalez, Constancio; Ormeño, Santiago; Morillo, Carmen; Garcia-Melendez, Eduardo

219

Soil moisture inferences from thermal infrared measurements of vegetation temperatures  

NASA Technical Reports Server (NTRS)

Thermal infrared measurements of wheat (Triticum durum) canopy temperatures were used in a crop water stress index to infer root zone soil moisture. Results indicated that one time plant temperature measurement cannot produce precise estimates of root zone soil moisture due to complicating plant factors. Plant temperature measurements do yield useful qualitative information concerning soil moisture and plant condition.

Jackson, R. D. (principal investigator)

1981-01-01

220

The Interrelationship Between The Spatial Distribution Of Microorganisms And Vegetation In Forest Soils  

Microsoft Academic Search

Recent advances in techniques for investigating soil organisms and evaluating spatial structure have improved our understanding\\u000a of the spatial dynamics of the soil microbial community. Identifying the scale at which microbial community function and interact\\u000a in forest soils is essential to designing sampling schemes that will allow us to adequately evaluate the complex relationships\\u000a between the microbial community and vegetation.

Sherry J. Morris; William J. Dress

221

Soil and vegetation carbon pools in a mountainous watershed of Nepal  

Microsoft Academic Search

Assessment of carbon stocks in vegetation and soil is a basic step in evaluating the carbon sequestration potential of an\\u000a ecosystem. We collected soil (core and composite) samples from 0–10, 10–20, 20–40, and 40–70 cm depths, or down to the bed\\u000a rock, in the soil profile of four types of forest (managed dense Shorea (DS), degraded forest (DF), pine mixed (PS),

Bharat Man Shrestha; Bal Ram Singh

2008-01-01

222

Effect of Vegetation Patterns on SAR derived Surface Soil Moisture Distribution  

NASA Astrophysics Data System (ADS)

Soil moisture can be regarded as one of the important life sustaining entities on our planet. Among its various functions, the first is probably to enable the growth of vegetation on the land surface. Apart from this, water stored in soils plays many other important roles in the global water (and energy) cycle. In the past decades, radar imaging has proven its potential to quantitatively estimate the near surface water content of soils at high spatial resolutions. The use of active microwave data to measure surface soil moisture requires the consideration of several factors like e.g. soil texture, surface roughness, and vegetation. Among these factors, the presence of a vegetation cover is perhaps the major impediment to accurate quantitative retrievals of soil moisture. On the one hand, the vegetation has a disturbing effect on the radar reflectivity and thus causes errors in the soil moisture retrieval which is generally based on theoretical or experimental relationships between the dielectric properties of the soil surface and the radar backscattering coefficient. On the other hand, the spatial distribution of vegetation with e.g. different crop types with different transpiration coefficients and different phenological development, etc, can cause large variations in the plant water consumption and thus has a significant impact on the soil moisture patterns. We have developed methods to estimate the amount of biomass for different crop types and the underlying surface soil water content directly from polarimetric L-band SAR images. While the horizontally-transmit horizontally-receive co-polarization (hh) is most sensitive towards the dielectric soil properties, the horizontally-transmit vertically-receive cross-polarization (hv) is much more sensitive towards the backscattering from the vegetation canopy. In addition the polarimetric observables entropy (H), alpha angle (?), and the total reflected power (span), all of which are highly affected by the canopy conditions, are used to derive biomass information independently from the soil moisture retrieval. Nevertheless, the canopy still has an attenuation effect on the co-polarized backscattering, but this can be corrected by using the vegetation information obtained from the other SAR observables. For constant permittivity states of the soil surface the canopy can have a disturbing effect of up to 6dB. This is the same order of magnitude of dynamic range as observed for soil moisture values ranging from 10 - 40 Vol.-% over bare surfaces. The present study is focused on the Rur catchment (Germany) where the effect of different vegetation patterns on the spatial distribution of near-surface soil water content is investigated by comparison between ALOS PALSAR derived biomass and soil moisture maps. The findings show that the impact of vegetation on the near-surface moisture contents may vary considerably. For wet and intermediate soil conditions where enough water is available for transpiration it was observed that the near-surface moisture content tends to be higher on vegetated fields. This may be explained by the fact that the canopy hampers evaporations due to lack of air movement while the plants uptake water from deeper soil layers. However if the water supply is low the plant water consumption can also lead to accelerated drying of the soil surface. This was especially observed for cereal crops.

Koyama, C. N.; Schneider, K.

2012-12-01

223

Vegetation and soil water interactions on a tailings sand storage facility in the athabasca oil sands region of Alberta Canada  

Microsoft Academic Search

The relationship between vegetation and soil water was studied on the Syncrude South West Sand Storage facility in the Athabasca Oil Sands region of Alberta, Canada. Soil water and relevant soil chemical and physical properties were measured at the soil surface, as well as above and below the reclamation soil and tailings sand interface, in areas of low and high

M. A. Naeth; D. S. Chanasyk; T. D. Burgers

2011-01-01

224

A Broad Approach to Abrupt Boundaries: Looking Beyond the Boundary at Soil Attributes within and Across Tropical Vegetation Types  

PubMed Central

Most research on boundaries between vegetation types emphasizes the contrasts and similarities between conditions on either side of a boundary, but does not compare boundary to non-boundary vegetation. That is, most previous studies lack suitable controls, and may therefore overlook underlying aspects of landscape variability at a regional scale and underestimate the effects that the vegetation itself has on the soil. We compared 25 soil chemistry variables in rainforest, sclerophyll vegetation and across rainforest-sclerophyll boundaries in north-eastern Queensland, Australia. Like previous studies, we did find some contrasts in soil chemistry across vegetation boundaries. However we did not find greater variation in chemical parameters across boundary transects than in transects set in either rainforest or woodland. We also found that soil on both sides of the boundary is more similar to “rainforest soil” than to “woodland soil”. Transects in wet sclerophyll forests with increasing degrees of rainforest invasion showed that as rainforest invades wet sclerophyll forest, the soil beneath wet sclerophyll forest becomes increasingly similar to rainforest soil. Our results have implications for understanding regional vegetation dynamics. Considering soil-vegetation feedbacks and the differences between soil at boundaries and in non-boundary sites may hold clues to some of the processes that occur across and between vegetation types in a wide range of ecosystems. Finally, we suggest that including appropriate controls should become standard practice for studies of vegetation boundaries and edge effects worldwide. PMID:23593312

Warman, Laura; Bradford, Matt G.; Moles, Angela T.

2013-01-01

225

The influence of vegetation on the distribution of soil properties in a semiarid floodplain  

NASA Astrophysics Data System (ADS)

Floodplains rely on specific inundation patterns to maintain soil fertility and vegetation stability. Concerns have been raised that a shift in these patterns has had a negative impact on the health of floodplain ecological communities; especially in semi-arid areas where water is limited. Soil analyses on the semi-arid Lowbidgee floodplain in south-western New South Wales, Australia, were conducted to determine relationships between flood inundation frequency and the soil properties of the floodplain and adjacent hillslope, and to investigate the applicability of the resource islands concept for this environment. Soils were sampled from zones representing four flood inundation frequency categories: high (return interval every year), intermediate (return interval every five years), low (return interval every ten years) and never flooded (hillslopes). Initially, differences between soil properties in the floodplain and the hillslope were evident when vegetated and non-vegetated soils were compared. Within floodplain soils, the electrical conductivity, pH, organic content and concentrations of eight soil geochemicals were higher for vegetated soils than non-vegetated soils, suggesting the resource island concept might apply in this environment. This is somewhat counterintuitive in that floodplains are ordinarily viewed as locations of nutrient enrichment where flood events replenish and redistribute nutrients across floodplain surfaces. Although increasing evidence has been presented to suggest that this replenishment is non-uniform along topographic gradients, this work provides some of the first evidence to suggest that vegetation may also play an important role in the distribution of nutrients and other elements in floodplains. It should be noted, however, that floodplain regions were always nutrient enriched relative to surrounding hillslope areas which suggests that the entire floodplain area (even those areas between existing vegetation patches where nutrient levels are comparatively low) has the potential to support vegetative growth when water becomes available. Comparative results for hillslope soils only identified electrical conductivity, organic content and the concentration of Na to statistically vary between vegetated and non-vegetated soils. Thus, resource islands appear to occur on the floodplain but are not evident on the adjacent flat hillslopes. This result may be a consequence of the relatively flat (slopes of approximately 0.2%) hillslopes that do not have sufficient gradient to generate erosive overland flows and, therefore, have their elements remaining immobile within the soil. Although hillslope regions were generally nutrient poor and chemically depleted relative to adjacent floodplains, the lack of any specific concentration of nutrients under vegetation implies that these hillslopes are open to colonization by vegetation when seeds are present in the soil and sufficient water is available to stimulate growth. This is a situation that is unlikely to occur on slopes where resource islands are present as the intershrub regions tend to be nutrient poor and hostile to vegetation growth.

Neave, Melissa; Rayburg, Scott; Thompson-Laing, Justin

2010-05-01

226

Integrated field lysimetry and porewater sampling for evaluation of chemical mobility in soils and established vegetation.  

PubMed

Potentially toxic chemicals are routinely applied to land to meet growing demands on waste management and food production, but the fate of these chemicals is often not well understood. Here we demonstrate an integrated field lysimetry and porewater sampling method for evaluating the mobility of chemicals applied to soils and established vegetation. Lysimeters, open columns made of metal or plastic, are driven into bareground or vegetated soils. Porewater samplers, which are commercially available and use vacuum to collect percolating soil water, are installed at predetermined depths within the lysimeters. At prearranged times following chemical application to experimental plots, porewater is collected, and lysimeters, containing soil and vegetation, are exhumed. By analyzing chemical concentrations in the lysimeter soil, vegetation, and porewater, downward leaching rates, soil retention capacities, and plant uptake for the chemical of interest may be quantified. Because field lysimetry and porewater sampling are conducted under natural environmental conditions and with minimal soil disturbance, derived results project real-case scenarios and provide valuable information for chemical management. As chemicals are increasingly applied to land worldwide, the described techniques may be utilized to determine whether applied chemicals pose adverse effects to human health or the environment. PMID:25045915

Matteson, Audrey R; Mahoney, Denis J; Gannon, Travis W; Polizzotto, Matthew L

2014-01-01

227

Effects of detailed soil spatial information on watershed modeling across different model scales  

Microsoft Academic Search

Hydro-ecological modelers often use spatial variation of soil information derived from conventional soil surveys in simulation of hydro-ecological processes over watersheds at mesoscale (10 100 km2). Conventional soil surveys are not designed to provide the same level of spatial detail as terrain and vegetation inputs derived from digital terrain analysis and remote sensing techniques. Soil property layers derived from conventional

Trevor Quinn; A.-Xing Zhu; James E. Burt

2005-01-01

228

A Conterminous United States Multilayer Soil Characteristics Dataset for Regional Climate and Hydrology Modeling  

Microsoft Academic Search

Soil information is now widely required by many climate and hydrology models and soil-vegetation-atmosphere transfer schemes. This pa- per describes the development of a multilayer soil characteristics dataset for the conterminous United States (CONUS-SOIL) that specifically addresses the need for soil physical and hydraulic property information over large areas. The State Soil Geographic Database (STATSGO) developed by the U.S. De-

Douglas A. Miller; Richard A. White

1998-01-01

229

Effect of long term organic amendments and vegetation of vineyard soils on the microscale distribution and biogeochemistry of copper.  

PubMed

In this study we evaluated the effect of the long term organic management of a vineyard-soil on the biogeochemistry of copper at the micro-aggregate scale. The model vineyard-soil (Mâcon-France) experienced a long-term field-experiment that consisted in amendments and vegetations with various materials and plants. We studied specifically the effect of Straw (S) and Conifer Compost (CC) organic amendments and Clover (Cl) and Fescue (F) vegetation on the fate of copper (fungicide) in the surface layer of this loamy soil, through a comparison with the Non Amended soil (NA). After collection the five soils were immediately physically fractionated in order to obtain 5 granulometric size-fractions. All soils and size-fractions were quantitatively characterized in terms of granulometry, chemical content and copper distribution, speciation and bioavailability to bacteria and plants. The results showed strong increases of soil-constituents aggregation for all treatments (Cl>CC>S>F>NA), in relation with the increased cementation of soil-constituents by organic matter (OM). The distribution patterns of all major elements and organic carbon were found highly variable within the soil sub-fractions and also between the 5 treatments. Due to their specific inorganic and organic composition, soil sub-fractions can thus be considered as a specific microbial habitat. Added OM accumulated preferentially in the 20-2 ?m and in the >250 ?m of the 5 soils. The distribution patterns of copper as well as its speciation and bioavailability to bacteria in the soil sub-fractions were shown to be strongly different among the five soils, in relation with OM distribution. Our results also suggest that Cu-bioavailability to plants is controlled by soil-rhizosphere structure. Altogether our results permitted to show that long-term organic management of a vineyard soil induced stable modifications of soil physical and chemical properties at both macro and micro-scales. These modifications affected in turn the micro-scale biogeochemistry of copper, and especially its bioavailability to bacteria and plants. PMID:23959219

Navel, Aline; Martins, Jean M F

2014-01-01

230

[Study on nutrient and salinity in soil covered with different vegetations in Shuangtaizi estuarine wetlands].  

PubMed

Nutrient elements and salinity in soil covered by different vegetations including Phragmites australis (Clay.) Trin., Typha orientalis Presl., Puccinellia distans Parl, and Suaeda salsa in Shuangtaizi estuarine wetlands were investigated to study their distribution characteristics and to reveal the nutrient element variation during the vegetation succession processes. Results indicated that total potassium, total phosphorus and salinity were different significantly in soil between different plant communities while available phosphorus, total nitrogen, available nitrogen, available potassium, total sulfur, iron and soil organic carbon were different insignificantly. Correlation analysis suggested that soil organic carbon were related significantly to total nitrogen, available phosphorus, available potassium, which implied that decomposition of plant litter might be the mail source of soil nitrogen and available nutrient. Salinity was significantly related to total phosphorus and iron in soil. In Shuangtaizi estuarine wetland soil, ratios of carbon to nitrogen (R(C/N)) was in the range of 12.21-26.33 and the average value was 18.21, which was higher than 12.0. It indicated that soil organic carbon in Shuangtaizi estuarine mainly came from land but not ocean and plants contributed the most of soil organic matters. There was no significant difference in R(C/N) between soil from the four plant communities (F = 1.890, p = 0.151). R(C/N) was related significantly to sol salinity (r = 0.346 3, p = 0.035 8) and was increasing with soil salinity. PMID:22165232

Song, Xiao-Lin; Lü, Xian-Guo; Zhang, Zhong-Sheng; Chen, Zhi-Ke; Liu, Zheng-Mao

2011-09-01

231

[Contribution of soil seed bank to the regeneration of damaged vegetation on floodplain].  

PubMed

A field germination experiment of soil seed bank was carried out on two typical floodplains in the lower reaches of Tarim River, and a comparison was made between the soil seed banks and corresponding seedling banks on the two floodplains, aimed to assess the contribution of soil seed bank to the regeneration of damaged vegetation. The results showed that there were 12 plant species in the soil seed banks, and the life forms were mainly perennial herbs and shrubs. The soil seed banks had a density of 282.5 seeds m(-2) and 173.2 seeds x m(-2), and the seeds in top soil (0-2 cm) accounted for 76.9% and 71.0% of the total, respectively. The soil seed banks had significant effects on the seedlings species composition and density, and 84.7% and 99.4% of the seedlings on the two floodplains were emerged from corresponding soil seed banks. The similarity coefficient between soil seed bank and seedling bank of the two floodplains was 0.72 and 0.63, respectively, and there existed significant positive correlation between seedling density and soil seed bank density, illustrating that soil seed bank made important contribution to the natural regeneration of vegetation. PMID:19288712

Wang, Zeng-ru; Xu, Hai-liang; Yin, Lin-ke; Li, Ji-mei; Zhang, Zhan-jiang; Li, Yuan

2008-12-01

232

Ad Hoc Modeling of Root Zone Soil Water with Landsat Imagery and Terrain and Soils Data  

PubMed Central

Agricultural producers require knowledge of soil water at plant rooting depths, while many remote sensing studies have focused on surface soil water or mechanistic models that are not easily parameterized. We developed site-specific empirical models to predict spring soil water content for two Montana ranches. Calibration data sample sizes were based on the estimated variability of soil water and the desired level of precision for the soil water estimates. Models used Landsat imagery, a digital elevation model, and a soil survey as predictor variables. Our objectives were to see whether soil water could be predicted accurately with easily obtainable calibration data and predictor variables and to consider the relative influence of the three sources of predictor variables. Independent validation showed that multiple regression models predicted soil water with average error (RMSD) within 0.04 mass water content. This was similar to the accuracy expected based on a statistical power test based on our sample size (n = 41 and n = 50). Improved prediction precision could be achieved with additional calibration samples, and range managers can readily balance the desired level of precision with the amount of effort to collect calibration data. Spring soil water prediction effectively utilized a combination of land surface imagery, terrain data, and subsurface soil characterization data. Ranchers could use accurate spring soil water content predictions to set stocking rates. Such management can help ensure that water, soil, and vegetation resources are used conservatively in irrigated and non-irrigated rangeland systems.

Sankey, Joel B.; Lawrence, Rick L.; Wraith, Jon M.

2008-01-01

233

Estimating the mechanical effects of riparian vegetation on stream bank stability using a fiber bundle model  

Microsoft Academic Search

Recent research has suggested that the roots of riparian vegetation dramatically increase the geomechanical stability (i.e., factor of safety) of stream banks. Past research has used a perpendicular root reinforcement model that assumes that all of the tensile strength of the roots is mobilized instantaneously at the moment of bank failure. In reality, as a soil-root matrix shears, the roots

Natasha Pollen; Andrew Simon

2005-01-01

234

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

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

235

Spatial and Temporal Variability of Soils as it Relates to Vegetation Zonation in a Tropical Wetland  

NASA Astrophysics Data System (ADS)

Wetland ecosystems provide a range of important ecosystem services, including provisioning, regulating and cultural services. Globally wetlands have come under increasing anthropogenic pressure, and many need to be restored. An important component of this is understanding the relationship between soils and plant zonation in tropical wetlands. The edaphic characteristics of wetland soils typically occur in gradients and have been the focus of intensive research as it relates to vegetation zonation. Because much of this research has been focused in temperate regions relatively little is still known about the importance of edaphic factors mainly salinity to the zonation of vegetation in a tropical wetland. Here, we use a geophysical response surface directed sampling approach to determine important soil properties and controls on vegetation zonation in a tropical wetland. By using geophysical imaging to determine the spatial patterns of salinity, soil physio-chemical properties and to compare plant community patterns within geophysical signals in the Godineau swamp, we were able to determine the major soil factors which influence plant zonation within a tropical wetland. Analysis revealed that salinity is a major soil factor that differentiates plant communities. Grasses thrived at higher elevations which had lower clay and salt levels and sedges dominated under lower elevations with higher clay and salt levels. Keywords: Vegetation pattern, EC, EMI, geophysics

Atwell, M.; Robinson, D. A.; Wuddivira, M. N.; Gobin, J.

2011-12-01

236

[Relationships between typical vegetations, soil salinity, and groundwater depth in the Yellow River Delta of China].  

PubMed

Soil salinity and groundwater depth are the two important factors affecting the vegetation growth and distribution in the Yellow River Delta. Through field investigation and statistical analysis, this paper studied the relationships between the typical vegetations (Suaeda heteroptera-Tamarix chinensis, Robinia pseudoacacia, Phragmites australis, and cotton) , soil salinity, and groundwater depth in the Delta. In the study area, groundwater depth had significant effects on soil salinity, with the average influence coefficient being 0.327. When the groundwater depth was 0.5-1.5 m, soil salinization was most severe. The vegetation growth in the Delta was poorer, with the NDVI in 78% of the total area being less than 0.4. Groundwater depth and soil salinity had significant effects on the vegetation distribution. Soil salinity had significant effects on the NDVI of R. pseudoacacia, S. heteroptera-T. chinensis, P. australis, and cotton, while groundwater depth had significant effects on the NDVI of S. heteroptera - T. chinensis, but lesser effects on the NDVI of P. australis, cotton and R. pseudoacacia. PMID:24417097

Ma, Yu-Lei; Wang, De; Liu, Jun-Min; Wen, Xiao-Hu; Gao, Meng; Shao, Hong-Bo

2013-09-01

237

[Effects of artificial vegetation on the spatial heterogeneity of soil moisture and salt in coastal saline land of Chongming Dongtan, Shanghai].  

PubMed

By the methods of classical statistics and geostatistics, this paper studied the spatial heterogeneity of surface soil (0-20 cm layer) moisture and salt contents under three kinds of artificial vegetation in coastal salt land in Chongming Dongtan of Shanghai. The soil moisture content in different plots was in order of Cynodon dactylon > Taxodium distichum > Nerium indicum, and the coefficient of variation was 13.9%, 13.4% and 12.9%, respectively. The soil electric conductivity was in the order of N. indicum > C. dactylon > T. distichum, and the coefficient of variation was 79.2%, 55.4% and 15. 9%, respectively. Both the soil moisture content and the salt content were in moderate variation. The theoretical models of variogram for the soil moisture and salt contents in different plots varied, among which, the soil electric conductivity fitted better, with R2 between 0.97 and 0.99. When the artificial vegetation varied from N. indicum to T. distichum and then to C. dactylon, the spatial heterogeneity of soil moisture content changed from weak to strong, in which, the variability was random under N. indicum. When the vegetation varied from C. dactylon to T. distichum and to N. indicum, the spatial heterogeneity of soil electric conductivity changed from moderate to strong. Under different vegetations, the soil electric conductivity was mostly in positive correlation, whereas the soil moisture content was in negative correlation. The spatial pattern of soil moisture and salt contents under T. distichum was in striped distribution, that under C. dactylon was in large plaque and continuous distribution, whereas under N. indicum, the spatial pattern of soil moisture content was in small breaking plaque distribution, and that of soil salt content was in striped distribution. PMID:24380332

He, Bin; Cai, Yong-li; Ran, Wen-rui; Zhao, Xiao-lei

2013-08-01

238

Soil moisture characteristics and implications for vegetation regeneration in Sudan during the period 1965-2005.  

