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1

A nonlinear coupled soil moisture-vegetation model  

NASA Astrophysics Data System (ADS)

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.

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

2005-06-01

2

[Soil moisture estimation model based on multiple vegetation index].  

PubMed

Estimating soil moisture conveniently and exactly is a hot issues in water resource monitoring among agriculture and forestry. Estimating soil moisture based on vegetation index has been recognized and applied widely. 8 vegetation indexes were figured out based on the hyper-spectral data measured by portable spectrometer. The higher correlation indexes among 8 vegetation indexes and surface vegetation temperature were selected by Gray Relative Analysis method (GRA). Then, these selected indexes were analyzed using Multiple Linear Regression to establish soil moisture estimation model based on multiple vegetation indexes, and the model accuracy was evaluated. The accuracy evaluation indicated that the fitting was satisfied and the significance was 0.000 (P < 0.001). High correlation was turned out between estimated and measured soil moisture with R2 reached 0.636 1 and RMSE 2.149 9. This method introduced multiple vegetation indexes into soil water content estimating over micro scale by non-contact measuring method using portable spectrometer. The exact estimation could be an appropriate replacement for remote sensing inversion and direct measurement. The model could estimate soil moisture quickly and accurately, and provide theory and technology reference for water resource management in agriculture and forestry. PMID:25358174

Wu, Hai-long; Yu, Xin-xiao; Zhang, Zhen-ming; Zhang, Yan

2014-06-01

3

Modeling of state of vegetation and soil erosion over large areas  

Microsoft Academic Search

A vegetation-erosion model was developed to assess the extent of soil erosion and development trend of vegetation in the context of existing and contemplated vegetation-based soil erosion controls under different climatic, topographical and soil conditions. The model recognizes four vegetation-mediated soil erosion states: (i) an expanding vegetation coverage coupled with reduced erosion (C), (ii) a deteriorating vegetation coverage coupled with

Zhao-Yin WANG; Guangqian WANG; Guohe HUANG

2008-01-01

4

Modeling vegetation coverage and soil erosion in the Loess Plateau Area of China  

Microsoft Academic Search

Soil erosion is still one of major issues limiting agricultural and forestry productivity in Loess Plateau of China. Vegetation plays an important role in controlling soil erosion, but studies on modeling dynamics of vegetation and soil erosion and interaction between them were hardly reported. We hypothesized that changes of vegetation coverage and soil erosion as affected by climate factors and

Z. C. Zhou; Z. P. Shangguan; D. Zhao

2006-01-01

5

Vegetation Dynamics And Soil Moisture: Consequences For Hydrologic Modeling  

NASA Astrophysics Data System (ADS)

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.

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

2007-12-01

6

Modeling radium and radon transport through soil and vegetation  

USGS Publications Warehouse

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.

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

2003-01-01

7

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...

8

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

E-print Network

in water-limited environments with significant water recycling, and introduce a simple process modelA model for soil-vegetation-atmosphere interactions in water-limited ecosystems M. Baudena,1,2 F. D-vegetation-atmosphere interactions in water-limited ecosystems, Water Resour. Res., 44, W12429, doi:10.1029/2008WR007172. 1

D'Andrea, Fabio

9

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

10

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

11

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

12

A generalized soil-adjusted vegetation index  

Microsoft Academic Search

Operational monitoring of vegetative cover by remote sensing currently involves the utilisation of vegetation indices (VIs), most of them being functions of the reflectance in red (R) and near-infrared (NIR) spectral bands. A generalized soil-adjusted vegetation index (GESAVI), theoretically based on a simple vegetation canopy model, is introduced. It is defined in terms of the soil line parameters (A and

M. A. Gilabert; J. Gonzalez-Piqueras; F. J. Garcõ ´ a-Haro; J Meliá

2002-01-01

13

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

PubMed

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. PMID:25475118

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

2015-02-01

14

Vegetation controls on soil hydraulic properties and implications for the hydrologic variability of soils: observations and modeling  

NASA Astrophysics Data System (ADS)

Soil properties and their associated spatial structure exert major controls on the storage and fluxes of water through surface soils and provide habitat and resources for life in the critical zone. Moreover it has been observed that a range of biotic processes are responsible for the formation and maintenance of these properties. For instance the build up of organic matter in soils can affect the water retention properties, particularly in coarse soils. This observation leads to the compelling possibility that the action of vegetation on its soil environment alters the hydrologic variability of soil, with consequences (positive and negative) for plant functions. This alteration was examined in four semi-arid ecosystems in southern Arizona using a combination of field data collection and modeling. It was expected that the extent and direction of biotic alteration would be dependent on the other factors determining soil formation, particularly the climate, lithology and landscape position. Controlling for the latter of these, soil samples were collected in the mid-slope sections of four north-facing hillslopes encompassing two lithologies and two climates. The effects of vegetation were examined by collecting paired samples from below and between woody-plant canopies. Samples were analyzed for their composition and hydraulic properties, including organic matter content, water retention, and permeability. The results demonstrate that the build-up of organic matter under vegetation can significantly alter soil hydraulic properties over small spatial scales. The effects of this alteration on the hydrologic variability of the soils, and the implications for vegetation water stress and nutrient cycling, will be examined using a simple model of soil-plant-atmosphere interactions.

Harman, C. J.; Lohse, K. A.; Troch, P. A.; Sivapalan, M.

2010-12-01

15

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

16

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

17

Spatial variability models of soil respiration from some vegetation types in Maritime Antarctica  

Microsoft Academic Search

Soil respiration is an important part of the terrestrial carbon cycling and is influenced by several aspects, such as type and distribution of vegetation. In this work we evaluated the spatial variability of the soil respiration (or soil CO2 emission) in three sites located in Maritime Antarctica at Admiralty Bay, King George Island under contrasting vegetation, representative of this region:

Newton La Scala Jr.; Eduardo S. Mendonça; Alan Rodrigo Panosso; Felipe N. Dimas; Carlos Eduardo G. Schaefer

2010-01-01

18

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

USGS Publications Warehouse

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

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

2003-01-01

19

Modeling temporal and large-scale spatial variability of soil respiration from soil water availability, temperature and vegetation productivity indices  

NASA Astrophysics Data System (ADS)

Field-chamber measurements of soil respiration from 17 different forest and shrubland sites in Europe and North America were summarized and analyzed with the goal to develop a model describing seasonal, interannual and spatial variability of soil respiration as affected by water availability, temperature, and site properties. The analysis was performed at a daily and at a monthly time step. With the daily time step, the relative soil water content in the upper soil layer expressed as a fraction of field capacity was a good predictor of soil respiration at all sites. Among the site variables tested, those related to site productivity (e.g., leaf area index) correlated significantly with soil respiration, while carbon pool variables like standing biomass or the litter and soil carbon stocks did not show a clear relationship with soil respiration. Furthermore, it was evidenced that the effect of precipitation on soil respiration stretched beyond its direct effect via soil moisture. A general statistical nonlinear regression model was developed to describe soil respiration as dependent on soil temperature, soil water content, and site-specific maximum leaf area index. The model explained nearly two thirds of the temporal and intersite variability of soil respiration with a mean absolute error of 0.82 ?mol m-2 s-1. The parameterized model exhibits the following principal properties: (1) At a relative amount of upper-layer soil water of 16% of field capacity, half-maximal soil respiration rates are reached. (2) The apparent temperature sensitivity of soil respiration measured as Q10 varies between 1 and 5 depending on soil temperature and water content. (3) Soil respiration under reference moisture and temperature conditions is linearly related to maximum site leaf area index. At a monthly timescale, we employed the approach by [2002] that used monthly precipitation and air temperature to globally predict soil respiration (T&P model). While this model was able to explain some of the month-to-month variability of soil respiration, it failed to capture the intersite variability, regardless of whether the original or a new optimized model parameterization was used. In both cases, the residuals were strongly related to maximum site leaf area index. Thus, for a monthly timescale, we developed a simple T&P&LAI model that includes leaf area index as an additional predictor of soil respiration. This extended but still simple model performed nearly as well as the more detailed time step model and explained 50% of the overall and 65% of the site-to-site variability. Consequently, better estimates of globally distributed soil respiration should be obtained with the new model driven by satellite estimates of leaf area index. Before application at the continental or global scale, this approach should be further tested in boreal, cold-temperate, and tropical biomes as well as for non-woody vegetation.

Reichstein, Markus; Rey, Ana; Freibauer, Annette; Tenhunen, John; Valentini, Riccardo; Banza, Joao; Casals, Pere; Cheng, Yufu; Grünzweig, Jose M.; Irvine, James; Joffre, Richard; Law, Beverly E.; Loustau, Denis; Miglietta, Franco; Oechel, Walter; Ourcival, Jean-Marc; Pereira, Joao S.; Peressotti, Alessandro; Ponti, Francesca; Qi, Ye; Rambal, Serge; Rayment, Mark; Romanya, Joan; Rossi, Federica; Tedeschi, Vanessa; Tirone, Giampiero; Xu, Ming; Yakir, Dan

2003-12-01

20

Vegetation and soils  

USGS Publications Warehouse

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

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

2000-01-01

21

Modeling Vegetation as a Dynamic COMPONENT in Soil-Vegetation TRANSFER Schemes and Hydrological Models  

NASA Astrophysics Data System (ADS)

Vegetation affects the climate by modifying the energy, momentum, and hydrologic balance of the land surface. Soil-vegetation-atmosphere transfer (SVAT) schemes explicitly consider the role of vegetation in affecting water and energy balance by taking into account its physiological properties, in particular, leaf area index (LAI) and stomatal conductance. These two physiological properties are also the basis of evapotranspiration parameterizations in physically based hydrological models. However, most current SVAT schemes and hydrological models do not parameterize vegetation as a dynamic component. The seasonal evolution of LAI is prescribed, and monthly LAI values are kept constant year after year. The effect of CO2 on the structure and physiological properties of vegetation is also neglected, which is likely to be important in transient climate simulations with increasing CO2 concentration and for hydrological models that are used to study climate change impact. The net carbon uptake by vegetation, which is the difference between photosynthesis and respiration, is allocated to leaves, stems, and roots. Carbon allocation to leaves determines their biomass and LAI. The timing of bud burst, leaf senescence, and leaf abscission (i.e., the phenology) determines the length of the growing season. Together, photosynthesis, respiration, allocation, and phenology, which are all strongly dependent on environmental conditions, make vegetation a dynamic component. This paper (1) familiarizes the reader with the basic physical processes associated with the functioning of the terrestrial biosphere using simple nonbiogeochemical terminology, (2) summarizes the range of parameterizations used to model these processes in the current generation of process-based vegetation and plant growth models and discusses their suitability for inclusion in SVAT schemes and hydrological models, and (3) illustrates the manner in which the coupling of vegetation models and SVAT schemes/hydrological models may be accomplished.

Arora, Vivek

2002-05-01

22

Using Distributed-Hydrology-Soil-Vegetation Model to Study Road Effects on Stream flow and Soil Moisture  

NASA Astrophysics Data System (ADS)

The distributed-hydrology-soil-vegetation model (DHSVM) was applied in Pang Khum Experimental Watershed (PKEW), located near 19.05\\deg N, 98.65\\deg E in the mountainous region of northern Thailand, headwaters of the Chao Phraya River system. PKEW has a highly seasonal rainfall regime, with 90% of the annual 1200-1400 mm rainfall occurring during the southwest summer monsoon. The elevation of PKEW ranges from approximately 1100 to 1500 m. Total road area including road banks is about 1.2% of the basin area. About 57% of the road area occurs on slopes steeper than 10%. All roads are unpaved. Land cover in PKEW is affected by swidden agriculture. Six land cover and nine soil classes are identified in the basin. We have been working in the area since 1997 as part of the Thailand Roads Project (TRP). Within the basin, we are monitoring microclimate at two sites, soil moisture at four sites, and rainfall at five sites. Streamflow is measured at the outlet. Based on digital elevation data, DHSVM explicitly accounts for the spatial distribution of the stream and road networks, soil depth, soil and vegetation types. The model run period, including warm up, calibration and validation, is from August 1997 to January 2001. Field measurements provide forcing data, calibration data, and guidance in parameter selection. Model calibration and validation were done by aggregating simulated hourly soil moisture and stream flow into daily values and comparing them with aggregated daily measurements. For the calibration period, RMSEs of soil moisture and streamflow were lower than the observed variability as represented by the standard deviation, median absolute deviation, and (for stream flow) interquartile range. Model performance drops in validation period, but RMSEs remain near or lower than observed variability. We ran DHSVM with and without roads to examine their effects. Significant effects of roads were found despite the very low proportion of the watershed covered by roads and road banks. Streamflow for road and non-road cases was significantly different (p < 0.0001) based on the Wilcoxon signed rank test. In general, roads increase peak volume for short, intense storms, but reduced whole-period discharge by about 5.5%. Soil moisture was affected in cells where roads occur. In cells where water exited the road onto the hillslope, soil moisture was higher than it was without the road. In cells with roads, but without water flowing onto the hillslope, soil moisture was higher in some cases and lower in others.

Cuo, L.; Giambelluca, T. W.; Ziegler, A. D.; Nullet, M. A.

2003-12-01

23

A snow-soil-vegetation-atmosphere transfer/radiobrightness model for wet snow  

NASA Astrophysics Data System (ADS)

Snow pack models like SNTHERM predict snow behavior very well during the cold periods but do not adequately capture liquid and vapor transport between soil and snow during the snowmelt period. To get a more realistic description of the snowpack and soil dynamics, I have developed a Snow-Soil-Vegetation-Atmosphere Transfer/Radiobrightness (SSVAT) model, which couples the Land Surface Processes (LSP) model with SNTHERM. I also developed an associated Radiobrightness model based on pendular rings that describes the microwave brightness signatures. Late winter/early spring comparisons with data show that SSVAT provided better estimates of heat fluxes, temperatures, grain sizes and densities in snow and soil than did SNTHERM. The SSVAT model predicted conditions for depth hoar in snow caused by vapor transport from soil. The SSVAT model could employ five-minute interval forcings for routine applications and two-minute interval forcings for research applications whereas SNTHERM requires a ten-minute, or longer, time resolution to avoid divergence. A sensitivity study suggests that the thatch at the snow/soil interface can be ignored for thick snowpacks. The Radiobrightness model was simulated at lower microwave frequencies where brightness temperatures can be estimated without considering scattering. The Radiobrightness model includes liquid water in the shape of pendular rings of an appropriate size, shape and number density, as indicated by the SSVAT model. Results show that moisture in pendular rings was a more effective absorber than equivalent moisture in spheres. The brightness temperatures of wet snow are governed by loss from water absorbers and by the dielectric contrast at the snow/soil interface. The underestimation in SSVAT based brightness temperature may be caused by the underestimation of the liquid moisture content. For an open canopy like that at CLPX'03, emission from the surrounding trees will cause a brightening. SSVAT/R provided a framework for exploring the soil-snow mechanism which is considerable interest since it plays an important role in the spring known to be influenced by water flow in snow and soil. If the melt-refreeze cycle is accurately simulated by the snow model, the darkening brightness due to increased grain size from melt-refreezing would not be mistaken for a signal of increased snow depth.

Chung, Yi-Ching

24

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

25

Levels of tritium in soils and vegetation near Canadian nuclear facilities releasing tritium to the atmosphere: implications for environmental models.  

PubMed

Concentrations of organically bound tritium (OBT) and tritiated water (HTO) were measured over two growing seasons in vegetation and soil samples obtained in the vicinity of four nuclear facilities and two background locations in Canada. At the background locations, with few exceptions, OBT concentrations were higher than HTO concentrations: OBT/HTO ratios in vegetation varied between 0.3 and 20 and values in soil varied between 2.7 and 15. In the vicinity of the four nuclear facilities OBT/HTO ratios in vegetation and soils deviated from the expected mean value of 0.7, which is used as a default value in environmental transfer models. Ratios of the OBT activity concentration in plants ([OBT]plant) to the OBT activity concentration in soils ([OBT]soil) appear to be a good indicator of the long-term behaviour of tritium in soil and vegetation. In general, OBT activity concentrations in soils were nearly equal to OBT activity concentrations in plants in the vicinity of the two nuclear power plants. [OBT]plant/[OBT]soil ratios considerably below unity observed at one nuclear processing facility represents historically higher levels of tritium in the environment. The results of our study reflect the dynamic nature of HTO retention and OBT formation in vegetation and soil during the growing season. Our data support the mounting evidence suggesting that some parameters used in environmental transfer models approved for regulatory assessments should be revisited to better account for the behavior of HTO and OBT in the environment and to ensure that modelled estimates (e.g., plant OBT) are appropriately conservative. PMID:25461522

Thompson, P A; Kwamena, N-O A; Ilin, M; Wilk, M; Clark, I D

2015-02-01

26

Vegetation and soil respiration: Correlations and controls  

Microsoft Academic Search

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

James W. Raich; Aydin Tufekciogul

2000-01-01

27

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

28

Two models to compute an adjusted Green Vegetation Fraction taking into account the spatial variability of soil NDVI  

NASA Astrophysics Data System (ADS)

The green vegetation fraction (Fg) is an important climate and hydrologic model parameter. The commonly- used Fg model is a simple linear mixing of two NDVI end-members: bare soil NDVI (NDVIo) and full vegetation NDVI (NDVI?). NDVI? is generally set as a percentile of the historical maximum NDVI for each land cover. This approach works well for areas where Fg reaches full cover (100%). Because many biomes do not reach Fg=0, however, NDVIo is often determined as a single invariant value for all land cover types. In general, it is selected among the lowest NDVI observed over bare or desert areas, yielding NDVIo close to zero. There are two issues with this approach: large-scale variability of soil NDVI is ignored and observations on a wide range of soils show that soil NDVI is often larger. Here we introduce and test two new approaches to compute Fg that takes into account the spatial variability of soil NDVI. The first approach uses a global soil NDVI database and time series of MODIS NDVI data over the conterminous United States to constrain possible soil NDVI values over each pixel. Fg is computed using a subset of the soils database that respects the linear mixing model condition NDVIo?NDVIh, where NDVIh is the pixel historical minimum. The second approach uses an empirical soil NDVI model that combines information of soil organic matter content and texture to infer soil NDVI. The U.S. General Soil Map (STATSGO2) database is used as input for spatial soil properties. Using in situ measurements of soil NDVI from sites that span a range of land cover types, we test both models and compare their performance to the standard Fg model. We show that our models adjust the temporal Fg estimates by 40-90% depending on the land cover type and amplitude of the seasonal NDVI signal. Using MODIS NDVI and soil maps over the conterminous U.S., we also study the spatial distribution of Fg adjustments in February and June 2008. We show that the standard Fg method overestimates Fg for a large part of the United States, with the largest over-estimation (up to 0.2) in the areas where 0.2

Montandon, L. M.; Small, E.

2008-12-01

29

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

30

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

SciTech Connect

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.

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

2014-06-01

31

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

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

32

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

33

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)

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.

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

2014-11-01

34

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

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

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

2013-01-01

35

Development of a fully-distributed daily hydrologic feedback model addressing vegetation, land cover, and soil water dynamics (VELAS)  

NASA Astrophysics Data System (ADS)

A simple hydrologic feedback model has been developed to simulate daily responses of hydrologic processes including interception, runoff, evapotranspiration, infiltration, and recharge under various conditions of vegetation, land cover, and soil in a fully-distributed manner. The daily soil water balance is a key element to link surface and subsurface models as it calculates infiltration and groundwater recharge by considering a time delay routing through a vadose zone down to the groundwater table. MODFLOW is adopted to simulate groundwater flow and interaction with surface water components as well. The model also can easily be localized by simple modification of soil and crop properties. The actual application of the model for a watershed in the Geum River Basin in Korea showed reliable hydrologic feedbacks between the surface and subsurface hydrologic systems.

Park, Changhui; Lee, Jejung; Koo, Min-Ho

2013-06-01

36

Modelling temporal and large-scale spatial variability of soil respiration from soil water availability, temperature and vegetation productivity indices  

NASA Astrophysics Data System (ADS)

Field-chamber measurements of soil respiration from 17 different forest and shrubland sites in Europe and North America were summarized and analyzed with the goal to develop a model describing seasonal, inter-annual and spatial variability of soil respiration as affected by water availability, temperature and site properties. The analysis was performed at a daily and at a monthly time step. With the daily time step, the relative soil water content in the upper soil layer expressed as a fraction of field capacity was a good predictor of soil respiration at all sites. Among the site variables tested, those related to site productivity (e.g. leaf area index) correlated significantly with soil respiration, while carbon pool variables like standing biomass or the litter and soil carbon stocks did not show a clear relationship with soil respiration. Furthermore, it was evidenced that the effect of precipitation on soil respiration stretched beyond its direct effect via soil moisture. A general statistical non-linear regression model was developed to describe soil respiration as dependent on soil temperature, soil water content and site-specific maximum leaf area index. The model explained nearly two thirds of the temporal and inter-site variability of soil respiration with a mean absolute error of 0.82 µmol m-2 s-1. The parameterised model exhibits the following principal properties: 1) At a relative amount of upper-layer soil water of 16% of field capacity half-maximal soil respiration rates are reached. 2) The apparent temperature sensitivity of soil respiration measured as Q10 varies between 1 and 5 depending on soil temperature and water content. 3) Soil respiration under reference moisture and temperature conditions is linearly related to maximum site leaf area index. At a monthly time-scale we employed the approach by Raich et al. (2002, Global Change Biol. 8, 800-812) that used monthly precipitation and air temperature to globally predict soil respiration (T&P-model). While this model was able to explain some of the month-to-month variability of soil respiration, it failed to capture the inter-site variability, regardless whether the original or a new optimized model parameterization was used. In both cases, the residuals were strongly related to maximum site leaf area index. Thus, for a monthly time scale we developed a simple T&P&LAI-model that includes leaf area index as an additional predictor of soil respiration. This extended but still simple model performed nearly as well as the more detailed time-step model and explained 50 % of the overall and 65% of the site-to-site variability. Consequently, better estimates of globally distributed soil respiration should be obtained with the new model driven by satellite estimates of leaf area index.

Reichstein, M.; Rey, A.; Freibauer, A.; Tenhunen, J.; Valentini, R.; Soil Respiration Synthesis Team

2003-04-01

37

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

38

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

SciTech Connect

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.

