Science.gov

Sample records for soil vegetation model

  1. A nonlinear coupled soil moisture-vegetation model

    NASA Astrophysics Data System (ADS)

    Liu, Shikuo; Liu, Shida; Fu, Zuntao; Sun, Lan

    2005-06-01

    Based on the physical analysis that the soil moisture and vegetation depend mainly on the precipitation and evaporation as well as the growth, decay and consumption of vegetation a nonlinear dynamic coupled system of soil moisture-vegetation is established. Using this model, the stabilities of the steady states of vegetation are analyzed. This paper focuses on the research of the vegetation catastrophe point which represents the transition between aridness and wetness to a great extent. It is shown that the catastrophe point of steady states of vegetation depends mainly on the rainfall P and saturation value v0, which is selected to balance the growth and decay of vegetation. In addition, when the consumption of vegetation remains constant, the analytic solution of the vegetation equation is obtained.

  2. Modeling soil water content for vegetation modeling improvement

    NASA Astrophysics Data System (ADS)

    Cianfrani, Carmen; Buri, Aline; Zingg, Barbara; Vittoz, Pascal; Verrecchia, Eric; Guisan, Antoine

    2016-04-01

    Soil water content (SWC) is known to be important for plants as it affects the physiological processes regulating plant growth. Therefore, SWC controls plant distribution over the Earth surface, ranging from deserts and grassland to rain forests. Unfortunately, only a few data on SWC are available as its measurement is very time consuming and costly and needs specific laboratory tools. The scarcity of SWC measurements in geographic space makes it difficult to model and spatially project SWC over larger areas. In particular, it prevents its inclusion in plant species distribution model (SDMs) as predictor. The aims of this study were, first, to test a new methodology allowing problems of the scarcity of SWC measurements to be overpassed and second, to model and spatially project SWC in order to improve plant SDMs with the inclusion of SWC parameter. The study was developed in four steps. First, SWC was modeled by measuring it at 10 different pressures (expressed in pF and ranging from pF=0 to pF=4.2). The different pF represent different degrees of soil water availability for plants. An ensemble of bivariate models was built to overpass the problem of having only a few SWC measurements (n = 24) but several predictors to include in the model. Soil texture (clay, silt, sand), organic matter (OM), topographic variables (elevation, aspect, convexity), climatic variables (precipitation) and hydrological variables (river distance, NDWI) were used as predictors. Weighted ensemble models were built using only bivariate models with adjusted-R2 > 0.5 for each SWC at different pF. The second step consisted in running plant SDMs including modeled SWC jointly with the conventional topo-climatic variable used for plant SDMs. Third, SDMs were only run using the conventional topo-climatic variables. Finally, comparing the models obtained in the second and third steps allowed assessing the additional predictive power of SWC in plant SDMs. SWC ensemble models remained very good, with

  3. Vegetation Dynamics And Soil Moisture: Consequences For Hydrologic Modeling

    NASA Astrophysics Data System (ADS)

    Guardiola-Claramonte, M.; Troch, P. A.

    2007-12-01

    Current global population growth and economical development accelerates land cover conversion in many parts of the world. Introducing non-native species and woody species encroachment, with different water demands, can affect the partitioning of hydrological fluxes. The impacts on the hydrologic cycle at local to regional scales are poorly understood. The present study investigates the hydrologic implications of land use conversion from native vegetation to rubber. We first compare the vegetation dynamics of rubber (Hevea brasiliensis), a non- native specie in Southeast Asia, to the other main vegetation types in the study area. The experimental catchment, Nam Ken (69km 2), is located in the Xishuangbanna Prefecture (21 °N, 100 °E), in the south of Yunnan province in South China. From 2005 to 2006, we collected continuous records of 2 m deep soil moisture profiles in four different land covers (tea, secondary forest, grassland and rubber), and measured surface radiation in tea and rubber canopies. Our observations show that root water uptake by rubber during the dry season is controlled by the change of day-length, whereas water demand of the native vegetation starts with the arrival of the first monsoon rainfall. The different root water uptake dynamics of rubber result in distinct depletion of deeper layer soil moisture. Traditional evapotranspiration and soil moisture models are unable to simulate this specific behavior, thus a different conceptual model is needed to predict hydrologic changes due to land use conversion in the area.

  4. Modeling radium and radon transport through soil and vegetation

    USGS Publications Warehouse

    Kozak, J.A.; Reeves, H.W.; Lewis, B.A.

    2003-01-01

    A one-dimensional flow and transport model was developed to describe the movement of two fluid phases, gas and water, within a porous medium and the transport of 226Ra and 222Rn within and between these two phases. Included in this model is the vegetative uptake of water and aqueous 226Ra and 222Rn that can be extracted from the soil via the transpiration stream. The mathematical model is formulated through a set of phase balance equations and a set of species balance equations. Mass exchange, sink terms and the dependence of physical properties upon phase composition couple the two sets of equations. Numerical solution of each set, with iteration between the sets, is carried out leading to a set-iterative compositional model. The Petrov-Galerkin finite element approach is used to allow for upstream weighting if required for a given simulation. Mass lumping improves solution convergence and stability behavior. The resulting numerical model was applied to four problems and was found to produce accurate, mass conservative solutions when compared to published experimental and numerical results and theoretical column experiments. Preliminary results suggest that the model can be used as an investigative tool to determine the feasibility of phytoremediating radium and radon-contaminated soil. ?? 2003 Elsevier Science B.V. All rights reserved.

  5. Soil detachment by overland flow under different vegetation restoration models in the loess plateau of China

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Land use change has significant effects on soil properties and vegetation cover and thus probably affects soil detachment by overland flow. Few studies were conducted to evaluate the effect of restoration models on the soil detachment process in the Loess Plateau in the past decade during which a Gr...

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

    NASA Technical Reports Server (NTRS)

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

    1998-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

    Baudena, M.; D'Andrea, F.; Provenzale, A.

    2008-12-01

    We study the interaction between atmosphere, soil moisture, and vegetation in water-limited environments with significant water recycling, and introduce a simple process model including some of the main feedbacks active in the system. In our model, the soil-vegetation-atmosphere dynamics display two stable states for realistic values of the synoptic moisture convergence flux. Starting from low soil moisture and/or low vegetation cover, the system reaches a dry and hot state, whereas it reaches a wet and cool state when starting from higher initial values of soil moisture and of vegetation cover. The role of synoptic perturbations is investigated by inserting a stochastic input of moisture: in this case, a bimodal distribution of soil moisture is obtained. We explore the difference between the dynamics of natural vegetation, capable of adjusting its areal extent to variations in soil moisture, and cultivated vegetation, whose areal extent cannot vary. The model results indicate that the presence of natural vegetation increases the probability of reaching a wet/cool state with respect to the case of cultivated plants.

  8. Measuring and modeling water-related soil-vegetation feedbacks in a fallow plot

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    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 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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-08-01

    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.

  10. Soil and vegetation surveillance

    SciTech Connect

    Antonio, E.J.

    1995-06-01

    Soil sampling and analysis evaluates long-term contamination trends and monitors environmental radionuclide inventories. This section of the 1994 Hanford Site Environmental Report summarizes the soil and vegetation surveillance programs which were conducted during 1994. Vegetation surveillance is conducted offsite to monitor atmospheric deposition of radioactive materials in areas not under cultivation and onsite at locations adjacent to potential sources of radioactivity.

  11. Evaluation of a Linear Mixing Model to Retrieve Soil and Vegetation Temperatures of Land Targets

    NASA Astrophysics Data System (ADS)

    Yang, Jinxin; Jia, Li; Cui, Yaokui; Zhou, Jie; Menenti, Massimo

    2014-03-01

    A simple linear mixing model of heterogeneous soil-vegetation system and retrieval of component temperatures from directional remote sensing measurements by inverting this model is evaluated in this paper using observations by a thermal camera. The thermal camera was used to obtain multi-angular TIR (Thermal Infra-Red) images over vegetable and orchard canopies. A whole thermal camera image was treated as a pixel of a satellite image to evaluate the model with the two-component system, i.e. soil and vegetation. The evaluation included two parts: evaluation of the linear mixing model and evaluation of the inversion of the model to retrieve component temperatures. For evaluation of the linear mixing model, the RMSE is 0.2 K between the observed and modelled brightness temperatures, which indicates that the linear mixing model works well under most conditions. For evaluation of the model inversion, the RMSE between the model retrieved and the observed vegetation temperatures is 1.6K, correspondingly, the RMSE between the observed and retrieved soil temperatures is 2.0K. According to the evaluation of the sensitivity of retrieved component temperatures on fractional cover, the linear mixing model gives more accurate retrieval accuracies for both soil and vegetation temperatures under intermediate fractional cover conditions.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    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

  13. Modeling the effects of vegetation on methane oxidation and emissions through soil landfill final covers across different climates.

    PubMed

    Abichou, Tarek; Kormi, Tarek; Yuan, Lei; Johnson, Terry; Francisco, Escobar

    2015-02-01

    Plant roots are reported to enhance the aeration of soil by creating secondary macropores which improve the diffusion of oxygen into soil as well as the supply of methane to bacteria. Therefore, methane oxidation can be improved considerably by the soil structuring processes of vegetation, along with the increase of organic biomass in the soil associated with plant roots. This study consisted of using a numerical model that combines flow of water and heat with gas transport and oxidation in soils, to simulate methane emission and oxidation through simulated vegetated and non-vegetated landfill covers under different climatic conditions. Different simulations were performed using different methane loading flux (5-200 g m(-2) d(-1)) as the bottom boundary. The lowest modeled surface emissions were always obtained with vegetated soil covers for all simulated climates. The largest differences in simulated surface emissions between the vegetated and non-vegetated scenarios occur during the growing season. Higher average yearly percent oxidation was obtained in simulations with vegetated soil covers as compared to non-vegetated scenario. The modeled effects of vegetation on methane surface emissions and percent oxidation were attributed to two separate mechanisms: (1) increase in methane oxidation associated with the change of the physical properties of the upper vegetative layer and (2) increase in organic matter associated with vegetated soil layers. Finally, correlations between percent oxidation and methane loading into simulated vegetated and non-vegetated covers were proposed to allow decision makers to compare vegetated versus non-vegetated soil landfill covers. These results were obtained using a modeling study with several simplifying assumptions that do not capture the complexities of vegetated soils under field conditions.

  14. Snow modeling within a multi-layer soil-vegetation-atmosphere model

    NASA Astrophysics Data System (ADS)

    McGowan, L. E.; Paw U, K. T.; Pyles, D. R.

    2014-12-01

    Estimates of snow depth, extent, and melt in the Sierra Nevada Mountain Range are critical to estimating the amount of water that will be available for crops during the growing season within California's Central Valley. Numerical simulations utilizing a fourth order turbulent closure transport scheme in a multi-layer soil-vegetation-atmosphere model, Advanced Canopy-Atmosphere-Soil algorithm (ACASA), were used to explore snow model improvements in the physics-based parameterization for the Sierra Nevada Range. A set of alterations were made separately to the existing snowpack model within ACASA focusing on improvements to snow cover simulations on complex terrain slopes and over varying canopy cover. Three winter seasons were simulated; a climatological average, dry, and wet winter. The simulated output from the models are compared to observations to determine which model alterations made the largest improvements to snow simulations.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    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.

  16. Advances in modelling the coevolving soils, landforms and vegetation in semiarid regions: a multidisciplinary approach.

    NASA Astrophysics Data System (ADS)

    Saco, Patricia M.; Moreno-de las Heras, Mariano; Willgoose, Garry R.

    2014-05-01

    Semiarid landscapes exhibit highly nonlinear interactions between coevolving physical and biological processes. Coevolution in these systems leads to the emergence of remarkable soil, landform and vegetation patterns. Growing concern over ecosystem resilience to climate and land use perturbations that could result in irreversible degradation imposes a pressing need for research, aiming at elucidating the processes, feedbacks, and dynamics leading to these coevolving patterns. This is particularly important since degradation in drylands has been frequently linked to feedback effects between soils, biota and erosion processes. In many dryland regions, feedbacks are responsible for the emergence of areas with low infiltration in unvegetated soil patches (due to surface crusting) and high infiltration rates in the vegetated soil patches (due to improved soil aggregation and macroporosity). This variable infiltration field gives rise to runoff-runon redistribution which determines areas of soil erosion and deposition. We have combined a coupled landform-soil-vegetation model with remote sensing and field data to capture these feedbacks and improve our knowledge of these coevolving biotic-abiotic processes. We discuss and present results showing that the dynamics of the individual processes and their response to climatic and anthropic disturbances cannot be fully understood or predicted if nonlinear feedbacks and coevolution are not considered. Implications for management and restoration efforts are illustrated using data and observations from agricultural sites in central Australia and reclaimed mining sites in Spain.

  17. Analyzing model uncertainty in predicted surface fluxes resulting from prescribed soil and vegetation parameters

    NASA Astrophysics Data System (ADS)

    Jankov, M.; Prochaka, L.; Mölders, N.

    2003-12-01

    The atmosphere and land-surface continuously interact, for which the surface affects current weather and climate. The biosphere-soil system plays an important role because it is the media in those interactions. The processes that describe those interactions are the exchange of momentuum, heat, water vapor, and matter. To include these processes at the soil-biosphere-atmosphere interface in atmospheric models they have to be parameterized. The different vegetation and soil types are realized by prescribed plant physiological and soil physical parameters (e.g. soil hydraulic conductivity, soil thermal conductivity, porosity, pore-size distribution index, leaf area index, albedo and emissivity of the foliage and soil, minimum stomatal resistance, canopy height, etc.) in these parameterizations. The parameters can vary even among the same soil or plant type. The order of magnitude of those variations can be as much as the mean values of the parameters themselves. In order to improve weather prediction the model uncertainty, caused by the necessity to prescribe parameters, has to be minimized. To asses the errors uncertainty analysis with respect to the prescribed parameters is carried out using the Gaussian Error Propagation method. We use the PennState/NCAR mesoscale meteorological model MM5 coupled with the Oregon State University land surface model (OSULSM) as the test-platform. The Gaussian Error Propagation technique provides error bars for the fluxes simulated by MM5. Moreover, the technique can point out which parameters contribute the most to the error, and should be replaced in future model development. Our preliminary results show that throughout the domain errors were at low or moderate levels. The highest errors predicted appear to be associated with scarcely vegetated, sandy clay loam areas and areas covered by ice and snow.

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

    USGS Publications Warehouse

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

    2003-01-01

    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

  19. Vegetation and soils

    USGS Publications Warehouse

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

    2000-01-01

    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).

  20. Developing risk models of Cryptosporidium transport in soils from vegetated, tilted soilbox experiments.

    PubMed

    Harter, Thomas; Atwill, Edward R; Hou, Lingling; Karle, Betsy M; Tate, Kenneth W

    2008-01-01

    Transport of Cryptosporidium parvum through macroporous soils is poorly understood yet critical for assessing the risk of groundwater contamination. We developed a conceptual model of the physics of flow and transport in packed, tilted, and vegetated soilboxes during and immediately after a simulated rainfall event and applied it to 54 experiments implemented with different soils, slopes, and rainfall rates. Using a parsimonious inverse modeling procedure, we show that a significant amount of subsurface outflow from the soilboxes is due to macropore flow. The effective hydraulic properties of the macropore space were obtained by calibration of a simple two-domain flow and transport model that accounts for coupled flow in the matrix and in the macropores of the soils. Using linear mixed-effects analysis, macropore hydraulic properties and oocyst attenuation were shown to be associated with soil bulk density and rainfall rate. Macropore flow was shown to be responsible for bromide and C. parvum transport through the soil into the underlying pore space observed during the 4-h experiments. We confirmed this finding by conducting a pair of saturated soil column studies under homogeneously repacked conditions with no macropores in which no C. parvum transport was observed in the effluent. The linear mixed-effects and logistic regression models developed from the soilbox experiments provide a basis for estimating macropore hydraulic properties and the risk of C. parvum transport through shallow soils from bulk density, precipitation, and total shallow subsurface flow rate. The risk assessment is consistent with the reported occurrence of oocysts in springs or groundwater from fractured or karstic rocks protected only by shallow overlying soils.

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

    PubMed

    Zhang, Yan; Yuan, Jianping; Liu, Baoyuan

    2002-08-01

    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.

  2. Coupled Hydro-Mechanical Constitutive Model for Vegetated Soils: Validation and Applications

    NASA Astrophysics Data System (ADS)

    Switala, Barbara Maria; Veenhof, Rick; Wu, Wei; Askarinejad, Amin

    2016-04-01

    It is well known, that presence of vegetation influences stability of the slope. However, the quantitative assessment of this contribution remains challenging. It is essential to develop a numerical model, which combines mechanical root reinforcement and root water uptake, and allows modelling rainfall induced landslides of vegetated slopes. Therefore a novel constitutive formulation is proposed, which is based on the modified Cam-clay model for unsaturated soils. Mechanical root reinforcement is modelled introducing a new constitutive parameter, which governs the evolution of the Cam-clay failure surface with the degree of root reinforcement. Evapotranspiration is modelled in terms of the root water uptake, defined as a sink term in the water flow continuity equation. The original concept is extended for different shapes of the root architecture in three dimensions, and combined with the mechanical model. The model is implemented in the research finite element code Comes-Geo, and in the commercial software Abaqus. The formulation is tested, performing a series of numerical examples, which allow validation of the concept. The direct shear test and the triaxial test are modelled in order to test the performance of the mechanical part of the model. In order to validate the hydrological part of the constitutive formulation, evapotranspiration from the vegetated box is simulated and compared with the experimental results. Obtained numerical results exhibit a good agreement with the experimental data. The implemented model is capable of reproducing results of basic geotechnical laboratory tests. Moreover, the constitutive formulation can be used to model rainfall induced landslides of vegetated slopes, taking into account the most important factors influencing the slope stability (root reinforcement and evapotranspiration).

  3. Correcting the influence of vegetation on surface soil moisture indices by using hyperspectral artificial 3D-canopy models

    NASA Astrophysics Data System (ADS)

    Spengler, D.; Kuester, T.; Frick, A.; Scheffler, D.; Kaufmann, H.

    2013-10-01

    Surface soil moisture content is one of the key variables used for many applications especially in hydrology, meteorology and agriculture. Hyperspectral remote sensing provides effective methodologies for mapping soil moisture content over a broad area by different indices such as NSMI [1,2] and SMGM [3]. Both indices can achieve a high accuracy for non-vegetation influenced soil samples, but their accuracy is limited in case of the presence of vegetation. Since, the increase of the vegetation cover leads to non-linear variations of the indices. In this study a new methodology for moisture indices correcting the influence of vegetation is presented consisting of several processing steps. First, hyperspectral reflectance data are classified in terms of crop type and growth stage. Second, based on these parameters 3D plant models from a database used to simulate typical canopy reflectance considering variations in the canopy structure (e.g. plant density and distribution) and the soil moisture content for actual solar illumination and sensor viewing angles. Third, a vegetation correction function is developed, based on the calculated soil moisture indices and vegetation indices of the simulated canopy reflectance data. Finally this function is applied on hyperspectral image data. The method is tested on two hyperspectral image data sets of the AISA DUAL at the test site Fichtwald in Germany. The results show a significant improvements compared to solely use of NSMI index. Up to a vegetation cover of 75 % the correction function minimise the influences of vegetation cover significantly. If the vegetation is denser the method leads to inadequate quality to predict the soil moisture content. In summary it can be said that applying the method on weakly to moderately overgrown with vegetation locations enables a significant improvement in the quantification of soil moisture and thus greatly expands the scope of NSMI.

  4. Smart plants, smart models? On adaptive responses in vegetation-soil systems

    NASA Astrophysics Data System (ADS)

    van der Ploeg, Martine; Teuling, Ryan; van Dam, Nicole; de Rooij, Gerrit

    2015-04-01

    Hydrological models that will be able to cope with future precipitation and evapotranspiration regimes need a solid base describing the essence of the processes involved [1]. The essence of emerging patterns at large scales often originates from micro-behaviour in the soil-vegetation-atmosphere system. A complicating factor in capturing this behaviour is the constant interaction between vegetation and geology in which water plays a key role. The resilience of the coupled vegetation-soil system critically depends on its sensitivity to environmental changes. To assess root water uptake by plants in a changing soil environment, a direct indication of the amount of energy required by plants to take up water can be obtained by measuring the soil water potential in the vicinity of roots with polymer tensiometers [2]. In a lysimeter experiment with various levels of imposed water stress the polymer tensiometer data suggest maize roots regulate their root water uptake on the derivative of the soil water retention curve, rather than the amount of moisture alone. As a result of environmental changes vegetation may wither and die, or these changes may instead trigger gene adaptation. Constant exposure to environmental stresses, biotic or abiotic, influences plant physiology, gene adaptations, and flexibility in gene adaptation [3-7]. To investigate a possible relation between plant genotype, the plant stress hormone abscisic acid (ABA) and the soil water potential, a proof of principle experiment was set up with Solanum Dulcamare plants. The results showed a significant difference in ABA response between genotypes from a dry and a wet environment, and this response was also reflected in the root water uptake. Adaptive responses may have consequences for the way species are currently being treated in models (single plant to global scale). In particular, model parameters that control root water uptake and plant transpiration are generally assumed to be a property of the plant

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

    NASA Astrophysics Data System (ADS)

    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

    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

  6. Assimilation of Remotely Sensed Soil Moisture and Vegetation with a Crop Simulation Model

    NASA Astrophysics Data System (ADS)

    Ines, A. V. M.; Das, N. N.

    2015-12-01

    When a crop model is used to predict crop yields early in the growing season, two sources of uncertainties prevail those coming from climate and model uncertainties. Climate uncertainty is greatest early in the growing season and tends to decrease as weather data become available in the growing season. Model uncertainty due to errors in model structure, modeling assumptions and other ancillary data, generally remains constant through the growing season. Skillful climate forecasts can reduce climate uncertainty especially at the earlier stages of the growing season, while assimilating remote sensing (RS) data within the growing season can reduced model uncertainty. In this talk, we focus on the development, application and verification of a crop modeling-data assimilation framework capable of ingesting RS soil moisture and vegetation parameters, in this case, leaf area index for predicting aggregated crop yields. We discuss the lessons learned from our case studies in Iowa, with more homogenous rainfed agricultural system, and Georgia, more heterogeneous mixed rainfed/irrigated agricultural system. One of our goals is to show the utility of better soil moisture products, e.g. from SMAP, for improving the prediction of agricultural/hydrological variables with actionable lead-times.

  7. Radar for Measuring Soil Moisture Under Vegetation

    NASA Technical Reports Server (NTRS)

    Moghaddam, Mahta; Moller, Delwyn; Rodriguez, Ernesto; Rahmat-Samii, Yahya

    2004-01-01

    A two-frequency, polarimetric, spaceborne synthetic-aperture radar (SAR) system has been proposed for measuring the moisture content of soil as a function of depth, even in the presence of overlying vegetation. These measurements are needed because data on soil moisture under vegetation canopies are not available now and are necessary for completing mathematical models of global energy and water balance with major implications for global variations in weather and climate.

  8. Soil carbon response to land-use change: evaluation of a global vegetation model using observational meta-analyses

    NASA Astrophysics Data System (ADS)

    Nyawira, Sylvia S.; Nabel, Julia E. M. S.; Don, Axel; Brovkin, Victor; Pongratz, Julia

    2016-10-01

    Global model estimates of soil carbon changes from past land-use changes remain uncertain. We develop an approach for evaluating dynamic global vegetation models (DGVMs) against existing observational meta-analyses of soil carbon changes following land-use change. Using the DGVM JSBACH, we perform idealized simulations where the entire globe is covered by one vegetation type, which then undergoes a land-use change to another vegetation type. We select the grid cells that represent the climatic conditions of the meta-analyses and compare the mean simulated soil carbon changes to the meta-analyses. Our simulated results show model agreement with the observational data on the direction of changes in soil carbon for some land-use changes, although the model simulated a generally smaller magnitude of changes. The conversion of crop to forest resulted in soil carbon gain of 10 % compared to a gain of 42 % in the data, whereas the forest-to-crop change resulted in a simulated loss of -15 % compared to -40 %. The model and the observational data disagreed for the conversion of crop to grasslands. The model estimated a small soil carbon loss (-4 %), while observational data indicate a 38 % gain in soil carbon for the same land-use change. These model deviations from the observations are substantially reduced by explicitly accounting for crop harvesting and ignoring burning in grasslands in the model. We conclude that our idealized simulation approach provides an appropriate framework for evaluating DGVMs against meta-analyses and that this evaluation helps to identify the causes of deviation of simulated soil carbon changes from the meta-analyses.

  9. Soil Moisture and Vegetation Controls on Surface Energy Balance Using the Maximum Entropy Production Model of Evapotranspiration

    NASA Astrophysics Data System (ADS)

    Wang, J.; Parolari, A.; Huang, S. Y.

    2014-12-01

    The objective of this study is to formulate and test plant water stress parameterizations for the recently proposed maximum entropy production (MEP) model of evapotranspiration (ET) over vegetated surfaces. . The MEP model of ET is a parsimonious alternative to existing land surface parameterizations of surface energy fluxes from net radiation, temperature, humidity, and a small number of parameters. The MEP model was previously tested for vegetated surfaces under well-watered and dry, dormant conditions, when the surface energy balance is relatively insensitive to plant physiological activity. Under water stressed conditions, however, the plant water stress response strongly affects the surface energy balance. This effect occurs through plant physiological adjustments that reduce ET to maintain leaf turgor pressure as soil moisture is depleted during drought. To improve MEP model of ET predictions under water stress conditions, the model was modified to incorporate this plant-mediated feedback between soil moisture and ET. We compare MEP model predictions to observations under a range of field conditions, including bare soil, grassland, and forest. The results indicate a water stress function that combines the soil water potential in the surface soil layer with the atmospheric humidity successfully reproduces observed ET decreases during drought. In addition to its utility as a modeling tool, the calibrated water stress functions also provide a means to infer ecosystem influence on the land surface state. Challenges associated with sampling model input data (i.e., net radiation, surface temperature, and surface humidity) are also discussed.

  10. 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)

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

    2011-12-01

    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

  11. Modeled Impacts of Cover Crops and Vegetative Barriers on Corn Stover Availability and Soil Quality

    SciTech Connect

    Ian J. Bonner; David J. Muth Jr.; Joshua B. Koch; Douglas L. Karlen

    2014-06-01

    Environmentally benign, economically viable, and socially acceptable agronomic strategies are needed to launch a sustainable lignocellulosic biofuel industry. Our objective was to demonstrate a landscape planning process that can ensure adequate supplies of corn (Zea mays L.) stover feedstock while protecting and improving soil quality. The Landscape Environmental Assessment Framework (LEAF) was used to develop land use strategies that were then scaled up for five U.S. Corn Belt states (Nebraska, Iowa, Illinois, Indiana, and Minnesota) to illustrate the impact that could be achieved. Our results show an annual sustainable stover supply of 194 million Mg without exceeding soil erosion T values or depleting soil organic carbon [i.e., soil conditioning index (SCI)?>?0] when no-till, winter cover crop, and vegetative barriers were incorporated into the landscape. A second, more rigorous conservation target was set to enhance soil quality while sustainably harvesting stover. By requiring erosion to be <1/2 T and the SCI-organic matter (OM) subfactor to be >?0, the annual sustainable quantity of harvestable stover dropped to148 million Mg. Examining removal rates by state and soil resource showed that soil capability class and slope generally determined the effectiveness of the three conservation practices and the resulting sustainable harvest rate. This emphasizes that sustainable biomass harvest must be based on subfield management decisions to ensure soil resources are conserved or enhanced, while providing sufficient biomass feedstock to support the economic growth of bioenergy enterprises.

  12. Anthropogenic soil erosion over the Holocene: Application of a new dynamic soils module for global vegetation models

    NASA Astrophysics Data System (ADS)

    Kaplan, J. O.; Vanwalleghem, T.

    2012-04-01

    Over the course of the Holocene, anthropogenic activities have transformed the surface of the Earth. In no way has human impact been more important or longer lasting than the transformation of soils, where erosion and sediment transport over the past 10,000 years have led to irreversible changes in landscapes. Soil erosion also affected global carbon and nutrient cycles, and could have amplified or attenuated ongoing changes in the Earth's climate. To quantify the role of anthropogenically induced soil development and erosion in the Earth system, we developed a new module of global soil dynamics: soil formation, erosion, and sediment transport, that is suitable for global application at 0.5° resolution. We incorporated this soil module into the LPJ-DGVM and performed a series of simulations to quantify the spatial and temporal pattern of global soil change over the Holocene. The soil formation module models bedrock-to-soil conversion rates as exponentially decreasing with soil depth. Parameters for soil formation in different geological units were extracted from a review of existing literature. Our global soil erosion formulation is based on the Revised Universal Soil Loss Equation (RUSLE), but importantly accounts for sediment deposition and the net export of sediment out of a relatively large and geomorphologically heterogeneous gridcell. Our new module was developed by running the detailed soil erosion-deposition model WaTEM/SEDEM at 3 arc-second resolution to derive generalized topographical scaling relations that accurately represent hillslope length, slope gradient and sediment delivery ratio. We show that, at large spatial scale, sediment delivery ratio and the area affected by sediment deposition can be easily estimated from topographical parameters such as mean LS factor and wetness index. We include the feedback between soil formation and soil erosion by adjusting the soil erosion rates for soil depth and stoniness. The results of our Holocene

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

    NASA Technical Reports Server (NTRS)

    Gillies, Robert R.; Carlson, Toby N.

    1995-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-06-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

    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.

  16. Optimality and soil water-vegetation dynamics

    NASA Astrophysics Data System (ADS)

    Schymanski, S. J.

    2007-12-01

    Soil moisture is an important factor for nearly all hydrological and biogeochemical processes. Antecedent soil moisture impacts on infiltration and runoff generation, the soil moisture distribution within the soil together with other factors determines the soil carbon and nutrient cycling and the amount of soil moisture within the rooting zone often constitutes a major constraint for plant growth and evapo-transpiration. The main processes determining soil moisture dynamics are infiltration, percolation, evaporation and root water uptake. Therefore, modelling soil moisture dynamics requires an interdisciplinary approach that links hydrological and biological processes. Previous approaches treat either root water uptake rates or root distributions and transpiration rates as a given, and calculate the soil moisture dynamics based on the theory of flow in unsaturated media. The present study introduces a different approach to linking soil water and vegetation dynamics, based on optimality. Assuming that plants aim at minimising the costs related to the maintenance of the root system while meeting their demand for water, a model was formulated that dynamically adjusts the vertical root distribution in the soil profile to meet this objective. The model was used to compute the soil moisture dynamics in a tropical savanna over 12 months, which showed a better resemblance with the observed time series of surface soil moisture than models based on fixed root distributions. The optimality-based approach to modelling soil-vegetation interactions requires a new level of interdisciplinary synthesis, as biological and hydrological knowledge needs to be combined to derive the very basis of the model, namely the costs and benefits of different root properties. On the other hand, this approach has the potential to reduce the number of unknowns in a model (e.g. the vertical root distribution), which makes it a valuable alternative to more empirically-based approaches.

  17. Representing the effects of alpine grassland vegetation cover on the simulation of soil thermal dynamics by ecosystem models applied to the Qinghai-Tibetan Plateau

    USGS Publications Warehouse

    Yi, S.; Li, N.; Xiang, B.; Wang, X.; Ye, B.; McGuire, A.D.

    2013-01-01

    Soil surface temperature is a critical boundary condition for the simulation of soil temperature by environmental models. It is influenced by atmospheric and soil conditions and by vegetation cover. In sophisticated land surface models, it is simulated iteratively by solving surface energy budget equations. In ecosystem, permafrost, and hydrology models, the consideration of soil surface temperature is generally simple. In this study, we developed a methodology for representing the effects of vegetation cover and atmospheric factors on the estimation of soil surface temperature for alpine grassland ecosystems on the Qinghai-Tibetan Plateau. Our approach integrated measurements from meteorological stations with simulations from a sophisticated land surface model to develop an equation set for estimating soil surface temperature. After implementing this equation set into an ecosystem model and evaluating the performance of the ecosystem model in simulating soil temperature at different depths in the soil profile, we applied the model to simulate interactions among vegetation cover, freeze-thaw cycles, and soil erosion to demonstrate potential applications made possible through the implementation of the methodology developed in this study. Results showed that (1) to properly estimate daily soil surface temperature, algorithms should use air temperature, downward solar radiation, and vegetation cover as independent variables; (2) the equation set developed in this study performed better than soil surface temperature algorithms used in other models; and (3) the ecosystem model performed well in simulating soil temperature throughout the soil profile using the equation set developed in this study. Our application of the model indicates that the representation in ecosystem models of the effects of vegetation cover on the simulation of soil thermal dynamics has the potential to substantially improve our understanding of the vulnerability of alpine grassland ecosystems to

  18. Assimilation of SMOS-derived soil moisture in a fully integrated hydrological and soil-vegetation-atmosphere transfer model in Western Denmark

    NASA Astrophysics Data System (ADS)

    Ridler, Marc-Etienne; Madsen, Henrik; Stisen, Simon; Bircher, Simone; Fensholt, Rasmus

    2014-11-01

    Real surface soil moisture retrieved from the Soil Moisture and Ocean Salinity (SMOS) satellite is downscaled and assimilated in a fully integrated hydrological and soil-vegetation-atmosphere transfer (MIKE SHE SW-ET) model using a bias aware ensemble transform Kalman filter (Bias-ETKF). Satellite-derived soil moisture assimilation in a catchment scale model is typically restricted by two challenges: (1) passive microwave is too coarse for direct assimilation and (2) the data tend to be biased. The solution proposed in this study is to disaggregate the SMOS bias using a higher resolution land cover classification map that was derived from Landsat thermal images. Using known correlations between SMOS bias and vegetation type, the assimilation filter is adapted to calculate biases online, using an initial bias estimate. Real SMOS-derived soil moisture is assimilated in a precalibrated catchment model in Denmark. The objective is to determine if any additional gains can be achieved by SMOS surface soil moisture assimilation beyond the optimized model. A series of assimilation experiments were designed to (1) determine how effectively soil moisture corrections propagate downward in the soil column, (2) compare the efficacy of in situ versus SMOS assimilation, and (3) determine how soil moisture assimilation affects fluxes and discharge in the catchment. We find that assimilation of SMOS improved R2 soil moisture correlations in the upper 5 cm compared to a network of 30 in situ sensors for most land cover classes. Assimilation also brought modest gains in R2 at 25 cm depth but slightly degraded the correlation at 50 cm depth. Assimilation overcorrected discharge peaks.

  19. Sensitivity analysis of a soil-vegetation-atmosphere transfer (SVAT) model parameterised for a British floodplain meadow

    NASA Astrophysics Data System (ADS)

    Morris, P. J.; Verhoef, A.; Van der Tol, C.; Macdonald, D.

    2011-12-01

    Rationale: Floodplain meadows are highly species-rich grassland ecosystems, unique in that their vegetation and soil structures have been shaped and maintained by ~1,000 yrs of traditional, low-intensity agricultural management. Widespread development on floodplains over the last two centuries has left few remaining examples of these once commonplace ecosystems and they are afforded high conservation value by British and European agencies. Increased incidences and severity of summer drought and winter flooding in Britain in recent years have placed floodplain plant communities under stress through altered soil moisture regimes. There is a clear need for improved management strategies if the last remaining British floodplain meadows are to be conserved under changing climates. Aim: As part of the Floodplain Underground Sensors Experiment (FUSE, a 3-year project funded by the Natural Environment Research Council) we aim to understand the environmental controls over soil-vegetation-atmosphere transfers (SVAT) of water, CO2 and energy at Yarnton Mead, a floodplain meadow in southern England. An existing model, SCOPE (Soil Canopy Observation, Photochemistry and Energy fluxes; van der Tol et al., 2009), uses remotely-sensed infrared radiance spectra to predict heat and water transfers between a vegetation canopy and the atmosphere. We intend to expand SCOPE by developing a more realistic, physically-based representation of water, gas and energy transfers between soil and vegetation. This improved understanding will eventually take the form of a new submodel within SCOPE, allowing more rigorous estimation of soil-canopy-atmosphere exchanges for the site using predominantly remotely-sensed data. In this context a number of existing SVAT models will be tested and compared to ensure that only reliable and robust underground model components will be coupled to SCOPE. Approach: For this study, we parameterised an existing and widely-used SVAT model (CoupModel; Jansson, 2011

  20. A comparison of simulation models for predicting soil water dynamics in bare and vegetated lysimeters

    SciTech Connect

    Link, S.O.; Kickert, R.N.; Fayer, M.J.; Gee, G.W.

    1993-06-01

    This report describes the results of simulation models used to predict soil water storage dynamics at the Field Lysimeter Test Facility (FLTF) weighing lysimeters. The objectives of this research is to develop the capability to predict soil water storage dynamics with plants in support of water infiltration control studies for the Hanford Permanent Isolation Barrier Development Program. It is important to gain confidence in one`s ability to simulate soil water dynamics over long time periods to assess the barrier`s ability to prevent drainage. Two models were compared for their ability to simulate soil water storage dynamics with and without plants in weighing lysimeters, the soil water infiltration and movement (SWIM) and the simulation of production and utilization of rangelands (SPUR-91) models. These models adequately simulated soil water storage dynamics for the weighing lysimeters. The range of root mean square error values for the two models was 7.0 to 19.8. This compares well with the range reported by Fayer et al. (1992) for the bare soil data sets of 8.1 to 22.1. Future research will test the predictive capability of these models for longer term lysimeter data sets and for historical data sets collected in various plant community types.

  1. How to upscale the coupling between hydrology and vegetation at the hillslope scale with an equivalent soil-vegetation column model

    NASA Astrophysics Data System (ADS)

    Maquin, Mathilde; Mugler, Claude; Mouche, Emmanuel; Ducharne, Agnès

    2014-05-01

    Three-dimensional watershed models coupled with land surface models have demonstrated the control of soil moisture over land energy fluxes, as evaporation and transpiration (Maxwell and Kollet, Nature Geoscience, 2008; Condon et al., Advances in Water Resources, 2013). However, due to computational costs, these fully integrated watershed models cannot be used at larger scales. Upscaling hydrological models can be an alternative to take into account the impact of groundwater hydrology on land energy fluxes at various scales. In this purpose, we propose a two-step upscaling methodology aiming to replace a hillslope model by an equivalent vertical soil column model suitable for land surface modelling. The hillslope reference model is based on a two-dimensional aquifer model (resolution of Richards' equation) combined with a representation of vegetation and climate forcing as boundary condition. In this system, two main hydrological processes corresponding to different time scales have to be distinguished: the vertical water transfer from roots to the atmosphere through the vegetation, and the longitudinal flow of the aquifer to the stream. In an upscaling approach, two options can be considered: one may accurately model the aquifer longitudinal flow but with a degraded model of vertical transfer, or inversely give a preferential treatment to the vertical flow. As the exchanges between soil, vegetation and atmosphere are strongly dependent on the vertical profile of water (through the distribution of roots), the second option appears to be more adapted to our objective which is the assessment of hillslope hydrology on land surface fluxes. In the first step of our upscaling methodology, the two-dimensional reference hillslope is modelled as a set of one-dimensional independent vertical soil vegetation columns. In each of them, Richards' equation is solved in the vertical direction, the representation of roots and climate forcing remaining unchanged. Moreover, a sink

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

    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

  3. Mapping SOC (Soil Organic Carbon) using LiDAR-derived vegetation indices in a random forest regression model

    NASA Astrophysics Data System (ADS)

    Will, R. M.; Glenn, N. F.; Benner, S. G.; Pierce, J. L.; Spaete, L.; Li, A.

    2015-12-01

    Quantifying SOC (Soil Organic Carbon) storage in complex terrain is challenging due to high spatial variability. Generally, the challenge is met by transforming point data to the entire landscape using surrogate, spatially-distributed, variables like elevation or precipitation. In many ecosystems, remotely sensed information on above-ground vegetation (e.g. NDVI) is a good predictor of below-ground carbon stocks. In this project, we are attempting to improve this predictive method by incorporating LiDAR-derived vegetation indices. LiDAR provides a mechanism for improved characterization of aboveground vegetation by providing structural parameters such as vegetation height and biomass. In this study, a random forest model is used to predict SOC using a suite of LiDAR-derived vegetation indices as predictor variables. The Reynolds Creek Experimental Watershed (RCEW) is an ideal location for a study of this type since it encompasses a strong elevation/precipitation gradient that supports lower biomass sagebrush ecosystems at low elevations and forests with more biomass at higher elevations. Sagebrush ecosystems composed of Wyoming, Low and Mountain Sagebrush have SOC values ranging from .4 to 1% (top 30 cm), while higher biomass ecosystems composed of aspen, juniper and fir have SOC values approaching 4% (top 30 cm). Large differences in SOC have been observed between canopy and interspace locations and high resolution vegetation information is likely to explain plot scale variability in SOC. Mapping of the SOC reservoir will help identify underlying controls on SOC distribution and provide insight into which processes are most important in determining SOC in semi-arid mountainous regions. In addition, airborne LiDAR has the potential to characterize vegetation communities at a high resolution and could be a tool for improving estimates of SOC at larger scales.

  4. Application of Distributed Hydrology-Soil-Vegetation Model in Pang Khum Experimental Watershed, Chiang Mai Province, Thailand

    NASA Astrophysics Data System (ADS)

    Cuo, L.; Giambelluca, T. W.; Ziegler, A. D.; Sutherland, R. A.; Nullet, M. A.; Larkin, E. D.; Vana, T. T.

    2001-12-01

    Distributed hydrology-soil-vegetation model (DHSVM) uses a digital elevation model (DEM) and accounts for topographic effects on soil moisture, groundwater, and surface water redistribution in a complex terrain. In this study, DHSVM is used to simulate soil moisture, net radiation and stream flow in a 1-km2 tropical mountainous watershed in Pang Khum, Chang Mai, Thailand. Pang Khum Experimental Watershed (PKEW) has two meteorological stations, four soil moisture stations, and one stream flow station at basin outlet. Meteorological measurements are used as forcing data for DHSVM. The grid resolution for this simulation is 50 m. Initial soil and vegetation parameter settings based on field measurements and literature review are adjusted through model calibration. The model is run for a six month warm-up period, followed by a calibration period of approximately one year. Validation is done for two periods totaling 18 months. At the forested site, net radiation is reasonably well simulated, although underestimated in the dry season, and overestimated in the wet season. At the agricultural site, net radiation is consistently overestimated. Soil moisture is well simulated at the forest site. In the simulation, the water table rises into the soil zone during the wet season, saturating all three soil layers at the agricultural site; measured values remained at unsaturated levels. Baseflow is significantly underestimated in calibration and validation periods. Difficulty in simulating streamflow may be caused by road-related effects in the basin. Our prior field work has shown that the road significantly alters runoff in PKEW. The principal mechanism of road-induced effects is Horton Overland Flow (HOF) generated on the road surface. In its present form DHSVM can account for interception of subsurface flow by roads, but not HOF generated on the road. We do not think subsurface flow interception is important in PKEW, and have therefore not implemented the road in our

  5. Process-based modeling of vegetation dynamics, snow, evapotranspiration and soil moisture patterns in an alpine catchment

    NASA Astrophysics Data System (ADS)

    Bertoldi, Giacomo; Della Chiesa, Stefano; Engel, Michael; Niedrist, Georg; Brenner, Johannes G.; Endrizzi, Stefano; Dall'Amico, Matteo; Cordano, Emanuele; Tappeiner, Ulrike; Rigon, Riccardo

    2014-05-01

    Mountain regions are particularly sensitive to climate change and at the same time they represent a key water resource not only locally but as well for lowland areas. Because of the complexity of mountain landscapes and the high climatic variability at a local scale, detailed quantification of key water budget components as snow cover, soil moisture and groundwater recharge is required. Therefore, there is a strong need to improve the capability of hydrological models to identify patterns in complex terrain (i.e. when variability of spatial characteristics counts), and to quantify changes of the water cycle components explicitly, considering interactions and feedbacks with climate and vegetation. Process-based hydrological models represent promising tools for addressing those needs. However, even if their inherent complexity sometimes limits their applicability for operational purpose, they offer great potential in terms of tools to test hypotheses, which can be verified in the field. GEOtop is a hydrological model that calculates the energy and mass exchanges between soil, vegetation, and atmosphere, accounting for land cover, water redistribution, snow processes, glacier mass budget and the effects of complex terrain and thus is one of the few models that was built with this complexity in mind. Recently, it has also been coupled with a dynamic vegetation model in order to simulate alpine grassland ecosystems. In this contribution, we want to present an application of the GEOtop model in simulating above ground biomass (Bag) production, evapotranspiration (ET), soil moisture (SM) and snow water equivalent (SWE) patterns for a catchment of about 100 km2, located in the Venosta/Vinschgau valley in the European Alps. Despite the Alps are one of the 'water towers of Europe', water scarcity issues can affect the region where the model is applied, and an intensive hydrological and ecological monitoring activity with ground observations and remote-sensing products has

  6. Parametrizing soil-vegetation-atmosphere transfer models with non-destructive and high resolution stable isotope data

    NASA Astrophysics Data System (ADS)

    Rothfuss, Youri; Vereecken, Harry; Brüggemann, Nicolas

    2015-04-01

    For nearly 50 years, stable isotopologues of water (1H2H16O and 1H218O) have been used in a wide range of water research disciplines to identify the origin and to quantify proportions of water pools involved in processes of the terrestrial water cycle. In soils between rain events, the combined action of convective capillary rise of water depleted in 1H2H16O and 1H218O with back-diffusion of water enriched in 1H2H16O and 1H218O from the evaporation site (i.e., soil surface or evaporation front) downwards leads to the formation of - typically exponential - soil water stable isotopologue profiles. The first steady state and isothermal analytical solutions of these isotopologues profiles were proposed in the late 60ies. They were later extended to unsteady state and non-isothermal conditions. These analytical formulations link the shape of the isotopologue profiles to soil evaporation flux and regime, and to the soil physical properties associated with both diffusive and convective water transport (such as tortuosity length and dispersivity). More recently, the movement of 1H2H16O and 1H218O was implemented in physically-based numerical soil-vegetation-atmosphere transfer (SVAT) models (e.g., TOUGHREACT, SiSPAT-Isotope, Soil-Litter iso, Hydrus 1D). In these fully coupled models, the output of the heat transfer module, i.e., the temperature profile, is fed into the isotope module. Isotope and water transport are therefore inter-dependent as opposed to analytical solutions. In addition to thermodynamic (equilibrium) isotope effects, which are only temperature-dependent, kinetic isotope effects during soil evaporation greatly affect the stable isotopic composition of soil water and evaporation and can be highly variable. Thus, a better understanding of the implications of these kinetic effects in addition to the well characterized equilibrium effects as well as their implementation in SVAT models are required for improving the use of 1H2H16O and 1H218O as tracers of soil

  7. Modeling hydrological process in a glacier basin on the central Tibetan Plateau with a distributed hydrology soil vegetation model

    NASA Astrophysics Data System (ADS)

    Zhang, Guoshuai; Kang, Shichang; Cuo, Lan; Qu, Bin

    2016-08-01

    A mass and energy balance-based glacier melt module was coupled with the spatially distributed hydrological soil vegetation model and used to simulate the basin-scale water and energy balance in the Zhadang glacier basin. Observed hourly meteorological data from 2011 to 2014 were used as model forcing data. The basin-scale simulations were evaluated at both the point and areal scales using albedo, temperature, and height change on the glacier surface, as well as the mass balance and streamflow of the whole basin. The analysis showed that the model could effectively reproduce the key elements of the energy and mass balance of the Zhadang basin. The analysis demonstrates that radiation was the most important energy component accounting for 80% of total surface energy. On average, glacier runoff contributed to 64% of the total basin discharge during the study period. The overall streamflow was controlled by the glacier mass balance in 2012 and 2014, while temperature and precipitation affected hydrological processes the most during 2011 and 2013. Both high temperature and precipitation resulted in high total basin streamflow but via different mechanisms. High temperatures increase glacier mass loss and glacier melt runoff, whereas high precipitation decreases glacier melt runoff but produces high runoff in nonglacier areas. The early onset of the Indian monsoon with high snowfall reduces glacier surface melt but sustains basin discharge, positively affecting for water resources.

  8. Preliminary assessment of soil moisture over vegetation

    NASA Technical Reports Server (NTRS)

    Carlson, T. N.

    1986-01-01

    Modeling of surface energy fluxes was combined with in-situ measurement of surface parameters, specifically the surface sensible heat flux and the substrate soil moisture. A vegetation component was incorporated in the atmospheric/substrate model and subsequently showed that fluxes over vegetation can be very much different than those over bare soil for a given surface-air temperature difference. The temperature signatures measured by a satellite or airborne radiometer should be interpreted in conjunction with surface measurements of modeled parameters. Paradoxically, analyses of the large-scale distribution of soil moisture availability shows that there is a very high correlation between antecedent precipitation and inferred surface moisture availability, even when no specific vegetation parameterization is used in the boundary layer model. Preparatory work was begun in streamlining the present boundary layer model, developing better algorithms for relating surface temperatures to substrate moisture, preparing for participation in the French HAPEX experiment, and analyzing aircraft microwave and radiometric surface temperature data for the 1983 French Beauce experiments.

  9. Intermediately complex models for the hydrological interactions in the atmosphere-vegetation-soil system

    NASA Astrophysics Data System (ADS)

    Zeng, X. D.; Wang, A. H.; Zeng, Q. C.; Dickinson, R. E.; Zeng, X. B.; Shen, S. S. P.

    2006-01-01

    This paper investigates the hydrological interactions in the atmosphere-evegetation-soil system by using the bucket model and several new simplified intermediately complex models. The results of mathematical analysis and numerical simulations show that these models, despite their simplicity, can very clearly reveal the essential features of the rather complex hydrological system of atmosphere-ecosystem-soil. For given atmospheric variables, these models clearly demonstrate multiple timescales, the "red shift" of response spectra, multi-equilibria and limit cycles, bifurcation, abrupt change, self-organization, recovery, "desertification", and chaos. Most of these agree with observations. Especially, the weakening of "shading effect" of living canopy and the wilted biomass might be a major mechanism leading to the desertification in a relatively short period due to overgrazing, and the desertification in a relatively long period or in climate of change might be due to both Charney's mechanism and the shading effect. These ideas could be validated with further numerical simulations. In the paper, some methods for improving the estimation of timescales in the soil water evolution responding to the forcing are also proposed.

  10. Application of the ORCHIDEE global vegetation model to evaluate biomass and soil carbon stocks of Qinghai-Tibetan grasslands

    NASA Astrophysics Data System (ADS)

    Tan, Kun; Ciais, Philippe; Piao, Shilong; Wu, Xiaopu; Tang, Yanhong; Vuichard, Nicolas; Liang, Shuang; Fang, Jingyun

    2010-03-01

    The cold grasslands of the Qinghai-Tibetan Plateau form a globally significant biome, which represents 6% of the world's grasslands and 44% of China's grasslands. Yet little is known about carbon cycling in this biome. In this study, we calibrated and applied a process-based ecosystem model called Organizing Carbon and Hydrology in Dynamic Ecosystems (ORCHIDEE) to estimate the C fluxes and stocks of these grasslands. First, the parameterizations of ORCHIDEE were improved and calibrated against multiple time-scale and spatial-scale observations of (1) eddy-covariance fluxes of CO2 above one alpine meadow site; (2) soil temperature collocated with 30 meteorological stations; (3) satellite leaf area index (LAI) data collocated with the meteorological stations; and (4) soil organic carbon (SOC) density profiles from China's Second National Soil Survey. The extensive SOC survey data were used to extrapolate local fluxes to the entire grassland biome. After calibration, we show that ORCHIDEE can successfully capture the seasonal variation of net ecosystem exchange (NEE), as well as the LAI and SOC spatial distribution. We applied the calibrated model to estimate 0.3 Pg C yr-1 (1 Pg = 1015 g) of total annual net primary productivity (NPP), 0.4 Pg C of vegetation total biomass (aboveground and belowground), and 12 Pg C of SOC stocks for Qinghai-Tibetan grasslands covering an area of 1.4 × 106 km2. The mean annual NPP, vegetation biomass, and soil carbon stocks decrease from the southeast to the northwest, along with precipitation gradients. Our results also suggest that in response to an increase of temperature by 2°C, approximately 10% of current SOC stocks in Qinghai-Tibetan grasslands could be lost, even though NPP increases by about 9%. This result implies that Qinghai-Tibetan grasslands may be a vulnerable component of the terrestrial carbon cycle to future climate warming.

  11. Thallium contamination of soils/vegetation as affected by sphalerite weathering: a model rhizospheric experiment.

    PubMed

    Vaněk, Aleš; Grösslová, Zuzana; Mihaljevič, Martin; Ettler, Vojtěch; Chrastný, Vladislav; Komárek, Michael; Tejnecký, Václav; Drábek, Ondřej; Penížek, Vít; Galušková, Ivana; Vaněčková, Barbora; Pavlů, Lenka; Ash, Christopher

    2015-01-01

    The environmental stability of Tl-rich sphalerite in two contrasting soils was studied. Rhizospheric conditions were simulated to assess the risk associated with sulfide microparticles entering agricultural (top)soils. The data presented here clearly demonstrate a significant effect of 500 μM citric acid, a model rhizospheric solution, on ZnS alteration followed by enhanced Tl and Zn release. The relative ZnS mass loss after 28 days of citrate incubation reached 0.05 and 0.03 wt.% in Cambisol and Leptosol samples respectively, and was up to 4 times higher, compared to H2O treatments. Incongruent (i.e., substantially increased) mobilization of Tl from ZnS was observed during the incubation time. Generally higher (long-term) stability of ZnS with lower Tl release is predicted for soils enriched in carbonates. Furthermore, the important role of silicates (mainly illite) in the stabilization of mobilized Tl, linked with structural (inter)layer Tl-K exchange, is suggested. Thallium was highly bioavailable, as indicated by its uptake by white mustard; maximum Tl amounts were detected in biomass grown on the acidic Cambisol. Despite the fact that sulfides are thought as relatively stable phases in soil environments, enhanced sulfide dissolution and Tl/trace element release (and bioaccumulation) can be assumed in rhizosphere systems.

  12. Vegetative soil covers for hazardous waste landfills

    NASA Astrophysics Data System (ADS)

    Peace, Jerry L.

    Shallow land burial has been the preferred method for disposing of municipal and hazardous wastes in the United States because it is the simplest, cheapest, and most cost-effective method of disposal. Arid and semiarid regions of the western United States have received considerable attention over the past two decades in reference to hazardous, radioactive, and mixed waste disposal. Disposal is based upon the premise that low mean annual precipitation, high evapotranspiration, and low or negligible recharge, favor waste isolation from the environment for long periods of time. The objective of this study is to demonstrate that containment of municipal and hazardous wastes in arid and semiarid environments can be accomplished effectively without traditional, synthetic materials and complex, multi-layer systems. This research demonstrates that closure covers utilizing natural soils and native vegetation i.e., vegetative soil covers, will meet the technical equivalency criteria prescribed by the U.S. Environmental Protection Agency for hazardous waste landfills. Vegetative soil cover design combines layers of natural soil, native plant species, and climatic conditions to form a sustainable, functioning ecosystem that maintains the natural water balance. 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 from 1919 to 1996 are used to simulate percolation through the natural analogue and an engineered cover, with and without vegetation. This study indicates that a 1 m (3 ft) cover is the minimum design thickness necessary to meet the U.S. Environmental Protection Agency

  13. A method to downscale soil moisture to fine resolutions using topographic, vegetation, and soil data

    NASA Astrophysics Data System (ADS)

    Ranney, Kayla J.; Niemann, Jeffrey D.; Lehman, Brandon M.; Green, Timothy R.; Jones, Andrew S.