NASA Astrophysics Data System (ADS)

This study aims at better understanding the soil moisture (SM) characteristics as fundamental factors for vegetation regeneration in Sudan during the period 1965-2005. The Mann Kendall (MK) analysis was used to test the trend in the average monthly soil moisture (SM), rainfall and temperature data. Geographically weighted regression (GWR) was selected to study the SM, rainfall and temperature relations because it accounts for the local spatial variability and non-stationarity of these variables. To further understand dry and wet variations in terms of regeneration demand, the aridity index (AI) was used. The results of (MK) test showed that there were decreasing trends of SM on an annual and seasonal level and that the trend was less dramatic or softer in the dry season (November-April) than the wet season (May- October). That soil moisture variability followed closely that of rainfall and temperature, although there was a hint that SM variability followed temperature changes more closely than rainfall. The (GWR) model gave optimal results in semi-arid central Sudan. In the north due to lack of rainfall and in the south due to plant heterogeneity, the model did not perform so well. The spatio-temporal variability of the (AI) showed that the long-term average of (AI) was affected by the reported decline in rainfall during 1965-1985. The decadal (AI) average of 1995-2005 gave evidence of increases in rainfall that are reported since the mid-nineties. (AI) performed well in reflecting the wet conditions in Sudan. Very rare are the studies of soil moisture in Sudan, especially in the through way that is presented here.

El Haj El Tahir, M.; Xu, C.; Zengxin, Z.

2012-04-01

239

The effect of vegetation on soil redox within a seasonally flooded forested system  

Microsoft Academic Search

The effect of rhizosphere oxidation on redox level was investigated between vegetated and denuded plots and betweenAcer rubrum andFraxinus pennsylvanica seedlings within a seasonally flooded forested system in Virginia. Redox potentials were significantly greater (p<0.05) in\\u000a the upper 15 cm of the soils in the vegetated plots. Redox potential within the root mass ofAcer rubrum seedlings did not differ significantly

Kirk J. Havens

1997-01-01

240

The Soil Biota Composition along a Progressive Succession of Secondary Vegetation in a Karst Area  

PubMed Central

Karst ecosystems are fragile and are in many regions degraded by anthropogenic activities. Current management of degraded karst areas focuses on aboveground vegetation succession or recovery and aims at establishing a forest ecosystem. Whether progressive succession of vegetation in karst areas is accompanied by establishment of soil biota is poorly understood. In the present study, soil microbial and nematode communities, as well as soil physico-chemical properties were studied along a progressive succession of secondary vegetation (from grassland to shrubland to forest) in a karst area in southwest China. Microbial biomass, nematode density, ratio of fungal to bacterial biomass, nematode structure index, and nematode enrichment index decreased with the secondary succession in the plant community. Overall, the results indicated a pattern of declines in soil biota abundance and food web complexity that was associated with a decrease in soil pH and a decrease in soil organic carbon content with the progressive secondary succession of the plant community. Our findings suggest that soil biota amendment is necessary during karst ecosystem restoration and establishment and management of grasslands may be feasible in karst areas. PMID:25379741

He, Xunyang; Liu, Lu; Wang, Kelin

2014-01-01

241

The Soil Biota Composition along a Progressive Succession of Secondary Vegetation in a Karst Area.  

PubMed

Karst ecosystems are fragile and are in many regions degraded by anthropogenic activities. Current management of degraded karst areas focuses on aboveground vegetation succession or recovery and aims at establishing a forest ecosystem. Whether progressive succession of vegetation in karst areas is accompanied by establishment of soil biota is poorly understood. In the present study, soil microbial and nematode communities, as well as soil physico-chemical properties were studied along a progressive succession of secondary vegetation (from grassland to shrubland to forest) in a karst area in southwest China. Microbial biomass, nematode density, ratio of fungal to bacterial biomass, nematode structure index, and nematode enrichment index decreased with the secondary succession in the plant community. Overall, the results indicated a pattern of declines in soil biota abundance and food web complexity that was associated with a decrease in soil pH and a decrease in soil organic carbon content with the progressive secondary succession of the plant community. Our findings suggest that soil biota amendment is necessary during karst ecosystem restoration and establishment and management of grasslands may be feasible in karst areas. PMID:25379741

Zhao, Jie; Li, Shengping; He, Xunyang; Liu, Lu; Wang, Kelin

2014-01-01

242

Anthropogenic impact on the presence of L. monocytogenes in soil, fruits, and vegetables.  

PubMed

The aim of this study was to determine the prevalence of Listeria sp. and Listeria monocytogenes in soil samples with reference to type of fertilizers (natural and artificial) and distance from places intensively exploited by men, as well as to determine the relationship between the presence of L. monocytogenes in the soil and in fruits and vegetables. The examined 1,000 soil samples originated from 15 different areas, whilst 140 samples of fruits and 210 samples of vegetables were collected from those areas. L. monocytogenes was isolated only from 5.5 % of all soil samples coming exclusively from meadows intensively grazed by cattle (27.8 %) and areas near food processing plants (25 %) and wild animal forests (24 %). Listeria sp. and L. monocytogenes were not present on artificially fertilized areas and wastelands. L. monocytogenes was detected in 10 % of samples of strawberry, 15 % of potato samples, and 5 % of parsley samples. Our data indicate that Listeria spp. and particularly L. monocytogenes were found in the soil from (1) arable lands fertilized with manure, (2) pasture (the land fertilized with feces of domestic animals), and (3) forests (again, the land fertilized with feces of animals, not domestic but wild). The bacteria were not detected in the soil samples collected at (1) artificially fertilized arable lands and (2) wastelands (the lands that were not fertilized with manure or animal feces). Moreover, a correlation was determined in the presence of L. monocytogenes between soil samples and samples of the examined fruits and vegetables. PMID:23775320

Szymczak, Barbara; Szymczak, Mariusz; Sawicki, Wojciech; D?browski, Waldemar

2014-01-01

243

Continuous measurements of net CO2 exchange by vegetation and soils in a suburban landscape  

NASA Astrophysics Data System (ADS)

In a suburban neighborhood of Minneapolis-Saint Paul, Minnesota, USA, we simultaneously measured net CO2 exchange of trees using sap flow and leaf gas exchange measurements, net CO2exchange of a turfgrass lawn using eddy covariance from a portable tower, and total surface-atmosphere CO2 fluxes (FC) using an eddy covariance system on a tall tower. Two years of continuous measurements showed that net CO2exchange varied among vegetation types, with the largest growing-season (Apr-Nov) net CO2 uptake on a per cover area basis from evergreen needleleaf trees (-603 g C m-2), followed by deciduous broadleaf trees (-216 g C m-2), irrigated turfgrass (-211 g C m-2), and non-irrigated turfgrass (-115 g C m-2). Vegetation types showed seasonal patterns of CO2exchange similar to those observed in natural ecosystems. Scaled-up net CO2 exchange from vegetation and soils (FC(VegSoil)) agreed closely with landscape FC measurements from the tall tower at times when fossil fuel emissions were at a minimum. Although FC(VegSoil) did not offset fossil fuel emissions on an annual basis, the temporal pattern of FC(VegSoil) did significantly alter the seasonality of FC. Total growing season FC(VegSoil)in recreational land-use areas averaged -165 g C m-2 and was dominated by turfgrass CO2 exchange (representing 77% of the total), whereas FC(VegSoil) in residential areas averaged -124 g C m-2 and was dominated by trees (representing 78% of the total). Our results suggest urban vegetation types can capture much of the variability required to predict seasonal patterns and differences in FC(VegSoil) that could result from changes in land use or vegetation composition in temperate cities.

Peters, Emily B.; McFadden, Joseph P.

2012-09-01

244

Models of soil moisture dynamics in ecohydrology: A comparative study  

NASA Astrophysics Data System (ADS)

An accurate description of plant ecology requires an understanding of the interplay between precipitation, infiltration, and evapotranspiration. A simple model for soil moisture dynamics, which does not resolve spatial variations in saturation, facilitates analytical expressions of soil and plant behavior as functions of climate, soil, and vegetation characteristics. Proper application of such a model requires knowledge of the conditions under which the underlying simplifications are appropriate. To address this issue, we compare predictions of evapotranspiration and root zone saturation over a growing season from a simple bucket-filling model to those from a more complex, vertically resolved model. Dimensionless groups of key parameters measure the quality of the match between the models. For a climate, soil, and woody plant characteristic of an African savanna the predictions of the two models are quite similar if the plant can extract water from locally wet regions to make up for roots in dry portions of the soil column; if not, the match is poor.

Guswa, Andrew J.; Celia, M. A.; Rodriguez-Iturbe, I.

2002-09-01

245

Evaluation of Thematic Mapper for detecting soil properties under grassland vegetation  

NASA Technical Reports Server (NTRS)

Analysis of Thematic Mapper data acquired November 15, 1982, over a vegetated site located in the East Texas Timberlands and Claypan area of Texas has indicated that montmorillonitic clay textured soils can be separated from soils with different textures. The difference of TM band 4 (0.76-0.90 micron) and band 7 (2.08-2.35 microns) had an agreement of 55.8 percent with the USDA soil survey for upland clay soils. This compared to 55.9-percent agreement when all six bands (excluding the thermal) were used. The disagreement occurred at the boundary lines as defined by the USDA soil survey and the spectral data. This result is considered to be fairly good, considering the difficulty in placement of soil boundaries by the soil scientist in the field. While the exact influence on the vegetation, and thus the spectral response observed by TM, is not understood at this time, it appears that TM band 7 is responding to the type of mineralogy of the soil and that soil properties important to the plant can be detected using TM.

Thompson, D. R.; Henderson, K. E.

1984-01-01

246

Investigation of Soil Moisture - Vegetation Interactions in Oklahoma  

E-print Network

magnitude and variability (Mahmood and Hubbard, 2003; Vicente-Serrano, 2007; DeLiberty and Legates, 2008). In fact, Mahmood and Hubbard (2003) found that under certain precipitation conditions, land use land cover is the most influential factor for soil... magnitude and variability (Mahmood and Hubbard, 2003; Vicente-Serrano, 2007; DeLiberty and Legates, 2008). In fact, Mahmood and Hubbard (2003) found that under certain precipitation conditions, land use land cover is the most influential factor for soil...

Ford, Trenton W.

2013-03-06

247

Estimation of soil moisture using trapezoidal relationship between remotely sensed land surface temperature and vegetation index  

NASA Astrophysics Data System (ADS)

The trapezoidal relationship between land surface temperature (Ts) and Vegetation Index (VI) was used to estimate soil moisture in the present study. An iterative algorithm is proposed to estimate the vertices of the Ts ~ VI trapezoid theoretically for each pixel, and then Water Deficit Index (WDI) is calculated based on the Ts ~ VI trapezoid using MODIS remotely sensed measurements of surface temperature and enhanced vegetation index (EVI). The capability of using WDI based on Ts ~ VI trapezoid to estimate soil moisture is evaluated using soil moisture observations and antecedent precipitation in the Walnut Gulch Experimental Watershed (WGEW) in Arizona, USA. The result shows that, the Ts ~ VI trapezoid based WDI can capture temporal variation in surface soil moisture well, but the capability of detecting spatial variation is poor for such a semi-arid region as WGEW.

Wang, W.; Huang, D.; Wang, X.-G.; Liu, Y.-R.; Zhou, F.

2011-05-01

248

Infrared temperature measurements over bare soil and vegetation - A HAPEX perspective  

NASA Technical Reports Server (NTRS)

Preliminary analyses of aircraft and ground measurements made in France during the HAPEX experiment show that horizontal radiometric surface temperature variations, as viewed by aircraft, can reflect the vertical profile of soil moisture (soil versus root zone) because of horizontal variations in vegetation density. Analyses based on one day's data show that, although horizontal variations in soil moisture were small, the vertical differences between a dry surface and a wet root zone were large. Horizontal temperature differences between bare soil, corn and oats reflect differences in the fractional vegetation cover, as seen by the radiometer. On the other hand, these horizontal variations in radiometric surface temperature seem to reflect real horizontal variations in surface turbulent energy fluxes.

Carlson, Toby N.; Perry, Eileen M.; Taconet, Odile

1987-01-01

249

Effect of vegetation and land use on soil fertility in Wutai Mountains of Shanxi Province  

Microsoft Academic Search

By comparison of several kinds stands, effect of vegetation and land use on the surface soil was investigated in Wutal Mountains\\u000a of Shanxi Province. The result shows that larch (Larix principis-rupprechtii) and birch stands (Betula platyphylla) have more favourable influence on the properties of surface soil than pine (Pinus tabulaeformis) plantation and mixed plantation of pine and poplar (Populus cathayana).

Zhang Xiaoquan; Song Chaoshu; Zhang Qinghua

1998-01-01

250

Field measurement of soil water repellency and its impact on water flow under different vegetation  

Microsoft Academic Search

Numerous recent laboratory studies have shown that vegetation can influence soil water flow by inducing very low levels of\\u000a water repellency. In this study we extended on this previous research by developing a field-based test using a miniature infiltrometer\\u000a to assess low levels of water repellency from physically based measurements of liquid flow in soil. The field-based test was\\u000a verified

L’ubomír Lichner; Paul D. Hallett; Debbie S. Feeney; Olívia ?ugová; Miroslav Tesa?

2007-01-01

251

The impact of using area-averaged land surface properties —topography, vegetation condition, soil wetness—in calculations of intermediate scale (approximately 10 km 2) surface-atmosphere heat and moisture fluxes  

Microsoft Academic Search

It is commonly assumed that biophysically based soil-vegetation-atmosphere transfer (SVAT) models are scale-invariant with respect to the initial boundary conditions of topography, vegetation condition and soil moisture. In practice, SVAT models that have been developed and tested at the local scale (a few meters or a few tens of meters) are applied almost unmodified within general circulation models (GCMs) of

Piers J. Sellers; Mark D. Heiser; Forrest G. Hall; Shashi B. Verma; Raymond L. Desjardins; Peter M. Schuepp; J. Ian MacPherson

1997-01-01

252

Spatial variability of soil and vegetation characteristics in an urban park in Tel-Aviv  

NASA Astrophysics Data System (ADS)

Mosaic-like spatial patterns, consisting of divers soil microenvironments, characterize the landscapes of many urban parks. These microenvironments may differ in their pedological, hydrological and floral characteristics, and they play important roles in urban ecogeomorphic system functioning. In and around a park covering 50 ha in Tel Aviv, Israel, soil properties and herbaceous vegetation were measured in eight types of microenvironments. Six microenvironments were within the park: area under Ceratonia siliqua (Cs-U), area under Ficus sycomorus (Fi-U), a rest area under F. sycomorus (Re-U), an open area with bare soil (Oa-S), an open area with biological crusts (Oa-C), and an open area with herbaceous vegetation (Oa-V). Outside the park were two control microenvironments, located, respectively, on a flat area (Co-P) and an inclined open area (Co-S). The soil was sampled from two depths (0-2 and 5-10 cm), during the peak of the growing season (March). For each soil sample, moisture content, organic matter content, CaCO3 content, texture, pH, electrical conductivity, and soluble ions contents were determined in 1:1 water extraction. In addition, prior to the soil sampling, vegetation cover, number of species, and species diversity of herbaceous vegetation were measured. The barbecue fires and visitors in each of the microenvironments were counted. Whereas the soil organic matter and vegetation in Fi-U differed from those in the control(Co-P, Co-S), those in Oa-V were similar to those in the control. Fi-U was characterized by higher values of soil moisture, organic matter, penetration depth, and vegetation cover than Cs-U. Open microenvironments within the park (Oa-S, Oa-C, Oa-V) showed lower values of soil penetration than the control microenvironments. In Oa-V unique types of plants such as Capsella bursa-pastoris and Anagallis arvensis, which did not appear in the control microenvironments, were found. This was true also for Fi-U, in which species like Oxalis pes-caprae were found. Significant differences in soil and vegetation properties were found between Re-U and the rest of microenvironments. Differences in levels of human activities, in addition to differences in vegetation types, increased the spatial heterogeneity of soil properties. The rest microenvironment (Re-U) exhibited degraded soil conditions and can be regarded as forming the fragile areas of the park. An urban park offers potential for presence and growth of natural vegetation and, therefore, also for preservation of biodiversity. Natural vegetation, in its role as a part of the urban park, enriches the landscape diversity and thereby may contribute to the enjoyment of the visitors in the park.

Sarah, Pariente; Zhevelev, Helena M.; Oz, Atar

2010-05-01

253

Soil, water, and vegetation conditions in South Texas  

NASA Technical Reports Server (NTRS)

The author has identified the following significant results. Reflectance measurements with a field spectroradiometer on nine dates (between December 9 and April 8) during the growing season of two wheat varieties, Milam and Penjamo, showed that the reflectance curves had the characteristic shape of vegetated surfaces by 4 weeks after the emergence. Green light (0.55 micron) reflectance was maximal and between water absorption bands (1.65 and 2.2 microns) reflectance was minimal when green vegetation development was greatest. Computer classification was accomplished for 81,000 hectare coastal rangeland area for October 13 and December 10, 1975, overpass dates. A hard freeze occurred between these two dates and many of the deciduous woody species defoliated so that more light penetrated to the herbaceous understory in December than in October.

Wiegand, C. L.; Gausman, H. W.; Leamer, R. W.; Richardson, A. J.; Everitt, J. H.; Gerbermann, A. H. (principal investigators)

1976-01-01

254

Chemical-specific representation of air--soil exchange and soil penetration in regional multimedia models.  

PubMed

In multimedia mass-balance models, the soil compartment is an important sink as well as a conduit for transfers to vegetation and shallow groundwater. Here a novel approach for constructing soil transport algorithms for multimedia fate models is developed and evaluated. The resulting algorithms account for diffusion in gas and liquid components; advection in gas, liquid, or solid phases; and multiple transformation processes. They also provide an explicit quantification of the characteristic soil penetration depth. We construct a compartment model using three and four soil layers to replicate with high reliability the flux and mass distribution obtained from the exact analytical solution describing the transient dispersion, advection, and transformation of chemicals in soil layers with different properties but a fixed boundary condition at the air-soil surface. The soil compartment algorithms can be dynamically linked to other compartments (air, vegetation, groundwater, surface water) in multimedia fate models. We demonstrate and evaluate the performance of the algorithms in a model with applications to benzene, benzo[a]pyrene, MTBE, TCDD, and tritium. PMID:12901660

McKone, T E; Bennett, D H

2003-07-15

255

Comparison of organochlorine pesticides and polychlorinated biphenyls residues in vegetables, grain and soil from organic and conventional farming in Poland  

Microsoft Academic Search

Organic and conventional crops were studied by identifying the relationship between persistent organic pollutants in cereals, vegetables and soil. The residues of organochlorine pesticides and polychlorinated biphenyls (PCBs) were determined in grains (rye and wheat), vegetables (carrots and beets) and soil collected from the fields. PCB residues recorded in the beets from organic farming were as high as 3.71 ppb

Agata Witczak; Hassan Abdel-Gawad

2012-01-01

256

Effects of vegetation on radon transport processes in soil  

SciTech Connect

Radon concentrations in soil gas were measured on a weekly schedule. Samples were extracted through the tubes used for measuring pressure differentials at depths of 30, 100, 180 cm. From November to March, the concentrations increase with depth and are for the most part constant over time. The situation is similar from May through August. There is a pronounced increase in the soil radon concentration in early March. This is followed by a decrease to pre March levels at 30 cm. However, at 100 and 180 cm the radon concentrations remain elevated. Attempts were made to explain this data. The average soil moisture content measured with the neutron gauge are shown in Figure 2. Also shown is a history of precipitation events. The period from November to March was relatively dry. On March 6 there was a heavy rain deposited 3 cm of water. This was followed by a snow storm that contained over 5 cm of moisture. Precipitation events during the summer months did not seem to have a large effect on the moisture profile because these rainfall events are typical of short duration with a large amount of runoff. Other soil parameters and meteorological data were analyzed in order to determine their influence on soil radon concentrations.

Borak, T.B.

1991-02-01

257

Transfer of radioactive caesium from soil to vegetation and comparison with potassium in upland grasslands.  