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

1993-06-01

39

Modeling temporal and large-scale spatial variability of soil respiration from soil water availability, temperature and vegetation productivity indices  

Microsoft Academic Search

Field-chamber measurements of soil respiration from 17 different forest and shrubland sites in Europe and North America were summarized and analyzed with the goal to develop a model describing seasonal, interannual and spatial variability of soil respiration as affected by water availability, temperature, and site properties. The analysis was performed at a daily and at a monthly time step. With

Markus Reichstein; Ana Rey; Annette Freibauer; John Tenhunen; Riccardo Valentini; Joao Banza; Pere Casals; Yufu Cheng; Jose M. Grünzweig; James Irvine; Richard Joffre; Beverly E. Law; Denis Loustau; Franco Miglietta; Walter Oechel; Jean-Marc Ourcival; Joao S. Pereira; Alessandro Peressotti; Francesca Ponti; Ye Qi; Serge Rambal; Mark Rayment; Joan Romanya; Federica Rossi; Vanessa Tedeschi; Giampiero Tirone; Ming Xu; Dan Yakir

2003-01-01

40

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

SciTech Connect

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

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

2010-01-29

41

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)

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 term is added to Richards' equation at the bottom of the column to model groundwater discharge to streams. Contrary to what has already been proposed (Liang et al., Journal of Geophysical Research, 1994; Yeh and Eltahir, Journal of Climate, 2005; Niu et al., Journal of Geophysical Research, 2007), this sink term is deduced from Darcy's law and Van Genuchten's relationships. Through the approximation of a linear groundwater table profile in two dimensions, a differential equation of the water table depth at a fixed distance from the river has been determined. It depends on topographic and soil parameters, and on the distance between the stream and the modelled column. Different types of soil and climate forcing (especially precipitations) have been tested in the above framework. Comparisons between the 2D reference model and a few 1D columns show good agreement in water table depth and evapotranspiration fluxes. This justifies using an equivalent column to replace the set of independent columns, with respect to evapotranspiration fluxes.

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

2014-05-01

42

Calibrating a soil-vegetation-atmosphere transfer model with remote sensing estimates of surface temperature and soil surface moisture in a semi arid environment  

NASA Astrophysics Data System (ADS)

SummaryA series of numerical experiments has been designed to investigate how effective satellite estimates of radiometric surface temperatures and soil surface moisture are for calibrating a Soil-Vegetation-Atmosphere Transfer (SVAT) model. Multi-objective calibration based on error minimization of temperature and soil moisture model outputs is performed in a semi-arid environment. Model accuracy when calibrated using in situ versus satellite objectives is explored in detail. Observational meteorological datasets from the African Monsoon Multidisciplinary Analysis (AMMA) were used to force a column model during a growing season in Mali. Fourier Amplitude Sensitivity Test (FAST) revealed the most sensitive parameters to model outputs. Parameters found sensitive were subsequently optimized in a series of model calibrations to reveal trade-offs between model objectives. Our main findings are (1) the SVAT model performs well in the semi-arid environment, but underestimates peak growing season evapotranspiration and overestimates soil moisture, (2) most of the parameters important for flux estimates can be constrained using surface temperature and soil surface moisture with the three exceptions: root depth, the extinction coefficient and unstressed stomatal resistance, (3) flux simulations are improved when the model is calibrated using in situ surface temperature and soil surface moisture versus satellite estimates.

Ridler, Marc E.; Sandholt, Inge; Butts, Michael; Lerer, Sara; Mougin, Eric; Timouk, Franck; Kergoat, Laurent; Madsen, Henrik

2012-05-01

43

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

44

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

E-print Network

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

Flores, Alejandro N.

45

Stochastic generation of meteorological variables and effects on global models of water and carbon cycles in vegetation and soils  

NASA Astrophysics Data System (ADS)

Global models of water and carbon cycles in continental vegetation and soils are usually forced with monthly mean climatic data-sets and thus neglect day to day variations of the weather. This treatment may be justified for empirical models based on parametrizations validated at a monthly timescale. Mechanistic models handling hydrological and biological processes at much shorter timescales might, however, be largely affected by such an approximation, since the various processes described are highly nonlinear. A random generator of daily precipitations and temperatures applicable at the global scale has thus been developed from worldwide meteorological data covering 6 years of observations. The probability of a wet day is correlated to the weather encountered the previous day. The amount of precipitation, the daily mean temperature and the diurnal range of temperature are described from the statistical point of view by the cumulative distribution functions (CDF) of three random variables. The CDFs relative to temperatures are different for rainy and dry days. This stochastically generated weather field is used as input to IBM (Improved Bucket Model) and CARAIB (CARbon Assimilation In the Biosphere), two global models of respectively soil hydrology and vegetation productivity. Large differences in both the geographical distribution and the global value of soil water, vegetation productivity and carbon stocks are obtained between the model runs using monthly uniform weather on one side and randomly generated weather on the other. The main contribution to this difference at the global scale arises from the precipitation generation occurring as a result of high degree of nonlinearity of the interception scheme used in IBM.

Hubert, B.; Francois, L.; Warnant, P.; Strivay, D.

1998-12-01

46

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

NASA Astrophysics Data System (ADS)

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 been established in the last five years. Simulations results showed that, along south-facing slopes, ET and Bag did not decrease with elevation, as it happens along north facing slopes, but showed a maximum at an intermediate elevation around ca. 1500 m a.s.l., because of the contrasting trends of a shorter vegetation season at higher elevations and water stress at lower elevations. Therefore, results suggest that in this region south-facing pastures and woodlands below the elevation band of 1000 - 1500 m a.s.l. are the locations exposed to more frequent water stress conditions. Future climate change will likely worsen drought frequency. This contribution highlights that the collected data set permits a multi-scale and multi-process evaluation of the model. Plot scale observations of evapotranspiration, soil moisture and snow cover, combined with remote sensing observations of snow and soil moisture help to discriminate between uncertainties in input data (i.e. snow/rainfall partitioning) and model parameterization. Moreover, we want to show with practical examples how, when dealing with coupled process-based eco-hydrological models is essential considering the physical consistency between different processes as modeled in GEOtop. For example, accounting the role of subsurface water lateral distribution on surface soil moisture; considering both water and energy budget constrains; introducing the control of snow cover on vegetation phenology. This introduces additional constraints in model parameterization that allow a better understanding of some processes dynamics, and can lead to a more coherent and accurate estimation of the catchment hydrological behavior than the one, which is possible with simpler models.

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

47

Preliminary assessment of soil moisture over vegetation  

NASA Technical Reports Server (NTRS)

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.

Carlson, T. N.

1986-01-01

48

Measurements and modeling of soil creep rates based on vegetation impedance on steep hillslopes  

NASA Astrophysics Data System (ADS)

Diffusive soil transport involves the movement of soil particles downslope due to small-scale processes such as bioturbation and rainsplash. Estimates of the diffusion-like coefficient (the "diffusivity'') associated with soil creep on soil-mantled hillslopes are conventionally obtained from fitting of measured hillslope profiles of known age to modeled profiles, calculations involving tracer motions, and calculations based on conservation of cosmogenic isotopes. Published values of diffusivities vary over several orders of magnitude and are associated with variations in soil properties, climate regime, and dominant processes contributing to soil particle motions. The rate of sediment transport depends on the diffusivity as well as the gradient of the hillslope. Even on steep slopes, small sediment transport rates on the human timescale make them difficult to measure, but diffusive transport nevertheless is involved in land-surface evolution at his timescale. On steep, forested hillslopes, trees influence the local flux of sediment. Specifically, a tree blocks delivery of sediment to its downslope side, so sediment moves away from the base of the tree faster than it is delivered from upslope. The resulting "excavation'' of sediment often leads to exposed roots. Similarly, sediment accumulates on the upslope side of the tree and is "steered'' around the tree. For trees of sufficient size (and age) a small but measurable mound often forms upslope of the tree. This mound introduces a possible method for estimating the diffusivity. The volume of sediment stored by each tree can only have been accumulating for as long as the tree has been alive, so dividing the volume of the mound by the age of the tree provides an estimate of the rate of transport. In order to illustrate and quantify this process, I have developed a numerical model that simulates the evolution of the hillslope surface concurrently with the growth of a tree. A two-dimensional, mass-conserving diffusion equation models land-surface evolution while a Chapman-Richards-like growth equation models the radial growth of the tree. In the model a mound forms upslope of the tree, and a divot forms downslope of the tree, consistent with detailed field surveys of mound and divot topography associated with large trees. Parameters such as the diffusivity, the slope of the land surface, and the total growth time can be calibrated to match model results. In general, the mound size increases with land-surface slope and tree size.

Jones, M. B.; Furbish, D. J.

2013-12-01

49

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

PubMed

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 ?M 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. PMID:25265594

Van?k, Aleš; Grösslová, Zuzana; Mihaljevi?, Martin; Ettler, Vojt?ch; Chrastný, Vladislav; Komárek, Michael; Tejnecký, Václav; Drábek, Ond?ej; Penížek, Vít; Galušková, Ivana; Van??ková, Barbora; Pavl?, Lenka; Ash, Christopher

2015-02-11

50

Vegetation Effects on Soil Moisture Estimation  

NASA Technical Reports Server (NTRS)

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

Kim, Yunjin; van Zyl, Jakob

2004-01-01

51

Green vegetation, nonphotosynthetic vegetation, and soils in AVIRIS data  

NASA Technical Reports Server (NTRS)

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.

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

1993-01-01

52

Treatment of soil, vegetation and snow in land surface models: a test of the BiosphereAtmosphere Transfer Scheme with the  

E-print Network

Treatment of soil, vegetation and snow in land surface models: a test of the Biosphere of the land surface, their individual hydrological processes and the process-oriented models are reviewed­Atmosphere Transfer Scheme (BATS) is examined regarding its performance for three different surfaces (crop, forest

Yang, Zong-Liang

53

Modelling the links between vegetation and landforms  

Microsoft Academic Search

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

Mike Kirkby

1995-01-01

54

Managing soil under vegetable production to improve soil quality  

Technology Transfer Automated Retrieval System (TEKTRAN)

Over the years, soil quality has eroded as soil organic matter has declined on farms across North Carolina. This study is assessing the effects of tillage practice, winter cover cropping and compost use on changes in soil function and improvement in soil quality under vegetable production. The field...

55

Retrieving pace in vegetation growth using precipitation and soil moisture  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

56

Application of the Distributed Soil Hydrology Vegetation Model (DHSVM) to the case of forest landcover change and alpine development  

NASA Astrophysics Data System (ADS)

Forest cover in the North East is changing due to both natural disturbances and anthropogenic influences. These changes in forest cover are likely to affect watershed hydrology, including precipitation interception, infiltration and stream flow. Understanding the interaction between forest cover and hydrologic processes is important as forests provide critical ecosystem services to the region. Our research focuses on alpine development in high-elevation, forested watersheds, in particular how the size, spatial arrangement, and orientation of ski runs and base village development influence runoff production. Our study area includes a forested control watershed and a watershed managed as an alpine ski area in northwestern Vermont. Empirical results from these watersheds show substantial differences (10-31%) in annual water yield between the watersheds over the 11-year period of record (2000-2011). This water yield differential is correlated with maximum seasonal snow depth (R2 = .47), with larger differences occurring in years with abundant winter snowpack. Field infiltration measurements show a significant difference between ski trail and forested soils (t=2.65, p<.05) with the average infiltration measured on ski trails nearly an order of magnitude slower. We suggest that enhanced routing of water from the compact soils found on ski trails and differences in watershed storage are responsible for the observed difference in runoff. Using the Distributed Soil Hydrology Vegetation Model (DHSVM), we developed model simulations for snow accumulation, melt and streamflow in both watersheds. Preliminary model runs show high model skill in simulating observed hourly flows (NE = .77). Model simulations support the hypothesis that slower infiltration results in an enhanced routing of runoff. This unique water transport mechanism should be integrated into future alpine development designs in order to moderate environmental impacts. Next steps will involve testing alternative alpine development scenarios and the effects of variable winter climate conditions on streamflow dynamics.

Del Peral, A.

2012-12-01

57

Reflectance of vegetation, soil, and water  

NASA Technical Reports Server (NTRS)

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.

Wiegand, C. L. (principal investigator)

1974-01-01

58

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

PubMed

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

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

2014-01-01

59

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

PubMed Central

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

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

2014-01-01

60

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

61

A Coupled Energy and Water Balance Model for Snow-Vegetation-Soil Systems  

Microsoft Academic Search

In mountainous and cold regions of the world snowmelt dominates the water balance, yet is quantified poorly despite the wealth of available remote sensing observations. Field measurements of snow cover and soil moisture are limited to experimental sites while the accuracy of soil moisture measurements from passive and active microwave sensors such as the upcoming SMOS and SMAP missions depends

D. Marks; M. Sandells; G. Flerchinger

2009-01-01

62

Vegetation management with fire modifies peatland soil thermal regime.  

PubMed

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 change for carbon processing and release, and hydrological processes, in these peatlands. PMID:25728915

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

2015-05-01

63

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)

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 explore the complex interactions involved in soil development and change. We were unable to identify appropriately-detailed existing models for plant productivity and for the dynamics of soil aggregation and porosity, and so developed the PROSUM and CAST models, respectively, to simulate these subsystems. Moreover, we applied the BRNS generator to obtain a chemical equilibrium model. These were combined with HYDRUS-1D (water and solute transport), a weathering model (derived from the SAFE model) and a simple bioturbation model. The model includes several feedbacks, such as the effect of soil organic matter on water retention and hydraulic conductivity. We encountered several important challenges when building the integrated model. First, a mechanism was developed that initiates the execution of a single time step for an individual sub-model and accounts for the relevant mass transfers between sub-models. This allows for different and sometimes variable time step duration in the submodels. Secondly, we removed duplicated processes and identified and included relevant solute production terms that had been neglected. The model is being tested against datasets obtained from several Soil Critical Zone Observatories in Europe. This contribution focuses on the design strategy for the model.

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

2014-05-01

64

Comparison of four models to determine surface soil moisture from C-band radar imagery in a sparsely vegetated semiarid landscape  

NASA Astrophysics Data System (ADS)

Four approaches for deriving estimates of near-surface soil moisture from radar imagery in a semiarid, sparsely vegetated rangeland were evaluated against in situ measurements of soil moisture. The approaches were based on empirical, physical, semiempirical, and image difference techniques. The empirical approach involved simple linear regression of radar backscatter on soil moisture, while the integral equation method (IEM) model was used in both the physical and semiempirical approaches. The image difference or delta index approach is a new technique presented here for the first time. In all cases, spatial averaging to the watershed scale improved agreement with observed soil moisture. In the empirical approach, variation in radar backscatter explained 85% of the variation in observed soil moisture at the watershed scale. For the physical and best semiempirical adjustment to the physical model, the root-mean-square errors (RMSE) between modeled and observed soil moisture were 0.13 and 0.04, respectively. Practical limitations to obtaining surface roughness measurements limit IEM utility for large areas. The purely image-based delta index has significant operational advantage in soil moisture estimates for broad areas. Additionally, satellite observations of backscatter used in the delta index indicated an approximate 1:1 relationship with soil moisture that explained 91% of the variability, with RMSE = 0.03. Results showed that the delta index is scaled to the range in observed soil moisture and may provide a purely image based model. It should be tested in other watersheds to determine if it implicitly accounts for surface roughness, topography, and vegetation. These are parameters that are difficult to measure over large areas, and may influence the delta index.

Thoma, D. P.; Moran, M. S.; Bryant, R.; Rahman, M.; Holifield-Collins, C. D.; Skirvin, S.; Sano, E. E.; Slocum, K.

2006-01-01

65

Soil Water Dynamics in a Clumped Vegetation Pattern  

NASA Astrophysics Data System (ADS)

Understanding the general principles behind the self-organization of vegetation may help to predict some of the consequences of environmental change for both ecosystem services and water resources. The accurate representation of landscape structure is necessary to estimate the flows exchanged between the earth's surface and atmosphere. Here, we adopted a physically based model to describe the spatial dynamics of vegetation taking into account soil physical characteristics and plant physiology. This approach is used at the landscape scale in order investigate the impact of spatial organization of vegetation on soil moisture distribution, evapotranspiration rate, root system uptake, vegetation stress, net primary productivity, etc. The proposed model is adopted in a patchy vegetation mosaic based on a spatial random process of individual tree canopies and their accompanying root systems. The spatial distribution of vegetation is not modeled like a homogeneous process of canopies, but like aggregated tree distribution, typically observed in savannas. To this end, we used a mathematical framework for describing vegetation structure based on the density, dispersion, and size distribution of individuals within a landscape. In particular, we posed particular attention to the role of clumping on the landscape dynamics analyzing different configurations of climatic parameters, soil types and plant types. The analyses show how the clumping structure may be beneficial for water use efficiency at the landscape scale.

Manfreda, S.; Pizzolla, T.; Caylor, K. K.

2013-12-01

66

Vegetation competition model for water and light limitation. II: Spatial dynamics of groundwater and vegetation  

Microsoft Academic Search

In temperate climates groundwater can have a profound effect on vegetation, because it strongly influences the spatio-temporal distribution of soil moisture in the rootzone and therefore the occurrence of water and oxygen stress of vegetation. This article focuses on vegetation and groundwater dynamics along a hill slope by developing and evaluating a fully coupled hydrological-vegetation model for a temperate forest

R. J. Brolsma; L. P. H. van Beek; M. F. P. Bierkens

2010-01-01

67

Development of a Scale-Consistent Soil-Vegetation-Atmosphere Modeling System Using COSMO, Community Land Model and ParFlow  

NASA Astrophysics Data System (ADS)

Here, we present the development and application of a modular scale-consistent coupled soil vegetation atmosphere (SVA) modeling system. The SVA modeling system developed at the Transregional Collaborative Research Centre 32 (TR32, 2nd phase), consists of the Deutscher Wetterdienst (DWD, German Weather Service) regional climate and weather forecast model COSMO (Consortium for Small Scale Modeling), the National Centre for Atmospheric Research (NCAR) Community Land Model (CLM) and the 3D variably saturated groundwater hydrology model ParFlow ( originally developed at the Lawrence Livermore National Laboratory). The external coupler Ocean Atmosphere Sea Ice Soil (OASIS) developed at European Centre for Research and Advanced Training (CERFACS, Toulouse, France) is used to drive the SVA system and control the exchange of fluxes defined over different grids of the components of the modeling system. Idealized and realistic test case simulations are presented to show the capability of this SVA modeling system to simulate the land-atmosphere interactions including ground water dynamics. The development of this SVA modeling system will also allow the integration of various model advancement efforts (e.g. implementation of carbon cycle, crop dynamics, downscaling and upscaling algorithm, development of adjoint models) and ensures the availability of these developments to the scientific community.

Shrestha, P.; Sulis, M.; Masbou, M.; Kollet, S. J.; Simmer, C.

2012-12-01

68

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

NASA Astrophysics Data System (ADS)

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

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

2010-09-01

69

The soil water balance in a mosaic of clumped vegetation  

NASA Astrophysics Data System (ADS)

The spatio-temporal distribution of soil moisture influences the plant growth and the distribution of terrestrial vegetation. This effect is more evident in arid and semiarid ecosystems where the interaction between individuals and the water limited conditions play a fundamental role, providing environmental conditions which drive a variety of non-linear ecohydrological response functions (such as transpiration, photosynthesis, leakage). In this context, modeling vegetation patterns at multiple spatial aggregation scales is important to understand how different vegetation structures can modify the soil water distribution and the exchanged fluxes between soil and atmosphere. In the present paper, the effect of different spatial vegetation patterns, under different climatic scenarios, is investigated in a patchy vegetation mosaic generated by a random process of individual tree canopies and their accompanying root system. Vegetation pattern are generated using the mathematical framework proposed by Caylor et al. (2006) characterized by a three dimensional stochastic vegetation structure, based on the density, dispersion, size distribution, and allometry of individuals within a landscape. A Poisson distribution is applied to generate different distribution of individuals paying particular attention on the role of clumping on water distribution dynamics. The soil water balance is evaluated using the analytical expression proposed by Laio et al. (2001) to explore the influence of climate and vegetation patterns on soil water balance steady-state components (such as the average rates of evaporation, the root water uptake and leakage) and on the stress-weighted plant water uptake. Results of numerical simulations show that clumping may be beneficial for water use efficiency at the landscape scale. References Caylor, Kelly K., P. D'Odorico and I. Rodriguez Iturbe: On the ecohydrology of structurally heterogeneous semiarid landscape. Water Resour. Res., 28, W07424, 2006. Laio, F., A. Porporato, L., Ridolfi and I. Rodriguez Iturbe: Plants in water controlled ecosystems: Active role in hydrological processes and response to water stress, II. Probabilistic soil moisture dynamics, Adv. Water Resour., 24(7), 707-723,2001.

Pizzolla, Teresa; Manfreda, Salvatore; Caylor, Kelly; Gioia, Andrea; Iacobellis, Vito

2014-05-01

70

An applied vegetation canopy model and its application in inversion of vegetation coverage and water content  

Microsoft Academic Search

Usually a vegetated area pixel is composed of the basic components, soil, leaf with different proportions, while soil and leaf have different water content. There are lots of canopy models to describe the mechanism with which these component spectra compose the canopy spectrum. For practicability, a simplified model is suggested to calculate the surface vegetation coverage, and water contents of

Ru-Ru Deng; Qin-Huo Liu; Guo-Liang Tian; Xiao-Zhou Xin; Qiang Liu; Hua Gong

2002-01-01

71

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

USGS Publications Warehouse

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).

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

2012-01-01

72

GRAZING AND MILITARY VEHICLE EFFECTS ON GRASSLAND SOILS AND VEGETATION  

E-print Network

:cattlegrazing,disturbance,grasslands,GreatPlainsecosystems,militaryimpacts,state-and-transition models IntroductIon Public land managers face pressure to maintain ecosystems, often in an idealizedGRAZING AND MILITARY VEHICLE EFFECTS ON GRASSLAND SOILS AND VEGETATION John A. Guretzky and Alan B natural state, while supporting multiple and sometimes conflicting land uses(NationalResearchCouncil1994

Fehmi, Jeffrey S.