    2015-02-01

    Soil moisture can be estimated over large regions with spatial resolutions greater than 500 m, but many applications require finer resolutions (10-100 m). Several methods use topographic data to downscale, but vegetation and soil patterns can also be important. In this paper, a downscaling model that uses fine-resolution topographic, vegetation, and soil data is presented. The method is tested at the Cache la Poudre catchment where detailed vegetation and soil data were collected. Additional testing is performed at the Tarrawarra and Nerrigundah catchments where limited soil data are available. Downscaled soil moisture patterns at Cache la Poudre improve when vegetation and soil data are used, and model performance is similar to an EOF method. Using interpolated soil data at Tarrawarra and Nerrigundah decreases model performance and results in worse performance than an EOF method, suggesting that soil data needs greater spatial detail and accuracy to be useful for downscaling.

  14. 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)

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

    2013-12-01

    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

  15. Modeling vegetation rooting strategies on a hillslope

    NASA Astrophysics Data System (ADS)

    Sivandran, G.; Bras, R. L.

    2011-12-01

    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.

  16. Green vegetation, nonphotosynthetic vegetation, and soils in AVIRIS data

    NASA Technical Reports Server (NTRS)

    Roberts, D. A.; Smith, M. O.; Adams, J. B.

    1993-01-01

    The problem of distinguishing between green vegetation, nonphotosynthetic vegetation (NPV, such as dry grass, leaf litter, and woody material), and soils in imaging-spectrometer data is addressed by analyzing an image taken by the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) over the Jasper Ridge Biological Preserve (California) on September 20, 1989, using spectral mixture analysis. Over 98 percent of the spectral variation could be explained by linear mixtures of three endmembers, green vegetation, shade, and soil. NPV, which could not be distinguished from soil when included as an endmember, was discriminated by residual spectra that contained cellulose and lignin absorptions. Distinct communities of green vegetation were distinguished by (1) nonlinear mixing effect caused by transmission and scattering by green leaves, (2) variations in a derived canopy-shade spectrum, and (3) the fraction of NPV.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    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

  18. 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

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

    2014-01-01

    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.

  19. 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

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

    2014-01-01

    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

  20. Retrieving pace in vegetation growth using precipitation and soil moisture

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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

  1. Reflectance of vegetation, soil, and water

    NASA Technical Reports Server (NTRS)

    Wiegand, C. L. (Principal Investigator)

    1974-01-01

    The author has identified the following significant results. The Kubelka-Munk model, a regression model, and a combination of these models were used to extract plant, soil, and shadow reflectance components of vegetated surfaces. The combination model was superior to the others; it explained 86% of the variation in band 5 reflectance of corn and sorghum, and 90% of the variation in band 6 reflectance of cotton. A fractional shadow term substantially increased the proportion of the digital count sum of squares explained when plant parameters alone explained 85% or less of the variation. Overall recognition of 94 agricultural fields using simultaneously acquired aircraft and spacecraft MSS data was 61.8 and 62.8%, respectively; recognition of vegetable fields larger than 10 acres and taller than 25 cm, rose to 88.9 and 100% for aircraft and spacecraft, respectively. Agriculture and rangeland, were well discriminated for the entire county but level 2 categories of vegetables, citrus, and idle cropland, except for citrus, were not.

  2. Integrating models to simulate emergent behaviour: effects of organic matter on soil hydraulics in the ICZ-1D soil-vegetation model

    NASA Astrophysics Data System (ADS)

    Valstar, Johan; Rowe, Ed; Konstantina, Moirogiorgou; Giannakis, Giorgos; Nikolaidis, Nikolaos

    2014-05-01

    Soil develops as a result of interacting processes, many of which have been described in more or less detailed models. A key challenge in developing predictive models of soil function is to integrate processes that operate across a wide range of temporal and spatial scales. Many soil functions could be classified as "emergent", since they result from the interaction of subsystems. For example, soil organic matter (SOM) dynamics are commonly considered in relation to carbon storage, but can have profound effects on soil hydraulic properties that are conventionally considered to be static. Carbon fixed by plants enters the soil as litterfall, root turnover or via mycorrhizae. Plants need water and nutrients to grow, and an expanding root system provides access to a larger volume of soil for uptake of water and nutrients. Roots also provide organic exudates, such as oxalate, which increase nutrient availability. Carbon inputs are transformed at various rates into soil biota, CO2, and more persistent forms of organic matter. The SOM is partly taken up into soil aggregates of variable sizes, which slows down degradation. Water availability is an important factor as both plant growth and SOM degradation can be limited by shortage of water. Water flow is the main driver for transport of nutrients and other solutes. The flow of water in turn is influenced by the presence of SOM as this influences soil water retention and hydraulic conductivity. Towards the top of the unsaturated zone, bioturbation by the soil fauna transports both solid material and solutes. Weathering rates of minerals determine the availability of many nutrients and are in turn dependent on parameters such as pH, water content, CO2 pressure and oxalate concentration. Chemical reactions between solutes, dissolution and precipitation, and exchange on adsorption sites further influence solute concentrations. Within the FP7 SoilTrEC project, we developed a model that incorporates all of these processes, to

  3. Vegetation management with fire modifies peatland soil thermal regime.

    PubMed

    Brown, Lee E; Palmer, Sheila M; Johnston, Kerrylyn; Holden, Joseph

    2015-05-01

    Vegetation removal with fire can alter the thermal regime of the land surface, leading to significant changes in biogeochemistry (e.g. carbon cycling) and soil hydrology. In the UK, large expanses of carbon-rich upland environments are managed to encourage increased abundance of red grouse (Lagopus lagopus scotica) by rotational burning of shrub vegetation. To date, though, there has not been any consideration of whether prescribed vegetation burning on peatlands modifies the thermal regime of the soil mass in the years after fire. In this study thermal regime was monitored across 12 burned peatland soil plots over an 18-month period, with the aim of (i) quantifying thermal dynamics between burned plots of different ages (from <2 to 15 + years post burning), and (ii) developing statistical models to determine the magnitude of thermal change caused by vegetation management. Compared to plots burned 15 + years previously, plots recently burned (<2-4 years) showed higher mean, maximum and range of soil temperatures, and lower minima. Statistical models (generalised least square regression) were developed to predict daily mean and maximum soil temperature in plots burned 15 + years prior to the study. These models were then applied to predict temperatures of plots burned 2, 4 and 7 years previously, with significant deviations from predicted temperatures illustrating the magnitude of burn management effects. Temperatures measured in soil plots burned <2 years previously showed significant statistical disturbances from model predictions, reaching +6.2 °C for daily mean temperatures and +19.6 °C for daily maxima. Soil temperatures in plots burnt 7 years previously were most similar to plots burned 15 + years ago indicating the potential for soil temperatures to recover as vegetation regrows. Our findings that prescribed peatland vegetation burning alters soil thermal regime should provide an impetus for further research to understand the consequences of thermal regime

  4. Using Vegetation Maps to Provide Information on Soil Distribution

    NASA Astrophysics Data System (ADS)

    José Ibáñez, Juan; Pérez-Gómez, Rufino; Brevik, Eric C.; Cerdà, Artemi

    2016-04-01

    Many different types of maps (geology, hydrology, soil, vegetation, etc.) are created to inventory natural resources. Each of these resources is mapped using a unique set of criteria, including scales and taxonomies. Past research has indicated that comparing the results of different but related maps (e.g., soil and geology maps) may aid in identifying deficiencies in those maps. Therefore, this study was undertaken in the Almería Province (Andalusia, Spain) to (i) compare the underlying map structures of soil and vegetation maps and (ii) to investigate if a vegetation map can provide useful soil information that was not shown on a soil map. To accomplish this soil and vegetation maps were imported into ArcGIS 10.1 for spatial analysis. Results of the spatial analysis were exported to Microsoft Excel worksheets for statistical analyses to evaluate fits to linear and power law regression models. Vegetative units were grouped according to the driving forces that determined their presence or absence (P/A): (i) climatophilous (climate is the only determinant of P/A) (ii); lithologic-climate (climate and parent material determine PNV P/A); and (iii) edaphophylous (soil features determine PNV P/A). The rank abundance plots for both the soil and vegetation maps conformed to Willis or Hollow Curves, meaning the underlying structures of both maps were the same. Edaphophylous map units, which represent 58.5% of the vegetation units in the study area, did not show a good correlation with the soil map. Further investigation revealed that 87% of the edaphohygrophylous units (which demand more soil water than is supplied by other soil types in the surrounding landscape) were found in ramblas, ephemeral riverbeds that are not typically classified and mapped as soils in modern systems, even though they meet the definition of soil given by the most commonly used and most modern soil taxonomic systems. Furthermore, these edaphophylous map units tend to be islands of biodiversity

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

    NASA Astrophysics Data System (ADS)

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

    2010-09-01

    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".

  6. Regime shifts in models of dryland vegetation.

    PubMed

    Zelnik, Yuval R; Kinast, Shai; Yizhaq, Hezi; Bel, Golan; Meron, Ehud

    2013-12-13

    Drylands are pattern-forming systems showing self-organized vegetation patchiness, multiplicity of stable states and fronts separating domains of alternative stable states. Pattern dynamics, induced by droughts or disturbances, can result in desertification shifts from patterned vegetation to bare soil. Pattern formation theory suggests various scenarios for such dynamics: an abrupt global shift involving a fast collapse to bare soil, a gradual global shift involving the expansion and coalescence of bare-soil domains and an incipient shift to a hybrid state consisting of stationary bare-soil domains in an otherwise periodic pattern. Using models of dryland vegetation, we address the question of which of these scenarios can be realized. We found that the models can be split into two groups: models that exhibit multiplicity of periodic-pattern and bare-soil states, and models that exhibit, in addition, multiplicity of hybrid states. Furthermore, in all models, we could not identify parameter regimes in which bare-soil domains expand into vegetated domains. The significance of these findings is that, while models belonging to the first group can only exhibit abrupt shifts, models belonging to the second group can also exhibit gradual and incipient shifts. A discussion of open problems concludes the paper.

  7. Regime shifts in models of dryland vegetation.

    PubMed

    Zelnik, Yuval R; Kinast, Shai; Yizhaq, Hezi; Bel, Golan; Meron, Ehud

    2013-01-01

    Drylands are pattern-forming systems showing self-organized vegetation patchiness, multiplicity of stable states and fronts separating domains of alternative stable states. Pattern dynamics, induced by droughts or disturbances, can result in desertification shifts from patterned vegetation to bare soil. Pattern formation theory suggests various scenarios for such dynamics: an abrupt global shift involving a fast collapse to bare soil, a gradual global shift involving the expansion and coalescence of bare-soil domains and an incipient shift to a hybrid state consisting of stationary bare-soil domains in an otherwise periodic pattern. Using models of dryland vegetation, we address the question of which of these scenarios can be realized. We found that the models can be split into two groups: models that exhibit multiplicity of periodic-pattern and bare-soil states, and models that exhibit, in addition, multiplicity of hybrid states. Furthermore, in all models, we could not identify parameter regimes in which bare-soil domains expand into vegetated domains. The significance of these findings is that, while models belonging to the first group can only exhibit abrupt shifts, models belonging to the second group can also exhibit gradual and incipient shifts. A discussion of open problems concludes the paper.

  8. Spatial pattern formation of coastal vegetation in response to external gradients and positive feedbacks affecting soil porewater salinity: A model study

    USGS Publications Warehouse

    Jiang, J.; DeAngelis, D.L.; Smith, T. J.; Teh, S.Y.; Koh, H. L.

    2012-01-01

    Coastal vegetation of South Florida typically comprises salinity-tolerant mangroves bordering salinity-intolerant hardwood hammocks and fresh water marshes. Two primary ecological factors appear to influence the maintenance of mangrove/hammock ecotones against changes that might occur due to disturbances. One of these is a gradient in one or more environmental factors. The other is the action of positive feedback mechanisms, in which each vegetation community influences its local environment to favor itself, reinforcing the boundary between communities. The relative contributions of these two factors, however, can be hard to discern. A spatially explicit individual-based model of vegetation, coupled with a model of soil hydrology and salinity dynamics is presented here to simulate mangrove/hammock ecotones in the coastal margin habitats of South Florida. The model simulation results indicate that an environmental gradient of salinity, caused by tidal flux, is the key factor separating vegetation communities, while positive feedback involving the different interaction of each vegetation type with the vadose zone salinity increases the sharpness of boundaries, and maintains the ecological resilience of mangrove/hammock ecotones against small disturbances. Investigation of effects of precipitation on positive feedback indicates that the dry season, with its low precipitation, is the period of strongest positive feedback. ?? 2011 Springer Science+Business Media B.V. (outside the USA).

  9. Determining soil moisture and soil properties in vegetated areas by assimilating soil temperatures

    NASA Astrophysics Data System (ADS)

    Dong, Jianzhi; Steele-Dunne, Susan C.; Ochsner, Tyson E.; van de Giesen, Nick

    2016-06-01

    This study addresses two critical barriers to the use of Passive Distributed Temperature Sensing (DTS) for large-scale, high-resolution monitoring of soil moisture. In recent research, a particle batch smoother (PBS) was developed to assimilate sequences of temperature data at two depths into Hydrus-1D to estimate soil moisture as well as soil thermal and hydraulic properties. However, this approach was limited to bare soil and assumed that the cable depths were perfectly known. In order for Passive DTS to be more broadly applicable as a soil hydrology research and remote sensing soil moisture product validation tool, it must be applicable in vegetated areas. To address this first limitation, the forward model (Hydrus-1D) was improved through the inclusion of a canopy energy balance scheme. Synthetic tests were used to demonstrate that without the canopy energy balance scheme, the PBS estimated soil moisture could be even worse than the open loop case (no assimilation). When the improved Hydrus-1D model was used as the forward model in the PBS, vegetation impacts on the soil heat and water transfer were well accounted for. This led to accurate and robust estimates of soil moisture and soil properties. The second limitation is that, cable depths can be highly uncertain in DTS installations. As Passive DTS uses the downward propagation of heat to extract moisture-related variations in thermal properties, accurate estimates of cable depths are essential. Here synthetic tests were used to demonstrate that observation depths can be jointly estimated with other model states and parameters. The state and parameter results were only slightly poorer than those obtained when the cable depths were perfectly known. Finally, in situ temperature data from four soil profiles with different, but known, soil textures were used to test the proposed approach. Results show good agreement between the observed and estimated soil moisture, hydraulic properties, thermal properties, and

  10. Correspondence between vegetation and soils in wetlands and nearby uplands

    USGS Publications Warehouse

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

    1989-01-01

    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.

  11. Soil Moisture Prediction in the Soil, Vegetation and Snow (SVS) Scheme

    NASA Astrophysics Data System (ADS)

    Alavi, Nasim; Bélair, Stéphane; Fortin, Vincent; Zhang, Shunli; Husain, Syed; Carrera, Marco; Abrahamowicz, Maria

    2016-04-01

    A new land surface scheme has been developed at Environment of Canada to provide surface fluxes of momentum, heat and moisture for the Global Environmental Multiscale (GEM) atmospheric model. In this study, the performance of the soil, vegetation and snow (SVS) scheme in estimating surface and root-zone soil moisture is evaluated against the ISBA (Interactions between Surface, Biosphere, and Atmosphere) scheme currently used operationally within GEM for numerical weather prediction. In addition, the sensitivity of SVS soil moisture results to soil texture and vegetation data sources (type and fractional coverage) has been explored. The performance of SVS and ISBA was assessed against a large set of in situ as well as brightness temperature data from the Soil Moisture and Ocean Salinity (SMOS) satellite over North America. The results indicate that SVS estimates the time evolution of soil moisture more accurately, and compared to ISBA results in higher correlations with observations and reduced errors. The sensitivity tests carried out during this study revealed that SVS soil moisture results are not affected significantly by the soil texture data from different sources. The vegetation data source, however, has a major impact on the soil moisture results predicted by SVS, and accurate specification of vegetation characteristics is crucial for accurate soil moisture prediction.

  12. Feedbacks between vegetation and soil moisture in mountain grasslands

    NASA Astrophysics Data System (ADS)

    Castelli, M.; Bertoldi, G.; Notarnicola, C.; Brenner, J.; Greifeneder, F.; Niedrist, G.; Tappeiner, U.

    2015-12-01

    Soil moisture content (SMC) is a key variable for water budget and controls both physical processes, as runoff generation, and biological processes, as vegetation development. On the other hand, vegetation and land management influence soil evolution and therefore SMC dynamic. Moreover, in mountain areas complex topography adds an additional control on water fluxes and climate. For those reasons, understanding the controls on the spatio-temporal variability of SMC is essential to predict how perturbations in vegetation and climate affects mountain hydrology. In this contribution we want to analyze the impact of different land management (meadows versus pastures) on the spatial and temporal dynamic of surface and root-zone SMC, and its relationships with climate and topography. We focus on water-limited alpine grasslands in the LTER area Mazia Valley in the European Alps. The infrastructure includes a dense network of more than 20 stations measuring soil moisture, biomass production observations and two eddy-covariance stations over meadow and pasture. Moreover, more than ten high-resolution SAR (Sentinel1 and RADARSAT2) images were acquired, in combination with ground surveys to monitor SMC spatial distribution. In order to understand the different physical controls, SMC has been also modelled using the GEOtop hydrological model, coupled with a dynamic vegetation model. Results show that meadows and pastures have different behaviors. Meadows are in general wetter and in flatter locations. This leads to higher vegetation productivity, development of soils with higher water holding capacity and to a positive feedback on SMC. In contrast, pastures are drier, in steeper locations with lower vegetation density and more compact soils due animal trampling, with a negative feedback on SMC. This co-evolution of land cover and SMC leads to persistent spatial patterns controlled by both topography and management.

  13. Soil Respiration Responses to Variation in Temperature Treatment and Vegetation Type

    NASA Astrophysics Data System (ADS)

    Liu, S.; Pavao-zuckerman, M.

    2013-12-01

    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.

  14. Mediterranean shrub vegetation: soil protection vs. water availability

    NASA Astrophysics Data System (ADS)

    García Estringana, Pablo; Nieves Alonso-Blázquez, M.; Alegre, Alegre; Cerdà, Artemi

    2014-05-01

    is very dynamic (Cerdà 1998b). Acknowledgements The research projects 07 M/0077/1998, 07 M/0023/2000 and RTA01-078-C2- 2, GL2008-02879/BTE, LEDDRA 243857 and RECARE FP7 project 603498 supported this research. References Belmonte Serrato, F., Romero Díaz, A., López Bermúdez, F., Hernández Laguna, E. 1999. Óptimo de cobertura vegetal en relación a las pérdidas de suelo por erosión hídrica y las pérdidas de lluvia por interceptación. Papeles de Geografía 30, 5-15. Cammeraat, E., Cerdà, A., Imeson, A.C. 2010. Ecohydrological adaptation of soils following land abandonment in a semiarid environment. Ecohydrology, 3: 421-430. 10.1002/eco.161 Cerdà, A. 1997a. The effect of patchy distribution of Stipa tenacissima L. on runoff and erosion. Journal of Arid Environments, 36, 37-51. Cerdà, A. 1998. The influence of aspect and vegetation on seasonal changes in erosion under rainfall simulation on a clay soil in Spain. Canadian Journal of Soil Science, 78, 321-330. Cerdà, A. 1998b. Changes in overland flow and infiltration after a rangeland fire in a Mediterranean scrubland. Hydrological Processes, 12, 1031-1042. Cerdà, A.1997b. Soil erosion after land abandonment in a semiarid environment of Southeastern Spain. Arid Soil Research and Rehabilitation, 11, 163-176. Garcia-Estringana, P., Alonso-Blázquez, N., Alegre, J. 2010b. Water storage capacity, stemflow and water funneling in Mediterranean shrubs. Journal of Hydrology 389, 363-372. Garcia-Estringana, P., Alonso-Blázquez, N., Marques, M.J., Bienes, R., Alegre, J. 2010a. Direct and indirect effects of Mediterranean vegetation on runoff and soil loss. European Journal of Soil Science 61, 174-185. García-Ruiz, J.M. 2010. The effects of land uses on soil erosion in Spain: a review. Catena 81, 1-11. Haregeweyn, N., Poesen, J., Verstraeten, G., Govers, G., de Vente, J., Nyssen, J., Deckers, J., and Moeyersons, J. 2013. Assessing the performance of a spatially distributed soil erosion and sediment delivery model

  15. Global model estimates of carbon and nitrogen storage in litter and soil pools: response to changes in vegetation quality and biomass allocation

    NASA Astrophysics Data System (ADS)

    Potter, Christopher S.; Klooster, Steven A.

    1997-02-01

    Changes in plant production, structure, and tissue composition are primary drivers for terrestrial biogeochemistry under future environmental conditions. Consequently, there is a need for process-oriented assessment of the potential global importance of vegetation controls over extended periods of C and N sequestration in terrestrial ecosystems. In this study, plant litter quality (lignin content) and carbon allocation to woody tissues are used as surrogates for testing the hypothetical effects of vegetation change on C and N cycles. We tested the CASA (Carnegie-Ames-Stanford approach) biosphere model, which uses global gridded (1°) satellite imagery on a monthly time interval to simulate seasonal patterns in net ecosystem carbon balance and near steady-state C/N storage in detritus and soils. Under contemporary "reference" settings, combined organic matter storage (litter plus surface soil to c. 30cm depth) for C and N is estimated highest in tropical and boreal forest ecosystem zones, and in cultivated ecosystems. The worldwide C:N ratio (by weight) for standing litter plus surface soil organic matter (SOM) is estimated at 23. About 14% of the projected global pool of 1327Pg (1015 g) soil C resides in "modern" form, in the sense that this proportion is in near-steady state exchange with plant production and decomposition on time scales of several decades. Likewise, about 12% of the projected global pool of 104Pg soil N is in modern form. Sensitivity tests treated litter quality and allocation effects independently from other direct effects of changes in climate, atmospheric CO2 levels, and primary production. For forested ecosystems, the model predicts that a hypothetical 50% decrease in litter lignin concentration would result in a long-term net loss of about 10% C from surface litter and soil organic matter pools. A 50% decrease in C allocation to woody tissues would invoke approximately the same net loss of C as a 50% decrease in litter lignin. With respect

  16. Modeling aeolian erosion in presence of vegetation

    NASA Astrophysics Data System (ADS)

    Dupont, S.; Bergametti, G.; Simoëns, S.

    2014-02-01

    Semiarid landscapes are characterized by vegetated surfaces. Understanding the impact of vegetation on aeolian soil erosion is important for reducing soil erosion or limiting crop damage through abrasion or burial. In the present study, a saltation model fully coupled with a large-eddy simulation airflow model is extended to vegetated landscapes. From this model, the sensitivity of sand erosion to different arrangements and type of plants (shrub versus tree) representative of semiarid landscapes is investigated and the wind erosion reduction induced by plants is quantified. We show that saltation processes over vegetated surfaces have a limited impact on the mean wind statistics, the momentum extracted from the flow by saltating particles being negligible compared to that extracted by plants. Simulated sand erosion patterns resulting from plant distribution, i.e., accumulation and erosion areas, appear qualitatively consistent with previous observations. It is shown that sand erosion reduction depends not only on vegetation cover but also on plant morphology and plant distribution relative to the mean wind direction. A simple shear stress partitioning approach applied in shrub cases gives similar trends of sand erosion reduction as the present model following wind direction and vegetation cover. However, the magnitude of the reduction appears significantly different from one approach to another. Although shrubs trap saltating particles, trees appear more efficient than shrubs to reduce sand erosion. This is explained by the large-scale sheltering effect of trees compared to the local shrub one.

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

    NASA Technical Reports Server (NTRS)

    Eagleson, P. S.

    1982-01-01

    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.

  18. Reflectance of vegetation, soil, and water

    NASA Technical Reports Server (NTRS)

    Wiegand, C. L. (Principal Investigator)

    1973-01-01

    The author has identified the following significant results. The ability to read the 24-channel MSS CCT tapes, select specified agricultural land use areas from the CCT, and perform multivariate statistical and pattern recognition analyses has been demonstrated. The 5 optimum channels chosen for classifying an agricultural scene were, in the order of their selection the far red visible, short reflective IR, visible blue, thermal infrared, and ultraviolet portions of the electromagnetic spectrum, respectively. Although chosen by a training set containing only vegetal categories, the optimum 4 channels discriminated pavement, water, bare soil, and building roofs, as well as the vegetal categories. Among the vegetal categories, sugar cane and cotton had distinctive signatures that distinguished them from grass and citrus. Acreages estimated spectrally by the computer for the test scene were acceptably close to acreages estimated from aerial photographs for cotton, sugar cane, and water. Many nonfarmable land resolution elements representing drainage ditch, field road, and highway right-of-way as well as farm headquarters area fell into the grass, bare soil plus weeds, and citrus categories and lessened the accuracy of the farmable acreage estimates in these categories. The expertise developed using the 24-channel data will be applied to the ERTS-1 data.

  19. A Methodology for Soil Moisture Retrieval from Land Surface Temperature, Vegetation Index, Topography and Soil Type

    NASA Astrophysics Data System (ADS)

    Pradhan, N. R.

    2015-12-01

    Soil moisture conditions have an impact upon hydrological processes, biological and biogeochemical processes, eco-hydrology, floods and droughts due to changing climate, near-surface atmospheric conditions and the partition of incoming solar and long-wave radiation between sensible and latent heat fluxes. Hence, soil moisture conditions virtually effect on all aspects of engineering / military engineering activities such as operational mobility, detection of landmines and unexploded ordinance, natural material penetration/excavation, peaking factor analysis in dam design etc. Like other natural systems, soil moisture pattern can vary from completely disorganized (disordered, random) to highly organized. To understand this varying soil moisture pattern, this research utilized topographic wetness index from digital elevation models (DEM) along with vegetation index from remotely sensed measurements in red and near-infrared bands, as well as land surface temperature (LST) in the thermal infrared bands. This research developed a methodology to relate a combined index from DEM, LST and vegetation index with the physical soil moisture properties of soil types and the degree of saturation. The advantage in using this relationship is twofold: first it retrieves soil moisture content at the scale of soil data resolution even though the derived indexes are in a coarse resolution, and secondly the derived soil moisture distribution represents both organized and disorganized patterns of actual soil moisture. The derived soil moisture is used in driving the hydrological model simulations of runoff, sediment and nutrients.

  20. Reflectance of vegetation, soil, and water

    NASA Technical Reports Server (NTRS)

    Wiegand, C. L.; Gausman, H. W.; Leamer, R. W.; Richardson, A. J.; Gerbermann, A. H. (Principal Investigator)

    1974-01-01

    The author has identified the following significant results. Iron deficient and normal grain sorghum plants were sufficiently different spectrally in ERTS-1 band 5 CCT data to detect chlorotic sorghum areas 2.8 acres (1.1 hectares) or larger in size in computer printouts of the MSS data. The ratio of band 5 to band 7 or band 7 minus band 5 relates to vegetation ground cover conditions and helps to select training samples representative of differing vegetation maturity or vigor classes and to estimate ground cover or green vegetation density in the absence of ground information. The four plant parameters; leaf area index, plant population, plant cover, and plant height explained 87 to 93% of the variability in band 6 digital counts and from 59 to 90% of the variation in bands 4 and 5. A ground area 2244 acres in size was classified on a pixel by pixel basis using simultaneously acquired aircraft support and ERTS-1 data. Overall recognition for vegetables, immature crops and mixed shrubs, and bare soil categories was 64.5% for aircraft and 59.6% for spacecraft data, respectively. Overall recognition results on a per field basis were 61.8% for aircraft and 62.8% for ERTS-1 data.

  1. Soil Moisture Estimation under Vegetation Applying Polarimetric Decomposition Techniques

    NASA Astrophysics Data System (ADS)

    Jagdhuber, T.; Schön, H.; Hajnsek, I.; Papathanassiou, K. P.

    2009-04-01

    Polarimetric decomposition techniques and inversion algorithms are developed and applied on the OPAQUE data set acquired in spring 2007 to investigate their potential and limitations for soil moisture estimation. A three component model-based decomposition is used together with an eigenvalue decomposition in a combined approach to invert for soil moisture over bare and vegetated soils at L-band. The applied approach indicates a feasible capability to invert soil moisture after decomposing volume and ground scattering components over agricultural land surfaces. But there are still deficiencies in modeling the volume disturbance. The results show a root mean square error below 8.5vol.-% for the winter crop fields (winter wheat, winter triticale and winter barley) and below 11.5Vol-% for the summer crop field (summer barley) whereas all fields have a distinct volume layer of 55-85cm height.

  2. Coevolution of hydraulic, soil and vegetation processes in estuarine wetlands

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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.

  3. The role of soil moisture on the coevolution of soil and vegetation in mountain grasslands

    NASA Astrophysics Data System (ADS)

    Bertoldi, Giacomo; Claudia, Notarnicola; Brenner, Johannes; Castelli, Mariapina; Greifeneder, Felix; Niedrist, Georg; Seeber, Julia; Tappeiner, Ulrike

    2016-04-01

    One of the key variables controlling the organization of vegetation and the coevolution of soils and landforms is soil moisture content (SMC). For this reason, understanding the controls on the spatial and temporal patterns of SMC is essential to predict how perturbations in vegetation and climate will affect mountain ecosystem functioning. In this contribution, we focus on the dynamic of surface SMC of water-limited alpine grasslands in the Long Term Ecological Research area Mazia Valley in the European Alps. We analyze the impacts of different land managements (meadows versus pastures) and its relationships with climate and topography. The area has been equipped since 2009 with a network of more than 20 stations, measuring SMC and climatic variables and with two eddy-covariance stations, measuring surface fluxes over meadows and pastures. Monthly biomass production data have been collected and detailed soil and spatial soil moisture surveys are available. Moreover, high spatial resolution SMC maps have been derived from satellites Synthetic Aperture Radar Radar (SAR) images (Sentinel 1 and RADARSAT2 images). Both ground surveys and remote sensing observations show persistent landscape-level patterns. Meadows, in general located in flatter areas, tend to be wetter. This leads to higher vegetation productivity and to the development of soils with higher water holding capacity, thus to a positive feedback on SMC. In contrast, pastures, located on steeper slopes with lower vegetation density and higher soil erosion, tend to be drier, leading to a negative feedback on SMC and soil development. This co-evolution of land cover and SMC leads therefore to persistent spatial patterns. In order to understand quantitatively such linked interactions, a sensitivity analysis has been performed with the GEOtop hydrological model. Results show how both abiotic (mainly slope and elevation) and anthropogenic (irrigation and soil management) factors exert a significant control on

  4. Estimation of arsenic in agricultural soils using hyperspectral vegetation indices of rice.

    PubMed

    Shi, Tiezhu; Liu, Huizeng; Chen, Yiyun; Wang, Junjie; Wu, Guofeng

    2016-05-01

    This study systematically analyzed the performance of multivariate hyperspectral vegetation indices of rice (Oryza sativa L.) in estimating the arsenic content in agricultural soils. Field canopy reflectance spectra was obtained in the jointing-booting growth stage of rice. Newly developed and published multivariate vegetation indices were initially calculated to estimate soil arsenic content. The well-performing vegetation indices were then selected using successive projections algorithm (SPA), and the SPA selected vegetation indices were adopted to calibrate a multiple linear regression model for estimating soil arsenic content. Results showed that a three-band vegetation index (R716-R568)/(R552-R568) performed best in the newly developed vegetation indices in estimating soil arsenic content. The photochemical reflectance index (PRI) and red edge position (REP) performed well in the published vegetation indices. Moreover, the linear combination of two vegetation indices ((R716-R568)/(R552-R568) and REP) selected using SPA improved the estimation of soil arsenic content. These results indicated that the newly developed three-band vegetation index (R716-R568)/(R552-R568) might be recommended as an indicator for estimating soil arsenic content in the study area. PRI and REP could be used as universal vegetation indices for monitoring soil arsenic contamination. PMID:26844405

  5. Estimation of arsenic in agricultural soils using hyperspectral vegetation indices of rice.

    PubMed

    Shi, Tiezhu; Liu, Huizeng; Chen, Yiyun; Wang, Junjie; Wu, Guofeng

    2016-05-01

    This study systematically analyzed the performance of multivariate hyperspectral vegetation indices of rice (Oryza sativa L.) in estimating the arsenic content in agricultural soils. Field canopy reflectance spectra was obtained in the jointing-booting growth stage of rice. Newly developed and published multivariate vegetation indices were initially calculated to estimate soil arsenic content. The well-performing vegetation indices were then selected using successive projections algorithm (SPA), and the SPA selected vegetation indices were adopted to calibrate a multiple linear regression model for estimating soil arsenic content. Results showed that a three-band vegetation index (R716-R568)/(R552-R568) performed best in the newly developed vegetation indices in estimating soil arsenic content. The photochemical reflectance index (PRI) and red edge position (REP) performed well in the published vegetation indices. Moreover, the linear combination of two vegetation indices ((R716-R568)/(R552-R568) and REP) selected using SPA improved the estimation of soil arsenic content. These results indicated that the newly developed three-band vegetation index (R716-R568)/(R552-R568) might be recommended as an indicator for estimating soil arsenic content in the study area. PRI and REP could be used as universal vegetation indices for monitoring soil arsenic contamination.

  6. [Impact of moss soil crust on vegetation indexes interpretation].

    PubMed

    Fang, Shi-bo; Zhang, Xin-shi

    2011-03-01

    Vegetation indexes were the most common and the most important parameters to characterizing large-scale terrestrial ecosystems. It is vital to get precise vegetation indexes for running land surface process models and computation of NPP change, moisture and heat fluxes over surface. Biological soil crusts (BSC) are widely distributed in arid and semi-arid, polar and sub-polar regions. The spectral characteristics of dry and wet BSCs were quite different, which could produce much higher vegetation indexes value for the wet BSC than for the dry BSC as reported. But no research was reported about whether the BSC would impact on regional vegetation indexes and how much dry and wet BSC had impact on regional vegetation indexes. In the present paper, the most common vegetation index NDVI were used to analyze how the moss soil crusts (MSC) dry and wet changes affect regional NDVI values. It was showed that 100% coverage of the wet MSC have a much higher NDVI value (0.657) than the dry MSC NDVI value (0.320), with increased 0.337. Dry and wet MSC NDVI value reached significant difference between the levels of 0.000. In the study area, MSC, which had the average coverage of 12.25%, would have a great contribution to the composition of vegetation index. Linear mixed model was employed to analyze how the NDVI would change in regional scale as wet MSC become dry MSC inversion. The impact of wet moss crust than the dry moss crust in the study area can make the regional NDVI increasing by 0.04 (14.3%). Due to the MSC existence and rainfall variation in arid and semi-arid zones, it was bound to result in NDVI change instability in a short time in the region. For the wet MSC's spectral reflectance curve is similar to those of the higher plants, misinterpretation of the vegetation dynamics could be more severe due to the "maximum value composite" (MVC) technique used to compose the global vegetation maps in the study of vegetation dynamics. The researches would be useful for

  7. Soil water availability as controlling factor for actual evapotranspiration in urban soil-vegetation-systems

    NASA Astrophysics Data System (ADS)

    Thomsen, Simon; Reisdorff, Christoph; Gröngröft, Alexander; Jensen, Kai; Eschenbach, Annette

    2015-04-01

    The City of Hamburg is characterized by a large number of greens, parks and roadside trees: 600.000 trees cover about 14% of the city area, and moreover, 245.000 roadside trees can be found here. Urban vegetation is generally known to positively contribute to the urban micro-climate via cooling by evapotranspiration (ET). The water for ET is predominantly stored in the urban soils. Hence, the actual evapotranspiration (ETa) is - beside atmospheric drivers - determined by soil water availability at the soil surface and in the rooting zones of the respective vegetation. The overall aim of this study is to characterize soil water availability as a regulative factor for ETa in urban soil-vegetation systems. The specific questions addressed are: i) What is the spatio-temporal variation in soil water availability at the study sites? ii) Which soil depths are predominantly used for water uptake by the vegetation forms investigated? and iii) Which are the threshold values of soil water tension and soil water content (Θ), respectively, that limit ETa under dry conditions on both grass-dominated and tree-dominated sites? Three study areas were established in the urban region of Hamburg, Germany. We selected areas featuring both single tree stands and grass-dominated sites, both representing typical vegetation forms in Hamburg. The areas are characterized by relatively dry soil conditions. However, they differ in regard to soil water availability. At each area we selected one site dominated by Common Oak (Quercus ruber L.) with ages from 40 to 120 years, and paired each oak tree site with a neighboring grass-dominated site. All field measurements were performed during the years 2013 and 2014. At each site, we continuously measured soil water tension and Θ up to 160 cm depth, and xylem sap flux of each of three oak trees per site in a 15 min-resolution. Furthermore, we measured soil hydraulic properties as pF-curve, saturated and unsaturated conductivity at all sites

  8. Estimating surface soil moisture from satellite microwave measurements and a satellite derived vegetation index

    NASA Technical Reports Server (NTRS)

    Owe, Manfred; Chang, Alfred; Golus, Robert E.

    1988-01-01

    Normalized 18-GHz microwave brightness temperatures, T(B), and a vegetation index determined from satellite radiometer data are combined with climatically modeled surface moisture estimates to constrain a simple physically based soil moisture model. It is found that the normalized T(B) values correlated well with soil moisture when the data were segregated by vegetation index range, but less so when all the data were combined. By using the vegetation index parameter, the model is shown to account for about 70 percent of the variability in modeled surface soil moisture.

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

    PubMed Central

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

    2009-01-01

    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

  10. Microwave backscatter dependence on surface roughness, soil moisture, and soil texture. II - Vegetation-covered soil

    NASA Technical Reports Server (NTRS)

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

    1979-01-01

    Results are presented for an experimental investigation to determine the relationship between radar backscatter coefficient (sigma) and soil moisture for vegetation-covered soil. These results extend a previous report which showed the experimental relationship between sigma and soil moisture for bare soil. It is shown that the highest correlation between sigma and soil moisture is 0.92 for the combined response of four crop types measured at 4.25 GHz, 10 deg incidence angle, and HH polarization. Radar look direction, relative to the crop row direction, is shown to have an insignificant effect on soil-moisture estimation if the radar frequency is higher than 4 GHz. The dependence on soil type can be minimized by expressing soil moisture in units of percent of field capacity. The possibility of using a single radar for measuring soil moisture for both bare and vegetated fields is demonstrated with a linear estimation algorithm having an experimental correlation coefficinet of 0.8.

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

    USGS Publications Warehouse

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

    2011-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    2), 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.

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

    NASA Technical Reports Server (NTRS)

    Lee, S. L.

    1974-01-01

    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.

  14. A land data assimilation system for simultaneous simulation of soil moisture and vegetation dynamics

    NASA Astrophysics Data System (ADS)

    Sawada, Yohei; Koike, Toshio; Walker, Jeffrey P.

    2015-06-01

    Despite the importance of the coupling between vegetation dynamics and root-zone soil moisture in land-atmosphere interactions, there is no land data assimilation system (LDAS) that currently addresses this issue, limiting the capacity to positively impact weather and seasonal forecasting. We develop a new LDAS that can improve the skill of an ecohydrological model to simulate simultaneously surface soil moisture, root-zone soil moisture, and vegetation dynamics by assimilating passive microwave observations that are sensitive to both surface soil moisture and terrestrial biomass. This LDAS first calibrates both hydrological and ecological parameters of a land surface model, which explicitly simulates vegetation growth and senescence. Then, it adjusts the model states of soil moisture and leaf area index (LAI) sequentially using a genetic particle filter. We can adjust the subsurface soil moisture, which is not observed directly by satellites, because we simulate the interactions between vegetation dynamics and subsurface water dynamics. From a point-scale evaluation, we succeed in improving the performance of our land surface model and generate ensembles of the model state whose distribution reflects the combined information in the land surface model and satellite observations. We show that the adjustment of the subsurface soil moisture significantly improves the capacity to simulate vegetation dynamics in seasonal forecast timescales. This LDAS can contribute to the generation of ensemble initial conditions of surface and subsurface soil moisture and LAI for a probabilistic framework of weather and seasonal forecasting.

  15. [Effects of solar greenhouse vegetable cultivation on soil physical quality].

    PubMed

    Sun, Yan; Wang, Yi-quan; Liu, Jun; Xia, Fa-sheng; Wang, Jin-gui; Li, Jian-bo

    2011-08-01

    Taking the solar greenhouse heavy loam soil having been planted vegetables for different years at Yunyang Town in Jingyang County of Shaanxi Province as test objects, and with the uncovered vegetable soil adjacent to the greenhouse as the control, this paper studied the effects of solar greenhouse vegetable cultivation on soil physical quality. Solar greenhouse vegetable cultivation had greater effects on the bulk density of 0-30 cm soil layer (an increase in 0-10 cm soil layer and a decrease in 10-30 cm soil layer), but little effects on that of 30-40 cm soil layer. In 0-40 cm solar greenhouse soil profile, the contents of < 0.01 mm physical clay and < 0.001 mm clay were lower in upper layer than in deeper layer, indicating their downward movement, and this phenomenon was more obvious with increasing year of solar greenhouse vegetable cultivation. Within the first 5 years of solar greenhouse vegetable cultivation, soil field water capacity decreased significantly, with a decrement of 13.8%, but remained relatively stable after then.

  16. Interactive Vegetation Phenology, Soil Moisture, and Monthly Temperature Forecasts

    NASA Technical Reports Server (NTRS)

    Koster, R. D.; Walker, G. K.

    2015-01-01

    The time scales that characterize the variations of vegetation phenology are generally much longer than those that characterize atmospheric processes. The explicit modeling of phenological processes in an atmospheric forecast system thus has the potential to provide skill to subseasonal or seasonal forecasts. We examine this possibility here using a forecast system fitted with a dynamic vegetation phenology model. We perform three experiments, each consisting of 128 independent warm-season monthly forecasts: 1) an experiment in which both soil moisture states and carbon states (e.g., those determining leaf area index) are initialized realistically, 2) an experiment in which the carbon states are prescribed to climatology throughout the forecasts, and 3) an experiment in which both the carbon and soil moisture states are prescribed to climatology throughout the forecasts. Evaluating the monthly forecasts of air temperature in each ensemble against observations, as well as quantifying the inherent predictability of temperature within each ensemble, shows that dynamic phenology can indeed contribute positively to subseasonal forecasts, though only to a small extent, with an impact dwarfed by that of soil moisture.

  17. Transregional Collaborative Research Centre 32: Patterns in Soil-Vegetation

    NASA Astrophysics Data System (ADS)

    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

    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

  18. Soil microbial properties under different vegetation types on Mountain Han.

    PubMed

    Wang, Miao; Qu, Laiye; Ma, Keming; Yuan, Xiu

    2013-06-01

    This study investigated the influence of broadleaf and conifer vegetation on soil microbial communities in a distinct vertical distribution belt in Northeast China. Soil samples were taken at 0-5, 5-10 and 10-20 cm depths from four vegetation types at different altitudes, which were characterized by poplar (Populus davidiana) (1250-1300 m), poplar (P. davidiana) mixed with birch (Betula platyphylla) (1370-1550 m), birch (B. platyphylla) (1550-1720 m), and larch (Larix principis-rupprechtii) (1840-1890 m). Microbial biomass and community structure were determined using the fumigation-extraction method and phospholipid fatty acid (PLFA) analysis, and soil fungal community level physiological profiles (CLPP) were characterized using Biolog FF Microplates. It was found that soil properties, especially soil organic carbon and water content, contributed significantly to the variations in soil microbes. With increasing soil depth, the soil microbial biomass, fungal biomass, and fungal catabolic ability diminished; however, the ratio of fungi to bacteria increased. The fungal ratio was higher under larch forests compared to that under poplar, birch, and their mixed forests, although the soil microbial biomass was lower. The direct contribution of vegetation types to the soil microbial community variation was 12%. If the indirect contribution through soil organic carbon was included, variations in the vegetation type had substantial influences on soil microbial composition and diversity.

  19. Mediterranean shrub vegetation: soil protection vs. water availability

    NASA Astrophysics Data System (ADS)

    García Estringana, Pablo; Nieves Alonso-Blázquez, M.; Alegre, Alegre; Cerdà, Artemi

    2014-05-01

    Soil Erosion and Land Degradation are closely related to the changes in the vegetation cover (Zhao et al., 2013). Although other factors such as rainfall intensiy or slope (Ziadat and Taimeh, 2013) the plant covers is the main factor that controls the soil erosion (Haregeweyn, 2013). Plant cover is the main factor of soil erosion processes as the vegetation control the infiltration and runoff generation (Cerdà, 1998a; Kargar Chigani et al., 2012). Vegetation cover acts in a complex way in influencing on the one hand on runoff and soil loss and on the other hand on the amount and the way that rainfall reaches the soil surface. In arid and semiarid regions, where erosion is one of the main degradation processes and water is a scant resource, a minimum percentage of vegetation coverage is necessary to protect the soil from erosion, but without compromising the availability of water (Belmonte Serrato and Romero Diaz, 1998). This is mainly controlled by the vegetation distribution (Cerdà, 1997a; Cammeraat et al., 2010; Kakembo et al., 2012). Land abandonment is common in Mediterranean region under extensive land use (Cerdà, 1997b; García-Ruiz, 2010). Abandoned lands typically have a rolling landscape with steep slopes, and are dominated by herbaceous communities that grow on pasture land interspersed by shrubs. Land abandonment use to trigger an increase in soil erosion, but the vegetation recovery reduces the impact of the vegetation. The goal of this work is to assess the effects of different Mediterranean shrub species (Dorycnium pentaphyllum Scop., Medicago strasseri, Colutea arborescens L., Retama sphaerocarpa, L., Pistacia Lentiscus L. and Quercus coccifera L.) on soil protection (runoff and soil losses) and on rainfall reaching soil surface (rainfall partitioning fluxes). To characterize the effects of shrub vegetation and to evaluate their effects on soil protection, two field experiments were carried out. The presence of shrub vegetation reduced runoff by

  20. The tri-soil experiment: do plants discriminate among vegetation soil types?

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We tested if rooting mass and root nutrient uptake of cheatgrass (Bromus tectorum) or creeping wildrye (Leymus triticoides) were influenced by vegetation soil type. Three soil types (A horizons), similar in gross physical and chemical properties, were freshly-collected. The soils varied in the veget...

  1. [Soil faunal diversity under typical alpine vegetations in West Sichuan].

    PubMed

    Huang, Xu; Wen, Wei-Quan; Zhang, Jian; Yang, Wan-Qin; Liu, Yang; Yan, Bang-Guo; Huang, Yu-Mei

    2010-01-01

    In order to understand the variations of soil faunal diversity under different natural alpine vegetations in West Sichuan, an investigation was made on the soil faunal communities under alpine coniferous forest, shrub, and meadow from August 2008 to June 2009. A total of 48343 individuals were collected, belonging to 7 phyla, 16 classes, 31 orders and 117 families. There was a great difference in the dominant groups of soil macro-fauna, and a significant difference (P < 0.05) in the number of soil faunal groups under different vegetations. Both the individual density and the group number of soil fauna decreased obviously with increasing soil depth, and were significantly higher (P < 0.01) in moss layer than in litter layer in coniferous forest. Significant difference (P < 0.01) was also observed in the density-group index among the three vegetations. The maximum biomass of soil macro-fauna was found in June. Jacard indices indicated that disturbed meadow had the lowest similarity of soil faunal community with the other vegetations. It was suggested that vegetation type had significant effects on the community structure of soil fauna, while aspect, altitude, and disturbance also had definite effects.

  2. Estimation of Soil Moisture for Vegetated Surfaces Using Multi-Temporal L-Band SAR Measurements

    NASA Technical Reports Server (NTRS)

    Shi, Jian-Cheng; Sun, G.; Hsu, A.; Wang, J.; ONeill, P.; Ranson, J.; Engman, E. T.

    1997-01-01

    This paper demonstrates the technique to estimate ground surface and vegetation scattering components, based on the backscattering model and the radar decomposition theory, under configuration of multi-temporal L-band polarimetric SAR measurement. This technique can be used to estimate soil moisture of vegetated surface.

  3. Radar reflectivity of bare and vegetation-covered soil

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

    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.

  4. Carbon Dynamics in Vegetation and Soils

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

    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.

  5. Vegetation clutter model

    NASA Technical Reports Server (NTRS)

    Ulaby, F. T.

    1980-01-01

    The statistical behavior of the radar backscattering coefficient of agricultural crops is examined. The data used were obtained by the microwave active spectrometer (MAS) systems in 1975 and 1976. Based on an evaluation of the angular and spectral variation of the mean, median, and 90-percent dynamic range of the coefficient (dB) histograms, empirical expressions describing the joint angular and frequency dependence of the mean and median were generated for each linear polarization configuration. The clutter model thus generated covers the angular range between 0 deg (nadir) and 80 deg and the frequency range between 1 GHz and 18 GHz. Decorrelation of the coefficient with frequency spacing was also evaluated and modeled.

  6. Detection of Cryptosporidium parvum in environmental soil and vegetables.

    PubMed

    Hong, Semie; Kim, Kyungjin; Yoon, Sejoung; Park, Woo-Yoon; Sim, Seobo; Yu, Jae-Ran

    2014-10-01

    Cryptosporidium parvum is a zoonotic protozoan parasite that causes cryptosporidial enteritis. Numerous outbreaks of cryptosporidiosis have been reported worldwide. Cryptosporidium is transmitted to hosts via consumption of contaminated water and food but also by direct contact with contaminated soil or infected hosts. The present study investigated farm soil collected from 34 locations along the western Korean peninsula and 24 vegetables purchased from local grocery markets in Seoul. The soil and vegetable samples were examined by real-time polymerase chain reaction (qPCR) to estimate the risk of infection. Eleven of 34 locations (32.4%) and 3 of 24 vegetable samples (12.5%) were contaminated with Cryptosporidium parvum, as confirmed by TaqI enzyme digestion of qPCR products and DNA sequencing. It is suggested that Cryptosporidium infection can be mediated via farm soil and vegetables. Therefore, it is necessary to reduce contamination of this organism in view of public health.

  7. Radiation budget and soil heat fluxes in different Arctic tundra vegetation types

    NASA Astrophysics Data System (ADS)

    Juszak, Inge; Iturrate Garcia, Maitane; Gastellu-Etchegorry, Jean-Philippe; Schaepman, Michael E.; Schaepman-Strub, Gabriela

    2016-04-01

    While solar radiation is one of the primary energy sources for warming and thawing permafrost soil, the amount of shortwave radiation reaching the soil is reduced by vegetation shading. Climate change has led to greening, shrub expansion and encroachment in many Arctic tundra regions and further changes are anticipated. These vegetation changes feed back to the atmosphere and permafrost as they modify the surface energy budget. However, canopy transmittance of solar radiation has rarely been measured or modelled for a variety of tundra vegetation types. We assessed the radiation budget of the most common vegetation types at the Kytalyk field site in North-East Siberia (70.8°N, 147.5°E) with field measurements and 3D radiative transfer modelling and linked it to soil heat fluxes. Our results show that Arctic tundra vegetation types differ in canopy albedo and transmittance as well as in soil heat flux and active layer thickness. Tussock sedges transmitted on average 56% of the incoming light and dwarf shrubs 27%. For wet sedges we found that the litter layer was very important as it reduced the average transmittance to only 6%. Model output indicated that both, albedo and transmittance, also depend on the spatial aggregation of vegetation types. We found that permafrost thaw was more strongly related to soil properties than to canopy shading. The presented radiative transfer model allows quantifying effects of the vegetation layer on the surface radiation budget in permafrost areas. The parametrised model can account for diverse vegetation types and variation of properties within types. Our results highlight small scale radiation budget and permafrost thaw variability which are indicated and partly caused by vegetation. As changes in species composition and biomass increase can influence thaw rates, small scale patterns should be considered in assessments of climate-vegetation-permafrost feedbacks.

  8. Effects of vegetation types on soil moisture estimation from the normalized land surface temperature versus vegetation index space

    NASA Astrophysics Data System (ADS)

    Zhang, Dianjun; Zhou, Guoqing

    2015-12-01

    Soil moisture (SM) is a key variable that has been widely used in many environmental studies. Land surface temperature versus vegetation index (LST-VI) space becomes a common way to estimate SM in optical remote sensing applications. Normalized LST-VI space is established by the normalized LST and VI to obtain the comparable SM in Zhang et al. (Validation of a practical normalized soil moisture model with in situ measurements in humid and semiarid regions [J]. International Journal of Remote Sensing, DOI: 10.1080/01431161.2015.1055610). The boundary conditions in the study were set to limit the point A (the driest bare soil) and B (the wettest bare soil) for surface energy closure. However, no limitation was installed for point D (the full vegetation cover). In this paper, many vegetation types are simulated by the land surface model - Noah LSM 3.2 to analyze the effects on soil moisture estimation, such as crop, grass and mixed forest. The locations of point D are changed with vegetation types. The normalized LST of point D for forest is much lower than crop and grass. The location of point D is basically unchanged for crop and grass.

  9. Measurement of soil hydraulic conductivity in relation with vegetation

    NASA Astrophysics Data System (ADS)

    Chen, Xi; Cheng, Qinbo

    2010-05-01

    Hydraulic conductivity is a key parameter which influences hydrological processes of infiltration, surface and subsurface runoff. Vegetation alters surface characteristics (e.g., surface roughness, litter absorption) or subsurface characteristics (e.g. hydraulic conductivity). Field infiltration experiment of a single ring permeameter is widely used for measuring soil hydraulic conductivity. Measurement equipment is a simple single-ring falling head permeameter which consists of a hollow cylinder that is simply inserted into the top soil. An optimization method on the basis of objective of minimum error between the measured and simulated water depths in the single-ring is developed for determination of the soil hydraulic parameters. Using the single ring permeameter, we measured saturated hydraulic conductivities (Ks) of the red loam soil with and without vegetation covers on five hillslopes at Taoyuan Agro-Ecology Experimental Station, Hunan Province of China. For the measurement plots without vegetation roots, Ks value of the soil at 25cm depth is much smaller than that of surface soil (1.52×10-4 vs. 1.10×10-5 m/s). For the measurement plots with vegetation cover, plant roots significantly increase Ks of the lower layer soil but this increase is not significant for the shallow soil. Moreover, influences of vegetation root on Ks depend on vegetation species and ages. Ks value of the Camellia is about three times larger than that of seeding of Camphor (2.62×10-4 vs. 9.82×10-5 m/s). Ks value of the matured Camellia is 2.72×10-4 m/s while Ks value of the young Camellia is only 2.17×10-4 m/s. Key words: single ring permeameter; soil hydraulic conductivity; vegetation

  10. Remote measurement of soil moisture over vegetation using infrared temperature measurements

    NASA Technical Reports Server (NTRS)

    Carlson, Toby N.

    1991-01-01

    Better methods for remote sensing of surface evapotranspiration, soil moisture, and fractional vegetation cover were developed. The objectives were to: (1) further develop a model of water movement through the soil/plant/atmosphere system; (2) use this model, in conjunction with measurements of infrared surface temperature and vegetation fraction; (3) determine the magnitude of radiometric temperature response to water stress in vegetation; (4) show at what point one can detect that sensitivity to water stress; and (5) determine the practical limits of the methods. A hydrological model that can be used to calculate soil water content versus depth given conventional meteorological records and observations of vegetation cover was developed. An outline of the results of these initiatives is presented.