PubMed

The distribution and transfer of caesium and potassium between soils and vegetation has been investigated by field sampling and experimental studies on soils and vegetation typical of upland grassland in north west England. Total (137)Cs content to a depth of 0.05 m below root matt ranged from 13 000 to 18 000 Bq m(-2). This caesium content derives from three sources: the Windscale accident of 1957, weapons-testing fallout which peaked in the early 1960s, and the Chernobyl accident in May 1986. From 2200 to 6200 Bq m(-2) is attributed to the first two sources, and the remainder to Chernobyl. In December 1986, 23-78% of pre-Chernobyl (137)Cs was associated with soil underlying root matt and 0.5-5.5% was associated with vegetation. Plant/soil concentration ratios for pre-Chernobyl (137)Cs were in the range 0.5-6.5, the lowest values being associated with patches of Festuca/Agrostis turf. At the same time, 4-19% of (137)Cs deposited from Chernobyl was associated with vegetation, although higher values appeared in conjunction with the moss, Polytrichum commune. Corresponding total potassium contents were in the range 9.6-22 mg m(-2) to 0.05 m soil depth. Lower values were found at the wetter sites where, on average, 5.7% of the total potassium was present in vegetation. At drier sites the potassium content was higher and, on average, 8.9% was present in vegetation. Plant/soil concentration ratios ranged from 2.2 to 9.2. During accelerated growth of vegetation, on monoliths in glasshouse conditions over the winter of 1986/87, (137)Cs was transferred from soil and root matt to new growth, such that concentrations in fresh growth were similar to or higher than those observed in the field during December 1986. Removal of caesium by successive cuts resulted in up to 25% of the original estimated total being removed over a 240 day period. Increased concentrations coincided with the emergence of Carex sp. and Trichophorum caespitosum, as well as the development of Agrostis sp. and Festuca ovina. Observed Cs/K discrimination ratios, particularly for (137)Cs deposited from Chernobyl, were higher than previously reported in the literature. The experimental results were confirmed by field observations during spring 1987 and it is concluded that caesium deposited as a result of the Chernobyl accident will continue to be recycled in organic and low potassium soils. PMID:15092335

Coughtrey, P J; Kirton, J A; Mitchell, N G; Morris, C

1989-01-01

258

Vegetation Succession & Geomorphic Channel Evolution Model  

E-print Network

floodplain development and bank stabilizing vegetation (OBL and FACW) ­ CP b: C type channel that exhibits) What do you think is the elevation difference between the two landforms? Channel trend? #12;State = widened Banks inclined Floodplain developing Vegetation = scirpus (OBL) Willow (FACW), cottonwood (FACW

259

Genetic algorithm applied to a Soil-Vegetation-Atmosphere system: Sensitivity and uncertainty analysis  

NASA Astrophysics Data System (ADS)

Numerical models are of precious help for predicting water fluxes in the vadose zone and more specifically in Soil-Vegetation-Atmosphere (SVA) systems. For such simulations, robust models and representative soil hydraulic parameters are required. Calibration of unsaturated hydraulic properties is known to be a difficult optimization problem due to the high non-linearity of the water flow equations. Therefore, robust methods are needed to avoid the optimization process to lead to non-optimal parameters. Evolutionary algorithms and specifically genetic algorithms (GAs) are very well suited for those complex parameter optimization problems. Additionally, GAs offer the opportunity to assess the confidence in the hydraulic parameter estimations, because of the large number of model realizations. The SVA system in this study concerns a pine stand on a heterogeneous sandy soil (podzol) in the Campine region in the north of Belgium. Throughfall and other meteorological data and water contents at different soil depths have been recorded during one year at a daily time step in two lysimeters. The water table level, which is varying between 95 and 170 cm, has been recorded with intervals of 0.5 hour. The leaf area index was measured as well at some selected time moments during the year in order to evaluate the energy which reaches the soil and to deduce the potential evaporation. Water contents at several depths have been recorded. Based on the profile description, five soil layers have been distinguished in the podzol. Two models have been used for simulating water fluxes: (i) a mechanistic model, the HYDRUS-1D model, which solves the Richards' equation, and (ii) a compartmental model, which treats the soil profile as a bucket into which water flows until its maximum capacity is reached. A global sensitivity analysis (Morris' one-at-a-time sensitivity analysis) was run previously to the calibration, in order to check the sensitivity in the chosen parameter search space. For the inversion procedure a genetical algorithm (GA) was used. Specific features such as elitism, roulette-wheel process for selection operator and island theory were implemented. Optimization was based on the water content measurements recorded at several depths. Ten scenarios have been elaborated and applied on the two lysimeters in order to investigate the impact of the conceptual model in terms of processes description (mechanistic or compartmental) and geometry (number of horizons in the profile description) on the calibration accuracy. Calibration leads to a good agreement with the measured water contents. The most critical parameters for improving the goodness of fit are the number of horizons and the type of process description. Best fit are found for a mechanistic model with 5 horizons resulting in absolute differences between observed and simulated water contents less than 0.02 cm3cm-3 in average. Parameter estimate analysis shows that layers thicknesses are poorly constrained whereas hydraulic parameters are much well defined.

Schneider, Sébastien; Jacques, Diederik; Mallants, Dirk

2010-05-01

260

Estimating models of vegetation fractional coverage based on remote sensing images at different radiometric correction levels  

Microsoft Academic Search

The images of post atmospheric correction reflectance (PAC), top of atmosphere reflectance (TOA), and digital number (DN)\\u000a of a SPOT5 HRG remote sensing image of Nanjing, China were used to derive four vegetation indices (VIs), that is, normalized\\u000a difference vegetation index (NDVI), transformed vegetation index (TVI), soil-adjusted vegetation index (SAVI), and modified\\u000a soil-adjusted vegetation index (MSAVI). Based on these VIs

Zhujun Gu; Zhiyuan Zeng; Xuezheng Shi; Dongsheng Yu; Wei Zheng; Zhenlong Zhang; Zifu Hu

2009-01-01

261

Distribution of vegetation in wind-dominated landscapes: Implications for wind erosion modeling and landscape processes  

NASA Astrophysics Data System (ADS)

Dust emission and wind erosion from arid and semiarid environments provide a major source of global atmospheric aerosols. Well-known relations between wind stress and saltation sand flux for sand sheets and relations between sand flux and dust emission by sandblasting have enabled construction of dust models that have only been partly successful in predicting atmospheric mineral dust concentrations. Most models of wind erosion assume that vegetation is evenly distributed. Through the use of field, Fourier transform, and semivariogram analysis, we show that mesquite dunelands in the Chihuahuan Desert of southern New Mexico, United States, have anisotropic shrub distributions. Elongated areas of bare soil, "streets," which are aligned with the prevailing winds may partially explain discrepancies between observed and predicted atmospheric dust concentrations. Soils in the streets are not protected from winds blowing down the streets and may therefore produce more dust than if vegetation were more evenly distributed. Currently, few desert landscape evolution models take the role of wind explicitly into account. The existence of streets implies that wind plays a major role in the evolution of vegetated arid and semiarid landscapes with wind-erodible soils. Here wind acts in tandem with water to enforce islands of fertility centered around individual shrubs and may provide an explanation for reduced soil fertility observed in shrublands. Furthermore, in order for mathematical models of dust flux to be successful in these landscapes, new landscape models are required which incorporate the existence and orientation of streets.

Okin, Gregory Stewart; Gillette, Dale A.

2001-05-01

262

Trace metals in soil and vegetables and associated health risk assessment.  

PubMed

The objective of this study was to assess the contamination level of trace metals in soil and vegetables and health risk to the urban population in Bangladesh. The range of Cr, Ni, Cu, As, Cd, and Pb in agricultural soils was 158-1160, 104-443, 157-519, 41-93, 3.9-13, and 84-574 mg/kg, respectively. Sequential extraction tests revealed that the studied metals were predominantly associated with the residual fraction, followed by the organically bound phase. Concerning Cu, Ni, Cd, and Pb in vegetables, more than 50 % samples exceeded the FAO/WHO recommended permissible limits. Considering the transfer of metals from soil to vegetables, Cu and Cd exhibited higher transfer factor (TF) values than the other metals. Target hazard quotient (THQ) for individual metal was below 1, suggesting that people would not experience significant health hazards if they ingest a single metal from vegetables. However, total metal THQ signifies the potential non-carcinogenic health hazard to the highly exposed consumers. The carcinogenic risk (TR) of As (1.9?×?10(-4)) and Pb (2.3?×?10(-5)) through consumption of vegetables were higher than the USEPA threshold level (10(-6)), indicating potential cancer risks. PMID:25204898

Islam, Md Saiful; Ahmed, Md Kawser; Habibullah-Al-Mamun, Md; Masunaga, Shigeki

2014-12-01

263

Dynamic floodplain vegetation model development for the Kootenai River, USA.  

PubMed

The Kootenai River floodplain in Idaho, USA, is nearly disconnected from its main channel due to levee construction and the operation of Libby Dam since 1972. The decreases in flood frequency and magnitude combined with the river modification have changed the physical processes and the dynamics of floodplain vegetation. This research describes the concept, methodologies and simulated results of the rule-based dynamic floodplain vegetation model "CASiMiR-vegetation" that is used to simulate the effect of hydrological alteration on vegetation dynamics. The vegetation dynamics are simulated based on existing theory but adapted to observed field data on the Kootenai River. The model simulates the changing vegetation patterns on an annual basis from an initial condition based on spatially distributed physical parameters such as shear stress, flood duration and height-over-base flow level. The model was calibrated and the robustness of the model was analyzed. The hydrodynamic (HD) models were used to simulate relevant physical processes representing historic, pre-dam, and post-dam conditions from different representative hydrographs. The general concept of the vegetation model is that a vegetation community will be recycled if the magnitude of a relevant physical parameter is greater than the threshold value for specific vegetation; otherwise, succession will take place toward maturation stage. The overall accuracy and agreement Kappa between simulated and field observed maps were low considering individual vegetation types in both calibration and validation areas. Overall accuracy (42% and 58%) and agreement between maps (0.18 and 0.27) increased notably when individual vegetation types were merged into vegetation phases in both calibration and validation areas, respectively. The area balance approach was used to analyze the proportion of area occupied by different vegetation phases in the simulated and observed map. The result showed the impact of the river modification and hydrological alteration on the floodplain vegetation. The spatially distributed vegetation model developed in this study is a step forward in modeling riparian vegetation succession and can be used for operational loss assessment, and river and floodplain restoration projects. PMID:21852032

Benjankar, Rohan; Egger, Gregory; Jorde, Klaus; Goodwin, Peter; Glenn, Nancy F

2011-12-01

264

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

NASA Astrophysics Data System (ADS)

Boreal landscapes are characterized by a mosaic of uplands and lowlands, which differ in plant species composition, litter biochemistry, and biogeochemical cycling rates. Boreal ecosystems, from upland black spruce stands to lowland fens, are structured largely by water table position and contain quantitatively and qualitatively different forms of soil organic matter. Differences in carbon (C) availability among ecosystems likely translate to differences in the structure of soil microbial communities, which in turn could affect rates of organic matter decomposition and turnover. We examined relationships between microbial communities and soil C turnover in near-surface soils along a topographic soil moisture and vegetation gradient in interior Alaska. We tested the hypothesis that upland black spruce sites would be dominated by soil fungi and have slow rates of C turnover, whereas lowland ecosystems would be dominated by bacteria and mesofauna (enchytraeids) and have more rapid rates of C turnover. We utilized several isotopic measures of soil C turnover including bomb radiocarbon techniques, the ?15N of SOM, and the difference between ?13C of SOM, DOC, and respired CO2. All three measures indicated greater C turnover rates in the surface soils of the lowland fen sites compared to the more upland locations. Quantitative PCR analyses of soil bacteria and archaea, combined with enchytraed counts, confirmed that surface soils from the lowland fen ecosystems had the highest abundances of these functional groups. Fungal biomass was highly variable and tended to be more abundant in the upland forest sites. Soil enzymatic results were mixed: potential cellulase activities were higher in the more upland soils even though rates of microbial activity were generally lower. Oxidative enzyme activities were higher in fens, even though these ecosystems are saturated and partly anaerobic. Overall our data support soil food web theory which argues that rapidly cycling systems are bacterial dominated with mesofaunal grazing, whereas slowly cycling systems have characteristic higher fungal:bacterial ratios.

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

2010-12-01

265

The influence of vegetation on sedimentation and resuspension of soil particles in small constructed wetlands.  

PubMed

When initiatives to mitigate soil erosion are insufficient or fail, constructed surface flow wetlands (CWs) could be a final buffer to reduce pollution before reaching recipients. The objective of this study was to determine the influence of CW vegetation on the retention of soil particles from arable land. Retention was measured with water flow-proportional sampling systems in the inlet and outlet, sedimentation traps, and sedimentation plates in four small CWs over a period of 5 yr. The surface area of the CWs was 265 to 900 m2, and the average hydraulic loads were 1.2 to 3.4 m d(-1). Watershed areas were 0.5 to 1.5 km2. Annual soil particle retention was 30 to 80% or 14 to 121 kg m(-2). Results show that macrophytes stimulate sediment retention by mitigating resuspension of CW sediment. Five years after construction, resuspension had decreased approximately 40% and was negligible. As vegetation cover increases, the influence of macrophytes on soil particle retention reaches a level where other factors, such as hydraulic load and sediment load, were more important. Macrophytes increased the hydraulic efficiency by reducing short-circuit or preferential flow. However, vegetation did not have any influence on the clay concentration in the sediment. Hence, a possible stimulation of particle flocculation was not detected. Vegetation makes it possible to use the positive effect of a short particle settling distance in shallow ponds by hindering resuspension. PMID:11476524

Braskerud, B C

2001-01-01

266

Soil–vegetation relationships in a coastal desert plain of southern Sinai, Egypt  

Microsoft Academic Search

The present study provides an analysis of soil, vegetation types as well as structure and species distribution in 19 sites in El-Qaa plain along the Gulf of Suez (south Sinai, Egypt), and focuses on the environmental factors that control the species distribution. A total of 203 species belonging to 39 families of the vascular plants are recorded. Asteraceae, Fabaceae, Chenopodiaceae

Monier M. Abd El-Ghani; Wafaa M Amer

2003-01-01

267

Mapping active fault-induced changes in soil and vegetation. Roer Graben (Belgium)  

Microsoft Academic Search

The recent seismic activity of the border faults of the Roer Graben has regional and local effects on topography as well as on the composition, chemistry and wetness of soils and on the vegetation overburden. Though so metimes quite important and visible on air photos and satel lite imagery, these effects are most often quite su btle and a high

M. Fernandez; K. Vanneste; K. Verbeeck; T. Camelbeeck

268

FLUE GAS DESULFURIZATION SLUDGE: ESTABLISHMENT OF VEGETATION ON PONDED AND SOIL-APPLIED WASTE  

EPA Science Inventory

The report gives results of research to identify and evaluate forms of vegetation and methods of their establishment for reclaiming retired flue gas desulfurization sludge ponds. Also studied were the soil liming value of limestone scrubber sludge (LSS) and plant uptake and perco...

269

Heavy metal contamination of soil and vegetables in suburban areas of Varanasi, India  

Microsoft Academic Search

Heavy metal contamination of soil resulting from wastewater irrigation is a cause of serious concern due to the potential health impacts of consuming contaminated produce. In this study an assessment is made of the impact of wastewater irrigation on heavy metal contamination of Beta vulgaris (palak); this is a highly nutritious leafy vegetable that is widely cultivated and consumed in

Rajesh Kumar Sharma; Madhoolika Agrawal; Fiona Marshall

2007-01-01

270

Soil and groundwater chemistry and vegetation distribution in a desert playa, Owens Lake, California  

Microsoft Academic Search

Generation of fine particulate dust (PM10)from the Owens Lake play a creates a severe air pollution hazard in the western Great Basin of the United States. One proposed mitigation strategy involves establishment of native vegetation to stabilize and trap fugitive sand. This study investigated soil and groundwater chemistry and the distribution of native plant species in relation to salts and

R. A. Dahlgren; J. H. Richards; Z. Yu

1997-01-01

271

Microbial Communities in Cerrado Soils under Native Vegetation Subjected to Prescribed Fires and Under Pasture  

EPA Science Inventory

The objective of this work was to evaluate the effects of fire regimes and vegetation cover on the structure and dynamics of soil microbial communities, through phospholipid fatty acid (PLFA) analysis. Comparisons were made between native areas with different woody covers ("cerra...

272

Utilization of Crawfish Peeling Plant Waste as a Soil Amendment for Vegetable Crop Production.  

National Technical Information Service (NTIS)

Crawfish waste applied at proper rates to vegetable crops will provide many of the essential nutrients required for growth and production. The crop response is influenced by rates of application and by the type of crop. The soil analysis reveals definite ...

R. Barry

1980-01-01

273

Radionuclide concentrations in terrestrial vegetation and soil on and around the Hanford Site, 1983 through 1993  

SciTech Connect

This report reviews concentrations of {sup 60}Co, {sup 90}Sr, {sup 137}Cs, U isotopes, {sup 238}Pu, {sup 239,240}Pu, and {sup 241}Am in soil and vegetation samples collected from 1983 through 1993 during routine surveillance of the Hanford Site. Sampling locations were grouped in study areas associated with operational areas on the Site. While radionuclide concentrations were very low and representative of background concentrations from historic fallout, some study areas on the Site contained slightly elevated concentrations compared to other study areas onsite and offsite. The 100 Areas had concentrations of {sup 60}Co comparable to the minimum detectable concentration of 0.02 pCi/g in soil. Concentrations of {sup 90}Sr, {sup 137}Cs, {sup 238}Pu, {sup 239,240}Pu, and {sup 241}Am in 200 Area soils were slightly elevated. The 300 Area had a slight elevation of U in soil. These observations were expected because many of the sampling locations were selected to monitor specific facilities or operations at the operational areas. Generally, concentrations of the radionuclides studied were greater and more readily measured in soil samples compared to vegetation samples. The general pattern of concentrations of radionuclide concentrations in vegetation by area mirrored that observed in soil. Declines in {sup 90}Sr in soil appear to be attributed to radioactive decay and possibly downward migration out of the sampling horizon. The other radionuclides addressed in this report strongly sorb to soil and are readily retained in surface soil. Because of their long half-lives compared to the length of the study period, there was no significant indication that concentrations of U isotopes and Pu isotopes were decreasing over time.

Poston, T.M.; Antonio, E.J.; Cooper, A.T.

1995-08-01

274

Wetland soil and vegetation bismuth content following experimental deposition of bismuth pellets.  

PubMed

Bismuth pellets have been approved as a non-toxic alternative to lead pellets in Canada since 1997 but, to our knowledge, there is little literature for soil and vegetation bismuth content in areas of bismuth pellet deposition. The present study addresses this shortcoming by measuring wetland soil and vegetation bismuth content following experimental deposition of bismuth pellets under ambient and experimentally increased acidic deposition conditions. We manipulated 24 plots in a fully factorial design (bismuth shot x soil acidification) in a south-eastern Ontario freshwater wetland during 1999-2003. Soil pH (range 6.5-7.3) increased significantly (p = 0.001) during the experimental period but there were no significant differences amongst treatments (p = 0.79). Significantly (p < 0.05) greater bismuth concentrations were measured in soil receiving bismuth pellets (mean +/- SE, n = 6; with acidification = 2.55 +/- 1.02 microg Bi g(-1) dry mass [DM]; without acidification = 6.40 +/- 2.23 microg Bi g(-1) DM) compared to plots that were not seeded with bismuth pellets (without acidification = 0.42 +/- 0.09 microg Bi g(-1) DM; with acidification = 0.39 +/- 0.10 microg Bi g(-1) DM). Nevertheless, bismuth levels in 20 of 24 aboveground tissue samples from the Carex lacustris-Agrostis scabra community were below detection levels (0.057 microg Bi g(-1) DM); the other samples ranged from 0.065 to 0.095 microg Bi g(-1) DM, similar to global background levels. Primary productivity in plots receiving bismuth pellets and soil acidification was not significantly (p = 0.15) different to vegetation in plots that were not manipulated. The results suggest bismuth mobilization from bismuth pellets into soil but not to aboveground vegetation. PMID:18688464

Fahey, Nathan S C; Karagatzides, Jim D; Jayasinghe, Ruwan; Tsuji, Leonard J S

2008-08-01

275

Identification and representability of processes controlling unsaturated flow in vegetated soils at differing temporal scales  

NASA Astrophysics Data System (ADS)

A model describing unsaturated flow in vegetated soil has been developed, coupling plant feedback mechanisms with a finite-difference implementation of Richards' equation. While care has been taken to relate all parameters and processes to physically realistic analogies, moderate uncertainty in a range of parameters is unavoidable due to the need for characterisation of pedo-transfer functions and the complexity of plant water processes. Confidence in model effectiveness has been addressed through simulations of lysimeter experiments undertaken at Imperial College. A highly comprehensive data set consists of measurements on eight lysimeters divided into two sets of four, with the two sets containing different soil types. The water table was maintained at 65 cm below the soil surface, and all possessed a mature crop of perennial ryegrass (Lolium perenne L.) by the start of the experiment. Measurements of soil hydrological status and onsite meteorological data were taken about every quarter of an hour for a period of close to a year, providing detailed information on events within the lysimeters, and the impact of various meteorological conditions over the year. Diurnal variation and seasonal responses are particularly clear. An application of sensitivity and uncertainty analysis to the model, using this detailed data set, has been undertaken. In the performance of the optimisation process, good quality of model definition at both diurnal and seasonal scales is treated as particularly important, as is the effect of measurement error on parameterisation at these different scales. Since we are correcting parameter estimates in the presence of measurement error, it is important to have an understanding of the distortions produced on the outputs by noise. Therefore, a Bayesian framework is used to facilitate the treatment of both measurement and parametric errors, and to allow the inclusion of subjective probability without losing mathematical rigour. Metropolis Hastings Monte-Carlo methods are used to approximate the posterior distribution for parameters of interest. Due to the complicated topology of the posterior probability, a range of different heuristic algorithms, including simulated annealing, has been investigated in order to aid the search for hard to find modes in which the posterior achieves substantial local maxima. Examination of such maxima aids in addressing questions of parameter and overall model identifiability.

Butler, A. P.; Jackson, B. M.

