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1

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

2

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

3

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

NASA Technical Reports Server (NTRS)

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

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

1998-01-01

4

Advantages of a Topographically Controlled Runoff Simulation in a Soil Vegetation Atmosphere Transfer Model  

Microsoft Academic Search

Two methods to incorporate subgrid variability in soil moisture and runoff production into soil-vegetation- atmosphere transfer (SVAT) models are compared: 1) the variable infiltration capacity model approach (VIC), and 2) a modified ''TOPMODEL'' approach. Because neither approach needs to track surface or subsurface flow within a catchment explicitly, they represent computationally efficient ways to represent hydrologic processes within the context

Kirsten Warrach; Marc Stieglitz; Heinz-Theo Mengelkamp; Ehrhard Raschke

2002-01-01

5

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

6

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

7

Modification of a soil–vegetation nonlinear interaction model with acid deposition for simplified experimental applicability  

Microsoft Academic Search

In this work we modified a theoretical model of acid deposition in the soil–vegetation interaction to be experimentally applicable. We simplified the expression of the mathematical model of dynamical complex systems by setting parameters into more simple groups, giving an easy-of-validate expression. By the theoretical model it was proposed the nonlinear response of vegetation to acid deposition, which can explain

Sebastián Guala; Flora A. Vega; Emma F. Covelo

2009-01-01

8

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 (5-200gm(-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

9

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

NASA Astrophysics Data System (ADS)

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: (I) a mixed Deschampsia/Mosses field, (II) a moss carpet of Sanionia uncinata and (III) a grass field of Deschampsia Antarctica. Soil respiration was measured in a 60-point regularly spaced grid previously installed at each site. The grid size was 3 x 1.5 meter with a minimum distance of 0.5 m between grid points in March 2009 during the morning at site I and afternoon at sites II and III. The spatial variability was analyzed by using descriptive statistics and the adjustment of the semivariogram models to the soil respiration and soil temperature data. The model adjusted to the semivariogram was used in order to generate the so-called kriging map by interpolation techniques, estimating the studied property at non-sampled places. Higher mean emission was observed in the Deschampsia field (4.13 µmol m-2 s-1), but the highest variability was detected in the mixed vegetation site I. The overall results indicate that soil temperature is not directly related to the spatial pattern of the soil respiration in the studied sites. The degree of spatial dependence was moderate for emission in all studied sites. Temperature values presented degree of spatial dependence classified as strong for sites I and III and moderate in site II. CO2 emission ranges were 1.29, 2.23 and 2.79 m for sites I - II - III, respectively. Higher range values observed in site II and III suggest higher emission homogeneity. In mixed vegetation at site I, points under Deschampsia Antarctica had an overall higher mean respiration (1.49 µmol m-2 s-1) compared with remaining points under mosses tuffs (1.32 µmol m-2 s-1). Kriging maps of soil CO2 emission and soil temperature indicate a more continuity of isolines for emission maps from sites II and III. This can also be observed in soil temperature maps, suggesting that vegetation cover may also control the continuity or discontinuity of both properties in space. Therefore distribution of soil respiration and soil temperature did not appear to be related to soil type, but more associated to the vegetation type and distribution at each site.

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

2010-05-01

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 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

11

Numerical modelling of snow and frozen soil processes for a multi-layer atmosphere-soil-vegetation model  

NASA Astrophysics Data System (ADS)

Snowcover plays an important role in Earth's climate system because of its high albedo, low thermal conductivity, roughness length, and ability to store water. A sophisticated process-based snow model is useful for representing the complex snow physics. In the present study, an existing multi-layer atmosphere-SOiL-VEGetation model (SOLVEG) developed by the authors was modified to simulate snow and frozen soil processes. The schemes of a multi-layer snow structure for heat and liquid water transports in snow and freeze-thaw processes of soil moisture were incorporated into the model. In the snow scheme, the liquid water transfer in snow was modeled based on the processes of both capillary rise and gravitational drainage in order to accurately simulate water movement in unsaturated snow. The performance of the modified model was tested at the pre-alpine grassland site in TERestrial ENvironmental Observatories (TERENO) networks in Germany. The modified model overall reproduced the temporal changes in observations of surface energy fluxes, albedo, snow depth and surface temperature, and soil temperature and moisture. The measured increases of soil water content due to infiltration of melted snow to the soil were simulated by the modified model. The observed large negative sensible and positive latent heat fluxes associated with the typical south foehn, a warm and dry downslope wind of the Alps, were also reproduced in the simulation.

Katata, Genki; Mauder, Matthias

2014-05-01

12

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

13

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

14

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

15

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

16

Development and validation of a dynamical atmosphere-vegetation-soil HTO transport and OBT formation model.  

PubMed

A numerical model simulating transport of tritiated water (HTO) in atmosphere-soil-vegetation system, and, accumulation of organically bound tritium (OBT) in vegetative leaves was developed. Characteristic of the model is, for calculating tritium transport, it incorporates a dynamical atmosphere-soil-vegetation model (SOLVEG-II) that calculates transport of heat and water, and, exchange of CO(2). The processes included for calculating tissue free water tritium (TFWT) in leaves are HTO exchange between canopy air and leaf cellular water, root uptake of aqueous HTO in soil, photosynthetic assimilation of TFWT into OBT, and, TFWT formation from OBT through respiration. Tritium fluxes at the last two processes are input to a carbohydrate compartment model in leaves that calculates OBT translocation from leaves and allocation in them, by using photosynthesis and respiration rate in leaves. The developed model was then validated through a simulation of an existing experiment of acute exposure of grape plants to atmospheric HTO. Calculated TFWT concentration in leaves increased soon after the start of HTO exposure, reaching to equilibrium with the atmospheric HTO within a few hours, and then rapidly decreased after the end of the exposure. Calculated non-exchangeable OBT amount in leaves linearly increased during the exposure, and after the exposure, rapidly decreased in daytime, and, moderately nighttime. These variations in the calculated TFWT concentrations and OBT amounts, each mainly controlled by HTO exchange between canopy air and leaf cellular water and by carbohydrates translocation from leaves, fairly agreed with the observations within average errors of a factor of two. PMID:21665337