  11. Modeling Feedbacks Between Water and Vegetation in the Climate System

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

    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.

  12. Electromagnetic wave scattering from vegetation (Potato) and vegetation covered soil moisture for remote sensing

    NASA Astrophysics Data System (ADS)

    Singh, Keshev

    In the country with limited resources, where the nutrition level of the population has to be maintained under inhospitable situation, the potato has a special value as food. Therefore efforts should be made for improvement and spreading the cultivation of this important crop. It demands an effective program that may provide information about potato growing areas and the growth conditions. Remote sensing has been acknowledged to be a valuable source of spatially comprehensive and temporally repeatable information of crop covered soil moisture, crop growth climatic information etc, which is useful and necessary for agriculture purposes. For this purpose, microwave remote sensing has evolved as an important tool. Since microwave are able to penetrate more deeply into vegetation and underneath ground surface. It is also preferred to the optical frequency band because microwave can work in all type of weather and have a wide signal dynamic range compared optical wavelengths. However interpretation of microwave scattering from agricultural crops requires an understanding the interaction among microwave, vegetative material and the soil. In order to develop useful forward and inverse models for retrieving the vegetation characteristic, it is necessary to know in detail the dielectric properties and plant structure of the vegetation over the range of expected growing conditions. In this paper, a theoretical model based on microwave interaction with potato crop along with examination of biomass of potato crop with the varying underlying soil moisture is studied. For this purpose, X-band (9.5GHz) scatterometer is used for studying the interaction of microwave with potato crop biomass and underlying soil moisture at various sensor parameters (i.e. angular variation and polarization, HH- and VV-). Although there may be a lot of crop parameters (i.e. crop height, leaf area index, etc) which also gives their effect on microwave. All this parameters are interlinked in the crop

  13. Influence of vegetation on the environmental partitioning of DDT in two global multimedia models.

    PubMed

    Wegmann, F; Scheringer, M; Möller, M; Hungerbühler, K

    2004-03-01

    Two multimedia models are used to investigate the effect of a vegetation compartment on the environmental partitioning of dichlorodiphenyltrichloroethane (DDT): a steady-state unit world model using global averages of vegetation cover and land-to-sea ratio and a dynamic model with latitudinal zones and zone-specific vegetation types and annual temperature courses. The vegetation compartment represents canopies of deciduous and coniferous forests and blades of grasses; the organic carbon content of the vegetation-covered soil is higher than in the bare soil. In the steady-state model, transfer from the air to the vegetation and the underlying soil as well as revolatilization from the foliage and reduced deposition to the soil is observed, depending on the chemical's degradation rate constant in vegetation and the deposition velocities of the gaseous and particle-bound fractions. In both models, a significant effect of the organic carbon content of the vegetation-covered soil increasing the effect of the vegetation compartment is observed. In the steady-state model, the changes in the DDT concentrations in air do not exceed 7% difference between the cases with and without vegetation; the soil concentrations differ by maximally a factor of 2.7. In the spatially and temporally resolved model, however, air concentration differences up to 90% are observed, depending on the type and amount of vegetation in the latitudinal zones. Long-range transport is less pronounced in the model with vegetation.

  14. Soil, water, and vegetation conditions in south Texas

    NASA Technical Reports Server (NTRS)

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

    1977-01-01

    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.

  15. Localised pattern formation in a model for dryland vegetation.

    PubMed

    Dawes, J H P; Williams, J L M

    2016-07-01

    We analyse the model for vegetation growth in a semi-arid landscape proposed by von Hardenberg et al. (Phys. Rev. Lett. 87:198101, 2001), which consists of two parabolic partial differential equations that describe the evolution in space and time of the water content of the soil and the level of vegetation. This model is a generalisation of one proposed by Klausmeier but it contains additional terms that capture additional physical effects. By considering the limit in which the diffusion of water in the soil is much faster than the spread of vegetation, we reduce the system to an asymptotically simpler parabolic-elliptic system of equations that describes small amplitude instabilities of the uniform vegetated state. We carry out a thorough weakly nonlinear analysis to investigate bifurcations and pattern formation in the reduced model. We find that the pattern forming instabilities are subcritical except in a small region of parameter space. In the original model at large amplitude there are localised solutions, organised by homoclinic snaking curves. The resulting bifurcation structure is well known from other models for pattern forming systems. Taken together our results describe how the von Hardenberg model displays a sequence of (often hysteretic) transitions from a non-vegetated state, to localised patches of vegetation that exist with uniform low-level vegetation, to periodic patterns, to higher-level uniform vegetation as the precipitation parameter increases.

  16. Improved Prediction of Quasi-Global Vegetation Conditions Using Remotely-Sensed Surface Soil Moisture

    NASA Technical Reports Server (NTRS)

    Bolten, John; Crow, Wade

    2012-01-01

    The added value of satellite-based surface soil moisture retrievals for agricultural drought monitoring is assessed by calculating the lagged rank correlation between remotely-sensed vegetation indices (VI) and soil moisture estimates obtained both before and after the assimilation of surface soil moisture retrievals derived from the Advanced Microwave Scanning Radiometer-EOS (AMSR-E) into a soil water balance model. Higher soil moisture/VI lag correlations imply an enhanced ability to predict future vegetation conditions using estimates of current soil moisture. Results demonstrate that the assimilation of AMSR-E surface soil moisture retrievals substantially improve the performance of a global drought monitoring system - particularly in sparsely-instrumented areas of the world where high-quality rainfall observations are unavailable.

  17. Shallow Subsurface Soil Moisture Dynamics in the Root-Zone and Bulk Soil of Sparsely Vegetated Land Surfaces as Impacted by Near-Surface Atmospheric State

    NASA Astrophysics Data System (ADS)

    Trautz, A.; Illangasekare, T. H.; Tilton, N.

    2015-12-01

    Soil moisture is a fundamental state variable that provides the water necessary for plant growth and evapotranspiration. Soil moisture has been extensively studied in the context of bare surface soils and root zones. Less attention has focused on the effects of sparse vegetation distributions, such as those typical of agricultural cropland and other natural surface environments, on soil moisture dynamics. The current study explores root zone, bulk soil, and near-surface atmosphere interactions in terms of soil moisture under different distributions of sparse vegetation using multi-scale laboratory experimentation and numerical simulation. This research is driven by the need to advance our fundamental understanding of soil moisture dynamics in the context of improving water conservation and next generation heat and mass transfer numerical models. Experimentation is performed in a two-dimensional 7.3 m long intermediate scale soil tank interfaced with a climate-controlled wind tunnel, both of which are outfitted with current sensor technologies for measuring atmospheric and soil variables. The soil tank is packed so that a sparsely vegetated soil is surrounded by bulk bare soil; the two regions are separated by porous membranes to isolate the root zone from the bulk soil. Results show that in the absence of vegetation, evaporation rates vary along the soil tank in response to longitudinal changes in humidity; soil dries fastest upstream where evaporation rates are highest. In the presence of vegetation, soil moisture in the bulk soil closest to a vegetated region decreases more rapidly than the bulk soil farther away. Evapotranspiration rates in this region are also higher than the bulk soil region. This study is the first step towards the development of more generalized models that account for non-uniformly distributed vegetation and land surfaces exhibiting micro-topology.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  19. Development of a ground hydrology model suitable for global climate modeling using soil morphology and vegetation cover, and an evaluation of remotely sensed information

    NASA Technical Reports Server (NTRS)

    Zobler, L.; Lewis, R.

    1988-01-01

    The long-term purpose was to contribute to scientific understanding of the role of the planet's land surfaces in modulating the flows of energy and matter which influence the climate, and to quantify and monitor human-induced changes to the land environment that may affect global climate. Highlights of the effort include the following: production of geo-coded, digitized World Soil Data file for use with the Goddard Institute for Space Studies (GISS) climate model; contribution to the development of a numerical physically-based model of ground hydrology; and assessment of the utility of remote sensing for providing data on hydrologically significant land surface variables.

  20. Predicting Vegetation Patterning across Climate, Soil, and Topographic Gradients

    NASA Astrophysics Data System (ADS)

    Axelsson, C.; Hanan, N. P.

    2014-12-01

    Vegetation communities in water-limited systems sometimes form periodic patterns, e.g. banded, spotted and labyrinthine distributions of woody and herbaceous plants. Pattern formation is commonly linked to competition and facilitation among plants, and variation in runoff and infiltration capacity in the landscape. Based on previous studies, we expect that climate, soil type, and slope to a large degree influence the type of vegetation pattern found at a specific site. We have analyzed to what extent vegetation patterns on the African continent can be predicted based on available climatic, topographic, and soil data. Our focus is not restricted to periodic patterns in drylands, but encompasses a range of tropical ecosystems from arid to humid. Vegetation patterns observed in remote sensing data can be informative regarding the underlying ecological processes that shape the landscape, not only in strikingly periodic vegetation but also in savannas with randomly located or dispersed vegetation. We use high-resolution multispectral and panchromatic remote sensing data classified into woody, herbaceous, and bare ground components. From these images we extract spatial statistical metrics that define type and degree of vegetation patterning. We then relate variables from climate, soil and topographic datasets to the observed patterns in order to determine how well we can predict vegetation patterning and which climatic and edaphic variables are most informative. We discuss the results and the possible sources of uncertainty in the relationships.

  1. Differentiating elements of the soil-vegetation complex

    NASA Technical Reports Server (NTRS)

    Baumgardner, M. F.

    1972-01-01

    The application of remote sensing to study soil-vegetation systems requires quantification and precise location of ground observation data such that they can be correlated with multispectral aerial acquired data. Griddling and sampling of an area for exact identification in a known address on magnetic tape containing multispectral scanner data produces quantitative physico-chemical parameters and the energy which is radiating from within the soil-vegetation complex of an area. Example classifications and spectral mappings of soils made from multispectral scanner data are included.

  2. Soil permeability as a function of vegetation type and soil water content.

    PubMed

    Morris, R C; Fraley, L

    1994-06-01

    Soil permeability is important for estimating the rate of mass transport of 222Rn through soils and into basements (Nazaroff 1992). We measured permeability and soil water content on a set of nine plots consisting of three plots vegetated with common barley (Hordeum vulgare), three plots vegetated with Russian thistle (Salsola kali), and three bare plots. Soil moisture was consistently highest on the bare plots and lowest on the Russian thistle plots. Plots with vegetation had lower soil water content during the growing season. Permeability was consistently higher on Russian thistle plots. ANOVA showed that both soil water content and presence of Russian thistle had a significant impact on permeability but that presence of barley did not. The effect of vegetation and moisture on permeability may have significant effects on 222Rn transport in soils.

  3. Soil permeability as a function of vegetation type and soil water content

    SciTech Connect

    Morris, R.C.; Fraley, L. Jr.

    1994-06-01

    Soil permeability is important for estimating the rate of mass transport of {sup 222}Rn through soils and into basements. We measured permeability and soil water content on a set of nine plots consisting of three plots vegetated with common barley (Hordeum vulgare), three plots vegetated with Russian thistle (Salsola kali), and three bare plots. Soil moisture was consistently highest on the bare plots and lowest on the Russian thistle plots. Plots with vegetation had lower soil water content during the growing season. Permeability was consistently higher on Russian thistle plots. ANOVA showed that both soil water content and presence of Russian thistle had a significant impact on permeability but that presence of barley did not. The effect of vegetation and moisture on permeability may have significant effects on {sup 222}Rn transport in soils. 18 refs., 8 figs., 1 tab.

  4. [Relationship among soil enzyme activities, vegetation state, and soil chemical properties of coal cinder yard].

    PubMed

    Wang, Youbao; Zhang, Li; Liu, Dengyi

    2003-01-01

    From field investigation and laboratory analysis, the relationships among soil enzyme activities, vegetation state and soil chemical properties of coal cinder yard in thermal power station were studied. The results showed that vegetation on coal cinder yard was distributed in scattered patch mainly with single species of plant, and herbs were the dominant species. At the same time, the activity of three soil enzymes had a stronger relativity to environment conditions, such as vegetation state and soil chemical properties. The sensitivity of three soil enzymes to environmental stress was in order of urease > sucrase > catalase. The relativity of three soil enzymes to environmental factor was in order of sucrase > urease > catalase. Because of urease being the most susceptible enzyme to environmental conditions, and it was marked or utmost marked interrelated with vegetation state and soil chemical properties, urease activity could be used as an indicator for the reclamation of wasteland.

  5. An overview of research on the beneficial effects of vegetation in contaminated soil.

    PubMed

    Erickson, L E

    1997-11-21

    Vegetation can enhance in situ bioremediation processes in many applications. Microbial transformations occur in soil and water external to plant roots. Organic contaminants also enter vegetation and are transformed within plants. Research progress is reviewed with emphasis on recent experimental results and mathematical models of contaminant fate in systems where vegetation is present. Plant evapotranspiration provides a solar driven pump-and-treat system which moves contaminants to the rhizosphere and helps to contain them on site. Significant savings have been reported at several field sites where vegetation has been utilized. PMID:9472312

  6. Coupling vegetation organization patterns to soil resource heterogeneity in a central Kenyan dryland using geophysical imagery

    NASA Astrophysics Data System (ADS)

    Franz, Trenton E.; King, Elizabeth G.; Caylor, Kelly K.; Robinson, David A.

    2011-07-01

    In dryland ecosystems, understanding the effects of heterogeneity in soil moisture and geophysical properties on vegetation structure and dynamics poses a suite of challenging research questions. Heterogeneity in soil depth can affect resource availability and the subsequent organization of woody vegetation, while spatiotemporal variation in soil moisture can reveal important ecohydrological feedbacks that govern the outcome of anthropogenic activities on the organization of dryland vegetation. In this research we investigate two cases of soil resource heterogeneity that affect the organization of dryland vegetation patterns by expanding previous electromagnetic induction (EMI) imaging techniques. In the first case we examine the influence of soil depth as a control on soil resource availability on hillslopes in tree-grass systems in central Kenya. Our results indicate that woody vegetation clumping occurs where soil depth changes, and the deeper rooted Acacia tortilis occurs on deep soils while the drought tolerant Acacia etbaica occurs on shallow soils. In the second case we examine daily patch-interpatch scale moisture dynamics following two different-sized rain events in a degraded landscape. With the aid of a numerical subsurface flow model, EMI, and soil moisture data, we have identified a possible positive feedback mechanism ("soil moisture halo effect") that we believe may have contributed to the proliferation and two-phase pattern formation of a native succulent Sansevieria volkensii in degraded ecosystems of Kenya. By determining how different plants respond to, and modify, the soil environment, we can better understand resource capture and dynamics, which in the longterm will help to develop management strategies.

  7. Research of the diurnal soil respiration dynamic in two typical vegetation communities in Tianjin estuarine wetland

    NASA Astrophysics Data System (ADS)

    Zhang, Q.; Meng, W. Q.; Li, H. Y.

    2016-08-01

    Understanding the differences and diurnal variations of soil respiration in different vegetation communities in coastal wetland is to provide basic reliable scientific evidence for the carbon "source" function of wetland ecosystems in Tianjin.Measured soil respiration rate which changed during a day between two typical vegetation communities (Phragmites australis, Suaeda salsa) in coastal wetland in October, 2015. Soil temperature and moisture were measured at the same time. Each of the diurnal curves of soil temperature in two communities had a single peak value, and the diurnal variations of soil moisture showed a "two peak-one valley" trend. The diurnal dynamic of soil respiration under the two communities had obvious volatility which showed a single peak form with its maximum between 12:00-14:00 and minimum during 18:00. The diurnal average of soil respiration rate in Phragmites australis communities was 3.37 times of that in Suaeda salsa communities. Significant relationships were found by regression analysis among soil temperature, soil moisture and soil respiration rate in Suaeda salsa communities. There could be well described by exponential models which was y = -0.245e0.105t between soil respiration rate and soil temperature, by quadratic models which was y = -0.276×2 + 15.277× - 209.566 between soil respiration rate and soil moisture. But the results of this study showed that there were no significant correlations between soil respiration and soil temperature and soil moisture in Phragmites australis communities (P > 0.05). Therefore, under the specific wetland environment conditions in Tianjin, soil temperature and moisture were not main factors influencing the diurnal variations of soil respiration rate in Phragmites australis communities.

  8. Geostatistical analyses reveal nutrient-vegetation relationships in savanna soils

    NASA Astrophysics Data System (ADS)

    Mladenov, N.; Okin, G. S.; Cassel, D.; Caylor, K. C.; Clausen, K. M.

    2005-12-01

    The uniform Kalahari sands that underlay the Kalahari Transect (KT) are a unique test bed for examining soil nutrient and vegetation cover relationships in a savanna ecosystem. Transects (300m x 100m) were sampled and mapped for each of four sites located along an aridity gradient from Mongu, Zambia in the north (1600 mm/yr precipitation), to Tshane, Botswana in the south (250 mm/yr precipitation). Geostatistical analyses of soil chemistry and tree, shrub, and grass cover at four sites along the moisture gradient of the KT indicated an accumulation of nutrients below tree/shrub cover. In general, areas where grasses dominated between canopies were negatively correlated with soil nutrients at the drier sites. Here we examine effects of vegetation cover on soil productivity and differences in soil nutrients along the moisture gradient of the KT.

  9. Vegetation affects the relative abundances of dominant soil bacterial taxa and soil respiration rates in an upland grassland soil.

    PubMed

    Thomson, Bruce C; Ostle, Nick; McNamara, Niall; Bailey, Mark J; Whiteley, Andrew S; Griffiths, Robert I

    2010-02-01

    Plant-derived organic matter inputs are thought to be a key driver of soil bacterial community composition and associated soil processes. We sought to investigate the role of acid grassland vegetation on soil bacterial community structure by assessing bacterial diversity in combination with other soil variables in temporally and spatially distinct samples taken from a field-based plant removal experiment. Removal of aboveground vegetation resulted in reproducible differences in soil properties, soil respiration and bacterial diversity. Vegetated soils had significantly increased carbon and nitrogen concentrations and exhibited higher rates of respiration. Molecular analyses revealed that the soils were broadly dominated by Alphaproteobacterial and Acidobacterial lineages, with increased abundances of Alphaproteobacteria in vegetated soils and more Acidobacteria in bare soils. This field-based study contributes to a growing body of evidence documenting the effect of soil nutrient status on the relative abundances of dominant soil bacterial taxa, with Proteobacterial taxa dominating over Acidobacteria in soils exhibiting higher rates of C turnover. Furthermore, we highlight the role of aboveground vegetation in mediating this effect by demonstrating that plant removal can alter the relative abundances of dominant soil taxa with concomitant changes in soil CO(2)-C efflux.

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

    PubMed

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

    2014-01-01

    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.

  11. [Soil infiltration characteristics under main vegetation types in Anji County of Zhejiang Province].

    PubMed

    Liu, Dao-Ping; Chen, San-Xiong; Zhang, Jin-Chi; Xie, Li; Jiang, Jiang

    2007-03-01

    The study on the soil infiltration under different main vegetation types in Anji County of Zhejiang Province showed that the characteristics of soil infiltration differed significantly with land use type, and the test eight vegetation types could be classified into four groups, based on soil infiltration capability. The first group, deciduous broadleaved forest, had the strongest soil infiltration capability, and the second group with a stronger soil infiltration capability was composed of grass, pine forest, shrub community and tea bush. Bamboo and evergreen broadleaved forest were classified into the third group with a relatively strong soil infiltration capability, while bare land belonged to the fourth group because of the bad soil structure and poorest soil infiltration capability. The comprehensive parameters of soil infiltration (alpha) and root (beta) were obtained by principal component analysis, and the regression model of alpha and beta could be described as alpha = 0. 1708ebeta -0. 3122. Soil infiltration capability was greatly affected by soil physical and chemical characteristics and root system. Fine roots (< or = 1 mm in diameter) played effective roles on the improvement of soil physical and chemical properties, and the increase of soil infiltration capability was closely related to the amount of the fine roots.

  12. Passive microwave response to vegetation and soil moisture on agricultural fields

    NASA Astrophysics Data System (ADS)

    Miller, B.; Bullock, Paul R.

    2014-10-01

    The SMAPVEX12 (Soil Moisture Active/Passive Validation Experiment) was carried out over the summer of 2012 in Manitoba, Canada. The goal of the project was to improve the accuracy of satellite based remote sensing of soil moisture. Data were gathered during a 42-day field campaign with surface measurements on 55 different agricultural fields in south-western Manitoba. The extended duration of the campaign, contrast in soil textures, and variety of crop types over the study region provided an excellent range of soil moisture and vegetation conditions. The study fields ranged from bare to fully vegetated, with volumetric soil moisture levels spanning almost 50%. Remotely sensed data were collected on 17 days by aircraft at 1.4 Ghz with a microwave radiometer at two different resolutions. Observed brightness temperatures from the radiometer showed a typical inverse relationship to the near simultaneous soil moisture measurements from the field. This study will focus on improving existing models for passive microwave retrieval of soil moisture using a more extensive data set of field-measured soil temperature, soil moisture and vegetation biomass from a wider range of crops than has been available in previous studies. The extensive ground data collected will allow for both a validation of the high-resolution passive soil moisture estimate, as well as an analysis on the effect of scaling to a lower resolution passive measurement.

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

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

    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.

  14. A heat balance model for partially vegetated surfaces

    NASA Astrophysics Data System (ADS)

    Zhang, J. Q.; Fang, X. P.; Zhang, H. X.; Yang, W.; Zhu, C. C.

    1997-08-01

    A steady-state thermal balance model has been designed to enable the prediction of the radiative temperature of partially vegetated surfaces. Vegetation is assumed to be a horizontally homogeneous but porous layer partially covering a soil surface. Short-wave and long-wave energy fluxes absorbed within the vegetation are estimated by solving simplified radiation equations. Sensible and latent heat exchange is estimated using a logarithmic and linear wind profile above the vegetation and a modified exponential profile within the vegetation. The stomatal resistance for latent heat flux is estimated from the equation summarizing the effect of solar irradiance, air temperature, and vapor pressure deficit on stomatal conductance. Based on the energy balance and the heat fluxes and water vapor continuity in the soil-vegetation-atmosphere system, the temperature of the foliage elements and the soil underneath is determined. The model has been tested by comparing simulated radiative temperatures with observed data gathered in short grass and a wheat field. The simulated and measured results match reasonably well. In order to examine whether the model responds to the change of a specific weather or material parameter, a sensitivity analysis of the model is considered.

  15. Retrieving Vegetation Parameters and Soil Reflection Coefficients with P-band SAR Polarimetry

    NASA Astrophysics Data System (ADS)

    Alemohammad, S. H.; Konings, A. G.; Jagdhuber, T.; Entekhabi, D.

    2015-12-01

    Photosynthetic activity of plants is highly dependent on the water available to the plant through its roots. Therefore, measuring the root-zone-soil-moisture across large spatial scales is of great importance for crop monitoring and yield estimation as well as hydrological and ecological modeling. Unlike L-band instruments, which are sensitive to only a few centimeters of the top soil layer, P-band Synthetic Aperture Radar (SAR) instruments have a penetration depth that can be used to retrieve soil moisture profiles in depths of several tens of centimeters (depending on soil texture and moisture content). NASA's Airborne Microwave Observatory of Subcanopy and Subsurface (AirMOSS) mission is designed to study the application of P-band SAR measurements for monitoring root-zone-soil-moisture. In this study, we introduce a new framework to retrieve vegetation parameters and smooth-surface soil reflection coefficients using SAR polarimetry and the fully polarimetric covariance matrix of the backscattering signal from AirMOSS observations. The retrieved soil reflectivities (both horizontally and vertically -polarized) can then be used to estimate the soil moisture profile. The retrieval model takes into account contributions from surface, dihedral and volume scattering coming from the vegetation and soil components, and does not require prior vegetation parameters. This approach reduces the dependency of the retrieval on allometry-based vegetation models with large numbers of uncertain parameters. The performance of this method will be validated using observations from AirMOSS field campaigns in July 2013 over Harvard Forest in Massachusetts, USA. This will enable a quality assessment of the polarimetry-based retrieval of the soil reflectivities and the estimated root-zone-soil-moisture profiles.

  16. Modelling the Congo basin ecosystems with a dynamic vegetation model

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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

  17. Soil erosion-vegetation interactions in Mediterranean-dry reclaimed mining slopes

    NASA Astrophysics Data System (ADS)

    Moreno de las Heras, Mariano; Merino-Martín, Luis; Espigares, Tíscar; Nicolau, José M.

    2014-05-01

    Mining reclamation in Mediterranean-dry environments represents a complex task. Reclaimed mining slopes are particularly vulnerable to the effects of accelerated soil erosion processes, especially when these processes lead to the formation of rill networks. On the other hand, encouraging early vegetation establishment is perceived as indispensable to reduce the risk of degradation in these man-made ecosystems. This study shows a synthesis of soil erosion-vegetation research conducted in reclaimed mining slopes at El Moral field site (Teruel coalfield, central-east Spain). Our results highlight the role of rill erosion processes in the development of reclaimed ecosystems. Runoff routing is conditioned by the development of rill networks, maximizing the loss of water resources at the slope scale by surface runoff and altering the spatial distribution of soil moisture. As a result, the availability of water resources for plant growth is drastically reduced, affecting vegetation development. Conversely, vegetation exerts a strong effect on soil erosion: erosion rates rapidly decrease with vegetation cover and no significant rill erosion is usually observed after a particular cover threshold is reached. These interactive two-way vegetation-soil erosion relationships are further studied using a novel modeling approach that focuses on stability analysis of water-limited reclaimed slopes. Our framework reproduces two main groups of trends along the temporal evolution of reclaimed slopes: successful trends, characterized by widespread vegetation development and the effective control of rill erosion processes; and gullying trends, characterized by the progressive loss of vegetation and a sharp logistic increase in erosion rates. This stability-analysis also facilitates the determination of threshold values for both vegetation cover and rill erosion that drive the long-term reclamation results, assisting the identification of critical situations that require specific human

  18. Assessment of regional biomass-soil relationships using vegetation indexes

    NASA Technical Reports Server (NTRS)

    Lozano-Garcia, D. Fabian; Fernandez, R. Norberto; Johannsen, Chris J.

    1991-01-01

    The development of photosynthetic active biomass in different ecological conditions, as indicated by normalized difference vegetation indices (NDVIs) is compared by performing a stratified sampling (based on soil assocations) on data acquired over Indiana. Data from the NOAA-10 AVHRR were collected for the 1987 and 1988 growing seasons. An NDVI transformation was performed using the two optical bands of the sensor (0.58-0.68 microns and 0.72-1.10 microns). The NDVI is related to the amount of active photosynthetic biomass present on the ground. Samples of NDVI values over 45 fields representing eight soil associations throughout Indiana were collected to assess the effect of soil conditions and acquisition date on the spectral response of the vegetation, as shown by the NDVIs. Statistical analysis of results indicate that land-cover types (forest, forest/pasture, and crops), soil texture, and soil water-holding capacity have an important effect on vegetation biomass changes as measured by AVHRR data. Acquisition dates should be selected with condideration of the phenological stages of vegetation. Sampling of AVHRR data over extended areas should be stratified according to physiographic units rather than man-made boundaries. This will provide more homogeneous samples for statistical analysis.

  19. Introducing tropical lianas in a vegetation model

    NASA Astrophysics Data System (ADS)

    Verbeeck, Hans; De Deurwaerder, Hannes; Brugnera, Manfredo di Procia e.; Krshna Moorthy Paravathi, Sruthi; Pausenberger, Nancy; Roels, Jana; kearsley, elizabeth

    2016-04-01

    Tropical forests are essential components of the earth system and play a critical role for land surface feedbacks to climate change. These forests are currently experiencing large-scale structural changes, including the increase of liana abundance and biomass. This liana proliferation might have large impacts on the carbon cycle of tropical forests. However no single global vegetation model currently accounts for lianas. The TREECLIMBERS project (ERC starting grant) aims to introduce for the first time lianas into a vegetation model. The project attempts to reach this challenging goal by performing a global meta-analysis on liana data and by collecting new data in South American forests. Those new and existing datasets form the basis of a new liana plant functional type (PFT) that will be included in the Ecosystem Demography model (ED2). This presentation will show an overview of the current progress of the TREECLIMBERS project. Liana inventory data collected in French Guiana along a forest disturbance gradient show the relation between liana abundance and disturbance. Xylem water isotope analysis indicates that trees and lianas can rely on different soil water resources. New modelling concepts for liana PFTs will be presented and in-situ leaf gas exchange and sap flow data are used to parameterize water and carbon fluxes for this new PFT. Finally ongoing terrestrial LiDAR observations of liana infested forest will be highlighted.

  20. Effect of Soil and Vegetation Heterogeneity on Runoff in a Semi-arid Grassland

    NASA Astrophysics Data System (ADS)

    Bedford, D. R.; Small, E. E.; Tucker, G. E.; Pockman, W. T.

    2006-12-01

    Vegetation in drylands is typically patchy, and surface soil properties tend to covary with this pattern. For example, infiltration rates tend to be relatively high under plant canopies, and decrease as a function of distance away from canopies. Vegetation also tends to exist on raised mounds of microtopography, and adjacent interspaces are topographically lower as a function of distance from vegetation patches. These patterns will clearly affect the locations where overland flow is generated and how it is routed on the landscape. Predicting soil erosion from overland flow therefore requires the ability to quantify how vegetation and soil properties covary over small-scales (i.e. decimeter to tens of meters). We use a two-dimensional numerical model that simulates overland flow using spatially variable vegetation, microtopography, and infiltration (saturated conductivity). We use a diffusion wave approximation for the shallow overland flow equations and green-ampt infiltration dynamics to simulate overland flow and infiltration at 5-cm grid cells. We calibrate unknown parameters such as roughness, and test the model with known spatial fields of surface properties and observed rainfall and runoff from eight ~100 m2 plots at the Sevilleta LTER in Central New Mexico. We interpolate measured surface properties with cokriging determined by geostatistical relationships to the vegetation pattern. We measure rainfall with tipping buckets and runoff at 5-second resolution from runoff gutters and flumes below the gently sloped grassland plots. Experiments indicate that bulk runoff volume is approximated as a function of surface depression volume and the mean and variance of microtopography and infiltration. We then simulate overland flow and erosion on plots that have experienced three years of vegetation reduction due to enforced drought in a controlled experiment. We quantify change in vegetation cover and pattern, and show how runoff discharge and patterns of overland

  1. Analyzing Groundwater-Vegetation Interactions using a Dynamic Agroecosystem Model

    NASA Astrophysics Data System (ADS)

    Soylu, M. E.; Kucharik, C. J.; Loheide, S. P.

    2012-12-01

    Groundwater is a crucial source of water for vegetation, especially in arid and semiarid environments in many regions around the world and its availability controls the distribution and the physiology of plant species. However, the impact of groundwater on vegetation is not completely understood mainly due to the limited ability of current models to simulate groundwater and vegetation interactions. Existing land surface models (LSM) simulate water and energy fluxes among soil-vegetation-atmosphere systems in a process-based way, but lack a detailed simulation of soil water movement in the unsaturated zone, particularly when groundwater is present. Furthermore, there are only a few available LSM and/or process based vegetation models that can simulate agroecosystems, which are as important to understand as natural ecosystems considering they occupy approximately 40% of the global land surface. On the other hand, current physically-based, variably-saturated soil water flux models are able to accurately simulate water movement in the unsaturated zone. However, they often lack a detailed plant physiology component making it difficult to understand plant responses to both variations in energy fluxes and upward capillary fluxes in shallow groundwater environments. To connect these two different model types, the objectives of this study are (1) to incorporate an advanced dynamic agroecosystem model (Agro-IBIS) and a variably saturated soil water flow model (Hydrus-1D) into a single framework that is capable of simulating groundwater and plant/crop system interactions in a fully, physically-based fashion, and (2) to apply this model using observed climate records to better understand the responses of managed and natural ecosystems to varied water table depths under inter-annual climate forcing conditions. The model results show that as the water table becomes shallower, (1) soil temperature decreases due to the moisture content driven effects on the thermal diffusivity of

  2. Estimation of effective hydrologic properties of soils from observations of vegetation density

    NASA Technical Reports Server (NTRS)

    Tellers, T. E.; Eagleson, P. S.

    1980-01-01

    A one-dimensional model of the annual water balance is reviewed. Improvements are made in the method of calculating the bare soil component of evaporation, and in the way surface retention is handled. A natural selection hypothesis, which specifies the equilibrium vegetation density for a given, water limited, climate soil system, is verified through comparisons with observed data. Comparison of CDF's of annual basin yield derived using these soil properties with observed CDF's provides verification of the soil-selection procedure. This method of parameterization of the land surface is useful with global circulation models, enabling them to account for both the nonlinearity in the relationship between soil moisture flux and soil moisture concentration, and the variability of soil properties from place to place over the Earth's surface.

  3. Canopy reflectance modelling of semiarid vegetation

    NASA Technical Reports Server (NTRS)

    Franklin, Janet

    1994-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    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

  5. Uptake of 137Cs by Leafy Vegetables and Grains from Calcareous Soils

    SciTech Connect

    Robison, W; Hamilton, T; Conrado, C; Kehl, S

    2004-04-19

    Cesium-137 was deposited on Bikini Island at Bikini Atoll in 1954 as a result of nuclear testing and has been transported and cycled in the ecosystem ever since. Atoll soils are of marine origin and are almost pure CaCO{sub 3} with high concentrations of organic matter in the top 40 cm. Data from previous experiments with mature fruit trees show very high transfer factors (TF's), [Bq g{sup -1} plant/ Bq g{sup -1} soil, both in dry weight] into fruits from atoll calcareous soil. These TF's are much higher than reported for continental, silica-based soils. In this report TF's for 5 types of leafy vegetable crops and 2 types of grain crops are provided for use in predictive dose assessments and for comparison with other data from other investigators working with other types of soil in the IAEA CRP ''The Classification of Soil Systems on the Basis of Transfer Factors of Radionuclides from Soil to Reference Plants''. Transfer factors for plants grown on calcareous soil are again very high relative to clay-containing soils and range from 23 to 39 for grain crops and 21 to 113 for leafy vegetables. Results from these experiments, in this unique, high pH, high organic content, low potassium (K) soil, provide a boundary condition for models relating soil properties to TF.

  6. Aminopyralid soil residues affect rotational vegetable crops in Florida

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Field experiments were conducted to determine the sensitivity of bell pepper, eggplant, tomato, muskmelon, and watermelon to aminopyralid soil residues. Aminopyralid was applied at six rates ranging from 0.0014 kg ae ha 1 to 0.0448 kg ae ha 1, and vegetable crops were planted in the treated areas. ...

  7. [Review of dynamic global vegetation models (DGVMs)].

    PubMed

    Che, Ming-Liang; Chen, Bao-Zhang; Wang, Ying; Guo, Xiang-Yun

    2014-01-01

    Dynamic global vegetation model (DGVM) is an important and efficient tool for study on the terrestrial carbon circle processes and vegetation dynamics. This paper reviewed the development history of DGVMs, introduced the basic structure of DGVMs, and the outlines of several world-widely used DGVMs, including CLM-DGVM, LPJ, IBIS and SEIB. The shortages of the description of dynamic vegetation mechanisms in the current DGVMs were proposed, including plant functional types (PFT) scheme, vegetation competition, disturbance, and phenology. Then the future research directions of DGVMs were pointed out, i. e. improving the PFT scheme, refining the vegetation dynamic mechanism, and implementing a model inter-comparison project. PMID:24765870

  8. [Investigation of polarization characteristics of soil surface with low vegetation cover and different soil moisture].

    PubMed

    Zhang, Qiao; Sun, Xiao-bing; Hong, Jin

    2010-11-01

    Compared with the spectral detection method, polarization detection could obtain more information of the target. For example, the polarization detection could be applied to interpret the refractive index and the surface roughness of the object, or retrieve the soil moisture, etc. Polarization detection provides a new approach to quantitative retrieval of soil moisture, and this is very important in agriculture, hydrology, meteorology and ecology. The polarization characteristics of soil surface with low vegetation cover,which is a example of mixed pixel in remote sensing, were researched with experiments, and the relationship between the polarization characteristics and soil moisture was also explored. The results showed that the polarization characteristics of soil surface with low vegetation cover are mainly determined by the area of bare soil, and are strongly relevant with the soil moisture. For the results of experiments in this paper, the IDOLP of soil surface with low vegetation cover increased with increasing soil moisture when the viewing angle of instrument was between 20 degree and 60 degree, while the incident angle of light source was fixed at 40 degree. This paper offered a new method to retrieve moisture content of soil with low vegetation cover.

  9. Assessing global vegetation activity using spatio-temporal Bayesian modelling

    NASA Astrophysics Data System (ADS)

    Mulder, Vera L.; van Eck, Christel M.; Friedlingstein, Pierre; Regnier, Pierre A. G.

    2016-04-01

    This work demonstrates the potential of modelling vegetation activity using a hierarchical Bayesian spatio-temporal model. This approach allows modelling changes in vegetation and climate simultaneous in space and time. Changes of vegetation activity such as phenology are modelled as a dynamic process depending on climate variability in both space and time. Additionally, differences in observed vegetation status can be contributed to other abiotic ecosystem properties, e.g. soil and terrain properties. Although these properties do not change in time, they do change in space and may provide valuable information in addition to the climate dynamics. The spatio-temporal Bayesian models were calibrated at a regional scale because the local trends in space and time can be better captured by the model. The regional subsets were defined according to the SREX segmentation, as defined by the IPCC. Each region is considered being relatively homogeneous in terms of large-scale climate and biomes, still capturing small-scale (grid-cell level) variability. Modelling within these regions is hence expected to be less uncertain due to the absence of these large-scale patterns, compared to a global approach. This overall modelling approach allows the comparison of model behavior for the different regions and may provide insights on the main dynamic processes driving the interaction between vegetation and climate within different regions. The data employed in this study encompasses the global datasets for soil properties (SoilGrids), terrain properties (Global Relief Model based on SRTM DEM and ETOPO), monthly time series of satellite-derived vegetation indices (GIMMS NDVI3g) and climate variables (Princeton Meteorological Forcing Dataset). The findings proved the potential of a spatio-temporal Bayesian modelling approach for assessing vegetation dynamics, at a regional scale. The observed interrelationships of the employed data and the different spatial and temporal trends support

  10. Evolution of hydrological pathways in engineered hillslopes due to soil and vegetation development

    NASA Astrophysics Data System (ADS)

    Appels, Willemijn M.; Ireson, Andrew M.; McDonnell, Jeffrey J.; Barbour, S. Lee

    2015-04-01

    The structure and hydraulic properties of soils and bedrock within a hillslope combined with the timing and rates of water availability control the partitioning of precipitation into vertical and lateral flowpaths. In natural hillslope sites, heterogeneity in both soil texture and structure are the result of long-term landscape evolution processes and consequently can be assumed to be static relative to the timescale of rainfall-runoff processes. However; engineered hillslopes, constructed commonly as reclamation covers overlying mine waste, have been observed to undergo rapid changes in hydraulic properties over relatively short timescales (i.e. 3-5 years) as a result of weathering (e.g. freeze-thaw and wet-dry cycles) and vegetation growth (e.g. increasing rooting depth and density). Rainfall-runoff responses on such hillslopes would therefore not only be expected to reflect seasonal dynamics, but also the evolution of the system from a relatively homogeneous initial condition to a system with increasing heterogeneity of soil texture and structure. We present results of a combined field and modeling study of three prototype soil covers on a saline-sodic shale overburden dump at the Syncrude Canada Ltd. Mildred Lake mine, north of Fort McMurray, Canada. Since their construction in 1999, soil properties, hydrological response to atmospheric and vegetative demands, and vegetation properties have been extensively monitored. The three covers have undergone substantial evolution due to freeze-thaw processes and aggrading vegetation. In this work, we quantify hydrological processes in the reclamation covers, focusing on inter- and intra-annual patterns. To this purpose we analyzed the long-term hydrometric data with field sampling of the distribution of salts and the stable isotopes of water within soil water and subsurface flow in the base of the cover. We use a 2D Hydrus model to explore the co-evolution of soil and vegetation and quantify its effect on flow

  11. Reflectance of vegetation, soil, and water

    NASA Technical Reports Server (NTRS)

    Wiegand, C. L. (Principal Investigator); Gausman, H. W.; Leamer, R. W.; Richardson, A. J.; Gerbermann, A. H.; Torline, R. J.; Gautreaux, M. R.; Everitt, J. H.; Guellar, J. A.; Rodriguez, R. R.

    1974-01-01

    The author has identified the following significant results. Bands 4, 5, and 7 and 5, 6, and 7 were best for distinguishing among crop and soil categories in ERTS-1 SCENES 1182-16322 (1-21-73) and 1308-16323 (5-21-73) respectively. Chlorotic sorghum areas 2.8 acres or larger in size were identified on a computer printout of band 5 data. Reflectance of crop residues was more often different from bare soil in band 4 than in bands 5, 6, and 7. Simultaneously acquired aircraft and spacecraft MSS data indicated that spacecraft surveys are as reliable as aircraft surveys. ERTS-1 data were successfully used to estimate acreage of citrus, cotton, and sorghum as well as idle crop land.

  12. Development of a New Land Data Assimilation System for Improvement of Forecasting both Soil Moisture and Vegetation Dynamics

    NASA Astrophysics Data System (ADS)

    Sawada, Y.; Koike, T.

    2014-12-01

    To improve the skill of reproducing land-atmosphere interactions in weather, seasonal, and climate prediction systems, it is necessary to simulate correctly and simultaneously the soil moisture and terrestrial biomass in land surface models. Despite the importance of the interactions between subsurface soil moisture and vegetation dynamics on the climate system both in global and regional scales, a land data assimilation approach that can effectively address these water and vegetation growth interactions has yet to be established. We develop a new land data assimilation system that can improve to simultaneously simulate surface and subsurface soil moisture and vegetation growth by assimilating a microwave observation that is sensitive to both surface soil moisture and terrestrial biomass. Our new system, Coupled Land and Vegetation Data Assimilation System (CLVDAS) comprises an eco-hydrological model that has a physically-based and sophisticated soil hydrology scheme and dynamic vegetation model that can estimate vegetation growth and senescence, and radiative transfer model that can convert land surface conditions into brightness temperatures in the microwave region. The CLVDAS firstly optimizes hydrological and ecological unknown parameters in the model at the same time by using the shuffled complex evolution method. Secondly, the model states of surface soil moisture, root-zone soil moisture, and leaf area index are adjusted by using genetic particle filter. We can justify to adjust the root-zone soil moisture from a microwave observation of the earth surface since we explicitly model subsurface water - vegetation dynamics interactions. From the point-scale evaluation at the in-situ observation sites in Mali, Mongolia, the United States, and Australia, we confirm the CLVDAS significantly improve the skill of simulating vertical soil moisture distribution and vegetation dynamics by assimilating microwave brightness temperatures from Advanced Microwave Scanning

  13. Infiltration and Transport of Bromide and Cryptosporidium parvum in Vegetated, Tilted Soil Box Experiments

    NASA Astrophysics Data System (ADS)

    Harter, T.; Atwill, E. R.; Hou, L.; Carle, B. M.

    2005-12-01

    In this paper we develop a conceptual model of the physics of flow and transport in packed, tilted, and vegetated soil boxes during and immediately after simulated rainfall events and apply it to 54 experiments implemented for three different soils at three different slopes and two different rainfall rates. Using an inverse modeling procedure, we show that a significant amount of the subsurface outflow from the soil boxes is due to macropore flow. The effective hydraulic properties of the macropore space were obtained by calibration of a simple two-domain flow and transport model that accounts for coupled flow in the matrix and in the macropores of the soils. While the macropore hydraulic properties are highly variable, linear mixed effects ( LME) modeling showed significant association with soil bulk density and with the rainfall rate. Macropore flow is shown to be responsible for both, tracer (bromide) and C. parvum transport through the soil into the underlying pore space observed during the 4 hours experiments. Over a 20 cm thick soil horizon, the soil attenuation rate for C. parvum due to straining in the soil matrix and due to filtration to the macropore surfaces is 0.6 (half an order of magnitude). The LME and logistic regression models developed from the soil box experiments provide a basis for estimating macropore hydraulic properties and the risk of C. parvum transport through shallow soils from bulk density, precipitation, and total subsurface flow rate information.

  14. Vegetation and Roughness Controls on Field Scale Soil Moisture Variability

    NASA Astrophysics Data System (ADS)

    Adams, J. R.; Berg, A. A.; Toth, B.; Magagi, R.

    2009-05-01

    Downscaling of satellite-based passive microwave soil moisture products such as those to be derived from the Soil Moisture and Ocean Salinity (SMOS) mission requires enhanced understanding of controls of field scale soil moisture variability. A RADARSAT 2 field validation campaign was conducted in July 2008 to measure soil conditions, crop parameters and surface roughness over a six day period, at a network of 10 agricultural sites in Saskatchewan (N 50° - N 51°; W 105° - W 106°). Four crop types are analysed: pulse crops, cereals, oilseeds, and fallow fields, with a sample area of 2.1 km2 per site. From this data set we evaluate the impact of vegetation type and surface roughness on field scale soil moisture variability using parametric and non-parametric statistical approaches. Our results demonstrate the importance of both field scale roughness and vegetation type on field scale variability. Of significance, field scale roughness can be measured from satellite platforms such as RADARSAT-2 and vegetation type is available from optical sensors.

  15. Organic fertilization for soil improvement in a vegetable cropping system

    NASA Astrophysics Data System (ADS)

    Verhaeghe, Micheline; De Rocker, Erwin; De Reycke, Luc

    2016-04-01

    Vegetable Research Centre East-Flanders Karreweg 6, 9770 Kruishoutem, Belgium A long term trial for soil improvement by organic fertilization was carried out in Kruishoutem from 2001 till 2010 in a vegetable rotation (carrots - leek - lettuce (2/year) - cauliflower (2/year) - leek - carrots - lettuce (2/year) - cauliflower (2/year) - leek and spinach). The trial compared yearly applications of 30 m²/ha of three types of compost (green compost, vfg-compost and spent mushroom compost) with an untreated object which did not receive any organic fertilization during the trial timescale. The organic fertilization was applied shortly before the cropping season. Looking at the soil quality, effects of organic fertilization manifest rather slow. The first four years after the beginning of the trial, no increase in carbon content of the soil is detectable yet. Although, mineralization of the soil has increased. The effect on the mineralization is mainly visible in crops with a lower N uptake (e.g. carrots) leading to a higher nitrate residue after harvest. Effects on soil structure and compaction occur rather slowly although, during the first two cropping seasons compost applications increase the water retention capacity of the soil. Compost increases the pH of the soil from the first year on till the end of the trial in 2010. Thus, organic fertilization impedes acidification in light sandy soils. Also soil fertility benefits from compost by an increase in K-, Ca- and Mg- content in the soil from the second year on. After 10 years of organic fertilization, yield and quality of spinach were increased significantly (p<0.05) compared to the untreated object. Also leek (2002 and 2009) and lettuce (2003 and 2007) benefit from organic fertilization.

  16. CAOS: the nested catchment soil-vegetation-atmosphere observation platform

    NASA Astrophysics Data System (ADS)

    Weiler, Markus; Blume, Theresa

    2016-04-01

    Most catchment based observations linking hydrometeorology, ecohydrology, soil hydrology and hydrogeology are typically not integrated with each other and lack a consistent and appropriate spatial-temporal resolution. Within the research network CAOS (Catchments As Organized Systems), we have initiated and developed a novel and integrated observation platform in several catchments in Luxembourg. In 20 nested catchments covering three distinct geologies the subscale processes at the bedrock-soil-vegetation-atmosphere interface are being monitored at 46 sensor cluster locations. Each sensor cluster is designed to observe a variety of different fluxes and state variables above and below ground, in the saturated and unsaturated zone. The numbers of sensors are chosen to capture the spatial variability as well the average dynamics. At each of these sensor clusters three soil moisture profiles with sensors at different depths, four soil temperature profiles as well as matric potential, air temperature, relative humidity, global radiation, rainfall/throughfall, sapflow and shallow groundwater and stream water levels are measured continuously. In addition, most sensors also measure temperature (water, soil, atmosphere) and electrical conductivity. This setup allows us to determine the local water and energy balance at each of these sites. The discharge gauging sites in the nested catchments are also equipped with automatic water samplers to monitor water quality and water stable isotopes continuously. Furthermore, water temperature and electrical conductivity observations are extended to over 120 locations distributed across the entire stream network to capture the energy exchange between the groundwater, stream water and atmosphere. The measurements at the sensor clusters are complemented by hydrometeorological observations (rain radar, network of distrometers and dense network of precipitation gauges) and linked with high resolution meteorological models. In this

  17. A microwave scattering model for layered vegetation

    NASA Technical Reports Server (NTRS)

    Karam, Mostafa A.; Fung, Adrian K.; Lang, Roger H.; Chauhan, Narinder S.

    1992-01-01

    A microwave scattering model was developed for layered vegetation based on an iterative solution of the radiative transfer equation up to the second order to account for multiple scattering within the canopy and between the ground and the canopy. The model is designed to operate over a wide frequency range for both deciduous and coniferous forest and to account for the branch size distribution, leaf orientation distribution, and branch orientation distribution for each size. The canopy is modeled as a two-layered medium above a rough interface. The upper layer is the crown containing leaves, stems, and branches. The lower layer is the trunk region modeled as randomly positioned cylinders with a preferred orientation distribution above an irregular soil surface. Comparisons of this model with measurements from deciduous and coniferous forests show good agreements at several frequencies for both like and cross polarizations. Major features of the model needed to realize the agreement include allowance for: (1) branch size distribution, (2) second-order effects, and (3) tree component models valid over a wide range of frequencies.

  18. Variation in Soil Respiration across Soil and Vegetation Types in an Alpine Valley

    PubMed Central

    Rubin, Aurélie

    2016-01-01

    Background and Aims Soils of mountain regions and their associated plant communities are highly diverse over short spatial scales due to the heterogeneity of geological substrates and highly dynamic geomorphic processes. The consequences of this heterogeneity for biogeochemical transfers, however, remain poorly documented. The objective of this study was to quantify the variability of soil-surface carbon dioxide efflux, known as soil respiration (Rs), across soil and vegetation types in an Alpine valley. To this aim, we measured Rs rates during the peak and late growing season (July-October) in 48 plots located in pastoral areas of a small valley of the Swiss Alps. Findings Four herbaceous vegetation types were identified, three corresponding to different stages of primary succession (Petasition paradoxi in pioneer conditions, Seslerion in more advanced stages and Poion alpinae replacing the climactic forests), as well as one (Rumicion alpinae) corresponding to eutrophic grasslands in intensively grazed areas. Soils were developed on calcareous alluvial and colluvial fan deposits and were classified into six types including three Fluvisols grades and three Cambisols grades. Plant and soil types had a high level of co-occurrence. The strongest predictor of Rs was soil temperature, yet we detected additional explanatory power of sampling month, showing that temporal variation was not entirely reducible to variations in temperature. Vegetation and soil types were also major determinants of Rs. During the warmest month (August), Rs rates varied by over a factor three between soil and vegetation types, ranging from 2.5 μmol m-2 s-1 in pioneer environments (Petasition on Very Young Fluvisols) to 8.5 μmol m-2 s-1 in differentiated soils supporting nitrophilous species (Rumicion on Calcaric Cambisols). Conclusions Overall, this study provides quantitative estimates of spatial and temporal variability in Rs in the mountain environment, and demonstrates that estimations of

  19. Development of the IAP Dynamic Global Vegetation Model

    NASA Astrophysics Data System (ADS)

    Zeng, Xiaodong; Li, Fang; Song, Xiang

    2014-05-01

    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.

  20. Assessing the evolution of soil moisture and vegetation conditions during the 2012 United States flash drought

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study examines the evolution of several model-based and satellite-derived drought metrics sensitive to soil moisture and vegetation conditions during the extreme flash drought event that impacted major agricultural areas across the central U.S. during 2012. Standardized anomalies from the remo...

  1. Benchmarking LSM root-zone soil mositure predictions using satellite-based vegetation indices

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The application of modern land surface models (LSMs) to agricultural drought monitoring is based on the premise that anomalies in LSM root-zone soil moisture estimates can accurately anticipate the subsequent impact of drought on vegetation productivity and health. In addition, the water and energy ...