73

Calculations of radar backscattering coefficient of vegetation-covered soils  

NASA Technical Reports Server (NTRS)

A model for simulating the measured backscattering coefficient of vegetation-covered soil surfaces includes both coherent and incoherent components of the backscattered radar pulses from a rough sil surface. The effect of vegetation canopy scattering is also incorporated into the model by making the radar pulse subject to two-way attenuation and volume scattering when it passes through the vegetation layer. Model results agree well with the measured angular distributions of the radar backscattering coefficient for HH polarization at the 1.6 GHz and 4.75 GHz frequencies over grass-covered fields. It was found that the coherent scattering component is very important at angles near nadir, while the vegetation volume scattering is dominant at incident angles 30 degrees.

Mo, T.; Schmugge, T. J.; Jackson, T. J. (principal investigators)

1983-01-01

74

Soil Respiration Responses to Variation in Temperature Treatment and Vegetation Type  

NASA Astrophysics Data System (ADS)

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

Liu, S.; Pavao-zuckerman, M.

2013-12-01

75

Reflectance of vegetation, soil, and water  

NASA Technical Reports Server (NTRS)

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.

Wiegand, C. L. (principal investigator)

1973-01-01

76

Reflectance of vegetation, soil, and water  

NASA Technical Reports Server (NTRS)

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.

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

1974-01-01

77

The impact of soil reflectance on the quantification of the green vegetation fraction from NDVI  

E-print Network

The impact of soil reflectance on the quantification of the green vegetation fraction from NDVI L to calculate Fg is to create a simple linear mixing model between two NDVI endmembers: bare soil NDVI (NDVIo) and full vegetation NDVI (NDVI). Usually it is assumed that NDVIo is close to zero (NDVIo 0

Small, Eric

78

Coevolution of hydraulic, soil and vegetation processes in estuarine wetlands  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

79

Modelling of vegetation volumes  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

80

Analysis of co-evolving soil depths, vegetation patterns, and connectivity on drylands.  

NASA Astrophysics Data System (ADS)

Arid and semiarid landscapes cover more than 30% of the Earth's surface. Vegetation in these areas is usually patchy due limited resource availability. This self-organized patchiness results from the nonlinear feedbacks between water redistribution, soils, landforms, and biota. These complex interactions make the understanding and prediction of landscape responses to climate and land use change highly challenging. Though several models have been recently developed and used to understand these feedbacks and the emergence of vegetation patterns in drylands, these models do not explicitly incorporate feedbacks with coevolving soil depths. Here we analyse feedback effects resulting from co-evolving soil depths, which play a key role in the redistribution of surface runoff and therefore on the patterns of vegetation and landscape connectivity. We present modelling results using a coupled landform evolution-dynamic vegetation model, which includes a soil depth evolution module accounts and for soil production and sediment erosion and deposition processes. We analyse the co-evolution of soil depths and vegetation patterns for varying soil erodibilities, slopes and plant functional types. We find that for deeper soils, facilitation effects of vegetation gives rise to the formation of regular patterns, and slope and soil erodibility are the key factors for recovery after disturbance. Disturbances in areas with high slope and/or soil erodibility lead to an increase in connectivity and a degraded state. In contrast, we find that for shallow soils, the facilitation effect of vegetation becomes less important and vegetation patterns are more irregular. In this case, soil depth becomes the key factor prescribing surface connectivity and for the recovery of the system after disturbance. These results have critical implications for effective management and restoration efforts, and for understanding the effects of changes in climate and land use.

Saco, Patricia; Willgoose, Garry

2014-05-01

81

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

USGS Publications Warehouse

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

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

2011-01-01

82

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

PubMed Central

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

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

2009-01-01

83

Vegetation and soil factors on the Jerah mine, Scotland  

Microsoft Academic Search

The vegetation of a small spoil heap at Jerah mine near Stirling was classified as species-rich acid grassland, an open barren-soil community with a high frequency of the moss Pohlia nutans, and a group which showed intermediate characteristics. Copper was present in the soil in potentially toxic concentrations and when the vegetation data were ordinated the axes showed highly significant

Angela Heaney; John Proctor

1983-01-01

84

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

NASA Technical Reports Server (NTRS)

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

Lee, S. L.

1974-01-01

85

Sensitivity of convective precipitation forecasts to soil moisture and vegetation  

NASA Astrophysics Data System (ADS)

Land surface properties play a major role in convective precipitation events through impacting the amount of surface evaporation which results in changes to near surface temperature and humidity. This study examines the effects of using soil moisture data from the North American Regional Reanalysis (NARR) and the Soil Moisture Ocean Salinity Satellite (SMOS) on short term weather forecasts using the Weather Research and Forecasting Model (WRF). SMOS soil moisture data were compared to in-situ observations and it was found that although they captured the spatial variation in soil moisture, the actual measurements had a dry bias of roughly 0.10 m3/m 3. Large differences existed between the in-situ observations, even for probes only a few meters apart. Observations from different sensors within a SMOS footprint differed from each other by a larger amount than they differed from the SMOS retrieval. Removing the mean and normalizing the data brought the in-situ observations into better agreement with each other and with SMOS but they still contained substantial differences. WRF sensitivity experiments demonstrated that changes to initial values of soil moisture resulted in no significant changes in precipitation. However, more of an impact was seen when the vegetation was changed, with barren vegetation yielding a substantial decrease in precipitation. Adding soil moisture resulted in significant changes to 2 m temperature and dewpoint relative to the control runs for each vegetation type. However, it was found that convective available potential energy and moist static energy change little, as the temperature and humidity impacts on these variables cancel each other out, which explain the limited precipitation response. SMOS data resulted in no significant changes in precipitation forecasts but had some impacts on temperature and humidity forecasts. However, because these results were not seen in all cases, no definitive conclusions about the usefulness of SMOS for high resolution numerical modeling can be made at this time. These results provide major implications for future satellite missions such as Soil Moisture Active Passive showing that experiments using true data assimilation methods which give only partial weight to satellite data may also not provide significant improvements to weather forecasts.

Collow, Thomas William

86

Transregional Collaborative Research Centre 32: Patterns in Soil-Vegetation  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

87

Derivation of soil moisture retrieval uncertainties associated to the simplification of the dynamic vegetation signal.  

NASA Astrophysics Data System (ADS)

Satellite-based microwave remote sensing has proven to provide reliable soil moisture observations on a global scale over the last decades. In microwave remote sensing of soil moisture the satellite signal holds information on both soil moisture and vegetation. Separating these components from each other is not straightforward. In the last years the importance of a robust and reliable vegetation parameterization within the soil moisture retrieval algorithms has become evident. In the TU-Wien soil moisture retrieval algorithm, developed by the Vienna University of Technology, the backscatter observations are corrected for vegetation effects by way of the slope and curvature. The slope and curvature are derivates of noisy backscatter measurements in relation to incidence angle and hence have a high level of noise. Therefore, they are averaged over several years resulting in a fixed seasonal vegetation correction, where no inter-annual variability is present in the characterisation of vegetation. This study assesses the strengths and weaknesses of the fixed seasonal vegetation correction in the TU-Wien soil moisture retrieval algorithm. The Vegetation Optical Depth (VOD) retrieved from AMSR-E passive microwave observations with the VUA-NASA retrieval algorithm is analysed to identify regions with high inter-annual variability in vegetation. For these regions the effect of a fixed seasonal correction on the soil moisture retrieval is investigated. First, the TU-Wien soil moisture products before and after the application of the vegetation correction, the TU-Wien normalised backscatter and TU-Wien soil moisture respectively, are compared to modelled soil moisture from ECMWFs ERA-Interim. With this analysis regions where the vegetation correction decreases the quality of the TU-Wien soil moisture product with regard to modeled soil moisture can be identified. Secondly, the vegetation correction within the TU-Wien retrieval algorithm is replaced by the VOD to simulate an inter-annually dynamic vegetation correction. The VOD is like the slope and curvature an indicator of vegetation water content. This new soil moisture product based on VOD is then also compared to modeled soil moisture from ERA-Interim. Results show that in areas of high inter-annual variability, like the Sahel, the TU-Wien vegetation correction is suboptimal and decreases the quality of the TU-Wien soil moisture product when compared to ERA-Interim. Spearman R with ERA-Interim soil moisture can decrease with as much as 0.4 after applying the vegetation correction. Using the VOD in these regions increases the quality of the TU-Wien soil moisture product. This study demonstrates that a fixed seasonal vegetation correction is not able to account for high inter-annual vegetation variability and leads to an inaccurate soil moisture signal, emphasizing the need for a dynamic vegetation correction.

Vreugdenhil, Mariette; Dorigo, Wouter; de Jeu, Richard; Hahn, Sebastian; Salinas, Jose Luis; Wagner, Wolfgang

2014-05-01

88

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

89

Associations between vegetation patterns and soil texture in the shortgrass steppe  

Microsoft Academic Search

A recent conceptual model of controls on vegetation structure in semiarid regions includes the hypothesis that the balance between the dominance of woody and herbaceous species is partly controlled by soil texture. The model predicts that the dominance of woody plants is associated with coarse textured soils, and that ecotones between woody and herbaceous plant functional types are associated with

M. B. Dodd; W. K. Lauenroth; I. C. Burke; P. L. Chapman

2002-01-01

90

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...

91

Mediterranean shrub vegetation: soil protection vs. water availability  

NASA Astrophysics Data System (ADS)

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 at least 45% and soil loss by at least 59% in relation to an abandoned and degraded soil (bare soil) (Garcia-Estringana et al., 2010a). D. pentaphyllum, M. strasseri and C. arborescens were more effective in reducing runoff and soil loss (at least 83% and 97% respectively) than R. sphaerocarpa (45% and 59% respectively). Pisctacia Lentiscus L reduced the soil losses in 87% and the runoff rates (68%) meanwhile Quercus coccifera L reached a larger reduction (95% and 88 %) in comparison to herbicide treated agriculture soil. So, all shrub species protected the soil, but not in the same way. In relation to rainfall reaching the soil surface, great differences were observed among species, with interception losses varying between 10% for R. sphaerocarpa to greater than 36% for D. pentaphyllum and M. strasseri, and with stemflow percentages changing between less than 11% for D. pentaphyllum and M. strasseri and 20% for R. sphaerocarpa (Garcia-Estringana et al., 2010b). Rainfall interception on Pistacia Lentiscus and Quercus coccifera were 24% and 34% respectively for the two years of measurements. The integration of the effects of Mediterranean shrub vegetation on soil protection and rainfall partitioning fluxes facilitates understanding the effects of changes in vegetation type on soil and water resources. From this perspective, the interesting protective effect of D. pentpahyllum and M. strasseri, reducing intensely runoff and soil loss contrasts with the dangerous reduction in rainfall reaching the soil surface. Soil protection is essential in semiarid and arid environments, but a proper assessment of the effects on water availability is critical because of water is a scant resource in these kinds of environments. Pistacia Lentiscus and Quercus coccifera shown both a high capacity to intercept rainfall, increase infiltration and reduce the soil losses. We suggest to apply similar research programs into recently fire affected land as the role of vegetation after the fire is very dynamic (Cerdà 1998b). Acknowledgements The research projects 07 M/0077/1998, 07 M/0023/

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

2014-05-01

92

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

NASA Technical Reports Server (NTRS)

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.

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

1997-01-01

93

Statistical modeling of global soil NOx emissions  

Microsoft Academic Search

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

Xiaoyuan Yan; Toshimasa Ohara; Hajime Akimoto

2005-01-01

94

Vegetation classification and soil moisture calculation using land surface temperature (LST) and vegetation index (VI)  

NASA Astrophysics Data System (ADS)

In this paper, the temperature-missivity separating (TES) method and normalized difference vegetation index (NDVI) are introduced, and the hyperspectral image data are analyzed using land surface temperature (LST) and NDVI channels which are acquired by Operative Module Imaging Spectral (OMIS) in Beijing Precision Agriculture Demonstration Base in Xiaotangshan town, Beijing in 26 Apr, 2001. Firstly, the 6 kinds of ground targets, which are winter wheat in booting stage and jointing stage, bare soil, water in ponds, sullage in dry ponds, aquatic grass, are well classified using LST and NDVI channels. Secondly, the triangle-like scatter-plot is built and analyzed using LST and NDVI channels, which is convenient to extract the information of vegetation growth and soil's moisture. Compared with the scatter-plot built by red and near-infrared bands, the spectral distance between different classes are larger, and the samples in the same class are more convergent. Finally, we design a logarithm VIT model to extract the surface soil water content (SWC) using LST and NDVI channel, which works well, and the coefficient of determination, R2, between the measured surface SWC and the estimated is 0.634. The mapping of surface SWC in the wheat area are calculated and illustrated, which is important for scientific irrigation and precise agriculture.

Liu, Liangyun; Zhang, Bing; Xu, Genxing; Zheng, Lanfen; Tong, Qingxi

2002-03-01

95

Carbon Dynamics in Vegetation and Soils  

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

96

Effects of vegetation structure on biomass accumulation in a Balanced Optimality Structure Vegetation Model (BOSVM v1.0)  

NASA Astrophysics Data System (ADS)

A myriad of interactions exist between vegetation and local climate for arid and semi-arid regions. Vegetation function, structure and individual behavior have large impacts on carbon-water-energy balances, which consequently influence local climate variability that, in turn, feeds back to the vegetation. In this study, a conceptual vegetation structure scheme is formulated and tested in the new Balanced Optimality Structure Vegetation Model (BOSVM) to explore the importance of vegetation structure and vegetation adaptation to water stress on equilibrium biomass states. Surface energy, water and carbon fluxes are simulated for a range of vegetation structures across a precipitation gradient in West Africa and optimal vegetation structures that maximize biomass for each precipitation regime are determined. Two different strategies of vegetation adaptation to water stress are included. Under dry conditions vegetation tries to maximize the water use efficiency and leaf area index as it tries to maximize carbon gain. However, a negative feedback mechanism in the vegetation-soil water system is found as the vegetation also tries to minimize its cover to optimize the surrounding bare ground area from which water can be extracted, thereby forming patches of vertical vegetation. Under larger precipitation, a positive feedback mechanism is found in which vegetation tries to maximize its cover as it then can reduce water loss from bare soil while having maximum carbon gain due to a large leaf area index. The competition between vegetation and bare soil determines a transition between a "survival" state to a "growing" state.

Yin, Z.; Dekker, S. C.; van den Hurk, B. J. J. M.; Dijkstra, H. A.

2014-05-01

97

Investigation of Soil Moisture - Vegetation Interactions in Oklahoma  

E-print Network

and-atmosphere interactions are an important component of climate, especially in semi-arid regions such as the Southern Great Plains. Interactions between soil moisture and vegetation modulate land-atmosphere coupling and thus represent a crucial...

Ford, Trenton W.

2013-03-06

98

Integrating dynamic soil and vegetation properties into ecosystem service-based state and transition models to guide rangeland management  

Technology Transfer Automated Retrieval System (TEKTRAN)

California’s annual rangelands cover approximately 6.4 million hectares, and produce 70% of the state’s forage base. This ecosystem supports more than 300 vertebrate, 5000 invertebrate, and 2000 plant species. Annual rangeland soils have the capacity to support high primary productivity, accumulate ...

99

Salix vegetation filters for purification of waters and soils  

Microsoft Academic Search

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

K. L. Perttu; P. J. Kowalik

1997-01-01

100

Remote measurement of soil moisture over vegetation using infrared temperature measurements  

NASA Technical Reports Server (NTRS)

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.

Carlson, Toby N.

1991-01-01

101

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

Microsoft Academic Search

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

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

2006-01-01

102

FUEL CHARACTERIZATION AND EFFECTS OF WILDFIRE RECURRENCE ON VEGETATION STRUCTURE ON LIMESTONE SOILS IN SOUTHEASTERN  

E-print Network

AND EFFECTS OF WILDFIRE RECURRENCE ON VEGETATION STRUCTURE ON LIMESTONE SOILS IN SOUTHEASTERN FRANCE) Fuel characterization and effects of wildfire recurrence on vegetation structure on limestone soils: wildfire recurrence; fire interval, wildland fuel, vegetation structure; shrubland, Pinus halepensis

Paris-Sud XI, Université de

103

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

NASA Technical Reports Server (NTRS)

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.

Bolten, John; Crow, Wade

2012-01-01

104

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

Microsoft Academic Search

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

Fawwaz Ulaby; Gerald Bradley; Myron Dobson

1979-01-01

105

Soil, water, and vegetation conditions in south Texas  

NASA Technical Reports Server (NTRS)

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

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

1977-01-01

106

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

107

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

NASA Astrophysics Data System (ADS)

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.

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

2011-07-01

108

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

PubMed Central

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

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

2014-01-01

109

Modeling Feedbacks Between Water and Vegetation in the Climate System  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

110

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

Microsoft Academic Search

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

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

2004-01-01

111

Passive microwave response to vegetation and soil moisture on agricultural fields  

NASA Astrophysics Data System (ADS)

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.

Miller, B.; Bullock, Paul R.

2014-10-01

112

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

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

113

Soil drainage and vegetation controls of nitrogen transformation rates in forest soils, southern Quebec  

E-print Network

Soil drainage and vegetation controls of nitrogen transformation rates in forest soils, southern and tree species on nitrogen (N) mineralization and nitrification rates in two forest catenas in southern. Potential N transformation rates in soils under American beech, sugar maple, and eastern hemlock trees were

Moore, Tim

114

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

NASA Astrophysics Data System (ADS)

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 interventions to ensure the long-term sustainability of the restored ecosystems.

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

2014-05-01

115

Assessment of regional biomass-soil relationships using vegetation indexes  

NASA Technical Reports Server (NTRS)

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.

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

1991-01-01

116

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

NASA Astrophysics Data System (ADS)

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

Bochet, Esther; García-Fayos, Patricio

2013-04-01

117

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

NASA Technical Reports Server (NTRS)

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

Wang, James R.

1996-01-01

118

Sigma Mesa: Background elemental concentrations in soil and vegetation, 1979  

SciTech Connect

In 1979, soil and vegetation samples were collected on Sigma Mesa to provide background data before construction on the mesa. Elemental data are presented for soil, grass, juniper, pinon pine, and oak. None of the data looks out of the ordinary. The purpose of the sampling program was to acquire, before any disturbance, a set of data to be used as background for future impact analysis. 6 refs., 2 figs., 7 tabs.

Ferenbaugh, R.W.; Gladney, E.S.; Brooks, G.H. Jr.

1990-10-01

119

Vegetation on the Soil Infiltration System Treating Livestock Wastewater  

NASA Astrophysics Data System (ADS)

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

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

120

Role of vegetation cover on soil water balance in two Mediterranean areas: semiarid and dry at southeastern of Spain.  

NASA Astrophysics Data System (ADS)

Water is a limited resource in the semiarid areas, which affects both, the population services, the economic growth, like the natural ecosystems stability. In this context, an accurate knowledge of soil water balance and role of the vegetation cover contribute to improve the management of resources water and forest. These studies are increasingly important, if we consider the latest Assessment Reports of the Intergovernmental Panel on Climate Change. In this paper the main objectives were focused on:(1)To determine the soil water balance on two different climatic conditions, semiarid and dry climate and(2) Assess the effect of vegetation (structure and cover) on soil water balance under the studied climatic conditions. For this purpose we used HYDROBAL ecohydrological model, which calculates at a daily resolution the water flows through of the vegetation canopy, estimates daily soil moisture and predicts deep drainage from the unsaturated soil layer into the aquifer. In order to achieve these objectives, we have selected two sites in the south-eastern of Spain, on soils calcareous and different climatic conditions. Ventós site in a semiarid Mediterranean area and Confrides site in a dry Mediterranean area, with 303 and 611 mm of annual precipitation respectively. Both sites, the predominant vegetation are afforestations with Pinus halepensis on dry grasslands with some patches of thorn shrublands and dwarf scrubs; but it show difference on trees density, cover and height of pines.Soil water balance was determined in each site using HYDROBAL ecohydrological model on one hydrological year (October 2012 and September 2013).Model inputs include climatic variables (daily rainfall and temperature), as well as soil and vegetation characteristics (soil field capacity, soil wilting point, initial soil water content and vegetation cover index). Model outputs are interception, net rainfall, runoff, soil water reserves, actual evapotranspiration, direct percolation, and deep percolation (or aquifer recharge). In the last decade, HYDROBAL model has been used successfully in semiarid conditions, to assess the soil water balance on different vegetation cover types, and the effect of different land-use scenarios on water resources and aquifer recharge. Results highlight the role of vegetation cover type and volume of annual rainfall on the soil water balance. Both sites present similar percentage of vegetation cover(>80%), however in Ventós site (semiarid area), a lower pine cover (44%) and lower volume of annual rainfall produced differences in the soil water balance. In Confrides site (dry area), in spite of show the twice of annual rainfall, a higher pine cover (78%) reduced the net precipitation and consequently affected the soil water balance. An understanding the role of vegetation cover on soil water balance is a very useful tool to implement an optimal management of forest and water resources.

Manrique, Àngela; Ruiz, Samantha; Chirino, Esteban; Bellot, Juan

2014-05-01

121

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

NASA Astrophysics Data System (ADS)

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 flow and erosion are affected by this change in vegetation pattern, along with the covarying soil properties.

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

2006-12-01

122

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

123

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

PubMed

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. PMID:21284189

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

2010-11-01

124

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

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

125

Reflectance of vegetation, soil, and water  

NASA Technical Reports Server (NTRS)

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.

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

126

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

Microsoft Academic Search

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

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

2004-01-01

127

Evaluation of the Hydro-Thermodynamic Soil Vegetation Scheme and implementation of a new numerical scheme  

E-print Network

ii Evaluation of the Hydro-Thermodynamic Soil Vegetation Scheme and implementation of a new.S. Fairbanks, Alaska August 2005 #12;iii Abstract The Hydro-Thermodynamic Soil-Vegetation Scheme (HTSVS;iv Table of Contents Abstract

Moelders, Nicole

128

Modeling the interaction between plant canopies and the planetary boundary layer using a new 1D multi-layer soil- vegetation-atmosphere transfer (SVAT) scheme combined with a non-local turbulence closure model  

NASA Astrophysics Data System (ADS)

A new one-dimensional (1D) soil-vegetation-atmospheric transport (SVAT) scheme is coupled to a nonlocal turbulence closure model in order to simulate the interactions between a forested canopy and the planetary boundary layer. The SVAT consists of mechanistic models for both physiological (photosynthesis, stomatal conductance and soil/root and bole respiration) and micrometeorological (radiative transfer and surface energy exchanges) processes. The turbulence closure model is a first-order, nonlocal turbulence closure called transilient turbulence theory (Stull, 1993; Inclan et al., 1995) which includes the effects of form drag, wake turbulence, and interference to vertical mixing by the plant elements. The submodel that accounts for radiative transfer inside the forest has been taken from Norman (1979) and Baldocchi (1989). It includes the effect of varying mean leaf inclination angle with height and it also accounts for leaf clumping The photosynthesis submodel is taken from Nikolov and others (1995). It accounts for both differences between shaded and sunlit leaves and the variation of photosynthetic capacity with height. The model was tested with data obtained from a deciduous forest in Pennsylvania. The results show reasonable agreement with the observations. They also demonstrate the model's ability to simulate phenomena that is characteristic of tall canopies like forests, including counter gradient-fluxes and local wind speed maxima in the trunk space.