2003-04-01

276

Transregional Collaborative Research Centre 32: Patterns in Soil-Vegetation-Atmosphere-Systems  

NASA Astrophysics Data System (ADS)

The soil-vegetation-atmosphere (SVA) system is characterized by non-linear multi-scale exchange processes concerning mass, momentum and energy resulting in complex spatial and temporal patterns and structures. Under the TR32 framework, the characterisation of these structures and patterns will lead to a deeper qualitative and quantitative understanding of the SVA system, and ultimately to better predictions of the SVA state. TR32-research is based on three methodological pillars: Monitoring, Modelling and Data Assimilation. While focusing on the Rur Catchment (Germany), patterns are monitored since 2006 continuously using existing and novel geophysical and remote sensing techniques from the local to the catchment scale like ground penetrating radar, polarimetric precipitation and cloud radar imaging, spectrally induced polarization, radiomagnetotellurics, electrical resistivity tomography, boundary layer scintillometry, lidar techniques, cosmic-ray, and microwave radiometry. Model development centers around a coupled model platform TerrSysMP, which considers mutual fluxes from the groundwater to the atmosphere from the meter to the kilometer scale by combining the atmospheric model COSMO, the land surface model CLM, and the hydrological model ParFlow in a scale-consistent way using the external OASIS coupler. Another focus is a LES model coupled to a novel landsurface scheme, which has been developed for a better understanding of the propagation of patterns between landsurface and atmosphere and their mutual interactions. A range of projects focus on smaller scales processes e.g. down to individual roots, which are modelled at high resolution in order to develop suitable parametrisations for TerrSysMP. Other research foci of TR32 are the transfer of results and developed technology related to new soil analysis tools from the laboratory to the field, the quantification of patterns of soil-carbon, evapotranspiration and respiration in the field, and the setup and operation of the atmospheric boundary layer, cloud and precipitation monitoring site JOYCE (Jülich ObservatorY for Cloud Evolution). These modern and predominantly non-invasive measurement techniques are exploited in combination with advanced modelling systems by data assimilation to yield improved predictions of the transfers of water-, energy and CO2 by accounting for the patterns occurring at various scales. We will present selected results and remaining challenges for characterizing the intertwined patterns and structure at the catchment scale.

Thiele-Eich, Insa; Simmer, Clemens; Diekkrüger, Bernd; Crewell, Susanne; Klitzsch, Norbert; Vereecken, Harry; Kollet, Stefan; Hintz, Michael

2014-05-01

277

Contributions of Understory and/or Overstory Vegetations to Soil Microbial PLFA and Nematode Diversities in Eucalyptus Monocultures  

PubMed Central

Ecological interactions between aboveground and belowground biodiversity have received many attentions in the recent decades. Although soil biodiversity declined with the decrease of plant diversity, many previous studies found plant species identities were more important than plant diversity in controlling soil biodiversity. This study focused on the responses of soil biodiversity to the altering of plant functional groups, namely overstory and understory vegetations, rather than plant diversity gradient. We conducted an experiment by removing overstory and/or understory vegetation to compare their effects on soil microbial phospholipid fatty acid (PLFA) and nematode diversities in eucalyptus monocultures. Our results indicated that both overstory and understory vegetations could affect soil microbial PLFA and nematode diversities, which manifested as the decrease in Shannon–Wiener diversity index (H?) and Pielou evenness index (J) and the increase in Simpson dominance index (?) after vegetation removal. Soil microclimate change explained part of variance of soil biodiversity indices. Both overstory and understory vegetations positively correlated with soil microbial PLFA and nematode diversities. In addition, the alteration of soil biodiversity might be due to a mixing effect of bottom-up control and soil microclimate change after vegetation removal in the studied plantations. Given the studied ecosystem is common in humid subtropical and tropical region of the world, our findings might have great potential to extrapolate to large scales and could be conducive to ecosystem management and service. PMID:24427315

Liu, Zhanfeng; Zhou, Lixia; Fu, Shenglei

2014-01-01

278

Contributions of understory and/or overstory vegetations to soil microbial PLFA and nematode diversities in Eucalyptus monocultures.  

PubMed

Ecological interactions between aboveground and belowground biodiversity have received many attentions in the recent decades. Although soil biodiversity declined with the decrease of plant diversity, many previous studies found plant species identities were more important than plant diversity in controlling soil biodiversity. This study focused on the responses of soil biodiversity to the altering of plant functional groups, namely overstory and understory vegetations, rather than plant diversity gradient. We conducted an experiment by removing overstory and/or understory vegetation to compare their effects on soil microbial phospholipid fatty acid (PLFA) and nematode diversities in eucalyptus monocultures. Our results indicated that both overstory and understory vegetations could affect soil microbial PLFA and nematode diversities, which manifested as the decrease in Shannon-Wiener diversity index (H') and Pielou evenness index (J) and the increase in Simpson dominance index (?) after vegetation removal. Soil microclimate change explained part of variance of soil biodiversity indices. Both overstory and understory vegetations positively correlated with soil microbial PLFA and nematode diversities. In addition, the alteration of soil biodiversity might be due to a mixing effect of bottom-up control and soil microclimate change after vegetation removal in the studied plantations. Given the studied ecosystem is common in humid subtropical and tropical region of the world, our findings might have great potential to extrapolate to large scales and could be conducive to ecosystem management and service. PMID:24427315

Zhao, Jie; Wan, Songze; Zhang, Chenlu; Liu, Zhanfeng; Zhou, Lixia; Fu, Shenglei

2014-01-01

279

Evaluation of microbial inoculation and vegetation to enhance the dissipation of atrazine and metolachlor in soil.  

PubMed

Four greenhouse studies were conducted to evaluate the effects of native prairie grasses and two pesticide-degrading bacteria to remediate atrazine and metolachlor in soils from agricultural dealerships (Alpha site soil, northwest Iowa, USA; Bravo site soil, central Iowa, USA). The Alpha soil contained a low population of atrazine-degrading microorganisms relative to the Bravo soil. Each soil freshly treated with atrazine or metolachlor was aged for a short or long period of time, respectively. An atrazine-degrading bacterium, Agrobacterium radiobacter strain J14a; a metolachlor-degrading bacterium, Pseudomonas fluorescens strain UA5-40; and a mixture of three native prairie grasses-big bluestem (Andropogon gerardii Vitman), yellow Indian grass (Sorghastrum nutans [L.] Nash), and switchgrass (Panicum virgatum L.)-were added to the soils after the soils were aged for long periods of time. The soils aged for short periods of time were treated with J14a, the prairie grasses, or both after aging. The J14a and the grasses significantly reduced the concentration of atrazine in Alpha soil when the soil was aged for a short period of time. However, these treatments had no statistically significant effect when the soil was aged for a long period of time or on atrazine in Bravo soil. Inoculation with UA5-40 did not enhance metolachlor dissipation in either soil, but vegetation did increase metolachlor dissipation. Our results indicate that the dissipation of atrazine by J14a is affected by the presence of indigenous atrazine-mineralizing microorganisms and probably by the bioavailability of atrazine in the soil. PMID:16268144

Zhao, Shaohan; Arthur, Ellen L; Moorman, Thomas B; Coats, Joel R

2005-10-01

280

Estimating soil water retention using soil component additivity model  

NASA Astrophysics Data System (ADS)

Soil water retention is a major soil hydraulic property that governs soil functioning in ecosystems and greatly affects soil management. Data on soil water retention are used in research and applications in hydrology, agronomy, meteorology, ecology, environmental protection, and many other soil-related fields. Soil organic matter content and composition affect both soil structure and adsorption properties; therefore water retention may be affected by changes in soil organic matter that occur because of both climate change and modifications of management practices. Thus, effects of organic matter on soil water retention should be understood and quantified. Measurement of soil water retention is relatively time-consuming, and become impractical when soil hydrologic estimates are needed for large areas. One approach to soil water retention estimation from readily available data is based on the hypothesis that soil water retention may be estimated as an additive function obtained by summing up water retention of pore subspaces associated with soil textural and/or structural components and organic matter. The additivity model and was tested with 550 soil samples from the international database UNSODA and 2667 soil samples from the European database HYPRES containing all textural soil classes after USDA soil texture classification. The root mean square errors (RMSEs) of the volumetric water content estimates for UNSODA vary from 0.021 m3m-3 for coarse sandy loam to 0.075 m3m-3 for sandy clay. Obtained RMSEs are at the lower end of the RMSE range for regression-based water retention estimates found in literature. Including retention estimates of organic matter significantly improved RMSEs. The attained accuracy warrants testing the 'additivity' model with additional soil data and improving this model to accommodate various types of soil structure. Keywords: soil water retention, soil components, additive model, soil texture, organic matter.

Zeiliger, A.; Ermolaeva, O.; Semenov, V.

2009-04-01

281

Coevolution of topography, hydrology, soil development, and vegetation in sky islands of the southwestern United States  

NASA Astrophysics Data System (ADS)

The sky islands of the southwestern U.S. offer a unique opportunity to study the coevolution of landscape processes in areas of similar rock type and tectonic history but a wide range of climates. In this study we compile high-resolution, spatially-distributed data for the available energy to drive rock weathering and other landscape processes, i.e. the Effective Energy and Mass Transfer (EEMT) variable of Rasmussen and Tabor (2005), together with data for LiDAR-derived above-ground biomass, soil thickness, water storage potential, hillslope relief, and valley density in the Santa Catalina and Pinaleno Mountains, two predominantly granitic ranges in southern Arizona. Strong correlations exist among these variables such that warm, dry, low elevation portions of these areas are characterized by low biomass, thin soils, low water-storage potential, steep slopes, and high valley densities. Cooler, wetter, higher-elevation portions have systematically higher biomass, thicker soils, higher water-storage potential, gentler slopes, and lower valley densities. Moreover, all of these variables have a nonlinear dependence on climate/elevation. Slope gradient and aspect also exert an important control on these variables, with steep, south-facing hillslopes characterized by drier-than-average conditions for a given elevation and north-facing slopes associated with wetter-than-average conditions. We hypothesize that these correlations partly reflect coevolutionary positive-feedback mechanisms among these processes that amplify differences in rates set by climate, tectonics, and rock type. For example, thicker soils with higher water storage potential that form at higher elevations/north-facing slopes tend to have greater biomass, causing lower runoff ratios, lower rates of slopewash and fluvial erosion, and increased rates of colluvial transport, thereby promoting thicker soils, lower-gradient slopes, and lower valley densities. Thicker soils and higher water storage potentials, in turn, promote greater biomass in a positive feedback. To test this hypothesis, we developed a landscape evolution model that couples soil development, the partitioning of rainfall into runoff, infiltration, and evapotranspiration, vegetation growth, and geomorphic processes (colluvial and fluvial transport) over geologic time scales. Numerical experiments with this model can be run for a range of input data for climate, tectonics, and rock type. Across a climate gradient similar to that of the sky islands of the southwestern U.S., the model self-organizes into states similar to those observed in the Santa Catalina and Pinaleno ranges, i.e. higher biomass, thicker soils, higher water storage potential, lower relief, and lower valley density at higher elevations/north-facing slopes. The model exhibits similar nonlinear relationships among landscape variables across the elevation/climate gradient, lending support to the hypothesis that positive feedback mechanisms contribute to the observed nonlinearity.

Pelletier, J. D.; Rasmussen, C.; Breshears, D. D.; Brooks, P. D.; Chorover, J.; Huxman, T. E.; Lohse, K. A.; Meixner, T.; McIntosh, J. C.; Kurc, S. A.; Schaap, M. G.; Swetnam, T.; Troch, P. A.; University Of Arizona Czo

2010-12-01

282

Stochastic Modeling of Soil Salinity  

E-print Network

A minimalist stochastic model of primary soil salinity is proposed, in which the rate of soil salinization is determined by the balance between dry and wet salt deposition and the intermittent leaching events caused by rainfall events. The long term probability density functions of salt mass and concentration are found by reducing the coupled soil moisture and salt mass balance equation to a single stochastic differential equation driven by multiplicative Poisson noise. The novel analytical solutions provide insight on the interplay of the main soil, plant and climate parameters responsible for long-term soil salinization. In particular, they show the existence of two distinct regimes, one where the mean salt mass remains nearly constant (or decreases) with increasing rainfall frequency, and another where mean salt content increases markedly with increasing rainfall frequency. As a result, relatively small reductions of rainfall in drier climates may entail dramatic shifts in long-term soil salinization trend...

Suweis, S; Van der Zee, S E A T M; Daly, E; Maritan, A; Porporato, A; 10.1029/2010GL042495

2012-01-01

283

Laboratory and Airborne BRDF Analysis of Vegetation Leaves and Soil Samples  

NASA Technical Reports Server (NTRS)

Laboratory-based Bidirectional Reflectance Distribution Function (BRDF) analysis of vegetation leaves, soil, and leaf litter samples is presented. The leaf litter and soil samples, numbered 1 and 2, were obtained from a site located in the savanna biome of South Africa (Skukuza: 25.0degS, 31.5degE). A third soil sample, number 3, was obtained from Etosha Pan, Namibia (19.20degS, 15.93degE, alt. 1100 m). In addition, BRDF of local fresh and dry leaves from tulip tree (Liriodendron tulipifera) and acacia tree (Acacia greggii) were studied. It is shown how the BRDF depends on the incident and scatter angles, sample size (i.e. crushed versus whole leaf,) soil samples fraction size, sample status (i.e. fresh versus dry leaves), vegetation species (poplar versus acacia), and vegetation s biochemical composition. As a demonstration of the application of the results of this study, airborne BRDF measurements acquired with NASA's Cloud Absorption Radiometer (CAR) over the same general site where the soil and leaf litter samples were obtained are compared to the laboratory results. Good agreement between laboratory and airborne measured BRDF is reported.

Georgiev, Georgi T.; Gatebe, Charles K.; Butler, James J.; King, Michael D.

2008-01-01

284

Concentrations of Radionuclides and Trace Elements in Soils and Vegetation Around the DARHT Facility during 2004  

SciTech Connect

Samples of soil, sediment, and unwashed overstory and understory vegetation were collected at four locations around the Dual-Axis Radiographic Hydrodynamic Test (DARHT) facility at Los Alamos National Laboratory (LANL). All samples were analyzed for concentrations of {sup 3}H, {sup 137}Cs, {sup 90}Sr, {sup 238}Pu, {sup 239,240}Pu, {sup 241}Am, {sup 234}U, {sup 235}U, {sup 238}U, Ag, As, Ba, Be, Cd, Cr, Cu, Hg, Ni, Pb, Sb, Se, and Tl. These results, which represent five years since the start of operations, were compared with baseline statistical reference level (BSRL) data established over a four-year-long preoperational period prior to DARHT operations, and to LANL and U.S. Environmental Protection Agency Screening Action Levels (SALs). Most radionuclides and trace elements in soil, sediment, and vegetation were below BSRL values and those soils/sediments that were above BSRLs were far below SALs.

P.R. Fresquez

2004-10-01

285

Pollution Status of Pakistan: A Retrospective Review on Heavy Metal Contamination of Water, Soil, and Vegetables  

PubMed Central

Trace heavy metals, such as arsenic, cadmium, lead, chromium, nickel, and mercury, are important environmental pollutants, particularly in areas with high anthropogenic pressure. In addition to these metals, copper, manganese, iron, and zinc are also important trace micronutrients. The presence of trace heavy metals in the atmosphere, soil, and water can cause serious problems to all organisms, and the ubiquitous bioavailability of these heavy metal can result in bioaccumulation in the food chain which especially can be highly dangerous to human health. This study reviews the heavy metal contamination in several areas of Pakistan over the past few years, particularly to assess the heavy metal contamination in water (ground water, surface water, and waste water), soil, sediments, particulate matter, and vegetables. The listed contaminations affect the drinking water quality, ecological environment, and food chain. Moreover, the toxicity induced by contaminated water, soil, and vegetables poses serious threat to human health.

Arshad, Jahanzaib; Iqbal, Farhat; Sajjad, Ashif; Mehmood, Zahid

2014-01-01

286

Measuring soil moisture with active microwave: effect of vegetation  

Microsoft Academic Search

An empirical algorithm for the retrieval of soil moisture content and surface root mean square (RMS) height from remotely sensed radar data over bare fields requiring two co-polarized channels at a frequency between 1.5 GHz and 11 GHz is presented. It gives best results for kh less than 2.5 where k is the wave number and h is the RMS

P. C. Dubois; J. van Zyl; T. Engman

1995-01-01

287

Effects of Soil Moisture Variations on Deposition Velocities Above Vegetation  

Microsoft Academic Search

The parameterized subgrid-scale surface flux (PASS) modelprovides a simplified means of using remote sensing data from satellites and limited surface meteorological information to estimate the influence of soil moisture on bulk canopy stomatalresistances to the uptake of gases over extended areas.PASS-generated estimates of bulk canopy stomatal resistance were usedin a dry deposition module to compute gas deposition velocitieswith a horizontal

M. L. Wesely; J. Song; R. T. Mcmillen; T. P. Meyers

2001-01-01

288

Identifying environmental controls on vegetation greenness phenology through model-data integration  

NASA Astrophysics Data System (ADS)

Existing dynamic global vegetation models (DGVMs) have a~limited ability in reproducing phenology and decadal dynamics of vegetation greenness as observed by satellites. These limitations in reproducing observations reflect a poor understanding and description of the environmental controls on phenology, which strongly influence the ability to simulate longer term vegetation dynamics, e.g. carbon allocation. Combining DGVMs with observational data sets can potentially help to revise current modelling approaches and thus to enhance the understanding of processes that control seasonal to long-term vegetation greenness dynamics. Here we implemented a~new phenology model within the LPJmL (Lund Potsdam Jena managed lands) DGVM and integrated several observational data sets to improve the ability of the model in reproducing satellite-derived time series of vegetation greenness. Specifically, we optimized LPJmL parameters against observational time series of the fraction of absorbed photosynthetic active radiation (FAPAR), albedo and gross primary production to identify the main environmental controls for seasonal vegetation greenness dynamics. We demonstrated that LPJmL with new phenology and optimized parameters better reproduces seasonality, inter-annual variability and trends of vegetation greenness. Our results indicate that soil water availability is an important control on vegetation phenology not only in water-limited biomes but also in boreal forests and the arctic tundra. Whereas water availability controls phenology in water-limited ecosystems during the entire growing season, water availability co-modulates jointly with temperature the beginning of the growing season in boreal and arctic regions. Additionally, water availability contributes to better explain decadal greening trends in the Sahel and browning trends in boreal forests. These results emphasize the importance of considering water availability in a new generation of phenology modules in DGVMs in order to correctly reproduce observed seasonal to decadal dynamics of vegetation greenness.

Forkel, M.; Carvalhais, N.; Schaphoff, S.; Bloh, W. v.; Migliavacca, M.; Thurner, M.; Thonicke, K.

2014-07-01

289

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

USGS Publications Warehouse

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.

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

2008-01-01

290

\\vspace{8mm}Inclusion of vegetation in the Town Energy Balance model for modelling urban green areas  

NASA Astrophysics Data System (ADS)

Cities impact both local climate, through urban heat islands and global climate, because they are an area of heavy greenhouse gas release into the atmosphere due to heating, air conditioning and traffic. Including more vegetation into cities is a planning strategy having possible positive impacts for both concerns. Improving vegetation representation into urban models will allow us to address more accurately these questions. This paper presents an improvement of the Town Energy Balance (TEB) urban canopy model. Vegetation is directly included inside the canyon, allowing shadowing of grass by buildings, better representation of urban canopy form and, a priori, a more accurate simulation of canyon air microclimate. The surface exchanges over vegetation are modelled with the well-known Interaction Soil Biosphere Atmosphere (ISBA) model that is integrated in the TEB's code architecture in order to account for interactions between natural and built-up covers. The design of the code makes possible to plug and use any vegetation scheme. Both versions of TEB are confronted to experimental data issued from a field campaign conducted in Israel in 2007. Two semi-enclosed courtyards arranged with bare soil or watered lawn were instrumented to evaluate the impact of landscaping strategies on microclimatic variables and evapotranspiration. For this case study, the new version of the model with integrated vegetation performs better than if vegetation is treated outside the canyon. Surface temperatures are closer to the observations, especially at night when radiative trapping is important. The integrated vegetation version simulates a more humid air inside the canyon. The microclimatic quantities (i.e., the street-level meteorological variables) are better simulated with this new version. This opens opportunities to study with better accuracy the urban microclimate, down to the micro (or canyon) scale.

Lemonsu, A.; Masson, V.; Shashua-Bar, L.; Erell, E.; Pearlmutter, D.

2012-11-01

291

[Effects of vegetable cultivation years on microbial biodiversity and abundance of nitrogen cycling in greenhouse soils].  

PubMed

The effects of facility vegetable cultivation years (three, nine, fourteen or seventeen years) on biodiversity and abundance of soil microorganisms, such as bacteria, ammonia oxidizing bacteria (AOB) and nirK type denitrifying bacteria, in the greenhouse soils in Wuwei of Gansu Province, China were determined by the combined analyses of terminal restriction fragment length polymorphism (T-RFLP) and real-time quantitative PCR. The results showed that the dominant population structure and abundance of bacteria, AOB, nirK type denitrifying bacteria in the soils were significantly different from those in the farmland fields. The dominant population also changed with the cultivation years. With the increase of vegetable cultivation years, the abundance of 16S rRNA and nirK gene in the 0-20 cm soil layer first increased and then decreased, with the maximum values of 9.67 x 10(9) and 2.30 x 10(7) copies x g(-1) soil at year 14 and year 9, being as 1.51 and 1.52 times of that of the 3-year, respectively. However, the abundance of amoA gene showed an opposite trend. The amoA gene copy number in the 14-year sample was 3.28 x 10(7) copies x g(-1) soil, which was only 45.7% of that of the 3-year. These results illustrated that the ecological adaptation mechanisms of the different functional microorganisms involved in nitrogen cycling had significant differences in the facility vegetable soils, and provided a base for further researches on exploring and explaining the characteristics and adaptation mechanisms of microorganisms in greenhouse soil. PMID:25011307

Wang, Ya-Nan; Zeng, Xi-Bai; Wang, Yu-Zhong; Bai, Ling-Yu; Su, Shi-Ming; Wu, Cui-Xia; Li, Lian-Fang; Duan, Ran

2014-04-01

292

[Estimation models of vegetation fractional coverage (VFC) based on remote sensing image at different radiometric correction levels].  