  2. The influence of vegetation and soil characteristics on active-layer thickness of permafrost soils in boreal forest.

    PubMed

    Fisher, James P; Estop-Aragonés, Cristian; Thierry, Aaron; Charman, Dan J; Wolfe, Stephen A; Hartley, Iain P; Murton, Julian B; Williams, Mathew; Phoenix, Gareth K

    2016-09-01

    Carbon release from thawing permafrost soils could significantly exacerbate global warming as the active-layer deepens, exposing more carbon to decay. Plant community and soil properties provide a major control on this by influencing the maximum depth of thaw each summer (active-layer thickness; ALT), but a quantitative understanding of the relative importance of plant and soil characteristics, and their interactions in determine ALTs, is currently lacking. To address this, we undertook an extensive survey of multiple vegetation and edaphic characteristics and ALTs across multiple plots in four field sites within boreal forest in the discontinuous permafrost zone (NWT, Canada). Our sites included mature black spruce, burned black spruce and paper birch, allowing us to determine vegetation and edaphic drivers that emerge as the most important and broadly applicable across these key vegetation and disturbance gradients, as well as providing insight into site-specific differences. Across sites, the most important vegetation characteristics limiting thaw (shallower ALTs) were tree leaf area index (LAI), moss layer thickness and understory LAI in that order. Thicker soil organic layers also reduced ALTs, though were less influential than moss thickness. Surface moisture (0-6 cm) promoted increased ALTs, whereas deeper soil moisture (11-16 cm) acted to modify the impact of the vegetation, in particular increasing the importance of understory or tree canopy shading in reducing thaw. These direct and indirect effects of moisture indicate that future changes in precipitation and evapotranspiration may have large influences on ALTs. Our work also suggests that forest fires cause greater ALTs by simultaneously decreasing multiple ecosystem characteristics which otherwise protect permafrost. Given that vegetation and edaphic characteristics have such clear and large influences on ALTs, our data provide a key benchmark against which to evaluate process models used to predict

  3. The influence of vegetation and soil characteristics on active-layer thickness of permafrost soils in boreal forest.

    PubMed

    Fisher, James P; Estop-Aragonés, Cristian; Thierry, Aaron; Charman, Dan J; Wolfe, Stephen A; Hartley, Iain P; Murton, Julian B; Williams, Mathew; Phoenix, Gareth K

    2016-09-01

    Carbon release from thawing permafrost soils could significantly exacerbate global warming as the active-layer deepens, exposing more carbon to decay. Plant community and soil properties provide a major control on this by influencing the maximum depth of thaw each summer (active-layer thickness; ALT), but a quantitative understanding of the relative importance of plant and soil characteristics, and their interactions in determine ALTs, is currently lacking. To address this, we undertook an extensive survey of multiple vegetation and edaphic characteristics and ALTs across multiple plots in four field sites within boreal forest in the discontinuous permafrost zone (NWT, Canada). Our sites included mature black spruce, burned black spruce and paper birch, allowing us to determine vegetation and edaphic drivers that emerge as the most important and broadly applicable across these key vegetation and disturbance gradients, as well as providing insight into site-specific differences. Across sites, the most important vegetation characteristics limiting thaw (shallower ALTs) were tree leaf area index (LAI), moss layer thickness and understory LAI in that order. Thicker soil organic layers also reduced ALTs, though were less influential than moss thickness. Surface moisture (0-6 cm) promoted increased ALTs, whereas deeper soil moisture (11-16 cm) acted to modify the impact of the vegetation, in particular increasing the importance of understory or tree canopy shading in reducing thaw. These direct and indirect effects of moisture indicate that future changes in precipitation and evapotranspiration may have large influences on ALTs. Our work also suggests that forest fires cause greater ALTs by simultaneously decreasing multiple ecosystem characteristics which otherwise protect permafrost. Given that vegetation and edaphic characteristics have such clear and large influences on ALTs, our data provide a key benchmark against which to evaluate process models used to predict

  4. Quantification of the uncertainties in soil and vegetation parameterizations for regional climate predictions

    NASA Astrophysics Data System (ADS)

    Breil, Marcus; Schädler, Gerd

    2016-04-01

    The aim of the german research program MiKlip II is the development of an operational climate prediction system that can provide reliable forecasts on a decadal time scale. Thereby, one goal of MiKlip II is to investigate the feasibility of regional climate predictions. Results of recent studies indicate that the regional climate is significantly affected by the interactions between the soil, the vegetation and the atmosphere. Thus, within the framework of MiKlip II a workpackage was established to assess the impact of these interactions on the regional decadal climate predictability. In a Regional Climate Model (RCM) the soil-vegetation-atmosphere interactions are represented in a Land Surface Model (LSM). Thereby, the LSM describes the current state of the land surface by calculating the soil temperature, the soil water content and the turbulent heat fluxes, serving the RCM as lower boundary condition. To be able to solve the corresponding equations, soil and vegetation processes are parameterized within the LSM. Such parameterizations are mainly derived from observations. But in most cases observations are temporally and spatially limited and consequently not able to represent the diversity of nature completely. Thus, soil and vegetation parameterizations always exhibit a certain degree of uncertainty. In the presented study, the uncertainties within a LSM are assessed by stochastic variations of the relevant parameterizations in VEG3D, a LSM developed at the Karlsruhe Institute of Technology (KIT). In a first step, stand-alone simulations of VEG3D are realized with varying soil and vegetation parameters, to identify sensitive model parameters. In a second step, VEG3D is coupled to the RCM COSMO-CLM. With this new model system regional decadal hindcast simulations, driven by global simulations of the Max-Planck-Institute for Meteorology Earth System Model (MPI-ESM), are performed for the CORDEX-EU domain in a resolution of 0.22°. The identified sensitive model

  5. Reflectance of vegetation, soil, and water

    NASA Technical Reports Server (NTRS)

    Wiegand, C. L. (Principal Investigator)

    1973-01-01

    The author has identified the following significant results. A ratio of MSS channels 5 and 7 (5/7) and 5 to 6 (5/6) signals resulted in a correct recognition of 86.9% of the members of representative crop and soil conditions, compared with recognitions of 60.0, 64.1, 74.1, and 81.4% for channels 4, 5, 6, and 7 taken individually. Based on this result a satellite channel ratio procedure has been developed that enhances line printer gray maps for more efficient experimental test site location in the CCT data. Because independent estimates are not available to judge acreage estmates derived from ERTS-1 data against, except for a few crops, an interpenetrating sample constituting 3.5% of the county is ground truthed periodically. The crop of land uses and their acreages, respectively, as estimated from the interpenetrating samples, are: cotton, 129, 714; sorghum, 182,783; mixed citrus, 53,954; oranges, 16,929; grapefruit, 13,863; rangeland, 137,845; and, improved pastures, 57.169.

  6. Plant functional diversity enhances associations of soil fungal diversity with vegetation and soil in the restoration of semiarid sandy grassland.

    PubMed

    Zuo, Xiaoan; Wang, Shaokun; Lv, Peng; Zhou, Xin; Zhao, Xueyong; Zhang, Tonghui; Zhang, Jing

    2016-01-01

    The trait-based approach shows that plant functional diversity strongly affects ecosystem properties. However, few empirical studies show the relationship between soil fungal diversity and plant functional diversity in natural ecosystems. We investigated soil fungal diversity along a restoration gradient of sandy grassland (mobile dune, semifixed dune, fixed dune, and grassland) in Horqin Sand Land, northern China, using the denaturing gradient gel electrophoresis of 18S rRNA and gene sequencing. We also examined associations of soil fungal diversity with plant functional diversity reflected by the dominant species' traits in community (community-weighted mean, CWM) and the dispersion of functional trait values (FD is). We further used the structure equation model (SEM) to evaluate how plant richness, biomass, functional diversity, and soil properties affect soil fungal diversity in sandy grassland restoration. Soil fungal richness in mobile dune and semifixed dune was markedly lower than those of fixed dune and grassland (P < 0.05). Soil fungal richness was positively associated with plant richness, biomass, CWM plant height, and soil gradient aggregated from the principal component analysis, but SEM results showed that plant richness and CWM plant height determined by soil properties were the main factors exerting direct effects. Soil gradient increased fungal richness through indirect effect on vegetation rather than direct effect. The negative indirect effect of FDis on soil fungal richness was through its effect on plant biomass. Our final SEM model based on plant functional diversity explained nearly 70% variances of soil fungal richness. Strong association of soil fungal richness with the dominant species in the community supported the mass ratio hypothesis. Our results clearly highlight the role of plant functional diversity in enhancing associations of soil fungal diversity with community structure and soil properties in sandy grassland ecosystems.

  7. Activated carbon adsorption of PAHs from vegetable oil used in soil remediation.

    PubMed

    Gong, Zongqiang; Alef, Kassem; Wilke, Berndt-Michael; Li, Peijun

    2007-05-01

    Vegetable oil has been proven to be advantageous as a non-toxic, cost-effective and biodegradable solvent to extract polycyclic aromatic hydrocarbons (PAHs) from contaminated soils for remediation purposes. The resulting vegetable oil contained PAHs and therefore required a method for subsequent removal of extracted PAHs and reuse of the oil in remediation processes. In this paper, activated carbon adsorption of PAHs from vegetable oil used in soil remediation was assessed to ascertain PAH contaminated oil regeneration. Vegetable oils, originating from lab scale remediation, with different PAH concentrations were examined to study the adsorption of PAHs on activated carbon. Batch adsorption tests were performed by shaking oil-activated carbon mixtures in flasks. Equilibrium data were fitted with the Langmuir and Freundlich isothermal models. Studies were also carried out using columns packed with activated carbon. In addition, the effects of initial PAH concentration and activated carbon dosage on sorption capacities were investigated. Results clearly revealed the effectiveness of using activated carbon as an adsorbent to remove PAHs from the vegetable oil. Adsorption equilibrium of PAHs on activated carbon from the vegetable oil was successfully evaluated by the Langmuir and Freundlich isotherms. The initial PAH concentrations and carbon dosage affected adsorption significantly. The results indicate that the reuse of vegetable oil was feasible.

  8. Soil moisture and evapotranspiration of wetlands vegetation habitats retrieved from satellite images

    NASA Astrophysics Data System (ADS)

    Dabrowska-Zielinska, K.; Budzynska, M.; Kowalik, W.; Turlej, K.

    2010-08-01

    The research has been carried out in Biebrza Ramsar Convention test site situated in the N-E part of Poland. Data from optical and microwave satellite images have been analysed and compared to the detailed soil-vegetation ground truth measurements conducted during the satellite overpasses. Satellite data applied for the study include: ENVISAT.ASAR, ENVISAT.MERIS, ALOS.PALSAR, ALOS.AVNIR-2, ALOS.PRISM, TERRA.ASTER, and NOAA.AVHRR. Optical images have been used for classification of wetlands vegetation habitats and vegetation surface roughness expressed by LAI. Also, heat fluxes have been calculated using NOAA.AVHRR data and meteorological data. Microwave images have been used for the assessment of soil moisture. For each of the classified wetlands vegetation habitats the relationship between soil moisture and backscattering coefficient has been examined, and the best combination of microwave variables (wave length, incidence angle, polarization) has been used for mapping and monitoring of soil moisture. The results of this study give possibility to improve models of water cycle over wetlands ecosystems by adding information about soil moisture and surface heat fluxes derived from satellite images. Such information is very essential for better protection of the European sensitive wetland ecosystems. ENVISAT and ALOS images have been obtained from ESA for AO ID 122 and AOALO.3742 projects.

  9. The effect of soil surface sealing on vegetation water uptake along a dry climatic gradient

    NASA Astrophysics Data System (ADS)

    Sela, Shai; Svoray, Tal; Assouline, Shmuel

    2015-09-01

    Soil surface sealing is a widespread natural process occurring frequently in bare soil areas between vegetation patches. The low hydraulic conductivity that characterizes the seal layer reduces both infiltration and evaporation fluxes from the soil, and thus has the potential to affect local vegetation water uptake (VWU). This effect is investigated here using experimental data, 2-D physically based modeling, and a long-term climatic data set from three dry sites presenting a climatic gradient in the Negev Desert, Israel. The Feddes VWU parameters for the dominant shrub at the study site (Sarcopoterium spinosum) were acquired using lysimeter experiments. The results indicate that during the season surface sealing could either increase or decrease VWU depending on initial soil water content, rainfall intensity, and the duration of the subsequent drying intervals. These factors have a marked effect on interannual variability of the seal layer effect on VWU, which on average was found to be 26% higher under sealed conditions than in the case of unsealed soil surfaces. The seal layer was found to reduce the period where the vegetation was under water stress by 31% compared with unsealed conditions. This effect was more pronounced for seasons with total rainfall depth higher than 10 cm/yr, and was affected by interseasonal climatic variability. These results shed light on the importance of surface sealing in dry environments and its contribution to the resilience of woody vegetation.

  10. Vegetation establishment on soil-amended weathered fly ash

    SciTech Connect

    Semalulu, O.; Barnhisel, R.I.; Witt, S.

    1998-12-31

    A field study was conducted with the following objectives in mind: (1) to study the effect of soil addition to weathered fly ash on the establishment and survival of different grasses and legumes, (2) to identify suitable grasses and/or legume species for vegetation of fly ash, (3) to study the fertilizer N and P requirements for successful vegetation establishment on fly ash and ash-soil mixtures, (4) to examine the nutrient composition of the plant species tested, and (5) to study the plant availability of P from fly ash and ash-soil mixtures. Three rooting media were used: weathered fly ash, and 33% or 50% soil blended with the ash. Four experiments were established on each of these media to evaluate warm season grasses in pure stands, warm season grasses inter-seeded with legumes, cool season grasses, and cool season grasses inter-seeded with legumes. Soil used in this study was more acidic than the fly ash. Only the results from characterization of the rooting media, ground cover, and yield will be presented here.

  11. 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)

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

    2013-12-01

    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

  12. Assessment of regional biomass-soil relationships using vegetation indexes

    SciTech Connect

    Lozano-Garcia, D.F.; Fernandez, R.N.; Johannsen, C.J. )

    1991-03-01

    This paper reports on data from the NOAA-10 Advanced Very High Resolution Radiometer (AVHRR) collected over the midwestern United States for the 1987 and 1988 growing seasons. A Normalized Difference Vegetation Index (NDVI) transformation was performed using the two optical bands of the sensor (0.58-0.68 {mu}m and 0.72-1.10 {mu}m). The NDVI is related to the amount of active photosynthetic biomass present on the ground. Samples of NDVI values over 45 fields representing 8 soil associations throughout the State of Indiana were collected to assess the effect of soil conditions and acquisition data on the spectral response of the vegetation, as shown by the NDVI's.

  13. Soil moisture modeling review

    NASA Technical Reports Server (NTRS)

    Hildreth, W. W.

    1978-01-01

    A determination of the state of the art in soil moisture transport modeling based on physical or physiological principles was made. It was found that soil moisture models based on physical principles have been under development for more than 10 years. However, these models were shown to represent infiltration and redistribution of soil moisture quite well. Evapotranspiration has not been as adequately incorporated into the models.

  14. A comparison of soil properties under four vegetation units from six metalliferous hills in Katanga

    NASA Astrophysics Data System (ADS)

    Kaya, Donato; Gregory, Mahy; Michel, Ngongo; Gilles, Colinet

    2013-04-01

    In Katanga (Democratic Republic of Congo), numerous metalliferous hills are distributed along what is called the copperhill belt from Kolwezi to Lubumbashi. Very specific vegetation developed on these hills within the miombo forest in response to very specific soil conditions, among which the copper content. Previous studies have already shown the existence of gradients of copper from the mineralized rocks outcropping at the top of the hills to the foot slopes on colluviums. After a characterization of the vertical variability of soil properties in pits distributed along the main slopes, we investigated the soil-vegetation relationships in six hills located between the towns of Tenke and Fungurume. Observation 1-square meter plots were installed in four vegetation units and sixty of them were selected according to their relative importance on the six hills. The soil from the top 10cm was sampled and analyzed for pH, Total Organic Carbon, available P, K, Mg, Ca, Cu, Co and Mn and soluble Cu and Co. Analysis of variance was performed in order to assess whether the effects of the "Hill" and of the "Vegetation Unit" were significant to explain soil chemical variability. Additionally, short transects were sampled at the boundaries from adjacent vegetation units in order to evaluate the gradual or rough nature of change in soil properties under these units. The results indicate that the six hills can not be considered as different for pH and available nutrients, excepted K, nor for the available Cu and Mn. Only TOC and Co contents were differing, mainly from one hill compared to the other five. The vegetation effect is significant for almost every studied soil characteristics, to the exception of Ca and Mn. Soluble Cu and Co significantly correlate to available Cu and Co, respectively. The pH variations however explain local departures from linear regression. The ANOVA models take into account 30 to 60% of the variations of soil properties. The study of the boundaries

  15. Using high-resolution radar images to determine vegetation cover for soil erosion assessments.

    PubMed

    Bargiel, D; Herrmann, S; Jadczyszyn, J

    2013-07-30

    Healthy soils are crucial for human well-being. Because soils are threatened worldwide, politicians recognize the need for soil protection. For example, the European Commission has launched the Thematic Strategy for Soil Protection, which requests the European member states to identify high risk areas for soil degradation. Most states use the Universal Soil Loss Equation (USLE) to assess soil erosion risk at the national scale. The USLE includes different factors, one of them is the vegetation cover and management factor (C factor). Modern satellite-based radar sensors now provide highly accurate vegetation cover data, enabling opportunities to improve the accuracy of the C factor. The presented study proves the suitability for C factor determination based on a multi-temporal classification of high-resolution radar images. Further USLE factors were derived from existing data sources (meteorological data, soil maps, digital elevation model) to conduct an USLE-based soil erosion assessment. The resulting map illustrates a qualitative assessment for soil erosion risk within a plot of about 7*12 km in an agricultural region in Poland that is very susceptible to soil erosion processes. A high erosion risk of more than 10 tonnes per ha and year was assessed to occur on 13.6% (646 ha) of the agricultural areas within the investigated plot. Further 7.8% (372 ha) of agricultural land is threaten by a medium risk of 5-10 tonnes per ha and year. Such a spatial information about areas of high or medium soil erosion risk are crucial for the development of strategies for the protection of soils.

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

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

    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.

  17. Surface modeling of soil antibiotics.

    PubMed

    Shi, Wen-jiao; Yue, Tian-xiang; Du, Zheng-ping; Wang, Zong; Li, Xue-wen

    2016-02-01

    Large numbers of livestock and poultry feces are continuously applied into soils in intensive vegetable cultivation areas, and then some veterinary antibiotics are persistent existed in soils and cause health risk. For the spatial heterogeneity of antibiotic residues, developing a suitable technique to interpolate soil antibiotic residues is still a challenge. In this study, we developed an effective interpolator, high accuracy surface modeling (HASM) combined vegetable types, to predict the spatial patterns of soil antibiotics, using 100 surface soil samples collected from an intensive vegetable cultivation area located in east of China, and the fluoroquinolones (FQs), including ciprofloxacin (CFX), enrofloxacin (EFX) and norfloxacin (NFX), were analyzed as the target antibiotics. The results show that vegetable type is an effective factor to be combined to improve the interpolator performance. HASM achieves less mean absolute errors (MAEs) and root mean square errors (RMSEs) for total FQs (NFX+CFX+EFX), NFX, CFX and EFX than kriging with external drift (KED), stratified kriging (StK), ordinary kriging (OK) and inverse distance weighting (IDW). The MAE of HASM for FQs is 55.1 μg/kg, and the MAEs of KED, StK, OK and IDW are 99.0 μg/kg, 102.8 μg/kg, 106.3 μg/kg and 108.7 μg/kg, respectively. Further, RMSE simulated by HASM for FQs (CFX, EFX and NFX) are 106.2 μg/kg (88.6 μg/kg, 20.4 μg/kg and 39.2 μg/kg), and less 30% (27%, 22% and 36%), 33% (27%, 27% and 43%), 38% (34%, 23% and 41%) and 42% (32%, 35% and 51%) than the ones by KED, StK, OK and IDW, respectively. HASM also provides better maps with more details and more consistent maximum and minimum values of soil antibiotics compared with the measured data. The better performance can be concluded that HASM takes the vegetable type information as global approximate information, and takes local sampling data as its optimum control constraints.

  18. Surface modeling of soil antibiotics.

    PubMed

    Shi, Wen-jiao; Yue, Tian-xiang; Du, Zheng-ping; Wang, Zong; Li, Xue-wen

    2016-02-01

    Large numbers of livestock and poultry feces are continuously applied into soils in intensive vegetable cultivation areas, and then some veterinary antibiotics are persistent existed in soils and cause health risk. For the spatial heterogeneity of antibiotic residues, developing a suitable technique to interpolate soil antibiotic residues is still a challenge. In this study, we developed an effective interpolator, high accuracy surface modeling (HASM) combined vegetable types, to predict the spatial patterns of soil antibiotics, using 100 surface soil samples collected from an intensive vegetable cultivation area located in east of China, and the fluoroquinolones (FQs), including ciprofloxacin (CFX), enrofloxacin (EFX) and norfloxacin (NFX), were analyzed as the target antibiotics. The results show that vegetable type is an effective factor to be combined to improve the interpolator performance. HASM achieves less mean absolute errors (MAEs) and root mean square errors (RMSEs) for total FQs (NFX+CFX+EFX), NFX, CFX and EFX than kriging with external drift (KED), stratified kriging (StK), ordinary kriging (OK) and inverse distance weighting (IDW). The MAE of HASM for FQs is 55.1 μg/kg, and the MAEs of KED, StK, OK and IDW are 99.0 μg/kg, 102.8 μg/kg, 106.3 μg/kg and 108.7 μg/kg, respectively. Further, RMSE simulated by HASM for FQs (CFX, EFX and NFX) are 106.2 μg/kg (88.6 μg/kg, 20.4 μg/kg and 39.2 μg/kg), and less 30% (27%, 22% and 36%), 33% (27%, 27% and 43%), 38% (34%, 23% and 41%) and 42% (32%, 35% and 51%) than the ones by KED, StK, OK and IDW, respectively. HASM also provides better maps with more details and more consistent maximum and minimum values of soil antibiotics compared with the measured data. The better performance can be concluded that HASM takes the vegetable type information as global approximate information, and takes local sampling data as its optimum control constraints. PMID:26613514

  19. The Role of Vegetation and Mulch in Mitigating the Impact of Raindrops on Soils in Urban Vegetated Green Infrastructure Systems

    NASA Astrophysics Data System (ADS)

    Alizadehtazi, B.; Montalto, F. A.; Sjoblom, K.

    2014-12-01

    Raindrop impulses applied to soils can break up larger soil aggregates into smaller particles, dispersing them from their original position. The displaced particles can self-stratify, with finer particles at the top forming a crust. Occurrence of this phenomenon reduces the infiltration rate and increases runoff, contributing to downstream flooding, soil erosion, and non point source pollutant loads. Unprotected soil surfaces (e.g. without vegetation canopies, mulch, or other materials), are more susceptible to crust formation due to the higher kinetic energy associated with raindrop impact. By contrast, soil that is protected by vegetation canopies and mulch layers is less susceptible to crust formation, since these surfaces intercept raindrops, dissipating some of their kinetic energy prior to their impact with the soil. Within this context, this presentation presents preliminary laboratory work conducted using a rainfall simulator to determine the ability of new urban vegetation and mulch to minimize soil crust formation. Three different scenarios are compared: a) bare soil, b) soil with mulch cover, and c) soil protected by vegetation canopies. Soil moisture, surface penetration resistance, and physical measurements of the volume of infiltrate and runoff are made on all three surface treatments after simulated rainfall events. The results are used to develop recommendations regarding surface treatment in green infrastructure (GI) system designs, namely whether heavily vegetated GI facilities require mulching to maintain infiltration capacity.

  20. Decadal predictability of soil water, vegetation, and wildfire frequency over North America

    NASA Astrophysics Data System (ADS)

    Chikamoto, Yoshimitsu; Timmermann, Axel; Stevenson, Samantha; DiNezio, Pedro; Langford, Sally

    2015-10-01

    The potential decadal predictability of land hydrological and biogeochemical variables in North America is examined using a 900-year-long pre-industrial control simulation, conducted with the NCAR Community Earth System Model (CESM) version 1.0.3. The leading modes of simulated North American precipitation and soil water storage are characterized essentially by qualitatively similar meridional seesaw patterns associated with the activity of the westerly jet. Whereas the corresponding precipitation variability can be described as a white noise stochastic process, power spectra of vertically integrated soil water exhibit significant redness on timescales of years to decades, since the predictability of soil water storage arises mostly from the integration of precipitation variability. As a result, damped persistence hindcasts following a 1st order Markov process are skillful with lead times of up to several years. This potential multi-year skill estimate is consistent with ensemble hindcasts conducted with the CESM for various initial conditions. Our control simulation further suggests that decadal variations in soil water storage also affect vegetation and wildfire occurrences. The long-term potential predictability of soil water variations in combination with the slow regrowth of vegetation after major disruptions leads to enhanced predictability on decadal timescales for vegetation, terrestrial carbon stock, and fire frequency, in particular in the Southern United States (US)/Mexico region. By contrast, the prediction skill of fire frequency in the Northern US is limited to 1 year. Our results demonstrate that skillful decadal predictions of soil water storage, carbon stock, and fire frequency are feasible with proper initialization of soil conditions. Although the potential predictability in our idealized modeling framework would overestimate the real predictability of the coupled climate-land-vegetation system, the decadal climate prediction may become

  1. 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)

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

    2014-05-01

    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.

  2. Evaluation of MODIS NDVI and NDWI for vegetation drought monitoring using Oklahoma Mesonet soil moisture data

    NASA Astrophysics Data System (ADS)

    Gu, Yingxin; Hunt, Eric; Wardlow, Brian; Basara, Jeffrey B.; Brown, Jesslyn F.; Verdin, James P.

    2008-11-01

    The evaluation of the relationship between satellite-derived vegetation indices (normalized difference vegetation index and normalized difference water index) and soil moisture improves our understanding of how these indices respond to soil moisture fluctuations. Soil moisture deficits are ultimately tied to drought stress on plants. The diverse terrain and climate of Oklahoma, the extensive soil moisture network of the Oklahoma Mesonet, and satellite-derived indices from the Moderate Resolution Imaging Spectroradiometer (MODIS) provided an opportunity to study correlations between soil moisture and vegetation indices over the 2002-2006 growing seasons. Results showed that the correlation between both indices and the fractional water index (FWI) was highly dependent on land cover heterogeneity and soil type. Sites surrounded by relatively homogeneous vegetation cover with silt loam soils had the highest correlation between the FWI and both vegetation-related indices (r~0.73), while sites with heterogeneous vegetation cover and loam soils had the lowest correlation (r~0.22).

  3. Soil TPH concentration estimation using vegetation indices in an oil polluted area of eastern China.

    PubMed

    Zhu, Linhai; Zhao, Xuechun; Lai, Liming; Wang, Jianjian; Jiang, Lianhe; Ding, Jinzhi; Liu, Nanxi; Yu, Yunjiang; Li, Junsheng; Xiao, Nengwen; Zheng, Yuanrun; Rimmington, Glyn M

    2013-01-01

    Assessing oil pollution using traditional field-based methods over large areas is difficult and expensive. Remote sensing technologies with good spatial and temporal coverage might provide an alternative for monitoring oil pollution by recording the spectral signals of plants growing in polluted soils. Total petroleum hydrocarbon concentrations of soils and the hyperspectral canopy reflectance were measured in wetlands dominated by reeds (Phragmites australis) around oil wells that have been producing oil for approximately 10 years in the Yellow River Delta, eastern China to evaluate the potential of vegetation indices and red edge parameters to estimate soil oil pollution. The detrimental effect of oil pollution on reed communities was confirmed by the evidence that the aboveground biomass decreased from 1076.5 g m(-2) to 5.3 g m(-2) with increasing total petroleum hydrocarbon concentrations ranging from 9.45 mg kg(-1) to 652 mg kg(-1). The modified chlorophyll absorption ratio index (MCARI) best estimated soil TPH concentration among 20 vegetation indices. The linear model involving MCARI had the highest coefficient of determination (R(2) = 0.73) and accuracy of prediction (RMSE = 104.2 mg kg(-1)). For other vegetation indices and red edge parameters, the R(2) and RMSE values ranged from 0.64 to 0.71 and from 120.2 mg kg(-1) to 106.8 mg kg(-1) respectively. The traditional broadband normalized difference vegetation index (NDVI), one of the broadband multispectral vegetation indices (BMVIs), produced a prediction (R(2) = 0.70 and RMSE = 110.1 mg kg(-1)) similar to that of MCARI. These results corroborated the potential of remote sensing for assessing soil oil pollution in large areas. Traditional BMVIs are still of great value in monitoring soil oil pollution when hyperspectral data are unavailable.

  4. Effect of grazing on vegetation and soil of the heuweltjieveld in the Succulent Karoo, South Africa

    NASA Astrophysics Data System (ADS)

    Schmiedel, Ute; Röwer, Inga Ute; Luther-Mosebach, Jona; Dengler, Jürgen; Oldeland, Jens; Gröngröft, Alexander

    2016-11-01

    We asked how historical and recent grazing intensity affect the patchy landscape of the heuweltjieveld in the semi-arid biodiversity hotspot Succulent Karoo. The study was carried out on a communal farmland 80 km south-west of Springbok, in Namaqualand. Heuweltjies are roughly circular earth mounds that are regularly distributed in this landscape. We sampled plant species and life-form composition, diversity measures, habitat and soil variables in 100 m2 plots, placed in three visually distinguishable heuweltjie zones (centre, fringe, and matrix) and distributed across grazing camps with different recent and historic grazing intensities. Differences between heuweltjie zones were assessed with ANOVAs and multiple linear regressions. The effect of past and recent grazing intensity on soil and plant variables was analysed by Generalized Linear Models for each heuweltjie zone separately. The three zones constituted clearly distinguishable units in terms of vegetation and soil characteristics. Soil pH and cover of annual plants increased from matrix to centres, while total vegetation cover, species richness and perennial plant cover decreased in the same direction. Historic (pre-2000) grazing patterns had the strongest effects on fringes, showing the strongest soil and vegetation-related signs of overutilization with increased stocking density. Centres showed signs of overutilization irrespective of the stocking density. The much shorter exposure to recent grazing pattern (post-2000), which was nearly inverse to the historic grazing pattern, showed increase of vegetation cover (centres) and species richness (matrix) with recent grazing intensity. We interpret these effects as still visible responses of the lower grazing intensity in these camps during the historic period. No recovery under recent grazing was observed at any of the zones. We conclude that irrespective of their conducive growing conditions, once transformed to a disturbed state, heuweltjie centres recover

  5. Soil TPH concentration estimation using vegetation indices in an oil polluted area of eastern China.

    PubMed

    Zhu, Linhai; Zhao, Xuechun; Lai, Liming; Wang, Jianjian; Jiang, Lianhe; Ding, Jinzhi; Liu, Nanxi; Yu, Yunjiang; Li, Junsheng; Xiao, Nengwen; Zheng, Yuanrun; Rimmington, Glyn M

    2013-01-01

    Assessing oil pollution using traditional field-based methods over large areas is difficult and expensive. Remote sensing technologies with good spatial and temporal coverage might provide an alternative for monitoring oil pollution by recording the spectral signals of plants growing in polluted soils. Total petroleum hydrocarbon concentrations of soils and the hyperspectral canopy reflectance were measured in wetlands dominated by reeds (Phragmites australis) around oil wells that have been producing oil for approximately 10 years in the Yellow River Delta, eastern China to evaluate the potential of vegetation indices and red edge parameters to estimate soil oil pollution. The detrimental effect of oil pollution on reed communities was confirmed by the evidence that the aboveground biomass decreased from 1076.5 g m(-2) to 5.3 g m(-2) with increasing total petroleum hydrocarbon concentrations ranging from 9.45 mg kg(-1) to 652 mg kg(-1). The modified chlorophyll absorption ratio index (MCARI) best estimated soil TPH concentration among 20 vegetation indices. The linear model involving MCARI had the highest coefficient of determination (R(2) = 0.73) and accuracy of prediction (RMSE = 104.2 mg kg(-1)). For other vegetation indices and red edge parameters, the R(2) and RMSE values ranged from 0.64 to 0.71 and from 120.2 mg kg(-1) to 106.8 mg kg(-1) respectively. The traditional broadband normalized difference vegetation index (NDVI), one of the broadband multispectral vegetation indices (BMVIs), produced a prediction (R(2) = 0.70 and RMSE = 110.1 mg kg(-1)) similar to that of MCARI. These results corroborated the potential of remote sensing for assessing soil oil pollution in large areas. Traditional BMVIs are still of great value in monitoring soil oil pollution when hyperspectral data are unavailable. PMID:23342066

  6. The influence of vegetation on soil water repellency-markers and soil hydrophobicity.

    PubMed

    Mao, Jiefei; Nierop, Klaas G J; Rietkerk, Max; Sinninghe Damsté, Jaap S; Dekker, Stefan C

    2016-10-01

    Soil water repellency (SWR) markers are defined as hydrophobic compounds in soil causing SWR and are mainly derived from plants. Previous studies have shown the types and abundance of SWR-markers in soils. However, how these SWR-markers are exactly related to SWR and their origin is poorly understood. This study aims to understand the relationship between SWR-markers, vegetation type and cover and SWR for a simple sandy soil ecosystem, consisting of oaks with sedge and six grass species. All the soil (at different depth) and vegetation samples were collected in the field along a 6m transect, starting from an oak tree. Further along the transect grasses and sedges became more abundant. Free and ester-bound lipids from soils and plant leaves/roots were obtained using a sequential extraction method and identified by gas chromatography-mass spectrometry. Significant linear correlations were found between the main soil characteristics, such as total organic carbon content, and SWR. Single long-chain (>C20) SWR-markers derived from both plant leaf waxes and roots positively related to SWR. Both ester-bound ω-hydroxy fatty acids and C22 and C24 α,ω-dicarboxylic acids were predominantly present in the grass roots, but to a lesser extent in the roots of oak and sedge. These suberin-derived ω-hydroxy fatty acids and α,ω-dicarboxylic acids characteristic of roots could well predict the SWR. Additionally, the SWR predictors abundantly present in the soils matched well with high concentrations of the corresponding biomarkers in the dominant vegetation species that covered the soils. Our analyses demonstrated that grass roots influenced SWR more due to their more substantial contribution of organic matter to the topsoils than oak roots. This led to a stronger SWR of the soils covered with grass than those covered with oak vegetation. PMID:27236626

  7. Transfer of cadmium from soil to vegetable in the Pearl River Delta area, South China.

    PubMed

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

    2014-01-01

    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 (y = ax(b)), 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.

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

    PubMed Central

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

    2014-01-01

    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

  9. [Effect of vegetation types on soil respiration characteristics on a smaller scale].

    PubMed

    Yan, Jun-Xia; Li, Hong-Jian; Tang, Yi; Zhang, Yi-Hui

    2009-11-01

    Soil respiration was measured from April 2005 to December 2007 using a LICOR-6400-09 chamber connecting a LiCor-6400 portable photosynthesis system at 3 sites with same elevation and soil texture but different vegetation types. The results indicated that seasonal trend of soil respiration showed a distinct temporal change with the higher values in summer and autumn months and the lower values in winter and spring. Annual means (March to December) of soil respiration for 3 the sampling sites were(3.58 +/- 2.50), (3.82 +/- 2.75) and (4.42 +/- 3.38) micromol x (m2 x s)(-1) (p > 0.05), respectively. Released annual amount (March to December) of CO2 efflux from 3 sites was from 854.9 to 1 297.2 g x (m2 x a)(-1) and the amount was no difference between sites and among years. The fitted exponential equations of soil respiration and soil temperature for 3 sites were all significant with the R2 from 0.61 to 0.81, and the Q10 and R10 calculated from fitted parameters of the equations ranged from 2.60 to 4.50, and from 1.70 to 3.02 micromol x (m2 x s)(-1). The relationships between soil respiration and soil water content were not significant for all 3 sites with a maximum R2 of the regression equations only 0.12 (p > 0.05). However, when the soil temperature was above 10 degrees C, the relationships between soil respiration and soil water content was significant (p < 0.05). Four combined regression equations including soil temperature and soil water content could be used to model relationships between soil respiration and both soil temperature and soil water content together, with the R2 most above 0.7, and maximum of 0.91. PMID:20063717

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

    SciTech Connect

    Hoffman, F.O.

    1982-04-01

    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 -/.

  11. Estimating Sahelian and East African soil moisture using the Normalized Difference Vegetation Index

    NASA Astrophysics Data System (ADS)

    McNally, A.; Funk, C.; Husak, G. J.; Michaelsen, J.; Cappelaere, B.; Demarty, J.; Pellarin, T.; Young, T. P.; Caylor, K. K.; Riginos, C.; Veblen, K. E.

    2013-06-01

    Rainfall gauge networks in Sub-Saharan Africa are inadequate for assessing Sahelian agricultural drought, hence satellite-based estimates of precipitation and vegetation indices such as the Normalized Difference Vegetation Index (NDVI) provide the main source of information for early warning systems. While it is common practice to translate precipitation into estimates of soil moisture, it is difficult to quantitatively compare precipitation and soil moisture estimates with variations in NDVI. In the context of agricultural drought early warning, this study quantitatively compares rainfall, soil moisture and NDVI using a simple statistical model to translate NDVI values into estimates of soil moisture. The model was calibrated using in-situ soil moisture observations from southwest Niger, and then used to estimate root zone soil moisture across the African Sahel from 2001-2012. We then used these NDVI-soil moisture estimates (NSM) to quantify agricultural drought, and compared our results with a precipitation-based estimate of soil moisture (the Antecedent Precipitation Index, API), calibrated to the same in-situ soil moisture observations. We also used in-situ soil moisture observations in Mali and Kenya to assess performance in other water-limited locations in sub Saharan Africa. The separate estimates of soil moisture were highly correlated across the semi-arid, West and Central African Sahel, where annual rainfall exhibits a uni-modal regime. We also found that seasonal API and NDVI-soil moisture showed high rank correlation with a crop water balance model, capturing known agricultural drought years in Niger, indicating that this new estimate of soil moisture can contribute to operational drought monitoring. In-situ soil moisture observations from Kenya highlighted how the rainfall-driven API needs to be recalibrated in locations with multiple rainy seasons (e.g., Ethiopia, Kenya, and Somalia). Our soil moisture estimates from NDVI, on the other hand, performed

  12. Derivation of soil thresholds for lead applying species sensitivity distribution: A case study for root vegetables.

    PubMed

    Ding, Changfeng; Ma, Yibing; Li, Xiaogang; Zhang, Taolin; Wang, Xingxiang

    2016-02-13

    The combination of food quality standard and soil-plant transfer models can be used to derive critical limits of heavy metals for agricultural soils. In this paper, a robust methodology is presented, taking the variations of plant species and cultivars and soil properties into account to derive soil thresholds for lead (Pb) applying species sensitivity distribution (SSD). Three species of root vegetables (four cultivars each for radish, carrot, and potato) were selected to investigate their sensitivity differences for accumulating Pb through greenhouse experiment. Empirical soil-plant transfer model was developed from carrot New Kuroda grown in twenty-one soils covering a wide variation in physicochemical properties and was used to normalize the bioaccumulation data of non-model cultivars. The relationship was then validated to be reliable and would not cause over-protection using data from field experimental sites and published independent studies. The added hazardous concentration for protecting 95% of the cultivars not exceeding the food quality standard (HC5add) were then calculated from the Burr Type III function fitted SSD curves. The derived soil Pb thresholds based on the added risk approach (total soil concentration subtracting the natural background part) were presented as continuous or scenario criteria depending on the combination of soil pH and CEC. PMID:26513560

  13. Soil management of copper mine tailing soils--sludge amendment and tree vegetation could improve biological soil quality.

    PubMed

    Asensio, Verónica; Covelo, Emma F; Kandeler, Ellen

    2013-07-01

    Mine soils at the depleted copper mine in Touro (Northwest Spain) are physico-chemically degraded and polluted by chromium and copper. To increase the quality of these soils, some areas at this mine have been vegetated with eucalyptus or pines, amended with sludges, or received both treatments. Four sites were selected at the Touro mine tailing in order to evaluate the effect of these different reclamation treatments on the biological soil quality: (1) Control (untreated), (2) Forest (vegetated), (3) Sludge (amended with sludges) and (4) Forest+Sludge (vegetated and amended). The new approach of the present work is that we evaluated the effect of planting trees or/and amending with sludges on the biological soil quality of mine sites polluted by metals under field conditions. The addition of sludges to mine sites recovered the biological quality of the soil, while vegetating with trees did not increase microbial biomass and function to the level of unpolluted sites. Moreover, amending with sludges increased the efficiency of the soil's microbial community to metabolize C and N, which was indicated by the decrease of the specific enzyme activities and the increase in the ratio Cmic:Nmic (shift towards predominance of fungi instead of bacteria). However, the high Cu and Cr concentrations still have negative influence on the microorganisms in all the treated soils. For the future remediation of mine soils, we recommend periodically adding sludge and planting native legume species.

  14. Discrete random media techniques for microwave modeling of vegetated terrain

    NASA Technical Reports Server (NTRS)

    Lang, Roger H.

    1991-01-01

    Microwave remote sensing models of vegetated terrain are investigated. The problem is to determine canopy characteristics such as biomass, canopy height, and the moisture of the underlying soil. The report describes a discrete scatter model which has been employed to model backscatter in the active (radar) case and to model brightness temperature in the passive (radiometric) case. The acquisition of ground truth data is discussed, as well as the comparison of theory and experiment. The overall conclusion of the work has been that the discrete scatter model in conjunction with efficient scatter algorithms and the distorted Born approximation is a most appropriate methodology to use for modeling purposes in the microwave region.

  15. Scaling relationships for soil formation and edaphic controls on vegetation growth

    NASA Astrophysics Data System (ADS)

    Hunt, A. G.; Ghanbarian, B.

    2015-12-01

    Critical path analysis (CPA) is suited to calculating the hydraulic conductivity, K, of heterogeneous porous media by quantifying of paths of least resistance. Whenever CPA could be used to calculate K, advective transport scaling relationships from percolation theory should describe solute transport. Two solute transport relationships are applied to predict soil development and edaphic constraints on natural vegetation growth. These results use known exponents from percolation theory and known subsurface flow velocities. The typical flow velocity itself constrains optimal growth rates of cultivars. The percolation scaling relationship constraining vegetation growth is shown to be in accord with data over time scales from hours to 100,000 years, including over a dozen studies (and two models) of tree growth. The scaling function for soil development explains time scales for formation of soils from years to hundreds of millions of years. Data on soil development comes from 23 different studies. The key unification is the common origin of the time and space coordinates for all three relationships in the time of transport through a single pore of roughly micron size at a typical subsurface pore-scale flow velocity. The distinction in evolving time scales is primarily a result of the hierarchical nature of vascular plant root systems, which speed up nutrient access relative to physical transport rates in the soil. The results help explain reduction in forest productivity with age, diminishing soil production with time, and the temporal distinction between the relevance of chemical and biological processes in soils to the global carbon cycle.

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    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.

  17. The Dependence of Peat Soil Hydraulic Conductivity on Dominant Vegetation Type in Mountain Fens

    NASA Astrophysics Data System (ADS)

    Crockett, A. C.; Ronayne, M. J.; Cooper, D. J.

    2014-12-01

    The peat soil within fen wetlands provides water storage that can substantially influence the hydrology of mountain watersheds. In this study, we investigated the relationship between hydraulic conductivity and vegetation type for fens occurring in Rocky Mountain National Park (RMNP), Colorado, USA. Vegetation in RMNP fens can be dominated by woody plants and shrubs, such as willows; by mosses; or by herbaceous plants such as sedges. Fens dominated by each vegetation type were selected for study. Six fens were investigated, all of which are in the Colorado River watershed on the west side of RMNP. For each site, soil hydraulic conductivity was measured at multiple locations using a single-ring infiltrometer. As a result of the shallow water table in these fens (the water table was always within 10 cm of the surface), horizontal hydraulic gradients were produced during the field tests. The measured infiltration rates were analyzed using the numerical model HYDRUS. In order to determine the hydraulic conductivity, a parameter estimation problem was solved using HYDRUS as the forward simulator. Horizontal flow was explicitly accounted for in the model. This approach produced more accurate estimates of hydraulic conductivity than would be obtained using an analytical solution that assumes strictly vertical flow. Significant differences in hydraulic properties between fens appear to result at least in part from the effects of different dominant vegetation types on peat soil formation.

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

    NASA Technical Reports Server (NTRS)

    Eagleson, Peter S.; Jasinski, Michael F.

    1988-01-01

    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.

  19. Hydrologic modeling of soil water storage in landfill cover systems

    SciTech Connect

    Barnes, F.J.; Rodgers, J.C.

    1987-01-01

    The accuracy of modeling soil water storage by two hydrologic models, CREAMS and HELP, was tested by comparing simulation results with field measurements of soil moisture in eight experimental landfill cover systems having a range of well-defined soil profiles and vegetative covers. Regression analysis showed that CREAMS generally represented soil moisture more accurately than HELP simulations. Soil profiles that more closely resembled natural agricultural soils were more accurately modeled than highly artificial layered soil profiles. Precautions for determining parameter values for model input and for interpreting simulation results are discussed.

  20. Development of a Multi-experience Approach in Introductory Soil and Vegetation Geography Courses.

    ERIC Educational Resources Information Center

    Limbird, Arthur

    1982-01-01

    Describes an introductory college level course in soil and vegetation which uses lecture, audiovisual tutorial, individualized instruction, field trips, films, and games. The course consists of three segments: basic concepts of soils, basic concepts of plants, and soil and vegetation concepts in a spatial context. (KC)

  1. Spatio-temporal evaluation of resolution enhancement for passive microwave soil moisture and vegetation optical depth

    NASA Astrophysics Data System (ADS)

    Gevaert, A. I.; Parinussa, R. M.; Renzullo, L. J.; van Dijk, A. I. J. M.; de Jeu, R. A. M.

    2016-03-01

    Space-borne passive microwave radiometers are used to derive land surface parameters such as surface soil moisture and vegetation optical depth (VOD). However, the value of such products in regional hydrology is limited by their coarse resolution. In this study, the land parameter retrieval model (LPRM) is used to derive enhanced resolution (∼10 km) soil moisture and VOD from advanced microwave scanning radiometer (AMSR-E) brightness temperatures sharpened by a modulation technique based on high-frequency observations. A precipitation mask based on brightness temperatures was applied to remove precipitation artefacts in the sharpened LPRM products. The spatial and temporal patterns in the resulting products are evaluated against field-measured and modeled soil moisture as well as the normalized difference vegetation index (NDVI) over mainland Australia. Results show that resolution enhancement accurately sharpens the boundaries of different vegetation types, lakes and wetlands. Significant changes in temporal agreement between LPRM products and related datasets are limited to specific areas, such as lakes and coastal areas. Spatial correlations, on the other hand, increase over most of Australia. In addition, hydrological signals from irrigation and water bodies that were absent in the low-resolution soil moisture product become clearly visible after resolution enhancement. The increased information detail in the high-resolution LPRM products should benefit hydrological studies at regional scales.

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

    USGS Publications Warehouse

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

    2003-01-01

    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.

  3. Modeling Soil Freezing Dynamics

    NASA Astrophysics Data System (ADS)

    Flerchinger, G. N.; Seyfried, M. S.; Hardegree, S. P.

    2002-12-01

    Seasonally frozen soil strongly influences runoff and erosion on large areas of land around the world. In many areas, rain or snowmelt on seasonally frozen soil is the single leading cause of severe runoff and erosion events. As soils freeze, ice blocks the soil pores, greatly diminishing the permeability of the soil. This is aggravated by the tendency of water to migrate to the freezing front, causing elevated ice content and frost heave. Freezing and thawing of the soil are controlled by the complex interactions of heat and water transfer at the soil surface governed by meteorological and environmental conditions at the soil-atmosphere interface. Soil freezing dynamics including liquid water content, infiltration, and runoff simulated by the Simultaneous Heat and Water (SHAW) Model were tested at three field locations in southwest Idaho. Sites included: three soil types at the Orchard Field Test Site; bare and sagebrush-covered runoff plots at the Lower Sheep Creek site on the Reynolds Creek Experimental Watershed; and runoff plots on steep mountainous slopes on the Boise Front. Detailed simulations of soil freezing and thawing were conducted specifically to examine the dynamics of liquid water content during freezing and thawing. Freezing/thawing processes, including liquid water content and runoff, were simulated well.

  4. Climate, vegetation, and soil controls on hydraulic redistribution in shallow tree roots

    NASA Astrophysics Data System (ADS)

    Yu, Kailiang; D'Odorico, Paolo

    2014-04-01

    Hydraulic redistribution defined as the translocation of soil moisture by plant root systems in response to water potential gradients is a phenomenon widely documented in different climate, vegetation, and soil conditions. Past research has largely focused on hydraulic redistribution in deep tree roots with access to groundwater and/or winter rainfall, while the case of relatively shallow (i.e., ≈1-2 m deep) tree roots has remained poorly investigated. In fact, it is not clear how hydraulic redistribution in shallow root zones is affected by climate, vegetation, and soil properties. In this study, we developed a model to investigate the climate, vegetation, and soil controls on the net direction and magnitude of hydraulic redistribution in shallow tree root systems at the growing season to yearly timescale. We used the model to evaluate the effect of hydraulic redistribution on the water stress of trees and grasses. We found that hydraulic lift increases with decreasing rainfall frequency, depth of the rooting zone, root density in the deep soil and tree leaf area index; at the same time for a given rainfall frequency, hydraulic lift increases with increasing average rainstorm depth and soil hydraulic conductivity. We propose that water drainage into deeper soil layers can lead to the emergence of vertical water potential gradients sufficient to explain the occurrence of hydraulic lift in shallow tree roots without invoking the presence of a shallow water table or winter precipitation. We also found that hydraulic descent reduces the water stress of trees and hydraulic lift reduces the water stress of grass with important implications on tree-grass interactions.

  5. Directional infrared temperature and emissivity of vegetation: Measurements and models

    NASA Technical Reports Server (NTRS)

    Norman, J. M.; Castello, S.; Balick, L. K.

    1994-01-01

    Directional thermal radiance from vegetation depends on many factors, including the architecture of the plant canopy, thermal irradiance, emissivity of the foliage and soil, view angle, slope, and the kinetic temperature distribution within the vegetation-soil system. A one dimensional model, which includes the influence of topography, indicates that thermal emissivity of vegetation canopies may remain constant with view angle, or emissivity may increase or decrease as view angle from nadir increases. Typically, variations of emissivity with view angle are less than 0.01. As view angle increases away from nadir, directional infrared canopy temperature usually decreases but may remain nearly constant or even increase. Variations in directional temperature with view angle may be 5C or more. Model predictions of directional emissivity are compared with field measurements in corn canopies and over a bare soil using a method that requires two infrared thermometers, one sensitive to the 8 to 14 micrometer wavelength band and a second to the 14 to 22 micrometer band. After correction for CO2 absorption by the atmosphere, a directional canopy emissivity can be obtained as a function of view angle in the 8 to 14 micrometer band to an accuracy of about 0.005. Modeled and measured canopy emissivities for corn varied slightly with view angle (0.990 at nadir and 0.982 at 75 deg view zenith angle) and did not appear to vary significantly with view angle for the bare soil. Canopy emissivity is generally nearer to unity than leaf emissivity may vary by 0.02 with wavelength even though leaf emissivity. High spectral resolution, canopy thermal emissivity may vary by 0.02 with wavelength even though leaf emissivity may vary by 0.07. The one dimensional model provides reasonably accurate predictions of infrared temperature and can be used to study the dependence of infrared temperature on various plant, soil, and environmental factors.

  6. Soil water and vegetation management for cleanup of selenium contaminated soils

    SciTech Connect

    Not Available

    1989-05-01

    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.

  7. Vegetation modeling in Yakutia, northeastern Siberia: connecting to palaeovegetation simulation and model-data comparison

    NASA Astrophysics Data System (ADS)

    Ni, J.; Herzschuh, U.

    2009-04-01

    Vegetation model is a useful tool to understand the impacts of climate change on ecosystems in the present, past and future. Simulation of the palaeovegetation can link the geographical pattern of vegetation in the past to pollen proxy and then test the palaeoclimate modeling. In this study we used an equilibrium vegetation model (BIOME4) and a dynamic vegetation model (LPJ) to predict the present-day vegetation pattern and their dynamic changes from 1901-2002 in Yakutia, an Arctic and sub-Arctic region in eastern Siberia, where is sensitive to climate change. Both the models characterized the basic features of regional vegetation pattern, function and their changes through time. The BIOME4 simulated a reasonable pattern of present biome distribution compared to the regional vegetation maps, the deciduous taiga-montane forests in the southern and central Yakutia, evergreen taiga-montane forests in the southwestern mountainous region and in the eastern coast, shrub tundra and dwarf shrub tundra in the northwest and northeast mixed with temperate xerophytic shrubland. In the NW Yakutia the LPJ demonstrated a dynamic change of local vegetation during the past 102 years responding to the changed climates. Forest and shrub covered the large area from the beginning to the 1950s of the 20th Century. Tundra extended from the west to the east during 1960s to 1970s. The woody plants extended in 1980s and in late 1990s to early 21st Century and grasses extended in 1990s. The performance of global vegetation models in regional study is well, but problems still existed. More plant functional types especially the shrubs and grasses and climatic constraints to them should be taken into account when improving the models. Soil water-related parameters should be redefined. The modules of permafrost, snow, and fire should be added or modified. Regional input data of climates, vegetation and soils at finer resolutions will be obtained from the regional and local studies.

  8. Microwave remote sensing of soil moisture content over bare and vegetated fields

    NASA Technical Reports Server (NTRS)

    Wang, J. R.; Shiue, J. C.; Mcmurtrey, J. E., III

    1980-01-01

    Remote measurements of soil moisture contents over bare fields and fields covered with orchard grass, corn, and soybean were made during October 1979 with 1.4 GHz and 5 GHz microwave radiometers mounted on a truck. Ground truth of soil moisture content, ambient air, and soil temperatures was acquired concurrently with the radiometric measurements. The biomass of the vegetation was sampled about once a week. The measured brightness temperatures over bare fields were compared with those of radiative transfer model calculations using as inputs the acquired soil moisture and temperature data with appropriate values of dielectric constants for soil-water mixtures. Good agreement was found between the calculated and the measured results over 10-70 deg incident angles. The presence of vegetation was found to reduce the sensitivity of soil moisture sensing. At 1.4 GHz the sensitivity reduction ranged from approximately 20% for 10-cm tall grassland to over 60% for the dense soybean field. At 5 GHz the corresponding reduction in sensitivity ranged from approximately 70 to approximately 90%.

  9. Microwave remote sensing of soil moisture content over bare and vegetated fields

    NASA Technical Reports Server (NTRS)

    Wang, J. R.; Shiue, J. C.; Mcmurtrey, J. E., III (Principal Investigator)

    1980-01-01

    The author has identified the following significant results. Ground truth of soil moisture content, and ambient air and soil temperatures were acquired concurrently with measurements of soil moisture in bare fields and fields covered with grass, corn, and soybeans obtained with 1.4 GHz and 5 GHz radiometers mounted on a truck. The biomass of the vegetation was sampled about once a week. The measured brightness temperatures over the bare fields were compared with those of radiative transfer model calculations using as inputs the acquired soil moisture and temperatures data with appropriate values of dielectric constants for soil-water mixtures. A good agreement was found between the calculated and measured results over 10 deg to 70 deg incident angles. The presence of vegetation reduced the sensitivity of soil moisture sensing. At 1.4 GHz the sensitivity reduction ranged from about 20% for 10 cm tall grassland cover to over 50 to 60% for the dense soybean field. At 5 GHz corresponding reduction in sensitivity ranged from approximately 70% to approximately 90%.

  10. Microwave remote sensing of soil moisture content over bare and vegetated fields

    NASA Astrophysics Data System (ADS)

    Wang, J. R.; Shiue, J. C.; McMurtrey, J. E., III

    1980-10-01

    Remote measurements of soil moisture contents over bare fields and fields covered with orchard grass, corn, and soybean were made during October 1979 with 1.4 GHz and 5 GHz microwave radiometers mounted on a truck. Ground truth of soil moisture content, ambient air and soil temperatures was acquired concurrently with the radiometric measurements. The biomass of the vegetation was sampled about once a week. The measured brightness temperatures over bare fields were compared with those of radiative transfer model calculations using as inputs the acquired soil moisture and temperature data with appropriate values of dielectric constants for soil-water mixtures. Good agreement was found between the calculated and the measured results over 10°-70° incident angles. The presence of vegetation was found to reduce the sensitivity of soil moisture sensing. At 1.4 GHz the sensitivity reduction ranged from ˜20% for 10-cm tall grassland to over 60% for the dense soybean field. At 5 GHz the corresponding reduction in sensitivity ranged from ˜70% to ˜90%.

  11. Microwave model prediction and verifications for vegetated terrain

    NASA Technical Reports Server (NTRS)

    Fung, A. K.

    1985-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

    Moreno, Jose; Moran, Susan

    2014-05-01

    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

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

    NASA Astrophysics Data System (ADS)

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

    2006-08-01

    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 (θ), 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 θ 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 θ deficits, and the switch from grass to bare soil following the rainy season had a significant impact on ET.

  14. Productivity of wet soils: Biomass of cultivated and natural vegetation

    SciTech Connect

    Johnston, C.A.

    1988-12-01

    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.