Yetzer, Kenneth H.

129

Reflectance of vegetation, soil, and water  

NASA Technical Reports Server (NTRS)

There are no author-identified significant results in this report. This report deals with the selection of the best channels from the 24-channel aircraft data to represent crop and soil conditions. A three-step procedure has been developed that involves using univariate statistics and an F-ratio test to indicate the best 14 channels. From the 14, the 10 best channels are selected by a multivariate stochastic process. The third step involves the pattern recognition procedures developed in the data analysis plan. Indications are that the procedures in use are satsifactory and will extract the desired information from the data.

Wiegand, C. L. (principal investigator)

1973-01-01

130

Mercury concentrations in oligohaline wetland vegetation and associated soil biogeochemistry.  

PubMed

Concentrations of mercury were determined in above- and below-ground tissues of dominant plant species, as well as soils, in the wetlands of Lake Maurepas, Louisiana. Indicators of wetland soil biogeochemical status, such as soil redox potential, pore-water nutrient concentrations, and pore-water total sulfides, were also determined. Total mercury concentrations in plant tissues were within the typical range for vegetation not exposed to mercury contamination. Similarly, total mercury concentrations in soils were typical of uncontaminated wetlands within this geographic region. Soil methyl mercury levels in this study are slightly lower than those reported in other studies of nearby wetlands. This may reflect the less extensive geographic sampling in this study, or the low water levels in the Lake Maurepas system immediately prior to and during this study, which would have altered soil biogeochemical status. This is corroborated by measurements of soil redox potential and soil pore-water nitrogen and sulfur constituents conducted during this study that suggest minimal sulfate reduction was occurring in surficial soils. This study indicates that the wetlands surrounding Lake Maurepas are typical of many uncontaminated oligohaline wetlands in the southeastern U.S. in regard to mercury concentrations. PMID:21188507

Willis, Jonathan M; Gambrell, Robert P; Hester, Mark W

2011-10-01

131

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 ...

132

Soil Moisture and Vegetation Water Content Retrieval Using QuikSCAT data  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

133

Modelling the Congo basin ecosystems with a dynamic vegetation model  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

134

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

Technology Transfer Automated Retrieval System (TEKTRAN)

Soil moisture can be estimated over large regions with spatial resolutions greater than 500 m, but many applications require finer resolutions (10 – 100 m grid cells). Several methods use topographic data to downscale, but vegetation and soil patterns can also be important. In this paper, a downsc...

135

A Mixture Modeling Approach to Estimate Vegetation Parameters for Heterogeneous Canopies in Remote Sensing  

Microsoft Academic Search

In this article, we describe a reflectance model which parametrizes the reflectance of vegetation canopies from optical properties of leaves and soil, and dominant canopy structural parameters. The model assumes certain principles of geometric models, for example, that sensor integrates the radiance reflected from three components, plant, shaded soil, and illuminated soil. Its inversion provides compositional information of the ground

M. A. Gilabert; F. J. Garc??a-Haro; J. Meliá

2000-01-01

136

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

NASA Astrophysics Data System (ADS)

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

Hassler, Sibylle; Weiler, Markus; Blume, Theresa

2014-05-01

137

Canopy reflectance modelling of semiarid vegetation  

NASA Technical Reports Server (NTRS)

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

Franklin, Janet

1994-01-01

138

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

NASA Technical Reports Server (NTRS)

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

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

1977-01-01

139

Reflectance of vegetation, soil, and water  

NASA Technical Reports Server (NTRS)

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.

Wiegand, C. L. (principal investigator)

1973-01-01

140

Fungal communities in soils along a vegetative ecotone.  

PubMed

We investigated the community composition and diversity of soil fungi along a sharp vegetative ecotone between coastal sage scrub (CSS) and nonnative annual grassland habitat at two sites in coastal California. USA- We pooled soil samples across 29 m transects on either side of the ecotone at each of the two sites, and. using clone libraries of fungal ribosomal DNA, we identified 280 operational taxonomic units (OTUs) from a total 40 g soil. We combined information from partial LSU and ITS sequences and found that the majority of OTUs belonged to the phylum Ascomycota, followed by Basidiomycota. Within the Ascomycota. a quarter of OTUs were Sordariomycetes. 17% were Leotiomycet.es, 16% were Dothideomycetes and the remaining OTUs were distributed among the classes Eurotiomycetes, Pezizomycetes, Lecanoromycetes, Orbiliomycetes and Arthoniomycetes. Within the Basidiomycota. all OTUs but one belonged to the subphylum Agaricomycotina. We also sampled plant communities at the same sites to offer a point of comparison for patterns in richness of fungal communities. Fungal communities had higher alpha and beta diversity than plant communities; fungal communities were approximately 20 times as rich as plant communities and the majority of OTUs were found in single soil samples. Soils harbored a unique mycoflora that did not reveal vegetative boundaries or site differences. High alpha and beta diversity and possible sampling artifacts necessitate extensive sampling to reveal differentiation in these fungal communities. PMID:22802393

Karst, Justine; Piculell, Bridget; Brigham, Christy; Booth, Michael; Hoeksema, Jason D

2013-01-01

141

Soil and Vegetation Management: Keys to Water Conservation on Rangeland  

E-print Network

as cover declines below these levels. Plant cover also interrupts the travel of rain- drop splash and overland flow thus reducing erosion. Soil movement caused by surface flow depends on the energy of the runoff, the susceptibility of the soil to detachment... in Edwards County, Texas. Adapted from Blackburn, et al. 1986. n storm characteristics. Vegetative surfaces can hold only a certain amount of water at a given time. Large storms account for the major portion of runoff and deep drainage in the Southwest...

Schuster, Joseph L.

2001-01-11

142

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

143

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

PubMed

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. PMID:23624425

Bargiel, D; Herrmann, S; Jadczyszyn, J

2013-07-30

144

Assessment of regional biomass-soil relationships using vegetation indexes  

SciTech Connect

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.

Lozano-Garcia, D.F.; Fernandez, R.N.; Johannsen, C.J. (Lab. of Applications of Remote Sensing, Purdue Univ., West Lafayette, IN (US))

1991-03-01

145

Prairie vegetation and soil nutrient responses to ungulate carcasses  

Microsoft Academic Search

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

E. Gene Towne

2000-01-01

146

Vegetation development on deposit soils starting at different seasons  

Microsoft Academic Search

Permanent plots were created in different seasons (autumn and spring) and filled with two substrates: nutrient-rich topsoil\\u000a and nutrient-poor ruderal soil (n = 5 for each treatment). My objectives were to assess the influence of starting season on initial species composition, whether\\u000a differences at the start cause divergent or convergent pathways of succession and which mechanisms are operating during vegetation\\u000a development. Mean

Franz Rebele

2008-01-01

147

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

NASA Astrophysics Data System (ADS)

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 indicate that most changes of vegetation types may be related to abrupt changes in soil properties. These changes do not only occur along the slope as a result of malachite deposition by erosion but the surface processes seem to be predominant in the context of the hills.

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

2013-04-01

148

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

PubMed

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

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

2014-01-01

149

Environmental sensor networks for vegetation, animal and soil sciences  

NASA Astrophysics Data System (ADS)

Environmental sensor networks (ESNs) provide new opportunities for improving our understanding of the environment. In contrast to remote sensing technologies where measurements are made from large distances (e.g. satellite imagery, aerial photography, airborne radiometric surveys), ESNs focus on measurements that are made in close proximity to the target environmental phenomenon. Sensors can be used to collect a much larger number of measurements, which are quantitative and repeatable. They can also be deployed in locations that may otherwise be difficult to visit regularly. Sensors that are commonly used in the environmental sciences include ground-based multispectral vegetation sensors, soil moisture sensors, GPS tracking and bioacoustics for tracking movement in wild and domesticated animals. Sensors may also be coupled with wireless networks to more effectively capture, synthesise and transmit data to decision-makers. The climate and weather monitoring domains provide useful examples of how ESNs can provide real-time monitoring of environmental change (e.g. temperature, rainfall, sea-surface temperature) to many users. The objective of this review is to examine state-of-the-art use of ESNs for three environmental monitoring domains: (a) terrestrial vegetation, (b) animal movement and diversity, and (c) soil. Climate and aquatic monitoring sensor applications are so extensive that they are beyond the scope of this review. In each of the three application domains (vegetation, animals and soils) we review the technologies, the attributes that they sense and briefly examine the technical limitations. We conclude with a discussion of future directions.

Zerger, A.; Viscarra Rossel, R. A.; Swain, D. L.; Wark, T.; Handcock, R. N.; Doerr, V. A. J.; Bishop-Hurley, G. J.; Doerr, E. D.; Gibbons, P. G.; Lobsey, C.

2010-10-01

150

River basin soil-vegetation condition assessment applying mathematic simulation methods  

NASA Astrophysics Data System (ADS)

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

Mishchenko, Natalia; Trifonova, Tatiana; Shirkin, Leonid

2013-04-01

151

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

NASA Astrophysics Data System (ADS)

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 beneficial for water resource management, forestry, and agriculture.

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

2015-01-01

152

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

PubMed

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

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

2009-11-01

153

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

154

Modelling the Effects of Vegetation on Stability of Slopes  

Microsoft Academic Search

Summary: It is well understood that vegetation influences slope stability in two ways: through hydrological effects and mechanical effects. Hydrological effects involve the removal of soil water by evapotranspiration through vegetation, which lead to an increase in soil suction or a reduction in pore-water pressure, hence, an increase in the soil shear strength. The shear strength of the soil is

Y H Chok; M. I. E. Aust; M B Jaksa; D V Griffiths

155

Development of the IAP Dynamic Global Vegetation Model  

NASA Astrophysics Data System (ADS)

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

Zeng, Xiaodong; Li, Fang; Song, Xiang

2014-05-01

156

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

PubMed

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

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

157

Soil TPH Concentration Estimation Using Vegetation Indices in an Oil Polluted Area of Eastern China  

PubMed Central

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 (R2?=?0.73) and accuracy of prediction (RMSE?=?104.2 mg kg?1). For other vegetation indices and red edge parameters, the R2 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 (R2?=?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

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

158

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

Microsoft Academic Search

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

Zongqiang GONG; Peijun LI; B. M. Wilke; Kassem Alef

2008-01-01

159

A microwave scattering model for layered vegetation  

NASA Technical Reports Server (NTRS)

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.

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

1992-01-01

160

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

PubMed Central

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

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

2014-01-01

161

Modeling vegetation controls on fluvial morphological trajectories  

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

162

Influence of vegetation, soil and antecedent soil moisture on the variability of surface runoff coefficients at the plot scale in the eastern alps  

Microsoft Academic Search

Modelling the runoff of a catchment in a high spatial resolution, you need to know the potential of a single plot to generate surface runoff. The portion of surface runoff is highly significant for storm runoff events, accordingly, it mainly forms the hydrograph. In this study, the influence of vegetation, soil features and antecedent soil moisture on generating surface runoff

P. Chifflard; B. Kohl; G. Markart; R. Kirnbauer

2009-01-01

163

Soil-vegetation-climate interactions in arid landscapes: Effects of the North American monsoon on grass recruitment  

Technology Transfer Automated Retrieval System (TEKTRAN)

We used a daily time step, multi-layer simulation model of soil water dynamics to integrate effects of soils, vegetation, and climate on the recruitment of Bouteloua eriopoda (black grama), the historically dominant grass in the Chihuahuan Desert. We simulated landscapes at the Jornada ARS-LTER site...

164

Soil-vegetation-climate interactions in arid landscapes: Effects of the North American monsoon on grass recruitment  

E-print Network

in carbon dynamics (Jackson et al., 2002; Knapp et al., 2008) and loss of biodiversity and forage productionSoil-vegetation-climate interactions in arid landscapes: Effects of the North American monsoon Perennial grass Plant-soil feedbacks Simulation model State change a b s t r a c t We used a daily time step

165

Effects of varying soil moisture contents and vegetation canopies on microwave emissions  

NASA Technical Reports Server (NTRS)

Results of NASA airborne passive microwave scans of bare and vegetated fields for comparison with ground truth tests are discussed and a model for atmospheric scattering of radiation by vegetation is detailed. On-board radiometers obtained data at 21, 2.8, and 1.67 cm during three passes over each of 46 fields, 28 of which were bare and the others having wheat or alfalfa. Ground-based sampling included moisture in five layers down to 15 cm in addition to soil temperature. The relationships among the brightness temperature and soil moisture, as well as the surface roughness and the vegetation canopy were examined. A model was developed for the dielectric coefficient and volume scattering for a vegetation medium. L- to C-band data were found useful for retrieving soil information directly. A surface moisture content of 5-35% yielded an emissivity of 0.9-0.7. The data agreed well with a combined multilayer radiative transfer model with simple roughness correction.

Burke, H.-H. K.; Schmugge, T. J.

1982-01-01

166

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

167

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

Microsoft Academic Search

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

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

2010-01-01

168

Radar response to vegetation. [soil moisture mapping via microwave backscattering  

NASA Technical Reports Server (NTRS)

Active microwave measurements of vegetation backscatter were conducted to determine the utility of radar in mapping soil moisture through vegetation and mapping crop types. Using a truck-mounted boom, spectral response data were obtained for four crop types (corn, milo, soybeans, and alfalfa) over the 4-8 GHz frequency band, at incidence angles of 0 to 70 degrees in 10-degree steps, and for all four linear polarization combinations. Based on a total of 125 data sets covering a wide range of soil moisture, content, system design criteria are proposed for each of the aforementioned objectives. Quantitative soil moisture determination was best achieved at the lower frequency end of the 4-8 GHz band using HH polarized waves in the 5- to 15-degree incidence angle range. A combination of low and high frequency measurements are suggested for classifying crop types. For crop discrimination, a dual-frequency dual-polarization (VV and cross) system operating at incidence angles above 40 degrees is suggested.

Ulaby, F. T.

1975-01-01

169

Modified vegetation-erosion dynamics model and its application in typical watersheds in the Loess Plateau  

Microsoft Academic Search

The vegetation-erosion model was applied in three typical watersheds of hilly and gully area in the Loess Plateau in northwestern China to study the dynamic relations between vegetation coverage and soil erosion rate and various stresses. The model was improved by introducing rainfall and runoff factors. Then the modified model was applied in the Luergou and Luoyugou watersheds. The calculation

Yuehong CHEN; Feixin WANG; Guangquan LIU; Xinxiao YU; Guodong JIA; Ping GAN

2011-01-01

170

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

NASA Technical Reports Server (NTRS)

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

Eagleson, Peter S.; Jasinski, Michael F.

1988-01-01

171

The soil seed bank and its relationship to the established vegetation in urban wastelands  

Microsoft Academic Search

Industrial and traffic areas are particularly characteristic of the urban environment. Due to frequent soil transport and vegetation disturbance, soil seed banks and seed production play an essential role for vegetation establishment in these sites. Since researchers have scarcely focussed on these traits, it was analysed in three railway and loading areas in Munich. Seed numbers in soil ranged from

Harald Albrecht; Elisabeth Eder; Thomas Langbehn; Clara Tschiersch

2011-01-01

172

Relationship between vegetation diversity and soil functional diversity in native mixed-oak forests  

Microsoft Academic Search

Most studies on the interactions between aboveground vegetation and belowground soil diversity have been carried out in microcosms or manipulated field plots. In the current study, we investigated the relationship between forest vegetation diversity and soil functional diversity (calculated from the activity of soil enzymes) in naturally developed plant communities of native mixed-oak forests without imposing any disturbances to already

Gloria Rodríguez-Loinaz; Miren Onaindia; Ibone Amezaga; Iker Mijangos; Carlos Garbisu

2008-01-01

173

Linking variability in soil solution dissolved organic carbon to climate, soil type, and vegetation type  

NASA Astrophysics Data System (ADS)

Lateral transport of carbon plays an important role in linking the carbon cycles of terrestrial and aquatic ecosystems. There is, however, a lack of information on the factors controlling one of the main C sources of this lateral flux, i.e., the concentration of dissolved organic carbon (DOC) in soil solution across large spatial scales and under different soil, vegetation, and climate conditions. We compiled a database on DOC in soil solution down to 80 cm and analyzed it with the aim, first, to quantify the differences in DOC concentrations among terrestrial ecosystems, climate zones, soil, and vegetation types at global scale and second, to identify potential determinants of the site-to-site variability of DOC concentration in soil solution across European broadleaved and coniferous forests. We found that DOC concentrations were 75% lower in mineral than in organic soil, and temperate sites showed higher DOC concentrations than boreal and tropical sites. The majority of the variation (R2 = 0.67-0.99) in DOC concentrations in mineral European forest soils correlates with NH4+, C/N, Al, and Fe as the most important predictors. Overall, our results show that the magnitude (23% lower in broadleaved than in coniferous forests) and the controlling factors of DOC in soil solution differ between forest types, with site productivity being more important in broadleaved forests and water balance in coniferous stands.

Camino-Serrano, Marta; Gielen, Bert; Luyssaert, Sebastiaan; Ciais, Philippe; Vicca, Sara; Guenet, Bertrand; Vos, Bruno De; Cools, Nathalie; Ahrens, Bernhard; Altaf Arain, M.; Borken, Werner; Clarke, Nicholas; Clarkson, Beverley; Cummins, Thomas; Don, Axel; Pannatier, Elisabeth Graf; Laudon, Hjalmar; Moore, Tim; Nieminen, Tiina M.; Nilsson, Mats B.; Peichl, Matthias; Schwendenmann, Luitgard; Siemens, Jan; Janssens, Ivan

2014-05-01

174

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

175

The effects of soil moisture, surface roughness, and vegetation on L-band emission and backscatter  

NASA Technical Reports Server (NTRS)

Measurements performed with SIR-B at 1.28 GHz and an airborne multiple-beam push-broom radiometer at 1.4 GHz over agricultural fields near Fresno, California are examined. A theoretical model (Kirchhoff approximation) was used to assess the effects of surface roughness and vegetation (alfalfa and lettuce) with respect to the responses of microwave emission and backscatter to soil-moisture variations. It is found that the surface roughness plays a dominant role compared to the vegetation cover in the microwave backscatter.

Wang, James R.; Shiue, J. C.; Engman, Edwin T.; Schmugge, Thomas J.; Mo, Tsan

1987-01-01

176

Soil water and vegetation management for cleanup of selenium contaminated soils  

SciTech Connect

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

Not Available

1989-05-01

177

The Impact of Climate on Sulfur Isotopes in Soils and Vegetation  

NASA Astrophysics Data System (ADS)

Stable isotopes of sulfur (S) in soil can be used as tracers for sources and in-situ processes, and understanding what drives the variability of S isotope ratios in the coupled precipitation-soil-vegetation system can provide a basis for identifying regions with potential S limitations or high susceptibility to anthropogenic additions. Here we investigated the impact of climate on the isotopic composition of total S in soils and vegetation (reported as ?34S values) using a series of well-defined climosequences at several locations around the globe. This is the most comprehensive study to date of the geographical patterns of soil and plant S, with sites covering a mean annual precipitation (MAP) range of 1 to 4200 mm and a mean annual temperature (MAT) range of 2.5 to 25.5°C. Within this broad range of climates the following relationships were explored: (1) constant MAP, varying MAT; (2) constant MAT, varying MAP; (3) increasing MAP as MAT decreases; (4) decreasing MAP as MAT decreases. The impact of other soil forming factors (parent material, landscape age and topography) were also considered and distinguished from the effects of climate. Based on total S and S isotope analysis of archived and newly-collected soil, vegetation, and rainwater samples from a total of 13 sites with nearly 70 sub-sites around the world, we produced a model for predicting the behavior of soil and plant S isotopes with climate. Our results showed that location affected soil ?34S by affecting the chemistry of S inputs to soil (i.e. proximity to the ocean, industrial centers, volcanoes, or other major sources of S). In areas with similar S sources, however, ?34S of soil and vegetation was controlled by MAP, with MAT playing a secondary role. At the wet end of the rainfall spectrum (2000-4200 mm), surface soil ?34S was around 15-17‰, approaching the seawater sulfate value of 21‰. This reflects the proximity to the ocean and the high proportion of ocean-derived rain at those sites. In the moderate MAP range (50-1000 mm), ?34S values of the upper 10 cm of the soil generally increased from 2.5 to 6.9‰ with increasing MAP while plant ?34S values decreased from 7.5 to 1.8‰. At the dry end of the rainfall spectrum (MAP < 50 mm), surface soil ?34S increased again, approaching 7‰. S isotope fractionation during plant uptake was also MAP-dependent: at sites with MAP > 600 mm, the ?34S of surface soil was greater than that of plants, while the opposite behavior was observed at MAP <600 mm. Total soil S (which is mostly organic S) ?34S values generally increased with soil depth, with the most pronounced increase at the wettest sites (MAP 3500-4200 mm). This increase likely reflects microbial mineralization of soil organic S. In contrast, at the hyperarid sites (MAP <5 mm), where microbial reactions are severely limited, soil ?34S decreased with depth. Overall, our results show that soil and plant ?34S vary predictably with climate, when accounting for variations due to input chemistry and other soil forming factors.

Balan, S. A.; Amundson, R.

2012-12-01

178

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

USGS Publications Warehouse

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

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

179

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

NASA Astrophysics Data System (ADS)

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%.

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

1980-10-01

180

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

PubMed

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. PMID:21071065

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

2010-12-15

181

Hydrologic modeling of soil water storage in landfill cover systems  

SciTech Connect

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.