PubMed

The images of post atmospheric correction reflectance (PAC), top of atmosphere reflectance (TOA), and digital number (DN) of a SPOT5 HRG remote sensing image of Nanjing, China were used to derive four vegetation indices (VIs), i. e., normalized difference vegetation index (NDVI), transformed vegetation index (TVI), soil-adjusted vegetation index (SAVI), and modified soil-adjusted vegetation index (MSAVI), and 36 VI-VFC relationship models were established based on these VIs and the VFC data obtained from ground measurement. The results showed that among the models established, the cubic polynomial models based on NDVI and TVI from PAC were the best, followed by those based on SAVI and MSAVI from DN, with the accuracy being slightly higher than that of the former two models when VFC > 0.8. The accuracy of these four models was higher in middle-densely vegetated areas (VFC = 0.4-0.8) than in sparsely vegetated areas (VFC = 0-0.4). All the established models could be used in other places via the introduction of calibration models. In VI-VFC modeling, using VIs derived from different radiometric correction levels of remote sensing image could help mining valuable information from remote sensing image, and thus, improving the accuracy of VFC estimation. PMID:18808023

Gu, Zhu-Jun; Zeng, Zhi-Yuan; Shi, Xue-Zheng; Yu, Dong-Sheng; Zheng, Wei; Zhang, Zhen-Long; Hu, Zi-Fu

2008-06-01

293

Modelling Peatlands Vegetation Dynamics at the Ecosystem Scale: Conceptual Basis and Preliminary Results  

NASA Astrophysics Data System (ADS)

Plant species distribution, interactions, and physiology are affected by climate. Thus, climate change is likely to affect vegetation structure and dynamics, especially in boreal, subarctic, and arctic environments, where the greatest climate warming is expected, and where the vegetation seems to be the most sensitive to environmental factors. Peatlands are important components of northern environments, and are functionally important in the terrestrial carbon balance, as they store one third of the global soil carbon as partially decomposed organic material. In no other ecosystem is the vegetation so closely influenced by hydrology and water table dynamics, which in turn influence carbon cycling inside the ecosystem. The process-oriented McGill Wetland Model (MWM) was developed to simulate carbon fluxes from peatlands at the ecosystem scale. An important feedback in the long term simulation of peatland carbon fluxes is the dynamic component of vegetation phenology, resource allocation, and distribution. This contribution introduces a conceptual approach to model vegetation dynamics at the ecosystem scale using MWM. The use of peatland plant functional types is described, as well as the implementation of phenology, nutrient use, species distribution and competition, and resource allocation. Results are compared with an ecosystem-scale field model built around an artificial drainage ditch governing the local water table position. Preliminary results show the importance of including vegetation dynamics when modelling peatlands carbon fluxes at the decadal time scale.

Talbot, J.; Roulet, N. T.; St-Hilaire, F.

2006-12-01

294

Chemical-Specific Representation of Air-Soil Exchange and Soil Penetration in Regional Multimedia Models  

SciTech Connect

In multimedia mass-balance models, the soil compartment is an important sink as well as a conduit for transfers to vegetation and shallow groundwater. Here a novel approach for constructing soil transport algorithms for multimedia fate models is developed and evaluated. The resulting algorithms account for diffusion in gas and liquid components; advection in gas, liquid, or solid phases; and multiple transformation processes. They also provide an explicit quantification of the characteristic soil penetration depth. We construct a compartment model using three and four soil layers to replicate with high reliability the flux and mass distribution obtained from the exact analytical solution describing the transient dispersion, advection, and transformation of chemicals in soil with fixed properties and boundary conditions. Unlike the analytical solution, which requires fixed boundary conditions, the soil compartment algorithms can be dynamically linked to other compartments (air, vegetation, ground water, surface water) in multimedia fate models. We demonstrate and evaluate the performance of the algorithms in a model with applications to benzene, benzo(a)pyrene, MTBE, TCDD, and tritium.

McKone, T.E.; Bennett, D.H.

2002-08-01

295

[Transfer characteristics of cadmium in soil-vegetable-insect food chain].  

PubMed

Taking two kinds of vegetables (Brassica rapa and Amaranthus mangostanus) and one insect species (Prodenia litura) as test materials, a greenhouse pot experiment was conducted to study the transfer characteristics of cadmium (Cd) in soil-vegetable-insect food chain and the distribution patters of different Cd chemical forms in the organs of the two vegetables. With the increasing concentration of applied Cd in soil, the biomass of the two vegetables decreased significantly, while the Cd concentration in the vegetables had a significant increase. The Cd concentration in the vegetable organs decreased in the order of stem > root > leaf for A. mangostanus, and of stem > leaf > root for B. rapa. The Cd concentration in P. litura larvae also increased with the increasing concentration of Cd in soil, and the maximum Cd concentration in the P. litura larvae on B. rapa and A. mangostanus was 36.7 and 46.3 mg x kg(-1), respectively. In the feces of the larvae on B. rapa and A. mangostanus, the Cd concentration was up to 190 and 229.8 mg x kg(-1), respectively, suggesting that the most part of Cd absorbed by P. litura larvae was excreted out of their bodies via feces. In the organs of the two vegetables, NaCl-extractable Cd was the dominant Cd form (> 70%), followed by d-H2O- and ethanol-extractable Cd, while the HAc-extractable Cd (insoluble cadmium phosphate), HCl-extractable Cd (insoluble cadmium oxalate), and residual Cd only had a very low concentration. Such a present pattern of different Cd forms in vegetable organs could be conducive to the Cd transfer in the food chain. P. litura could ease Cd poison by excreting large amount of absorbed Cd via feces, and effectively restrict the transfer of Cd to next trophic level. Since B. rapa and A. mangostanus could accumulate large amount of Cd in their biomass, the two vegetables were suggested not to be planted in highly Cd-contaminated soil. PMID:23431799

Ding, Ping; Zhuang, Ping; Li, Zhi-An; Xia, Han-Ping; Tai, Yi-Ping; Lu, Huan-Ping

2012-11-01

296

Phthalic Acid Esters in Soils from Vegetable Greenhouses in Shandong Peninsula, East China  

PubMed Central

Soils at depths of 0 cm to 10 cm, 10 cm to 20 cm, and 20 cm to 40 cm from 37 vegetable greenhouses in Shandong Peninsula, East China, were collected, and 16 phthalic acid esters (PAEs) were detected using gas chromatography-mass spectrometry (GC-MS). All 16 PAEs could be detected in soils from vegetable greenhouses. The total of 16 PAEs (?16PAEs) ranged from 1.939 mg/kg to 35.442 mg/kg, with an average of 6.748 mg/kg. Among four areas, including Qingdao, Weihai, Weifang, and Yantai, the average and maximum concentrations of ?16PAEs in soils at depths of 0 cm to 10 cm appeared in Weifang, which has a long history of vegetable production and is famous for extensive greenhouse cultivation. Despite the different concentrations of ?16PAEs, the PAE compositions were comparable. Among the 16 PAEs, di(2-ethylhexyl) phthalate (DEHP), di-n-octyl phthalate (DnOP), di-n-butyl phthalate (DnBP), and diisobutyl phthalate (DiBP) were the most abundant. Compared with the results on agricultural soils in China, soils that are being used or were used for vegetable greenhouses had higher PAE concentrations. Among PAEs, dimethyl phthalate (DMP), diethyl phthalate (DEP) and DnBP exceeded soil allowable concentrations (in US) in more than 90% of the samples, and DnOP in more than 20%. Shandong Peninsula has the highest PAE contents, which suggests that this area is severely contaminated by PAEs. PMID:24747982

Chai, Chao; Cheng, Hongzhen; Ge, Wei; Ma, Dong; Shi, Yanxi

2014-01-01

297

Using vegetation indices for soil-moisture retrievals from passive microwave radiometry Hydrology and Earth System Sciences, 5(4), 671677 (2001) EGS  

E-print Network

Using vegetation indices for soil-moisture retrievals from passive microwave radiometry 671 Hydrology and Earth System Sciences, 5(4), 671­677 (2001) © EGS Using vegetation indices for soil-moisture@hwr.arizona.edu Abstract Surface soil moisture and the nature of the overlying vegetation both influence microwave emission

Paris-Sud XI, Université de

298

Regional assessment of soil erosion using the distributed model SEMMED and remotely sensed data  

Microsoft Academic Search

The soil erosion model for Mediterranean regions (SEMMED) is presented and used to produce regional maps of simulated soil loss for two Mediterranean test sites: one in southern France and one in Sicily. The model demonstrates the integrated use of (1) multi-temporal Landsat Thematic Mapper (TM) images to account for vegetation properties, (2) a digital terrain model in a GIS

S. M. de Jong; M. L. Paracchini; F. Bertolo; S. Folving; J. Megier; A. P. J. de Roo

1999-01-01

299

Modeling land surface processes of the midwestern United States : predicting soil moisture under a warmer climate  

E-print Network

This dissertation seeks to quantify the response of soil moisture to climate change in the midwestern United States. To assess this response, a dynamic global vegetation model, Integrated Biosphere Simulator, was coupled ...

Winter, Jonathan (Jonathan Mark)

2010-01-01

300

Detecting vegetation-precipitation feedbacks in mid-Holocene North Africa from two climate models  

SciTech Connect

Using two climate-vegetation model simulations from the Fast Ocean Atmosphere Model (FOAM) and the Community Climate System Model (CCSM, version 2), we investigate vegetation-precipitation feedbacks across North Africa during the mid-Holocene. From mid-Holocene snapshot runs of FOAM and CCSM2, we detect a negative feedback at the annual timescale with our statistical analysis. Using the Monte- Carlo bootstrap method, the annual negative feedback is further confirmed to be significant in both simulations. Additional analysis shows that this negative interaction is partially caused by the competition between evaporation and transpiration in North African grasslands. Furthermore, we find the feedbacks decrease with increasing timescales, and change signs from positive to negative at increasing timescales in FOAM. The proposed mechanism for this sign switch is associated with the different persistent timescales of upper and lower soil water contents, and their interactions with vegetation and atmospheric precipitation.

Wang, Yi; Notaro, Michael; Liu, Zhengyu; Gallimore, Robert; Levis, Samuel; Kutzbach, John E.

2008-03-31

301

Field determination and QSPR prediction of equilibrium-status soil/vegetation partition coefficient of PCDD/Fs.  

PubMed

Characterizing pseudo equilibrium-status soil/vegetation partition coefficient KSV, the quotient of respective concentrations in soil and vegetation of a certain substance at remote background areas, is essential in ecological risk assessment, however few previous attempts have been made for field determination and developing validated and reproducible structure-based estimates. In this study, KSV was calculated based on measurements of seventeen 2,3,7,8-substituted PCDD/F congeners in soil and moss (Dicranum angustum), and rouzi grass (Thylacospermum caespitosum) of two background sites, Ny-Ålesund of the Arctic and Zhangmu-Nyalam region of the Tibet Plateau, respectively. By both fugacity modeling and stepwise regression of field data, the air-water partition coefficient (KAW) and aqueous solubility (SW) were identified as the influential physicochemical properties. Furthermore, validated quantitative structure-property relationship (QSPR) model was developed to extrapolate the KSV prediction to all 210 PCDD/F congeners. Molecular polarizability, molecular size and molecular energy demonstrated leading effects on KSV. PMID:24887127

Li, Li; Wang, Qiang; Qiu, Xinghua; Dong, Yian; Jia, Shenglan; Hu, Jianxin

2014-07-15

302

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

SciTech Connect

This study examines the uptake of explosives by existing vegetation growing in soils contaminated with 2,4,6-trinitrotoluene (TNT) and 1,3,5-trinitro-3,5-triazine (RDX) in three areas at the Iowa Army Ammunition Plant (IAAP). To determine explosives uptake under natural environmental conditions, existing plant materials and soil from the root zone were sampled at different locations in each area, and plant materials were separated by species. Standard methods were used to determine the concentrations of explosives, their derivatives, and metabolites in the soil samples. Plant materials were also analyzed. The compound TNT was not detected in the aboveground portion of plants, and vegetation growing on TNT-contaminated soils is not considered a health hazard. However, soil and plant roots may contain TNT degradation products that may be toxic; hence, their consumption is not advised. The compound RDX was found in the tops and roots of plants growing on RDX-contaminated soils at all surveyed sites. Although RDX is not a listed carcinogen, several of its potentially present degradation products are carcinogens. Therefore, the consumption of any plant tissues growing on RDX-contaminated sites should be considered a potential health hazard.

Schneider, J.F.; Zellmer, S.D.; Tomczyk, N.A.; Rastorier, J.R.; Chen, D.; Banwart, W.L. [Argonne National Lab., IL (United States)

1995-02-01

303

Tree vegetation and waste amendments to improve the physical condition of copper mine soils.  

PubMed

Mine soils are often physically degraded, which hinders plants development. The untreated soils at the depleted copper mine in Touro (Galicia, north-west Spain) have no vegetation and are probably physically degraded. These mine soils were reclaimed both by planting trees and amending with waste (sewage sludge and paper mill residues). The purpose was to determine the effect of these treatments on the physical quality of the soils of the Touro mine under field conditions. We evaluated the physical situation of both the settling pond and the mine tailings in Touro, then comparing them with their respective treated areas: vegetated, amended or with both treatments at the same time. We corroborated that the physical degradation of untreated soils was considerable: low porosity, high density and less than 50% of water stable aggregates. The trees that were planted increased porosity, probably due to root activity. The added amendments increased the mean weight diameter (MWD), the percentage of water stable aggregates (WSA) and the stability index (SI) due to the high organic carbon content in the added wastes. We verified that using both treatments at the same time is better than using only one to improve the physical situation of mine soils. PMID:23026161

Asensio, V; Vega, F A; Andrade, M L; Covelo, E F

2013-01-01

304

Chemical and vegetative stabilization of soils: Laboratory and field investigations of new materials and methods for soil stabilization and erosion control  

Microsoft Academic Search

A survey was conducted on chemical stabilization of soils, and revegetation methods and materials for erosion control. Results of the study indicate that through chemical and vegetative stabilization of disturbed soils, sediment production can be reduced, fertile top soil preserved, and a more environmentally acceptable condition achieved after construction is completed.

W. R. Morrison; L. R. Simmons

1977-01-01

305

A fully traits-based approach to modeling global vegetation distribution  

PubMed Central

Dynamic Global Vegetation Models (DGVMs) are indispensable for our understanding of climate change impacts. The application of traits in DGVMs is increasingly refined. However, a comprehensive analysis of the direct impacts of trait variation on global vegetation distribution does not yet exist. Here, we present such analysis as proof of principle. We run regressions of trait observations for leaf mass per area, stem-specific density, and seed mass from a global database against multiple environmental drivers, making use of findings of global trait convergence. This analysis explained up to 52% of the global variation of traits. Global trait maps, generated by coupling the regression equations to gridded soil and climate maps, showed up to orders of magnitude variation in trait values. Subsequently, nine vegetation types were characterized by the trait combinations that they possess using Gaussian mixture density functions. The trait maps were input to these functions to determine global occurrence probabilities for each vegetation type. We prepared vegetation maps, assuming that the most probable (and thus, most suited) vegetation type at each location will be realized. This fully traits-based vegetation map predicted 42% of the observed vegetation distribution correctly. Our results indicate that a major proportion of the predictive ability of DGVMs with respect to vegetation distribution can be attained by three traits alone if traits like stem-specific density and seed mass are included. We envision that our traits-based approach, our observation-driven trait maps, and our vegetation maps may inspire a new generation of powerful traits-based DGVMs. PMID:25225413

van Bodegom, Peter M.; Douma, Jacob C.; Verheijen, Lieneke M.

2014-01-01

306

Relationship between soil moisture and vegetation in the Kairouan plain region of Tunisia using low spatial resolution satellite data  

E-print Network

Relationship between soil moisture and vegetation in the Kairouan plain region of Tunisia using low containing soil moisture products derived from ERS scatterometer data over the period 1991­2006 and the other region of Tunisia (North Africa). Soil moisture products were first validated on the basis of comparisons

Boyer, Edmond

307

Responses of soil microbial and nematode communities to aluminum toxicity in vegetated oil-shale-waste lands  

E-print Network

Responses of soil microbial and nematode communities to aluminum toxicity in vegetated oil Springer Science+Business Media, LLC 2012 Abstract Both soil nematodes and microorganisms have been shown are poorly understood. We investigated the relationship among soil microbial community composition, nematode

Neher, Deborah A.

308

[Degradation and bioaccumulation characteristics of ciprofloxacin in soil-vegetable system].  

PubMed

A pot experiment was conducted to investigate the effects of applying ciprofloxacin (CIP) on the growth of flowering Chinese cabbage (Brassica campestris), radish (Raphanus sativus), tomato (Solanum lycopersicum) and long bean (Vigna unguiculata), the bioaccumation of CIP in the vegetables, and the degradation of the antibiotics in soil. The results showed that applying 5, 30 and 75 mg x kg(-1) of CIP had no significant effects on the plant biomass of flowering Chinese cabbage, tomato and long bean, but the high concentration of CIP (> or = 30 mg x kg(-1)) inhibited the radish growth significantly. The degradation of CIP in soil was fast at beginning, but slowed down gradually since then. The DT50 and DT90 of CIP in long bean soil were 18.3-43.9 d and 260-738 d, respectively. The CIP could be absorbed by the roots of all the four vegetables and allocated to their aboveground parts, and the CIP residues in the vegetables in creased with the concentration of CIP in soil. The CIP concentration in flowering Chinese cabbage roots was higher than that in the cabbage aboveground parts, that in radish showed a higher concentration in aboveground parts than in roots, and the CIP concentration in tomato and long bean was in the same order of root > stem > leaf. PMID:23359930

Xiao, Qiu-Mei; Wang, Jian-Wu; Tang, Yi-Ling

2012-10-01

309

[Quantitative estimation of vegetation cover and management factor in USLE and RUSLE models by using remote sensing data: a review].  

PubMed

Soil loss prediction models such as universal soil loss equation (USLE) and its revised universal soil loss equation (RUSLE) are the useful tools for risk assessment of soil erosion and planning of soil conservation at regional scale. To make a rational estimation of vegetation cover and management factor, the most important parameters in USLE or RUSLE, is particularly important for the accurate prediction of soil erosion. The traditional estimation based on field survey and measurement is time-consuming, laborious, and costly, and cannot rapidly extract the vegetation cover and management factor at macro-scale. In recent years, the development of remote sensing technology has provided both data and methods for the estimation of vegetation cover and management factor over broad geographic areas. This paper summarized the research findings on the quantitative estimation of vegetation cover and management factor by using remote sensing data, and analyzed the advantages and the disadvantages of various methods, aimed to provide reference for the further research and quantitative estimation of vegetation cover and management factor at large scale. PMID:22937667

Wu, Chang-Guang; Li, Sheng; Ren, Hua-Dong; Yao, Xiao-Hua; Huang, Zi-Jie

2012-06-01

310

The interaction of soil, vegetation and snow - results of a case study in the Central Swiss Alps  

NASA Astrophysics Data System (ADS)

In mountainous areas snow movements can yield enormous erosive forces that are responsible for major soil loss. In this presentation we aim to assess and highlight the importance of snow-gliding as soil erosion agent. Since snow-gliding is dependent of surface roughness, four land use/land cover types in a sub-alpine area in Switzerland were investigated. We used two different approaches to estimate soil erosion rates: the fallout radionuclide 137Cs and the Revised Universal Soil Loss Equation (RUSLE). The RUSLE model is suitable to estimate soil loss by water erosion, while the 137Cs method integrates soil loss due to all erosion agents involved. Thus, we hypothesised that the soil erosion rates determined with the 137Cs method are higher and that the observed discrepancy between the erosion rate of RUSLE and the 137Cs method can be largely explained by snow-gliding. Cumulative snow-glide distance was measured for the sites in the winter 2009/2010 and modelled for the surrounding area with the Spatial Snow Glide Model (SSGM). Measured snow glide distances range from 0 to 189 cm with lower values for the north facing slopes. Further, with increasing surface roughness of the vegetation a reduced snow-glide distance was observed. The latter relationship is of crucial importance in the light of conservation planning and the observed land use changes in the Alps. Our hypothesis was confirmed, as the difference of RUSLE and 137Cs derived erosion rates was correlated to the measured snow-glide distances (R2 = 0.73; p

Mueller, Matthias H.; Meusburger, Katrin; Leitinger, Georg; Mabit, Lionel; Alewell, Christine

2014-05-01

311

Salmonella enterica Serovar Typhimurium and Escherichia coli Contamination of Root and Leaf Vegetables Grown in Soils with Incorporated Bovine Manure  

PubMed Central

Bovine manure, with or without added Salmonella enterica serovar Typhimurium (three strains), was incorporated into silty clay loam (SCL) and loamy sand (LS) soil beds (53- by 114-cm surface area, 17.5 cm deep) and maintained in two controlled-environment chambers. The S. enterica serovar Typhimurium inoculum was 4 to 5 log CFU/g in manure-fertilized soil. The conditions in the two environmental chambers, each containing inoculated and uninoculated beds of manure-fertilized soil, simulated daily average Madison, Wis., weather conditions (hourly temperatures, rainfall, daylight, and humidity) for a 1 March or a 1 June manure application and subsequent vegetable growing seasons ending 9 August or 28 September, respectively. Core soil samples were taken biweekly from both inoculated and uninoculated soil beds in each chamber. Radishes, arugula, and carrots were planted in soil beds, thinned, and harvested. Soils, thinned vegetables, and harvested vegetables were analyzed for S. enterica serovar Typhimurium and Escherichia coli (indigenous in manure). After the 1 March manure application, S. enterica serovar Typhimurium was detected at low levels in both soils on 31 May, but not on vegetables planted 1 May and harvested 12 July from either soil. After the 1 June manure application, S. enterica serovar Typhimurium was detected in SCL soil on 7 September and on radishes and arugula planted in SCL soil on 15 August and harvested on 27 September. In LS soil, S. enterica serovar Typhimurium died at a similar rate (P ? 0.05) after the 1 June manure application and was less often detected on arugula and radishes harvested from this soil compared to the SCL soil. Pathogen levels on vegetables were decreased by washing. Manure application in cool (daily average maximum temperature of <10°C) spring conditions is recommended to ensure that harvested vegetables are not contaminated with S. enterica serovar Typhimurium. Manure application under warmer (daily average maximum temperature >20°C) summer conditions is not recommended when vegetable planting is done between the time of manure application and late summer. A late fall manure application will not increase the risk of contaminating vegetables planted the next spring, since further experiments showed that repeated freeze-thaw cycles were detrimental to the survival of S. enterica serovar Typhimurium and E. coli in manure-fertilized soil. The number of indigenous E. coli in soil was never significantly lower (P < 0.05) than that of S. enterica serovar Typhimurium, suggesting its usefulness as an indicator organism for evaluating the risk of vegetable contamination with manure-borne S. enterica serovar Typhimurium. PMID:12039728

Natvig, Erin E.; Ingham, Steven C.; Ingham, Barbara H.; Cooperband, Leslie R.; Roper, Teryl R.