  15. Soil erosion and sediment yield and their relationships with vegetation cover in upper stream of the Yellow River.

    PubMed

    Ouyang, Wei; Hao, Fanghua; Skidmore, Andrew K; Toxopeus, A G

    2010-12-15

    Soil erosion is a significant concern when considering regional environmental protection, especially in the Yellow River Basin in China. This study evaluated the temporal-spatial interaction of land cover status with soil erosion characteristics in the Longliu Catchment of China, using the Soil and Water Assessment Tool (SWAT) model. SWAT is a physical hydrological model which uses the RUSLE equation as a sediment algorithm. Considering the spatial and temporal scale of the relationship between soil erosion and sediment yield, simulations were undertaken at monthly and annual temporal scales and basin and sub-basin spatial scales. The corresponding temporal and spatial Normalized Difference Vegetation Index (NDVI) information was summarized from MODIS data, which can integrate regional land cover and climatic features. The SWAT simulation revealed that the annual soil erosion and sediment yield showed similar spatial distribution patterns, but the monthly variation fluctuated significantly. The monthly basin soil erosion varied from almost no erosion load to 3.92 t/ha and the maximum monthly sediment yield was 47,540 tones. The inter-annual simulation focused on the spatial difference and relationship with the corresponding vegetation NDVI value for every sub-basin. It is concluded that, for this continental monsoon climate basin, the higher NDVI vegetation zones prevented sediment transport, but at the same time they also contributed considerable soil erosion. The monthly basin soil erosion and sediment yield both correlated with NDVI, and the determination coefficients of their exponential correlation model were 0.446 and 0.426, respectively. The relationships between soil erosion and sediment yield with vegetation NDVI indicated that the vegetation status has a significant impact on sediment formation and transport. The findings can be used to develop soil erosion conservation programs for the study area.

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    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.

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

    USGS Publications Warehouse

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

    2012-01-01

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

  18. Vegetation and soils field research data base: Experiment summaries

    NASA Technical Reports Server (NTRS)

    Biehl, L. L.; Daughtry, C. S. T.; Bauer, M. E.

    1984-01-01

    Understanding of the relationships between the optical, spectral characteristics and important biological-physical parameters of earth-surface features can best be obtained by carefully controlled studies over fields and plots where complete data describing the condition of targets are attainable and where frequent, timely spectral measurement can be obtained. Development of a vegetation and soils field research data base was initiated in 1972 at Purdue University's Laboratory for Applications of Remote Sensing and expanded in the fall of 1974 by NASA as part of LACIE. Since then, over 250,000 truck-mounted and helicopter-borne spectrometer/multiband radiometer observations have been obtained of more than 50 soil series and 20 species of crops, grasses, and trees. These data are supplemented by an extensive set of biophysical and meteorological data acquired during each mission. The field research data form one of the most complete and best-documented data sets acquired for agricultural remote sensing research. Thus, they are well-suited to serve as a data base for research to: (1) quantiatively determine the relationships of spectral and biophysical characteristics of vegetation, (2) define future sensor systems, and (3) develop advanced data analysis techniques.

  19. Interactions between soil moisture and Atmospheric Boundary Layer at the Brazilian savana-type vegetation Cerrado

    NASA Astrophysics Data System (ADS)

    Pinheiro, L. R.; Siqueira, M. B.

    2013-05-01

    Before the large people influx and development of the central part of Brazil in the sixties, due to new capital Brasília, Cerrado, a typical Brazilian savanna-type vegetation, used to occupy about 2 million km2, going all the way from the Amazon tropical forest, in the north of the country, to the edges of what used to be of the Atlantic forest in the southeast. Today, somewhat 50% of this area has given place to agriculture, pasture and managed forests. It is forecasted that, at the current rate of this vegetation displacement, Cerrado will be gone by 2030. Understanding how Cerrado interacts with the atmosphere and how this interaction will be modified with this land-use change is a crucial step towards improving predictions of future climate-change scenarios. Cerrado is a vegetation adapted to a climate characterized by two very distinct seasons, a wet season (Nov-Mar) and dry season (May-Ago), with April and October being transitions between seasons. Typically, based on measurements in a weather station located in Brasilia, 75% of precipitation happens in the wet-season months and only 5% during dry-season. Under these circumstances, it is clear that the vegetation will have to cope with long periods of water stress. In this work we studied using numerical simulations, the interactions between soil-moisture, responsible for the water stress, with the Atmospheric Boundary Layer (ABL). The numerical model comprises of a Soil-Vegetation-Atmosphere model where the biophysical processes are represented with a big-leaf approach. Soil water is estimated with a simple logistic model and with water-stress effects on stomatal conductance are parameterized from local measurements of simultaneous latent-heat fluxes and soil moisture. ABL evolution is calculate with a slab model that considers independently surface and entrainment fluxes of sensible- and latent- heat. Temperature tropospheric lapse-rate is taken from soundings at local airport. Simulations of 30-day dry

  20. PALADYN, a comprehensive land surface-vegetation-carbon cycle model of intermediate complexity

    NASA Astrophysics Data System (ADS)

    Willeit, Matteo; Ganopolski, Andrey

    2016-04-01

    PALADYN is presented, a new comprehensive and computationally efficient land surface-vegetation-carbon cycle model designed to be used in Earth system models of intermediate complexity for long-term simulations and paleoclimate studies. The model treats in a consistent manner the interaction between atmosphere, terrestrial vegetation and soil through the fluxes of energy, water and carbon. Energy, water and carbon are conserved. The model explicitly treats permafrost, both in physical processes and as important carbon pool. The model distinguishes 9 surface types of which 5 are different vegetation types, bare soil, land ice, lake and ocean shelf. Including the ocean shelf allows to treat continuous changes in sea level and shelf area associated with glacial cycles. Over each surface type the model solves the surface energy balance and computes the fluxes of sensible, latent and ground heat and upward shortwave and longwave radiation. It includes a single snow layer. The soil model distinguishes between three different macro surface types which have their own soil column: vegetation and bare soil, ice sheet and ocean shelf. The soil is vertically discretized into 5 layers where prognostic equations for temperature, water and carbon are consistently solved. Phase changes of water in the soil are explicitly considered. A surface hydrology module computes precipitation interception by vegetation, surface runoff and soil infiltration. The soil water equation is based on Darcy's law. Given soil water content, the wetland fraction is computed based on a topographic index. Photosynthesis is computed using a light use efficiency model. Carbon assimilation by vegetation is coupled to the transpiration of water through stomatal conductance. The model includes a dynamic vegetation module with 5 plant functional types competing for the gridcell share with their respective net primary productivity. Each macro surface type has its own carbon pools represented by a litter, a fast

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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

  2. A Methodology for Surface Soil Moisture and Vegetation Optical Depth Retrieval Using the Microwave Polarization Difference Index

    NASA Technical Reports Server (NTRS)

    Owe, Manfred; deJeu, Richard; Walker, Jeffrey; Zukor, Dorothy J. (Technical Monitor)

    2001-01-01

    A methodology for retrieving surface soil moisture and vegetation optical depth from satellite microwave radiometer data is presented. The procedure is tested with historical 6.6 GHz brightness temperature observations from the Scanning Multichannel Microwave Radiometer over several test sites in Illinois. Results using only nighttime data are presented at this time, due to the greater stability of nighttime surface temperature estimation. The methodology uses a radiative transfer model to solve for surface soil moisture and vegetation optical depth simultaneously using a non-linear iterative optimization procedure. It assumes known constant values for the scattering albedo and roughness. Surface temperature is derived by a procedure using high frequency vertically polarized brightness temperatures. The methodology does not require any field observations of soil moisture or canopy biophysical properties for calibration purposes and is totally independent of wavelength. Results compare well with field observations of soil moisture and satellite-derived vegetation index data from optical sensors.

  3. Projection of future climate change impacts on nonpoint source pollution loads for a forest dominant dam watershed by reflecting future vegetation canopy in a Soil and Water Assessment Tool model.

    PubMed

    Park, Min J; Park, Jong Y; Shin, Hyung J; Lee, Mi S; Park, Geun A; Jung, In K; Kim, Seong J

    2010-01-01

    This study is to assess the future impact of climate change on hydrological behavior considering future vegetation canopy prediction and its propagation to nonpoint source pollution (NPS) loads. The SWAT (Soil and Water Assessment Tool) model was used for the assessment. For a forest dominant ChungjuDam watershed of South Korea, the MIROC3.2hires climate data of SRES A1B and B1 scenarios were adopted and downscaled for the watershed. The future vegetation canopy information was projected by the monthly relationship between Terra MODIS (MODerate resolution Imaging Spectroradiometer) LAI (Leaf Area Index) and temperature. The future predicted LAI increased up to 1.9 in 2080s April and October because of the temperature increase 3.6 degrees C and 5.3 degrees C respectively. By reflecting the future LAI changes, the future estimated percent changes of maximum annual dam inflow, SS, T-N, and T-P were + 42.5% in 2080s A1B,-35.6% in 2020s A1B,+73.7% in 2080s A1B and-21.0% in 2080s B1 scenario respectively. The increase of T-N load was from the increase of subsurface lateral flows and the groundwater recharges by the future rainfall increase. The decrease of T-P load was by decrease of sediment load during wet days because the effect of LAI increase is greater than the increase of rainfall.

  4. A new offline dust cycle model that includes dynamic vegetation

    NASA Astrophysics Data System (ADS)

    Shannon, Sarah; Lunt, Daniel

    2010-05-01

    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

  5. Separating vegetation and soil temperature using airborne multiangular remote sensing image data

    NASA Astrophysics Data System (ADS)

    Liu, Qiang; Yan, Chunyan; Xiao, Qing; Yan, Guangjian; Fang, Li

    2012-07-01

    Land surface temperature (LST) is a key parameter in land process research. Many research efforts have been devoted to increase the accuracy of LST retrieval from remote sensing. However, because natural land surface is non-isothermal, component temperature is also required in applications such as evapo-transpiration (ET) modeling. This paper proposes a new algorithm to separately retrieve vegetation temperature and soil background temperature from multiangular thermal infrared (TIR) remote sensing data. The algorithm is based on the localized correlation between the visible/near-infrared (VNIR) bands and the TIR band. This method was tested on the airborne image data acquired during the Watershed Allied Telemetry Experimental Research (WATER) campaign. Preliminary validation indicates that the remote sensing-retrieved results can reflect the spatial and temporal trend of component temperatures. The accuracy is within three degrees while the difference between vegetation and soil temperature can be as large as twenty degrees.

  6. Evaluating models of climate and forest vegetation

    NASA Technical Reports Server (NTRS)

    Clark, James S.

    1992-01-01

    Understanding how the biosphere may respond to increasing trace gas concentrations in the atmosphere requires models that contain vegetation responses to regional climate. Most of the processes ecologists study in forests, including trophic interactions, nutrient cycling, and disturbance regimes, and vital components of the world economy, such as forest products and agriculture, will be influenced in potentially unexpected ways by changing climate. These vegetation changes affect climate in the following ways: changing C, N, and S pools; trace gases; albedo; and water balance. The complexity of the indirect interactions among variables that depend on climate, together with the range of different space/time scales that best describe these processes, make the problems of modeling and prediction enormously difficult. These problems of predicting vegetation response to climate warming and potential ways of testing model predictions are the subjects of this chapter.

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

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

    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.

  8. The effects of basin morphology on soil water content and vegetation stress

    NASA Astrophysics Data System (ADS)

    Pizzolla, T.; Acampora, A.; Manfreda, S.; Fiorentino, M.

    2012-04-01

    Soil water content plays an important role especially in water limited ecosystems. It controls the partition of net radiation into sensible and latent heat, the movement of solutes and pollutants, the soil temperature and affects the water stress of vegetation. All these processes are intimately interconnected and strongly influenced by the radiation balance. The available solar radiation, that depends on climatic conditions and morphology, may strongly modify hydrological processes at the local scale. Basin morphology in fact modifies the amount of direct solar radiation, and also the amount of diffuse and reflected solar radiation received by a given point in the basin. Using the analytical model developed by Allen et al. (2006), it is possible to describe the radiation balance taking in to consideration the effects of basin morphology. This approach is extremely useful to describe the spatial distribution of solar radiation and the maps of potential evapotranspiration during any phase of the year. Using this approach in cascade with the analytical form of the soil water balance equation proposed by Laio et al. (2001), we identified the main statistics of soil moisture dynamics as well as the dynamic water stress of the vegetation (Porporato et al., 2001) during the growing season. The model has been applied using three study cases: 1) a flat river basin under stationary climate; 2) a river basin with morphology under stationary climate; 3) a river basin with morphology under stationary climate with imposed initial conditions. It is necessary to specify that the initial conditions for the last study case were defined based on the climatic conditions during the dormant period, while the vegetation water stress refers to the growing season. Results show that basin morphology (case 2 and 3) significantly affects the spatial distribution of vegetation water stress increasing its variability. The variability of this index increases when taking into consideration the

  9. [Physicochemical and biological characteristics of coastal saline soil under different vegetation cover].

    PubMed

    Zhou, Jian; Li, Gang; Zhou, Jian; Qin, Pei

    2011-04-01

    Taking seven plots of coastal saline soil under different vegetation cover in North Jiangsu as study sites, this paper studied the seasonal fluctuations of soil basic physicochemical and biological characteristics, and analyzed the relationships between these fluctuations and vegetation cover. In the test plots, there was a greater variability of soil basic physicochemical and biological characteristics. The average soil electrical conductivity was lower in crop plots (0.95 dS m(-1)) than in natural vegetation plots (2.77 dS m(-1)), but parts of the crop plots showed an increased soil electrical conductivity compared with pre-planting. Overall, the soil fertility of the plots was generally at a low level, with the hydrolysable nitrogen content averagely lower than 50 mg kg(-1), available phosphorus content (except fertilized plots) lower than 3 mg kg(-1), and organic matter content less than 1%. Due to fertilization, the soil conditions in crop plots somewhat improved. For the test coastal saline soil, its electrical conductivity and nutrient level were the key factors affecting the vegetation distribution and plant growth, and soil electrical conductivity was most important. There existed close correlations between soil nitrogen and phosphorus contents and soil microbial amount. The seasonal fluctuations of soil characteristics were closely related with vegetation type and human disturbance, being relatively stable under higher vegetation coverage and lesser human disturbance, and dramatic in bare land and castor experimental plots.

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

    SciTech Connect

    Burley, J.B.; Polakowski, K.J.; Fowler, G.

    1996-12-31

    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.

  11. Vegetation controls on soil water dynamics and runoff production in a headwater catchment in the Ore Mountains

    NASA Astrophysics Data System (ADS)

    Zehe, E.; Graeff, T.; Schlaeger, S.; Morgner, M.; Bauer, A.

    2009-04-01

    Spatial variability of soil hydraulic parameters and soil structures dominate surface runoff production as well as soil water dynamics at the hillslope and headwater scale. These seem to be common grounds in soil physics and was our credo when we instrumented a small headwater (10 km2) of the Weiáeritz with six rain gauges, a meteorological station, shallow piezometers and two STDR clusters to investigate soil moisture control on runoff and surface runoff production. Both TDR clusters consist of 35 individual TDR sensors of 60 cm depth covering an extend of 15m by 15m. Cluster 1 one is located at a grassland site, cluster 2 is located in a nearby forested area. The soil at the grassland site is a clayey loam with a high content of organic matter, a very large porosity of 0.63 in the top 20 cm and a soil hydraulic conductivity of on average around 4 * 10-5 m/s. Soil at the forested site is similar with an even higher infiltrability and higher organic content of the top soil. Both soils exhibit a high gravel content and rather high spatial variability of soil properties. Despite of this large heterogeneity of soil parameters, we found that vegetation exerts crucial control on average soil moisture dynamics, its spatial variability and most interesting on the development of the spatial covariance structure of the soil moisture patterns. Correlation length at the grassland site was rather short but increased with increasing average wetness. So did the nugget to sill ratio of the variogram. At the forested site correlation length did not vary with average wetness and was constantly 50% of the maximum probe distance. We therefore conclude that the correlation structure at the forested site is dominated by the pattern of through-fall and interception and therefore vegetation. During a modelling exercise we found that despite of the large heterogeneity of the soils a homogeneous soil setup allowed a good reproduction of observed soil moisture dynamics at the hourly scale

  12. Winter soil respiration from different vegetation patches in the Yellow River Delta, China.

    PubMed

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

    2012-07-01

    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 μmol CO(2) 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. PMID:22576142

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

    NASA Astrophysics Data System (ADS)

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

    2012-07-01

    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 μmol 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.

  14. Effects of spatial variations of soil moisture and vegetation on the evolution of a prestorm environment - A numerical case study

    NASA Technical Reports Server (NTRS)

    Chang, Jy-Tai; Wetzel, Peter J.

    1991-01-01

    To examine the effects of spatial variations of soil moisture and vegetation coverage on the evolution of a prestorm environment, the Goddard mesoscale model is modified to incorporate a simple evapotranspiration model that requires these two parameters. The case study of 3-4 June 1980 is of special interest due to the development of a tornado producing convective complex near Grand Island, Nebraska during a period of comparatively weak synoptic-scale forcing. It is shown that the observed stationary front was strongly enhanced by differential heating created by observed gradients of soil moisture, as acted upon by the vegetation cover.

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

    PubMed

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

    2013-09-01

    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.

  16. Concentrations of lead, cadmium and barium in urban garden-grown vegetables: the impact of soil variables

    PubMed Central

    McBride, Murray B.; Shayler, Hannah A.; Spliethoff, Henry M.; Mitchell, Rebecca G.; Marquez-Bravo, Lydia G.; Ferenz, Gretchen S.; Russell-Anelli, Jonathan M.; Casey, Linda; Bachman, Sharon

    2014-01-01

    Paired vegetable/soil samples from New York City and Buffalo, NY, gardens were analyzed for lead (Pb), cadmium (Cd) and barium (Ba). Vegetable aluminum (Al) was measured to assess soil adherence. Soil and vegetable metal concentrations did not correlate; vegetable concentrations varied by crop type. Pb was below health-based guidance values (EU standards) in virtually all fruits. 47% of root crops and 9% of leafy greens exceeded guidance values; over half the vegetables exceeded the 95th percentile of market-basket concentrations for Pb. Vegetable Pb correlated with Al; soil particle adherence/incorporation was more important than Pb uptake via roots. Cd was similar to market-basket concentrations and below guidance values in nearly all samples. Vegetable Ba was much higher than Pb or Cd, although soil Ba was lower than soil Pb. The poor relationship between vegetable and soil metal concentrations is attributable to particulate contamination of vegetables and soil characteristics that influence phytoavailability. PMID:25163429

  17. Concentrations of lead, cadmium and barium in urban garden-grown vegetables: the impact of soil variables.

    PubMed

    McBride, Murray B; Shayler, Hannah A; Spliethoff, Henry M; Mitchell, Rebecca G; Marquez-Bravo, Lydia G; Ferenz, Gretchen S; Russell-Anelli, Jonathan M; Casey, Linda; Bachman, Sharon

    2014-11-01

    Paired vegetable/soil samples from New York City and Buffalo, NY, gardens were analyzed for lead (Pb), cadmium (Cd) and barium (Ba). Vegetable aluminum (Al) was measured to assess soil adherence. Soil and vegetable metal concentrations did not correlate; vegetable concentrations varied by crop type. Pb was below health-based guidance values (EU standards) in virtually all fruits. 47% of root crops and 9% of leafy greens exceeded guidance values; over half the vegetables exceeded the 95th percentile of market-basket concentrations for Pb. Vegetable Pb correlated with Al; soil particle adherence/incorporation was more important than Pb uptake via roots. Cd was similar to market-basket concentrations and below guidance values in nearly all samples. Vegetable Ba was much higher than Pb or Cd, although soil Ba was lower than soil Pb. The poor relationship between vegetable and soil metal concentrations is attributable to particulate contamination of vegetables and soil characteristics that influence phytoavailability.

  18. Vegetative cover and PAHs accumulation in soils of urban green space.

    PubMed

    Peng, Chi; Ouyang, Zhiyun; Wang, Meie; Chen, Weiping; Jiao, Wentao

    2012-02-01

    We investigated how urban land uses influence soil accumulation of polycyclic aromatic hydrocarbons (PAHs) in the urban green spaces composed of different vegetative cover. How did soil properties, urbanization history, and population density affect the outcomes were also considered. Soils examined were obtained at 97 green spaces inside the Beijing metropolis. PAH contents of the soils were influenced most significantly by their proximity to point source of industries such as the coal combustion installations. Beyond the influence circle of industrial emissions, land use classifications had no significant effect on the extent of PAH accumulation in soils. Instead, the nature of vegetative covers affected PAH contents of the soils. Tree-shrub-herb and woodland settings trapped more airborne PAH and soils under these vegetative patterns accumulated more PAHs than those of the grassland. Urbanization history, population density and soil properties had no apparent impact on PAHs accumulations in soils of urban green space.

  19. Modeling Hydrologic and Vegetation Responses in Freshwater Wetlands

    NASA Astrophysics Data System (ADS)

    Chui, Ting Fong May; Low, Swee Yang; Liong, Shie-Yui

    2010-05-01

    Wetlands constitute 6 - 7 % of the Earth's land surface and provide various critical ecosystem services such as purifying the air and water, mitigating floods and droughts, and supporting wildlife habitats. Despite the importance of wetlands, they are under threat of degradation by human-induced land use changes and climate change. Even if the value of wetlands is recognized, they are often not managed properly or restored successfully due to an inadequate understanding of the ecosystems and their responses to management scenarios. A better understanding of the main components of wetlands, namely the interdependent hydrologic and vegetation systems, and the sensitivity of their responses to engineering works and climate change, is crucial for the preservation of wetlands. To assess these potential impacts, a model is developed in this study for characterizing the coupled dynamics between soil moisture and plant biomass in wetland habitats. The hydrology component of the model is based on the Richards' equation and simulates spatially-varying groundwater movement and provides information on soil moisture at different depths. The plant growth component of the model is described through an equation of the Lotka-Volterra type modified for plant growth dynamics and is adapted from published literature. The two components are coupled via transpiration and ecosystem carrying capacity for plants. Transpiration is modeled for both unsaturated and saturated zones, while the carrying capacity describes limiting oxygen and subsequent nutrient availability in the soil column as a function of water table depth. Vegetation is represented by two species characteristic of mudflat herbaceous plants ranging from facultative wetland to upland plants. The model is first evaluated using a simplified domain and the hydrological information available in the RG2 site of the Everglades wetlands region. The modeled water table fluctuations in general are comparable to field data collected on

  20. Heavy metals bioconcentration from soil to vegetables and assessment of health risk caused by their ingestion.

    PubMed

    Garg, V K; Yadav, Poonam; Mor, Suman; Singh, Balvinder; Pulhani, Vandana

    2014-03-01

    The present study was undertaken to assess the non-carcinogenic human health risk of heavy metals through the ingestion of locally grown and commonly used vegetables viz. Raphanus sativus (root vegetable), Daucus carota (root vegetable), Benincasa hispida (fruit vegetable) and Brassica campestris leaves (leafy vegetable) in a semi-urbanized area of Haryana state, India. Heavy metal quantification of soil and vegetable samples was done using flame atomic absorption spectrophotometer. Lead, cadmium and nickel concentration in vegetable samples varied in range of 0.12-6.54 mg kg(-1), 0.02-0.67 mg kg(-1) and <0.05-0.41 mg kg(-1), respectively. Cadmium and lead concentration in some vegetable samples exceeded maximum permissible limit given by World Health Organization/Food and Agriculture Organization and Indian standards. Much higher concentrations of Pb (40-190.5 mg kg(-1)), Cd (0.56-9.85 mg kg(-1)) and Ni (3.21-45.87 mg kg(-1)) were reported in corresponding vegetable fields' soils. Correlation analysis revealed the formation of three primary clusters, i.e. Cu-Cd, Cd-Pb and Ni-Zn in vegetable fields' soils further supported by cluster analysis and principal component analysis. Bioconcentration factor revealed that heavy metals' uptake was more by leafy vegetable than root and fruit vegetables. Hazard index of all the vegetables was less than unity; thus, the ingestion of these vegetables is unlikely to pose health risks to the target population.

  1. Combined active and passive microwave remote sensing of soil moisture for vegetated surfaces at L-band

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The distorted Born approximation (DBA) combined with the numerical solutions of Maxwell equations (NMM3D) has been used for the radar backscattering model for the SMAP mission. The models for vegetated surfaces such as wheat, grass, soybean and corn have been validated with the Soil Moisture Active ...

  2. Thermal vegetation canopy model studies

    SciTech Connect

    Smith, J.A.; Ranson, K.J.; Nguyen, D.; Balick, L.; Link, L.E.; Fritschen, L.; Hutchison, B.

    1981-01-01

    An iterative-type thermal model applicable to forest canopies was tested with data from two diverse forest types. The model framework consists of a system of steady-state energy budget equations describing the interactions of short- and long-wave radiation within three horizontally infinite canopy layers. A state-space formulation of the energy dynamics within the canopy is used which permits a factorization of canopy geometrical parameters from canopy optical and thermal coefficients as well as environmental driving variables. Two sets of data characterizing a coniferous (Douglas-fir) and deciduous (oak-hickory) canopy were collected to evaluate the thermal model. The results show that the model approximates measured mean canopy temperatures to within 2/sup 0/C for relatively clear weather conditions and deviates by a maximum of 3/sup 0/C for very hazy or foggy conditions.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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

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

    NASA Technical Reports Server (NTRS)

    Eagleson, Peter S.; Jasinski, Michael F.

    1988-01-01

    This work focuses on the characterization of natural, spatially variable, semivegetated landscapes using a linear, stochastic, canopy-soil reflectance model. A first application of the model was the investigation of the effects of subpixel and regional variability of scenes on the shape and structure of red-infrared scattergrams. Additionally, the model was used to investigate the inverse problem, the estimation of subpixel vegetation cover, given only the scattergrams of simulated satellite scale multispectral scenes. The major aspects of that work, including recent field investigations, are summarized.

  5. Feasibility of using LANDSAT images of vegetation cover to estimate effective hydraulic properties of soils

    NASA Technical Reports Server (NTRS)

    Eagleson, P. S.

    1985-01-01

    Research activities conducted from February 1, 1985 to July 31, 1985 and preliminary conclusions regarding research objectives are summarized. The objective is to determine the feasibility of using LANDSAT data to estimate effective hydraulic properties of soils. The general approach is to apply the climatic-climax hypothesis (Ealgeson, 1982) to natural water-limited vegetation systems using canopy cover estimated from LANDSAT data. Natural water-limited systems typically consist of inhomogeneous vegetation canopies interspersed with bare soils. The ground resolution associated with one pixel from LANDSAT MSS (or TM) data is generally greater than the scale of the plant canopy or canopy clusters. Thus a method for resolving percent canopy cover at a subpixel level must be established before the Eagleson hypothesis can be tested. Two formulations are proposed which extend existing methods of analyzing mixed pixels to naturally vegetated landscapes. The first method involves use of the normalized vegetation index. The second approach is a physical model based on radiative transfer principles. Both methods are to be analyzed for their feasibility on selected sites.

  6. Influence of planting patterns on fluoroquinolone residues in the soil of an intensive vegetable cultivation area in northern China.

    PubMed

    Li, Xuewen; Xie, Yunfeng; Wang, Jinfeng; Christakos, George; Si, Jiliang; Zhao, Huinan; Ding, Yanqiang; Li, Jie

    2013-08-01

    Recent studies have demonstrated the persistence of antibiotics in soil, especially in areas of vegetable cultivation. However, there are very few studies of the influence of planting regimes on the levels of antibiotic pollution. This work introduces geographical-detector models to investigate the relationship between planting patterns (vegetable planting model, manure type and quantity, planting age, greenhouse area, and topographic elevation) and residual fluoroquinolones (FQs) in soil in a pilot project in Shouguang County, Shandong Province (the largest vegetable-producing area in China). The results led to the following findings. 1. The vegetable planting model is the major determinant of the spatial stratification of FQ in the soil. For example, the "cucumber-cucumber" model (growing cucumbers after cucumbers) has a three-fold power of determinant compared to the "pepper-melon" model (growing melons after peppers). 2. Planting age (years with continuous vegetable cultivation) does not necessarily affect the spatial distribution of FQ owing to their relatively short degradation period. 3. Interactions between risk factors were more significant than the individual factors for FQ pollution. In particular, the interaction between the vegetable planting model and amount of manure resulted in the highest pollution level. The findings of the present study make it possible to introduce effective and practical measures to alleviate pollution of soils by FQ in the study area. Adjustment of the vegetable cultivation models and application of chicken manure (less than 6 kg/m(2) manure annually with a more dry than fresh manure) could be an effective and flexible approach to alleviate FQ pollution.

  7. A new thermal vegetation canopy model

    SciTech Connect

    Li Zhengzhi; Dong Gouquan )

    1992-10-01

    A three-layer thermal vegetation canopy model applicable to forest canopies was developed and tested by field experiments. The model is based on energy budget equations that describe the interactions between short and long wave radiation, sensible heat flux and latent heat flux within three horizontally infinite canopy layers. Particularly it concerns the wind, air temperature, and water vapor pressure profiles in the canopy, which were never considered in earlier models. In solving the nonlinear energy budget equations, a new method was adopted resulting in great reduction of the model computer time. The calculated results of the model are in good agreement with observed data, which shows that the new model is able to simulate exactly the variation of canopy temperature with vegetation structure and environmental conditions. 11 refs.

  8. Modeling soil response to acidic deposition in nonsulfate adsorbing soils

    SciTech Connect

    Bloom, P.R.; Grigal, D.F.

    1985-01-01

    A simple semiempirical model for the prediction of changes in soil pH and base saturation with acidic deposition was developed. In steady-state ecosystems acidic deposition results in losses of basic cations from exchange sites. In the model, depletion of exchangeable bases is calculated from the difference between input acidity and output of H/sup +/ and Al/sup 3 +/ in water percolating through the solum. A correction for the decrease in bicarbonate weathering is made but sulfate adsorption is not considered. Estimates including the effect of increased mineral weathering with decreased pH can be made if the natural weathering rate is known and if the order with respect to H/sup +/ is known for the rate expression for soil weathering. The model predicted laboratory data for the acidification of samples for three soil horizons. For a fourth horizon, that was formed in contact with bedrock and high in weatherable minerals, the model overestimated the effect of the acid. Model predictions using soil data showed a slow decrease in soil pH and base saturation until the pH region of Al buffering was attained and then a new steady-state was achieved. The pH and base saturation in the Al buffering region was similar to that found in very acid soils under forest vegetation.

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

    NASA Technical Reports Server (NTRS)

    Wiegand, C. L. (Principal Investigator)

    1973-01-01

    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.

  10. Soil, water, and vegetation conditions in south Texas

    NASA Technical Reports Server (NTRS)

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

    1976-01-01

    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.

  11. An update on remote measurement of soil moisture over vegetation using infrared temperature measurements: A FIFE perspective

    NASA Technical Reports Server (NTRS)

    Carlson, Toby N.

    1988-01-01

    Using model development, image analysis and micrometeorological measurements, the object is to push beyond the present limitations of using the infrared temperature method for remotely determining surface energy fluxes and soil moisture over vegetation. Model development consists of three aspects: (1) a more complex vegetation formulation which is more flexible and realistic; (2) a method for modeling the fluxes over patchy vegetation cover; and (3) a method for inferring a two-layer soil vertical moisture gradient from analyses of horizontal variations in surface temperatures. HAPEX and FIFE satellite data will be used along with aircraft thermal infrared and solar images as input for the models. To test the models, moisture availability and bulk canopy resistances will be calculated from data collected locally at the Rock Springs experimental field site and, eventually, from the FIFE project.

  12. Submersed Aquatic Vegetation Modeling Output Online

    USGS Publications Warehouse

    Yin, Yao; Rogala, Jim; Sullivan, John; Rohweder, Jason J.

    2005-01-01

    Introduction The ability to predict the distribution of submersed aquatic vegetation in the Upper Mississippi River on the basis of physical or chemical variables is useful to resource managers. Wildlife managers have a keen interest in advanced estimates of food quantity such as American wildcelery (Vallisneria americana) population status to give out more informed advisories to hunters before the fall hunting season. Predictions for distribution of submerged aquatic vegetation beds can potentially increase hunter observance of voluntary avoidance zones where foraging birds are left alone to feed undisturbed. In years when submersed aquatic vegetation is predicted to be scarce in important wildlife habitats, managers can get the message out to hunters well before the hunting season (Jim Nissen, Upper Mississippi River National Wildlife and Fish Refuge, La Crosse District Manager, La Crosse, Wisconsin, personal communication). We developed a statistical model to predict the probability of occurrence of submersed aquatic vegetation in Pool 8 of the Upper Mississippi River on the basis of a few hydrological, physical, and geomorphic variables. Our model takes into consideration flow velocity, wind fetch, bathymetry, growing-season daily water level, and light extinction coefficient in the river (fig. 1) and calculates the probability of submersed aquatic vegetation existence in Pool 8 in individual 5- x 5-m grid cells. The model was calibrated using the data collected in 1998 (516 sites), 1999 (595 sites), and 2000 (649 sites) using a stratified random sampling protocol (Yin and others, 2000b). To validate the model, we chose the data from the Long Term Resource Monitoring Program (LTRMP) transect sampling in backwater areas (Rogers and Owens 1995; Yin and others, 2000a) and ran the model for each 5- x 5-m grid cell in every growing season from 1991 to 2001. We tallied all the cells and came up with an annual average percent frequency of submersed aquatic vegetation

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

    SciTech Connect

    Peace, Gerald 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

    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.

  14. Sensitivity of Three Vegetation Indices to Cimate and Soil moisture at a Tallgrass Prairie Site

    NASA Astrophysics Data System (ADS)

    Bajgain, R.; Xiao, X.; Wagle, P.; Basara, J. B.

    2014-12-01

    Climatic variability influence vegetation condition and growth, which are often characterized by satellite derived vegetation indices (VIs) such as normalized difference vegetation Index (NDVI), enhanced vegetation Index (EVI) and land surface water index (LSWI). A fourteen-year (2000 - 2013) of NDVI, EVI and LSWI data from Moderate-Resolution Imaging Spectroradiometer (MODIS) were analyzed for assessing grassland vegetation dynamics to climatic variability ( i.e., drought) and soil moisture over the time series at the Marena site, Stillwater Oklahoma,USA. This is also the Marena, Oklahoma In-situ Sensor Testbed (MOISST) site in support of NASA SMAP mission. Change in magnitudes of VIs provided the dynamics of inter-annual variability of the grassland vegetation. The magnitude of VIs declined in dry years (2006 and 2012) .Variation in NDVI and EVI over years resulting from climatic variability was strongly correlated to cumulative seasonal rainfall (NDVI, r = 0.82, EVI, r = 0.77) and average seasonal soil volumetric water content up to 60 cm depth. The EVI declined more than did NDVI during the dry events of 2006 and 2012, indicating that the use of EVI in place of NDVI appears to increase the performance of ecosystem models under drought condition. Furthermore, LSWI was the most sensitive index to drought among the three VIs tested. The LSWI values were negative (LSWI < 0) even within the middle of plant growing season in dry years, showing its potential to track the hydrological status of the ecosystem. Duration of LSWI < 0 in summer was greater in dry years (2006= 53 & 2012= 34 days) compared to wet years (2007 & 2013= 0 days). The result also revealed that LSWI values quantitatively corresponded well with the drought severity categories identified by the United States Drought Monitoring (USDM). In conclusion, the number of days with LSWI < 0 during the plant growing season and LSWI-based drought severity classification scheme can provide useful information for

  15. Roles of Climate, Vegetation and Soil in Regulating the Spatial Variations in Ecosystem Carbon Dioxide Fluxes in the Northern Hemisphere

    PubMed Central

    Chen, Zhi; Yu, Guirui; Ge, Jianping; Wang, Qiufeng; Zhu, Xianjin; Xu, Zhiwei

    2015-01-01

    Climate, vegetation, and soil characteristics play important roles in regulating the spatial variation in carbon dioxide fluxes, but their relative influence is still uncertain. In this study, we compiled data from 241 eddy covariance flux sites in the Northern Hemisphere and used Classification and Regression Trees and Redundancy Analysis to assess how climate, vegetation, and soil affect the spatial variations in three carbon dioxide fluxes (annual gross primary production (AGPP), annual ecosystem respiration (ARE), and annual net ecosystem production (ANEP)). Our results showed that the spatial variations in AGPP, ARE, and ANEP were significantly related to the climate and vegetation factors (correlation coefficients, R = 0.22 to 0.69, P < 0.01) while they were not related to the soil factors (R = -0.11 to 0.14, P > 0.05) in the Northern Hemisphere. The climate and vegetation together explained 60 % and 58 % of the spatial variations in AGPP and ARE, respectively. Climate factors (mean annual temperature and precipitation) could account for 45 - 47 % of the spatial variations in AGPP and ARE, but the climate constraint on the vegetation index explained approximately 75 %. Our findings suggest that climate factors affect the spatial variations in AGPP and ARE mainly by regulating vegetation properties, while soil factors exert a minor effect. To more accurately assess global carbon balance and predict ecosystem responses to climate change, these discrepant roles of climate, vegetation, and soil are required to be fully considered in the future land surface models. Moreover, our results showed that climate and vegetation factors failed to capture the spatial variation in ANEP and suggest that to reveal the underlying mechanism for variation in ANEP, taking into account the effects of other factors (such as climate change and disturbances) is necessary. PMID:25928452

  16. Roles of climate, vegetation and soil in regulating the spatial variations in ecosystem carbon dioxide fluxes in the Northern Hemisphere.

    PubMed

    Chen, Zhi; Yu, Guirui; Ge, Jianping; Wang, Qiufeng; Zhu, Xianjin; Xu, Zhiwei

    2015-01-01

    Climate, vegetation, and soil characteristics play important roles in regulating the spatial variation in carbon dioxide fluxes, but their relative influence is still uncertain. In this study, we compiled data from 241 eddy covariance flux sites in the Northern Hemisphere and used Classification and Regression Trees and Redundancy Analysis to assess how climate, vegetation, and soil affect the spatial variations in three carbon dioxide fluxes (annual gross primary production (AGPP), annual ecosystem respiration (ARE), and annual net ecosystem production (ANEP)). Our results showed that the spatial variations in AGPP, ARE, and ANEP were significantly related to the climate and vegetation factors (correlation coefficients, R = 0.22 to 0.69, P < 0.01) while they were not related to the soil factors (R = -0.11 to 0.14, P > 0.05) in the Northern Hemisphere. The climate and vegetation together explained 60% and 58% of the spatial variations in AGPP and ARE, respectively. Climate factors (mean annual temperature and precipitation) could account for 45-47% of the spatial variations in AGPP and ARE, but the climate constraint on the vegetation index explained approximately 75%. Our findings suggest that climate factors affect the spatial variations in AGPP and ARE mainly by regulating vegetation properties, while soil factors exert a minor effect. To more accurately assess global carbon balance and predict ecosystem responses to climate change, these discrepant roles of climate, vegetation, and soil are required to be fully considered in the future land surface models. Moreover, our results showed that climate and vegetation factors failed to capture the spatial variation in ANEP and suggest that to reveal the underlying mechanism for variation in ANEP, taking into account the effects of other factors (such as climate change and disturbances) is necessary.

  17. Antibiotic resistance genes in manure-amended soil and vegetables at harvest.

    PubMed

    Wang, Feng-Hua; Qiao, Min; Chen, Zheng; Su, Jian-Qiang; Zhu, Yong-Guan

    2015-12-15

    Lettuce and endive, which can be eaten raw, were planted on the manure-amended soil in order to explore the influence of plants on the abundance of antibiotic resistance genes (ARGs) in bulk soil and rhizosphere soil, and the occurrence of ARGs on harvested vegetables. Twelve ARGs and one integrase gene (intI1) were detected in all soil samples. Five ARGs (sulI, tetG, tetC, tetA, and tetM) showed lower abundance in the soil with plants than those without. ARGs and intI1 gene were also detected on harvested vegetables grown in manure-amended soil, including endophytes and phyllosphere microorganisms. The results demonstrated that planting had an effect on the distribution of ARGs in manure-amended soil, and ARGs were detected on harvested vegetables after growing in manure-amended soil, which had potential threat to human health.

  18. Simple equation to approximate the bidirectional reflectance from vegetative canopies and bare soil surfaces

    NASA Technical Reports Server (NTRS)

    Walthall, C. L.; Norman, J. M.; Blad, B. L.; Welles, J. M.; Campbell, G.

    1985-01-01

    A simple equation has been developed for describing the bidirectional reflectance of some vegetative canopies and bare soil surfaces. The equation describes directional reflectance as a function of zenith and azimuth view angles and solar azimuth angle. The equation works for simulated and field measured red and IR reflectance under clear sky conditions. Hemispherical reflectance can be calculated as a function of the simple equation coefficients by integrating the equation over the hemisphere of view angles. A single equation for estimating soil bidirectional reflectance was obtained using the relationships between solar zenith angles and the simple equation coefficients for medium and rough soil distributions. The equation has many useful applications such as providing a lower level boundary condition in complex plant canopy models and providing an additional tool for studying bidirectional effects on pointable sensors.

  19. Establishing an International Soil Modelling Consortium

    NASA Astrophysics Data System (ADS)

    Vereecken, Harry; Schnepf, Andrea; Vanderborght, Jan

    2015-04-01

    Soil is one of the most critical life-supporting compartments of the Biosphere. Soil provides numerous ecosystem services such as a habitat for biodiversity, water and nutrients, as well as producing food, feed, fiber and energy. To feed the rapidly growing world population in 2050, agricultural food production must be doubled using the same land resources footprint. At the same time, soil resources are threatened due to improper management and climate change. Soil is not only essential for establishing a sustainable bio-economy, but also plays a key role also in a broad range of societal challenges including 1) climate change mitigation and adaptation, 2) land use change 3) water resource protection, 4) biotechnology for human health, 5) biodiversity and ecological sustainability, and 6) combating desertification. Soils regulate and support water, mass and energy fluxes between the land surface, the vegetation, the atmosphere and the deep subsurface and control storage and release of organic matter affecting climate regulation and biogeochemical cycles. Despite the many important functions of soil, many fundamental knowledge gaps remain, regarding the role of soil biota and biodiversity on ecosystem services, the structure and dynamics of soil communities, the interplay between hydrologic and biotic processes, the quantification of soil biogeochemical processes and soil structural processes, the resilience and recovery of soils from stress, as well as the prediction of soil development and the evolution of soils in the landscape, to name a few. Soil models have long played an important role in quantifying and predicting soil processes and related ecosystem services. However, a new generation of soil models based on a whole systems approach comprising all physical, mechanical, chemical and biological processes is now required to address these critical knowledge gaps and thus contribute to the preservation of ecosystem services, improve our understanding of climate

  20. Effects of Vegetation and of Heat and Vapor Fluxes from Soil on Snowpack Evolution and Radiobrightness

    NASA Technical Reports Server (NTRS)

    Chung, Y. C.; England, A. W.; DeRoo, R. D.; Weininger, Etai

    2006-01-01

    The radiobrightness of a snowpack is strongly linked to the snow moisture content profile, to the point that the only operational inversion algorithms require dry snow. Forward dynamic models do not include the effects of freezing and thawing of the soil beneath the snowpack and the effect of vegetation within the snow or above the snow. To get a more realistic description of the evolution of the snowpack, we reported an addition to the Snow-Soil-Vegetation-Atmosphere- Transfer (SSVAT) model, wherein we coupled soil processes of the Land Surface Process (LSP) model with the snow model SNTHERM. In the near future we will be adding a radiobrightness prediction based on the modeled moisture, temperature and snow grain size profiles. The initial investigations with this SSVAT for a late winter and early spring snow pack indicate that soil processes warm the snowpack and the soil. Vapor diffusion needs to be considered whenever the ground is thawed. In the early spring, heat flow from the ground into a snow and a strong temperature gradient across the snow lead to thermal convection. The buried vegetation can be ignored for a late winter snow pack. The warmer surface snow temperature will affect radiobrightness since it is most sensitive to snow surface characteristics. Comparison to data shows that SSVAT provides a more realistic representation of the temperature and moisture profiles in the snowpack and its underlying soil than SNTHERM. The radiobrightness module will be optimized for the prediction of brightness when the snow is moist. The liquid water content of snow causes considerable absorption compared to dry snow, and so longer wavelengths are likely to be most revealing as to the state of a moist snowpack. For volumetric moisture contents below about 7% (the pendular regime), the water forms rings around the contact points between snow grains. Electrostatic modeling of these pendular rings shows that the absorption of these rings is significantly higher than a

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

    NASA Technical Reports Server (NTRS)

    Wiegand, C. L. (Principal Investigator)

    1974-01-01

    The author has identified the following significant results. The majority of the rangelands of Hidalgo County, Texas are used in cow-calf operations. Continuous year-long grazing is practiced on about 60% of the acreage and some type of deferred system on the rest. Mechanical brush control is used more than chemical control. Ground surveys gave representative estimates for 15 vegetable crops produced in Hidalgo County. ERTS-1 data were used to estimate the acreage of citrus in the county. Combined Kubleka Munk and regression models, that included a term for shadow areas, gave a higher correlation of composite canopy reflectance with ground truth than either model alone.

  2. Accumulation of Heavy Metals in Vegetable Species Planted in Contaminated Soils and the Health Risk Assessment

    PubMed Central

    Zhou, Hang; Yang, Wen-Tao; Zhou, Xin; Liu, Li; Gu, Jiao-Feng; Wang, Wen-Lei; Zou, Jia-Ling; Tian, Tao; Peng, Pei-Qin; Liao, Bo-Han

    2016-01-01

    The objectives of the present study were to investigate heavy metal accumulation in 22 vegetable species and to assess the human health risks of vegetable consumption. Six vegetable types were cultivated on farmland contaminated with heavy metals (Pb, Cd, Cu, Zn, and As). The target hazard quotient (THQ) method was used to assess the human health risks posed by heavy metals through vegetable consumption. Clear differences were found in the concentrations of heavy metals in edible parts of the different vegetables. The concentrations of heavy metals decreased in the sequence as leafy vegetables > stalk vegetables/root vegetables/solanaceous vegetables > legume vegetables/melon vegetables. The ability of leafy vegetables to uptake and accumulate heavy metals was the highest, and that of melon vegetables was the lowest. This indicated that the low accumulators (melon vegetables) were suitable for being planted on contaminated soil, while the high accumulators (leafy vegetables) were unsuitable. In Shizhuyuan area, China, the total THQ values of adults and children through consumption of vegetables were 4.12 and 5.41, respectively, suggesting that the residents may be facing health risks due to vegetable consumption, and that children were vulnerable to the adverse effects of heavy metal ingestion. PMID:26959043

  3. Accumulation of Heavy Metals in Vegetable Species Planted in Contaminated Soils and the Health Risk Assessment.

    PubMed

    Zhou, Hang; Yang, Wen-Tao; Zhou, Xin; Liu, Li; Gu, Jiao-Feng; Wang, Wen-Lei; Zou, Jia-Ling; Tian, Tao; Peng, Pei-Qin; Liao, Bo-Han

    2016-03-04

    The objectives of the present study were to investigate heavy metal accumulation in 22 vegetable species and to assess the human health risks of vegetable consumption. Six vegetable types were cultivated on farmland contaminated with heavy metals (Pb, Cd, Cu, Zn, and As). The target hazard quotient (THQ) method was used to assess the human health risks posed by heavy metals through vegetable consumption. Clear differences were found in the concentrations of heavy metals in edible parts of the different vegetables. The concentrations of heavy metals decreased in the sequence as leafy vegetables > stalk vegetables/root vegetables/solanaceous vegetables > legume vegetables/melon vegetables. The ability of leafy vegetables to uptake and accumulate heavy metals was the highest, and that of melon vegetables was the lowest. This indicated that the low accumulators (melon vegetables) were suitable for being planted on contaminated soil, while the high accumulators (leafy vegetables) were unsuitable. In Shizhuyuan area, China, the total THQ values of adults and children through consumption of vegetables were 4.12 and 5.41, respectively, suggesting that the residents may be facing health risks due to vegetable consumption, and that children were vulnerable to the adverse effects of heavy metal ingestion.

  4. Evaluation of Soil Moisture Estimation in Vegetated Areas Using Compact Polarimetry

    NASA Astrophysics Data System (ADS)

    Yan, Jian; Chen, Lin; Yin, Qiang; Li, Yang; Hong, Wen

    2010-12-01

    Within the framework of the DRAGON project, in this paper, we preliminarily analyze the soil moisture estimation performance in vegetated areas based on Water-Cloud model and Dubois model using compact polarimetry. We compare the inversion results of the compact polarimetry (CP) data to those of the dual polarimetric data (DP, HH and VV) and to the in-situ data. The comparison indicates that the retrieved parameters from original DP data are mainly in consistence with ground measured values, but the estimated parameters from the reconstructed data of CP are not quite consistent with the in-situ values, especially for the moisture.

  5. Evaluation of Landsat Multispectral Scanner data for mapping vegetated soil landscapes

    USGS Publications Warehouse

    Thompson, D. R.; Haas, Robert H.; Milford, M. H.

    1981-01-01

    Landsat multispectral scanner data for Brazos County, Texas, were evaluated in terms of effectiveness for classifying soils on vegetated landscapes at three times during the year: a time of normally adequate soil water, a time of expected soil water deficit, and a time when soil water is normally being replenished. Six test sites were used to evaluate LARSYS supervised and unsupervised classification of vegetated soil landscapes. Open grassland soils were best separated in the fall during a period when soil moisture was being replenished after the summer period of soil water deficit. Woodland soils were separated by Landsat data in late spring when adequate moisture was available. However, a high degree of accuracy was not achieved using Landsat for separating soil map units. Accurate separation of soil mapping units on vegetated landscapes was not possible during late summer when soil water was deficient. Selected soil properties important to plant growth were separable on the test sites using June and October Landsat data. Particle size and soil moisture regime were separated at both dates. Soils with argillic horizons were separated from soils without argillic horizons.

  6. Greenland soil bacteria & biogeochemistry: a vegetation cover proxy for climate warming effects

    NASA Astrophysics Data System (ADS)

    Dowdy, K. L.; Sistla, S.; Buckeridge, K. M.; Schimel, J.; Schaeffer, S. M.

    2013-12-01

    Climate warming in the high Arctic is expected to increase plant biomass, deepen thaw, and stimulate decomposition of soil organic matter. However, it remains unclear how warming, plant growth, and microbial processing will interact to drive Arctic carbon and nutrient cycling. For example, greater plant growth should increase carbon storage in the ecosystem; however, increasing plant C inputs and thawing permafrost carbon should stimulate microbial biomass, potentially causing soil respiration to outpace storage. Alternatively, greater plant cover may lower soil temperature through shading, potentially curtailing the predicted increase in microbial activity. To evaluate microbial responses to climate warming in the high Arctic, we characterized the soil bacterial community and related soil biogeochemical properties, including pH, temperature, moisture, bulk density, extractable nutrient pools, extractable organic carbon and nitrogen, and total microbial biomass along a vegetation cover gradient in northwest Greenland. Vegetation cover was classified using the Normalized Difference Vegetation Index (NDVI), and vegetation cover classes were used as a proxy for changes associated with warming. We found that soil moisture increased and soil temperature decreased significantly with vegetation cover; moisture and temperature were higher in organic than in mineral horizons. Extractable nutrients (NO3-, NH4+, PO43-) and extractable organic C and N generally increased with vegetation cover and are higher in organic than in mineral horizons within a given vegetation class, with the exception of NO3-, which was comparable between horizons. Despite increases in available carbon and nutrients, microbial biomass carbon in both horizons ultimately decreased with vegetation cover, as did microbial biomass nitrogen in the mineral horizon. Moreover, the relative proportion of microbial biomass carbon to extractable organic carbon decreased with vegetation cover, indicating that

  7. Radar backscattering measurement of bare soil and vegetation covered soil using X-band and full polarization

    NASA Astrophysics Data System (ADS)

    Goswami, B.; Kalita, M.

    2014-11-01

    The objective of the study is to measure backscattered power of bare soil and vegetation covered soil using X-band scatterometer system with full polarization and various angles during monsoon season and relate backscattered power to the density of vegetation over soil. The measurement was conducted at an experimental field located in the campus of Assam Engineering College, Guwahati, India. The soil sample consists of Silt and Clay in higher proportions as compared to Sand. The scatterometer system consists of dual-polarimetric square horn antennas, Power meter, Klystron, coaxial cables, isolator and waveguide detector. The polarization of the horn antennas as well as the look angle can be changed in the set-up. The backscattering coefficients were calculated by applying a radar equation for the measured values at incident angles between 30° and 60° for full polarization (HH, VV, HV, VH), respectively, and compared with vegetation cover over soil for each scatterometer measurement simultaneously. The VH polarization and 60° look angle are found to be the most suitable combination of configuration of an X-band scatterometer for distinguishing the land cover targets such as bare soil and vegetation covered soil. From the analysis of the results, polarimetric scatterometer data appear to be promising to distinguish the land cover types such as bare soil and soil completely covered by vegetation. The results of this study will help the scientists working in the field of active microwave remote sensing.

  8. Comparison modeling for alpine vegetation distribution in an arid area.

    PubMed

    Zhou, Jihua; Lai, Liming; Guan, Tianyu; Cai, Wetao; Gao, Nannan; Zhang, Xiaolong; Yang, Dawen; Cong, Zhentao; Zheng, Yuanrun

    2016-07-01

    Mapping and modeling vegetation distribution are fundamental topics in vegetation ecology. With the rise of powerful new statistical techniques and GIS tools, the development of predictive vegetation distribution models has increased rapidly. However, modeling alpine vegetation with high accuracy in arid areas is still a challenge because of the complexity and heterogeneity of the environment. Here, we used a set of 70 variables from ASTER GDEM, WorldClim, and Landsat-8 OLI (land surface albedo and spectral vegetation indices) data with decision tree (DT), maximum likelihood classification (MLC), and random forest (RF) models to discriminate the eight vegetation groups and 19 vegetation formations in the upper reaches of the Heihe River Basin in the Qilian Mountains, northwest China. The combination of variables clearly discriminated vegetation groups but failed to discriminate vegetation formations. Different variable combinations performed differently in each type of model, but the most consistently important parameter in alpine vegetation modeling was elevation. The best RF model was more accurate for vegetation modeling compared with the DT and MLC models for this alpine region, with an overall accuracy of 75 % and a kappa coefficient of 0.64 verified against field point data and an overall accuracy of 65 % and a kappa of 0.52 verified against vegetation map data. The accuracy of regional vegetation modeling differed depending on the variable combinations and models, resulting in different classifications for specific vegetation groups. PMID:27307276

  9. Comparison modeling for alpine vegetation distribution in an arid area.

    PubMed

    Zhou, Jihua; Lai, Liming; Guan, Tianyu; Cai, Wetao; Gao, Nannan; Zhang, Xiaolong; Yang, Dawen; Cong, Zhentao; Zheng, Yuanrun

    2016-07-01

    Mapping and modeling vegetation distribution are fundamental topics in vegetation ecology. With the rise of powerful new statistical techniques and GIS tools, the development of predictive vegetation distribution models has increased rapidly. However, modeling alpine vegetation with high accuracy in arid areas is still a challenge because of the complexity and heterogeneity of the environment. Here, we used a set of 70 variables from ASTER GDEM, WorldClim, and Landsat-8 OLI (land surface albedo and spectral vegetation indices) data with decision tree (DT), maximum likelihood classification (MLC), and random forest (RF) models to discriminate the eight vegetation groups and 19 vegetation formations in the upper reaches of the Heihe River Basin in the Qilian Mountains, northwest China. The combination of variables clearly discriminated vegetation groups but failed to discriminate vegetation formations. Different variable combinations performed differently in each type of model, but the most consistently important parameter in alpine vegetation modeling was elevation. The best RF model was more accurate for vegetation modeling compared with the DT and MLC models for this alpine region, with an overall accuracy of 75 % and a kappa coefficient of 0.64 verified against field point data and an overall accuracy of 65 % and a kappa of 0.52 verified against vegetation map data. The accuracy of regional vegetation modeling differed depending on the variable combinations and models, resulting in different classifications for specific vegetation groups.