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

1987-01-01

182

A dynamic global vegetation model for studies of the coupled atmosphere-biosphere system  

Microsoft Academic Search

This work presents a new dynamic global vegetation model designed as an extension of an existing surface-vegetation-atmosphere transfer scheme which is included in a coupled ocean-atmosphere general circulation model. The new dynamic global vegetation model simulates the principal processes of the continental biosphere influencing the global carbon cycle (photosynthesis, autotrophic and heterotrophic respiration of plants and in soils, fire, etc.)

G. Krinner; Nicolas Viovy; Nathalie de Noblet-Ducoudré; Jérôme Ogée; Jan Polcher; Pierre Friedlingstein; Philippe Ciais; Stephen Sitch; I. Colin Prentice

2005-01-01

183

Productivity of wet soils: Biomass of cultivated and natural vegetation  

SciTech Connect

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

Johnston, C.A.

1988-12-01

184

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

NASA Astrophysics Data System (ADS)

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

Moreno, Jose; Moran, Susan

2014-05-01

185

Vegetation modeled as a water cloud  

Microsoft Academic Search

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

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

1978-01-01

186

Interactions between vegetation, hydrology, and soil biogeochemistry in a Southern California annual grassland  

NASA Astrophysics Data System (ADS)

The soil carbon-nitrogen cycle is an integral component of the surface hydrologic system. Vegetation dynamics influence and respond to soil water and nitrogen availability, which are also linked through biogeochemical (e.g. decomposition, mineralization) and physical processes (e.g. drainage, transpiration). With anticipated changes in precipitation variability and reactive nitrogen inputs, a holistic approach toward understanding this coupled system is necessary. Leveraging data from a factorial irrigation-fertilization experiment in a Mediterranean-like annual grassland, we search for evidence of feedbacks between vegetation, nitrogen availability, and hydrology. Our analysis demonstrates that the water balance is relatively insensitive to an exogenous increase in nitrogen availability, due to a trade-off between canopy density and leaf conductance. This is consistent with the notion that, in semi-arid ecosystems, canopy structure and physiology work in an integrated fashion to maintain a transpiration flux tightly controlled by soil and climate properties. We explain this behavior with a model constrained by the hydraulic capacity of the soil-vegetation-atmosphere pathway.

Parolari, A.; Goulden, M.; Bras, R. L.

2011-12-01

187

SRTM vegetation removal and hydrodynamic modeling accuracy  

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

188

Vegetation and soils field research data base: Experiment summaries  

NASA Technical Reports Server (NTRS)

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.

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

1984-01-01

189

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

NASA Astrophysics Data System (ADS)

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 down from saturation to complete water stress were performed and is analyzed as far how ABL respond to soil moisture changes. This provides informations about ABL behavior on the transition states. Future studies will look on how this behavior will change with the new vegetation covers.

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

2013-05-01

190

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

NASA Technical Reports Server (NTRS)

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.

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

2001-01-01

191

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

Microsoft Academic Search

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

Jiangbao Xia; Zhaohua Lu; Chuanrong Li; Peng Gao

2011-01-01

192

Soil amendments reduce trace element solubility in a contaminated soil and allow regrowth of natural vegetation.  

PubMed

We tested the effects of three amendments (a biosolid compost, a sugar beet lime, and a combination of leonardite plus sugar beet lime) on trace element stabilisation and spontaneous revegetation of a trace element contaminated soil. Soil properties were analysed before and after amendment application. Spontaneous vegetation growing on the experimental plot was studied by three surveys in terms of number of taxa colonising, percentage vegetation cover and plant biomass. Macronutrients and trace element concentrations of the five most frequent species were analysed. The results showed a positive effect of the amendments both on soil chemical properties and vegetation. All amendments increased soil pH and TOC content and reduced CaCl(2)-soluble-trace element concentrations. Colonisation by wild plants was enhanced in all amended treatments. The nutritional status of the five species studied was improved in some cases, while a general reduction in trace element concentrations of the aboveground parts was observed in all treated plots. The results obtained show that natural assisted remediation has potential for success on a field scale reducing trace element entry in the food chain. PMID:16005126

Madejón, Engracia; de Mora, Alfredo Pérez; Felipe, Efraín; Burgos, Pilar; Cabrera, Francisco

2006-01-01

193

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

NASA Technical Reports Server (NTRS)

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

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

1997-01-01

194

Mechanisms influencing surface soil CO2 efflux in respect to elevation and vegetation gradients in a complex watershed  

NASA Astrophysics Data System (ADS)

Topographically complex watersheds exert spatial and temporal variations in the distribution of soil water due to horizontal flows. The redistribution of soil water has profound effects on biogeochemical cycles. Of keen interest is the impact this lateral redistribution has on carbon cycling and surface soil carbon efflux. We are currently employing a plot based study across an elevation gradient (950-1150 m) in the Weimer Run watershed located near Davis, West Virginia to evaluate carbon and water cycling dynamics. At each of three different elevation levels (high, middle, low) are three sites. At each site are three 4 m2 plots, each underneath a different vegetation cover type (open, closed tree canopy, shrub canopy), for a total of 27 plots across all elevations. At each plot, surface CO2 efflux, soil temperature, PAR, air temperature and volumetric soil water content at 0-12 cm are measured weekly during the growing season. Measurements of Leaf Area Index (LAI) and soil nutrient concentrations (NH4+, NO3-) have also been conducted for each plot. Each plot also has gas wells at both 5 and 20 cm to measure CO2 concentrations below the soil surface. Data collected from June through October, 2010, indicate a stronger control on soil CO2 efflux exerted by vegetation cover type than by elevation gradient. The impact of vegetation cover type on soil CO2 efflux increases with elevation. Based on data collected weekly from June through October, 2010, there is no significant relationship between surface soil CO2 efflux and the three elevation levels within our gradient (p = 0.47). However, a significant statistical relationship between surface soil CO2 efflux and vegetation type (p = < 0.001) exists, regardless of seasonality. Soil moisture shows an expected decline with increasing elevation. Soil temperatures across vegetation types are nearly identical. Nutrient availability appears to be strongly correlated with vegetation type, but uncorrelated with elevation level. The heterogeneity of a watershed can greatly influence biogeochemical cycles. Quantifying the impact that vegetation cover, elevation and micrometeorological controls exert on soil CO2 efflux is vital for accurate model inputs and carbon budgets.
* All values in columns represent means for respective treatments for June - October 2010. +/- indicate standard deviation.

Atkins, J. W.; Epstein, H. E.; Welsch, D. L.

2011-12-01

195

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

PubMed

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. PMID:21774319

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

2011-04-01

196

Stability of banded vegetation patterns under seasonal rainfall and limited soil moisture storage capacity  

Microsoft Academic Search

The delicate equilibrium of soil moisture and biomass may become unstable under water scarcity conditions causing banded vegetation patterns to form on hillsides of semi-arid catchments. Soil related processes that induce instability (namely: soil moisture advection and diffusion), have been evaluated numerically for different rainfall regimes. This study addresses the combined influence of some relevant soil characteristics, and the effect

Nadia Ursino; Samuel Contarini

2006-01-01

197

Soil Carbon and Nitrogen Dynamics During Conversion of Agricultural Lands to Natural Vegetation in Central Korea  

Microsoft Academic Search

Changes in land use can affect the distribution and cycling of soil organic matter and nutrients. Soil organic carbon (C) and nitrogen (N) concentrations, soil CO2 evolution, litter decomposition, and soil N availability under the three types of conversion of agricultural lands to natural vegetation (rice field conversion to forest, crop field conversion to shrub, and indigenous forest) in central

Yowhan Son; Soo Young Yang; Young Chul Jun; Rae Hyun Kim; Yoon Young Lee; Jung Ok Hwang; Jong Sung Kim

2003-01-01

198

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

SciTech Connect

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

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

1996-12-31

199

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

200

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)

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.

Chang, Jy-Tai; Wetzel, Peter J.

1991-01-01

201

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

PubMed

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

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

202

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

NASA Technical Reports Server (NTRS)

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.

Eagleson, Peter S.; Jasinski, Michael F.

1988-01-01

203

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

NASA Technical Reports Server (NTRS)

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.

Eagleson, P. S.

1985-01-01

204

Soils and vegetation of the lateral moraine at Malte Brun, Mount Cook Region, New Zealand  

Microsoft Academic Search

Soils and vegetation at an altitude of 1710 m on a lateral moraine above the Tasman glacier at Malte Brun, Southern Alps of New Zealand arc described.Surface morphology includes rectilinear and lobatc solifluction terraces, which are vegetated and stabilised, and colluvial debris in the form of fans.Two soil profiles are described, one from the solifluction terraces, the other from a

A. C. Archer; M. J. A. Simpson; B. H. Macmillan

1973-01-01

205

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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 mod...

206

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

NASA Technical Reports Server (NTRS)

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

Wiegand, C. L. (principal investigator)

1973-01-01

207

Soil, water, and vegetation conditions in south Texas  

NASA Technical Reports Server (NTRS)

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

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

1976-01-01

208

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

PubMed

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. PMID:23644280

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

2013-08-01

209

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

NASA Technical Reports Server (NTRS)

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.

Carlson, Toby N.

1988-01-01

210

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

NASA Astrophysics Data System (ADS)

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.

Ni, J.; Herzschuh, U.

2009-04-01

211

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

SciTech Connect

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

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

2004-11-01

212

Transmission Line Theory Based Two Layer Model for Determining Soil Moisture  

NASA Astrophysics Data System (ADS)

Present paper deals with the task of estimating soil moisture under vegetation cover by using transmission line theory based two layer model. The two layer model measures the impedance of both the layers namely, soil and vegetation. This impedance is the function of dielectric constant and thickness of both the layers. For known dielectric constant and height of vegetation layer, dielectric constant of soil was determined for certain thickness of soil layer using genetic algorithm (GA). The soil moisture value was retrieved from dielectric constant of soil by using Topp et al., (1980) relationship. Retrieved soil moisture values were in good agreement with observed values.

Mishra, P.; Singh, D.

2013-05-01

213

Magnesium retention on the soil exchange complex controlling Mg isotope variations in soils, soil solutions and vegetation in volcanic soils, Iceland  

NASA Astrophysics Data System (ADS)

Understanding the biogeochemical cycle of magnesium (Mg) is not only crucial for terrestrial ecology, as this element is a key nutrient for plants, but also for quantifying chemical weathering fluxes of Mg and associated atmospheric CO2 consumption, requiring distinction of biotic from abiotic contributions to Mg fluxes exported to the hydrosphere. Here, Mg isotope compositions are reported for parent basalt, bulk soils, clay fractions, exchangeable Mg, seasonal soil solutions, and vegetation for five types of volcanic soils in Iceland in order to improve the understanding of sources and processes controlling Mg supply to vegetation and export to the hydrosphere. Bulk soils (?26Mg = -0.40 ± 0.11‰) are isotopically similar to the parent basalt (?26Mg = -0.31‰), whereas clay fractions (?26Mg = -0.62 ± 0.12‰), exchangeable Mg (?26Mg = -0.75 ± 0.14‰), and soil solutions (?26Mg = -0.89 ± 0.16‰) are all isotopically lighter than the basalt. These compositions can be explained by a combination of mixing and isotope fractionation processes on the soil exchange complex. Successive adsorption-desorption of heavy Mg isotopes leads to the preferential loss of heavy Mg from the soil profile, leaving soils with light Mg isotope compositions relative to the parent basalt. Additionally, external contributions from sea spray and organic matter decomposition result in a mixture of Mg sources on the soil exchange complex. Vegetation preferentially takes up heavy Mg from the soil exchange complex (?26Mgplant-exch = +0.50 ± 0.09‰), and changes in ?26Mg in vegetation reflect changes in bioavailable Mg sources in soils. This study highlights the major role of Mg retention on the soil exchange complex amongst the factors controlling Mg isotope variations in soils and soil solutions, and demonstrates that Mg isotopes provide a valuable tool for monitoring biotic and abiotic contributions of Mg that is bioavailable for plants and is exported to the hydrosphere.

Opfergelt, S.; Burton, K. W.; Georg, R. B.; West, A. J.; Guicharnaud, R. A.; Sigfusson, B.; Siebert, C.; Gislason, S. R.; Halliday, A. N.

2014-01-01

214

Modelling of backscatter from vegetation layers  

NASA Technical Reports Server (NTRS)

A simple way to build up a library of models which may be used to distinguish between the different types of vegetation and ground surfaces by means of their backscatter properties is presented. The curve of constant power received by the antenna (Gamma sphere) is calculated for the given Stokes Scattering Operator, and model parameters are adopted of the most similar library model Gamma sphere. Results calculated for a single scattering model resembling coniferous trees are compared with the Gamma spheres of a model resembling tropical region trees. The polarization which would minimize the effect of either the ground surface or the vegetation layer can be calculated and used to analyze the backscatter from the ground surface/vegetation layer combination, and enhance the power received from the desired part of the combination.

Van Zyl, J. J.; Engheta, N.; Papas, C. H.; Elachi, C.; Zebker, H.

1985-01-01

215

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

NASA Technical Reports Server (NTRS)

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 sphere of the same volume. The first implementation of the radiobrightness module will therefore be a simple radiative transfer model without scattering.

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

2006-01-01

216

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

SciTech Connect

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

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

1992-10-01

217

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

SciTech Connect

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

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

1992-10-01

218

Evaluation of Landsat Multispectral Scanner data for mapping vegetated soil landscapes  

USGS Publications Warehouse

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.

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

1981-01-01

219

Evapotranspiration of soil water movement in small area vegetation  

NASA Astrophysics Data System (ADS)

In Greece, crops are frequently cultivated in small isolated areas in close proximity to roads and bare soils and therefore evapotranspiration is affected by local advection. Under these circumstances, oasis effect conditions are present and evapotranspiration is higher than what is expected. In this paper, the evapotranspiration and soil water dynamics of a cotton crop cultivated in small areas under the oasis effect is studied. To this end, two isolated free-drainage lysimeters cultivated with cotton in the year 2007 were used. Soil moisture of the soil profile of both the lysimeters was monitored with two capacitance water content probes. The soil water balance method was used to estimate crop evapotranspiration and corresponding crop coefficients in one of the two lysimeters. These coefficients were 75% larger than the FAO-56 crop coefficients at the mid-season stage. The FAO-56 and the derived crop coefficients were used for the simulation of the water dynamics in the second lysimeter by the SWBACROS model. The derived crop coefficients for these conditions produced much better results than the FAO-56 crop coefficients. The results were improved when crop coefficient value equal to 2.5 was used for the mid-season stage.

Paraskevas, C.; Georgiou, P.; Ilias, A.; Panoras, A.; Babajimopoulos, C.

2013-12-01

220

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

Microsoft Academic Search

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

Krista K. Bartz; Robert J. Naiman

2005-01-01

221

Soil and vegetation carbon stocks in Brazilian Western Amazonia: relationships and ecological implications for natural landscapes  

Microsoft Academic Search

The relationships between soils attributes, soil carbon stocks and vegetation carbon stocks are poorly know in Amazonia, even\\u000a at regional scale. In this paper, we used the large and reliable soil database from Western Amazonia obtained from the RADAMBRASIL\\u000a project and recent estimates of vegetation biomass to investigate some environmental relationships, quantifying C stocks of\\u000a intact ecosystem in Western Amazonia.

C. E. G. R. Schaefer; B. A. F. de Mendonça; H. Oliveira; J. L. Lani; L. M. Costa; E. I. Fernandes Filho

2008-01-01

222

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

NASA Technical Reports Server (NTRS)

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.

Wiegand, C. L. (principal investigator)

1974-01-01

223

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

NASA Astrophysics Data System (ADS)

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.

Goswami, B.; Kalita, M.

2014-11-01

224

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

E-print Network

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

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

2007-01-01

225

A regional dynamic vegetation-climate model for Central America  

NASA Astrophysics Data System (ADS)

Global vegetation models simulate the distribution of vegetation as a function of climate. Dynamic global vegetation models (DGVMs) are also able to simulate the vegetation shifts in response to climate change, which makes them particularly useful for addressing questions about past and future climate scenarios. However, DGVMs have been criticized for using generic plant functional types (PFTs) and running the models at a coarse grid cell resolution. Regional dynamic vegetation models are able to simulate important landscape variation, since they use a finer resolution and specific PFTs for their region. Regional studies have typically focused on boreal or temperate ecosystems in North America and Europe. We will be presenting the results of applying a dynamic regional vegetation-climate model (LPJ-GUESS) for Central America. Initially, the model was run with the described global PFTs. However, several biomes were very poorly represented. Two PFTs were added: a Tropical Needleleaf Evergreen Tree to improve the simulation of the Mixed Pine-Oak biome, and a Desert Shrub to capture the Xeric Shrublands. The overall distribution of biomes was visually similar, however the Kappa statistic indicated a poor agreement with the potential biome map (overall Kappa = 0.301). The Kappa statistic did improve as we aggregated cell sizes and simplified the biomes (overall Kappa = 0.728). Compared to remote sensing data, the model showed a strong correlation with total LAI (r = 0.75). The poor Kappa statistic is likely due to a combination of factors. The way in which biomes are defined by the author can have a large influence on the level of agreement between simulated and potential vegetation. The Kappa statistic is also limited to comparing individual grid cells and thus, cannot detect overall patterns. Examining those areas which are poorly represented will help to identify future work and improve the representation of vegetation in these ecological models. In particular, the model was especially poor at distinguishing between the different ‘dry’ biomes, such as Tropical Dry Forest, Savanna, Grassland and Xeric Shrubland. There are several potential reasons why this might be so. The module which simulates fire in LPJ-GUESS is based on fire requirement for boreal and temperate regions. Fire was underestimated in those areas which were supposed to be Savannas, which is likely why those areas were dominated by a Dry Tropical Forest. Other potential factors include hydraulic redistribution, facilitation, photosynthetic pathway, and the described soil layer.

Snell, R. S.; Cowling, S. A.; Smith, B.

2009-12-01

226

Evaluating models of climate and forest vegetation  

NASA Technical Reports Server (NTRS)

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.

Clark, James S.

1992-01-01

227

Modeling Hydrologic and Vegetation Responses in Freshwater Wetlands  

NASA Astrophysics Data System (ADS)

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-site, indicating the potential of the model in capturing soil moisture dynamics. Further application of the model for impact assessments demonstrates that drainage of wetlands resulting in groundwater drawdown is expected to produce appreciable effects on vegetation biomass response. The model developed in this study simulates the coupled and spatially-varying groundwater movement and plant growth dynamics, which allows researchers to better understand and protect the integrated hydrologic and vegetation systems of wetlands worldwide.

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

2010-05-01

228

Lead, cadmium, and zinc contamination of Aspen garden soils and vegetation  

Microsoft Academic Search

Samples of old silver mine dump materials, garden soils contaminated with mine dump materials, noncontaminated garden soils, and vegetation grown in these gardens were collected to determine the extent of Pb, Cd, and Zn contamination in Aspen, CO. Many of the mine dump materials and soils contained sufficient quantities of Pb and Cd to pose potential health risks if the

D. Y. Boon; P. N. Soltanpour

2009-01-01

229

Re-Vegetating Mine Land that Has Been Ameliorated with Alternative Soil Ameliorants  

Microsoft Academic Search

One of the major limiting factors for re-vegetating soils disturbed by surface coal mining in South Africa is their potentially acidic and nutrient deficient nature. Liming and fertilizing these soils are accepted as common practice, but recently it has become crucial to investigate the use of other soil ameliorants that can possibly provide a more sustainable system. The use of

Wayne F. Truter; Norman F. G. Rethman

230

Soil-vegetation correlations in the Connecticut River floodplain of Western Massachusetts  

USGS Publications Warehouse

As part of a national study analyzing the relation between hydric soils and wetland vegetation, the vegetation associated with a series of known soils was sampled along the Connecticut River floodplain in Massachusetts. Weighted average and index average (presence/absence) values were calculated for vegetation using wetland ecological index values from the National List of Plant Species that Occur in Wetlands developed by the U.S. Fish and Wildlife Service and procedures developed by T. R. Wentworth and G. P. Johnson at North Carolina State University. Good correspondence between soils and vegetation was recorded with two exceptions. Two typically nonhydric soils were determined to be hydric based on vegetation analyses. Examination of the groundwater hydrology of these two soils confirmed their hydric nature. The authors suggested that one of these soils may need to be redefined and they also suggested that the assigned index values for a few species of vegetation should be reexamined. However, in general the index average values of vegetation based on published wetland index values corresponded with the hydric and nonhydric nature of soils.

Veneman, Peter L.M.; Tiner, Ralph W.

1990-01-01

231

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

PubMed Central

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 of species which are typically observed as a consequence of strong environmental filtering, as for instance on sites affected by industrial activities. PMID:25474688

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

2014-01-01

232

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

PubMed

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

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

2014-01-01

233

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

USGS Publications Warehouse

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.

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

2008-01-01

234

Soil drainage and vegetation controls of nitrogen transformation rates in forest soils, southern Quebec  

NASA Astrophysics Data System (ADS)

We investigated the influence of soil drainage class and tree species on nitrogen (N) mineralization and nitrification rates in two forest catenas in southern Quebec. Monthly net N mineralization and nitrification rates were determined along transects running from well-drained to poorly drained soils for 2 years through in situ incubation of homogenized soils. Potential N transformation rates in soils under American beech, sugar maple, and eastern hemlock trees were determined through incubation of homogenized soils in the laboratory under two different moisture regimes (50 and 100% water by volume) mimicking well-drained and poorly drained soil conditions in the two watersheds. Field-based N mineralization rates averaged 38 ± 6 mg m-2 d-1 in well-drained soils, while those in the poorly drained soils averaged 17 ± 5 mg N m-2 d-1. Similarly, net nitrification rates in well-drained soils (18 ± 4 mg N m-2 d-1) were 3 times greater than those in poorly drained soils (6 ± 3 mg N m-2 d-1). Laboratory-based potential N mineralization rates in soils ranked sugar maple > American beech > eastern hemlock under both well-drained (incubated at 50% water by volume) and poorly drained soil conditions (incubated at 100% water by volume). Potential nitrification rates ranked sugar maple > American beech > eastern hemlock under well-drained soil conditions, while under poorly drained conditions, American beech > sugar maple ? eastern hemlock. Nitrification enzyme activity determined through a soil slurry method correlated significantly with field-based nitrification rates. Differences in soil volumetric water contents, leaf litter N input, and soil C:N ratios, as surrogates of soil drainage and floristic heterogeneity, respectively, correlated significantly with field-based N mineralization and nitrification rates. Field-based N mineralization and nitrification rates were higher in summer than in early spring and autumn. Soil drainage class and tree species exert marked controls over N transformation rates in forested landscapes and need to be incorporated when characterizing and/or modeling internal N cycling at watershed scales.