Ota, Masakazu; Nagai, Haruyasu

2011-09-01

17

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

18

Vegetation and soil characteristics data in the COSMO-CLM and WRF regional climate models  

NASA Astrophysics Data System (ADS)

The paper investigates the vegetation and soil characteristics time invariant boundary data of two regional climate models CCLM (COnsortium for Small-scale MOdeling - COSMO in CLimate Mode) and WRF (Weather Research and Forecasting Model). The available choice of the data is presented and the interchangeability from CCLM point of view is investigated. In several runs of the CCLM with ERA40 and NCEP boundary forcings the question how the selected invariant boundary influences actual CCLM simulations is addressed. The considered model domain is the MED-CORDEX (Mediterranean COordinated Regional Climate Downscaling Experiment) area. Despite of incompatibilities in the land use and soil texture category definitions a principal suitability of all investigated data sets was found. Variations in the modeling results introduced by the specific choice of time invariant boundary reach up 1.1 K in the area monthly mean temperature and up to 18% in the area mean precipitation. In total they are in range of the variations which result from the choice of reanalysis data. Thus, addition efforts in improvement of the time invariant boundary data applied in SVAT models associated with regional climate models can help to reduce the uncertainty in the modeling results.

Smiatek, Gerhard

2014-05-01

19

Validation and comparison of two soil-vegetation-atmosphere transfer models for tropical Africa  

NASA Astrophysics Data System (ADS)

This study aims to compare and validate two soil-vegetation-atmosphere-transfer (SVAT) schemes: TERRA-ML and the Community Land Model (CLM). Both SVAT schemes are run in standalone mode (decoupled from an atmospheric model) and forced with meteorological in-situ measurements obtained at several tropical African sites. Model performance is quantified by comparing simulated sensible and latent heat fluxes with eddy-covariance measurements. Our analysis indicates that the Community Land Model corresponds more closely to the micrometeorological observations, reflecting the advantages of the higher model complexity and physical realism. Deficiencies in TERRA-ML are addressed and its performance is improved: (1) adjusting input data (root depth) to region-specific values (tropical evergreen forest) resolves dry-season underestimation of evapotranspiration; (2) adjusting the leaf area index and albedo (depending on hard-coded model constants) resolves overestimations of both latent and sensible heat fluxes; and (3) an unrealistic flux partitioning caused by overestimated superficial water contents is reduced by adjusting the hydraulic conductivity parameterization. CLM is by default more versatile in its global application on different vegetation types and climates. On the other hand, with its lower degree of complexity, TERRA-ML is much less computationally demanding, which leads to faster calculation times in a coupled climate simulation.

Akkermans, T.; Lauwaet, D.; Demuzere, M.; Vogel, G.; Nouvellon, Y.; Ardö, J.; Caquet, B.; de Grandcourt, A.; Merbold, L.; Kutsch, W.; van Lipzig, N.

2012-06-01

20

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

21

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 diffi- cult. 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

JAMES W. RAICH; AYDIN TUFEKCIOGLU

2000-01-01

22

Evaluation of Snow Depth and Soil Temperatures Predicted by the Hydro Thermodynamic Soil Vegetation Scheme Coupled with the Fifth-Generation Pennsylvania State University NCAR Mesoscale Model  

Microsoft Academic Search

The Hydro Thermodynamic Soil Vegetation Scheme (HTSVS) coupled in a two-way mode with the fifth-generation Pennsylvania State University National Center for Atmospheric Research (NCAR) Mesoscale Meteorological Model (MM5) is evaluated for a typical snowmelt episode in the Baltic region by means of observations at 25 soil temperature, 355 snow-depth, and 344 precipitation sites that have, in total, 1000, 1775, and

Balachandrudu Narapusetty; Nicole Mölders

2005-01-01

23

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

24

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

25

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)

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

26

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

NASA Astrophysics Data System (ADS)

Rationale: Floodplain meadows are highly species-rich grassland ecosystems, unique in that their vegetation and soil structures have been shaped and maintained by ~1,000 yrs of traditional, low-intensity agricultural management. Widespread development on floodplains over the last two centuries has left few remaining examples of these once commonplace ecosystems and they are afforded high conservation value by British and European agencies. Increased incidences and severity of summer drought and winter flooding in Britain in recent years have placed floodplain plant communities under stress through altered soil moisture regimes. There is a clear need for improved management strategies if the last remaining British floodplain meadows are to be conserved under changing climates. Aim: As part of the Floodplain Underground Sensors Experiment (FUSE, a 3-year project funded by the Natural Environment Research Council) we aim to understand the environmental controls over soil-vegetation-atmosphere transfers (SVAT) of water, CO2 and energy at Yarnton Mead, a floodplain meadow in southern England. An existing model, SCOPE (Soil Canopy Observation, Photochemistry and Energy fluxes; van der Tol et al., 2009), uses remotely-sensed infrared radiance spectra to predict heat and water transfers between a vegetation canopy and the atmosphere. We intend to expand SCOPE by developing a more realistic, physically-based representation of water, gas and energy transfers between soil and vegetation. This improved understanding will eventually take the form of a new submodel within SCOPE, allowing more rigorous estimation of soil-canopy-atmosphere exchanges for the site using predominantly remotely-sensed data. In this context a number of existing SVAT models will be tested and compared to ensure that only reliable and robust underground model components will be coupled to SCOPE. Approach: For this study, we parameterised an existing and widely-used SVAT model (CoupModel; Jansson, 2011) for our study site and analysed the model's sensitivity to a comprehensive set of soil/plant biophysical processes and parameter values. Findings: The sensitivity analysis indicates those processes and parameters most important to soil-vegetation-atmosphere transfers at the site. We use the outcomes of the sensitivity analysis to indicate directly the desired structure of the new SCOPE submodel. In addition, existing soil-moisture, soil matric-potential and meteorological data for the site indicate that evapotranspiration is heavily water-limited during summer months, although soil moisture and soil matric-potential data alone provide very little explanation of the ratio of potential to actual evapotranspiration. A mechanistic representation of stomatal resistance and its response to short-term changes in meteorological conditions - independent of soil moisture status - will also likely improve SCOPE's predictions of heat and water transfers. Ultimately our work will contribute to improved understanding and management of floodplain meadows in Britain and elsewhere.