2002-01-01

312

Salmonella enterica serovar Typhimurium and Escherichia coli contamination of root and leaf vegetables grown in soils with incorporated bovine manure.  

PubMed

Bovine manure, with or without added Salmonella enterica serovar Typhimurium (three strains), was incorporated into silty clay loam (SCL) and loamy sand (LS) soil beds (53- by 114-cm surface area, 17.5 cm deep) and maintained in two controlled-environment chambers. The S. enterica serovar Typhimurium inoculum was 4 to 5 log CFU/g in manure-fertilized soil. The conditions in the two environmental chambers, each containing inoculated and uninoculated beds of manure-fertilized soil, simulated daily average Madison, Wis., weather conditions (hourly temperatures, rainfall, daylight, and humidity) for a 1 March or a 1 June manure application and subsequent vegetable growing seasons ending 9 August or 28 September, respectively. Core soil samples were taken biweekly from both inoculated and uninoculated soil beds in each chamber. Radishes, arugula, and carrots were planted in soil beds, thinned, and harvested. Soils, thinned vegetables, and harvested vegetables were analyzed for S. enterica serovar Typhimurium and Escherichia coli (indigenous in manure). After the 1 March manure application, S. enterica serovar Typhimurium was detected at low levels in both soils on 31 May, but not on vegetables planted 1 May and harvested 12 July from either soil. After the 1 June manure application, S. enterica serovar Typhimurium was detected in SCL soil on 7 September and on radishes and arugula planted in SCL soil on 15 August and harvested on 27 September. In LS soil, S. enterica serovar Typhimurium died at a similar rate (P >or= 0.05) after the 1 June manure application and was less often detected on arugula and radishes harvested from this soil compared to the SCL soil. Pathogen levels on vegetables were decreased by washing. Manure application in cool (daily average maximum temperature of <10 degrees C) spring conditions is recommended to ensure that harvested vegetables are not contaminated with S. enterica serovar Typhimurium. Manure application under warmer (daily average maximum temperature >20 degrees C) summer conditions is not recommended when vegetable planting is done between the time of manure application and late summer. A late fall manure application will not increase the risk of contaminating vegetables planted the next spring, since further experiments showed that repeated freeze-thaw cycles were detrimental to the survival of S. enterica serovar Typhimurium and E. coli in manure-fertilized soil. The number of indigenous E. coli in soil was never significantly lower (P < 0.05) than that of S. enterica serovar Typhimurium, suggesting its usefulness as an indicator organism for evaluating the risk of vegetable contamination with manure-borne S. enterica serovar Typhimurium. PMID:12039728

Natvig, Erin E; Ingham, Steven C; Ingham, Barbara H; Cooperband, Leslie R; Roper, Teryl R

2002-06-01

313

A model of the coupled dynamics of climate, vegetation and terrestrial ecosystem biogeochemistry for regional applications  

NASA Astrophysics Data System (ADS)

Regional climate models (RCMs) primarily represent physical components of the climate system, omitting vegetation dynamics, ecosystem biogeochemistry and their associated feedbacks. To account for such feedbacks, we implemented a novel plant individual-based vegetation dynamics-ecosystem biogeochemistry scheme within the RCA3 RCM. Variations in leaf area index (LAI) of seven plant functional type (PFTs) in response to physical forcing and evolving vegetation state feed back to climate via adjustments in surface energy fluxes and surface properties. In an ERA-40-driven simulation over Europe, the model reproduces the recent past climate with comparable accuracy to the standard RCM. Large-scale patterns of LAI, net primary production and vegetation composition were comparable with observations, although winter LAI was systematically overestimated compared to satellite estimates. Analysis of the ERA-40 simulation and an A1B climate-change simulation revealed considerable covariation among dynamic variables of the physical climate and vegetation. At a Mediterranean site, periodic soil water limitation led to fluctuations in leaf cover and a likely positive feedback to near-surface temperature. At an alpine site, rising temperatures led to forest advance onto tundra areas, reducing albedo and effecting a likely positive feedback on temperature. Climate-vegetation coupling was less pronounced but still apparent at intermediate temperate and boreal sites.

Smith, Benjamin; Samuelsson, Patrick; Wramneby, Anna; Rummukainen, Markku

2011-01-01

314

Infiltration and soil erosion modelling on Lausatian post mine sites  

NASA Astrophysics Data System (ADS)

Land management of reclaimed lignite mine sites requires long-term and safe structuring of recultivation areas. Erosion by water leads to explicit soil losses, especially on heavily endangered water repellent and non-vegetated soil surfaces. Beyond that, weathering of pyrite-containing lignite burden dumps causes sulfuric acid-formation, and hence the acidification of groundwater, seepage water and surface waters. Pyrite containing sediment is detached by precipitation and transported into worked-out open cuts by draining runoff. In addition to ground water influence, erosion processes are therefore involved in acidification of surface waters. A model-based approach for the conservation of man-made slopes of post mining sites is the objective of this ongoing study. The study shall be completed by modeling of the effectiveness of different mine site recultivation scenarios. Erosion risks on man-made slopes in recultivation areas should be determined by applying the physical, raster- and event based computer model EROSION 2D/3D (Schmidt, 1991, 1992; v. Werner, 1995). The widely used erosion model is able to predict runoff as well as detachment, transport and deposition of sediments. Lignite burden dumps contain hydrophobic substances that cover soil particles. Consequently, these soils show strong water repellency, which influences the processes of infiltration and soil erosion on non-vegetated, coal containing dump soils. The influence of water repellency had to be implemented into EROSION 2D/3D. Required input data for soil erosion modelling (e.g. physical soil parameters, infiltration rates, calibration factors, etc.) were gained by soil sampling and rainfall experiments on non-vegetated as well as recultivated reclaimed mine sites in the Lusatia lignite mining region (southeast of Berlin, Germany). The measured infiltration rates on the non-vegetated water repellent sites were extremely low. Therefore, a newly developed water repellency-factor was applied to depict infiltration and erosion processes on water repellent dump soils. For infiltration modelling with EROSION 2D calibration factors (e.g. water repellency factor, skin-factor, etc.) were determined in different steps by calibrating computer modelled infiltration, respectively volume rate of flow to the measured data.

Kunth, Franziska; Schmidt, Jürgen

2013-04-01

315

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

SciTech Connect

This study examines the uptake of explosives by vegetation growing on soils contaminated by 2,4,6-trinitrotoluene (TNT) in Group 61 at the Joliet Army Ammunition Plant (JAAP). Plant materials and soil from the root zone were sampled and analyzed to determine TNT uptake under natural field conditions. Standard USATHAMA methods were used to determine concentrations of explosives, their derivatives, and metabolites in the soil samples. No- explosives were detected in the aboveground portion of any plant sample. However, results indicate that TNT, 2-aminodinitrotoluene (2-ADNT), and/or 4-ADNT were present in some root samples. The presence of 2-ADNT and 4-ADNT increases the likelihood that explosives were taken up by plant roots, as opposed to their presence resulting from external soil contamination.

Schneider, J.F.; Tomczyk, N.A.; Zellmer, S.D. [Argonne National Lab., IL (United States); Banwart, W.L. [University of Illinois, Champaign-Urbana, IL (United States). Agronomy Dept.; Houser, W.P. [US Army Environmental Center, Edgewood, MD (United States)

1994-06-01

316

Environmental factors influencing soil testate amoebae in herbaceous and shrubby vegetation along an altitudinal gradient in subarctic tundra (Abisko, Sweden).  

PubMed

Shifts in community composition of soil protozoa in response to climate change may substantially influence microbial activity and thereby decomposition processes. However, effects of climate and vegetation on soil protozoa remain poorly understood. We studied the distribution of soil testate amoebae in herbaceous and shrubby vegetation along an altitudinal gradient (from below the treeline at 500 m to the mid-alpine region at 900 m a.s.l.) in subarctic tundra. To explain patterns in abundance, species diversity and assemblage composition of testate amoebae, a data set of microclimate and soil chemical characteristics was collected. Both elevation and vegetation influenced the assemblage composition of testate amoebae. The variation was regulated by interactive effects of summer soil moisture, winter soil temperature, soil pH and nitrate ion concentrations. Besides, soil moisture regulated non-linear patterns in species richness across the gradient. This is the first study showing the effects of winter soil temperatures on species composition of soil protozoa. The effects could be explained by specific adaptations of testate amoebae such as frost-resistant cysts allowing them to survive low winter temperatures. We conclude that the microclimate and soil chemical characteristics are the main drivers of changes in protozoan assemblage composition in response to elevation and vegetation. PMID:23022310

Tsyganov, Andrey N; Milbau, Ann; Beyens, Louis

2013-05-01

317

Modeling vegetation reflectance from satellite remote sensing data  

NASA Astrophysics Data System (ADS)

The development of better techniques for land vegetation cover and forest ecosystems monitoring is a major requirement for local, regional and global policy and global change science. The influence of climatic variability and anthropogenic activities on the condition of the vegetation (agricultural fields, forests, sparse) is growing up continuously. In order to characterize current and future state of vegetation and localize zones of changes must be defined the proper criteria. Vegetation land cover monitoring by satellite remote sensing data is one of the most important application of satellite imagery. Vegetation reflectance has variations with sun zenith angle, view zenith angle, and terrain slope angle. To better providing of this these effects corrections in the visible and near-infrared region of electromagnetic spectrum, was used a three parameters model and was developed a simple physical model of vegetation reflectance, by assuming a homogeneous and closed vegetation canopy with randomly oriented leaves. Multiple scattering theory was used to extend the model to function for both near-infrared and visible light. This paper aims to improve the model to be used to correct satellite imagery for bidirectional and topographic effects. Thresholding based on biophysical variables derived from time trajectories of satellite data was applied for classifying using Landsat TM and ETM, SAR ERS-1 imagery for Cernica forested area in the Eastern part of Bucharest town, Romania. Classification accuracies are function of the class, comparison method and season of the year.

Zoran, Maria

2007-08-01

318

Impact of the December 2004 tsunami on soil, groundwater and vegetation in the Nagapattinam District, India.  

PubMed

The tsunami of 26 December 2004 struck the Nagapattinam District, Tamil Nadu, India. Sea water inundation from the tsunami caused salinization problems for soil and groundwater in coastal areas of the district, and also induced salt injuries in crops. To document the recovery of the agricultural environment from the tsunami, we conducted observations of the soil, groundwater, and vegetation. Soil electrical conductivity increased sharply after the tsunami, but returned to pre-tsunami levels the following year. Groundwater salinity returned to pre-tsunami levels by 2006. These rapid rates of recovery were due to the monsoon rainfall leaching salt from the highly permeable soils in the area. MODIS NDVI values measured before and after the tsunami showed that vegetation damaged by the tsunami recovered to its pre-tsunami state by the next rice cropping season, called samba, which starts from August to February. From these results, we conclude that the agricultural environment of the district has now fully recovered from the tsunami. Based on the results, we have also identified important management implications for soil, groundwater, and vegetation as follows: 1) due to the heavy monsoon rainfall and the high permeability of soils in this region, anthropogenic inputs like fertilizers should be applied carefully to minimize pollution, and the use of green manure is recommended; 2) areas that were contaminated by sea water extended up to 1000 m from the sea shore and over pumping of groundwater should be carefully avoided to prevent inducing sea water intrusion; and 3) data from a moderate resolution sensor of 250 m, such as MODIS, can be applied to impact assessment in widespread paddy field areas like the Nagapattinam District. PMID:19540650

Kume, Takashi; Umetsu, Chieko; Palanisami, K

2009-07-01

319

The effects of vegetation and soil hydraulic properties on passive microwave sensing of soil moisture: Data report for the 1982 fiels experiments  

NASA Technical Reports Server (NTRS)

Field experiments to (1) study the biomass and geometrical structure properties of vegetation canopies to determine their impact on microwave emission data, and (2) to verify whether time series microwave data can be related to soil hydrologic properties for use in soil type classification. Truck mounted radiometers at 1.4 GHz and 5 GHz were used to obtain microwave brightness temperatures of bare vegetated test plots under different conditions of soil wetness, plant water content and canopy structure. Observations of soil moisture, soil temperature, vegetation biomass and other soil and canopy parameters were made concurrently with the microwave measurements. The experimental design and data collection procedures for both experiments are documented and the reduced data are presented in tabular form.

Oneill, P.; Jackson, T.; Blanchard, B. J.; Vandenhoek, R.; Gould, W.; Wang, J.; Glazar, W.; Mcmurtrey, J., III

1983-01-01

320

Changes in soils and vegetation in a Mediterranean coastal salt marsh impacted by human activities  

NASA Astrophysics Data System (ADS)

This paper reports changes in vegetation distribution and species cover in relation to soil factors and hydrology in a semiarid Mediterranean salt marsh adjacent to the Mar Menor saline lagoon. Species cover, soil salinity, and the groundwater level were monitored between 1991 and 1993 and between 2002 and 2004, and total organic carbon, total nitrogen, total phosphorus, nitrates, ammonium and exchangeable phosphorus were measured in the soils in both study periods. In addition, three soil profiles were described in August 1992 and August 2004. The results indicate an elevation of the water table throughout the 13-year period, which was attributable to water flowing from areas with intensive agriculture. Flooding increased and soil salinity dropped in the most saline sites and increased in the least saline ones. The morphology of the soil profiles reflected the increase in flooding periods, due to the appearance of a greyer matrix in the deeper horizons and a more diffuse pattern of Fe mottles. Following these environmental changes, Sarcocornia fruticosa, Phragmites australis and Juncus maritimus strongly expanded at the wettest sites, which led to the disappearance of the original zonation pattern. The cover of Limonium delicatulum, in turn, decreased with the increase in moisture but increased following the increase in salinity. Changes in soil nutrients were only very evident in the sandy soils of the beach, probably due to the influence of organic debris deposited on the shoreline by the storms and due to the strong increase in the colonisation of this habitat by perennial species. According to the results obtained, control measures are needed in order to preserve habitat diversity in this and other salt marshes of this area. Monitoring of the vegetation distribution could be a useful tool to identify environmental impacts, in order to implement remedial actions.

Álvarez-Rogel, J.; Jiménez-Cárceles, F. J.; Roca, M. J.; Ortiz, R.

2007-07-01

321

Measurement of directional thermal infrared emissivity of vegetation and soils  

SciTech Connect

A new method has been developed for measuring directional thermal emissivity as a function of view angle for plant canopies and soils using two infrared thermometers each sensitive to a different wavelength band. By calibrating the two infrared thermometers to 0.1C consistency, canopy directional emissivity can be estimated with typical errors less than 0.005 in the 8--14 um wavelength band, depending on clarity of the sky and corrections for CO{sub 2} absorption by the atmosphere. A theoretical justification for the method is developed along with an error analysis. Laboratory measurements were used to develop corrections for CO{sub 2}, absorption and a field calibration method is used to obtain the necessary 0.1C consistency for relatively low cost infrared thermometers. The emissivity of alfalfa (LAI=2.5) and corn (LAI=3.2) was near 0.995 and independent of view angle. Individual corn leaves had an emissivity of 0.97. A wheat (LAI=3.0) canopy had an emissivity of 0.985 at nadir and 0.975 at 75 degree view angle. The canopy emissivity values tend to be higher than values in the literature, and are useful for converting infrared thermometer measurements to kinetic temperature and interpreting satellite thermal observations.

Norman, J.M. [Wisconsin Univ., Madison, WI (United States). Dept. of Soil Science; Balick, L.K. [EG and G Energy Measurements, Inc., Las Vegas, NV (United States)

1995-10-01

322

Effects of Model Resolution on Predictions of Vegetation Health in Water-Limited Ecosystems  

NASA Astrophysics Data System (ADS)

Water-limited ecosystems are characterized by precipitation with low annual totals and significant temporal variability, transpiration that is limited by soil-moisture availability rather than atmospheric demand, and infiltration events that may only partially rewet the vegetation root zone. Average transpiration in such environments is controlled by precipitation, and accurate predictions of vegetation health require an adequate representation of the temporal variation in the timing and intensity of plant uptake. Complexities introduced by variability in depth of infiltration, distribution of roots, and a plant's ability to compensate for spatially heterogeneous soil moisture suggest a minimum vertical resolution required for a satisfactory representation of plant behavior. To explore the effect of model resolution on predictions of vegetation health, we conduct a series of numerical experiments, comparing the results from models of varying resolution for a range of plant and climate conditions. Plant uptake is represented with a Type I model, in which flow through the soil-atmosphere-plant continuum is driven by a potential difference across a network of resistances. To isolate the effects of spatial variations in soil-moisture and uptake, infiltration is simplified to occur instantaneously in response to intermittent storms arriving as a Poisson process. From temporal and spatial scales of the underlying processes and desired output, we develop a dimensionless parameter that indicates the adequacy of a finite-resolution model with respect to reproducing characteristics of plant transpiration over multiple growing seasons. This parameter may be used to determine the spatial resolution required to predict vegetation health in water-limited ecosystems accurately.

Guswa, A. J.; Celia, M. A.; Rodriguez-Iturbe, I.

2003-12-01

323

Transfer of radioactivity from soil to vegetation in Rechna Doab, Pakistan  

Microsoft Academic Search

In Rechna Doab, samples of the most common vegetation, perennial grass Desmostachya bipinnata (dab), were collected along with soil samples from 29 sites. Natural radioactivity of Ra, Th\\/Ac and K was measured by using high purity germanium-based gamma ray spectrometer. Activity concentration levels of Ra, Th\\/Ac and K in soil were found to be 46.8±6.2 (36.0–57.6), 61.4±5.9 (48.2–73.2) and 644.8±73.9

Abdul Jabbar; Muhammad Tufail; Waheed Arshed; Arshed Salem Bhatti; Syed Salman Ahmad; Perveen Akhter; Muhammad Dilband

2010-01-01

324

[Soil respiration dynamics and its controlling factors of typical vegetation communities on meadow steppes in the western Songnen Plain].  

PubMed

In order to accurately explore the soil respiration dynamics and its controlling factors of typical vegetation types in the western Songnen Plain, soil respiration rates of Chloris virgata, Puccinellia distans, Phragmites australis and Leymus chinensis communities were measured. The results showed that the diurnal curves of soil respiration rates of the four vegetation communities had simple peak values, which appeared at 11:00-15:00, and the valley values occurred at 21:00-1:00 or 3:00-5:00. The seasonal dynamic patterns of their soil respiration rates were similar, with the maximum (3.21-4.84 micromol CO2 x m(-2) x s(-1)) occurring in July and August and the minimum (0.46-1.51 micromol CO2 x m(-2) x s(-1)) in October. The soil respiration rates of the four vegetation communities had significant exponential correlations with ambient air temperature and soil temperature. Soil moisture, however, only played an important role in affecting the soil respiration rate of C. virgata community while air humidity near the soil surface was significantly correlated with the soil respiration rates of P. australis and L. chinensis communities. The soil salt contents seriously constrained the CO2 dioxide emission, and the soil pH, electrical conductivity (EC), exchangeable sodium percentage (ESP) could explain 87%-91% spatial variations of the soil respiration rate. PMID:24765841

Wang, Ming; Liu, Xing-Tu; Li, Xiu-Jun; Zhang, Ji-Tao; Wang, Guo-Dong; Lu, Xin-Rui; Li, Xiao-Yu

2014-01-01

325

Accounting for spatial variation in vegetation properties improves simulations of Amazon forest biomass and productivity in a global vegetation model  

NASA Astrophysics Data System (ADS)

Dynamic vegetation models forced with spatially homogeneous biophysical parameters are capable of producing average productivity and biomass values for the Amazon basin forest biome that are close to the observed estimates, but are unable to reproduce the observed spatial variability. Recent observational studies have shown substantial regional spatial variability of above-ground productivity and biomass across the Amazon basin, which is believed to be primarily driven by soil physical and chemical properties. In this study, spatial heterogeneity of vegetation properties is added to the IBIS land surface model, and the simulated productivity and biomass of the Amazon basin are compared to observations from undisturbed forest. The maximum Rubisco carboxylation capacity (Vcmax) and the woody biomass residence time (?w) were found to be the most important properties determining the modeled spatial variation of above-ground woody net primary productivity and biomass, respectively. Spatial heterogeneity of these properties may lead to a spatial variability of 1.8 times in the simulated woody net primary productivity and 2.8 times in the woody above-ground biomass. The coefficient of correlation between the modeled and observed woody productivity improved from 0.10 with homogeneous parameters to 0.73 with spatially heterogeneous parameters, while the coefficient of correlation between the simulated and observed woody above-ground biomass improved from 0.33 to 0.88. The results from our analyses with the IBIS dynamic vegetation model demonstrate that using single values for key ecological parameters in the tropical forest biome severely limits simulation accuracy. We emphasize that our approach must be viewed as an important first step and that a clearer understanding of the biophysical mechanisms that drive the spatial variability of carbon allocation, ?w and Vcmax are necessary.

de Almeida Castanho, A. D.; Coe, M. T.; Heil Costa, M.; Malhi, Y.; Galbraith, D.; Quesada, C. A.