Ullah, Sami; Moore, Tim R.

2009-03-01

235

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

236

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

SciTech Connect

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

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

2005-02-01

237

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

PubMed

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. PMID:20963797

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

238

The N transformation mechanisms for rapid nitrate accumulation in soils under intensive vegetable cultivation  

Microsoft Academic Search

Purpose  Rapid soil degradation occurring under intensive vegetable cultivation, an increasingly common agricultural strategy in China,\\u000a is characterized by soil acidification, salinity, and NO3? accumulation. However, to date, the reasons for rapid NO3? accumulation in soils at the nitrogen (N) levels have not been completely understood. In this study, we explored the underlying\\u000a mechanisms for rapid NO3? accumulation in soils used

Tongbin Zhu; Jinbo Zhang; Zucong Cai; Christoph Müller

239

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

USGS Publications Warehouse

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.

Germino, Matthew J.

2013-01-01

240

Bioremediation of petroleum contaminated soil using vegetation. A microbial study  

SciTech Connect

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.

Lee, E.; Banks, M.K. (Kansas State Univ., Manhattan, KS (United States))

1993-12-01

241

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

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

242

Relations between Root-zone Soil Moisture and MODIS-derived Vegetation Indices in Oak savanna and Open Grassland in California  

NASA Astrophysics Data System (ADS)

Optical remote sensing cannot provide direct quantification of soil moisture, but here we test the idea that plant available soil moisture can be inferred through calibration of images that quantify plant-leaf water and photosynthetic relationships. We measured relationships between volumetric soil water content in the rooting zone of annual grasslands and oak savanna and six vegetation indices (VIs) derived from MODIS data (NDVI, EVI, ARVI, SAVI,VARI and NDWI). The measured sites were part of the AmeriFlux network in California: Tonzi Ranch (oak savanna)and Vaira Ranch(open grassland). To reduce the empirical effect of linking vegetation indices to soil moisture directly, measured gross primary production (GPP) was used to bridge them. The results showed that (1) VARI was most sensitive to soil moisture variations; (2) in open grassland GPP is significantly controlled by the available water in the soil but the relationship is not linear----- GPP continues to increase in the growing season as long as soil moisture is sufficient. In oak savanna, the relationship is less obvious because oak trees can exploit water in deep soil layers. The results also demonstrated a strong linear relationship between GPP and vegetation indices for both oak savanna and open grassland. Therefore, based on the relation between GPP and root-zone soil moisture and the relation between GPP and VI, we estimated soil moisture as a function of a VI. Likely, the functional parameters are dependent on vegetation types, soil texture and topography. In order to explore the sensitivity of this relationship in areas where soil moisture and vegetation production data are not available, we will use DayCENTURY and ISOLSM models to simulate soil moisture and primary production at instrumented sites with meteorological data and soil properties data. The simulation tested in Tonzi Ranch and Vaira Ranch suggest that we can estimate root-zone soil moisture with optical remotely sensed data at large scale.

Liu, S.; Chadwick, O.; Roberts, D.

2008-12-01

243

The Changing Model of Soil  

NASA Astrophysics Data System (ADS)

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

Richter, D. D.; Yaalon, D.

2012-12-01

244

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

E-print Network

Soil moisture and vegetation controls on evapotranspiration in a heterogeneous Mediterranean 2006. [1] Micrometeorological measurements of evapotranspiration (ET) can be difficult to interpret on evapotranspiration in a heterogeneous Mediterranean ecosystem on Sardinia, Italy, Water Resour. Res., 42, W08419, doi

Katul, Gabriel

245

Coupling a distributed hydrological model with a vegetated slope stability model  

NASA Astrophysics Data System (ADS)

Vegetation significantly influences the hydrological and mechanical properties which are relevant for the stability of shallow soils along sloping surfaces. In view of the complexity of soil plant hydrological interactions, the quantification of root mechanical reinforcement remains a challenge. In this paper we couple root reinforcement models with a quasi-dynamic wetness index (QDI), which is specifically designed for estimating the local wetness conditions by accounting for the character of the upslope topography and the time of the lateral soil moisture distribution. The overall modelling strategy can be effectively employed for assessing the relative hazard of shallow landslides accounting for vegetation patterns and dominant forest management practices. The methodology is applied to an area located in Northern Tuscany to assess the effect of root degradation after tree logging on the spatial occurrence of shallow landslides during extreme rainfall events.

Preti, F.; Dani, A.; Chirico, G. B.

2012-04-01

246

Bioremediation of petroleum contaminated soil using vegetation: A microbial study  

Microsoft Academic Search

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

Euisang Lee; M. K. Banks

1993-01-01

247

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

E-print Network

of Dielectric Constant of Soil Measurements with Wiebe Waveguide System Measurements with Giarola's Modified Waveguide Method V. RESULTS AND ANALYSIS Introduction Experimental Results and Analysis Effects of Surface Roughness Effects of Vegetation... Soil Moisture Contents" of the Vegetated Rough Surface. . . . The Tools of the Special Technique for Handling Clay for Dielectric Constant Measurements 194 202 ~Fi ure B-2a B-2b B-3a B-3b Step 1. . Step 2. Step 3. Step 4. ~pa e 203 203...

Lee, Siu Lim

1974-01-01

248

Vegetation and soil characteristics of the wasteland of Valika Chemical Industries near Manghopir, Karachi  

Microsoft Academic Search

The vegetation of the wasteland of Valika chemical industries near Manghopir road, Karachi was studied. Nine plant communities were recognized based on dominant species. In these plant communities the vegetation was disturbed, mostly halophytic and dominated bySuaeda fruticosa,Tamarix indica,Salsola baryosma,Cressa cretica,Atriplex griffithii,Haloxylon recurvum,Indigofera hochstetteri,Prosopis julifloraandChenopodium album.The physico-chemical properties of the soils were also analysed. Soil texture was mostly sandy loam,

Tariq Mehmood; Zafar M. Iqbal

1995-01-01

249

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

NASA Astrophysics Data System (ADS)

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

Katata, Genki; Held, Andreas; Mauder, Matthias

2014-05-01

250

Estimating Fractional Cover of Photosynthetic Vegetation, Non-Photosynthetic Vegetation and Soil in Savannas Using the EO-1 Hyperion and MODIS Sensors  

NASA Astrophysics Data System (ADS)

Monitoring the fractional cover of photosynthetic vegetation (PV), non-photosynthetic vegetation (NPV) and bare soil (BS) in savannas is important for carbon and water modeling, grazing management, fire risk assessment and erosion control. We developed a simple method for resolving their fractional cover with hyperspectral imagery, by combining the Normalized Difference Vegetation Index (NDVI) which measures vegetation greenness and the Cellulose Absorption Index (CAI), which quantifies the intensity of the cellulose-lignin feature at 2.0-2.2 ?m, and then applying a linear unmixing. We applied this method to three EO-1 Hyperion scenes acquired during the 2005 growing season in a site in northern Australia. Data from field measurements and from fire scar maps provided a means for qualitatively validating the results obtained. We then explored the potential of the MODIS-TERRA sensor for resolving vegetation fractional cover. We generated synthetic MODIS data from the Hyperion images and also used actual MODIS reflectance from the MOD09 product, concurrent with the Hyperion images. We found that the MODIS-TERRA sensor, despite not being able to quantify the cellulose feature directly, can be used for mapping fractional cover. This is due to the fact that vegetation, regardless of its photosynthetic status, has a lower reflectance at 2.1 ?m (MODIS band 7) than at 1.6 ?m (MODIS band 6), compared to soils, which have a relatively flat spectra at those wavelengths. We propose using the ratio of band 7 to band 6 together with the NDVI for resolving the proportions of PV, NPV and BS. We tested the method in 10 independent savanna sites across Australia where grass curing is continuously monitored and found very good agreement both in space and in time between observed and modeled fractional cover. Finally, we developed a prototype of an operational product based on the MOD43 product (Nadir BRDF-Adjusted Reflectance 16-Day composites) and discuss its strengths and limitations.

Guerschman, J. P.; Hill, M. J.; Barrett, D. J.; Renzullo, L.; Marks, A.; Botha, E.

2007-12-01

251

Phosphorus in China's Intensive Vegetable Production Systems: Overfertilization, Soil Enrichment, and Environmental Implications.  

PubMed

China's vegetable production has experienced a rapid growth in recent years. Total production amounted to 522.7 million Mg (1 Mg = 10 g) in 2009, which was more than nine times that in 1980 and represented >50% of the world production. Meanwhile, excessive use of animal manures and chemical fertilizers in vegetable fields has brought various production and environmental challenges, including excessive accumulation of nutrients in soils and accelerated water pollution problems. In this study, we have evaluated the current status of phosphorus (P) in China's intensive vegetable production systems based on data summarized from nearly 100 publications plus results from our recent experiments. Gross overfertilization occurred in greenhouse (571 kg P ha) and open-field (117 kg P ha) vegetable systems compared with P removal in harvested crops (44 and 25 kg P ha) per season. Excess P input led to soil enrichment of labile P, measured as Olsen-P, averaging 179 (greenhouses) and 100 mg P kg (open fields) in the 0- to 20-cm soil depth, and in some cases led to P leaching, as evidenced by increases in Olsen-P and CaCl-P at the 40- to 60-cm soil depth. The vast majority of vegetable soils had Olsen-P exceeding the critical level (46.0-58.0 mg P kg) for optimum vegetable yield. Innovative policies and strategies are urgently needed to implement science-based nutrient management practices to attain sustainable vegetable production while protecting natural and environmental resources. PMID:24216350

Yan, Zhengjuan; Liu, Pengpeng; Li, Yuhong; Ma, Lin; Alva, Ashok; Dou, Zhengxia; Chen, Qing; Zhang, Fusuo

2013-07-01

252

[Soil physical and chemical characteristics under different vegetation restoration patterns in China south subtropical area].  

PubMed

This paper studied the change of soil physical and chemical properties under eleven vegetation restoration patterns (1 kind of secondary forest, 2 kinds of pure coniferous plantations, 5 kinds of evergreen broad-leaved plantations, 2 kinds of conifer and broad-leaved mixed plantations, and 1 kind of shrub) typical in Daqingshan of Guangxi. Obvious differences were observed in the soil physical and chemical properties under different vegetation restoration patterns. The soil physical properties were better in secondary forest but poorer in pure conifer plantations. Conifer and broad-leaved mixed plantations had lower soil bulk density, and their soil total porosity and water-holding capacity were higher than those in pure plantations. There were no significant differences in the soil porosity among the 5 evergreen broad-leaved plantations. Except that of soil total K, the contents of soil nutrients in secondary forest were higher than those in plantations, and the soil C/N ratio and pH value were relatively lower. Comparing with shrub, the 9 plantations had an obvious change in their soil nutrient contents, e. g. , the increase of soil total N and available K. The 2 pure coniferous plantations had lower soil nutrient contents, but after mixed planted with evergreen broad-leaved trees, their soil nutrient contents increased markedly, and the soil C/N ratio decreased. PMID:21328932

Kang, Bing; Liu, Shi-rong; Cai, Dao-xiong; Lu, Li-hua; He, Ri-ming; Gao, Yan-xia; Di, Wei-zhi

2010-10-01

253

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

E-print Network

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

Mattox, April Marie

2013-07-30

254

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

E-print Network

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

Standiford, Richard B.

255

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

Microsoft Academic Search

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

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

2007-01-01

256

Feedback between structured vegetation and soil water in a changing climate: A simulation study  

Microsoft Academic Search

Structure and composition of vegetation influence the local water budget by transpiration and interception. On the other hand\\u000a soil water content crucially affects plant physiological processes such as nutrient transport or photosynthesis. These processes\\u000a in turn partly determine biomass production, plant growth, survival and competition and, thus, vegetation structure. This\\u000a vegetation-hydrology feedback has the potential to influence the impacts of

Heike Lischke; Bärbel Zierl

257

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

NASA Astrophysics Data System (ADS)

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.

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

2015-03-01

258

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

PubMed Central

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

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

2015-01-01

259

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

SciTech Connect

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.

Klooster, S.A.; Potter, C.S. [NASA/Ames Research Center, Moffett Field, CA (United States)

1995-06-01

260

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

NASA Astrophysics Data System (ADS)

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 encroached catchment were generally lower than on the grassland catchment, especially proceeding the seasons of peak rainfall in spring and fall. Frequency and magnitude of streamflow events was observed to be substantially reduced in the encroached catchment. Model simulation suggests that conversion of all existing grassland to juniper in the Cimarron River basin will increase overall water efflux through evapotranspiration sufficient to substantially reduce water yield for streamflow. Rapid transformation of mesic grasslands to a woodland state with juniper encroachment, if not confined, has the potential to reduce soil water, streamflow and flow duration of ephemeral streams. Slowing the expansion of woody encroachment into grasslands might be considered as a land-based strategy to sustain or even augment streamflow and groundwater recharge to meet the increase in water demand under increasing climate variability and population growth in the southern Great Plains of USA

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

2014-05-01

261

Utilizing satellite imagery and GLOBE student data to model soil dynamics  

Microsoft Academic Search

General Purpose Atmosphere Plant Soil Simulator (GAPS), a menu-driven soil-vegetation-atmosphere transfer (SVAT) model, was used to simulate soil water dynamics from 1998 through 2001 for Greenville, PA, USA. GLOBE student data collected by students from Reynolds Junior and Senior High School, coupled with normalized difference vegetation index (NDVI) data derived from SPOT4 vegetation imagery, were used to parameterize and validate

Jessica Robin; Elissa Levine; Susan Riha

2005-01-01

262

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

NASA Technical Reports Server (NTRS)

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

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

1981-01-01

263

Floristic Composition of Vegetation and the Soil Seed Bank in Different Types of Dunes of Kerqin Steppe  

Microsoft Academic Search

The floristic composition of the vegetation and the soil seed bank in different types of dunes of Kerqin steppe were compared. The aim of this study was to examine the influence of desertification on the floristic composition of the vegetation and soil seed bank. An indirect germination method was used to study the seed bank. Thirty species of the vegetation

Yulin Li; Jianyuan Cui; Xueyong Zhao; Halin Zhao

2004-01-01

264

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

PubMed

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 ?g/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 ?g/L and 23.74-118.27 ?g/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. PMID:24468500

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

2014-04-01

265

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

266

Terrestrial vegetation and water balance—hydrological evaluation of a dynamic global vegetation model  

Microsoft Academic Search

Earth's vegetation plays a pivotal role in the global water balance. Hence, there is a need to model dynamic interactions and feedbacks between the terrestrial biosphere and the water cycle. Here, the hydrological performance of the Lund–Potsdam–Jena model (LPJ), a prominent dynamic global vegetation model, is evaluated. Models of this type simulate the coupled terrestrial carbon and water cycle, thus

Dieter Gerten; Sibyll Schaphoff; Uwe Haberlandt; Wolfgang Lucht; Stephen Sitch

2004-01-01

267

Laboratorial simulation on soil erosion under different vegetation coverage in Southwest Karst Area, China  

Microsoft Academic Search

n Abstract-In order to understand soil erosion characteristics on different vegetation coverage in karst mountain area in southwest of China, 12 tests of soil erosion simulation were carried out according to the land surface features and meteorological data in this region. The results showed that slop runoff ratio which was after 180 ? 300s changed little, and the average runoff

Xiongfei Cai; Ji Wang; Yulun An; Wenli Dan

2011-01-01

268

Contamination of soil and vegetation near a zinc smelter by zinc, cadmium, copper, and lead  

Microsoft Academic Search

Metal oxide fumes escaping from two zinc smelters in Palmerton, Pa., have highly contaminated soil and vegetation with zinc, cadmium, copper, and lead. Within 1 km of the smelters, 135,000 parts per million (ppm) zinc, 1750 ppm cadmium, 2000 ppm copper, and 2000 ppm lead have been measured in the Oâ horizon. Approximately 90% of metals deposited on the soil

Marilyn J. Buchauer

1973-01-01

269

Alpine tussockland communities and vegetation-landform-soil relationships, Wapiti Lake, Fiordland, New Zealand  

Microsoft Academic Search

Classification and ordination of 139 plots and 207 species in a 2 km alpine area revealed nine tussockland communities within two broad community groups. The two community groups occupied different ends of a gradient in soil development, nutrient status, and drainage, indicating that soil factors were the dominant broad-scale influence on the vegetation. Within this pattern, the communities were mainly

A. B. Rose; J. B. J. Harrison; K. H. Platt

1988-01-01

270

Effects of Vegetation Cover on the Microwave Radiometric Sensitivity to Soil Moisture  

Microsoft Academic Search

The reduction in sensitivity of the microwave brightness temperature to soil moisture content due to vegetation cover is analyzed using airborne observations made at 1.4 and 5 GHz. The data were acquired during six flights in 1978 over a test site near Colby, Kansas. The test site consisted of bare soil, wheat stubble, and fully mature corn fields. The results

Fawwaz T. Ulaby; Mohammad Razani; Myron C. Dobson

1983-01-01

271

Spatial variability of soil and vegetation characteristics in an urban park in TelAviv  

Microsoft Academic Search

Mosaic-like spatial patterns, consisting of divers soil microenvironments, characterize the landscapes of many urban parks. These microenvironments may differ in their pedological, hydrological and floral characteristics, and they play important roles in urban ecogeomorphic system functioning. In and around a park covering 50 ha in Tel Aviv, Israel, soil properties and herbaceous vegetation were measured in eight types of microenvironments.

Pariente Sarah; Helena M. Zhevelev; Atar Oz

2010-01-01

272

The Vertical Distribution of Soil Organic Carbon and Its Relation to Climate and Vegetation  

Microsoft Academic Search

As the largest pool of terrestrial organic carbon, soils interact strongly with atmospheric composition, climate, and land cover change. Our capacity to predict and ameliorate the consequences of global change depends in part on a better understanding of the distributions and controls of soil organic carbon (SOC) and how vegetation change may affect SOC distributions with depth. The goals of

Esteban G. Jobbagy; Robert B. Jackson

2000-01-01

273

Fifteen Years of Vegetation and Soil Development after Brackish-Water  

Microsoft Academic Search

Aboveground biomass, macro-organic matter (MOM), and wetland soil characteristics were measured peri- odically between 1983 and 1998 in a created brackish- water marsh and a nearby natural marsh along the Pamlico River estuary, North Carolina to evaluate the development of wetland vegetation and soil de- pendent functions after marsh creation. Development of aboveground biomass and MOM was dependent on elevation

Marsh Creation; Christopher Craft; Stephen Broome; Carlton Campbell

274

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

PubMed

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

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

2012-03-01

275

Soil moisture inferences from thermal infrared measurements of vegetation temperatures  

NASA Technical Reports Server (NTRS)

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

Jackson, R. D. (principal investigator)

1981-01-01

276

Productivity of wet soils: Biomass of cultivated and natural vegetation  

Microsoft Academic Search

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

1988-01-01

277

INNOVATIVE APPROACHES FOR SOIL FUMIGATION IN VEGETABLE PRODUCTION SYSTEMS  

Technology Transfer Automated Retrieval System (TEKTRAN)

An apparatus was developed for injecting soil fumigants beneath raised planting beds covered by plastic mulch without disturbing the integrity of the beds. Soil fumigation using a mixture of 1,3-dichloropropene (1,3-D) and chloropicrin (Pic) was combined with abbreviated soil solarization periods, v...

278

Carbon in the Vegetation and Soils of Great Britain  

Microsoft Academic Search

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

R. Milne; T. A. Brown

1997-01-01

279

A distributed hydrology-vegetation model for complex terrain  

SciTech Connect

A distributed hydrology-vegetation model is described that includes canopy interception, evaporation, transpiration, and snow accumulation and melt, as well as runoff generation via the saturation excess mechanisms. Digital elevation data are used to model topographic controls on incoming solar radiation, air temperature, precipitation, and downslope water movement. Canopy evapotranspiration is represented via a two-layer Penman-Monteith formulation that incorporates local net solar radiation, surface meteorology, soil characteristics and moisture status, and species-dependent leaf area index and stomatal resistance. Snow accumulation and ablation are modeled using an energy balance approach that includes the effects of local topography and vegetation cover. Saturated subsurface flow is modeled using a quasi three-dimensional routing scheme. The model was applied at a 180-m scale to the Middle Fork Flathead River basin in northwestern Montana. This 2900-km{sup 2}, snowmelt-dominated watershed ranges in elevation from 900 to over 3000 m. The model was calibrated using 2 years of recorded precipitation and streamflow. The model was verified against 2 additional years of runoff and against advanced very high resolution radiometer based spatial snow cover data at the 1-km{sup 2} scale. Simulated discharge showed acceptable agreement with observations. The simulated areal patterns of snow cover were in general agreement with the remote sensing observations, but were lagged slightly in time. 42 refs., 10 figs., 1 tab.

Wigmosta, M.S.; Lettenmaier, D.P. [Univ. of Washington, Seattle, WA (United States)] [Univ. of Washington, Seattle, WA (United States); Vail, L.W. [Pacific Northwest Lab., Richland, WA (United States)] [Pacific Northwest Lab., Richland, WA (United States)

1994-06-01

280

Linear spectral mixture modelling to estimate vegetation amount from optical spectral data  

Microsoft Academic Search

Spectral mixture modelling has developed in recent years as a suitable remote sensing tool for analysing the biophysical and compositional character of ground surfaces. In this paper the potentiality of the linear spectral mixture model to extract vegetation related parameters from 0·4-2·5 ?m reflectance data has been tested. High spectral resolution reflectance measurements of soil-plant mixtures with different soil colour

F. J. GARCÍA-HARO; M. A. GILABERT; J. MELIÁ

1996-01-01

281

Can artificial soil be used in the vegetative vigor test for U.S. pesticide registration?  