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

2011-12-01

27

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

28

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

29

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

Microsoft Academic Search

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 microwave brightness temperatures in a way that produces bias at coarser scales (kilometers). The physics underlying soil moisture remote sensing suggests that the effects of topography on

Alejandro N. Flores; Valeriy Y. Ivanov; Dara Entekhabi; Rafael L. Bras

2009-01-01

30

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

31

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

NASA Astrophysics Data System (ADS)

Distributed hydrology-soil-vegetation model (DHSVM) uses a digital elevation model (DEM) and accounts for topographic effects on soil moisture, groundwater, and surface water redistribution in a complex terrain. In this study, DHSVM is used to simulate soil moisture, net radiation and stream flow in a 1-km2 tropical mountainous watershed in Pang Khum, Chang Mai, Thailand. Pang Khum Experimental Watershed (PKEW) has two meteorological stations, four soil moisture stations, and one stream flow station at basin outlet. Meteorological measurements are used as forcing data for DHSVM. The grid resolution for this simulation is 50 m. Initial soil and vegetation parameter settings based on field measurements and literature review are adjusted through model calibration. The model is run for a six month warm-up period, followed by a calibration period of approximately one year. Validation is done for two periods totaling 18 months. At the forested site, net radiation is reasonably well simulated, although underestimated in the dry season, and overestimated in the wet season. At the agricultural site, net radiation is consistently overestimated. Soil moisture is well simulated at the forest site. In the simulation, the water table rises into the soil zone during the wet season, saturating all three soil layers at the agricultural site; measured values remained at unsaturated levels. Baseflow is significantly underestimated in calibration and validation periods. Difficulty in simulating streamflow may be caused by road-related effects in the basin. Our prior field work has shown that the road significantly alters runoff in PKEW. The principal mechanism of road-induced effects is Horton Overland Flow (HOF) generated on the road surface. In its present form DHSVM can account for interception of subsurface flow by roads, but not HOF generated on the road. We do not think subsurface flow interception is important in PKEW, and have therefore not implemented the road in our simulation. In future applications, we hope to include road effects, including HOF generation. As far as we know, this is the first application of DHSVM in a tropical location. Also, we apply the model over a very small watershed using a smaller grid-cell size than prior applications. Overall, we find the model to perform reasonably well despite being applied in a region and at a scale that contrast strongly with those in which it was developed. >http://webdata.soc.hawaii.edu/climate/Roads1/Roads.html

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

2001-12-01

32

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

33

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

34

Gophers and grassland: a model of vegetation response to patchy soil disturbance  

Microsoft Academic Search

We present a computer model which simulates population processes and spatial patterning in response to gopher disturbance in an annual grassland community. The model includes the processes of seed production, dispersal, germination and seedling survival of four main grassland species. Runs show that soil disturbance by gophers affects both short-term spatial patterning and long-term species composition. The main determinant of

R. J. Hobbs; V. J. Hobbs

1987-01-01

35

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

NASA Astrophysics Data System (ADS)

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

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

2010-03-01

36

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

37

Calibration and Uncertainty Analysis of Water and Solute Transport Models Within Vegetated Soils Using a Detailed Dataset  

NASA Astrophysics Data System (ADS)

Appropriate models predicting the fate and transport of water and dissolved chemicals in vegetated soils are required for a wide range of applications. Substantial uncertainty is present due to measurement errors, parametric uncertainty, and structural issues related to model conceptualisation. Due to the costs and intrusiveness of subsurface measurements there are limited datasets available to interrogate models against. Furthermore, the models are typically computationally intensive, making it difficult to fully explore parametric and other uncertainty spaces. Hence there are two pressing needs which must be met to improve the utility of models: more data and constraints are needed to quantify the interactions between different uncertainties and their overall impact on the reliability and robustness of model outputs, and efficient methodologies to explore sensitivities and uncertainties are also called for. This paper presents a combined analysis of a particularly detailed dataset and models of water and solute movement, using both simple random search and Markov chain Monte Carlo methods. Data was collected from an outdoor vegetated lysimeter facility over a duration of close to a year, with soil matric potential, moisture content and temperature at 10 cm depth intervals, along with rainfall and other meteorological variables, logged in four instrumented lysimeters at a time interval of 0.01 days. Three radionuclides (Na-22, Cl-36 and Cs-137) were supplied through the base of the lysimeters using an automated water table control system. Periodic soil cores and plant cuttings provided information on their migration and uptake. The integrity of the experimental data is examined, with uncertainty associated with outputs discussed and quantified. To interpret the data, a Richards' equation model coupled to a dynamic plant water model is linked to an advection-dispersion model with additional process representations of sorption, radioactive decay and root uptake. Structural uncertainty, parameterisation issues, and perturbation effects due to erroneous inputs are discussed. It is shown that although parameters are difficult to constrain in a univariate sense, consideration of model structure allows constraints on parametric interactions and hence a significant reduction of the parametric space that must be sampled. The efficiency of Markov Chain Monte Carlo techniques is demonstrated. However, despite the unusually comprehensive experimental dataset, major issues of uncertainty remain, of which data issues are a dominant component.