2012-08-01

326

The applicability of ERTS-1 data covering the major landforms of Kenya. [landforms, vegetation, soils, forests  

NASA Technical Reports Server (NTRS)

The author has identified the following significant results. Five investigators report on the applicability of ERTS-1 data covering the major landforms of Kenya. Deficiencies due to lack of equipment, repetitive coverage and interpretation know-how are also reported on. Revision of lake shorelines is an immediate benefit. Basement system metasediments are rapidly differentiated, but dune areas are not readily distinguishable from sandy soils. Forest, moorland, high altitude grass, tea, and conifer plantations are readily distinguished, with podocarpus forest especially distinguishable from podocarpus/juniperus forest. In the arid areas physiographic features, indicating the major soil types, are readily identified and mapped. Preliminary vegetation type analysis in the Mara Game Reserve indicates that in a typical savannah area about 36% of the vegetation types are distinguishable at a scale of 1:1 million as well as drainage patterns and terrain features.

Omino, J. H. O. (principal investigator)

1973-01-01

327

Contents of minerals in green leafy vegetables cultivated in soil fortified with different chemical fertilizers.  

PubMed

Content of selected minerals in spinach (Spinacea oleracea) and ambat chuka (Rumex vesicarius) cultivated in soil fortified with different chemical fertilizers was determined in a pot experiment. Addition of NPK (Nitrogen, Phosphorus and Potassium) fertilizer along with micronutrients, iron and zinc, enhanced the concentration of zinc, iron and magnesium in selected green leafy vegetables markedly (p < 0.05), while the concentration of copper was not altered significantly (p > 0.05). Potassium content in the green leafy vegetables was not affected (p > 0.05) by the addition of chemical fertilizers to soil. Spinach and ambat chuka differed remarkably in their mineral contents. Contents of potassium, zinc and copper were significantly high in spinach, while the contents of magnesium and iron were markedly high in ambat chuka (p < 0.05). PMID:11213164

Reddy, N S; Bhatt, G

2001-01-01

328

Patterns of soil moisture and vegetation in constructed wetlands  

NASA Astrophysics Data System (ADS)

Early results from a new simple model for the study of eco-hydrological patterns in constructed wetland are presented. The model may simulate the case that a dominant plant tends to colonize neighbouring zones to the detriment of the other species, or that synergies between different species allow their survival under water or oxygen stress. Tasks such as of zonation and controlling invasive plants spreading by regulating water table depth and inundation timing are discussed on the base of the outcome of few numerical modelling exercises.

Ursino, N.

2009-04-01

329

Ultramafic Rocks: Their Soils, Vegetation and Fauna Rocas Ultramficas: Sus Suelos, Vegetacin y Fauna  

E-print Network

Ultramafic Rocks: Their Soils, Vegetation and Fauna Rocas Ultramáficas: Sus Suelos, Vegetación y Caledonia y los Estados Unidos. El volumen incluye artículos sobre los temas siguientes: · Geología y suelos, · Flora, fitogeografía y vegetación de Cuba y otras regiones, · Microbiología de suelos ultramáficos

Boyd, Robert S.

330

Radiological conditions at Bikini Atoll: Radionuclide concentrations in vegetation, soil, animals, cistern water, and ground water  

Microsoft Academic Search

This report is intended as a resource document for the eventual cleanup of Bikini Atoll and contains a summary of the data for the concentrations of ¹³⁷Cs, ⁹°Sr, \\/sup 239 +240\\/Pu, and ²⁴¹Am in vegetation through 1987 and in soil through 1985 for 14 islands at Bikini Atoll. The data for the main residence island, Bikini, and the most important

W. L. Robison; C. L. Conrado; M. L. Stuart

1988-01-01

331

Evaluation of vegetative cover on reclaimed land by color infrared videography relative to soil properties  

E-print Network

as to style and content by: (Chairman) L, k. ~ J gp, Q~~ L. R. Hossner (Member) R. C. Maggio (Member) E. C. A. Rung (Head of Department) August 1988 ABSTRACT Evaluation of Vegetative Cover on Reclaimed Land by Color Infrared Videography Relative... formation which is Eocene in age. These sandy, silty clay and clayey sediments were derived from an ancient coastal river system representing both fresh and marine water environments (Hall Southwest Water Consultants, Inc. , 1982). A soil survey...

Pfordresher, Anne Augusta

2012-06-07

332

Speciation studies of tetraalkylleads and inorganic Pb in polluted roadside vegetation and soil samples  

Microsoft Academic Search

The Gas chromatography?atomic absorption spectrophotometric method has been used for the determination of tetraalkylleads in polluted roadside vegetation and soil samples. The method, which required very little sample preparation, gave precisions of 8.3% (TML) and 22% (TEL), which are adjudged acceptable. The detection limits (16.3–43.6 pg, Pb) for the alkylleads are sufficiently low for pollution monitoring applications.Results are presented for

O. S. Fatoki; S. J. Hill

1994-01-01

333

Lead contamination and its potential sources in vegetables and soils of Fujian, China  

Microsoft Academic Search

Lead (Pb) contents and partition in soils collected from eleven vegetable-growing lands in Fujian Province, China, were investigated\\u000a using a modification of the BCR (Community Bureau of Reference) sequential extraction procedure coupled with the Pb isotope\\u000a ratio technique. Pb contents in Chinese white cabbage (B. Chinensis L.) grown on the lands for this study were also measured. Results showed that

Zhi-Yong HuangTing; Ting Chen; Jiang Yu; De-Ping Qin; Lan Chen

334

Radionuclide concentrations in terrestrial vegetation and soil on and around the Hanford Site, 1983 through 1993  

Microsoft Academic Search

This report reviews concentrations of ⁶°Co, ⁹°Sr, ¹³⁷Cs, U isotopes, ²³⁸Pu, {sup 239,240}Pu, and ²⁴¹Am in soil and vegetation samples collected from 1983 through 1993 during routine surveillance of the Hanford Site. Sampling locations were grouped in study areas associated with operational areas on the Site. While radionuclide concentrations were very low and representative of background concentrations from historic fallout,

T. M. Poston; E. J. Antonio; A. T. Cooper

1995-01-01

335

Edge effects on vegetation and soils in a Virginia old-field  

Microsoft Academic Search

We investigated the effect of proximity to forest edge on plant community structure and ecosystem properties during succession, using field measurements of leaf area index (LAI), species composition, and soil carbon. Data were collected along four transects within a 14-year-old temperate successional field in north-central Virginia over the 2000 growing season. Additionally, the normalized difference vegetation index (NDVI) was calculated

Sebastian M. Riedel; Howard E. Epstein

2005-01-01

336

How sedge meadow soils, microtopography, and vegetation respond to sedimentation  

USGS Publications Warehouse

The expansion of urban and agricultural activities in watersheds of the Midwestern USA facilitates the conversion of species-rich sedge meadows to stands of Phalaris arundinacea and Typha spp. We document the role of sediment accumulation in this process based on field surveys of three sedge meadows dominated by Carex stricta, their adjacent Phalaris or Typha stands, and transitions from Carex to these invasive species. The complex microtopography of Carex tussocks facilitates the occurrence of other native species. Tussock surface area and species richness were positively correlated in two marshes (r2 = 0.57 and 0.41); on average, a 33-cm-tall tussock supported 7.6 species. Phalaris also grew in tussock form in wetter areas but did not support native species. We found an average of 10.5 Carex tussocks per 10-m transect, but only 3.5 Phalaris tussocks. Microtopographic relief, determined with a high-precision GPS, measured 11% greater in Carex meadows than Phalaris stands. Inflowing sediments reduced microtopographic variation and surface area for native species. We calculated a loss of one species per 1000 cm2 of lost tussock surface area, and loss of 1.2 species for every 10-cm addition of sediment over the sedge meadow surface. Alluvium overlying the sedge meadow soil had a smaller proportion of organic matter content and higher dry bulk density than the buried histic materials. We conclude that sedimentation contributes to the loss of native species in remnant wetlands. ?? 2002, The Society of Wetland Scientists.

Werner, K.J.; Zedler, J.B.

2002-01-01

337

Effects of Spatial Heterogeneity in Rainfall and Vegetation on the Space-Time Scaling of Soil-Moisture and Evapotranspiration  

NASA Astrophysics Data System (ADS)

The effects of spatial heterogeneity in rainfall and vegetation on the space-time scaling behavior of hydrologic variables controlling the water balance are outstanding issues in land-surface modeling. An important aspect of these effects is the variability of specified hydrologic variables and their relationships with scales characteristic of land-surface heterogeneity and a model's resolution. In this work, we focus on the spatial and temporal scaling properties of soil moisture and evapotranspiration for various types of rainfall and vegetation heterogeneity in a Texas water-limited ecosystem. A detailed model simulates stochastic rainfall in space and time for multiple realizations to compute daily values of these variables over a range of spatial and temporal averaging windows. Results of our simulations indicate that the spatial variance of soil moisture and evapotranspiration decrease with increasing averaging area such that spatial threshold scales, or representative averaging areas, can be identified. Spatial threshold scales have been used in the literature to infer the importance of modeling land-surface heterogeneity explicitly. The results are generalized by relating the spatial threshold scales to a dimensionless group of parameters that includes length scales characteristic of the heterogeneity and the model's resolution. In the time domain, we compute the temporal variance over multiple realizations for different temporal averaging windows. This computation enables prediction of a temporal threshold scale, which indicates the amount of time necessary to predict accurately the mean of the variables. The space-time scaling behavior is then explored and results demonstrate that the spatial and temporal threshold scales are interdependent. These space-time results provide valuable insight into sampling and resolution issues for field and modeling studies of soil moisture and evapotranspiration.

Puma, M. J.; Rodriguez-Iturbe, I.; Celia, M. A.; Nordbotten, J. M.; Guswa, A. J.

2005-12-01

338

Lead and cadmium in soils and vegetables from urban gardens of Salamanca (Spain).  

PubMed

The Pb and Cd contents of soils and vegetables from 16 urban gardens of Salamanca (Spain) have been determined. The metals were found to occur at concentrations in the ranges 20.1-96.2 and 0.20-0.95 microgram/g for Pb and Cd, respectively. The mean Pb concentration found was 2.60 times higher than that in natural soils of the Salamanca province, whereas that of Cd exceeded its mean concentration in natural and cultivated soils by a factor of 2.73 and 2.04, respectively. The Pb and Cd contents of the vegetables (branches) ranged between 4.17 and The Pb and Cd contents of the vegetables (branches) ranged between 4.17 and 52.7 micrograms/g, and between 0.35 and 3.05 micrograms/g, respectively. According to these results, Pb and Cd occur at pollution levels in the surveyed gardens. The total and soluble Pb (extractable with 1 N ammonium acetate) levels were found to be related to the traffic density. On the other hand, the Cd levels appear to be more closely related to the distance from roadways, as well as to the age of the garden and the flow of visitors. PMID:8016634

Sánchez-Camazano, M; Sánchez-Martín, M J; Lorenzo, L F

1994-05-23

339

Soil and vegetation carbon stocks in Brazilian Western Amazonia: relationships and ecological implications for natural landscapes.  

PubMed

The relationships between soils attributes, soil carbon stocks and vegetation carbon stocks are poorly know in Amazonia, even at regional scale. In this paper, we used the large and reliable soil database from Western Amazonia obtained from the RADAMBRASIL project and recent estimates of vegetation biomass to investigate some environmental relationships, quantifying C stocks of intact ecosystem in Western Amazonia. The results allowed separating the western Amazonia into 6 sectors, called pedo-zones: Roraima, Rio Negro Basin, Tertiary Plateaux of the Amazon, Javari-Juruá-Purus lowland, Acre Basin and Rondonia uplands. The highest C stock for the whole soil is observed in the Acre and in the Rio Negro sectors. In the former, this is due to the high nutrient status and high clay activity, whereas in the latter, it is attributed to a downward carbon movement attributed to widespread podzolization and arenization, forming spodic horizons. The youthful nature of shallow soils of the Javari-Juruá-Purus lowlands, associated with high Al, results in a high phytomass C/soil C ratio. A similar trend was observed for the shallow soils from the Roraima and Rondonia highlands. A consistent east-west decline in biomass carbon in the Rio Negro Basin sector is associated with increasing rainfall and higher sand amounts. It is related to lesser C protection and greater C loss of sandy soils, subjected to active chemical leaching and widespread podzolization. Also, these soils possess lower cation exchangeable capacity and lower water retention capacity. Zones where deeply weathered Latosols dominate have a overall pattern of high C sequestration, and greater than the shallower soils from the upper Amazon, west of Madeira and Negro rivers. This was attributed to deeper incorporation of carbon in these clayey and highly pedo-bioturbated soils. The results highlight the urgent need for refining soil data at an appropriate scale for C stocks calculations purposes in Amazonia. There is a risk of misinterpreting C stocks in Amazonia when such great pedological variability is not taken into account. PMID:17846909

Schaefer, C E G R; do Amaral, E F; de Mendonça, B A F; Oliveira, H; Lani, J L; Costa, L M; Fernandes Filho, E I

2008-05-01

340

Gravel admix, vegetation, and soil water interactions in protective barriers: Experimental design, construction, and initial conditions  

SciTech Connect

The purpose of this study is to measure the interactive effects of gravel admix and greater precipitation on soil water storage and plant abundance. The study is one of many tasks in the Protective Barrier Development Program for the disposal of Hanford defense waste. A factorial field-plot experiment was set up at the site selected as the borrow area for barrier topsoil. Gravel admix, vegetation, and enhanced precipitation treatments were randomly assigned to the plots using a split-split plot design structure. Changes in soil water storage and plant cover were monitored using neutron probe and point intercept methods, respectively. The first-year results suggest that water extraction by plants will offset gravel-caused increases in soil water storage. Near-surface soil water contents were much lower in graveled plots with plants than in nongraveled plots without plants. Large inherent variability in deep soil water storage masked any effects gravel may have had on water content below the root zone. In the future, this source of variation will be removed by differencing monthly data series and testing for changes in soil water storage. Tests of the effects of greater precipitation on soil water storage were inconclusive. A telling test will be possible in the spring of 1988, following the first wet season during which normal precipitation is doubled. 26 refs., 9 figs., 9 tabs.

Waugh, W.J.

1989-05-01

341

Modeling the Interactions Between River Morphodynamics and Riparian Vegetation  

NASA Astrophysics Data System (ADS)

The study of river-riparian vegetation interactions is an important and intriguing research field in geophysics. Vegetation is an active element of the ecological dynamics of a floodplain which interacts with the fluvial processes and affects the flow field, sediment transport, and the morphology of the river. In turn, the river provides water, sediments, nutrients, and seeds to the nearby riparian vegetation, depending on the hydrological, hydraulic, and geomorphological characteristic of the stream. In the past, the study of this complex theme was approached in two different ways. On the one hand, the subject was faced from a mainly qualitative point of view by ecologists and biogeographers. Riparian vegetation dynamics and its spatial patterns have been described and demonstrated in detail, and the key role of several fluvial processes has been shown, but no mathematical models have been proposed. On the other hand, the quantitative approach to fluvial processes, which is typical of engineers, has led to the development of several morphodynamic models. However, the biological aspect has usually been neglected, and vegetation has only been considered as a static element. In recent years, different scientific communities (ranging from ecologists to biogeographers and from geomorphologists to hydrologists and fluvial engineers) have begun to collaborate and have proposed both semiquantitative and quantitative models of river-vegetation interconnections. These models demonstrate the importance of linking fluvial morphodynamics and riparian vegetation dynamics to understand the key processes that regulate a riparian environment in order to foresee the impact of anthropogenic actions and to carefully manage and rehabilitate riparian areas. In the first part of this work, we review the main interactions between rivers and riparian vegetation, and their possible modeling. In the second part, we discuss the semiquantitative and quantitative models which have been proposed to date, considering both multi- and single-thread rivers.

Camporeale, C.; Perucca, E.; Ridolfi, L.; Gurnell, A. M.

2013-09-01

342

Soil Trace Gas Flux for Wetland Vegetation Zones in North Dakota Prairie Pothole Basins  

NASA Astrophysics Data System (ADS)

Wetland ecosystems are considered a source for radiatively trace gases [methane (CH4), carbon dioxide (CO2), nitrous oxide (N2O)] but flux data for these greenhouse gases are lacking for depressional wetlands that comprise the Prairie Pothole Region. This region is characterized by thousands of small, closed basins that extend along the Missouri Coteau from north central Iowa to central Alberta. Surrounding each body of water are conspicuous zonation patterns given by specific vegetation life-forms and soil properties that are predominately formed by basin hydrology. Basin vegetation zones include deep marsh, shallow marsh, wet meadow, low prairie, and cropland (Stewart and Kantrud,1971). Our primary objective was to determine if net greenhouse gas flux for soils in these wetland basins [mg/m2/day CO2 equivalent (IPCC, 2000)] vary with vegetative zone for prairie pothole ecosystems. These data may then be used to map estimates for total basin greenhouse gas (GHG) flux. Additionally, we aimed to find the relative contribution of each of the 3 trace gases (CO2, CH4 and N2O) to net GHG flux. We hypothesized that flux would be greatest for marsh areas and lowest for upland areas. We selected a semi-permenant prairie pothole research site in Max, ND and mapped respective vegetative zones for 3 adjacent basins. Sample points were randomly selected for each basin and zone using aerial imagery. Samples of soil gases were collected using the static chamber method on August 3, 2003, and these were analyzed using gas chromatography for CO2, CH4 and N2O the following day. Soil moisture, clay content, organic matter, and temperature data were also collected. Net greenhouse gas flux for the cropped zone soils was significantly lower (p<0.01) than flux for the deep marsh, shallow marsh and wet meadow zone soils. Average flux measurement by zone (mg CO2 equivalent/m2/day) was 283 for cropland, 677 for low prairie, 1067 for wet meadow, 2572 for shallow marsh, and 6686 for deep marsh. Methane, in terms of CO2 equivalents, contributed most strongly to and was the best predictor of greenhouse gas flux (r2=0.98). Since most of these basin areas are planted with wheat, average net GHG flux per square meter was 600 to 900 mg CO2 equivalents per day. Our results indicate that there are flux differences among wetland zones within these closed basin ecosystems and that CH4 contributes most to net GHG flux for these wetland soils.

Phillips, R. L.; Beeri, O.; Dekaiser, E. S.

2003-12-01

343

Spreading Topsoil Encourages Ecological Restoration on Embankments: Soil Fertility, Microbial Activity and Vegetation Cover  

PubMed Central

The construction of linear transport infrastructure has severe effects on ecosystem functions and properties, and the restoration of the associated roadslopes contributes to reduce its impact. This restoration is usually approached from the perspective of plant cover regeneration, ignoring plant-soil interactions and the consequences for plant growth. The addition of a 30 cm layer of topsoil is a common practice in roadslope restoration projects to increase vegetation recovery. However topsoil is a scarce resource. This study assesses the effects of topsoil spreading and its depth (10 to 30 cm) on two surrogates of microbial activity (?-glucosidase and phosphatase enzymes activity and soil respiration), and on plant cover, plant species richness and floristic composition of embankment vegetation. The study also evaluates the differences in selected physic-chemical properties related to soil fertility between topsoil and the original embankment substrate. Topsoil was found to have higher values of organic matter (11%), nitrogen (44%), assimilable phosphorous (50%) and silt content (54%) than the original embankment substrate. The topsoil spreading treatment increased microbial activity, and its application increased ?-glucosidase activity (45%), phosphatase activity (57%) and soil respiration (60%). Depth seemed to affect soil respiration, ?-glucosidase and phosphatase activity. Topsoil application also enhanced the species richness of restored embankments in relation to controls. Nevertheless, the depth of the spread topsoil did not significantly affect the resulting plant cover, species richness or floristic composition, suggesting that both depths could have similar effects on short-term recovery of the vegetation cover. A significant implication of these results is that it permits the application of thinner topsoil layers, with major savings in this scarce resource during the subsequent slope restoration work, but the quality of topsoil relative to the original substrate should be previously assessed on a site by site basis. PMID:24984137

Rivera, Desiree; Mejias, Violeta; Jauregui, Berta M.; Lopez-Archilla, Ana Isabel; Peco, Begona

2014-01-01

344

Co-Composting of Soil Heavily Contaminated with Creosote with Cattle Manure and Vegetable Waste for the Bioremediation of Creosote–Contaminated Soil  

Microsoft Academic Search

Mispah form (FAO: Lithosol) soil contaminated with >380 000 mg kg creosote was co-composted with cattle manure and mixed vegetable waste for 19 months. The soil was mixed with wood chips to improve aeration and then mixed with cattle manure or mixed vegetable waste in a ratio of 4:1. Moisture, temperature, pH, ash content, C:N ratios, and the concentrations of

Harrison I. Atagana; R. J. Haynes; F. M. Wallis

2003-01-01

345

Interactions of aluminum with forest soils and vegetation: Implications for acid deposition  

SciTech Connect

Recent evidence suggests that an important ecological consequence of acidic deposition is increased aluminum mobilization. There is concern that increased aluminum activity may produce toxic effects in forested ecosystems. My studies were concerned with the behavior of pedogenic and added aluminum in soils derived from chemically different parent material. Soil aluminum was related to the aluminum content of the vegetation found growing in the soils. In addition, aluminum levels of forest litter was compared to levels determined 40 years ago. Field, greenhouse, and laboratory investigations were conducted in which the effects of aluminum concentration on germination and early growth was determined. Soils were then used in greenhouse and laboratory studies to establish patterns of soil and plant aluminum behavior with implications to acid deposition. Results show that the amount of aluminum extracted was related to the pH value of the extracting solution and to the chemical characteristics of the soil. Some acid rain solutions extracted measurable amounts of aluminum from selected primary minerals. Germination and early growth of Pinus radiata was controlled by levels of aluminum in the soil or in solution. Field studies indicated that most forest species were sensitive to rising levels of aluminum in the soil. In general, ferns and fern allies were less sensitive to very high levels of aluminum in the soil, continuing to grow when more advanced dicots have disappeared. Aluminum tissue levels of all species were related to the concentration of aluminum in the soil as was the reappearance of species. Aluminum levels in leaf litter have risen at least 50% in the last 40 years. These values were consistent over 3 years. The implications to acid deposition were discussed.