PubMed

Current testing guidelines for pesticide registration for the protection of nontarget plants calls for the use of sterilized, standardized soil consisting of primarily sandy loam, loamy sand, loamy clay, or clay loam that contains up to 3% organic matter. Low organic matter soils can be difficult to manage in a greenhouse setting because when soils dry, they contract, causing impeded water infiltration, or when overwatered, poor drainage increases the chances of anaerobic conditions. The purpose of this study was to determine if the results for the vegetative vigor test differed when using either natural or artificial soils. The herbicide sulfometuron methyl was applied 14 d after emergence at 0.1 and 0.0032 of the suggested field application rate. Six plant species were tested, 4 of the common test species, Zea mays (corn), Glycine max (soybean), Avena sativa (oat), and Lactuca sativa (lettuce), and 2 native plants of the Willamette Valley, Oregon prairie, Bromus carinatus (California brome) and Ranunculus occidentalis (western buttercup). Herbicide application rate was the most significant factor in the experiment regardless of soil type. The different soils generally produced different results, even though the 2 native soils, one from Oregon and the other from Maryland, are both acceptable soils for the pesticide registration tests. The plants grown on artificial soil produced results generally between the Oregon and Maryland soil results. This study indicates that artificial soils may produce results similar to or more sensitive than soils currently used in the vegetative vigor test. PMID:18563958

Bidelspach, Conor; Olszyk, David; Pfleeger, Thomas

2008-10-01

282

Metal speciation in soil and health risk due to vegetables consumption in Bangladesh.  

PubMed

This study was conducted to investigate the contamination level of heavy metals in soil and vegetables, chemical speciation, and their transfer to the edible part of vegetables. Metals were analyzed using inductively coupled plasma mass spectrometer (ICP-MS). The ranges of Cr, Ni, Cu, As, Cd, and Pb in agricultural soils were 3.7-41, 3.9-36, 3.7-46, 2.3-26, 0.6-13, and 4.5-32 mg/kg, respectively. The metals were predominantly associated with the residual fractions of 39, 41, 40, 40, 34, and 41 % for Cr, Ni, Cu, As, Cd, and Pb, respectively. Considering the metal transfer from soil to the edible part of vegetables, the mean transfer factors (TFs) were in the descending order of Cu?>?Ni?>?Cr?>?Pb?>?As?>?Cd. In the edible tissues of vegetables, the concentrations of As, Cd, and Pb in most vegetable samples exceeded the maximum permissible levels, indicating not safe for human consumption. Total target hazard quotient (THQ) of the studied metals (except Cr) from all vegetables were higher than 1, indicated that if people consume these types of vegetables in their diet, they might pose risk to these metals. Total values of carcinogenic risk (CR) were 3.2 for As and 0.15 for Pb which were higher than the US Environmental Protection Agency (USEPA) threshold level (0.000001), indicating that the inhabitants consuming these vegetables are exposed to As and Pb with a lifetime cancer risk. PMID:25903407

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

2015-05-01

283

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

NASA Technical Reports Server (NTRS)

The 2-D difference vegetation index (DVI) and perpendicular vegetation index (PVI), and the 4-D green vegetation index (GVI) are compared in LANDSAT MSS data from grain sorghum (Sorghum bicolor, L. Moench) fields for the years 1973 to 1977. PVI and DVI were more closely related to LAI than was GVI. A new 2-D soil line index (SLI), the vector distance from the soil line origin to the point of intersection of PVI with the soil line, is defined and compared with the 4-D soil brightness index, SBI. SLI (based on MSS and MSS7) and SL16 (based on 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.

Wiegand, C. L.; Richardson, A. J. (principal investigators)

1982-01-01

284

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

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

285

[Soil microbial properties under different vegetation types in Loess hilly region].  

PubMed

By using fumigation-extract (FE) method and Biolog Ecoplate, this paper investigated the microbial biomass and diversity in 0-20 cm soil layer under five vegetation types, including artificial woodland, shrubland, cropland, abandoned farmland, and natural grassland, in Dingxi of Gansu Province. In the meanwhile, the relationships between soil microbes and soil nutrients were studied by path analysis, and the five typical vegetation types were evaluated from the aspect of soil microbes. Relative to cropland, "grain for green" project played a key role in improving soil microbial resources. Microbial biomass carbon was the highest in ridge grassland, abandoned farmland, and pine woodland, followed by in Caragana korshinskii land, Medicago sativa land, restored land, and roadside land, and in wheat field and potato field. Microbial biomass nitrogen was the highest in ridge land, abandoned farmland, Pinus tabulaeformis woodland, Caragana korshinskii land, and Medicago sativa land, followed by in restored land and roadside land, and in wheat field and potato field. Caragana korshinskii land and Medicago sativa land, due to the existence of N-fixing rhizobium, had the highest ratio of soil microbial biomass nitrogen to soil total nitrogen. Owing to the continual biomass loss and rare feedback, cropland had the lowest quantity and activity of soil microbes. Through planting trees, shrubs and grasses or through fallowing, soil microbial biomass and activity were recovered, and the effect was increased with time. In 20-year old Caragana korshinskii land, the quantity and activity of soil microbes were similar to those in 50-year old Pinus tabulaeformis woodland, and the microbial community catabolic activity and soil nutrient use efficiency were higher. Considering the features of soil microbes under test vegetation types, Caragana korshinskii would be a good choice for local vegetation restoration. PMID:20387439

Zhang, Yan-Yan; Qu, Lai-Ye; Chen, Li-Ding; Wei, Wei

2010-01-01

286

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

Microsoft Academic Search

Traditional methodologies for the characterization of volatile organic compounds (VOCs) in subsurface soil are expensive, time-consuming processes that are often conducted on samples collected at random. The determination of VOCs in near-surface soils and vegetation is the foundation for a more efficient sampling strategy to characterize subsurface soil and improve understanding of environmental problems.In the absence of a standard methodology

Jorge S Alvarado; Candace Rose

2004-01-01

287

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

Microsoft Academic Search

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

P. C. Miller; D. K. Poole

1983-01-01

288

Heterogeneity as an index of anthropogenic disturbance of soil and vegetation in urban Parks  

NASA Astrophysics Data System (ADS)

The conditions of urban ecosystems depend on a wide range of anthropogenic factors, one of which is visitor pressure on urban parks. This study aims: (1) to analyze soil properties and vegetation characteristics of different open areas, and (2) to determine an index of disturbance for these areas, according to their spatial heterogeneity. The study was conducted in Tel-Aviv, and addressed two scales: (1) Land Use Units (municipal parks and vacant lots); and (2) Microenvironment (under tree, under bush, herbaceous area, lawn, and path). In each type of microenvironment, soil was sampled at seven points, from layers at two depths (0-2 and 5-10 cm). Before the sampling, penetration depth, litter biomass and vegetation characteristics (vegetation cover, number of species, and vegetation height) were determined in the field. In each soil sample gravimetric soil moisture and organic matter contents were determined, and pH, electrical conductivity and soluble-ion contents were measured in a 1:1 water extraction. The level of disturbance by visitors was scored for each microenvironment according to field evidence of trampling, such as lack of vegetation cover and litter biomass. The results show strong differences in soil properties among the various microenvironments: penetration depth ranged from a few millimeters up to ~ 3 cm; organic matter content from less than 1% to 10%; soil moisture content from a few percents to ~ 30%; electrical conductivity from ~ 0.3 to ~2 dS/m; sodium content from ~ 1 to 7.5 meq/kg; chlorine content from ~ 0.5 to ~9 meq/kg; and litter biomass from 0.5 to 1.4 kg/m2. The vegetation characteristics also varied among the microenvironments: vegetation cover ranged from 11 to 99 %; number of species from 2 to11; and vegetation height from 5 to 35 cm. In order to assess the level of heterogeneity of soil and vegetation, an integral index, based on the number of Duncan groups, has been calculated. Regarding the Scale of Land Use unit, it was found that the highest heterogeneity of soil characteristics corresponded with the lowest species richness. For the smaller-scale unit - Microenvironment - an index was developed that defines the status of disturbance, and it was used to sort the microenvironments into several groups. High correlation between percentiles and averages of soil properties was found for the microenvironments. This hints at a fractal structure of soil properties distribution at the microenvironment level.

Zhevelev, H.; Sarah, P.

2012-04-01

289

Modeling Soil Freezing Dynamics  

Microsoft Academic Search

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

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

2002-01-01

290

Erosion of upland hillslope soil organic carbon: Coupling field measurements with a sediment transport model  

Microsoft Academic Search

Little is known about the role of vegetated hillslope sediment transport in the soil C cycle and soil-atmosphere C exchange. We combined a hillslope sediment transport model with empirical soil C measurements to quantify the erosion and temporal storage of soil organic carbon (SOC) within two grasslands in central California. The sites have contrasting erosional mechanisms: biological perturbation (Tennessee Valley

Kyungsoo Yoo; Ronald Amundson; Arjun M. Heimsath; William E. Dietrich

2005-01-01

291

Modelling Soil respiration in agro-ecosystems  

NASA Astrophysics Data System (ADS)

A soil respiration model was developed to simulate soil respiration in crops on a daily time step. The soil heterotrophic respiration component was derived from Century (Parton et al., 1987). Soil organic carbon is divided into three major components including active, slow and passive soil carbon. Each pool has its own decomposition rate coefficient. Carbon flows between these pools are controlled by carbon inputs (crop residues), decomposition rate and microbial respiration loss parameters, both of which are a function of soil texture, soil temperature and soil water content. The model assumes that all C decompositions flows are associated with microbial activity and that microbial respiration occurs for each of these flows. Heterotrophic soil respiration is the sum of all these microbial respiration processes. To model the soil autotrophic respiration component, maintenance respiration is calculated from the nitrogen content and assuming an exponential relationship to account for temperature dependence (Ryan et al., 1991). Growth respiration is calculated assuming a dependence on both growth rate and construction cost of the considered organ (MacCree et al., 1982) A database, made of four different soil and climate conditions in mid-latitude was used to study the two components of the soil respiration model in wheat fields. Soil respiration were measured in three winter wheat fields at Lamasquère (43°49'N, 01°23'E, 2007) and Auradé (43°54'N, 01°10'E, 2008), South-West France and Lonzée (50°33'N, 4°44'E, 2007), Belgium, and in a spring wheat field at Ottawa (45°22'N, 75°43'W, 2007, 2011), Ontario, Canada. Manual closed chambers were used in the French sites. The Belgium and Canadian sites were equipped with automated closed chamber systems, which continuously collected 30-min soil respiration exchanges. All the sites were also equipped with eddy flux towers. When eddy flux data were collected over bare soil, the net ecosystem exchange (NEE) was equal to 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.

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

2013-04-01

292

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

PubMed Central

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

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

2013-01-01

293

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)

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.

Sakalli, A.

2015-01-01

294

Climate-vegetation-soil interactions and long-term hydrologic partitioning: Signatures of catchment co-evolution (Invited)  

NASA Astrophysics Data System (ADS)

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=?(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 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 reveals that climates that give rise to more (less) E/P are associated with catchments that have vegetation with less (more) efficient water use parameters. In particular, the climates with tendency to produce more E/P have catchments that have lower % root fraction and less light use efficiency. Our results suggest that their exists strong interactions between climate, vegetation and soil properties that lead to specific hydrologic partitioning at the catchment scale. This co-evolution of catchment vegetation and soils with climate needs to be further explored to improve our capabilities to predict hydrologic partitioning in ungaged basins.

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

2013-12-01

295

Selenium content of Belgian cultivated soils and its uptake by field crops and vegetables.  

PubMed

A series of 695 food crops were collected on 539 soils throughout Belgium. All samples were collected on commercial production fields, omitting private gardens. All crops were analyzed for their selenium (Se) concentration. The soils represent different soil types occurring in Belgium, with soil textures ranging from sand to silt loam, and including a few clay soils. They were analyzed for Se concentration, organic carbon content, cation exchange capacity and extractable sulphur (S) concentration. The Se concentrations in the soils were low (range 0.14-0.70 mg kg(-1) dw), but increasing soil Se concentrations were observed with increasing clay content. Stepwise multiple regressions were applied to determine relations between Se concentrations in crops and soil characteristics. Among field crops, wheat is the most important accumulator of selenium but the concentration remains rather low on the Belgian low Se-soils. Based on dry weight, leafy vegetables contain more Se than wheat. The soil is the most important source of Se and the element is transported with the water stream to the leaves, where it is accumulated. Vegetables rich in S, e.g. some Brassica and Allium species, have a higher capacity to accumulate Se as it can replace S in the proteins, although this accumulation is still limited at low soil Se concentrations. In loamy soils, weak correlations were found between the soil Se concentration and its concentration in wheat and potato. The uptake of Se increased with increasing pH. The Se concentrations in Belgian soils are far too low to generate a driving force on Se uptake. General climatic conditions such as temperature, air humidity and soil moisture are also important for the transfer of Se within the plant, and plant linked factors such as cultivar, growth stage and edible part are important as well, although their influence remains limited at low soil Se concentrations. PMID:24013513

De Temmerman, Ludwig; Waegeneers, Nadia; Thiry, Céline; Du Laing, Gijs; Tack, Filip; Ruttens, Ann

2014-01-15

296

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)

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.

Tellers, T. E.

1980-01-01

297

Influence of vegetation spatial heterogeneity on soil enzyme activity in burned Mediterranean areas  

NASA Astrophysics Data System (ADS)

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, ?-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 ?-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 linearly with the total cover of vegetation patches, which is consistent with the strong effect of plant patches on the activity of this enzyme. According to our results, variations in the cover and composition of vegetation patches may have profound impacts on the soil enzyme activity and associated nutrient cycling processes in burned Mediterranean areas, particularly in the case of phosphorus. Keywords: wildfires, landscape metrics, Mediterranean shrublands, soil enzyme activity, resprouter species.

Mayor, Á. G.; Goirán, S.; Bautista, S.

2009-04-01

298

The effects of vegetation parameter aggregation on modeled evapotranspiration  

E-print Network

vegetation indices developed from satellite remote sensing images of the study area. Aggregation of the vegetation parameters followed a subcatchment scheme. The model was executed for one growing season for each subcatchment aggregation scheme...

Hoffpauir, Richard James

2001-01-01

299

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

PubMed Central

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

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

2008-01-01

300

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

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

301

Water status of soil and vegetation in a shortgrass steppe  

Microsoft Academic Search

In an attempt to describe some major relationships between soil and plant compartments in a shortgrass steppe, the process of water loss from the system and plant water relations throughout a drying cycle were studied. The water supply was manipulated and some soil and plant variables monitored throughout a drying cycle. Leaf conductance and leaf water potential of blue grama

O. E. Sala; W. K. Lauenroth; W. J. Parton; M. J. Trlica

1981-01-01

302

FIRE AND GRAZING EFFECTS ON VEGETATION AND BIOLOGICAL SOIL CRUSTS  

Technology Transfer Automated Retrieval System (TEKTRAN)

Biological soil crusts increase soil water retention and may enhance plant establishment. Crusts may be sensitive to disturbances, but little information is available on their response to fire and grazing in the Northern Plains. We measured cover on permanent plots in grazed, burned, and non-graze...

303

Modeling Vernal Pool Hydrology and Vegetation in the Sierra Nevadas  

NASA Astrophysics Data System (ADS)

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.

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

2012-12-01

304

Evolution of vegetation and soil nutrients after uranium mining in Los Ratones mine (Cáceres, Spain).  

PubMed

The evolution of vegetation structure following mine rehabilitation is rather scarce in the literature. The concentration of long-lived radionuclides of the (238)U series might have harmful effects on living organisms. We studied soil properties and the natural vegetation occurring along a gradient in Los Ratones, an area rehabilitated after uranium mining located in Cáceres, Spain. Soil and vegetation were sampled seasonally and physical and chemical properties of soil were analysed, including natural isotopes of (238)U, (230)Th, (226)Ra and (210)Pb. Species richness, diversity, evenness and plant cover were estimated and correlated in relation to soil physical and chemical variables. The location of the sampling sites along a gradient had a strong explanatory effect on the herbaceous species, as well as the presence of shrubs and trees. Seasonal effects of the four natural isotopes were observed in species richness, species diversity and plant cover; these effects were directly related to the pH values in the soil, this being the soil property that most influences the plant distribution. Vegetation in the studied area resembles that of the surroundings, thus proving that the rehabilitation carried out in Los Ratones mine was successful in terms of understorey cover recovery. PMID:24450758

Pérez-Fernández, María A; Vera-Tomé, Feliciano; Blanco-Rodríguez, María P; Lozano, Juan C

2014-06-01

305

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

PubMed

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

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

2013-08-01

306

Modeling soil freezing dynamics  

Technology Transfer Automated Retrieval System (TEKTRAN)

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 permea...

307

Monitoring soil-vegetation interactions using non-invasive geophysical techniques  

NASA Astrophysics Data System (ADS)

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 setup was created using four small-scale boreholes and a 2D array of surface electrodes. The soil response to irrigation and evapo-transpiration evidences the location of tree roots, including the influence of irrigation patterns on the root growth, and their efficiency at removing soil moisture.

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

308

Modeling the effects of historical vegetation change on near-surface atmosphere in the northern Chihuahuan Desert  

Technology Transfer Automated Retrieval System (TEKTRAN)

Our goal was to evaluate the effects of a broad-scale change in vegetation from grasslands in the mid-1800s to shrublands in the late 1900’s on weather and climate. Vegetation and soil maps for 1858 and 1998 were used to run a fully coupled atmospheric-biospheric model for two times during the growi...

309

Calibrating a Coupled SVAT-Vegetation Growth Model with Remotely Sensed Reflectance and Surface Temperature--A Case Study for the HAPEX-Sahel Grassland Sites  

Microsoft Academic Search

Models simulating the seasonal growth of vegetation have been recently coupled to soil-vegetation-atmosphere transfer schemes (SVATS). Such coupled vegetation-SVATS models (V-S) account for changes of the vegetation leaf area index (LAI) over time. One problem faced by V-S models is the high number of parameters that are required to simulate different sites or large areas. Therefore, efficient calibration procedures are

P. Cayrol; L. Kergoat; S. Moulin; G. Dedieu; A. Chehbouni

2000-01-01

310

Physically-based parameterization of spatially variable soil and vegetation using satellite multispectral data  

NASA Technical Reports Server (NTRS)

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.

Jasinski, Michael F.; Eagleson, Peter S.

1989-01-01

311

Water based microwave assisted extraction of thiamethoxam residues from vegetables and soil for determination by HPLC.  

PubMed

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 ?g 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. PMID:22065124

Karmakar, Rajib; Singh, Shashi Bala; Kulshrestha, Gita

2012-02-01

312

Fluoride accumulation in soil and vegetation in the vicinity of brick fields.  

PubMed

Fluoride in the soil and vegetation in the vicinity of brick field in the suburb of Lucknow, India was estimated. The water soluble fluoride (1:1) in the surface soil ranged from 0.59 ppm to 2.74 ppm where as CaCl(2) extractable fluoride ranged from 0.69 ppm to 3.18 ppm. The mean total fluoride concentration in surface soil varied from 322 microg g(-1) to 456 microg g(-1). The local vegetations grown in the area found to accumulate air borne fluoride from the brick field. The fluoride accumulation in the vegetation followed the order Mentha arvensis > Spinacea oleracea > Luffa cylindrical. PMID:18345473

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

2008-04-01

313

Post Chernobyl surveys of radiocaesium in soil, vegetation, wildlife and fungi in Great Britain  

NASA Astrophysics Data System (ADS)

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

Chaplow, J. S.; Beresford, N. A.; Barnett, C. L.

2014-12-01

314

Coincidence and spatial variability of geology, soils, and vegetation, Mill Run watershed, Virginia.  

USGS Publications Warehouse

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

Olson, C.G.; Hupp, C.R.

1986-01-01

315

Mapping the spectral variability in photosynthetic and non-photosynthetic vegetation, soils, and shade using AVIRIS  

NASA Technical Reports Server (NTRS)

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.

Roberts, Dar A.; Smith, Milton O.; Sabol, Donald E.; Adams, John B.; Ustin, Susan L.

1992-01-01

316

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

NASA Technical Reports Server (NTRS)

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.

Macari, Emir Jose

1990-01-01

317

Understory vegetation leads to changes in soil acidity and in microbial communities 27 years after reforestation.  

PubMed

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. PMID:25261818

Fu, Xiaoli; Yang, Fengting; Wang, Jianlei; Di, Yuebao; Dai, Xiaoqin; Zhang, Xinyu; Wang, Huimin

2015-01-01

318

Relations between soil moisture and satellite vegetation indices in the U.S. Corn Belt  

USGS Publications Warehouse

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.

Adegoke, J.O.; Carleton, A.M.

2002-01-01

319

[Sizes of soil macropores and related main affecting factors on a vegetated basalt slope].  

PubMed

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

Guan, Qi; Xu, Ze-Min; Tian, Lin

2013-10-01

320

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

PubMed Central

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

He, Xunyang; Liu, Lu; Wang, Kelin

2014-01-01

321

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

PubMed

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

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

2014-01-01

322

Agricultural use of soil, consequences in soil organic matter and hydraulic conductivity compared with natural vegetation in central Spain  

NASA Astrophysics Data System (ADS)

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 0.7±1.1 % soil organic matter; far from the usual limit advisable for cultivated soils. Soil porosity was also affected in cultivated soils, being 39±5% (total porosity), significantly less than those found under Stipa (46%) and Quercus (51%). Hydraulic conductivity presented a similar pattern to porosity, being higher in soils under Quercus, however further research is needed to clarify this result, as it can also be related to changes detected in soil texture. Sand content, which was different between soil conditions, is highly correlated to hydraulic conductivity. Changes in soil texture can be due to erosive processes that have to be studied to establish the causative relationships between these findings. Acknowledgements: Project CGL 2008-04296. Environmental Impact evaluation through the assessment of soil organic matter resilient forms in soils.