Jackson, B.; Wheater, H.; Butler, A.

2006-12-01

38

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

39

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...

40

MANAGING VEGETATION DYNAMICS: SOIL-GEOMORPHIC MAPS, STATE-AND-TRANSITION MODELS, AND REMOTE SENSING  

Technology Transfer Automated Retrieval System (TEKTRAN)

Vegetation mapping via remote sensing tools is a useful and cost-effective approach for understanding current land use and species habitat patterns, but has limited utility in predicting the future state of vegetation. We describe an approach that couples data-supported, conceptual state-and-transi...

41

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

42

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

43

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

44

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

45

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

Microsoft Academic Search

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

M. K. RIDD

1995-01-01

46

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

47

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

48

Modelling vegetated dune landscapes  

NASA Astrophysics Data System (ADS)

This letter presents a self-organising cellular automaton model capable of simulating the evolution of vegetated dunes with multiple types of plant response in the environment. It can successfully replicate hairpin, or long-walled, parabolic dunes with trailing ridges as well as nebkha dunes with distinctive deposition tails. Quantification of simulated landscapes with eco-geomorphic state variables and subsequent cluster analysis and PCA yields a phase diagram of different types of coastal dunes developing from blow-outs as a function of vegetation vitality. This diagram indicates the potential sensitivity of dormant dune fields to reactivation under declining vegetation vitality, e.g. due to climatic changes. Nebkha simulations with different grid resolutions demonstrate that the interaction between the (abiotic) geomorphic processes and the biological vegetation component (life) introduces a characteristic length scale on the resultant landforms that breaks the typical self-similar scaling of (un-vegetated) bare-sand dunes.

Baas, A. C. W.; Nield, J. M.

2007-03-01

49

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

50

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

51

Calculations of radar backscattering coefficient of vegetation-covered soils  

NASA Technical Reports Server (NTRS)

The present investigation has the objective to develop a simple 'user's' model for simulating the measured radar backscattering coefficients from vegetation-covered fields in conjunction with the data obtained by Jackson et al. (1980, 1982). The theoretical work reported by Fung and Eom (1981) provides the basis for the model. Certain modifications are related to a consideration of the effect of a vegetation canopy. The first part of the model is concerned with a description of scatter from rough bare soil, while the second part takes into account the effect of a vegetation cover. It is shown that the measured angular distribution of the backscattering coefficient of vegetation-covered fields can be satisfactory reproduced by using the developed model.

Mo, T.; Schmugge, T. J.; Jackson, T. J.

1984-01-01

52

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

53

Trace metal uptake by tropical vegetables grown on soil amended with urban sewage sludge.  

PubMed

Trace metal uptake was measured for tropical and temperate leafy vegetables grown on soil from an urban sewage disposal farm in the UK. Twenty-four leafy vegetables from East Africa and the UK were assessed and the five vegetable types that showed the greatest Cd concentrations were grown on eight soils differing in the severity of contamination, pH and other physico-chemical properties. The range of Cd concentrations in the edible shoots was greater for tropical vegetables than for temperate types. Metal uptake was modelled as a function of (i) total soil metal concentration, (ii) CaCl(2)-soluble metal, (iii) soil solution concentration and (iv) the activity of metal ions in soil pore water. Tropical vegetables were not satisfactorily modelled as a single generic 'green vegetable', suggesting that more sophisticated approaches to risk assessment may be required to assess hazard from peri-urban agriculture in developing countries. PMID:21129831

Nabulo, G; Black, C R; Young, S D

2011-02-01

54

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

NASA Technical Reports Server (NTRS)

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

Eagleson, P. S.

1982-01-01

55

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

56

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

PubMed

Vegetation indexes were the most common and the most important parameters to characterizing large-scale terrestrial ecosystems. It is vital to get precise vegetation indexes for running land surface process models and computation of NPP change, moisture and heat fluxes over surface. Biological soil crusts (BSC) are widely distributed in arid and semi-arid, polar and sub-polar regions. The spectral characteristics of dry and wet BSCs were quite different, which could produce much higher vegetation indexes value for the wet BSC than for the dry BSC as reported. But no research was reported about whether the BSC would impact on regional vegetation indexes and how much dry and wet BSC had impact on regional vegetation indexes. In the present paper, the most common vegetation index NDVI were used to analyze how the moss soil crusts (MSC) dry and wet changes affect regional NDVI values. It was showed that 100% coverage of the wet MSC have a much higher NDVI value (0.657) than the dry MSC NDVI value (0.320), with increased 0.337. Dry and wet MSC NDVI value reached significant difference between the levels of 0.000. In the study area, MSC, which had the average coverage of 12.25%, would have a great contribution to the composition of vegetation index. Linear mixed model was employed to analyze how the NDVI would change in regional scale as wet MSC become dry MSC inversion. The impact of wet moss crust than the dry moss crust in the study area can make the regional NDVI increasing by 0.04 (14.3%). Due to the MSC existence and rainfall variation in arid and semi-arid zones, it was bound to result in NDVI change instability in a short time in the region. For the wet MSC's spectral reflectance curve is similar to those of the higher plants, misinterpretation of the vegetation dynamics could be more severe due to the "maximum value composite" (MVC) technique used to compose the global vegetation maps in the study of vegetation dynamics. The researches would be useful for detecting and mapping MSC from remote sensing imagery. It also is to the advantage to employing vegetation index wisely. PMID:21595239