Maynard, A.A.

1989-01-01

346

Site identity and moss species as determinants of soil microbial community structure in Norway spruce forests across three vegetation zones  

Microsoft Academic Search

Soil microbial community structure was investigated by PLFA-analysis in four spruce forests in Norway. The maximum latitudinal\\u000a distance between the sites was approximately 350 km. Bilberry Vaccinium myrtillus dominated the forest floor vegetation in the study sites, which were selected because of the vegetation type. Soil samples\\u000a were taken from all four sites under close to 100% homogeneous ground cover of

Lisbet Holm Bach; Åsa Frostegård; Mikael Ohlson

2009-01-01

347

Soil bacterial community shifts in response to vegetation and soil temperature change in moist acidic tundra of Northern Alaska  

NASA Astrophysics Data System (ADS)

The effects of rising temperatures on Earth's ecosystems remain largely unknown and are an active area of research. In temperate systems, plant species often respond directly to climate forcing factors causing complex cascading effects in ecosystem C and nutrient cycling. Similarly, in the Arctic tundra, shifts in aboveground species composition and distribution have been observed in response to warming and other climate change factors, following increases in active layer depth and soil temperature. These abiotic changes provide soil microorganisms access to previously unavailable soil organic matter via thawing soils and increases soil microbial mineralization rates, suggesting that soil microorganisms may be eliciting the plant response. It is hypothesized that this release of nutrients may be providing a competitive advantage to N rich woody species, such as dwarf birch and diamond-leaf willow, over grassy species such as cottongrass tussock. Here we examine how microbial communities respond to increases in soil thermal insulation and vegetative change caused by the accumulation of winter precipitation at a snowfence installed in 1998 at Toolik Field Station, Alaska. In addition to soil temperature, increased snow depth also results in increased surface moisture, soil temperature, and active layer depth. Bacterial phylogenies and relative abundances from soils collected in August of 2012 were determined by sequencing 16S rRNA genes and analyzed using the QIIME software package. We found many significant relative abundance shifts between snow depth treatments (deep, intermediate, low) and soil depths (organic, transition, mineral), most notable of which include in an increase in Deltaproteobacteria in the deep treatment zones, a decrease in Alphaproteobacteria with increased soil depth, and a marked increase in Chloroflexi Anaerolineae (a green non-sulfur bacteria found in a wide range of habitats) in the deep treatment and mineral layers. Other interesting results include the presence of two novel, uncultured phyla of Bacteria, AD3 (phylogenetically related to green non-sulfur bacteria) which was found in mineral layers across all treatments, and OP8 (yet to be characterized), found only in the mineral layers of the deep snow depth treatment.

Ricketts, M. P.; Gonzalez-Meler, M. A.

2013-12-01

348

Impact of spruce forest and grass vegetation cover on soil micromorphology and hydraulic properties of organic matter horizon  

Microsoft Academic Search

Two organic matter horizons developed under a spruce forest and grass vegetation were chosen to demonstrate the impact of\\u000a a different vegetation cover on the micromorphology, porous system and hydraulic properties of surface soils. Micromorphological\\u000a studies showed that the decomposed organic material in the organic matter horizon under the grass vegetation was more compact\\u000a compared to the decomposed organic material

Radka Kodešová; Lenka Pavl?; Vít Kodeš; Anna Žigová; Antonín Nikodem

2007-01-01

349

[Study on hyperspectral estimation model of crop vegetation cover percentage].  

PubMed

In order to boost the study and application of hyperspectral remote sensing for the estimation of crop vegetation coverage percentage, an ASD FieldSpec Pro FRTM spectroradiometer was used for canopy spectral measurements of rape, corn and rice at different vegetation cover levels and photos of individual plants were taken simultaneously in order to calculate the vegetation cover percentage in computer. Firstly, data of three crops respectively and the mixed data of them were used to make correlation analysis between vegetation coverage percentage and reflectance spectra There was a high correlation between them and no obvious difference in correlation coefficient among different types of crop in the region of blue, red and near-infrared band. This indicated that it was feasible to make correlation analysis and build estimation model using mixed data Secondly, mixed data were used as unique analytical data to calculate red edge variables and pair combination of bands in the region of blue, red and near-infrared band was used to calculate normal difference vegetation index (NDVI). Hyperspectral estimation models with NDVI and red edge variable as independent variable were built individually. The correlation coefficient of the former was larger than the latter, which indicated that NDVI was most effective for the estimation of vegetation coverage percentage. Effective wavelength combinations of NDVI for vegetation cover percentage estimation were determined based on the principle of higher correlation coefficient. NDVI combined with bands in the regions from 350 to 590 nm and from 710 to 1150 nm or bands in the regions from 590 to 710 nm and from 710 to 1300 nm are most effective for vegetation coverage percentage estimation. The best estimation model is simple quadratic equation using NDVI(696-921) as independent variable. The correlation coefficient matrix shows that most of the correlation coefficients of vegetation coverage percentage and NDVI combined with bands in the regions from 630 to 690 nm and from 760 to 900 nm are larger than 0.8. These two band regions correspond to TM3 and TM4 of landsat 4,5,7. It proves that NDVI(TM3-TM4) can be used to and has been used to simulate vegetation coverage percentage. In order to further the study, TM3 and TM4 of Landsat5 was modeled according to spectral response function to calculate NDVI. Correlation analysis was made with NDVI and corresponding vegetation coverage percentage. The correlation coefficient of them was 0.80 and the regression equation was verified by experimental data. This is exploratory research for the calculation of vegetation coverage percentage using TM data in large area. PMID:18975813

Zhu, Lei; Xu, Jun-feng; Huang, Jing-feng; Wang, Fu-min; Liu, Zhan-yu; Wang, Yuan

2008-08-01

350

Vegetation and soil erosion under a semi-arid Mediterranean climate: a case study from Murcia (Spain)  

Microsoft Academic Search

The objectives of the present work are to analyse some relationships between soil and vegetation parameters for Mediterranean matorral in the El Ardal experimental field site in Murcia (Spain), the response of this system in terms of erosion and runoff, and the pedological and vegetation effects of some disturbing factors such as agricultural use and grazing. The El Ardal experimental

Francisco López-Bermúdez; Asunción Romero-D??az; José Mart??nez-Fernandez; Julia Mart??nez-Fernandez

1998-01-01

351

Investigation of heavy-metal uptake by vegetables growing in contaminated soils using the modified BCR sequential extraction method  

Microsoft Academic Search

The heavy metal (Cu, Fe, Co, Ni, Cd, Cr, Pb, Zn, and Mn) concentrations in soils and in vegetable samples, i.e. lettuce (Lactuca sativa L.), parsley (Petroselinum crispum), dill (Anethum graveolens), and onion (Allium cepa L.), taken from three urban vegetable gardens in Kayseri, Turkey, were determined by FAAS. The modified three-step sequential extraction procedure proposed by the European Bureau

?er?fe Tokalio?lu; ?enol Kartal; Ar?f Gültek?n

2006-01-01

352

Responses of soil microbial and nematode communities to aluminum toxicity in vegetated oil-shale-waste lands.  

PubMed

Both soil nematodes and microorganisms have been shown to be sensitive bioindicators of soil recovery in metal-contaminated habitats; however, the underlying processes are poorly understood. We investigated the relationship among soil microbial community composition, nematode community structure and soil aluminum (Al) content in different vegetated aluminum-rich ecosystems. Our results demonstrated that there were greater soil bacterial, fungal and arbuscular mycorrhizal fungal biomass in Syzygium cumini plantation, greater abundance of soil nematodes in Acacia auriculiformis plantation, and greater abundance of soil predatory and herbivorous nematodes in Schima wallichii plantation. The concentration of water-soluble Al was normally greater in vegetated than non-vegetated soil. The residual Al and total Al concentrations showed a significant decrease after planting S. cumini plantation onto the shale dump. Acid extractable, reducible and oxidisable Al concentrations were greater in S. wallichii plantation. Stepwise linear regression analysis suggests the concentrations of water-soluble Al and total Al content explain the most variance associated with nematode assembly; whereas, the abundance of early-successional nematode taxa was explained mostly by soil moisture, soil organic C and total N rather than the concentrations of different forms of Al. In contrast, no significant main effects of either Al or soil physico-chemical characteristics on soil microbial biomass were observed. Our study suggests that vegetation was the primary driver on soil nematodes and microorganisms and it also could regulate the sensitivity of bio-indicator role mainly through the alteration of soil Al and physico-chemical characteristics, and S. cumini is effective for amending the Al contaminated soils. PMID:22732942

Shao, Yuanhu; Zhang, Weixin; Liu, Zhanfeng; Sun, Yuxin; Chen, Dima; Wu, Jianping; Zhou, Lixia; Xia, Hanping; Neher, Deborah A; Fu, Shenglei

2012-11-01

353

Technical note monitoring native vegetation on a dumpsite of PCB-contaminated soil.  

PubMed

Composition of native vegetation on a polychlorinated biphenyls (PCB)-contaminated soil dumpsite at Lhenice, South Bohemia (Czech Republic), was determined and species variability in the accumulation of PCBs in plant biomass was investigated. Soil stripping contaminated by PCBs originated at a factory producing electrical transformers that mostly used the commercial PCB mixture Delor 103 and 106. The PCB content of soil in the most contaminated part of the dumpsite reached 153 mg kg(-1) dry soil. Low diversity of plant species was found on the dumpsite. Results showed three grass species, Festuca arundinacea Schreb., Phalaroides arundinacea (L.) Rauschert., and Calamagrostis epigeios (L.) Roth., to be the major components of the vegetation and confirmed their high tolerance toward PCB contamination. The highest content of PCB in plant biomass--813.2 microg kg(-1) dry biomass--was determined in Festuca aboveground biomass. For phytoextraction purposes especially, Festuca can be recommended due to its high biomass yield, but its bioconcentration factor was very low (0.006). Tripleurospermum maritimum (L.) Sch. Bip. and Cirsium arvense (L.) Scop. grew mainly at the margins of the most contaminated part of the dumpsite. The PCB content determined in their aboveground biomass-278.7 and 289.5 microg kg(-1) dry biomass, respectively--was nonsignificantly lower compared to grass species Phalaroides and Calamagrostis. Salix (Salix viminalis L. and Salix caprea L.) was monitored among plant species composition at this site as a representative of woody species. PMID:18246716

Pavlíková, Daniela; Macek, Tomas; Macková, Martina; Pavlík, Milan

2007-01-01

354

The soil carbon/nitrogen ratio and moisture affect microbial community structures in alkaline permafrost-affected soils with different vegetation types on the Tibetan plateau.  

PubMed

In the Tibetan permafrost region, vegetation types and soil properties have been affected by permafrost degradation, but little is known about the corresponding patterns of their soil microbial communities. Thus, we analyzed the effects of vegetation types and their covariant soil properties on bacterial and fungal community structure and membership and bacterial community-level physiological patterns. Pyrosequencing and Biolog EcoPlates were used to analyze 19 permafrost-affected soil samples from four principal vegetation types: swamp meadow (SM), meadow (M), steppe (S) and desert steppe (DS). Proteobacteria, Acidobacteria, Bacteroidetes and Actinobacteria dominated bacterial communities and the main fungal phyla were Ascomycota, Basidiomycota and Mucoromycotina. The ratios of Proteobacteria/Acidobacteria decreased in the order: SM>M>S>DS, whereas the Ascomycota/Basidiomycota ratios increased. The distributions of carbon and nitrogen cycling bacterial genera detected were related to soil properties. The bacterial communities in SM/M soils degraded amines/amino acids very rapidly, while polymers were degraded rapidly by S/DS communities. UniFrac analysis of bacterial communities detected differences among vegetation types. The fungal UniFrac community patterns of SM differed from the others. Redundancy analysis showed that the carbon/nitrogen ratio had the main effect on bacteria community structures and their diversity in alkaline soil, whereas soil moisture was mainly responsible for structuring fungal communities. Thus, microbial communities and their functioning are probably affected by soil environmental change in response to permafrost degradation. PMID:24463013

Zhang, Xinfang; Xu, Shijian; Li, Changming; Zhao, Lin; Feng, Huyuan; Yue, Guangyang; Ren, Zhengwei; Cheng, Guogdong

2014-01-01

355

Modeling the interaction between flow and highly flexible aquatic vegetation  

NASA Astrophysics Data System (ADS)

Aquatic vegetation has an important role in estuaries and rivers by acting as bed stabilizer, filter, food source, and nursing area. However, macrophyte populations worldwide are under high anthropogenic pressure. Protection and restoration efforts will benefit from more insight into the interaction between vegetation, currents, waves, and sediment transport. Most aquatic plants are very flexible, implying that their shape and hence their drag and turbulence production depend on the flow conditions. We have developed a numerical simulation model that describes this dynamic interaction between very flexible vegetation and a time-varying flow, using the sea grass Zostera marina as an example. The model consists of two parts: an existing 1DV k-? turbulence model simulating the flow combined with a new model simulating the bending of the plants, based on a force balance that takes account of both vegetation position and buoyancy. We validated this model using observations of positions of flexible plastic strips and of the forces they are subjected to, as well as hydrodynamic measurements. The model predicts important properties like the forces on plants, flow velocity profiles, and turbulence characteristics well. Although the validation data are limited, the results are sufficiently encouraging to consider our model to be of generic value in studying flow processes in fields of flexible vegetation.

Dijkstra, J. T.; Uittenbogaard, R. E.

2010-12-01

356

Geothermal environmental assessment baseline study: vegetation and soils of the Roosevelt Hot Springs Geothermal Resource Area  

SciTech Connect

Identification and elemental concentrations of indigenous soil and plant systems found on the Roosevelt Hot Spring KGRA are described. Twenty-three different soils and five separate plant communities are geographically mapped and identified. One hundred forty-seven plant species were identified. Forbs, shrubs, and grasses are represented by 58, 53, and 36 species respectively. Three sites, each measuring 25 hectares, were selected for long-term vegetative assessment. At these locations a permanent enclosure measuring 24.4 meters x 24.4 meters was constructed to assess long-term effects of livestock grazing. Biomass, plant species, percentage composition, ground cover and livestock carrying capacities were determined at each site. Surface soils and Artemisia tridentata leaf tissue were collected for elemental analysis.

Brown, K.W.; Wiersma, G.B.

1981-07-01

357

Geothermal environmental assessment baseline study: Vegetation and soils of the Roosevelt Hot Springs geothermal resource area  

NASA Astrophysics Data System (ADS)

Identification and elemental concentrations of indigenous soil and plant systems found on the Roosevelt Hot Spring KGRA are described. Twenty-three different soils and five separate plant communities are geographically mapped and identified. One hundred forty-seven plant species were identified. Forbs, shrubs, and grasses are represented by 58, 53, and 36 species respectively. Three sites each measuring 25 hectares were selected for long-term vegetative assessment. At these locations a permanent enclosure measuring 24.4 meters x 24.4 meters was constructed to assess long-term effects livestock grazing. Biomass plant species, percentage composition, ground cover and livetock carrying capacities were determined at each site. Surface soils and Artemisia tridentata leaf tissue were collected for elemental analysis.

Brown, K. W.; Wiersma, G. B.

1981-07-01

358

Effects of various uranium leaching procedures on soil: Short-term vegetation growth and physiology. Progress report, April 1994  

SciTech Connect

Significant volumes of soil containing elevated levels of uranium exist in the eastern United States. The contamination resulted from the development of the nuclear industry in the United States requiring a large variety of uranium products. The contaminated soil poses a collection and disposal problem of a magnitude that justifies the development of decontamination methods. Consequently, the Department of Energy (DOE) Office of Technology Development formed the Uranium Soils Integrated Demonstration (USID) program to address the problem. The fundamental goal of the USID task group has been the selective extraction/leaching or removal of uranium from soil faster, cheaper, and safer than what can be done using current conventional technologies. The objective is to selectively remove uranium from soil without seriously degrading the soil`s physicochemical characteristics and without generating waste that is difficult to manage and/or dispose of. However, procedures developed for removing uranium from contaminated soil have involved harsh chemical treatments that affect the physicochemical properties of the soil. The questions are (1) are the changes in soil properties severe enough to destroy the soil`s capacity to support and sustain vegetation growth and survival? and (2) what amendments might be made to the leached soil to return it to a reasonable vegetation production capacity? This study examines the vegetation-support capacity of soil that had been chemically leached to remove uranium. The approach is to conduct short-term germination and phytotoxicity tests for evaluating soils after they are subjected to various leaching procedures followed by longer term pot studies on successfully leached soils that show the greatest capacity to support plant growth. This report details the results from germination and short-term phytotoxicity testing of soils that underwent a variety of leaching procedures at the bench scale at ORNL and at the pilot plant at Fernald.

Edwards, N.T.

1994-08-01

359

Fire as an interactive component of dynamic vegetation models  

Microsoft Academic Search

Fire affects ecosystems by altering both their structure and the cycling of carbon and nutrients. The emissions from fires represent an important biogeochemical pathway by which the biosphere affects climate. For climate change studies it is important to model fire as a mechanistic climate-dependent process in dynamic global vegetation models (DGVMs) and the terrestrial ecosystem components of climate models. We

Vivek K. Arora; George J. Boer

2005-01-01

360

Temporal variation of aqueous-extractable Ca, Mg and K in acidified forest mountainous soils under different vegetation cover  

NASA Astrophysics Data System (ADS)

Acidification of forest soils is a natural degradation process which can be significantly enhanced by anthropogenic activities. Inputs of basic cations (BC - Ca, Mg and K) via precipitation, litter and soil organic matter decomposition and also via inter-soil weathering may partially mitigate the consequences of this degradation process. The aim of this study is to assess the temporal variation of aqueous-extractable Ca, Mg and K in acidified forest mountainous soils under different vegetation cover. The Jizera Mountains region (Czech Republic, northern Bohemia) was chosen as a representative soil mountainous ecosystem strongly affected by acidification. Soil and precipitation samples were collected at monthly basis from April till October/ November during the years 2009-2011. Study spots were delimited under two contrasting vegetation covers - beech and spruce monoculture. Prevailing soil types were classified as Alumic Cambisols under beech and Entic Podzols under spruce stands (according to FAO classification). Soil samples were collected from surface fermentation (F) and humified (H) organic horizons and subsurface B horizons (cambic or spodic). The collected soil samples were analyzed immediately under laboratory condition in a "fresh" state. Unsieved fresh samples were extracted by deionised water. The content of main elements (Ca, Mg, K, Al and Fe) was determined by ICP-OES. The content of major anions (SO42-, NO3-, Cl- and F-) was determined by ion-exchange chromatography (IC). Content of major anions and main elements were determined in the precipitation samples (throughfall, stemflow and bulk) as well. Besides computing the basic statistical parameters (mean, median, variance, maximum, minimum, etc.) we also employed other statistical methods such as T-test and ANOVA to assess the differences between beech and spruce vegetation spots. To carry out the temporal variability in the data we used the time series analysis and short-term forecasting by Holt-Winters exponential smoothing and ARIMA models. Our results clearly exhibit differences in the horizontal and spatial distribution of BC. The influences of the study spot, i.e. the influence of stand factors e.g. vegetation covers on BC distribution are well pronounced. The highest amounts of aqueous extractable BC were identified in the F and H organic horizons. The contents of Ca and Mg were significantly higher under beech cover than under spruce cover. The influence of seasonality on BC content and distribution was the strongest in the upper organic horizons. The annual changes are less pronounced in inner mineral B horizons. We have observed a significant influence of the snow melting period - after this event the content of BC was the lowest. In contrast, the BC content rises during the summer period - the time of high biological activity and accelerated organic matter decomposition. This period is again followed by a BC content decrease during the fall period - the time of gradually decreasing biological activity and high precipitation. Generally, we can conclude that the seasonal variations are higher than annual and spatial for both sites.

Tejnecky, V.; Bradová, M.; Boruvka, L.; Vasat, R.; Nemecek, K.; Ash, C.; Sebek, O.; Rejzek, J.; Drabek, O.

2012-12-01

361

Effects of coal-bed methane discharge waters on the vegetation and soil ecosystem in Powder River Basin, Wyoming  

USGS Publications Warehouse

Coal-bed methane (CBM) co-produced discharge waters in the Powder River Basin of Wyoming, resulting from extraction of methane from coal seams, have become a priority for chemical, hydrological and biological research during the last few years. Soil and vegetation samples were taken from affected and reference sites (upland elevations and wetted gully) in Juniper Draw to investigate the effects of CBM discharge waters on soil physical and chemical properties and on native and introduced vegetation density and diversity. Results indicate an increase of salinity and sodicity within local soil ecosystems at sites directly exposed to CBM discharge waters. Elevated concentrations of sodium in the soil are correlated with consistent exposure to CBM waters. Clay-loam soils in the study area have a much larger specific surface area than the sandy soils and facilitate a greater sodium adsorption. However, there was no significant relation between increasing water sodium adsorption ratio (SAR) values and increasing sediment SAR values downstream; however, soils exposed to the CBM water ranged from the moderate to severe SAR hazard index. Native vegetation species density was highest at the reference (upland and gully) and CBM affected upland sites. The affected gully had the greatest percent composition of introduced vegetation species. Salt-tolerant species had the greatest richness at the affected gully, implying a potential threat of invasion and competition to established native vegetation. These findings suggest that CBM waters could affect agricultural production operations and long-term water quality. ?? Springer 2005.

Stearns, M.; Tindall, J.A.; Cronin, G.; Friedel, M.J.; Bergquist, E.

2005-01-01

362

Characterization and risk assessment of polychlorinated biphenyls in soils and vegetations near an electronic waste recycling site, South China.  

PubMed

This study aimed at identifying the levels of PCBs generated from e-waste recycling, and their potential impacts on the soils and vegetations as well. The ?PCBs concentrations in soil</