Vega, Verónica; Carral, Pilar; Alvarez, Ana Maria; Marques, Maria Jose

2014-05-01

323

Influence of Vegetations' Metabolites on the Composition and Functioning of Soil Microbial Complex  

NASA Astrophysics Data System (ADS)

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 incubation the rate of mineralisation of organic substances was assessed with CO2 measurements. In 5, 10 and 21 days of incubation the enzymatic properties of the formed MC were studied by the hydrolysis of fluorogenic substrates. The influence of BAS on enzymatic properties of MC were researched by addition of different concentrations of phenolic acids (e.g. salicylic, vanillic, benzoic, etc.) to the samples from various substrates treatments. The acute toxicity of BAS was studied with bacterial luminescent test. After the last measurement, the isolations of microorganisms on elective nutrient medias were made. The dominant microorganisms were collected to the library for further identification and physiological tests. MeOH-chloroform extraction of phospholipids were performed with the remaining samples. Finally, they were stored for subsequent FAME identifications. The obtained data prove that penetration of various substrates into the soil determines the formation of MC different in structure and properties. It was found, that EC50 of the most studied phenolic acids are similar to naturally occurring concentrations. This means that they can be the real drivers of forming endemical MC under various vegetations along with the plant-specific fluxes of nutrients.

Biryukov, Mikhail

2013-04-01

324

Vegetation and climate controls on potential CO2, DOC and DON production in northern latitude soils  

USGS Publications Warehouse

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 climate.

Neff, J.C.; Hooper, D.U.

2002-01-01

325

ORIGINAL ARTICLE Responses of vegetation to soil disturbance by Sibelian  

E-print Network

; this is an example of a keystone species acting as an ecosystem engineer (Adiya 2000; Yoshihara et al. 2009a Ecosystem engineer; keystone species; landscape richness enhancement; susceptibility to disturbance; zoning rodent in Mongolia, and play many impor- tant roles, such as increasing species diversity of vegetation

Schweik, Charles M.

326

Evaluation of Thematic Mapper for detecting soil properties under grassland vegetation  

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

327

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

NASA Astrophysics Data System (ADS)

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

Peters, Emily B.; McFadden, Joseph P.

2012-09-01

328

Salt-marsh Vegetation and Morphology: Basic Physiology, Modelling and Remote Sensing Observations  

Microsoft Academic Search

The state and evolution of a tidal salt marsh are crucially dependent on the interplay between sediment input and transport, eustatism, hydrodynamic regimes and biotic factors (e.g. vegetation colonization). Biotic factors have a decisive influence on sediment deposition, resuspension and compaction but are, in turn, governed by numerous physical factors (e.g. soil salinity and oxygen availability). A model that can

Sonia Silvestri; Marco Marani

329

Effect of land-use practice on soil moisture variability for soils covered with dense forest vegetation of Puerto Rico  

NASA Technical Reports Server (NTRS)

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.

Tsegaye, T.; Coleman, T.; Senwo, Z.; Shaffer, D.; Zou, X.

1998-01-01

330

Classification of Soil Moisture on Vegetated Earthen Levees Using X and L Band Synthetic Aperture Radar (SAR)  

NASA Astrophysics Data System (ADS)

Earthen levees protect large areas of land in the US from flooding. Timely inspection and repairs can reduce the potential for catastrophic failures. Changes in spatial and temporal patterns of soil moisture can reveal signs of instability and help identify zones of weakness. Since analytical and empirical models have shown a relationship between SAR backscatter and soil moisture, we are using SAR to classify soil moisture on levees. Estimation of soil moisture from SAR is challenging when the surface has any significant vegetation. For the levee application, the soil is typically covered with a uniform layer of grass. Our methodology is based on a supervised soil moisture classification using a back propagation neural network with four classes of low, medium, high, and very high soil moisture. Our methodology consists of the following steps: 1) segmentation of the levee area from background and exclusion of tree-covered areas; 2) extracting the backscattering and texture features such as GLCM (Grey-Level Co-occurrence Matrix) and wavelet features; 3) training the back propagation neural network classifier; and 4) testing the area of interest and validation of the results using ground truth data. Two sources of SAR imagery are tested with this method: (1) fully polarimetric L-band data from NASA's UAVSAR; and (2) dual-polarimetric X-band data from the German TerraSAR-X satellite. The study area is a 4 km stretch of levee along the lower Mississippi River in the United States. Field data collected simultaneously with image acquisition are utilized for training and validation. Preliminary results show classification accuracies of about 50% for the UAVSAR image and 30% for the TerraSAR-X image in vegetated areas. The figure below shows a soil moisture classification using UAVSAR on April 28, 2011.

Mahrooghy, M.; Aanstoos, J. V.; Hasan, K.; Nobrega, R. A.; Younan, N. H.

2011-12-01

331

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

NASA Technical Reports Server (NTRS)

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

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

1987-01-01

332

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

USGS Publications Warehouse

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 lowlands on ice-poor eolian sand and (4) peaty–silty lowlands on thick ice-rich peat deposits over reworked lowland loess. In rocky uplands, after fire permafrost thawed rapidly due to low ice contents, soils became well drained and SOC stocks decreased slightly. In silty uplands, after fire permafrost persisted, soils remained saturated and SOC decreased slightly. In gravelly–sandy lowlands where permafrost persisted in drier forest soils, loss of deeper permafrost around lakes has allowed recent widespread drainage of lakes that has exposed limnic material with high SOC to aerobic decomposition. In peaty–silty lowlands, 2–4 m of thaw settlement led to fragmented drainage patterns in isolated thermokarst bogs and flooding of soils, and surface soils accumulated new bog peat. We were not able to detect SOC changes in deeper soils, however, due to high variability. Complicated soil stratigraphy revealed that permafrost has repeatedly aggraded and degraded in all landscapes during the Holocene, although in silty uplands only the upper permafrost was affected. Overall, permafrost thaw has led to the reorganization of vegetation, water storage and flow paths, and patterns of SOC accumulation. However, changes have occurred over different timescales among landscapes: over decades in rocky uplands and gravelly–sandy lowlands in response to fire and lake drainage, over decades to centuries in peaty–silty lowlands with a legacy of complicated Holocene changes, and over centuries in silty uplands where ice-rich soil and ecological recovery protect permafrost.

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

333

Soil, water, and vegetation conditions in south Texas  

NASA Technical Reports Server (NTRS)

The author has identified the following significant results. Software development for a computer-aided crop and soil survey system is nearing completion. Computer-aided variety classification accuracies using LANDSAT-1 MSS data for a 600 hectare citrus farm were 83% for Redblush grapefruit and 91% for oranges. These accuracies indicate that there is good potential for computer-aided inventories of grapefruit and orange citrus orchards with LANDSAT-type MSS data. Mean digital values of clouds differed statistically from those for crop, soil, and water entities, and those for cloud shadows were enough lower than sunlit crop and soil to be distinguishable. The standard errors of estimate for the calibration of computer compatible tape coordinate system (pixel and record) to earth coordinate system (longitude and latitude) for 6 LANDSAT scenes ranged from 0.72 to 1.50 pixels and from 0.58 to 1.75 records.

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

1976-01-01

334

Soil, water, and vegetation conditions in South Texas  

NASA Technical Reports Server (NTRS)

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

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

1976-01-01

335

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

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

336

Environmental controls on the 34S/32S ratios of soil and vegetation  

NASA Astrophysics Data System (ADS)

Climate and landscape age strongly affect most soil processes, however their impact on the terrestrial sulfur (S) cycle is poorly known. In this study, we examine how S isotope composition changes in soils and plants along gradients of climate (Tanzania, Hawaii, California, Great Plains) and age (California). As a model, we assume (as is the case for C and N) that soil S pools are largely at steady state, representing the balance between inputs and losses. The same assumption is made for isotopes: the ?34S value of soil S (in most cases dominantly in organic form) represents the value of inputs and the S isotope fractionation between the losses and the soil S it is derived from. While the geographic variation in the isotopic composition of atmospheric S inputs is not well known at this stage, conducting gradient analyses in confined areas (where S inputs should be constant), allows us to examine how forms of S loss vary with climate and time. For the African (Kilimanjaro) transect, as elevation increases, both mean annual precipitation (MAP) and mean annual temperature (MAT) decrease. Mean ?34S values increase with elevation up a value of 17.9‰ at 2545 m, and then decrease from 2990 m, to a minimum of 8.8‰ at 3900 m. The higher ?34S values at lower elevations, where the climate is wetter and warmer, indicate that the forms of S losses are relatively depleted in 34S , suggesting gaseous losses along with sulfate leaching. The Hawaiian transect mirrors that of Africa at comparable MAP and MAT conditions, suggesting both similar sources, but most importantly similar in-soil responses to temperature/moisture combinations. In contrast, the Great Plain soils, which are significantly drier and somewhat cooler than the Kilimanjaro and Hawaii soils, have ?34S values ranging from -3.3 to +3.8‰, likely as a result of a combination of more 34S-depleted atmospheric inputs and smaller losses of S-depleted sulfate given the drier climate. For the Sierra Nevada transect, MAP increases and MAT decreases with increasing elevation, while the average ?34S values of vegetation increases only slightly. For most tree samples, leaves are slightly more enriched in 34S than the stems, however no clear difference is seen between different plant types at the same site, or between plants and soil, indicating that there is little to no fractionation during plant uptake. On the Merced chronosequence, biomass ?34S values initially increase with age (5.8, 6.1, 6.3 and 6.7‰ for the 3 ky, 6 ky, 150 ky and 600 ky soils respectively) and then decrease on the most ancient terraces (6.0 and 5.3‰ for the 1 and 3 My soils respectively). At this stage, there appears to be similarities in the patterns of S isotopes and our previous work along these same transects on N isotopes (Amundson et al., 2003), indicating (as we hypothesized) a common response of these somewhat similar biological elements to climate. However, increasing our knowledge of the mechanisms underlying these emerging patterns is the goal of our on-going work.

Balan, S. A.; Laleian, A.; Portier, E.; Amundson, R.

2010-12-01

337

Interacting vegetative and thermal contributions to water movement in desert soil  

USGS Publications Warehouse

Thermally driven water-vapor flow can be an important component of total water movement in bare soil and in deep unsaturated zones, but this process is often neglected when considering the effects of soil-plant-atmosphere interactions on shallow water movement. The objectives of this study were to evaluate the coupled and separate effects of vegetative and thermal-gradient contributions to soil water movement in desert environments. The evaluation was done by comparing a series of simulations with and without vegetation and thermal forcing during a 4.7-yr period (May 2001-December 2005). For vegetated soil, evapotranspiration alone reduced root-zone (upper 1 m) moisture to a minimum value (25 mm) each year under both isothermal and nonisothermal conditions. Variations in the leaf area index altered the minimum storage values by up to 10 mm. For unvegetated isothermal and nonisothermal simulations, root-zone water storage nearly doubled during the simulation period and created a persistent driving force for downward liquid fluxes below the root zone (total net flux ~1 mm). Total soil water movement during the study period was dominated by thermally driven vapor fluxes. Thermally driven vapor flow and condensation supplemented moisture supplies to plant roots during the driest times of each year. The results show how nonisothermal flow is coupled with plant water uptake, potentially influencing ecohydrologic relations in desert environments. ?? Soil Science Society of America 5585 Guilford Rd., Madison, WI 53711 USA. All rights reserved.

Garcia, C.A.; Andraski, B.J.; Stonestrom, D.A.; Cooper, C.A.; Simunek, J.; Wheatcraft, S.W.

2011-01-01

338

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

NASA Astrophysics Data System (ADS)

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

Schneider, Sébastien; Jacques, Diederik; Mallants, Dirk

2010-05-01

339

Mineralisation of atrazine, metolachlor and their respective metabolites in vegetated filter strip and cultivated soil.  

PubMed

In vegetated filter strips (VFS) the presence of perennial vegetation, rhizodeposition of labile organic substrates and the accumulation of an organic residue thatch layer may enhance microbial numbers and activity, thereby increasing the potential for mineralisation of herbicides and herbicide metabolites retained during run-off events. The objective of this laboratory experiment was to compare the mineralisation of atrazine and metolachlor with that of their respective metabolites in VFS and cultivated soil. With the exception of total bacteria, propagule density of the microbial groups, endogenous soil enzymes and microbial diversity were higher in the VFS soil. This correlated with increased mineralisation of metolachlor and its metabolites in the VFS soil and indicates potential for VFS to curtail the subsequent transport of these compounds. In contrast, the mineralisation of atrazine and the majority of its metabolites was substantially reduced in VFS soil relative to cultivated soil. Consequently, the potential for subsequent transport of atrazine and many of its metabolites may be greater in VFS soil than in cultivated soil if reduced mineralisation is not offset by increased sorption in the VFS. PMID:16612813

Krutz, Larry J; Gentry, Terry J; Senseman, Scott A; Pepper, Ian L; Tierney, Dennis P

2006-06-01

340

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

341

The impact of parent material, climate, soil type and vegetation on Venetian forest humus forms: a direct gradient approach  

E-print Network

1 The impact of parent material, climate, soil type and vegetation on Venetian forest humus forms and vegetation on forest humus forms was studied in the Veneto Region (northern Italy). A total of 352 study, warmer climate associated to lower elevation, lower soil acidity, deciduous (as opposed to coniferous

Boyer, Edmond

342

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

SciTech Connect

Changes in the distribution of vegetation types under altered climate regimes could have important consequences for the storage of atmospheric carbon in terrestrial ecosystems. Because there are relatively few definitive field studies of changes in whole ecosystem carbon balance under modified climate stress, process-level models driven by gridded global databases may provide reasonable indicators of biome-specific sensitivity of C storage 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{degrees}) satellite imagery on a monthly time interval to simulate seasonal patterns in net ecosystem carbon balance and steady-state carbon storage in detritus and 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 concentrations 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.

Klooster, S.A.; Potter, C.S. [NASA-Ames Research Center, Moffett Field, CA (United States)

1995-09-01

343

Modelling of groundwater-vegetation interactions in a tidal marsh  

NASA Astrophysics Data System (ADS)

Wetting and drying due to tidal fluctuations affect soil conditions and hence plant growth in tidal marshes. Here, a coupled one-dimensional model was developed to simulate interacting groundwater flow and plant growth in these wetlands. The simulation results revealed three characteristic zones of soil conditions for plant growth along a cross-creek section subjected to the combined influences of spring-neap tides and evapotranspiration: (1) a near-creek zone affected by semi-diurnal tides over the whole spring-neap cycle, where the soil is well aerated although the plant growth could be slightly limited by the local water content dropping periodically below the wilting point on the ebb tide; (2) a less well-drained zone where drainage occurs only during neap tides (for which the daily inundation is absent) and plant growth is aeration-limited; and (3) an interior zone where evapotranspiration determines the soil-water saturation. Plant growth dynamics, which depend on these soil conditions, lead to spatial biomass distributions that are consistent with the characteristic zonation. The simulations shed light on the feedback mechanism for groundwater-vegetation interactions in the marsh system. It was demonstrated that the growth of pioneer plants can improve the soil aeration condition as a result of transpiration. The strength of this feedback varies spatially in accordance with the three characteristic zones of soil-water saturation. However, the development of another species in the marsh system is likely to be more complicated than suggested by the "positive feedback" mechanism proposed previously, due to the influence of inter-species competition. The feedback effects are generally more complex, involving both plant growth enhancement and inhibition depending on the combined influence of the intra- and inter-species competition, the ecosystem's carrying capacity and plant transpiration. These findings demonstrate the interplay of ecological and hydrological processes in tidal marshes, and provide guidance for future research, including field investigations that aim to establish the principle relationship between marsh morphology and plant zonation.

Xin, Pei; Kong, Jun; Li, Ling; Barry, D. A.

2013-07-01

344

COMMENTARY - SPATIAL VARIATION OF SOIL PROPERTIES RELATING TO VEGETATION CHANGES  

Technology Transfer Automated Retrieval System (TEKTRAN)

Bekele and Hudnall provide an interesting perspective on the spatial variation of soil chemical properties in a natural area undergoing transition from prairie to forest. Their focus is on the unique calcareous prairie ecosystem of Louisiana where prairie remnants are being encroached upon by the f...

345

Soil changes after four years of organic vegetable production  

Technology Transfer Automated Retrieval System (TEKTRAN)

In 2002, scientists at the Lane Agricultural Center in southeastern Oklahoma began a study to explore the potential for organic agricultural production. Land was certified as organic according to the guidelines of the National Organic Program. At the beginning of the study, soil samples were taken...

346

Trace elements in vegetables grown in an industrial area in relation to soil and air particulate matter  

Microsoft Academic Search

The relationships between the trace element content of vegetables, agricultural soil and airborne particulate matter were investigated in the greater industrial area of Thessaloniki, northern Greece. Most elements were found at concentrations normally observed in vegetables grown in uncontaminated areas, however, elevated concentrations of Pb, Zn, Cr and Mn were found particularly in leafy vegetables. The trace element content of

D. Voutsa; A. Grimanis; C. Samara

1996-01-01

347

Soil seed bank recovery occurs more rapidly than expected in semi-arid Mediterranean gypsum vegetation  

PubMed Central

Background and Aims Seed banks are critical in arid ecosystems and ensure the persistence of species. Despite the importance of seed banks, knowledge about their formation and the extent to which a seed bank can recover after severe perturbation remains scarce. If undisturbed, soil seed banks reflect a long vegetation history; therefore, we would expect that new soil seed banks and those of undisturbed soils require long periods to become similar with respect to both density and composition. In contrast, if soil seed banks are only a short- to mid-term reservoir in which long-term accumulation constitutes only a tiny fraction, they will recover rapidly from the vegetation. To shed light on this question, we evaluated seed bank formation in a semi-arid gypsum community. Methods Soils from 300 plots were replaced with sterilized soil in an undisturbed semi-arid Mediterranean community. Seasonal changes in seed bank density and composition were monitored for 3 years by comparing paired sterilized and control soil samples at each plot. Key Results Differences in seed bank density between sterilized and control soil disappeared after 18 months. The composition of sterilized seed banks was correlated with that of the control plots from the first sampling date, and both were highly correlated with vegetation. Nearly 24 % of the seed bank density could be attributed to secondary dispersal. Most seeds died before emergence (66·41–71·33 %), whereas the rest either emerged (14·08–15·48 %) or persisted in the soil (14·59–18·11 %). Conclusions Seed banks can recover very rapidly even under the limiting and stressful conditions of semi-arid environments. This recovery is based mainly on the seed rain at small scales together with secondary dispersal from intact seed banks in the vicinity. These results emphasize the relevance of processes occurring on short spatial scales in determining community structure. PMID:22003238

Olano, J. M.; Caballero, I.; Escudero, A.

2012-01-01

348

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

SciTech Connect

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

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

1995-08-01

349

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

PubMed

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

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

2005-10-01

350

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

351

REMOVAL AND DEGRADATION OF ATRAZINE AND METOLACHLOR BY VEGETATIVE FILTER STRIPS ON CLAY LOAM SOIL  

Microsoft Academic Search

The effectiveness of filter strips, with and without vegetation, in removing dissolved atrazine and metolachlor in runoff was investigated using aluminum tilted beds set at 1% slope on Cullen clay loam soil. Runon containing atrazine and metolachlor was applied on the up-slope end of the simulated filter strips. Water samples from surface runoff, lateral subsurface movement, and leachates as well

Cathy Seybold; Wondi Mersie; Don Delorem

2001-01-01

352

Soil erosion and runoff in different vegetation patches from semiarid Central Mexico  

Technology Transfer Automated Retrieval System (TEKTRAN)

Vegetation patches in arid and semiarid areas are important in the regulation of surface hydrological processes. Canopy and ground cover in these fertility islands develop a natural cushion against the impact energy of rainfall, and the higher levels of organic matter improve soil physicochemical pr...

353

Vegetation controls on soil organic carbon dynamics in an arid, hyperthermic ecosystem  

Microsoft Academic Search

The large land area occupied by arid lands, roughly 36% to 40% globally, underscores the importance for understanding how these ecosystems function in the global carbon cycle. Few studies have directly examined soil organic carbon (SOC) dynamics and the effect of vegetation on SOC and microbial community structure in arid ecosystems. The objective of this study was to determine the

David A. White II; Amy Welty-Bernard; Craig Rasmussen; Egbert Schwartz

2009-01-01

354

Vegetation and climate controls on potential CO2, DOC and DON production in northern latitude soils  

E-print Network

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 types at two of those sites (upland spruce at Fairbanks, and wet sedge and shrub tundra at Toolik Lake

Neff, Jason

355

Late-Holocene glacier growth in Svalbard, documented by subglacial relict vegetation and living soil microbes  

Microsoft Academic Search

Much renewed research interest in Arctic regions stems from the increasing concentration of atmospheric greenhouse gases and the alleged climatic sensitivity of high latitude areas. Glacier and permafrost changes are among a number of proxies used for monitoring past and present Arctic climate change. Here we present observations on frozen in situ soil and vegetation, found below cold-based glacier Longyearbreen

Ole Humlum; Bo Elberling; Anne Hormes; Kristine Fjordheim; Odd Harald Hansen; Jan Heinemeier

2005-01-01

356

Impact of soil type on vegetation response to prairie dog herbivory  

Technology Transfer Automated Retrieval System (TEKTRAN)

Prairie dogs and their impact on vegetation have been the focus of numerous research projects. However, the effect of soil from this interaction has been less thoroughly documented. We evaluated prairie dog colonies (on-colony) and nearby sites without prairie dogs (off-colony) on Wayden, Cabba an...

357

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

EPA Science Inventory

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

358

Evaluating MODIS Vegetation Indices as Ancillary Data in the Retrieval of Soil Moisture from Microwave Data  

Microsoft Academic Search

One approach to soil moisture retrieval from remotely sensed microwave data uses single frequency H polarization brightness temperature measurements. This algorithm requires ancillary information to estimate the effective temperature of the surface and the attenuation of the microwave signal by vegetation. When applied on a global basis using spaceborne microwave observations, such as AMSR-E, it is most efficient if the

A. Y. Hsu; T. J. Jackson

2005-01-01

359

Heavy metals in industrial wastewater, soil and vegetables in Lohta village, India  

Microsoft Academic Search

A field study was conducted at four major sites that were irrigated by either treated or untreated wastewater in the Lohta village of Varanasi, India, receiving the discharged water from DLW (Diesel Locomotive Works) sewage treatment plant. Samples of irrigation water, soil and the edible portion of various vegetables were collected monthly during the summer and winter seasons. Heavy metals

Prabhat Kumar Rai; B. D. Tripathi

2008-01-01

360

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

E-print Network

Author's personal copy Soil and vegetation as the determinants of lake nitrogen concentrations Sciences Research Program, Department of Biology, University of Victoria, P.O. Box 3020, STN CSC, Victoria rivers and lakes within forested areas. The remaining 20% of the population draws water from large lakes

Mazumder, Asit