Fang, Shi-bo; Zhang, Xin-shi

2011-03-01

57

Vegetation and Soil Restoration on Highly Impacted  

E-print Network

We assessed the effectiveness of planting techniques (seeding and transplanting) and restoration treatments designed to improve the physical, biological, and chemical properties of soils and ameliorate microclimatic condi-tions on six closed campsites in subalpine forests. Restoration treatments included scarification, soil amendment with organic matter, compost and soil inoculum, and application of a mulch blanket. Campsite closure, scarifi-cation, planting, and soil amendments were successful in increasing recovery rates. The mulch blanket had no effect on recovery. 10 years after campsite closure, vegetation cover was still diminished in comparison to ref-erence conditions on nearby undisturbed sites. Particularly problematic was reestablishment of the low-growing shrub species (particularly Vaccinium scoparium and Phyllodoce empetriformis) that are the most abundant groundcover species in these forests. These species seldom establish from seed. Moreover, survivorship and growth rates are unusually low for transplants. Our results show the relative ease of establishing various spe-cies and growth forms in these forests, as well as which species and growth forms respond best to the applied treatments. Results reinforce the importance of avoiding impacts in the first place, the lengthy recovery periods

Forest Service; Rocky Mountain; Campsites In; The Eagle Cap; David N. Cole; David R. Spildie; David N. Spildie; David R. Vegetation

2007-01-01

58

Passive Microwave Soil Moisture Disaggregation radar data and relationship between soil moisture, vegetation and surface temperature  

NASA Astrophysics Data System (ADS)

Soil moisture is an important variable in weather and climate. The passive microwave sensors have provided soil moisture of various spatial resolutions and are available for all-weather conditions, including AMSR-E (Advanced Microwave Scanning Radiometer- Earth Observing System), AMSR2 (Advanced Microwave Scanning Radiometer 2) and SMOS (Soil Moisture and Ocean Salinity). However, the spatial resolution of passive microwave soil moisture product is restricted at tens of kilometers level and needs to be improved. Toward this issue, the SMAP (Soil Moisture Active Passive) is set to be launched in October 2014 will be the first mission to provide L-band radar/radiometer soil moisture retrievals at three resolutions. In this paper we present two distinct methods to obtain higher spatial resolution soil moisture. The first one is use of active radar data to downscale soil moisture obtained by passive radiometers. The SMAP Validation Experiment 2012 (SMAPVEX12) was taken place and provided Passive/Active L-band Sensor (PALS) observations of two along-track resolutions (650 m and 1590 m), as well as ground soil moisture measurements. Consequently the PALS data can be used for disaggregating coarse resolution passive soil moisture retrievals. Based on a change detection theory, the relationships between change in radar backscatter and change in soil moisture at both coarse and fine resolutions are examined and used for calculating high spatial resolution soil moisture from AMSR-E and SMOS. Using SMAPVEX12 ground measurements validates the disaggregation results. The second method is use of the relationship between vegetation and surface temperature to downscale soil moisture obtained from passive radiometers. The physical relationships amongst soil moisture, land surface temperature and vegetation index (Normalized Difference Vegetation Index, NDVI), the historic soil moisture data of recent 30 years at 1/8 degree NLDAS (North America Land Data Assimilation Systems) scale were studied and modeled by using the long term records of land surface model and remote sensing products, NLDAS, MODIS (Moderate Resolution Imaging Spectroradiometer) and AVHRR (Advanced Very High Resolution Radiometer). This modeled relationship was then applied to the 1 km MODIS land surface temperature for disaggregating the microwave soil moisture estimates AMSR-E and SMOS in Oklahoma. Two sets of in-situ measurements Oklahoma Mesonet and Little Washita watershed Micronet were used for validating the disaggregated soil moisture.

Lakshmi, Venkat; Fang, Bin

2014-05-01

59

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

60

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

61

Soil erosion under different vegetation covers in the Venezuelan Andes  

Microsoft Academic Search

This comparative study of soil erosion considered different environments in an ecological unit of the Venezuelan Andes. The soils belong to an association of typic palehumults and humic dystrudepts. Soil losses were quantified by using erosion plots in areas covered by four types of vegetation, including both natural and cultivated environments. The highest soil erosion rate evaluated corresponded to horticultural

Luz Amelia Sánchez; Michele Ataroff; Roberto López

2002-01-01

62

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

63

Microwave remote sensing of soil moisture with vegetation effect  

NASA Astrophysics Data System (ADS)