  10. Illuminating hydrological processes at the soil-vegetation-atmosphere interface with water stable isotopes

    NASA Astrophysics Data System (ADS)

    Sprenger, Matthias; Leistert, Hannes; Gimbel, Katharina; Weiler, Markus

    2016-09-01

    Water stable isotopes (18O and 2H) are widely used as ideal tracers to track water through the soil and to separate evaporation from transpiration. Due to the technical developments in the last two decades, soil water stable isotope data have become easier to collect. Thus, the application of isotope methods in soils is growing rapidly. Studies that make use of soil water stable isotopes often have a multidisciplinary character since an interplay of processes that take place in the vadose zone has to be considered. In this review, we provide an overview of the hydrological processes that alter the soil water stable isotopic composition and present studies utilizing pore water stable isotopes. The processes that are discussed include the water input as precipitation or throughfall, the output as evaporation, transpiration, or recharge, and specific flow and transport processes. Based on the review and supported by additional data and modeling results, we pose a different view on the recently proposed two water world hypothesis. As an alternative to two distinct pools of soil water, where one pool is enriched in heavy isotopes and used by the vegetation and the other pool does not undergo isotopic fractionation and becomes recharge, the water gets successively mixed with newly introduced rainwater during the percolation process. This way, water initially isotopically enriched in the topsoil loses the fractionation signal with increasing infiltration depth, leading to unfractionated isotopic signals in the groundwater.

  11. Soils and vegetation of Santa Barbara Island, Channel Islands National Park, California, USA

    NASA Astrophysics Data System (ADS)

    Halvorson, William L.; Fenn, Dennis B.; Allardice, William R.

    1988-01-01

    The multifaceted development of an erosion surface on Santa Barbara Island, Channel Islands National Park, California, has led to this study of the relationship between soils and vegetation. A dry Mediterranean climate and past attempts at farming and introductions of alien species have led to vegetative degradation accompanied by both gully and surface erosion. Soil and vegetation analyses show this erosion to be in a location of transition. The soils are Typic Chromoxererts (Vertisol Order) with high clay, salinity, and sodium contents. The vegetation is ecotonal in nature, grading from a principally alien annual grassland with Avena fatua and Atriplex semibaccata to a shrub community dominated by the native Suaeda californica. Management toward revegetation and stabilization of this island ecosystem will be difficult with high clay, saline-sodic soils and disturbed vegetation.

  12. Effects of Vegetation Removal and Soil Disturbance on Soil Organic and Inorganic Carbon Dynamics in California Desert Ecosystems

    NASA Astrophysics Data System (ADS)

    Swanson, A. C.; Allen, E. B.; Allen, M. F.; Hernandez, R. R.

    2015-12-01

    Solar energy developments are projected to be deployed over desert wildland areas with deep soil inorganic carbon (SIC) deposits, which often involves elimination of deep-rooted vegetation. This land cover change may systemically alter SIC pools since respired CO2 is the carbon (C) source during SIC formation. We sought to understand how removal of creosote bush scrub affects soil C pools. We hypothesized that vegetation is important for maintaining SIC and soil organic C (SOC) pools and that disturbance to the vegetation and soil will change CO2 flux with increased losses from SIC. Soils were collected from sites that had intact creosote bush scrub habitat adjacent to disturbed, bare areas where the native vegetation had been previously removed. Samples were taken from beneath shrub canopies and interspaces in intact areas, and from random points in the disturbed area. Soils were analyzed for SIC, SOC, microbial and labile C, and δ13C. Soils were also incubated to determine the potential CO2 flux from disturbed and undisturbed soils along with the sources of CO2. Three replicates per soil underwent a control and water addition treatment and flux and δ13C of CO2 were measured continuously. Control replicates yielded no significant CO2 flux. CO2 flux from watered soils was higher beneath shrub canopy (18.57µmol g soil-1 day-1±1.86) than the interspace soils (0.86 µmol g soil-1 day-1±0.17). Soils collected from bare areas had an intermediate flux (5.41 µmol g soil-1 day-1±2.68 and 3.68 µmol g soil-1 day-1±0.85, respectively) lying between shrub canopy and interspace soils. There was no significant difference between the δ13C values of CO2 from shrub canopy and interspace soils, both of which had a very low δ13C values (-22.60‰±0.64 and -23.88‰±0.89, respectively), resembling that of organic C. However, the isotopic values of CO2 from disturbed soils were significantly higher (-16.68‰±1.36 and -15.22‰±2.12, respectively) suggesting that these

  13. The effect of vegetation on infiltration in shallow soils underlain by fissured bedrock

    NASA Astrophysics Data System (ADS)

    Stothoff, S. A.; Or, D.; Groeneveld, D. P.; Jones, S. B.

    1999-05-01

    Mean annual infiltration above the high-level waste repository proposed to be sited at Yucca Mountain, Nevada, has a large impact on assessments of repository performance. Ongoing investigations of infiltration processes have identified the relatively horizontal caprock environment above portions of the repository as a potentially large source of infiltrating waters, due to shallow, permeable soils above a moderately welded tuff with large soil-filled fissures. The combination of shallow soils and fissured bedrock allows rapid penetration of wetting pulses to below the rooting zone. Plant uptake can strongly reduce net infiltration in arid environments with high water storage capacity, and, despite the low water storage capacity, there is a relatively high vegetation density in this environment. The apparent discrepancy between high vegetation density and low water storage motivates the study of plant-hydrologic interactions in this semiarid environment. Field observations were coupled with plant- and landscape-scale models to provide insight into plant-hydrologic interactions. Several lines of evidence, including: (i) linear plant growth features observed on aerial photographs; (ii) comparisons of plant cover within the fissured environment and comparable environments lacking fissures; and (iii) direct excavations, all suggest that the widely spaced soil-filled fissures are conducive to plant growth even when fissures are buried at soil depths exceeding 30 cm. Results from a mechanistic simulation model for root growth into fissures suggest that the additional (sheltered) plant-available soil water within fissures provides a competitive advantage for plant establishment. Therefore, plants that germinate above a fissure are more likely to survive, in turn developing linear features above fissures. Having established that plants preferentially root within soil-filled fissures in the caprock environment, a set of simulations were performed to examine the hydrologic

  14. Evidence of climatic effects on soil, vegetation and landform in temperate forests of south-eastern Australia

    NASA Astrophysics Data System (ADS)

    Inbar, Assaf; Nyman, Petter; Lane, Patrick; Sheridan, Gary

    2016-04-01

    Water and radiation are unevenly distributed across the landscape due to variations in topography, which in turn causes water availability differences on the terrain according to elevation and aspect orientation. These differences in water availability can cause differential distribution of vegetation types and indirectly influence the development of soil and even landform, as expressed in hillslope asymmetry. While most of the research on the effects of climate on the vegetation and soil development and landscape evolution has been concentrated in drier semi-arid areas, temperate forested areas has been poorly studied, particularly in South Eastern Australia. This study uses soil profile descriptions and data on soil depth and landform across climatic gradients to explore the degrees to which coevolution of vegetation, soils and landform are controlled by radiative forcing and rainfall. Soil depth measurements were made on polar and equatorial facing hillslopes located at 3 sites along a climatic gradient (mean annual rainfall between 700 - 1800 mm yr-1) in the Victorian Highlands, where forest types range from dry open woodland to closed temperate rainforest. Profile descriptions were taken from soil pits dag on planar hillslopes (50 m from ridge), and samples were taken from each horizon for physical and chemical properties analysis. Hillslope asymmetry in different precipitation regimes of the study region was quantified from Digital Elevation Models (DEMs). Significant vegetation differences between aspects were noted in lower and intermediate rainfall sites, where polar facing aspects expressed higher overall biomass than the drier equatorial slope. Within the study domain, soil depth was strongly correlated with forest type and above ground biomass. Soil depths and chemical properties varied between topographic aspects and along the precipitation gradient, where wetter conditions facilitate deeper and more weathered soils. Furthermore, soil depths showed

  15. The Changing Model of Soil

    NASA Astrophysics Data System (ADS)

    Richter, D. D.; Yaalon, D.

    2012-12-01

    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.

  16. The contribution of vegetation cover and bare soil to pixel reflectance in an arid ecosystem

    NASA Astrophysics Data System (ADS)

    Steele, C. M.; Smith, A.; Campanella, A.; Rango, A.

    2008-12-01

    The heterogeneity of vegetation and soils in arid and semi-arid environments complicates the analysis of medium spatial resolution remotely sensed imagery. A single pixel may contain several different types of vegetation, as well as a sizeable proportion of bare soil. We have used linear mixture modeling to explore the contribution of vegetation cover and bare soil to pixel reflectance. In October, 2006, aerial imagery (0.25 m spatial resolution) was acquired for our study sites in the Jornada Experimental Range, southern New Mexico. Imagery was also acquired from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) for June and November, 2006. These data corresponded with pre- and post monsoon conditions. Object-based feature extraction was used to classify the aerial imagery to shrub, grass and bare ground cover classes. Percent cover was then calculated for each cover class. Visible-near-infrared and shortwave infrared ASTER reflectance data from both dates were combined into a single 18-band dataset (30 m spatial resolution). A vector overlay from the classification results of the aerial imagery was used to define pure endmember pixels in the ASTER imagery. Estimates of the proportions of shrub, grass and bare ground cover from the linear mixture modeling approach were compared with cover calculated using feature extraction from the aerial imagery. The results indicate that reflectance in ASTER pixels is likely to be a linear combination of the cover proportions of the three main cover types (shrubs, grass, bare ground). However, noticeable outliers in the relationship between cover calculated from each method, indicate there may be other variables that affect the accuracy with which we can estimate cover using linear mixture modeling.

  17. Evaluation of MODIS NDVI and NDWI for vegetation drought monitoring using Oklahoma Mesonet soil moisture data

    USGS Publications Warehouse

    Gu, Y.; Hunt, E.; Wardlow, B.; Basara, J.B.; Brown, J.F.; Verdin, J.P.

    2008-01-01

    The evaluation of the relationship between satellite-derived vegetation indices (normalized difference vegetation index and normalized difference water index) and soil moisture improves our understanding of how these indices respond to soil moisture fluctuations. Soil moisture deficits are ultimately tied to drought stress on plants. The diverse terrain and climate of Oklahoma, the extensive soil moisture network of the Oklahoma Mesonet, and satellite-derived indices from the Moderate Resolution Imaging Spectroradiometer (MODIS) provided an opportunity to study correlations between soil moisture and vegetation indices over the 2002-2006 growing seasons. Results showed that the correlation between both indices and the fractional water index (FWI) was highly dependent on land cover heterogeneity and soil type. Sites surrounded by relatively homogeneous vegetation cover with silt loam soils had the highest correlation between the FWI and both vegetation-related indices (r???0.73), while sites with heterogeneous vegetation cover and loam soils had the lowest correlation (r???0.22). Copyright 2008 by the American Geophysical Union.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    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.

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

    PubMed

    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

    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.

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

    PubMed Central

    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

    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

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

    PubMed

    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

    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

  2. Assembly Processes under Severe Abiotic Filtering: Adaptation Mechanisms of Weed Vegetation to the Gradient of Soil Constraints

    PubMed Central

    Nikolic, Nina; Böcker, Reinhard; Kostic-Kravljanac, Ljiljana; Nikolic, Miroslav

    2014-01-01

    Questions Effects of soil on vegetation patterns are commonly obscured by other environmental factors; clear and general relationships are difficult to find. How would community assembly processes be affected by a substantial change in soil characteristics when all other relevant factors are held constant? In particular, can we identify some functional adaptations which would underpin such soil-induced vegetation response? Location Eastern Serbia: fields partially damaged by long-term and large-scale fluvial deposition of sulphidic waste from a Cu mine; subcontinental/submediterranean climate. Methods We analysed the multivariate response of cereal weed assemblages (including biomass and foliar analyses) to a strong man-made soil gradient (from highly calcareous to highly acidic, nutrient-poor soils) over short distances (field scale). Results The soil gradient favoured a substitution of calcicoles by calcifuges, and an increase in abundance of pseudometallophytes, with preferences for Atlantic climate, broad geographical distribution, hemicryptophytic life form, adapted to low-nutrient and acidic soils, with lower concentrations of Ca, and very narrow range of Cu concentrations in leaves. The trends of abundance of the different ecological groups of indicator species along the soil gradient were systematically reflected in the maintenance of leaf P concentrations, and strong homeostasis in biomass N:P ratio. Conclusion Using annual weed vegetation at the field scale as a fairly simple model, we demonstrated links between gradients in soil properties (pH, nutrient availability) and floristic composition that are normally encountered over large geographic distances. We showed that leaf nutrient status, in particular the maintenance of leaf P concentrations and strong homeostasis of biomass N:P ratio, underpinned a clear functional response of vegetation to mineral stress. These findings can help to understand assembly processes leading to unusual, novel combinations

  3. Monitoring seasonal variations of soil moisture and vegetation cover using satellite microwave radiometry

    NASA Technical Reports Server (NTRS)

    Kerr, Y. H.; Njoku, E. G.

    1988-01-01

    The NIMBUS-7 scanning multichannel microwave radiometer measured brightness temperatures at 5 frequencies (6.6, 10.7, 18, 21, 37 GHz), all dual-polarized with a 50 deg incidence angle over Africa since 1978. A 3 yr data set is being processed (1983 to 1985), and a theoretical model was developed, allowing investigation of the microwave emissivity of land features in the frequency range 6.6 to 37 GHz and of the extent to which vegetation and roughness can be determined in order to improve the soil moisture estimation.

  4. 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)

    Katata, Genki; Held, Andreas; Mauder, Matthias

    2014-05-01

    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.

  5. Quantifying the influence of deep soil moisture on ecosystem albedo: The role of vegetation

    NASA Astrophysics Data System (ADS)

    Sanchez-Mejia, Zulia Mayari; Papuga, Shirley Anne; Swetish, Jessica Blaine; van Leeuwen, Willem Jan Dirk; Szutu, Daphne; Hartfield, Kyle

    2014-05-01

    As changes in precipitation dynamics continue to alter the water availability in dryland ecosystems, understanding the feedbacks between the vegetation and the hydrologic cycle and their influence on the climate system is critically important. We designed a field campaign to examine the influence of two-layer soil moisture control on bare and canopy albedo dynamics in a semiarid shrubland ecosystem. We conducted this campaign during 2011 and 2012 within the tower footprint of the Santa Rita Creosote Ameriflux site. Albedo field measurements fell into one of four Cases within a two-layer soil moisture framework based on permutations of whether the shallow and deep soil layers were wet or dry. Using these Cases, we identified differences in how shallow and deep soil moisture influence canopy and bare albedo. Then, by varying the number of canopy and bare patches within a gridded framework, we explore the influence of vegetation and soil moisture on ecosystem albedo. Our results highlight the importance of deep soil moisture in land surface-atmosphere interactions through its influence on aboveground vegetation characteristics. For instance, we show how green-up of the vegetation is triggered by deep soil moisture, and link deep soil moisture to a decrease in canopy albedo. Understanding relationships between vegetation and deep soil moisture will provide important insights into feedbacks between the hydrologic cycle and the climate system.

  6. Impact of vegetation change on the mobility of uranium- and thorium-series nuclides in soils

    NASA Astrophysics Data System (ADS)

    Gontier, A.; Rihs, S.; Turpault, M.-P.; Chabaux, F.

    2012-04-01

    The effect of land cover change on chemical mobility and soil response was investigated using short- and long-lived nuclides from the U- and Th series. Indeed, the matching of these nuclides half-live to the pedogenic processes rates make these nuclides especially suitable to investigate either time or mechanism of transfers within a soil-water-plant system. This study was carried out from the experimental Breuil-Chenue site (Morvan mountains, France). The native forest (150 year-old) was partially clear-felled and replaced in 1976 by mono-specific plantations distributed in different stands. Following this cover-change, some mineralogical changes in the acid brown soil were recognized (Mareschal, 2008). Three soil sections were sampled under the native forest and the replanted oak and Douglas spruce stands respectively. The (238U), (234U), (230Th), (226Ra), (232Th) and (228Ra) activities were analysed by thermal ionization mass spectrometry (TIMS), inductively coupled plasma mass spectrometry (MC-ICPMS) and gamma spectrometry. Significant differences in U, Th, and Ra activities were observed between the soils located under the native forest or the replanted-trees stands, mostly dominated by a large uranium mobilization from the replanted soils. Moreover, all the investigated U and Th-series activity ratios show a contrasted trend between the shallowest horizons (0-50cm) and the deepest one (below 50cm), demonstrating the chemical effect of the vegetation change on the shallow soil layers. Using a continuous open-system leaching model, the coupled radioactive disequilibria measured in the different soil layers permit to quantify the rate of the radionuclides mobilities. Reference: Mareschal, L., 2008. Effet des substitutions d'essences forestières sur l'évolution des sols et de leur minéralogie : bilan après 28 ans dans le site expérimental de Breuil (Morvan) Université Henri Poincaré, Nancy-I.

  7. Individual contributions of climate and vegetation change to soil moisture trends across multiple spatial scales

    PubMed Central

    Feng, Huihui

    2016-01-01

    Climate and vegetation change are two dominating factors for soil moisture trend. However, their individual contributions remain unknown due to their complex interaction. Here, I separated their contributions through a trajectory-based method across the global, regional and local scales. Our results demonstrated that climate change accounted for 98.78% and 114.64% of the global drying and wetting trend. Vegetation change exhibited a relatively weak influence (contributing 1.22% and −14.64% of the global drying and wetting) because it occurred in a limited area on land. Regionally, the impact of vegetation change cannot be neglected, which contributed −40.21% of the soil moisture change in the wetting zone. Locally, the contributions strongly correlated to the local environmental characteristics. Vegetation negatively affected soil moisture trends in the dry and sparsely vegetated regions and positively in the wet and densely vegetated regions. I conclude that individual contributions of climate and vegetation change vary at the global, regional and local scales. Climate change dominates the soil moisture trends, while vegetation change acts as a regulator to drying or wetting the soil under the changing climate. PMID:27600157

  8. Individual contributions of climate and vegetation change to soil moisture trends across multiple spatial scales.

    PubMed

    Feng, Huihui

    2016-01-01

    Climate and vegetation change are two dominating factors for soil moisture trend. However, their individual contributions remain unknown due to their complex interaction. Here, I separated their contributions through a trajectory-based method across the global, regional and local scales. Our results demonstrated that climate change accounted for 98.78% and 114.64% of the global drying and wetting trend. Vegetation change exhibited a relatively weak influence (contributing 1.22% and -14.64% of the global drying and wetting) because it occurred in a limited area on land. Regionally, the impact of vegetation change cannot be neglected, which contributed -40.21% of the soil moisture change in the wetting zone. Locally, the contributions strongly correlated to the local environmental characteristics. Vegetation negatively affected soil moisture trends in the dry and sparsely vegetated regions and positively in the wet and densely vegetated regions. I conclude that individual contributions of climate and vegetation change vary at the global, regional and local scales. Climate change dominates the soil moisture trends, while vegetation change acts as a regulator to drying or wetting the soil under the changing climate. PMID:27600157

  9. Individual contributions of climate and vegetation change to soil moisture trends across multiple spatial scales.

    PubMed

    Feng, Huihui

    2016-09-07

    Climate and vegetation change are two dominating factors for soil moisture trend. However, their individual contributions remain unknown due to their complex interaction. Here, I separated their contributions through a trajectory-based method across the global, regional and local scales. Our results demonstrated that climate change accounted for 98.78% and 114.64% of the global drying and wetting trend. Vegetation change exhibited a relatively weak influence (contributing 1.22% and -14.64% of the global drying and wetting) because it occurred in a limited area on land. Regionally, the impact of vegetation change cannot be neglected, which contributed -40.21% of the soil moisture change in the wetting zone. Locally, the contributions strongly correlated to the local environmental characteristics. Vegetation negatively affected soil moisture trends in the dry and sparsely vegetated regions and positively in the wet and densely vegetated regions. I conclude that individual contributions of climate and vegetation change vary at the global, regional and local scales. Climate change dominates the soil moisture trends, while vegetation change acts as a regulator to drying or wetting the soil under the changing climate.

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

    SciTech Connect

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

    2005-02-01

    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.

  11. Capturing Vegetation Diversity in the Ent Terrestrial Biosphere Model

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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

  12. Relationship between polychlorinated dibenzo-p-dioxin, polychlorinated dibenzofuran, and dioxin-like polychlorinated biphenyl concentrations in vegetation and soil on residential properties.

    PubMed

    Demond, Avery; Towey, Timothy; Adriaens, Peter; Zhong, Xiaobo; Knutson, Kristine; Chen, Qixuan; Hong, Biling; Gillespie, Brenda; Franzblau, Alfred; Garabrant, David; Lepkowski, James; Luksemburg, William; Maier, Martha

    2010-12-01

    The University of Michigan Dioxin Exposure Study was undertaken to address concerns that the industrial discharge of dioxin-like compounds in the Midland, Michigan, USA area had resulted in the contamination of soil and vegetation in the Tittabawassee River floodplain and downwind of the incinerator in the City of Midland. The study included the analysis of 597 vegetation samples, predominantly grass and weeds, from residential properties selected through a multistage probabilistic sample design in the Midland area, and in Jackson and Calhoun Counties (Michigan), as a background comparison, for 29 polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and polychlorinated biphenyls (PCBs). The mean toxic equivalent (TEQ) of the house perimeter vegetation samples ranged from 4.2 to 377 pg/g. The ratio of TEQs (vegetation to soil) was about 0.3, with a maximum of 3.5. Based on a calculation of the similarity of the congener patterns between the soil and the vegetation, it appeared that the source of the contamination on the vegetation was the surrounding soil. This conclusion was supported by linear regression analysis, which showed that the largest contributor to the R(2) for the outcome variable of log(10) of the vegetation concentration was log(10) of the surrounding soil concentration. Models of vegetation contamination usually focus on atmospheric deposition and partitioning. The results obtained here suggest that the deposition of soil particles onto vegetation is a significant route of contamination for residential herbage. Thus, the inclusion of deposition of soil particles onto vegetation is critical to the accurate modeling of contamination residential herbage in communities impacted by historic industrial discharges of persistent organic compounds.

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

    NASA Astrophysics Data System (ADS)

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

    2008-12-01

    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.

  14. Role of native and exotic woody vegetation in soil restoration in active gully systems (southern Ecuador)

    NASA Astrophysics Data System (ADS)

    Borja Ramon, Pablo; Alvarado Moncayo, Dario; Vanacker, Veerle; Cisneros, Pedro; Molina, Armando; Govers, Gerard

    2015-04-01

    Revegetation projects in degraded lands have the potential to recover essential soil functions. If vegetation restoration is combined with bioengineering techniques, such as the construction of retention dams in active gully systems, soil restoration could be enhanced. One important aspect of this process is the role of vegetation on restoration of soil chemical and physical properties. There is currently a lack of knowledge on the potential of soil restoration in active badland systems, as most studies have concentrated on the direct and visible effect of revegetation on erosion control. The aim of this study is to evaluate the role of revegetation and bioengineering works on the restoration of soil physical and chemical properties. The analyses are realized in a highly degraded area of 3 km2, located in the lower part of the Loreto catchment (Southern Ecuadorian Andes). First, the soil physical and/or chemical parameters that are most sensitive to track environmental change were evaluated. Second, the role of vegetation on soil restoration was quantified. . Soil samples were taken in sites with different vegetation cover, land use and physiographic position. The following physical and chemical parameters were measured: volumetric water content (θsat, θact), bulk density, pH, texture, organic matter, C and N content. Our first results do not show a clear relationship between volumetric water content at saturation (θsat), bulk density, or C content. The saturation water content does not vary significantly between different sites, or land use types. However, significant differences are found between sites at different stages of restoration; and this for most chemical and physical soil properties. Vegetation cover (%) appears to exert a strong control on the C content in the mineral soils. The highest C values are found in soils of forest plantations with Eucalyptus and Pinus species. These plantations are located in areas that were previously affected by active

  15. The influence of precipitation, vegetation and soil properties on the ecohydrology of sagebrush steppe rangelands on the INL site

    USGS Publications Warehouse

    Germino, Matthew J.

    2013-01-01

    The INL Site and other landscapes having sagebrush steppe vegetation are experiencing a simultaneous change in climate and floristics that result from increases in exotic species. Determining the separate and combined/interactive effects of climate and vegetation change is important for assessing future changes on the landscape and for hydrologic processes. This research uses the 72 experimental plots established and initially maintained for many years as the “Protective Cap Biobarrier Experiment” by Dr. Jay Anderson and the Stoller ESER program, and the experiment is also now referred to as the “INL Site Ecohydrology Study.” We are evaluating long-term impacts of different plant communities commonly found throughout Idaho subject to different precipitation regimes and to different soil depths. Treatments of amount and timing of precipitation (irrigation), soil depth, and either native/perennial or exotic grass vegetation allow researchers to investigate how vegetation, precipitation and soil interact to influence soil hydrology and ecosystem biogeochemistry. This information will be used to improve a variety of models, as well as provide data for these models.

  16. Bioremediation of petroleum contaminated soil using vegetation. A microbial study

    SciTech Connect

    Lee, E.; Banks, M.K. )

    1993-12-01

    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 weeks after planting. Microbial numbers were substantially greater in soil with plants when compared to soil containing no plants, indicating that plant roots enhanced microbial populations in contaminated soil. Soil treatments had no effect on microbial numbers in the presence of plants. 12 refs., 3 figs., 1 tab.

  17. Climate-vegetation-soil interactions and long-term hydrologic partitioning: signatures of catchment co-evolution

    NASA Astrophysics Data System (ADS)

    Troch, P. A.; Carrillo, G.; Sivapalan, M.; Wagener, T.; Sawicz, K.

    2013-03-01

    Catchment hydrologic partitioning, regional vegetation composition and soil properties are strongly affected by climate, but the effects of climate-vegetation-soil interactions on river basin water balance are still poorly understood. Here we use a physically-based hydrologic model separately parameterized in 12 US catchments across a climate gradient to decouple the impact of climate and landscape properties to gain insight into the role of climate-vegetation-soil interactions in long-term hydrologic partitioning. The 12 catchment models (with different parameterizations) are subjected to the 12 different climate forcings, resulting in 144 10-yr model simulations. The results are analyzed per catchment (one catchment model subjected to 12 climates) and per climate (one climate filtered by 12 different model parameterization), and compared to water balance predictions based on Budyko's hypothesis (E/P = φ (EP/P); E: evaporation, P: precipitation, EP: potential evaporation). We find significant anti-correlation between average deviations of the evaporation index (E/P) computed per catchment vs. per climate, compared to that predicted by Budyko. Catchments that on average produce more E/P have developed in climates that on average produce less E/P, when compared to Budyko's prediction. Water and energy seasonality could not explain these observations, confirming previous results reported by Potter et al. (2005). Next, we analyze which model (i.e., landscape filter) characteristics explain the catchment's tendency to produce more or less E/P. We find that the time scale that controls perched aquifer storage release explains the observed trend. This time scale combines several geomorphologic and hydraulic soil properties. Catchments with relatively longer aquifer storage release time scales produce significantly more E/P. Vegetation in these catchments have longer access to this additional groundwater source and thus are less prone to water stress. Further analysis

  18. [Heidaigou Opencast Coal Mine: Soil Enzyme Activities and Soil Physical and Chemical Properties Under Different Vegetation Restoration].

    PubMed

    Fang, Ying; Ma, Ren-tian; An, Shao-shan; Zhao, Jun-feng; Xiao, Li

    2016-03-15

    Choosing the soils under different vegetation recovery of Heidaigou dump as the research objects, we mainly analyzed their basic physical and chemical properties and enzyme activities with the method of Analysis of Variance as well as their relations using Pearson correlation analysis and path analysis hoping to uncover the driving factors of the differences between soil enzyme activities under different vegetation restoration, and provide scientific suggestions for the plant selection as well as make a better evaluation to the reclamation effect. The results showed that: (1) Although the artificial vegetation restoration improved the basic physical and chemical properties of the soils while increasing their enzyme activities to a certain extent, the soil conditions still did not reach the level of the natural grassland; (2) Contents of soil organic carbon (SOC) and soil total nitrogen (TN) of the seabuckthorns were the nearest to those of the grassland, which reached 54. 22% and 70. 00% of those of the grassland. In addition, the soil bulk density of the seabuckthorns stand was 17. 09% lower than the maximum value of the amorpha fruitcosa land. The SOC and TN contents as well as the bulk density showed that seabuckthorns had advantages as the species for land reclamation of this dump; Compared with the seabuckthorn, the pure poplar forest had lower contents of SOC and TN respectively by 35.64% and 32.14% and displayed a 16.79% higher value of soil bulk density; (3) The activities of alkaline phosphotase under different types of vegetation rehabilitation had little variation. But soil urease activities was more sensitive to reflect the effects of vegetation restoration on soil properties; (4) Elevation of the SOC and TN turned out to be the main cause for soil fertility restoration and increased biological activities of the dump.

  19. [Heidaigou Opencast Coal Mine: Soil Enzyme Activities and Soil Physical and Chemical Properties Under Different Vegetation Restoration].

    PubMed

    Fang, Ying; Ma, Ren-tian; An, Shao-shan; Zhao, Jun-feng; Xiao, Li

    2016-03-15

    Choosing the soils under different vegetation recovery of Heidaigou dump as the research objects, we mainly analyzed their basic physical and chemical properties and enzyme activities with the method of Analysis of Variance as well as their relations using Pearson correlation analysis and path analysis hoping to uncover the driving factors of the differences between soil enzyme activities under different vegetation restoration, and provide scientific suggestions for the plant selection as well as make a better evaluation to the reclamation effect. The results showed that: (1) Although the artificial vegetation restoration improved the basic physical and chemical properties of the soils while increasing their enzyme activities to a certain extent, the soil conditions still did not reach the level of the natural grassland; (2) Contents of soil organic carbon (SOC) and soil total nitrogen (TN) of the seabuckthorns were the nearest to those of the grassland, which reached 54. 22% and 70. 00% of those of the grassland. In addition, the soil bulk density of the seabuckthorns stand was 17. 09% lower than the maximum value of the amorpha fruitcosa land. The SOC and TN contents as well as the bulk density showed that seabuckthorns had advantages as the species for land reclamation of this dump; Compared with the seabuckthorn, the pure poplar forest had lower contents of SOC and TN respectively by 35.64% and 32.14% and displayed a 16.79% higher value of soil bulk density; (3) The activities of alkaline phosphotase under different types of vegetation rehabilitation had little variation. But soil urease activities was more sensitive to reflect the effects of vegetation restoration on soil properties; (4) Elevation of the SOC and TN turned out to be the main cause for soil fertility restoration and increased biological activities of the dump. PMID:27337909

  20. Microwave Dielectric Properties of Soil and Vegetation and Their Estimation From Spaceborne Radar

    NASA Technical Reports Server (NTRS)

    Dobson, M. Craig; McDonald, Kyle C.

    1996-01-01

    This paper is largely tutorial in nature and provides an overview of the microwave dielectric properties of certain natural terrestrial media (soils and vegetation) and recent results in estimating these properties remotely from airborne and orbital synthetic aperture radar (SAR).

  1. Ecological optimality in water-limited natural soil-vegetation systems. II - Tests and applications

    NASA Technical Reports Server (NTRS)

    Eagleson, P. S.; Tellers, T. E.

    1982-01-01

    The long-term optimal climatic climax soil-vegetation system is defined for several climates according to previous hypotheses in terms of two free parameters, effective porosity and plant water use coefficient. The free parameters are chosen by matching the predicted and observed average annual water yield. The resulting climax soil and vegetation properties are tested by comparison with independent observations of canopy density and average annual surface runoff. The climax properties are shown also to satisfy a previous hypothesis for short-term optimization of canopy density and water use coefficient. Using these hypotheses, a relationship between average evapotranspiration and optimum vegetation canopy density is derived and is compared with additional field observations. An algorithm is suggested by which the climax soil and vegetation properties can be calculated given only the climate parameters and the soil effective porosity. Sensitivity of the climax properties to the effective porosity is explored.

  2. [Characteristics of soil microbial community under different vegetation types in Wuyishan National Nature Reserve, East China].

    PubMed

    Wu, Ze-yan; Lin, Wen-xiong; Chen, Zhi-fang; Fang, Chang-xun; Zhang, Zhi-xing; Wu, Lin-kun; Zhou, Ming-ming; Shen, Li-hua

    2013-08-01

    By using Biolog Ecoplate system, this paper studied the structure and functional diversity of soil microbial community under different vegetation types in Wuyishan National Nature Reserve, aimed to probe into the effects of vegetation type on the diversity of soil microbial community. The results showed that the soil chemical properties, soil enzyme activities, and average well color development (AWCD) were higher in natural forest than in planted forest, and were the lowest in abandoned field. The AWCD reflecting soil microbial activity and functional diversity was increased with increasing incubation time, but there existed significant differences among different vegetation types. The carbon sources mostly used by soil microbes were carbohydrates and carboxylic acids, followed by amino acids, phenolic acids and polymers, and amines had the lowest utilization rate. The Simpson index, Shannon index, Richness index and McIntosh index in natural forest were holistically higher than those in planted forest. Principal component analysis (PCA) identified 2 principal component factors in relation to carbon sources, explaining 56.3% and 30.2% of the variation, respectively. The carbon sources used by soil microbial community differed with vegetation types. Amino acids and amides were the two main carbon sources separating the 2 principal component factors. The results of this study could provide basis for further approaching the relationships between vegetation diversity and soil microbial community diversity.

  3. 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)

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

    2011-12-01

    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

  4. Importance of Soil Moisture and Vegetation Cover for Energy Balance partition in Burkina Faso

    NASA Astrophysics Data System (ADS)

    Ceperley, N. C.; Mande, T.; Tyler, S. W.; Bou-Zeid, E.; Van De Giesen, N.; Parlange, M. B.

    2015-12-01

    Land surface characteristics are the main control on hydrologic processes, the driver of most livelihoods, in semi arid West Africa. We use the energy and water balance measured with two eddy-covariance towers, coupled with a dense network of small, wireless meteorological stations in a small (3.5 km2) catchment to understand these relationships. Time series of monthly averages of soil moisture, rainfall, air temperature, cloud cover, components of net radiation, wind speed, and NDVI are presented in relation to the evaporative fraction and energy balance. We found that both latent and sensible heat fluxes are greater over mixed forest and savanna areas compared agricultural land. Sensible heat is found to be most different between the two land-covers at the end of the year, when the grass and vegetation is dry, and latent heat is found to be most different at the beginning of the year, when bare ground dominates. Further examination shows that soil moisture and vegetation indexes provide the main controls on evaporative fraction. These findings have implications for modeling the evaporation over large regions based on remotely sensed land surface temperature. The site is characteristic of the contrasts in vegetation and moisture availability present in the rocky escarpments found in Northern Benin and Southeastern Burkina Faso. Historically these sites are important in location for village choice and land use designation. These findings reinforce local cultural beliefs of the importance of vegetation for climate regulation and may provide support to local farmers for improving the resilience of natural resources and livelihood security.

  5. Irrigation Requirement Estimation Using Vegetation Indices and Inverse Biophysical Modeling

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

    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.

  6. Trampling resistance of tropical rainforest soils and vegetation in the wet tropics of north east Australia.

    PubMed

    Talbot, L M; Turton, S M; Graham, A W

    2003-09-01

    Controlled trampling was conducted to investigate the trampling resistance of contrasting high fertility basaltic and low fertility rhyolitic soils and their associated highland tropical rainforest vegetation in north east Australia's Wet Tropics. Although this approach has been taken in numerous studies of trampling in a variety of ecosystem types (temperate and subtropical forest, alpine shrubland, coral reef and seagrass beds), the experimental method does not appear to have been previously applied in a tropical rainforest context. Ground vegetation cover and soil penetration resistance demonstrated variable responses to trampling. Trampling, most noticeably after 200 and 500 passes reduced organic litter cover. Bulk density increased with trampling intensity, particularly on basalt soils as rhyolite soils appeared somewhat resistant to the impacts of trampling. The permeability of the basalt and rhyolite soils decreased markedly with increased trampling intensity, even after only 75 passes. These findings suggest physical and hydrological changes may occur rapidly in tropical rainforest soils following low levels of trampling, particularly on basalt soils.

  7. Storage of atmospheric carbon in global litter and soil pools in response to vegetation change and biomass allocation

    SciTech Connect

    Klooster, S.A.; Potter, C.S.

    1995-06-01

    Changes in the distribution of vegetation types under altered climate regimes could have important consequences for the storage of stems. Because there are relatively few definitive field studies of changes in whole ecosystem carbon process-level models driven by gridded global databases may provide reasonable indicators of to changes in vegetation cover. We have used plant litter quality (lignin content) and carbon allocation to woody tissues as surrogates for testing the hypothetical effects of future vegetation change using the CASA (Carnegie-Ames-Stanford Approach) Biosphere model. The model is driven by global gridded (1{degree}) satellite imagery on a monthly time interval to simulate seasonal patterns in net ecosystem carbon balance and steady-state carbon storage in detritus arid soils. Sensitivity tests treated litter quality and allocation effects independently from other direct effects of changes in climate, atmospheric CO{sub 2} levels, and primary production. Results support the hypothesis that soil C storage in today`s temperate and boreal forest life zones are those most sensitive to changes in litter lignin content which may accompany increased climate stress. For these systems, the model predicts that a 50% increase in litter lignin concentration would result in a long-term net gain of about 10% C from the atmosphere into surface litter and soil organic matter pools. A 50% decrease in C allocation to woody tissues would invoke a net loss of 10% C from litter and soil organic matter pools.

  8. [Soil infiltration capacity under different vegetations in southern Ningxia Loess hilly region].

    PubMed

    Yang, Yong-Hui; Zhao, Shi-Wei; Lei, Ting-Wu; Liu, Han

    2008-05-01

    A new apparatus for measuring the run off-on-out under simulated rainfall conditions was used to study the soil infiltration capacity under different rainfall intensities and vegetations in loess hilly region of southern Ningxia, with the relationships between soil water-stable aggregate content and soil stable infiltration rate under different vegetations analyzed. The results showed that the regression equations between rainfall duration and soil infiltration rate under different vegetations all followed y = a + be(-cx), with R2 ranged from 0.9678 to 0.9969. With the increase of rainfall intensity, the soil stable infiltration rate on slope cropland decreased, while that on Medicago lupulina land, natural grassland, and Caragana korshinskii land increased. Under the rainfall intensity of 20 mm h(-1), the rainfall infiltration translation rate (RITR) was decreased in the order of M. lupulina land > slope cropland > natural grassland > C. korshinskii land; while under the rainfall intensity of 40 mm h(-1) and 56 mm h(-1), the RITR was in the sequence of M. lupulina land > natural grassland > slope cropland > C. korshinskii land, and decreased with increasing rainfall intensity. After the reversion of cropland to grassland and forest land, and with the increase of re-vegetation, the amount of >0.25 mm soil aggregates increased, and soil infiltration capacity improved. The revegetation in study area effectively improved soil structure and soil infiltration capacity, and enhanced the utilization potential of rainfall on slope.

  9. Spatial variability of the properties of marsh soils and their impact on vegetation

    NASA Astrophysics Data System (ADS)

    Sidorova, V. A.; Svyatova, E. N.; Tseits, M. A.

    2015-03-01

    Spatial variability of the properties of soils and the character of vegetation was studied on seacoasts of the Velikii Island in the Kandalaksha Bay of the White Sea. It was found that the chemical and physicochemical properties of marsh soils (Tidalic Fluvisols) are largely dictated by the distance from the sea and elevation of the sampling point above sea level. The spatial distribution of the soil properties is described by a quadratic trend surface. With an increase in the distance from the sea, the concentration of ions in the soil solution decreases, and the organic carbon content and soil acidity become higher. The spatial dependence of the degree of variability in the soil properties is moderate. Regular changes in the soil properties along the sea-land gradient are accompanied by the presence of specific spatial patterns related to the system of temporary water streams, huge boulders, and beached heaps of sea algae and wood debris. The cluster analysis made it possible to distinguish between five soil classes corresponding to the following plant communities: barren surface (no permanent vegetation), clayey-sandy littoral with sparse halophytes, marsh with large rhizomatous grasses, and grass-forb-bunchberry vegetation of forest margins. The subdivision into classes is especially distinct with respect to the concentration of chloride ions. The following groups of factors affect the distribution of vegetation: the composition of the soil solution, the height above sea level, the pH of water suspensions, and the humus content.

  10. Multi-discipline resource inventory of soils, vegetation and geology

    NASA Technical Reports Server (NTRS)

    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

    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).

  11. Temporal variations in soil moisture for three typical vegetation types in inner Mongolia, northern China.

    PubMed

    Zheng, Hao; Gao, Jixi; Teng, Yanguo; Feng, Chaoyang; Tian, Meirong

    2015-01-01

    Drought and shortages of soil water are becoming extremely severe due to global climate change. A better understanding of the relationship between vegetation type and soil-moisture conditions is crucial for conserving soil water in forests and for maintaining a favorable hydrological balance in semiarid areas, such as the Saihanwula National Nature Reserve in Inner Mongolia, China. We investigated the temporal dynamics of soil moisture in this reserve to a depth of 40 cm under three types of vegetation during a period of rainwater recharge. Rainwater from most rainfalls recharged the soil water poorly below 40 cm, and the rainfall threshold for increasing the moisture content of surface soil for the three vegetations was in the order: artificial Larix spp. (AL) > Quercus mongolica (QM) > unused grassland (UG). QM had the highest mean soil moisture content (21.13%) during the monitoring period, followed by UG (16.52%) and AL (14.55%); and the lowest coefficient of variation (CV 9.6-12.5%), followed by UG (CV 10.9-18.7%) and AL (CV 13.9-21.0%). QM soil had a higher nutrient content and higher soil porosities, which were likely responsible for the higher ability of this cover to retain soil water. The relatively smaller QM trees were able to maintain soil moisture better in the study area. PMID:25781333

  12. Temporal variations in soil moisture for three typical vegetation types in inner Mongolia, northern China.

    PubMed

    Zheng, Hao; Gao, Jixi; Teng, Yanguo; Feng, Chaoyang; Tian, Meirong

    2015-01-01

    Drought and shortages of soil water are becoming extremely severe due to global climate change. A better understanding of the relationship between vegetation type and soil-moisture conditions is crucial for conserving soil water in forests and for maintaining a favorable hydrological balance in semiarid areas, such as the Saihanwula National Nature Reserve in Inner Mongolia, China. We investigated the temporal dynamics of soil moisture in this reserve to a depth of 40 cm under three types of vegetation during a period of rainwater recharge. Rainwater from most rainfalls recharged the soil water poorly below 40 cm, and the rainfall threshold for increasing the moisture content of surface soil for the three vegetations was in the order: artificial Larix spp. (AL) > Quercus mongolica (QM) > unused grassland (UG). QM had the highest mean soil moisture content (21.13%) during the monitoring period, followed by UG (16.52%) and AL (14.55%); and the lowest coefficient of variation (CV 9.6-12.5%), followed by UG (CV 10.9-18.7%) and AL (CV 13.9-21.0%). QM soil had a higher nutrient content and higher soil porosities, which were likely responsible for the higher ability of this cover to retain soil water. The relatively smaller QM trees were able to maintain soil moisture better in the study area.

  13. Temporal Variations in Soil Moisture for Three Typical Vegetation Types in Inner Mongolia, Northern China

    PubMed Central

    Zheng, Hao; Gao, Jixi; Teng, Yanguo; Feng, Chaoyang; Tian, Meirong

    2015-01-01

    Drought and shortages of soil water are becoming extremely severe due to global climate change. A better understanding of the relationship between vegetation type and soil-moisture conditions is crucial for conserving soil water in forests and for maintaining a favorable hydrological balance in semiarid areas, such as the Saihanwula National Nature Reserve in Inner Mongolia, China. We investigated the temporal dynamics of soil moisture in this reserve to a depth of 40 cm under three types of vegetation during a period of rainwater recharge. Rainwater from most rainfalls recharged the soil water poorly below 40 cm, and the rainfall threshold for increasing the moisture content of surface soil for the three vegetations was in the order: artificial Larix spp. (AL) > Quercus mongolica (QM) > unused grassland (UG). QM had the highest mean soil moisture content (21.13%) during the monitoring period, followed by UG (16.52%) and AL (14.55%); and the lowest coefficient of variation (CV 9.6-12.5%), followed by UG (CV 10.9-18.7%) and AL (CV 13.9-21.0%). QM soil had a higher nutrient content and higher soil porosities, which were likely responsible for the higher ability of this cover to retain soil water. The relatively smaller QM trees were able to maintain soil moisture better in the study area. PMID:25781333

  14. Simulation of vegetation, soil characteristics, and topography effects on soil water distribution and streamflow timing over a semi-arid mountain catchment

    NASA Astrophysics Data System (ADS)

    Grant, L. E.; Seyfried, M. S.; Marks, D.; Winstral, A.

    2004-12-01

    Soil water (θ , m3m-3) and soil characteristics act as intermediaries, along with plants and climate, modifying and modulating streamflow timing and quantity-the majority in the intermountain US west resulting from spring-melt events of accumulated winter snow. The antecedent soil water conditions also predispose different patterns and dynamic responses, especially in semiarid, mountain regions. The context of soil water, analyzed using modeling, is necessary to describe the processes of soil water dynamics. In this research, two years of neutron probe soil water data from a small, semiarid mountain catchment were evaluated using a vertical flow, combined snowmelt-soil water, capacitance-parameter model with available snowmelt data and climate data as driving inputs. Model parameters were vegetation characteristics and soil properties. Results at the point scale show good fit at many locations while a few have poor simulation results at depth. The discrepancies are hypothesized to be due to lack of understanding of parameters such as rooting depth of trees; heterogeneity of parameters within the soil layers; using capacitance parameters that treat some variables as constants; exclusion of lateral flow processes that must occur in some locations due to basin geometry and nature of soil-fractured bedrock interface; and rising water table effects that can be seen in the gleying of clayey soils near drainage lines. Driving parameters were then distributed over the 0.36 km2 catchment using the regional 10 m DEM, soil maps, remotely sensed color-infrared imagery, and the spatiotemporal distributions of soil water from previous research. The model was run discretely at each pixel. Results matched point data simulations well. Simulated throughflow, totaled over the watershed, compared well with weir measured streamflow in timing and quantity indicating accurate representation of parameters over the watershed, proper calibration, and well described processes.

  15. Role of vegetation in modulating rainfall interception and soil water flux in ecosystems under transition from grassland to woodland

    NASA Astrophysics Data System (ADS)

    Zou, Chris; Will, Rodney; Stebler, Elaine; Qiao, Lei

    2014-05-01

    Vegetation exerts strong control on the hydrological budget by shielding the soil from rainfall through interception and modulating water transmission in the soil by altering soil properties and rooting zone water extraction. Therefore, a change in vegetation alters the water cycle by a combination of a passive, rainfall redistribution mechanism controlled by the physical dimensions of vegetation and active, water extracting processes resulting from physiological attributes of different plants. As a result, the role of vegetation on the water cycle is likely to change where vegetation is under transition such as in the southern Great Plains of USA due to woody plant encroachment. However, it remains largely unknown how this physiognomic transformation from herbaceous cover to woody canopy alters rainfall influx, soil water transmission and efflux from the soil profile and consequently alters historic patterns of runoff and groundwater recharge. This knowledge is critical for both water resource and ecosystem management. We conducted a comprehensive, 5-year study involving direct quantification of throughfall and stemflow for grassland and encroached juniper woodland (Juniperus virginiana), water efflux through transpiration using an improved Granier thermal dissipation method (trees) and ET chamber (grassland), soil moisture storage and dynamics (capacitance probe) and streamflow (small catchment). We calibrated a prevailing hydrological model (SWAT) based on observed data to simulate potential change in runoff and recharge for the Cimarron River basin (study site located within this basin) under various phases of grassland to woodland transition. Our results show that juniper encroachment reduces throughfall reaching the soil surface compared with grassland under moderate grazing. The evergreen junipers transpired water year-round including fall and winter when the warm season grasses were senescent. As a result, soil water content and soil water storage on the

  16. Occurrence of nonylphenol and nonylphenol monoethoxylate in soil and vegetables from vegetable farms in the Pearl River Delta, South China.

    PubMed

    Cai, Quan-Ying; Huang, Hui-Juan; Lü, Huixiong; Mo, Ce-Hui; Zhang, Jun; Zeng, Qiao-Yun; Tian, Jun-Jian; Li, Yan-Wen; Wu, Xiao-Lian

    2012-07-01

    Low molecular-mass nonylphenol ethoxylates (NPEOs) and 4-nonylphenol (NP) are biodegradation products of higher molecular mass NPEOs used as surface active agents, and they are endocrine-disrupting contaminants. In this study, surface soil (0-20 cm) samples and different vegetable samples were collected from 27 representative vegetable farms located in Shenzhen, Dongguan, and Huizhou within the Pearl River Delta region, South China, and NP and nonylphenol monoethoxylate (NP(1)EO) were analyzed using high-performance liquid chromatography with ultraviolet detection. The results show that NP and NP(1)EO were detected in soil and vegetable samples. The concentrations of NP and NP(1)EO in soil samples ranged from nondetectable (ND) to 7.22 μg kg(-1) dry weight (dw) and from ND to 8.24 μg kg(-1) dw, respectively. The average concentrations of both NP and NP(1)EO in soil samples decreased in the following order: Dongguan > Huizhou > Shenzhen. The levels of NP and NP(1)EO in vegetable samples varied from 1.11 to 4.73 μg kg(-1) dw and from 1.32 to 5.33 μg kg(-1) dw, respectively. The greatest levels of both NP and NP(1)EO were observed in water spinach, and the lowest levels of NP and NP(1)EO were recorded in cowpea. The bioconcentration factors (the ratio of contaminant concentration in plant tissue to soil concentration) of NP and NP(1)EO were <1.0 (mean 0.535 and 0.550, respectively). The occurrences of NP and NP(1)EO in this study are compared with other studies, and their potential sources are discussed. PMID:22203462

  17. Modeling Vernal Pool Hydrology and Vegetation in the Sierra Nevadas

    NASA Astrophysics Data System (ADS)

    Montrone, A. K.; Saito, L.; Weisberg, P.; Gosejohan, M.

    2012-12-01

    Vernal pools are geographic depressions with relatively impermeable substrates that are subject to four distinct seasons in mountainous regions: they fill with snow in the winter, melt into inundated pools in the spring, become unsaturated and vegetated by summer, then dry and become fully desiccated by fall. Vernal pools in California are greatly threatened. Over 90% of the pools in California have been destroyed by urbanization and other land use changes and continue to disappear with population growth. Furthermore, these pools face threats posed by climate change due to altered precipitation and temperature regimes. In the context of anthropogenic climate change, we are evaluating the direct and indirect effects of grazing management on ecohydrology and plant community structure in vernal pools Northern Sierra Nevada mountains. Hydrologic models of vernal pool basins, driven by climatic variables, are used to 1) determine if a changing climate will alter the magnitude and spatial distribution of inundation period within the pools; 2) determine how the available habitat for vernal pool vegetation specialists will change with climate change; 3) determine if increased soil compaction due to cattle grazing can help mitigate effects of climate change resulting from changes in hydraulic conductivity; and 4) determine the importance of spatial resolution in constructing the physical representation of the pools within the hydrologic models. Preliminary results from the models including calibration error metrics and hydroperiod impacts of grazing for models with varying spatial complexity will be presented.

  18. Modelling Soil respiration in agro-ecosystems

    NASA Astrophysics Data System (ADS)

    Delogu, Emilie; LeDantec, Valerie; Mordelet, Patrick; Buysse, Pauline; Aubinet, Marc; Pattey, Elizabeth

    2013-04-01

    soil respiration exchange. These NEE data were used to validate the model. The carbon pools in the model needed to be initialized at each site, by running iteratively simulations of a same climatic year in a given wheat field, until equilibrium was reached. The model performance was evaluated by comparing simulated and measured soil respiration values. The predicted heterotrophic soil respiration compared well with the seasonal dynamic fluxes at each site. The measured values of heterotrophic soil respiration were also well calculated by the model. Then, the autotrophic soil respiration was validated. The parameterization of the Root/Shoot ratio dynamic was a key factor to retrieve the seasonal dynamic of observed root+rhizosphere respiration during vegetation growth period. Finally, the total soil respiration model was validated on independent datasets from calibration, of four wheat crops and could be used as a prediction model for comparison between different scenario of irrigation, ploughing, or crop rotation.

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

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    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 (σ 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

  1. How can effect the synergy of climate change, soil units and vegetation groups the potential global distribution of plants up to 2300: a modelling study for prediction of potential global distribution and migration of the N2 fixing species Alnus spp.

    NASA Astrophysics Data System (ADS)

    Sakalli, A.

    2015-01-01

    Plant migration is a well known adaptation strategy of plant groups or species with evidence from historical to present observation and monitoring studies. Importance of N2-fixing plants has increased in last decades. Alnus (alder) is an important plant group because of its nitrogen fixation ability. Alders are generally distributed in humid locations of boreal, temperate and tropical climate zones, where the nitrogen fixation is an important nitrogen source for other plants. To model the nitrogen fixation by alder, data about the global distribution of alder is absolutely required. In this study a new method and model are presented to predict the distribution of N2-fixing genus on global scale and its migration in the future by using climate change scenarios. Three linear functions were defined for the determination of climate niche of alders. The distribution and migration model (Alnus-Distribution-Model (ADM)) was improved with the aid of the soil units from FAO-Unesco Soil Database, and vegetation types from Schmithüsen's biogeographical atlas. The model was also developed to predict the impact of climate change on alder distribution by using climate data from experiments performed by the Community Climate System Model version 4 (CCSM4) including the representative concentration pathways (RCPs) mitigation scenarios, and extensions of the scenarios beyond 2100 to 2300. The model covered basic approaches to understand the combine effect of climate, soil and vegetation on plant distribution and migration in the current time and future.

  2. Effect of vegetation on rock and soil type discrimination

    NASA Technical Reports Server (NTRS)

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

    1977-01-01

    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.

  3. Petroleum contamination of soil and water, and their effects on vegetables by statistically analyzing entire data set.

    PubMed

    Zhang, Juan; Fan, Shu-kai; Yang, Jun-cheng; Du, Xiao-ming; Li, Fa-sheng; Hou, Hong

    2014-04-01

    Aliphatic hydrocarbons have been used to assess total oil concentrations, petroleum sources, and petroleum degradation. In this study, surface soil, groundwater, surface water, and vegetables were collected from the outskirts of Xi'an, the largest city in northwestern China, and the samples were analyzed for aliphatic hydrocarbon contents. The concentrations of n-alkanes were 1.06-4.01 μg/g in the soil. The concentrations and the geochemical characteristics of n-alkanes showed that the low carbon number hydrocarbons were mainly from petroleum sources, whereas the high carbon number hydrocarbons received more hydrocarbons from herbaceous plants. The concentrations of n-alkanes were 9.20-93.44 μg/L and 23.74-118.27 μg/L in the groundwater and the surface water, respectively. The water had characteristics of petroleum and submerged/floating macrophytes and was found in concentrations that would cause chronic disruption of sensitive organisms. The concentrations and geochemical characteristics of n-alkanes in Brassica chinensis L. and Apium graveolens were different, but both were contaminated by petroleum hydrocarbons. The results from principal component analysis (PCA) indicated that the sorption of n-alkanes to soil particles could not be described by linear models. The distributions of n-alkanes in vegetables were positively correlated with those in soil, and the correlation coefficient was up to 0.9310 using the constructed vectors. Therefore, the researchers should pay close attention to the effect of soil contamination on vegetables.