The objectives of this study were: to examine the sensitivity of radar backscatter, to estimate soil moisture under a corn plot and to evaluate the effectiveness and sensitivity of a Radiative Transfer Model (RTM), adapted from the earlier work of Njoku and Kong, (1977) in predicting brightness temperature from a grass plot. Microwave radar measurements were collected from plots of different vegetation cover types, vegetation density, and moisture conditions during the Huntsville 1998 field experiment. A large amount of ground data on brightness temperatures, soil moisture, and vegetation characteristics (e.g., biomass, and water content) were collected. The experiments were conducted at Alabama A&M University's, Winfred Thomas Agricultural Research Station, located near Hazel Green, Alabama. Six plots, one 50 X 60 m smooth bare plot, one 50 X 60 m grass plot, and four 30 X 50 m corn plots at full, 2/3, 1/2, and 1/3 densities were used. Radar backscatter data were obtained from a ground based truck mounted radar operating at L, C, and X bands (1.6, 4.75, and 10 GHz) with four linear polarization HH, HV, VV, and VH and two incidence angles (15 and 45 degrees). Soil moisture values were determined using Water Content Reflectometry (WCR). Three types of soil temperature sensors (Infrared Thermometer, Thermistor, and a 4-sensor averaging thermocouple probes) were used. A discrete backscatter approach model and RTM were evaluated. Comparisons between model prediction and experimental observation for HH polarization indicated good agreement for a corn full plot. The direct-reflected scattering coefficient is found to be the most dominant term for both polarization and the backscatter is also highly sensitive to soil moisture. The trends in time variation of brightness temperature are in agreement with the experimental results and the numerical results are within a few percent of the experimental results. The vegetation corrections as estimated by the Jackson and Schmugge method are very small. Detailed examination of the vegetation canopy contribution including the geometry of the canopy, the various absorption and scattering mechanisms are necessary.

Tsegaye, Teferi D.; Inguva, Ramarao; Lang, Roger H.; O'Neill, Peggy E.; Fahsi, Ahmed; Coleman, Tommy L.; Tadesse, Wubishet; Rajbhandari, Narayan B.; Aburemie, Sunnie A.; de Matthaeis, Paolo

1999-12-01

64

Using Distributed Snow Data to Evaluate and Improve the Performance of the Distributed Soil Hydrology Vegetation Model (DHSVM): a test case from the northeastern U.S  

NASA Astrophysics Data System (ADS)

Internal validation of physically-based hydrologic models using distributed field measurements has been increasingly recognized as an important approach for testing model performance and improving model skill. We are evaluating the performance of the Distributed Soil Hydrology Vegetation Model (DHSVM) to model snowmelt and runoff in mountainous watersheds in the northeastern U.S. Our test cases include a forested control watershed and a watershed managed as an alpine ski area. Empirical results from these watersheds show substantial differences in annual water yield between the watersheds that are highly correlated to annual snowpack magnitude. An underlying objective of our research is to explore the effects of ski area development, in particular the size, spatial arrangement and orientation of ski runs and base village development on runoff production. In this application, we use distributed snow pack measurements to validate distributed model simulations of snow accumulation and melt. We also explore the use of an automated model calibration approach, utilizing our distributed snow measurements, to improve model skill. Future work will make use of these exploratory simulations as we attempt to model the effects of ski area development under different design scenarios and climate conditions.

del Peral, A.; Wemple, B.

2011-12-01

65

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

Microsoft Academic Search

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

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

2007-01-01

66

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 T. R. Moore (2009), Soil drainage and vegetation controls of nitrogen transformation rates in forest] Comprehension of the environmental controls of nitrogen (N) transformation in forest ecosystems is critical

Moore, Tim

67

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...

68

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

69

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

70

Evaluation of Landsat Thematic Mapper for vegetated alluvium soils information  

NASA Technical Reports Server (NTRS)

Landsat Thematic Mapper data acquired over Mississippi County, Arkansas, on August 22, 1982, were evaluated whether TM provides information that could be used for soil association maps and if soil properties (variability within vegetated fields) can be detected with the new bands on TM. It was found that TM data - especially the mid-IR and thermal bands - show the capability for separating vegetated soil landscapes on a broad basis. Analysis at the field level with a crop growing indicates that TM, with its additional and narrower bands and improved spatial resolution is influenced by within-field variability due to soils.

Thompson, D. R.; Henderson, K. E.; Houston, A. G.; Pitts, D. E.

1983-01-01

71

Measurement of soil hydraulic conductivity in relation with vegetation  

NASA Astrophysics Data System (ADS)

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

Chen, Xi; Cheng, Qinbo

2010-05-01

72

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

Microsoft Academic Search

The effects of soil optical properties on vegetation index imagery are analysed 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 'colour’ differences among bare soils, and soil-vegetation spectral mixing. Primary variations were

A. R. HUETE; C. J. TUCKER

1991-01-01

73

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

NASA Astrophysics Data System (ADS)

In the country with limited resources, where the nutrition level of the population has to be maintained under inhospitable situation, the potato has a special value as food. Therefore efforts should be made for improvement and spreading the cultivation of this important crop. It demands an effective program that may provide information about potato growing areas and the growth conditions. Remote sensing has been acknowledged to be a valuable source of spatially comprehensive and temporally repeatable information of crop covered soil moisture, crop growth climatic information etc, which is useful and necessary for agriculture purposes. For this purpose, microwave remote sensing has evolved as an important tool. Since microwave are able to penetrate more deeply into vegetation and underneath ground surface. It is also preferred to the optical frequency band because microwave can work in all type of weather and have a wide signal dynamic range compared optical wavelengths. However interpretation of microwave scattering from agricultural crops requires an understanding the interaction among microwave, vegetative material and the soil. In order to develop useful forward and inverse models for retrieving the vegetation characteristic, it is necessary to know in detail the dielectric properties and plant structure of the vegetation over the range of expected growing conditions. In this paper, a theoretical model based on microwave interaction with potato crop along with examination of biomass of potato crop with the varying underlying soil moisture is studied. For this purpose, X-band (9.5GHz) scatterometer is used for studying the interaction of microwave with potato crop biomass and underlying soil moisture at various sensor parameters (i.e. angular variation and polarization, HH- and VV-). Although there may be a lot of crop parameters (i.e. crop height, leaf area index, etc) which also gives their effect on microwave. All this parameters are interlinked in the crop. So, this study is focused on biomass, which is one of the main parameter of crop and related with dielectric. Scattering coefficient at X-band showed strong sensitivity to different growth cycle of potato. The soil effect on scattering coefficient was prominent at steeper incidence angle (less than 40 degree) where as potato plant effects are more dominant at higher incidence angle (more than 40 degree). The microwave response of potato is polarization dependent and is more prominent for VV-Pol than HH-Pol at every stages of growth of potato and this strong polarization dependence can play a strong role for crop discrimination. The dependency of scattering coefficient on biomass is statistically checked by the linear regression analysis and results of regression analysis confirm the experimental results i.e., scattering coefficient increases as the biomass increases in the potato crop. The best angle to observe and retrieve the biomass by scattering coefficient is 55 degree and 60 degree incidence angles for HH-Pol and VV-Pol respectively. The regression results also revealed that scattering coefficient is positively correlated with soil moisture for both like pols. This result follows many earlier findings. The best incidence angle to compute the potato covered soil moisture from scattering coefficient is 35 degree and 30 degree for HH- and VV-Pol respectively. The HH- pol has edge over VV-pol for observing the potato the covered soil moisture. This approach provides a new direction to understand the potato scattering at X-band for remote sensing.