  4. Application of a coupled vegetation competition and groundwater simulation model to study effects of sea level rise and storm surges on coastal vegetation

    USGS Publications Warehouse

    Teh, Su Yean; Turtora, Michael; DeAngelis, Don; Jiang Jiang,; Pearlstine, Leonard G.; Smith, Thomas; Koh, Hock Lye

    2015-01-01

    Global climate change poses challenges to areas such as low-lying coastal zones, where sea level rise (SLR) and storm-surge overwash events can have long-term effects on vegetation and on soil and groundwater salinities, posing risks of habitat loss critical to native species. An early warning system is urgently needed to predict and prepare for the consequences of these climate-related impacts on both the short-term dynamics of salinity in the soil and groundwater and the long-term effects on vegetation. For this purpose, the U.S. Geological Survey’s spatially explicit model of vegetation community dynamics along coastal salinity gradients (MANHAM) is integrated into the USGS groundwater model (SUTRA) to create a coupled hydrology–salinity–vegetation model, MANTRA. In MANTRA, the uptake of water by plants is modeled as a fluid mass sink term. Groundwater salinity, water saturation and vegetation biomass determine the water available for plant transpiration. Formulations and assumptions used in the coupled model are presented. MANTRA is calibrated with salinity data and vegetation pattern for a coastal area of Florida Everglades vulnerable to storm surges. A possible regime shift at that site is investigated by simulating the vegetation responses to climate variability and disturbances, including SLR and storm surges based on empirical information.

  5. Modeling the Impact of Vegetation Structure on Canopy Radiative Transfer for a Global Vegetation Dynamic Model

    NASA Astrophysics Data System (ADS)

    Ni-Meister, W.; Kiang, N.; Yang, W.

    2007-12-01

    The transmission of light through plant canopies results in vertical profiles of light intensity that affect the photosynthetic activity and gas exchange of plants, their competition for light, and the canopy energy balance. The accurate representation of the canopy light profile is then important for predicting ecological dynamics. The study presents a simple canopy radiative transfer scheme to characterize the impact of the horizontal and vertical vegetation structure heterogeneity on light profiles. Actual vertical foliage profile and a clumping factor which are functions of tree geometry, size and density and foliage density are used to characterize the vertical and horizontal vegetation structure heterogeneity. The simple scheme is evaluated using the ground and airborne lidar data collected in deciduous and coniferous forests and was also compared with the more complex Geometric Optical and Radiative Transfer (GORT) model and the two-stream scheme currently being used to describe light interactions with vegetation canopy in most GCMs. The simple modeled PAR profiles match well with the ground data, lidar and full GORT model prediction, it performs much better than the simple Beer's&plaw used in two stream scheme. This scheme will have the same computation cost as the current scheme being used in GCMs, but provides better photosynthesis, radiative fluxes and surface albedo estimates, thus is suitable for a global vegetation dynamic model embedded in GCMs.

  6. The impact of Precipitation and Grassland Vegetation on Soil Moisture Dynamics

    NASA Astrophysics Data System (ADS)

    Salve, R.; Sudderth, E. A.; St. Clair, S. B.; Torn, M. S.

    2009-12-01

    The primary objective of this study was to assess the impact of grassland vegetation and precipitation (defined by the temporal pattern of water deposition and cumulative rainfall) on near-surface hydrology. Using a randomized block design experiment in a greenhouse, we monitored soil-moisture dynamics in mesocosms planted with three types of grassland vegetation found in California (mixed California grassland, avena grass monoculture, and erodium forb monoculture). We observed that above ground biomass production was strongly influenced by rainfall amount, with most productivity in the mid-level rainfall treatment. Soil moisture content (SMC) was best predicted by rainfall, stage of plant growth, and the interaction between these two parameters. Surprisingly, SMC did not depend on species composition of the grassland. The role of ET in drying the soil was influenced by the interaction between growth stage and rainfall, and to a lesser extend by the interaction between vegetation type and growth stage. When combined, seasonal precipitation and vegetation influenced the near-surface hydrology in ways that cannot be predicted from manipulation of a single variable. These results emphasize the importance of the interactive effects of precipitation and vegetation on soil moisture dynamics, and the potential for feedbacks since soil moisture affects vegetation. This study was supported by the Program for Ecosystem Research, Office of Science, U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

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

    NASA Technical Reports Server (NTRS)

    Wang, J. R.

    1985-01-01

    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.

  8. Soil moisture inferences from thermal infrared measurements of vegetation temperatures

    NASA Technical Reports Server (NTRS)

    Jackson, R. D. (Principal Investigator)

    1981-01-01

    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.

  9. [Characteristics of soil pH and exchangeable acidity in red soil profile under different vegetation types].

    PubMed

    Ji, Gang; Xu, Ming-gang; Wen, Shi-lin; Wang, Bo-ren; Zhang, Lu; Liu, Li-sheng

    2015-09-01

    The characteristics of soil pH and exchangeable acidity in soil profile under different vegetation types were studied in hilly red soil regions of southern Hunan Province, China. The soil samples from red soil profiles within 0-100 cm depth at fertilized plots and unfertilized plots were collected and analyzed to understand the profile distribution of soil pH and exchangeable acidity. The results showed that, pH in 0-60 cm soil from the fertilized plots decreased as the following sequence: citrus orchard > Arachis hypogaea field > tea garden. As for exchangeable acidity content, the sequence was A. hypogaea field ≤ citrus orchard < tea garden. After tea tree and A. hypogaea were planted for long time, acidification occurred in surface soil (0-40 cm), compared with the deep soil (60-100 cm), and soil pH decreased by 0.55 and 0.17 respectively, but such changes did not occur in citrus orchard. Soil pH in 0-40 cm soil from the natural recovery vegetation unfertilized plots decreased as the following sequence: Imperata cylindrica land > Castanea mollissima garden > Pinus elliottii forest ≥ Loropetalum chinensis forest. As for exchangeable acidity content, the sequence was L cylindrica land < C. mollissima garden < L. chinensis forest ≤ P. elliottii forest. Soil pH in surface soil (0-20 cm) from natural forest plots, secondary forest and Camellia oleifera forest were significantly lower than that from P. massoniana forest, decreased by 0.34 and 0.20 respectively. For exchangeable acidity content in 0-20 cm soil from natural forest plot, P. massoniana forest and secondary forest were significantly lower than C. oleifera forest. Compared with bare land, surface soil acidification in unfertilized plots except I. cylindrica land had been accelerated, and the natural secondary forest was the most serious among them, with surface soil pH decreasing by 0.52. However, the pH increased in deep soils from unfertilized plots except natural secondary forest, and I. cylindrica

  10. [Characteristics of soil pH and exchangeable acidity in red soil profile under different vegetation types].

    PubMed

    Ji, Gang; Xu, Ming-gang; Wen, Shi-lin; Wang, Bo-ren; Zhang, Lu; Liu, Li-sheng

    2015-09-01

    The characteristics of soil pH and exchangeable acidity in soil profile under different vegetation types were studied in hilly red soil regions of southern Hunan Province, China. The soil samples from red soil profiles within 0-100 cm depth at fertilized plots and unfertilized plots were collected and analyzed to understand the profile distribution of soil pH and exchangeable acidity. The results showed that, pH in 0-60 cm soil from the fertilized plots decreased as the following sequence: citrus orchard > Arachis hypogaea field > tea garden. As for exchangeable acidity content, the sequence was A. hypogaea field ≤ citrus orchard < tea garden. After tea tree and A. hypogaea were planted for long time, acidification occurred in surface soil (0-40 cm), compared with the deep soil (60-100 cm), and soil pH decreased by 0.55 and 0.17 respectively, but such changes did not occur in citrus orchard. Soil pH in 0-40 cm soil from the natural recovery vegetation unfertilized plots decreased as the following sequence: Imperata cylindrica land > Castanea mollissima garden > Pinus elliottii forest ≥ Loropetalum chinensis forest. As for exchangeable acidity content, the sequence was L cylindrica land < C. mollissima garden < L. chinensis forest ≤ P. elliottii forest. Soil pH in surface soil (0-20 cm) from natural forest plots, secondary forest and Camellia oleifera forest were significantly lower than that from P. massoniana forest, decreased by 0.34 and 0.20 respectively. For exchangeable acidity content in 0-20 cm soil from natural forest plot, P. massoniana forest and secondary forest were significantly lower than C. oleifera forest. Compared with bare land, surface soil acidification in unfertilized plots except I. cylindrica land had been accelerated, and the natural secondary forest was the most serious among them, with surface soil pH decreasing by 0.52. However, the pH increased in deep soils from unfertilized plots except natural secondary forest, and I. cylindrica

  11. Application of vegetable oils in the treatment of polycyclic aromatic hydrocarbons-contaminated soils.

    PubMed

    Yap, C L; Gan, S; Ng, H K

    2010-05-15

    A brief review is conducted on the application of vegetable oils in the treatment of PAH-contaminated soils. Three main scopes of treatment strategies are discussed in this work including soil washing by oil, integrated oil-biological treatment and integrated oil-non-biological treatment. For each of these, the arguments supporting vegetable oil application, the applied treatment techniques and their efficiencies, associated factors, as well as the feasibility of the techniques are detailed. Additionally, oil regeneration, the environmental impacts of oil residues in soil and comparison with other commonly employed techniques are also discussed.

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

    NASA Technical Reports Server (NTRS)

    Wiegand, C. L.; Richardson, A. J. (Principal Investigator)

    1982-01-01

    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 MSS 5 and MSS 6) 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.

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

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

    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

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

    PubMed

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

    2012-11-01

    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.

  15. Soil Erosion Risk Map based on irregularity of the vegetative activity

    NASA Astrophysics Data System (ADS)

    Saa-Requejo, Antonio; Tarquis, Ana Maria; Martín-Sotoca, Juan J.; Valencia, Jose L.; Gobin, Anne; Rodriguez-Sinobas, Leonor

    2016-04-01

    Because of the difficulties to build on both daily rainfall and base shorter time, we explored the possibilities of building indexes based on land cover, which also provide us the opportunity to evaluate their evolution over time. We consider the Fournier index (Fournier, 1960) which is used to assess the rainfall erosivity based on monthly rainfall, alternatively to use of the rainfall intensity in time bases under one hour (eg., van der Knijff et al., 1999; Shamshad et al, 2008). This index can also be interpreted as an index of irregularity and representing a ratio between maximum monthly precipitation and annual rainfall. We propose to calculate this irregularity in terms of irregularity of the vegetative activity. This activity is related to precipitation, but also with the availability of water in the soil reservoir and land use. Therefore, we propose a kind of Fournier index on the effective use of water, which is also closely related to variations in infiltration. Higher is the presence of vegetation higher is the effective use of water. For this "modified Fourier index" we used the NDVI (Normalized Difference Vegetation Index) as index of available vegetative activity, which is widely reported in the literature (Jensen, 2000). Initial calculations have been done with MODIS 500 x 500 m satellite data. The selected area was Cega-Eresma-Adaja subbasin during the period from 2009 to 2012. We selected 8 days composite images product. The calculation of the valid values to eliminate areas with clouds or snow is performed according to the criteria of Martinez Sotoca (2014), ie with a Saturation (based on HSL color model) greater or equal to 0.15. Then, an average of these values was estimated to represent each month of the year. The results are very interesting when we compare Modified Fournier Index on NDVIs with the map of potential soil loss. We have found surprisingly similar patterns and practical equivalence between several classes. Therefore, the Modified

  16. Boron isotopes in soils: investigation of horizon reactivity and vegetation cycling

    NASA Astrophysics Data System (ADS)

    Cividini, D.; Lemarchand, D.; Chabaux, F. J.; Turpault, M.; Viville, D.; Stille, P.; Pierret, M.

    2009-12-01

    Investigating the soil/plant coupling requires the development of specific approaches being unambiguously sensitive to mineral- and biology-derived reactions. Boron presents chemical properties that, a priori, well meet the conditions for tracing bio-geochemical reactions. In particular, it is present in moderate to high concentrations in minerals; it is very sensitive to water/rock interactions during which it is partitioned between solid and liquid phases and undergoes a great isotopic fractionation and, finally, it is an essential nutrient for plants. Here, we present an extensive study on B isotopes in two distinct soil/tree systems from the well-characterized Strengbach basin (http://ohge.u-strasbg.fr/indexuk.html). Both bulk soil samples and granulometric fractions were analyzed. Soil solutions (down to 60 cm depth) were monitored every 6 weeks over two years (2005-2006). Tree samples (spruce needles and beech leaves) punctually sampled during this period. A Mass budget based on B concentration and hydrology model clearly first indicates that trees largely control the distribution of B in soil uppermost layers by yearly mobilizing 4 times more B than it is drained by soil solutions below 60 cm depth. B isotopes in soil solution depth profile highlight the presence of a highly reactive layer a 10 cm depth, which is interpreted as resulting from seasonal chemical oscillations caused by the biology and hydrology cycles. Isotopic budget indicates that this layer is not at steady state and accumulates B over years. The increasing contribution with depth of the weathering-derived B flux is clearly observable by a shift of the δ11B values towards low values. At the soil scale, mass and isotopic budgets help distinguishing both the B fluxes related to the mineral weathering reactions and the vegetation cycling and even show a strong correlation between them. Detailed analyses of granulometric fractions permit the determination of the B-carrier phases in these two

  17. Effects of vegetable oil residue after soil extraction on physical-chemical properties of sandy soil and plant growth.

    PubMed

    Gong, Zongqiang; Li, Peijun; Wilke, B M; Alef, Kassem

    2008-01-01

    Vegetable oil has the ability to extract polycyclic aromatic hydrocarbons (PAHs) from contaminated sandy soil for a remediation purpose, with some of the oil remaining in the soil. Although most of the PAHs were removed, the risk of residue oil in the soil was not known. The objective of this study was to evaluate the effects of the vegetable oil residue on higher plant growth and sandy soil properties after soil extraction for a better understanding of the soil remediation. Addition of sunflower oil and column experiment were performed on a PAH contaminated soil and/or a control soil, respectively. Soils were incubated for 90 d, and soil pH was measured during the soil incubation. Higher plant growth bioassays with Avena sativa L. (oat) and Brassica rapa L. (turnip) were performed after the incubation, and then soil organic carbon contents were measured. The results show that both the nutrient amendment and the sunflower oil degradation resulted in the decrease of soil pH. When these two process worked together, their effects were counteracted due to the consumption of the nutrients and oil removal, resulting in different pH profiles. Growth of A. sativa was adversely affected by the sunflower oil, and the nutrient amendments stimulated the A. sativa growth significantly. B. rapa was more sensitive to the sunflower oil than A. sativa. Only 1% sunflower oil addition plus nutrient amendment stimulated B. rapa growth. All the other treatments on B. rapa inhibited its growth significantly. The degradation of the sunflower oil in the soils was proved by the soil organic carbon content.

  18. Effects of vegetable oil residue after soil extraction on physical-chemical properties of sandy soil and plant growth.

    PubMed

    Gong, Zongqiang; Li, Peijun; Wilke, B M; Alef, Kassem

    2008-01-01

    Vegetable oil has the ability to extract polycyclic aromatic hydrocarbons (PAHs) from contaminated sandy soil for a remediation purpose, with some of the oil remaining in the soil. Although most of the PAHs were removed, the risk of residue oil in the soil was not known. The objective of this study was to evaluate the effects of the vegetable oil residue on higher plant growth and sandy soil properties after soil extraction for a better understanding of the soil remediation. Addition of sunflower oil and column experiment were performed on a PAH contaminated soil and/or a control soil, respectively. Soils were incubated for 90 d, and soil pH was measured during the soil incubation. Higher plant growth bioassays with Avena sativa L. (oat) and Brassica rapa L. (turnip) were performed after the incubation, and then soil organic carbon contents were measured. The results show that both the nutrient amendment and the sunflower oil degradation resulted in the decrease of soil pH. When these two process worked together, their effects were counteracted due to the consumption of the nutrients and oil removal, resulting in different pH profiles. Growth of A. sativa was adversely affected by the sunflower oil, and the nutrient amendments stimulated the A. sativa growth significantly. B. rapa was more sensitive to the sunflower oil than A. sativa. Only 1% sunflower oil addition plus nutrient amendment stimulated B. rapa growth. All the other treatments on B. rapa inhibited its growth significantly. The degradation of the sunflower oil in the soils was proved by the soil organic carbon content. PMID:19209632

  19. [Evaluation and source analysis of the mercury pollution in soils and vegetables around a large-scale zinc smelting plant].

    PubMed

    Liu, Fang; Wang, Shu-Xiao; Wu, Qing-Ru; Lin, Hai

    2013-02-01

    The farming soil and vegetable samples around a large-scale zinc smelter were collected for mercury content analyses, and the single pollution index method with relevant regulations was used to evaluate the pollution status of sampled soils and vegetables. The results indicated that the surface soil and vegetables were polluted with mercury to different extent. Of the soil samples, 78% exceeded the national standard. The mercury concentration in the most severely contaminated area was 29 times higher than the background concentration, reaching the severe pollution degree. The mercury concentration in all vegetable samples exceeded the standard of non-pollution vegetables. Mercury concentration, in the most severely polluted vegetables were 64.5 times of the standard, and averagely the mercury concentration in the vegetable samples was 25.4 times of the standard. For 85% of the vegetable samples, the mercury concentration, of leaves were significantly higher than that of roots, which implies that the mercury in leaves mainly came from the atmosphere. The mercury concentrations in vegetable roots were significantly correlated with that in soils, indicating the mercury in roots was mainly from soil. The mercury emissions from the zinc smelter have obvious impacts on the surrounding soils and vegetables. Key words:zinc smelting; mercury pollution; soil; vegetable; mercury content

  20. Effect of Vegetation Patterns on SAR derived Surface Soil Moisture Distribution

    NASA Astrophysics Data System (ADS)

    Koyama, C. N.; Schneider, K.

    2012-12-01

    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 (α), and the total reflected power (span), all of which are highly affected by the canopy

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

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

    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

  2. Effects of Coal-Bed Methane Discharge Waters on Soils and Vegetation Diversity

    NASA Astrophysics Data System (ADS)

    Stearns, M.; Tindall, J. A.; Friedel, M. J.; Cronin, G.; Berquist, E.

    2004-12-01

    Coal bed methane 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 impacted and reference sites (upland elevations and wetted gully) to investigate impacts of CBM discharge waters on soil physical and chemical properties and on native and introduced vegetation richness and diversity. Results indicate a significant increase of salinity and sodicity within local soil ecosystems at sites directly exposed to CBM discharge waters. Elevated concentrations of sodium in the soil appear to be due to consistent exposure to CBM waters. Clay-loam soils in the study area, which have a much larger specific surface area than the sandy soils, readily allow sodium ions to adsorb quickly to exchange sites. There was no significant relation between increasing water 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 richness was highest at the reference (upland and gully) and impacted upland sites. The impacted gully had the greatest percent composition of introduced vegetation species. Salt-tolerant species had the greatest richness at the impacted gully, implicating a potential threat of invasion and competition to established native vegetation. CBM waters could have detrimental impacts to the local ecosystem, causing dispersion of soils and making it difficult for native vegetation to exist. These waters could also have a devastating effect on agricultural production operations and long-term water quality.

  3. Technique for assessing vegetation-induced moisture flux, with implications for global climate modeling

    NASA Technical Reports Server (NTRS)

    Macari, Emir Jose

    1990-01-01

    The time between storms, the duration of storms, and the storm depths are studied in relation to vegetation controls on the disposition of rainfall. It is proposed that understanding the movement of water between the vegetation and soil (including evapotranspiration and infiltration) will be the gateway for modeling atmospheric flux and improving global climate models. The overall objective goal of the proposed research effort is to develop a field/lab methodology which will provide a better understanding of vegetation induced water movement. Water flow initiated from stem flow of wooded slopes feeds soil water pathways, which in turn feed the deeper ground water system and give rise to stream response. This is balanced by more water inputs via throughfall, where it percolates the soil matrix and allows much greater rates of evapotranspiration and atmospheric/soil moisture flux. This research study seeks to gain an understanding of the effect of vegetation on soil moisture, and the effect of this differential wetting on resulting evapotranspiration and atmospheric flux.

  4. Integrated Field Lysimetry and Porewater Sampling for Evaluation of Chemical Mobility in Soils and Established Vegetation

    PubMed Central

    Gannon, Travis W.; Polizzotto, Matthew L.

    2014-01-01

    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

  5. Climate-vegetation-soil interactions and long-term hydrologic partitioning: signatures of catchment co-evolution

    NASA Astrophysics Data System (ADS)

    Troch, P. A.; Carrillo, G.; Sivapalan, M.; Wagener, T.; Sawicz, K.

    2013-06-01

    Budyko (1974) postulated that long-term catchment water balance is controlled to first order by the available water and energy. This leads to the interesting question of how do landscape characteristics (soils, geology, vegetation) and climate properties (precipitation, potential evaporation, number of wet and dry days) interact at the catchment scale to produce such a simple and predictable outcome of hydrological partitioning? Here we use a physically-based hydrologic model separately parameterized in 12 US catchments across a climate gradient to decouple the impact of climate and landscape properties to gain insight into the role of climate-vegetation-soil interactions in long-term hydrologic partitioning. The 12 catchment models (with different paramterizations) are subjected to the 12 different climate forcings, resulting in 144 10 yr model simulations. The results are analyzed per catchment (one catchment model subjected to 12 climates) and per climate (one climate filtered by 12 different model parameterization), and compared to water balance predictions based on Budyko's hypothesis (E/P = ϕ (Ep/P); E: evaporation, P: precipitation, Ep: potential evaporation). We find significant anti-correlation between average deviations of the evaporation index (E/P) computed per catchment vs. per climate, compared to that predicted by Budyko. Catchments that on average produce more E/P have developed in climates that on average produce less E/P, when compared to Budyko's prediction. Water and energy seasonality could not explain these observations, confirming previous results reported by Potter et al. (2005). Next, we analyze which model (i.e., landscape filter) characteristics explain the catchment's tendency to produce more or less E/P. We find that the time scale that controls subsurface storage release explains the observed trend. This time scale combines several geomorphologic and hydraulic soil properties. Catchments with relatively longer subsurface storage

  6. Climate-vegetation-soil interactions and long-term hydrologic partitioning: Signatures of catchment co-evolution (Invited)

    NASA Astrophysics Data System (ADS)

    Troch, P. A.; Carrillo, G. A.; Sivapalan, M.; Sawicz, K. A.; Wagener, T.

    2013-12-01

    Budyko (1974) postulated that long-term catchment water balance is controlled to first order by the available water and energy. This leads to the interesting question of how do landscape characteristics (soils, geology, vegetation) and climate properties (precipitation, potential evaporation, number of wet and dry days) interact at the catchment scale to produce such a simple and predictable outcome of hydrological partitioning? Here we use a physically-based hydrologic model separately parameterized in 12 US catchments across a climate gradient to decouple the impact of climate and landscape properties to gain insight into the role of climate-vegetation-soil interactions in long-term hydrologic partitioning. The 12 catchment models (with different paramterizations) are subjected to the 12 different climate forcings, resulting in 144 10-year model simulations. The results are analyzed per catchment (one catchment model subjected to 12 climates) and per climate (one climate filtered by 12 different model parameterization), and compared to water balance predictions based on Budyko's hypothesis (E/P=φ(Ep/P); E: evaporation, P: precipitation, Ep: potential evaporation). We find significant anti-correlation between average deviations of the evaporation index (E/P) computed per catchment vs. per climate, compared to that predicted by Budyko. Catchments that on average produce more E/P have developed in climates that on average produce less E/P, when compared to Budyko's prediction. Water and energy seasonality could not explain these observations, confirming previous results reported by Potter et al. (2005). Next, we analyze which model (i.e., landscape filter) characteristics explain the catchment's tendency to produce more or less E/P. We find that the time scale that controls subsurface storage release explains the observed trend. This time scale combines several geomorphologic and hydraulic soil properties. Catchments with relatively longer subsurface storage

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

    PubMed Central

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

    2008-01-01

    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.

  8. Bacterial Community Responses to Soils along a Latitudinal and Vegetation Gradient on the Loess Plateau, China.

    PubMed

    Zeng, Quanchao; Dong, Yanghong; An, Shaoshan

    2016-01-01

    Soil bacterial communities play an important role in nutrient recycling and storage in terrestrial ecosystems. Loess soils are one of the most important soil resources for maintaining the stability of vegetation ecosystems and are mainly distributed in northwest China. Estimating the distributions and affecting factors of soil bacterial communities associated with various types of vegetation will inform our understanding of the effect of vegetation restoration and climate change on these processes. In this study, we collected soil samples from 15 sites from north to south on the Loess Plateau of China that represent different ecosystem types and analyzed the distributions of soil bacterial communities by high-throughput 454 pyrosequencing. The results showed that the 142444 sequences were grouped into 36816 operational taxonomic units (OTUs) based on 97% similarity. The results of the analysis showed that the dominant taxonomic phyla observed in all samples were Actinobacteria, Proteobacteria, Chloroflexi, Acidobacteria and Planctomycetes. Actinobacteria and Proteobacteria were the two most abundant groups in all samples. The relative abundance of Actinobacteria increased from 14.73% to 40.22% as the ecosystem changed from forest to sandy, while the relative abundance of Proteobacteria decreased from 35.35% to 21.40%. Actinobacteria and Proteobacteria had significant correlations with mean annual precipitation (MAP), pH, and soil moisture and nutrients. MAP was significantly correlated with soil chemical and physical properties. The relative abundance of Actinobacteria, Proteobacteria and Planctomycetes correlated significantly with MAP, suggesting that MAP was a key factor that affected the soil bacterial community composition. However, along with the MAP gradient, Chloroflexi, Bacteroidetes and Cyanobacteria had narrow ranges that did not significantly vary with the soil and environmental factors. Overall, we conclude that the edaphic properties and/or vegetation

  9. Bacterial Community Responses to Soils along a Latitudinal and Vegetation Gradient on the Loess Plateau, China

    PubMed Central

    Zeng, Quanchao; Dong, Yanghong; An, Shaoshan

    2016-01-01

    Soil bacterial communities play an important role in nutrient recycling and storage in terrestrial ecosystems. Loess soils are one of the most important soil resources for maintaining the stability of vegetation ecosystems and are mainly distributed in northwest China. Estimating the distributions and affecting factors of soil bacterial communities associated with various types of vegetation will inform our understanding of the effect of vegetation restoration and climate change on these processes. In this study, we collected soil samples from 15 sites from north to south on the Loess Plateau of China that represent different ecosystem types and analyzed the distributions of soil bacterial communities by high-throughput 454 pyrosequencing. The results showed that the 142444 sequences were grouped into 36816 operational taxonomic units (OTUs) based on 97% similarity. The results of the analysis showed that the dominant taxonomic phyla observed in all samples were Actinobacteria, Proteobacteria, Chloroflexi, Acidobacteria and Planctomycetes. Actinobacteria and Proteobacteria were the two most abundant groups in all samples. The relative abundance of Actinobacteria increased from 14.73% to 40.22% as the ecosystem changed from forest to sandy, while the relative abundance of Proteobacteria decreased from 35.35% to 21.40%. Actinobacteria and Proteobacteria had significant correlations with mean annual precipitation (MAP), pH, and soil moisture and nutrients. MAP was significantly correlated with soil chemical and physical properties. The relative abundance of Actinobacteria, Proteobacteria and Planctomycetes correlated significantly with MAP, suggesting that MAP was a key factor that affected the soil bacterial community composition. However, along with the MAP gradient, Chloroflexi, Bacteroidetes and Cyanobacteria had narrow ranges that did not significantly vary with the soil and environmental factors. Overall, we conclude that the edaphic properties and/or vegetation

  10. Bacterial Community Responses to Soils along a Latitudinal and Vegetation Gradient on the Loess Plateau, China.

    PubMed

    Zeng, Quanchao; Dong, Yanghong; An, Shaoshan

    2016-01-01

    Soil bacterial communities play an important role in nutrient recycling and storage in terrestrial ecosystems. Loess soils are one of the most important soil resources for maintaining the stability of vegetation ecosystems and are mainly distributed in northwest China. Estimating the distributions and affecting factors of soil bacterial communities associated with various types of vegetation will inform our understanding of the effect of vegetation restoration and climate change on these processes. In this study, we collected soil samples from 15 sites from north to south on the Loess Plateau of China that represent different ecosystem types and analyzed the distributions of soil bacterial communities by high-throughput 454 pyrosequencing. The results showed that the 142444 sequences were grouped into 36816 operational taxonomic units (OTUs) based on 97% similarity. The results of the analysis showed that the dominant taxonomic phyla observed in all samples were Actinobacteria, Proteobacteria, Chloroflexi, Acidobacteria and Planctomycetes. Actinobacteria and Proteobacteria were the two most abundant groups in all samples. The relative abundance of Actinobacteria increased from 14.73% to 40.22% as the ecosystem changed from forest to sandy, while the relative abundance of Proteobacteria decreased from 35.35% to 21.40%. Actinobacteria and Proteobacteria had significant correlations with mean annual precipitation (MAP), pH, and soil moisture and nutrients. MAP was significantly correlated with soil chemical and physical properties. The relative abundance of Actinobacteria, Proteobacteria and Planctomycetes correlated significantly with MAP, suggesting that MAP was a key factor that affected the soil bacterial community composition. However, along with the MAP gradient, Chloroflexi, Bacteroidetes and Cyanobacteria had narrow ranges that did not significantly vary with the soil and environmental factors. Overall, we conclude that the edaphic properties and/or vegetation

  11. Determining soil and ground water use of vegetation from heat pulse, water potential and stable isotope data.

    PubMed

    Cook, P G; O'Grady, A P

    2006-05-01

    A simple model of water uptake by vegetation is used to aid the discrimination of plant water sources determined with isotope data. In the model, water extracted from different soil depths depends on the leaf-soil potential difference, a root distribution function and a lumped hydraulic conductance parameter. Measurements of plant transpiration rate, and soil and leaf water potentials are used to estimate the value of the conductance parameter. Isotopic ratios in soil water and xylem are then used to constrain the root distribution. The model is applied to field measurements of transpiration, leaf water potential and 18O composition of xylem water on Corymbia clarksoniana, Lophostemon suaveolens, Eucalpytus platyphylla and Melaleuca viridiflora, and soil water potential and 18O composition of soil water to 8.5 m depth, in an open woodland community, Pioneer Valley, North Queensland. Estimates of the water uptake from various depths below the surface are determined for each species. At the time of sampling, the proportion of groundwater extracted by the trees ranged from 100% for C. clarksoniana to <15% for L. suaveolens and E. platyphylla. The advantages of the model over the traditional approach to determining sources of water used by plants using isotope methods are that it: (1) permits more quantitative assessments of the proportion of water sourced from different depths, (2) can deal with gradational soil water isotope profiles (rather than requiring distinct values for end-members), and (3) incorporates additional data on plant water potentials and is based on simple plant physiological processes.

  12. Heavy metals and metalloid content in vegetables and soil collected from the gardens of Zagreb, Croatia.

    PubMed

    Puntarić, Dinko; Vidosavljević, Domagoj; Gvozdić, Vlatka; Puntarić, Eda; Puntarić, Ida; Mayer, Dijana; Bosnir, Jasna; Lasić, Dario; Jergović, Matijana; Klarić, Ivana; Vidosavljević, Marina; Krivdić, Ivancica

    2013-09-01

    Aim of this study was to determine concentration of Pb, Cd, As and Hg in green leafy vegetables and soil in the urban area of Zagreb, Croatia and to determine if there is a connection between the contamination of soil and vegetables. Green leafy vegetables and soil samples were taken from the gardens located in the outskirts of the city. Concentrations of Pb, Cd, As and Hg were determined by atomic absorption spectrometry; showing that average concentrations of metals and metalloids in vegetables and in soil, regardless of the location of sampling were below the maximum allowed concentration (MAC). The analysis determined that metal concentrations in only nine vegetable samples (9%) were above maximum allowed values prescribed by national and European legislation (three with higher concentrations of Pb, one with a higher concentration of Cd and five with higher concentrations of Hg). Concentrations of contaminants present in the analysed samples, in general, are lower than the ones published in similar studies. The final distribution and concentration of contaminants in vegetables of Zagreb, besides industry and traffic, is affected by the dominant wind direction.

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

    PubMed

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

    2008-12-01

    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.

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

    PubMed

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

    2008-12-01

    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

  15. Large herbivores may alter vegetation structure of semi-arid savannas through soil nutrient mediation.

    PubMed

    van der Waal, Cornelis; Kool, Ada; Meijer, Seline S; Kohi, Edward; Heitkönig, Ignas M A; de Boer, Willem F; van Langevelde, Frank; Grant, Rina C; Peel, Mike J S; Slotow, Rob; de Knegt, Henrik J; Prins, Herbert H T; de Kroon, Hans

    2011-04-01

    In savannas, the tree-grass balance is governed by water, nutrients, fire and herbivory, and their interactions. We studied the hypothesis that herbivores indirectly affect vegetation structure by changing the availability of soil nutrients, which, in turn, alters the competition between trees and grasses. Nine abandoned livestock holding-pen areas (kraals), enriched by dung and urine, were contrasted with nearby control sites in a semi-arid savanna. About 40 years after abandonment, kraal sites still showed high soil concentrations of inorganic N, extractable P, K, Ca and Mg compared to controls. Kraals also had a high plant production potential and offered high quality forage. The intense grazing and high herbivore dung and urine deposition rates in kraals fit the accelerated nutrient cycling model described for fertile systems elsewhere. Data of a concurrent experiment also showed that bush-cleared patches resulted in an increase in impala dung deposition, probably because impala preferred open sites to avoid predation. Kraal sites had very low tree densities compared to control sites, thus the high impala dung deposition rates here may be in part driven by the open structure of kraal sites, which may explain the persistence of nutrients in kraals. Experiments indicated that tree seedlings were increasingly constrained when competing with grasses under fertile conditions, which might explain the low tree recruitment observed in kraals. In conclusion, large herbivores may indirectly keep existing nutrient hotspots such as abandoned kraals structurally open by maintaining a high local soil fertility, which, in turn, constrains woody recruitment in a negative feedback loop. The maintenance of nutrient hotspots such as abandoned kraals by herbivores contributes to the structural heterogeneity of nutrient-poor savanna vegetation. PMID:21225433

  16. Heavy metal load of soil, water and vegetables in peri-urban Delhi.

    PubMed

    Singh, S; Kumar, M

    2006-09-01

    Peri-urban lands are often used for production of vegetables for better market accessibility and higher prices. But most of these lands are contaminated with heavy metals through industrial effluents, sewage and sludge, and vehicular emission. Vegetables grown in such lands, therefore, are likely to be contaminated with heavy metals and unsafe for consumption. Samples of vegetables i.e., spinach (Spinacia oleracea L.) and okra (Abelmoschus esculentus L.); soil and irrigation water were collected from 5 peri-urban sites of New Delhi to monitor their heavy metal loads. While heavy metal load of the soils were below the maximum allowable limit prescribed by the World Health Organization (WHO), it was higher in irrigation water and vegetable samples. The spinach and okra samples showed Zn, Pb and Cd levels higher than the WHO limits. The levels of Cu, however, were at their safe limits. Metal contamination was higher in spinach than in okra. Spatial variability of metal contamination was also observed in the study. Bio-availability of metals present in soil showed a positive relationship with their total content and organic matter content of soil but no relationship was observed with soil pH. Washing of vegetables with clean water was a very effective and easy way of decontaminating the metal pollution as it reduced the contamination by 75 to 100%.

  17. Influence of vegetation spatial heterogeneity on soil enzyme activity in burned Mediterranean areas

    NASA Astrophysics Data System (ADS)

    Mayor, Á. G.; Goirán, S.; Bautista, S.

    2009-04-01

    Mediterranean ecosystems are commonly considered resilient to wildfires. However, depending on fire severity and recurrence, post-fire climatic conditions and plant community type, the recovery rate of the vegetation can greatly vary. Often, the post-fire vegetation cover remains low and sparsely distributed many years after the wildfire, which could have profound impacts on ecosystem functioning. In this work, we studied the influence of vegetation patchiness on soil enzyme activity (acid phosphatase, β-glucosidase and urease), at the patch and landscape scales, in degraded dry Mediterranean shrublands affected by wildfires. At the patch scale, we assessed the variation in soil enzyme between bare soils and vegetation patches. At the landscape scale, we studied the relationships between soil enzyme activity and various landscape metrics (total patch cover, average interpatch length, average patch width, and patch density). The study was conducted in 19 sites in the Valencia Region (eastern Spain), which had been affected by large wildfires in 1991. Site selection aimed at capturing a wide range of the variability of post-fire plant recovery rates in Mediterranean areas. The activities of the three enzymes were significantly higher in soils under the vegetation canopies than in adjacent bare areas, which we attributed to the effect of plants on the soil amount of both enzyme substrates and enzymes. The differences between bare and plant microsites were larger in the case of the acid phosphatase and less marked for urease. The activity of acid phosphatase was also higher under patches of resprouter species than under patches of seeder species, probably due to the faster post-fire recovery and older age of resprouter patches in fire-prone ecosystems. Soil enzyme activities of β-glucosidase and urease in both bare soils and vegetation patches showed no relationships with any of the landscape metrics analysed. However, the activity of acid phosphatase increased

  18. Improving the Projections of Vegetation Biogeography by Integrating Climate Envelope Models and Dynamic Global Vegetation Models

    NASA Astrophysics Data System (ADS)

    Case, M. J.; Kim, J. B.

    2015-12-01

    Assessing changes in vegetation is increasingly important for conservation planning in the face of climate change. Dynamic global vegetation models (DGVMs) are important tools for assessing such changes. DGVMs have been applied at regional scales to create projections of range expansions and contractions of plant functional types. Many DGVMs use a number of algorithms to determine the biogeography of plant functional types. One such DGVM, MC2, uses a series of decision trees based on bioclimatic thresholds while others, such as LPJ, use constraining emergent properties with a limited set of bioclimatic threshold-based rules. Although both approaches have been used widely, we demonstrate that these biogeography outputs perform poorly at continental scales when compared to existing potential vegetation maps. Specifically, we found that with MC2, the algorithm for determining leaf physiognomy is too simplistic to capture arid and semi-arid vegetation in much of the western U.S., as well as is the algorithm for determining the broadleaf and needleleaf mix in the Southeast. With LPJ, we found that the bioclimatic thresholds used to allow seedling establishment are too broad and fail to capture regional-scale biogeography of the plant functional types. In response, we demonstrate a new approach to determining the biogeography of plant functional types by integrating the climatic thresholds produced for individual tree species by a series of climate envelope models with the biogeography algorithms of MC2 and LPJ. Using this approach, we find that MC2 and LPJ perform considerably better when compared to potential vegetation maps.

  19. [Soil microbial characters under different vegetation communities in taihang mountain area].

    PubMed

    Yang, Xitian; Ning, Guohua; Dong, Huiying; Li, You

    2006-09-01

    This paper measured the numbers and biomass of soil microbes as well as the soil respiration rate under mixed coniferous--broadleaved forest, mixed coniferous forest, pure coniferous forest, pure deciduous broadleaved forest, shrubs, and bare land in Taihang Mountain area, aimed to evaluate the soil microbial characters under different vegetation communities in this area. The results showed that shrub land had the greatest numbers and biomass of soil microbes, followed by deciduous broadleaved forestland, mixed coniferous--broadleaved forestland, pure coniferous forestland, and bare land. Soil respiration rate had the similar trend. When restoring the vegetations on degraded mountain land, more attention should be paid to the natural restoration capability of forest ecosystems.

  20. [Residue and Degradation of Roxarsone in the System of Soil-Vegetable].

    PubMed

    Shao, Ting; Yao, Chun-xia; Shen, Yuan-yuan; Zhang, Yu-jie; Su, Nan-nan; Zhou, Shou-biao

    2015-08-01

    The field experiment was developed for simulating the residues, transformation and degradation in soil-vegetable system of Roxarsone contained in organic fertilizer. Under the treatment, the yield of Brassica chinensis decreased in low Roxarsone concentration with a decline by 15% to 32% compared with the control group; there had an accumulating role of vegetables to arsenic, and the root was the main part; total content of arsenic in the soil was positively correlated with the dose of the applied Roxarsone; total arsenic in soil first increased and then decreased with the planting time prolonged and peaked at 12.94 mg x kg(-1), while the level of inorganic arsenic in the soil stabilized after 30 d, which accounting for 66.75% to 98.56% of the total arsenic; there existed a positively significant correlation of total arsenic content between the Brassica chinensis and the soil as well as the arsenic enrichment factor of vegetables; the degradation rate of Roxarsone in soil was slow, there was still some Roxarsone remained in soil after 45 d when added the organic fertilizer which containing Roxarsone with the dose higher than 5 000 kg x hm(-2); Roxarsone could significantly increase the number of bacteria in the soil, and low concentration showed an inhibited role in the growth of fungi and actinomyces, while high concentration of Roxarsone promoted the growth. PMID:26592042

  1. Variation in Soil Respiration Across an Alpine Soil Moisture and Vegetation Community Gradient at Niwot Ridge, Colorado

    NASA Astrophysics Data System (ADS)

    Knowles, J. F.; Blanken, P.; Williams, M. W.

    2014-12-01

    The alpine tundra is a mosaic of comingled vegetation communities that vary predominantly as a function of landscape position, micro-scale topography, subsurface permeability, and resultant soil moisture availability. We characterized the spatio-temporal variability of soil respiration from 17 alpine tundra sites across an irregular soil moisture gradient within the footprint of ongoing eddy covariance measurements over the 2011 (wet year) and 2012 (dry year) growing seasons. We then used a soil moisture threshold as a proxy to separate the sites into fellfield, dry/moist meadow, and wet meadow tundra vegetation communities. Soil moisture and soil respiration were significantly correlated across all communities (p << 0.001), but increasing soil moisture invoked a bidirectional response from fellfield and dry/moist meadow communities (directly proportional) relative to wet meadow communities (inversely proportional). Soil temperature and soil respiration were not significantly correlated. Linearly interpolating between sampling dates, the cumulative soil respiration flux over the two growing seasons ranged from 595 to 3177 g CO2 m-2, and median fluxes were 1114, 1679, and 1400 g CO2 m-2 for fellfield, dry/moist meadow, and wet meadow sites, respectively. Ecosystem respiration from nighttime eddy covariance measurements was 618 g CO2 m-2 over the same period, suggesting that soil respiration fluxes from very dry fellfield tundra disproportionately influenced the eddy covariance data. Overall, cumulative soil respiration was 50% greater in the wet year (2011) relative to the dry year (2012); therefore increased precipitation has the potential to increase soil respiration from alpine tundra as a whole.

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

    NASA Astrophysics Data System (ADS)

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

    2009-04-01

    Water erosion involves three main processes: detachment, transport and deposition of soil particles. The main factors affecting water erosion are rainfall, soil, topography, soil management and land cover and use. Soil erosion potential is increased if the soil has no or very little vegetative cover of plants and/or crop residues, whereas plant and residue cover substantially decrease rates of soil erosion. Plant and residue cover protects the soil from raindrop impact and splash, tends to slow down the movement of surface runoff and allows excess surface water to infiltrate. Moreover, plant and residue cover improve soil physical, chemical and biological properties. Soils with improved structure have a greater resistance to erosion. By contrast, accelerated soil erosion is accentuated by deforestation, biomass burning, plowing and disking, cultivation of open-row crops, etc. The erosion-reducing effectiveness of plant and/or residue covers depends on the type, extent and quantity of cover. Vegetation and residue combinations that completely cover the soil are the most efficient in controlling soil. Partially incorporated residues and residual roots are also important, as these provide channels that allow surface water to move into the soil. The effectiveness of any crop, management system or protective cover also depends on how much protection is available at various periods during the year, relative to the amount of erosive rainfall that falls during these periods. Most of the erosion on annual row crop land can be reduced by leaving a residue cover greater after harvest and over the winter months, or by inter-seeding a forage crop. Soil erosion potential is also affected by tillage operations and tillage system. Conservation tillage reduces water erosion in relation to conventional tillage by increasing soil cover and soil surface roughness. Here, we review the effect of vegetation on soil erosion in the Santa Catarina highlands, south of Brazil, under

  3. Estimation of effective hydrologic properties of soils from observations of vegetation density. M.S. Thesis; [water balance of watersheds in Clinton, Maine and Santa Paula, California

    NASA Technical Reports Server (NTRS)

    Tellers, T. E.

    1980-01-01

    An existing one-dimensional model of the annual water balance is reviewed. Slight improvements are made in the method of calculating the bare soil component of evaporation, and in the way surface retention is handled. A natural selection hypothesis, which specifies the equilibrium vegetation density for a given, water limited, climate-soil system, is verified through comparisons with observed data and is employed in the annual water balance of watersheds in Clinton, Ma., and Santa Paula, Ca., to estimate effective areal average soil properties. Comparison of CDF's of annual basin yield derived using these soil properties with observed CDF's provides excellent verification of the soil-selection procedure. This method of parameterization of the land surface should be useful with present global circulation models, enabling them to account for both the non-linearity in the relationship between soil moisture flux and soil moisture concentration, and the variability of soil properties from place to place over the Earth's surface.

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

    PubMed

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

    2013-09-01

    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.

  5. [Effects of planting years of vegetable solar greenhouse on soil microbial flora and enzyme activities].

    PubMed

    Yang, Qin; Li, Liang

    2013-09-01

    Taking the vegetable solar greenhouses having been planted for 2, 4, 6, 11, 13, 16, and 19 years as test objects, and with the open vegetable field as the control, this paper studied the variations of soil microbial flora and enzyme activities. With the increasing years of planting, the numbers of soil bacteria, actinomycetes, and total microbes in vegetable solar greenhouses decreased after an initial increase, and reached the maximum in the greenhouse of 11 years planting, with a significant increment of 54.8%, 63.7%, and 55.4%, respectively, as compared to the control. The number of soil fungi in the vegetable solar greenhouses increased steadily with increasing planting years, being about 2.2 times higher in the greenhouse of 11 years planting. Among the microbial physiological groups, the numbers of aerobic cellulose-decomposer, aerobic azotobacter, nitrite bacteria, denitrifier, and sulphur reducer showed the same variation trend as the soil bacteria's, and those in the greenhouse of 11 years planting being 1.5, 1.6, 1.9, 1.4, and 1.1 times of the control, respectively. The number of ammonifiers increased after an initial decrease, reached the minimum in the greenhouse of 13 years planting, being only 56.0% of the control. The enzyme activities of soil urease, polyphenol oxidase, sucrase, protease, cellulase, and alkaline phosphatase increased firstly and then decreased with the increasing years of planting, but soil catalase activity was relatively stable. Correlation analysis showed that the numbers of soil bacteria, actinomycetes, and total microbes were significantly positively correlated with all test soil enzyme activities, while the number of soil fungi had significant negative correlation with the activity of soil catalase. PMID:24417112

  6. [Effects of planting years of vegetable solar greenhouse on soil microbial flora and enzyme activities].

    PubMed

    Yang, Qin; Li, Liang

    2013-09-01

    Taking the vegetable solar greenhouses having been planted for 2, 4, 6, 11, 13, 16, and 19 years as test objects, and with the open vegetable field as the control, this paper studied the variations of soil microbial flora and enzyme activities. With the increasing years of planting, the numbers of soil bacteria, actinomycetes, and total microbes in vegetable solar greenhouses decreased after an initial increase, and reached the maximum in the greenhouse of 11 years planting, with a significant increment of 54.8%, 63.7%, and 55.4%, respectively, as compared to the control. The number of soil fungi in the vegetable solar greenhouses increased steadily with increasing planting years, being about 2.2 times higher in the greenhouse of 11 years planting. Among the microbial physiological groups, the numbers of aerobic cellulose-decomposer, aerobic azotobacter, nitrite bacteria, denitrifier, and sulphur reducer showed the same variation trend as the soil bacteria's, and those in the greenhouse of 11 years planting being 1.5, 1.6, 1.9, 1.4, and 1.1 times of the control, respectively. The number of ammonifiers increased after an initial decrease, reached the minimum in the greenhouse of 13 years planting, being only 56.0% of the control. The enzyme activities of soil urease, polyphenol oxidase, sucrase, protease, cellulase, and alkaline phosphatase increased firstly and then decreased with the increasing years of planting, but soil catalase activity was relatively stable. Correlation analysis showed that the numbers of soil bacteria, actinomycetes, and total microbes were significantly positively correlated with all test soil enzyme activities, while the number of soil fungi had significant negative correlation with the activity of soil catalase.

  7. Monitoring soil-vegetation interactions using non-invasive geophysical techniques

    NASA Astrophysics Data System (ADS)

    Perri, M.; Cassiani, G.; Boaga, J.; Rossi, M.; Vignoli, G.; Deiana, R.; Ursino, N.; Putti, M.; Majone, B.; Bellin, A.; Blaschek, M.; Duttmann, R.; Meyer, S.; Ludwig, R.; Soddu, A.; Dietrich, P.; Werban, U.

    2012-12-01

    The understanding of soil-vegetation-atmosphere interactions is of utmost importance in the solution of a number of hydrological questions and practical issues, including flood control, agricultural best practice, slope stability and impacts of climatic changes. Geophysical time-lapse monitoring can greatly contribute to the understanding of these interactions particularly for its capability to map in space and time the effects of vegetation on soil moisture content. In this work we present the results of two case studies showing the potential of hydro-geophysics in this context. The first example refers to the long term monitoring of the soil static and dynamic characteristics in an experimental site located in Sardinia (Italy). The main objective of this study is to understand the effects of soil - water - plants interactions on soil water balance. A combination of time-lapse electromagnetic induction (EMI) monitoring over wide areas and localized irrigation tests monitored by electrical resistivity tomography (ERT) and TDR soil moisture measurements is here used, in order to achieve quantitative field-scale estimates of moisture content from topsoil layer. Natural gamma-ray emission mapping, texture analysis and laboratory calibration of an electrical constitutive relationship on soil samples complete the dataset. We therefore observed that the growth of vegetation, with the associated below ground allocation of biomass, has a significant impact on the soil moisture dynamics. In particular vegetation extracts a large amount of water from the soil in the hot season, but it also reduces evaporation by shadowing the soil surface. In addition, vegetation enhances the soil wetting process as the root system facilitates water infiltration, thus creating a positive feedback system. The second example regards the time-lapse monitoring of soil moisture content in an apple orchard located in the Alpine region of Northern Italy (Trento). A three-dimensional cross-hole ERT

  8. Biotic carbon feedbacks in a materially closed soil-vegetation-atmosphere system

    NASA Astrophysics Data System (ADS)

    Milcu, Alexandru; Lukac, Martin; Subke, Jens-Arne; Manning, Pete; Heinemeyer, Andreas; Wildman, Dennis; Anderson, Robert; Ineson, Phil

    2012-04-01

    The magnitude and direction of the coupled feedbacks between the biotic and abiotic components of the terrestrial carbon cycle is a major source of uncertainty in coupled climate-carbon-cycle models. Materially closed, energetically open biological systems continuously and simultaneously allow the two-way feedback loop between the biotic and abiotic components to take place, but so far have not been used to their full potential in ecological research, owing to the challenge of achieving sustainable model systems. We show that using materially closed soil-vegetation-atmosphere systems with pro rata carbon amounts for the main terrestrial carbon pools enables the establishment of conditions that balance plant carbon assimilation, and autotrophic and heterotrophic respiration fluxes over periods suitable to investigate short-term biotic carbon feedbacks. Using this approach, we tested an alternative way of assessing the impact of increased CO2 and temperature on biotic carbon feedbacks. The results show that without nutrient and water limitations, the short-term biotic responses could potentially buffer a temperature increase of 2.3°C without significant positive feedbacks to atmospheric CO2. We argue that such closed-system research represents an important test-bed platform for model validation and parameterization of plant and soil biotic responses to environmental changes.

  9. Physically-based parameterization of spatially variable soil and vegetation using satellite multispectral data

    NASA Technical Reports Server (NTRS)

    Jasinski, Michael F.; Eagleson, Peter S.

    1989-01-01

    A stochastic-geometric landsurface reflectance model is formulated and tested for the parameterization of spatially variable vegetation and soil at subpixel scales using satellite multispectral images without ground truth. Landscapes are conceptualized as 3-D Lambertian reflecting surfaces consisting of plant canopies, represented by solid geometric figures, superposed on a flat soil background. A computer simulation program is developed to investigate image characteristics at various spatial aggregations representative of satellite observational scales, or pixels. The evolution of the shape and structure of the red-infrared space, or scattergram, of typical semivegetated scenes is investigated by sequentially introducing model variables into the simulation. The analytical moments of the total pixel reflectance, including the mean, variance, spatial covariance, and cross-spectral covariance, are derived in terms of the moments of the individual fractional cover and reflectance components. The moments are applied to the solution of the inverse problem: The estimation of subpixel landscape properties on a pixel-by-pixel basis, given only one multispectral image and limited assumptions on the structure of the landscape. The landsurface reflectance model and inversion technique are tested using actual aerial radiometric data collected over regularly spaced pecan trees, and using both aerial and LANDSAT Thematic Mapper data obtained over discontinuous, randomly spaced conifer canopies in a natural forested watershed. Different amounts of solar backscattered diffuse radiation are assumed and the sensitivity of the estimated landsurface parameters to those amounts is examined.

  10. Parameter selection and testing the soil water model SOIL

    NASA Astrophysics Data System (ADS)

    McGechan, M. B.; Graham, R.; Vinten, A. J. A.; Douglas, J. T.; Hooda, P. S.

    1997-08-01

    The soil water and heat simulation model SOIL was tested for its suitability to study the processes of transport of water in soil. Required parameters, particularly soil hydraulic parameters, were determined by field and laboratory tests for some common soil types and for soils subjected to contrasting treatments of long-term grassland and tilled land under cereal crops. Outputs from simulations were shown to be in reasonable agreement with independently measured field drain outflows and soil water content histories.

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

    PubMed

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

    2013-08-01

    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.

  12. Water based microwave assisted extraction of thiamethoxam residues from vegetables and soil for determination by HPLC.

    PubMed

    Karmakar, Rajib; Singh, Shashi Bala; Kulshrestha, Gita

    2012-02-01

    A microwave assisted extraction (MAE) method for determination of thiamethoxam residues in vegetable and soil samples was standardized. Insecticide spiked vegetable and soil samples were extracted by MAE using water as an extraction solvent, cleaned up by solid phase extraction and analysed by high performance liquid chromatography on photodiode array detector. The recoveries of the insecticide from various vegetable (tomato, radish, brinjal, okra, French been, sugarbeet) and soil (sandy loam, silty clay loam, sandy clay loam, loamy sand) samples at 0.1 and 0.5 μg g(-1) spiking levels ranged from 79.8% to 86.2% and from 82.1% to 87.0%, respectively. The recoveries by MAE were comparable to those obtained by the conventional blender and shake-flask extraction techniques. The precision of the MAE method was demonstrated by relative standard deviations of <3% for the insecticide.

  13. Utilization of vegetation indices to improve microwave soil moisture estimates over agricultural lands

    NASA Technical Reports Server (NTRS)

    Theis, S. W.; Blanchard, B. J.; Newton, R. W.

    1984-01-01

    A technique is presented by means of which visible/near-IR data are used to develop corrections in remotely sensed microwave soil moisture signals, in order to account for vegetation effects. Visible/IR data collected with the NASA NS001 Thematic Mapper Simulator were used to calculate the Perpendicular Vegetation Index (PVI), which was then related to the change of sensitivity of the microwave measurement to surface soil moisture. Effective estimation of soil moisture in the presence of vegetation can be made with L-band microwave radiometers and visible/IR sensors when the PVI is lower than 4.3. This technique offers a means for the estimation of moisture from a space platform over many agricultural areas, without expensive ground data collection.

  14. Post Chernobyl surveys of radiocaesium in soil, vegetation, wildlife and fungi in Great Britain

    NASA Astrophysics Data System (ADS)

    Chaplow, J. S.; Beresford, N. A.; Barnett, C. L.

    2014-12-01

    The dataset "Post Chernobyl surveys of radiocaesium in soil, vegetation, wildlife and fungi in Great Britain" was developed to enable data collected by the Natural Environment Research Council after the Chernobyl accident to be made publicly available. Data for samples collected between May 1986 (immediately after Chernobyl) to spring 1997 are presented. Additional data to radiocaesium concentrations are presented where available. The data have value in trying to assess the contribution of new sources of radiocaesium in the environment, providing baseline data for future planned releases and to aid the development and testing of models. The data are freely available for non-commercial use under Open Government Licence terms and conditions. doi:10.5285/7a5cfd3e-0247-4228-873d-5be563c4ee3b

  15. Modelling Holocene peatland and permafrost dynamics with the LPJ-GUESS dynamic vegetation model

    NASA Astrophysics Data System (ADS)

    Chaudhary, Nitin; Miller, Paul A.; Smith, Benjamin

    2016-04-01

    Dynamic global vegetation models (DGVMs) are an important platform to study past, present and future vegetation patterns together with associated biogeochemical cycles and climate feedbacks (e.g. Sitch et al. 2008, Smith et al. 2001). However, very few attempts have been made to simulate peatlands using DGVMs (Kleinen et al. 2012, Tang et al. 2015, Wania et al. 2009a). In the present study, we have improved the peatland dynamics in the state-of-the-art dynamic vegetation model (LPJ-GUESS) in order to understand the long-term evolution of northern peatland ecosystems and to assess the effect of changing climate on peatland carbon balance. We combined a dynamic multi-layer approach (Frolking et al. 2010, Hilbert et al. 2000) with soil freezing-thawing functionality (Ekici et al. 2015, Wania et al. 2009a) in LPJ-GUESS. The new model is named LPJ-GUESS Peatland (LPJ-GUESS-P) (Chaudhary et al. in prep). The model was calibrated and tested at the sub-arctic mire in Stordalen, Sweden, and the model was able to capture the reported long-term vegetation dynamics and peat accumulation patterns in the mire (Kokfelt et al. 2010). For evaluation, the model was run at 13 grid points across a north to south transect in Europe. The modelled peat accumulation values were found to be consistent with the published data for each grid point (Loisel et al. 2014). Finally, a series of additional experiments were carried out to investigate the vulnerability of high-latitude peatlands to climate change. We find that the Stordalen mire will sequester more carbon in the future due to milder and wetter climate conditions, longer growing seasons, and the carbon fertilization effect. References: - Chaudhary et al. (in prep.). Modelling Holocene peatland and permafrost dynamics with the LPJ-GUESS dynamic vegetation model - Ekici A, et al. 2015. Site-level model intercomparison of high latitude and high altitude soil thermal dynamics in tundra and barren landscapes. The Cryosphere 9: 1343

  16. Does vegetation type matter? Plant-soil interactions change urban rain garden hydrology

    NASA Astrophysics Data System (ADS)

    Johnston, M. R.; Balster, N. J.

    2009-12-01

    Residential infiltration basins or rain gardens are being installed at an ever-increasing rate across the urban landscape, yet their impact on the urban hydrologic cycle remains largely untested. Specifically, because rain garden design varies considerably, we know little about how plant-soil dynamics control their hydrologic function. In a controlled field experiment with closed-system rain gardens, we tested the hydrologic response of three vegetation treatments common in rain garden design (shrubs, wet-mesic prairie, turfgrass). We used a complete, randomized block design in which each vegetative treatment was replicated three times. Each rain garden represented 17% of a contributing roof area where stormwater was collected and then applied following precipitation events. We continuously monitored stormwater input, soil water content, and soil exfiltration to assess differences in the hydrologic function of each rain garden. Overall, vegetation type significantly changed the magnitude and timing of the hydrologic response. During the months of June and July, 2009, the rain gardens planted with shrubs, prairie, and turfgrass all reduced the volume of soil exfiltration by 50%, 30%, and 17%, respectively, relative to the non-vegetated controls. Similarly, depending on storm magnitude and antecedent soil moisture, vegetation type significantly decreased the mean peak flow rate of exfiltration (p < 0.001), as well as the duration of the exfiltration response (p < 0.0001). The flashiest hydrologic responses (i.e. shortest lag time, highest peak flow rate) were observed in the turfgrass gardens. We explain these vegetative-mediated responses in hydrology relative to differences in infiltration, aboveground dry mass, root dynamics, and transpirative loss. Our data suggest that changing the vegetation type of urban rain gardens yields marked differences in the hydrologic budget via shifts in ecohydrological processes.

  17. Mapping the spectral variability in photosynthetic and non-photosynthetic vegetation, soils, and shade using AVIRIS

    NASA Technical Reports Server (NTRS)

    Roberts, Dar A.; Smith, Milton O.; Sabol, Donald E.; Adams, John B.; Ustin, Susan L.

    1992-01-01

    The primary objective of this research was to map as many spectrally distinct types of green vegetation (GV), non-photosynthetic vegetation (NPV), shade, and soil (endmembers) in an Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) scene as is warranted by the spectral variability of the data. Once determined, a secondary objective was to interpret these endmembers and their abundances spatially and spectrally in an ecological context.

  18. Coincidence and spatial variability of geology, soils, and vegetation, Mill Run watershed, Virginia.

    USGS Publications Warehouse

    Olson, C.G.; Hupp, C.R.

    1986-01-01

    The Mill Run watershed is a structurally-controlled synclinal basin on the eastern limb of the Massanutten Mountain complex of NW Virginia. Bedrock contacts are obscured by coarse sandstone debris from exposures near basin divides. Colluvium blankets more than half the basin, masking geomorphic surfaces, affecting vegetation patterns, and contributing to the convexity of the alluvial, terrace, pediment and erosion surfaces. Vegetation is strongly interdependent with geomorphology, bedrock geology, and soils. - from Authors

  19. Soils under conservation agriculture with vegetables in Siem Reap, Cambodia

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Smallholder vegetable farmers in Siem Reap, Cambodia experienced declining crop productivity. It could be a result of a mixture of factors such as nutrient and pest problems and extreme weather events such as droughts and/or heavy rains. The no-till, continuous mulch and diverse species principles o...

  20. The effect of bullet removal and vegetation on mobility of Pb in shooting range soils.

    PubMed

    Fayiga, Abioye O; Saha, Uttam

    2016-10-01

    Lead (Pb) contamination at shooting ranges is a public health concern because Pb is a toxic metal. An experiment was conducted to determine the effect of two best management practices; bullet removal and vegetation, on bioavailability and leachability of Pb in three shooting range (SR) soils. St. Augustine grass was grown in sieved (2 mm) and un-sieved SR soils for 8 weeks after which leachates, soil and plant samples were analyzed. Bullet removal reduced total soil Pb, increased Mehlich-3 Pb in unvegetated soils and increased dissolved organic carbon (DOC) in all soils. Bullet removal increased leaching in two SR soils while grasses reduced leaching but increased water soluble Pb in two SR soils. The roots of the grasses were able to accumulate more Pb in the root (1893-5021 mg kg(-1)) than the aboveground biomass (252-880 mg kg(-1)) due to mobilization of Pb in the rhizosphere. Grasses had a higher plant biomass in unsieved soils suggesting tolerance to the presence of bullets in the unsieved soils. Results suggest that bullet removal probably increased microbial activity and Pb bioavailability in the soil. The leaching and bioavailability of Pb in shooting range soils depends on biological activities and chemical processes in the soil. PMID:27391048

  1. The effect of bullet removal and vegetation on mobility of Pb in shooting range soils.

    PubMed

    Fayiga, Abioye O; Saha, Uttam

    2016-10-01

    Lead (Pb) contamination at shooting ranges is a public health concern because Pb is a toxic metal. An experiment was conducted to determine the effect of two best management practices; bullet removal and vegetation, on bioavailability and leachability of Pb in three shooting range (SR) soils. St. Augustine grass was grown in sieved (2 mm) and un-sieved SR soils for 8 weeks after which leachates, soil and plant samples were analyzed. Bullet removal reduced total soil Pb, increased Mehlich-3 Pb in unvegetated soils and increased dissolved organic carbon (DOC) in all soils. Bullet removal increased leaching in two SR soils while grasses reduced leaching but increased water soluble Pb in two SR soils. The roots of the grasses were able to accumulate more Pb in the root (1893-5021 mg kg(-1)) than the aboveground biomass (252-880 mg kg(-1)) due to mobilization of Pb in the rhizosphere. Grasses had a higher plant biomass in unsieved soils suggesting tolerance to the presence of bullets in the unsieved soils. Results suggest that bullet removal probably increased microbial activity and Pb bioavailability in the soil. The leaching and bioavailability of Pb in shooting range soils depends on biological activities and chemical processes in the soil.

  2. Relations between soil moisture and satellite vegetation indices in the U.S. Corn Belt

    USGS Publications Warehouse

    Adegoke, Jimmy O.; Carleton, A.M.

    2002-01-01

    Satellite-derived vegetation indices extracted over locations representative of midwestern U.S. cropland and forest for the period 1990-94 are analyzed to determine the sensitivity of the indices to neutron probe soil moisture measurements of the Illinois Climate Network (ICN). The deseasoned (i.e., departures from multiyear mean annual cycle) soil moisture measurements are shown to be weakly correlated with the deseasoned full resolution (1 km ?? 1 km) normalized difference vegetation index (NDVI) and fractional vegetation cover (FVC) data over both land cover types. The association, measured by the Pearson-moment-correlation coefficient, is stronger over forest than over cropland during the growing season (April-September). The correlations improve successively when the NDVI and FVC pixel data are aggregated to 3 km ?? 3 km, 5 km ?? 5 km, and 7 km ?? 7 km areas. The improved correlations are partly explained by the reduction in satellite navigation errors as spatial aggregation occurs, as well as the apparent scale dependence of the NDVI-soil moisture association. Similarly, stronger relations are obtained with soil moisture data that are lagged by up to 8 weeks with respect to the vegetation indices, implying that soil moisture may be a useful predictor of warm season satellite-derived vegetation conditions. This study suggests that a "long-term" memory of several weeks is present in the near-surface hydrological characteristics, especially soil water content, of the Midwest Corn Belt. The memory is integrated into the satellite vegetation indices and may be us??eful for predicting crop yield estimates and surface temperature anomalies.

  3. Assessment of Fluoride Concentration of Soil and Vegetables in Vicinity of Zinc Smelter, Debari, Udaipur, Rajasthan

    PubMed Central

    Bhat, Nagesh; Asawa, Kailash; Tak, Mridula; Shinde, Kushal; Singh, Anukriti; Gandhi, Neha; Gupta, Vivek Vardhan

    2015-01-01

    Background As of late, natural contamination has stimulated as a reaction of mechanical and other human exercises. In India, with the expanding industrialization, numerous unsafe substances are utilized or are discharged amid generation as cleans, exhaust, vapours and gasses. These substances at last are blended in the earth and causes health hazards. Objective To determine concentration of fluoride in soils and vegetables grown in the vicinity of Zinc Smelter, Debari, Udaipur, Rajasthan. Materials and Methods Samples of vegetables and soil were collected from areas situated at 0, 1, 2, 5, and 10 km distance from the zinc smelter, Debari. Three samples of vegetables (i.e. Cabbage, Onion and Tomato) and 3 samples of soil {one sample from the upper layer of soil (i.e. 0 to 20 cm) and one from the deep layer (i.e. 20 – 40 cm)} at each distance were collected. The soil and vegetable samples were sealed in clean polythene bags and transported to the laboratory for analysis. One sample each of water and fertilizer from each distance were also collected. Results The mean fluoride concentration in the vegetables grown varied between 0.36 ± 0.69 to 0.71 ± 0.90 ppm. The fluoride concentration in fertilizer and water sample from various distances was found to be in the range of 1.4 – 1.5 ppm and 1.8 – 1.9 ppm respectively. Conclusion The fluoride content of soil and vegetables was found to be higher in places near to the zinc smelter. PMID:26557620

  4. [Spatial variation of soil moisture/salinity and the relationship with vegetation under natural conditions in Yancheng coastal wetland].

    PubMed

    Zhang, Hua-Bing; Liu, Hong-Yu; Li, Yu-Feng; An, Jing; Xue, Xing-Yu; Hou, Ming-Hang

    2013-02-01

    Taking the core part of Yancheng national nature reserve as the study area, according to soil sampling analysis of coastal wetlands in April and May 2011 land the 2011 ETM + remote sensing image, the spatial difference characteristic of coastal wetlands soil moisture and salinity, and the relationship with vegetation under natural conditions, were investigated with the model of correspondence analysis (CCA), linear regression simulation and geo-statistical method. The results showed: Firstly, the average level of the soil moisture was fluctuating between 36.820% and 46.333% , and the soil salinity was between 0.347% and 1.328% , in a more detailed sense, the Spartina swamp was the highest, followed by the mudflats swamp, the Suaeda salsa swamp, and the Reed marsh. Secondly, the spatial variation of soil moisture was consistent with that of the salinity, and the degree of variation in the east-west direction was greater than that in the north-south. The maximum soil moisture and salinity were found in the southwest Spartina swamp. The minimum was in the Reed swamp. The soil moisture and salinity were divided into 5 levels, from I to V. Level IV occupied the highest proportion, which were 36.156% and 28.531% , respectively. Finally, different landscape types with the combination of soil moisture and salinity showed a common feature that the moisture and salinity were from both high to low. The soil moisture value of Reed marshes was lower than 40.116% and the salinity value was lower than 0. 676% . The soil moisture value of Suaeda salsa marshes was between 38. 162% and 46. 403% and the salinity value was between 0.417% and 1.295%. The soil moisture value of Spartina swamp was higher than 43.214% and the salinity was higher than 1.090%. The soil moisture value of beach was higher than 43.214% and the salinity was higher than 0.677%.

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

    NASA Astrophysics Data System (ADS)

    Simmer, C.; Thiele-Eich, I.

    2015-12-01

    The Collaborative Research Centre TR32 has the goal to perform pattern-based prediction of states and fluxes of water, CO2 and energy in terrestrial systems across scales. For this, the TR32 set up the following three elements during the past nine years: measurement techniques that allow us to characterize and monitor the spatiotemporal dynamics and evolution of system properties across scales, a cross-scale, multi-compartment terrestrial system modeling approach that includes all relevant processes using the terrestrial model platform TerrSysMP and state variable assimilation and parameter estimation methods. We will present examples of how the TR32 utilizes these three elements to improve our understanding of the water cycle. The available soil moisture monitoring network consisting of e.g. cosmic-ray sensors or an in situ NMR slim-line logging tool has been helpful in understanding the interactions of plant growth and soil moisture dynamics. New algorithms derive soil moisture from satellite based SAR systems, which showed potential for the derivation of surface roughness and vegetation information. For surface precipitation, a radar composite using observations from two dual-polarized X-band Doppler radars provides nearly 100% coverage of the Rur catchment. To also be able to include other precipitation observations which occur at different temporal and spatial resolutions, such as rain gauges, a high resolution space-time precipitation model is being developed. Commercial microwave links used for cell phone communication have also been experimented with to improve polarimetric quantitative precipitation estimation. In addition, uncertainty plays a major role with respect to the central goal of the TR32 and is taken into account in various ways. For example, model uncertainty in the Rur catchment results in large parts from anthropogenic activities such as e.g. drainage patterns in fields, the control of the Rur discharge, groundwater pumping, storage lakes

  6. Understory vegetation leads to changes in soil acidity and in microbial communities 27 years after reforestation.

    PubMed

    Fu, Xiaoli; Yang, Fengting; Wang, Jianlei; Di, Yuebao; Dai, Xiaoqin; Zhang, Xinyu; Wang, Huimin

    2015-01-01

    Experiments with potted plants and removed understories have indicated that understory vegetation often affects the chemical and microbial properties of soil. In this study, we examined the mechanism and extent of the influence of understory vegetation on the chemical and microbial properties of soil in plantation forests. The relationships between the vegetational structure (diversity for different functional layers, aboveground biomass of understory vegetation, and species number) and soil properties (pH, microbial community structure, and levels of soil organic carbon, total nitrogen, and inorganic nitrogen) were analyzed across six reforestation types (three pure needleleaf forests, a needle-broadleaf mixed forest, a broadleaf forest, and a shrubland). Twenty-seven years after reforestation, soil pH significantly decreased by an average of 0.95 across reforestation types. Soil pH was positively correlated with the aboveground biomass of the understory. The levels of total, bacterial, and fungal phospholipid fatty acids, and the fungal:bacterial ratios were similar in the shrubland and the broadleaf forest. Both the aboveground biomass of the understory and the diversity of the tree layer positively influenced the fungal:bacterial ratio. Improving the aboveground biomass of the understory could alleviate soil acidification. An increase in the aboveground biomass of the understory, rather than in understory diversity, enhanced the functional traits of the soil microbial communities. The replacement of pure plantations with mixed-species stands, as well as the enhancement of understory recruitment, can improve the ecological functions of a plantation, as measured by the alleviation of soil acidification and increased fungal dominance.

  7. Vegetation-induced spatial variability of soil redox properties in wetlands

    NASA Astrophysics Data System (ADS)

    Szalai, Zoltán; Jakab, Gergely; Kiss, Klaudia; Ringer, Marianna; Balázs, Réka; Zacháry, Dóra; Horváth Szabó, Kata; Perényi, Katalin

    2016-04-01

    Vegetation induced land patches may result spatial pattern of on soil Eh and pH. These spatial pattern are mainly emerged by differences of aeration and exudation of assimilates. Present paper focuses on vertical extent and temporal dynamics of these patterns in wetlands. Two study sites were selected: 1. a plain wetland on calcareous sandy parent material (Ceglédbercel, Danube-Tisza Interfluve, Hungary); 2. headwater wetland with calcareous loamy parent material (Bátaapáti, Hungary). Two vegetation patches were studied in site 1: sedgy (dominated by Carex riparia) and reedy (dominated by Phragmites australis). Three patches were studied in site2: sedgy1 (dominated by C vulpina), sedgy 2 (C. riparia); nettle-horsetail (Urtica dioica and Equisetum arvense). Boundaries between patches were studied separately. Soil redox, pH and temperature studied by automated remote controlled instruments. Three digital sensors (Ponsell) were installed in each locations: 20cm and 40cm sensors represent the solum and 100 cm sensor monitors the subsoil). Groundwater wells were installed near to triplets for soil water sampling. Soil Eh, pH and temperature values were recorded in each 10 minutes. Soil water sampling for iron and DOC were carried out during saturated periods. Spatial pattern of soil Eh is clearly caused by vegetation. We measured significant differences between Eh values of the studied patches in the solum. We did not find this kinds horizontal differences in the subsoil. Boundaries of the patches usually had more reductive soil environment than the core areas. We have found temporal dynamics of the spatial redox pattern. Differences were not so well expressed during wintertime. These spatial patterns had influence on the DOC and iron content of porewater, as well. Highest temporal dynamics of soil redox properties and porewater iron could be found in the boundaries. These observations refer to importance patchiness of vegetation on soil chemical properties in

  8. [Sizes of soil macropores and related main affecting factors on a vegetated basalt slope].

    PubMed

    Guan, Qi; Xu, Ze-Min; Tian, Lin

    2013-10-01

    The landslide on vegetated slopes caused by extreme weather has being increased steadily, and the preferential flow in soil macropores plays an important role in the landslide. By using water breakthrough curve and Poiseuille equation, this paper estimated the radius range, amount, and average volume of soil macropores on a vegetated basalt slope of Maka Mountain, Southwest China, and analyzed the distribution of the soil macropores and the main affecting factors. In the study area, the radius of soil macropores ranged from 0.3 to 1.8 mm, mainly between 0.5 and 1.2 mm. The large-radius macropores (1.4-1.8 mm) were lesser, while the small-radius macropores (< 1.4 mm) were more. With the development of soil profile, soil macropores were more in upper layers and lesser in deeper layers. The average volume of the macropores contributed 84.7% to the variance of steady effluent rate. Among the factors affecting the average volume of the large macropores, vegetations root mass had a linear relationship, with the correlation coefficient being 0.70, and soil organic matter content also had a linear relationship, with the correlation coefficient being 0.64.

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

    PubMed Central

    He, Xunyang; Liu, Lu; Wang, Kelin

    2014-01-01

    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

  10. The soil biota composition along a progressive succession of secondary vegetation in a karst area.

    PubMed

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

    2014-01-01

    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.

  11. [Sizes of soil macropores and related main affecting factors on a vegetated basalt slope].

    PubMed

    Guan, Qi; Xu, Ze-Min; Tian, Lin

    2013-10-01

    The landslide on vegetated slopes caused by extreme weather has being increased steadily, and the preferential flow in soil macropores plays an important role in the landslide. By using water breakthrough curve and Poiseuille equation, this paper estimated the radius range, amount, and average volume of soil macropores on a vegetated basalt slope of Maka Mountain, Southwest China, and analyzed the distribution of the soil macropores and the main affecting factors. In the study area, the radius of soil macropores ranged from 0.3 to 1.8 mm, mainly between 0.5 and 1.2 mm. The large-radius macropores (1.4-1.8 mm) were lesser, while the small-radius macropores (< 1.4 mm) were more. With the development of soil profile, soil macropores were more in upper layers and lesser in deeper layers. The average volume of the macropores contributed 84.7% to the variance of steady effluent rate. Among the factors affecting the average volume of the large macropores, vegetations root mass had a linear relationship, with the correlation coefficient being 0.70, and soil organic matter content also had a linear relationship, with the correlation coefficient being 0.64. PMID:24483084

  12. Effect of vegetation on the presence and genetic diversity of Bacillus thuringiensis in soil.

    PubMed

    Ricieto, Ana Paula Scaramal; Fazion, Fernanda Aparecida Pires; Carvalho Filho, Celso Duarte; Vilas-Boas, Laurival Antonio; Vilas-Bôas, Gislayne Trindade

    2013-01-01

    Bacillus thuringiensis isolates were obtained from soil samples collected at different sites located in the same region but with different vegetation. The sites showed different frequencies of B. thuringiensis, depending on the type of vegetation. Strains of B. thuringiensis were found to be less common in samples of riparian forest soil than in soil of other types of vegetation. The rate of occurrence of B. thuringiensis in the samples also varied according to the vegetation. These results show that whenever this bacterium was found, it showed a high rate of occurrence, indicating that this species could be better adapted to using soil as a reservoir than other Bacillus species. The presence of cry genes was analyzed by polymerase chain reaction, and genes that exhibited activity against Diptera species were the most commonly found. The isolates obtained were characterized by random amplified polymorphic DNA, and 50% were clustered into clonal groups. These results demonstrated the possible occurrence of a high number of genetically similar strains when samples are collected from the same region, even if they are from locations with different vegetation.

  13. Vegetation uptake of nitrogen and base cations in China and its role in soil acidification.

    PubMed

    Duan, Lei; Huang, Yongmei; Hao, Jiming; Xie, Shaodong; Hou, Min

    2004-09-01

    Vegetation uptake of nitrogen and base cations may be an important source of soil acidity. In this study, the uptake rate of nitrogen and base cations was estimated for each major vegetation type in China. Although the uptake rates of most vegetation types are lower than 2.0 keq ha(-1) a(-1), great variations exist because of the significant differences in net primary productivity and elemental composition. Uptake rates decreased gradually from southeast to northwest, except for the wide-distributed agricultural areas in the east of China, where the nitrogen and base cation uptake rates are near zero. It is evident that this pattern coincides well with the distribution of the annual mean precipitation. However, the geographical distribution of the base cation uptake rate is not entirely the same as that of nitrogen, which indicates the importance of soil conditions in determining the chemical component and hence the uptake rate of different vegetation. The acidity input caused by vegetation uptake is quite high (>0.5 keq ha(-1) a(-1)), and even higher than the current acid deposition and the alkalinity produced by soil weathering in some areas, which indicates that the growth of the plants may contribute significantly to the soil acidification problem in China. PMID:15325168

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

    PubMed Central

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

    2013-01-01

    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

  15. Influence of Vegetations' Metabolites on the Composition and Functioning of Soil Microbial Complex

    NASA Astrophysics Data System (ADS)

    Biryukov, Mikhail

    2013-04-01

    Microbiota is one of the major factors of soils fertility. It transforms organic substances in soil and, therefore, serves as the main component in the cycles of carbon and nitrogen. Microbial communities (MC) are characterized as highly diverse and extremely complex structures. This allows them to adapt to any affection and provide all the necessary biospheric functions. Hence, the study of their functional diversity and adaptivity of microbiota provides the key to the understanding of the ecosystems' functioning and their adaptivity to the human impact. The formation of MC at the initial stage is regulated by the fluxes of substrates and biologically active substances (BAS), which vary greatly in soils under different vegetations. These fluxes are presented by: low molecular weights organic substances (LMWOS), which can be directly included in metabolism of microbes; polymers, that can be decomposed to LMWOS by exoenzymes; and more complex compounds, having different "drug effects" (e.g. different types of phenolic acids) and regulating growth and enzymatic properties of microbiota. Therefore, the main hypothesis of the research was formulated as follows: penetration of different types of substrates and BAS into soil leads to the emergence of MC varying in enzymatic properties and structure. As a soil matrix we used the soil from the untreated variant of the lysimeter model experiment taking place in the faculty of Soil Science of the MSU for over the last 40 years. It was sieved with a 2mm sieves, humidified and incubated at 25C during one week. Subsequently, the samples were air-dried with occasional stirring for one more week. Thereafter, aliquots of the prepared soil were taken for the different experimental variants. The samples were rewetted with solutions of various substrates (glucose, cellulose, starch, etc.) and thoroughly mixed. The control variant was established with addition of deionised water. The samples were incubated at the 25C. During the

  16. Vegetation and climate controls on potential CO2, DOC and DON production in northern latitude soils

    USGS Publications Warehouse

    Neff, J.C.; Hooper, D.U.

    2002-01-01

    Climatic change may influence decomposition dynamics in arctic and boreal ecosystems, affecting both atmospheric CO2 levels, and the flux of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) to aquatic systems. In this study, we investigated landscape-scale controls on potential production of these compounds using a one-year laboratory incubation at two temperatures (10?? and 30??C). We measured the release of CO2, DOC and DON from tundra soils collected from a variety of vegetation types and climatic regimes: tussock tundra at four sites along a latitudinal gradient from the interior to the north slope of Alaska, and soils from additional vegetation types at two of those sites (upland spruce at Fairbanks, and wet sedge and shrub tundra at Toolik Lake in northern Alaska). Vegetation type strongly influenced carbon fluxes. The highest CO2 and DOC release at the high incubation temperature occurred in the soils of shrub tundra communities. Tussock tundra soils exhibited the next highest DOC fluxes followed by spruce and wet sedge tundra soils, respectively. Of the fluxes, CO2 showed the greatest sensitivity to incubation temperatures and vegetation type, followed by DOC. DON fluxes were less variable. Total CO2 and total DOC release were positively correlated, with DOC fluxes approximately 10% of total CO2 fluxes. The ratio of CO2 production to DOC release varied significantly across vegetation types with Tussock soils producing an average of four times as much CO2 per unit DOC released compared to Spruce soils from the Fairbanks site. Sites in this study released 80-370 mg CO2-C g soil C-1 and 5-46 mg DOC g soil C-1 at high temperatures. The magnitude of these fluxes indicates that arctic carbon pools contain a large proportion of labile carbon that could be easily decomposed given optimal conditions. The size of this labile pool ranged between 9 and 41% of soil carbon on a g soil C basis, with most variation related to vegetation type rather than

  17. Optimum strategies for mapping vegetation using multiple-endmember spectral mixture models

    NASA Astrophysics Data System (ADS)

    Roberts, Dar A.; Gardner, Margaret E.; Church, Rick; Ustin, Susan L.; Green, Robert O.

    1997-10-01

    Improved vegetation maps are required for fire management and biodiversity assessment, from critical inputs for hydrological and biogeochemical models and represent a means for scaling-up point measurements. At scales greater than 10 meters, vegetation communities are typically mixed consisting of leaves, branches, exposed soil and shadows. To map mixed vegetation, many researchers employ spectral mixture analysis (SMA). In most SMA applications, a single set of spectra consisting of green vegetation, soil, non- photosynthetic vegetation and shade are used to 'unmix' images. However, because most scenes contain more than four components, this simple approach leads to fraction errors and may fail to differentiate many vegetation types. In this work, we apply a new approach called multiple endmember spectral mixture analysis, in which the number and types of endmembers vary per-pixel. Using this approach, hundreds of unique models are generated that account for community specific differences in plant chemistry, physical attributes and phenology. Additionally, we describe a new strategy for developing and organizing regionally specific spectral libraries. We present result from a study in the Santa Monica Mountains using AVIRIS data, in which we map grassland and chaparral communities, mapping species dominance in some cases to a high degree of accuracy.

  18. Atmospheric carbon exchange associated with vegetation and soils in urban and suburban land uses

    SciTech Connect

    Rowntree, R.A.

    1993-12-31

    In studies of the global C cycle prior to the 1980s, urban ecosystems were largely ignored, in part because them were inadequate measures of phytomass and soil carbon for the various land uses associated with cities. In the last decade, progress has been made in gathering urban vegetation data and recently, estimates of urban land use carbon storage and fluxes have been attempted. Demographic trends in many countries suggest that urban areas are growing. Thus it is important to discover the appropriate concepts and methods for understanding greenhouse gas fluxes from urban-related vegetation and soils.

  19. Impact of vegetation types on soil organic carbon stocks SOC-S in Mediterranean natural areas

    NASA Astrophysics Data System (ADS)

    Parras-Alcántara, Luis; Lozano-García, Beatriz; Cantudo-Pérez, Marta

    2015-04-01

    with different vegetation types (Quercus suber, Quercus ilex, Quercus faginea, Pinus pinaster and Pinus pinea) in The Cardeña-Montoro Natural Park, a nature reserve that consists of a 38,449 ha forested area in southern Spain. Sixty-eight sampling points were selected in the study zone. Each sampling point was analyzed as soil control section with different depth increments (0-25, 25-50, 50-75 and 75-100 cm). The studied soils were classified as Cambisols and the major goal of this research was to study the SOCS variability at regional scale. The total SOCS in The Cardeña-Montoro Natural Park was higher in MEOW with olive grove (111,69 Mg ha-1) and lower in MEOW with Quercus faginea (93,57 Mg ha-1). However, when the top soil (superficial section control) was analyzed, the SOCS was the highest in MEOW with olive grove (70,12 Mg-1) and the lowest in MEOW with Pinus (47,82 Mg ha-1). This research is a preliminary assessment for modeling SOCS at the regional level in Mediterranean natural areas. References Hontoria, C., Rodríguez-Murillo, J., and Saa, A.: Contenido de carbono orgánico en el suelo y factores de control en la España Peninsular, Edafología, 11, 149-155, 2004. Parras-Alcántara, L., Díaz-Jaimes, L., and Lozano-García, B: Organic farming affects C and N in soils under olive groves in Mediterranean areas, Land Degrad. Develop., in press, available online: in Wiley Online Library (wileyonlinelibrary.com), http://dx.doi.org/10.1002/ldr.2231, 2013. Parras-Alcántara, L., Díaz-Jaimes, L., Lozano-García, B., Fernández Rebollo, P., Moreno Elcure, F., Carbonero Muñoz, M.D.: Organic farming has little effect on carbon stock in a Mediterranean dehesa (southern Spain). Catena 113 (2014) 9-17. http://dx.doi.org/10.1016/j.catena.2013.09.002 Parras-Alcántara, L., Díaz-Jaimes, L., and Lozano-García, B.: Management effects on soil organic carbon stock in Mediterranean open rangelands -- treeless grasslands, Land Degrad. Develop., in press, available online: in

  20. Response of Soil Fungi Community Structure to Salt Vegetation Succession in the Yellow River Delta.

    PubMed

    Wang, Yan-Yun; Guo, Du-Fa

    2016-10-01

    High-throughput sequencing technology was used to reveal the composition and distribution of fungal community structure in the Yellow River Delta under bare land and four kinds of halophyte vegetation (saline seepweed, Angiospermae, Imperata and Apocynum venetum [A. venetum]). The results showed that the soil quality continuously improved with the succession of salt vegetation types. The soil fungi richness of mild-salt communities (Imperata and A. venetum) was relatively higher, with Shannon index values of 5.21 and 5.84, respectively. The soil fungi richness of severe-salt-tolerant communities (saline seepweed, Angiospermae) was relatively lower, with Shannon index values of 4.64 and 4.66, respectively. The UniFrac metric values ranged from 0.48 to 0.67 when the vegetation was in different succession stages. A total of 60,174 valid sequences were obtained for the five vegetation types, and they were classified into Ascomycota, Basidiomycota, Chytridiomycota, Glomeromycota and Mucoromycotina. Ascomycota had the greatest advantage among plant communities of Imperata and A. venetum, as indicated by relative abundances of 2.69 and 69.97 %, respectively. Basidiomycota had the greatest advantage among mild-salt communities of saline seepweed and Angiospermae, with relative abundances of 9.43 and 6.64 %, respectively. Soil physical and chemical properties were correlated with the distribution of the fungi, and Mucor was significantly correlated with soil moisture (r = 0.985; P < 0.01). Soil quality, salt vegetation and soil fungi were influenced by each other.

  1. Response of Soil Fungi Community Structure to Salt Vegetation Succession in the Yellow River Delta.

    PubMed

    Wang, Yan-Yun; Guo, Du-Fa

    2016-10-01

    High-throughput sequencing technology was used to reveal the composition and distribution of fungal community structure in the Yellow River Delta under bare land and four kinds of halophyte vegetation (saline seepweed, Angiospermae, Imperata and Apocynum venetum [A. venetum]). The results showed that the soil quality continuously improved with the succession of salt vegetation types. The soil fungi richness of mild-salt communities (Imperata and A. venetum) was relatively higher, with Shannon index values of 5.21 and 5.84, respectively. The soil fungi richness of severe-salt-tolerant communities (saline seepweed, Angiospermae) was relatively lower, with Shannon index values of 4.64 and 4.66, respectively. The UniFrac metric values ranged from 0.48 to 0.67 when the vegetation was in different succession stages. A total of 60,174 valid sequences were obtained for the five vegetation types, and they were classified into Ascomycota, Basidiomycota, Chytridiomycota, Glomeromycota and Mucoromycotina. Ascomycota had the greatest advantage among plant communities of Imperata and A. venetum, as indicated by relative abundances of 2.69 and 69.97 %, respectively. Basidiomycota had the greatest advantage among mild-salt communities of saline seepweed and Angiospermae, with relative abundances of 9.43 and 6.64 %, respectively. Soil physical and chemical properties were correlated with the distribution of the fungi, and Mucor was significantly correlated with soil moisture (r = 0.985; P < 0.01). Soil quality, salt vegetation and soil fungi were influenced by each other. PMID:27449214

  2. Agricultural use of soil, consequences in soil organic matter and hydraulic conductivity compared with natural vegetation in central Spain

    NASA Astrophysics Data System (ADS)

    Vega, Verónica; Carral, Pilar; Alvarez, Ana Maria; Marques, Maria Jose

    2014-05-01

    When ecosystems are under pressure due to high temperatures and water scarcity, the use of land for agriculture can be a handicap for soil and water conservation. The interactions between plants and soils are site-specific. This study provides information about the influence of the preence vs. The absence of vegetation on soil in a semi-arid area of the sout-east of Madrid (Spain, in the Tagus River basin. In this area soil materials are developed over a calcareous-evaporitic lithology. Soils can be classified as Calcisols, having horizons of accumulation with powdered limestone and irregular nodules of calcium carbonate. They can be defined as Haplic Cambisols and Leptic Calcisols (WRB 2006-FAO). The area is mainly used for rainfed agriculture, olive groves, vineyards and cereals. There are some patches of bushes (Quercus sp.) and grasses (Stipa tenacissima L.) although only found on the top of the hills. This study analyses the differences found in soils having three different covers: Quercus coccifera, Stipa tenacissima and lack of vegetation. This last condition was found in the areas between cultivated olive trees. Soil organic matter, porosity and hydraulic conductivity are key properties of soil to understand its ability to adapt to climate or land use changes. In order to measure the influence of different soil covers, four replicates of soil were sampled in each condition at two soil depth, (0-10 cm and 10-20 cm). Hydraulic conductivity was measured in each soil condition and replicate using a Mini-disk® infiltrometer. There were no differences between the two depths sampled. Similarly, there were no changes in electric conductivity (average 0.1±0.03 dS m-1); pH (8.7±0.2) or calcium carbonate content (43±20 %). Nevertheless, significant differences (p>0.001) were found in soil organic matter. The maximum was found in soils under Quercus (4.7±0.5 %), followed by Stipa (2.2±1.1 %). The soil without vegetation in the areas between olive trees had only 0

  3. Evaluation of Thematic Mapper for detecting soil properties under grassland vegetation

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

    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.

  4. Influences of biochar addition on vegetable soil nitrogen balance and pH buffering capacity

    NASA Astrophysics Data System (ADS)

    Yu, Y.; Odindo, AO; Xue, L.; Yang, L.

    2016-08-01

    Leaching is a major path for chemical nitrogen fertilizer loss from in vegetable soil, which would destroy soil pH buffering capacity soil and result in acidification. It has been a common phenomenon in Tai Lake Region, China. However, few study focused on the change soil pH buffering capacity, especially the effect of soil amendment on pH buffering capacity. In this study, a pot experiment was conducted to research the effects of biochar addition to a vegetable soil on nitrogen leaching and pH buffering capacity with pakchoi (B.chinensis L.) growth as the experimental crop. The results showed that biochar could significantly increase the pakchoi nitrogen utilization efficiency, decrease 48%-65% nitrogen loss from leaching under the urea continuous applied condition. Biochar also could effectively maintain the content of soil organic matter and base cations. Therefore, it rose up soil pH buffering capacity by 9.4%-36.8% and significantly slowed down acidification rate. It was suggested that 1%-2% addition ratio was recommended from this study when used as similar soil condition.

  5. A model of goal directed vegetable parenting practices

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The aim of this study was to explore factors underlying parents' motivations to use vegetable parenting practices (VPP) using the Model of Goal Directed Vegetable Parenting Practices (MGDVPP) (an adaptation of the Model of Goal Directed Behavior) as the theoretical basis for qualitative interviews. ...

  6. Coevolution of soil and vegetation in the South Eastern Australian uplands with variable climate and fire regimes

    NASA Astrophysics Data System (ADS)

    Inbar, Assaf; Petter, Nyman; Patrick, Lane; Gary, Sheridan

    2016-04-01

    The south east Australian forested uplands are characterized by complex and inter-correlated spatial patterns in forest types, soil depths and fire regimes, even within areas with similar sedimentary geology and catenary position. The ecohydrology of these system-state combinations varies markedly, and is difficult to predict. Here we present preliminary results from a soil and vegetation co-evolutionary framework that represents the key feedbacks that have resulted in the current quasi-equilibrium system states of standing biomass, soil depth and fire frequency. The model is based on a modification of an existing mechanistic model, and includes an ecohydrological engine that drives a vegetation dynamics and a geomorphic submodels. Five sites with similar parent material and slope along a rainfall gradient and opposing aspects were chosen to test the model outputs: soil depth and above-ground biomass. In three of the sites, microclimate conditions were extensively monitored in a clear ridge-top (Open), and North and South facing aspects. The data was used to calibrate and test the ecohydrology modelling according to landscape position. Geomorphic processes that control soil depth were modeled using existing transport functions which varied with climate and forest type, and fire regime was set to be a function of biomass state and water deficit. In the next step, the model will have the potential to be incorporated into a 2D landscape evolution model in order to route sediment and water in a dynamic landscape. Using this model allows us to explore how, and in what rate, did each of the different systems evolve into their current state, and what is the unique and combined part of climate and fire regimes in the coevolution process, and predict the response of the current systems to change in a changing climate.

  7. Exploring field vegetation reflectance as an indicator of soil contamination in river floodplains.

    PubMed

    Kooistra, L; Salas, E A L; Clevers, J G P W; Wehrens, R; Leuven, R S E W; Nienhuis, P H; Buydens, L M C

    2004-01-01

    This study investigated the relation between vegetation reflectance and elevated concentrations of the metals Ni, Cd, Cu, Zn and Pb in river floodplain soils. High-resolution vegetation reflectance spectra in the visible to near-infrared (400-1350 nm) were obtained using a field radiometer. The relations were evaluated using simple linear regression in combination with two spectral vegetation indices: the Difference Vegetation Index (DVI) and the Red-Edge Position (REP). In addition, a multivariate regression approach using partial least squares (PLS) regression was adopted. The three methods achieved comparable results. The best R(2) values for the relation between metals concentrations and vegetation reflectance were obtained for grass vegetation and ranged from 0.50 to 0.73. Herbaceous species displayed a larger deviation from the established relationships, resulting in lower R(2) values and larger cross-validation errors. The results corroborate the potential of hyperspectral remote sensing to contribute to the survey of elevated metal concentrations in floodplain soils under grassland using the spectral response of the vegetation as an indicator. Additional constraints will, however, have to be taken into account, as results are resolution- and location-dependent.

  8. [Distribution and Risk Assessment of Sulfonamides Antibiotics in Soil and Vegetables from Feedlot Livestock].

    PubMed

    Jin, Cai-xia; Si, Xiao-wei; Wang, Zi-ying; Zhang, Qin-wen

    2016-04-15

    Soil and vegetable samples were collected from 13 different livestock farms of different sizes in Xinxiang of China, and the residues of three sulfonamides including sulfadiazine, sulfamonomethoxine, and sulfamethoxazole were analyzed by HPLC with a fluorimetric detector, The results indicated that the total concentration ranges of the three sulfonamides in soil and vegetable were 7.60-176.26 µg · kg⁻¹ and ND-32, 70 µg · kg⁻¹, respectively. The mean concentrations were 70.73 µg · kg⁻¹ and 7.08 µg · kg⁻¹ for soil and vegetables. The residue levels in soil were all lower than the ecotoxic effect trigger value (100 µg · kg⁻¹) set by the Veterinary Medicine International Coordination Commission, indicating the low risk for organisms in soil. The concentrations of three sulfonamides varied significantly in different kinds of vegetables and were all lower than the acceptable daily intake values [50 µg · (kg ·d)⁻¹] set by Joint FAO/WHO Expert CommIttee on Food Additives. But we cannot neglect the potential ecotoxicity and resistance for human via food chain.

  9. [Distribution and Risk Assessment of Sulfonamides Antibiotics in Soil and Vegetables from Feedlot Livestock].

    PubMed

    Jin, Cai-xia; Si, Xiao-wei; Wang, Zi-ying; Zhang, Qin-wen

    2016-04-15

    Soil and vegetable samples were collected from 13 different livestock farms of different sizes in Xinxiang of China, and the residues of three sulfonamides including sulfadiazine, sulfamonomethoxine, and sulfamethoxazole were analyzed by HPLC with a fluorimetric detector, The results indicated that the total concentration ranges of the three sulfonamides in soil and vegetable were 7.60-176.26 µg · kg⁻¹ and ND-32, 70 µg · kg⁻¹, respectively. The mean concentrations were 70.73 µg · kg⁻¹ and 7.08 µg · kg⁻¹ for soil and vegetables. The residue levels in soil were all lower than the ecotoxic effect trigger value (100 µg · kg⁻¹) set by the Veterinary Medicine International Coordination Commission, indicating the low risk for organisms in soil. The concentrations of three sulfonamides varied significantly in different kinds of vegetables and were all lower than the acceptable daily intake values [50 µg · (kg ·d)⁻¹] set by Joint FAO/WHO Expert CommIttee on Food Additives. But we cannot neglect the potential ecotoxicity and resistance for human via food chain. PMID:27548983

  10. Radiostrontium contamination of soil and vegetation within the Semipalatinsk test site.

    PubMed

    Howard, B J; Semioschkina, N; Voigt, G; Mukusheva, M; Clifford, J

    2004-12-01

    The Semipalatinsk nuclear test site (STS) in the Republic of Kazakhstan was an important site for testing atomic bombs and other civil and military nuclear devices of the former Soviet Union. Results are presented from investigations on the extent of radiostrontium contamination in soils and vegetation at the technical areas of the STS, where the tests were conducted and in pastures used by farmers for grazing animals or for hay production. Our data are compared with those reported largely in the recent Russian language literature that has been reviewed. The extent of (90)Sr contamination of soil is highly variable over the STS with the highest values associated with the technical areas, particularly the Degelen mountains. Recently measured values in both the present data and the Russian language literature confirm the relatively high current contamination of soil and vegetation in the vicinity of tunnels and associated watercourses in the Degelen area. The proportion of (90)Sr in soil which could not be extracted with 6 M HCl was only an average of 20%, which is low compared to other test site areas and possibly indicates a relatively high mobility in this area, because the (90)Sr is derived from leakage from explosion tunnels along watercourses rather than being associated with fused silicates. A comparison of relative activity concentrations in soil and vegetation suggests that the transfer of (90)Sr to vegetation on the STS is high compared to that of (137)Cs and plutonium. PMID:15645315

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

    PubMed

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

    2012-02-01

    Lead (Pb) contents and partition in soils collected from eleven vegetable-growing lands in Fujian Province, China, were investigated using a modification of the BCR (Community Bureau of Reference) sequential extraction procedure coupled with the Pb isotope ratio technique. Pb contents in Chinese white cabbage (B. Chinensis L.) grown on the lands for this study were also measured. Results showed that Pb concentrations in fifty samples of topsoil ranged from 456 to 21.5 mg kg(-1), with each mean concentration of six sampling lands exceeding the national standard (50 mg kg(-1)); while Pb concentrations in edible portions of thirty-two vegetable samples ranged from 0.009 to 2.20 mg kg(-1), with four sampling sites exceeding the national sanitary standard (0.2 mg kg(-1)). A significant correlation (r = 0.971, P < 0.01) of Pb contents in the acid-extractable fractions by BCR approach and the vegetables was observed, which indicates that the acid-extractable Pb is useful for evaluating the metal bioavailability for plants and potential risk for human health in soils. The determination of lead isotope ratios in different chemical forms of soils by BCR sequential extraction procedures provides useful information on the Pb isotopic composition associated with different soil fractions (especially in the acid-extractable fractions), and the result is helpful for the further study on controlling and reducing Pb contamination in vegetable-growing soils.

  12. Effects of vegetation on soil moisture distribution and flux with implications for the global hydrologic cycle

    NASA Technical Reports Server (NTRS)

    Macari, Emir Jose

    1991-01-01

    Recent climate modeling experiments have identified the critical need for a better understanding of land surface - atmosphere interactions. An important issue in global climate modeling is to be able to relate land surface and atmospheric processes. In the past this link has been inadequately represented due to the lack of understanding of the interaction between the processes and also due to the large spatial variability of the hydrological and soil properties. A project was initiated at the Marshall Space Flight Center (MSFC) in FY-90 under the Center's Directorate Discretionary Fund (CDDF) to study small-scale effects of vegetation on the distribution and fluxes of soil moisture. Installation of a large array of instruments was accomplished during that first year (FY-90). During this second year of the project, the instrumentation and data collection systems were improved and data has begun to be taken. Preliminary analysis of the data show that the equipment has been functioning properly. Some of the preliminary results that have recently been analyzed are given.

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

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

    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.

  14. Estimating root-zone soil moisture in the West Africa Sahel using remotely sensed rainfall and vegetation

    NASA Astrophysics Data System (ADS)

    McNally, Amy L.

    Agricultural drought is characterized by shortages in precipitation, large differences between actual and potential evapotranspiration, and soil water deficits that impact crop growth and pasture productivity. Rainfall and other agrometeorological gauge networks in Sub-Saharan Africa are inadequate for drought early warning systems and hence, satellite-based estimates of rainfall and vegetation greenness provide the main sources of information. While a number of studies have described the empirical relationship between rainfall and vegetation greenness, these studies lack a process based approach that includes soil moisture storage. In Chapters I and II, I modeled soil moisture using satellite rainfall inputs and developed a new method for estimating soil moisture with NDVI calibrated to in situ and microwave soil moisture observations. By transforming both NDVI and rainfall into estimates of soil moisture I was able to easily compare these two datasets in a physically meaningful way. In Chapter II, I also show how the new NDVI derived soil moisture can be assimilated into a water balance model that calculates an index of crop water stress. Compared to the analogous rainfall derived estimates of soil moisture and crop stress the NDVI derived estimates were better correlated with millet yields. In Chapter III, I developed a metric for defining growing season drought events that negatively impact millet yields. This metric is based on the data and models used in the Chapters I and II. I then use this metric to evaluate the ability of a sophisticated land surface model to detect drought events. The analysis showed that this particular land surface model's soil moisture estimates do have the potential to benefit the food security and drought early warning communities. With a focus on soil moisture, this dissertation introduced new methods that utilized a variety of data and models for agricultural drought monitoring applications. These new methods facilitate a more

  15. Effect of land-use practice on soil moisture variability for soils covered with dense forest vegetation of Puerto Rico

    NASA Technical Reports Server (NTRS)

    Tsegaye, T.; Coleman, T.; Senwo, Z.; Shaffer, D.; Zou, X.

    1998-01-01

    Little is known about the landuse management effect on soil moisture and soil pH distribution on a landscape covered with dense tropical forest vegetation. This study was conducted at three locations where the history of the landuse management is different. Soil moisture was measured using a 6-cm three-rod Time Domain Reflectometery (TDR) probe. Disturbed soil samples were taken from the top 5-cm at the up, mid, and foothill landscape position from the same spots where soil moisture was measured. The results showed that soil moisture varies with landscape position and depth at all three locations. Soil pH and moisture variability were found to be affected by the change in landuse management and landscape position. Soil moisture distribution usually expected to be relatively higher in the foothill (P3) area of these forests than the uphill (P1) position. However, our results indicated that in the Luquillo and Guanica site the surface soil moisture was significantly higher for P1 than P3 position. These suggest that the surface and subsurface drainage in these two sites may have been poor due to the nature of soil formation and type.

  16. Soil, water, and vegetation conditions in South Texas

    NASA Technical Reports Server (NTRS)

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

    1976-01-01

    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.

  17. Effects of vegetation on radon transport processes in soil

    SciTech Connect

    Borak, T.B.

    1991-02-01

    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.

  18. Modeling biogeochemistry in agricultural soils

    SciTech Connect

    Li, C.; Frolking, S.; Harriss, R.

    1994-09-01

    An existing model of C and N dynamics in soils was supplemented with a plant growth submodel and cropping practice routines (fertilization, irrigation, tillage, crop rotation, and manure amendments) to study the biogeochemistry of soil carbon in arable lands. The new model was validated against field results for short-term (1-9 years) decomposition experiments, the seasonal pattern of soil CO{sub 2} respiration, and long-term (100 years) soil carbon storage dynamics. A series of sensitivity runs investigated the impact of varying agricultural practices on soil organic carbon (SOC) sequestration. The tests were simulated for corn (maize) plots over a range of soil and climate conditions typical of the United States. The largest carbon sequestration occurred with manure additions; the results were very sensitive to soil texture (more clay led to greater sequestration). Increased N fertilization generally enhanced carbon sequestration, but the results were sensitive to soil texture, initial soil carbon content, and annual precipitation. Reduced tillage also generally (but not always) increased SOC content, through the results were very sensitive to soil texture, initial SOC content, and annual precipitation. A series of long-term simulations investigated the SOC equilibrium for various agricultural practices, soil and climate conditions, and crop rotations. Equilibrium SOC content increased with decreasing temperatures, increasing clay content, enhanced N fertilization, manure amendments, and crops with higher residue yield. Time to equilibrium appears to be one hundred to several hundred years. In all cases, equilibration time was longer for increasing SOC content than for decreasing SOC content. Efforts to enhance carbon sequestration in agricultural soils would do well to focus on those specific areas and agricultural practices with the greatest potential for increasing soil carbon content. 64 refs., 13 figs., 5 tabs.

  19. The Effects of Topography, Vegetation and Soil Properties on Hillslope Hydrology in Northeastern Brazil

    NASA Astrophysics Data System (ADS)

    Fernandes, N.; Franklin, M. R.; Mota, P.

    2015-12-01

    Soil water dynamics, especially on hillslopes, is mainly controlled by conditions defined by topography, climate, vegetation cover and soil properties. In many areas of northeastern Brazil, semi-arid tropical soils are being rapidly modified by land-use changes which usually lead to a decrease in infiltration rates and to an increase in surface runoff and soil erosion, as well as to a reduction in groundwater recharge. This study focus on the effects of these land-use changes on the main hydrological processes close to the soil surface, especially on the soil infiltration rates and hillslope hydrology dynamics on highly weathered thick tropical soils at the southwestern portion of the Bahia state. The Caetité experimental basin (CEB) presents portions with natural savanna, agriculture, grazing, as well as those resulting from a uranium mining and milling activities. The watershed (75 km2) has an average total annual rainfall is about 710 mm, with a long dry period. Bedrock is comprised by gneisses and granites with a gentle topography covered by thick (>3m) soils. In order to assess the role played by topography, soil properties and vegetation cover in controlling soil water infiltration and redistribution along a typical hillslope, 6 soil matrix potential nests (SMPN) were installed along a 1.4 km long transect. Each nest is composed by 7 soil matrix potential sensors (installed up to 3.0 m depth), 1 soil temperature sensor and a datalogger. In parallel, field experiments were carried out at different points of the CEB in order to estimate soil infiltration rates and field-saturated hydraulic conductivities. At these points, undisturbed soil samples were collected to characterize soil texture, porosity (micro and macro), bulk density, as well as to define the soil water retention curves. The results show that dense savanna presents the highest infiltration capacity values, independently of soil and topography conditions. Besides, maximum infiltration rates may be

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

    USGS Publications Warehouse

    Jorgenson, M. Torre; Harden, Jennifer; Kanevskiy, Mikhail; O'Donnell, Jonathan; Wickland, Kim; Ewing, Stephanie; Manies, Kristen; Zhuang, Qianlai; Shur, Yuri; Striegl, Robert; Koch, Josh

    2013-01-01

    The diversity of ecosystems across boreal landscapes, successional changes after disturbance and complicated permafrost histories, present enormous challenges for assessing how vegetation, water and soil carbon may respond to climate change in boreal regions. To address this complexity, we used a chronosequence approach to assess changes in vegetation composition, water storage and soil organic carbon (SOC) stocks along successional gradients within four landscapes: (1) rocky uplands on ice-poor hillside colluvium, (2) silty uplands on extremely ice-rich loess, (3) gravelly–sandy l