Singh, Keshev

74

A Vegetated Urban Canopy Model for Meteorological and Environmental Modelling  

NASA Astrophysics Data System (ADS)

An urban canopy model is developed for use in mesoscale meteorological and environmental modelling. The urban geometry is composed of simple homogeneous buildings characterized by the canyon aspect ratio ( h/ w) as well as the canyon vegetation characterized by the leaf aspect ratio (? l ) and leaf area density profile. Five energy exchanging surfaces (roof, wall, road, leaf, soil) are considered in the model, and energy conservation relations are applied to each component. In addition, the temperature and specific humidity of canopy air are predicted without the assumption of thermal equilibrium. For radiative transfer within the canyon, multiple reflections for shortwave radiation and one reflection for longwave radiation are considered, while the shadowing and absorption of radiation due to the canyon vegetation are computed by using the transmissivity and the leaf area density profile function. The model is evaluated using field measurements in Vancouver, British Columbia and Marseille, France. Results show that the model quite well simulates the observations of surface temperatures, canopy air temperature and specific humidity, momentum flux, net radiation, and energy partitioning into turbulent fluxes and storage heat flux. Sensitivity tests show that the canyon vegetation has a large influence not only on surface temperatures but also on the partitioning of sensible and latent heat fluxes. In addition, the surface energy balance can be affected by soil moisture content and leaf area index as well as the fraction of vegetation. These results suggest that a proper parameterization of the canyon vegetation is prerequisite for urban modelling.

Lee, Sang-Hyun; Park, Soon-Ung

2008-01-01

75

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

PubMed

Two multimedia models are used to investigate the effect of a vegetation compartment on the environmental partitioning of dichlorodiphenyltrichloroethane (DDT): a steady-state unit world model using global averages of vegetation cover and land-to-sea ratio and a dynamic model with latitudinal zones and zone-specific vegetation types and annual temperature courses. The vegetation compartment represents canopies of deciduous and coniferous forests and blades of grasses; the organic carbon content of the vegetation-covered soil is higher than in the bare soil. In the steady-state model, transfer from the air to the vegetation and the underlying soil as well as revolatilization from the foliage and reduced deposition to the soil is observed, depending on the chemical's degradation rate constant in vegetation and the deposition velocities of the gaseous and particle-bound fractions. In both models, a significant effect of the organic carbon content of the vegetation-covered soil increasing the effect of the vegetation compartment is observed. In the steady-state model, the changes in the DDT concentrations in air do not exceed 7% difference between the cases with and without vegetation; the soil concentrations differ by maximally a factor of 2.7. In the spatially and temporally resolved model, however, air concentration differences up to 90% are observed, depending on the type and amount of vegetation in the latitudinal zones. Long-range transport is less pronounced in the model with vegetation. PMID:15046353

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

2004-03-01

76

Mercury concentrations in oligohaline wetland vegetation and associated soil biogeochemistry  

Microsoft Academic Search

Concentrations of mercury were determined in above- and below-ground tissues of dominant plant species, as well as soils,\\u000a in the wetlands of Lake Maurepas, Louisiana. Indicators of wetland soil biogeochemical status, such as soil redox potential,\\u000a pore-water nutrient concentrations, and pore-water total sulfides, were also determined. Total mercury concentrations in plant\\u000a tissues were within the typical range for vegetation not

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

77

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

78

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

PubMed

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

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

2014-01-01

79

Scaling dimensions in spectroscopy of soil and vegetation  

NASA Astrophysics Data System (ADS)

The paper revises and clarifies definitions of the term scale and scaling conversions for imaging spectroscopy of soil and vegetation. We demonstrate a new four-dimensional scale concept that includes not only spatial but also the spectral, directional and temporal components. Three scaling remote sensing techniques are reviewed: (1) radiative transfer, (2) spectral (un)mixing, and (3) data fusion. Relevant case studies are given in the context of their up- and/or down-scaling abilities over the soil/vegetation surfaces and a multi-source approach is proposed for their integration. Radiative transfer (RT) models are described to show their capacity for spatial, spectral up-scaling, and directional down-scaling within a heterogeneous environment. Spectral information and spectral derivatives, like vegetation indices (e.g. TCARI/OSAVI), can be scaled and even tested by their means. Radiative transfer of an experimental Norway spruce ( Picea abies (L.) Karst.) research plot in the Czech Republic was simulated by the Discrete Anisotropic Radiative Transfer (DART) model to prove relevance of the correct object optical properties scaled up to image data at two different spatial resolutions. Interconnection of the successive modelling levels in vegetation is shown. A future development in measurement and simulation of the leaf directional spectral properties is discussed. We describe linear and/or non-linear spectral mixing techniques and unmixing methods that demonstrate spatial down-scaling. Relevance of proper selection or acquisition of the spectral endmembers using spectral libraries, field measurements, and pure pixels of the hyperspectral image is highlighted. An extensive list of advanced unmixing techniques, a particular example of unmixing a reflective optics system imaging spectrometer (ROSIS) image from Spain, and examples of other mixture applications give insight into the present status of scaling capabilities. Simultaneous spatial and temporal down-scaling by means of a data fusion technique is described. A demonstrative example is given for the moderate resolution imaging spectroradiometer (MODIS) and LANDSAT Thematic Mapper (TM) data from Brazil. Corresponding spectral bands of both sensors were fused via a pyramidal wavelet transform in Fourier space. New spectral and temporal information of the resultant image can be used for thematic classification or qualitative mapping. All three described scaling techniques can be integrated as the relevant methodological steps within a complex multi-source approach. We present this concept of combining numerous optical remote sensing data and methods to generate inputs for ecosystem process models.

Malenovský, Zbyn?k; Bartholomeus, Harm M.; Acerbi-Junior, Fausto W.; Schopfer, Jürg T.; Painter, Thomas H.; Epema, Gerrit F.; Bregt, Arnold K.

2007-05-01

80

Determining soil and ground water use of vegetation from heat pulse, water potential and stable isotope data  

Microsoft Academic Search

A simple model of water uptake by vegetation is used to aid the discrimination of plant water sources determined with isotope data. In the model, water extracted from different soil depths depends on the leaf–soil potential difference, a root distribution function and a lumped hydraulic conductance parameter. Measurements of plant transpiration rate, and soil and leaf water potentials are used

P. G. Cook; A. P. O’Grady

2006-01-01

81

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

82

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

83

Forest Environment of Vietnam: Features of Forest Vegetation and Soils  

Microsoft Academic Search

Accounting for 57% of its entire national area, the forests and forestland of Vietnam cover about 19 million hectares (ha),\\u000a of which 12.6 million ha is covered by forests (MARD 2005). Because of its diverse climate conditions and complicated topography, Vietnam has a wide range of vegetation and soil types.\\u000a The forest vegetation includes six major types: (i) evergreen and

Vu Tan Phuong

84

GATOR-GCMM: A global- through urban-scale air pollution and weather forecast model, 1. Model design and treatment of subgrid soil, vegetation, roads, rooftops, water, sea ice, and snow  

NASA Astrophysics Data System (ADS)

A model that treats nesting of gas, size- and composition-resolved aerosol, radiative, and meteorological parameters from the global through urban scales (<5-km grid spacing) was developed. The model treats multiple one-way-nested layers and multiple air quality and meteorological domains in each layer between the global and the urban scales. This latter feature allows forecast of air pollution and weather at several urban or regional sites during the same simulation. Regardless of the number of domains used during a single continuous simulation, the central memory required never exceeds 1.5 times and 2.1 times that of the largest domain for gas and gas/aerosol simulations, respectively. A submodule was developed for all domains to treat ground temperatures, latent heat fluxes, and sensible heat fluxes over subgrid soil types (with and without vegetation), water, sea ice, and urban areas. Urban areas are divided into road surfaces, rooftops, vegetation, and bare soil. Snow is treated over all surface types. The global-through-urban model is applied in a companion paper to study elevated ozone, ozone in national parks, and weather during a field campaign in northern and central California.

Jacobson, Mark Z.

2001-03-01

85

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

86

Quaternary soil salinity events and Australian vegetation history  

NASA Astrophysics Data System (ADS)

A late Quaternary history of Australian soil salinization is produced by comparing Chenopodiaceae and Casuarina pollen curves. Although salinity development varied between sites, its occurrence was generally associated with arid phases and when high rainfall or high sea level caused regionally high groundwater tables. Soil salinization contributed to the shift from Casuarina- to Eucalyptus-dominance of interglacial sclerophyll vegetation. The deposition of saline sediments deflated from the Murray Basin seems more likely than Aboriginal burning to have caused the decline of Casuarina at Lake George. Soil salinization probably resulted in other vegetation changes and must be taken into account in environmental reconstructions. The renewed increase in soil salinity caused by European land-use practices and an associated decline in Casuarina are evident in the pollen records of many sites.

Crowley, G. M.

87

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

NASA Technical Reports Server (NTRS)

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

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

1980-01-01

88

Can SMAP radar observations be used to determine vegetation moisture status and root zone soil moisture?  

NASA Astrophysics Data System (ADS)

Recently, large differences in backscatter between the ascending (evening) and descending (morning) tracks of the wind scatterometer onboard the ERS-1 and ERS-2 satellites have been identified in times and locations of vegetation water stress. This suggests that vegetation might be considered as a source of information rather than a barrier to soil moisture retrieval. The goal here is to develop a quantitative relationship between the magnitude of the diurnal variation in backscatter and the vegetation water status. In turn, this will lead to information on the availability of water in the root zone. Diurnal variation in the backscatter response of vegetation was identified as early as the 1970s and was first observed from space in Seasat-1 scatterometer data in 1982. Subsequent field and laboratory experiments, primarily those of Ulaby and McDonald, have demonstrated that the variation is largely driven by changes in the dielectric properties of vegetation, which in turn depend on vegetation moisture content, sap chemistry and temperature. The magnitude of the diurnal variation in dielectric constant varies considerably within the vegetation itself. Furthermore, the contribution of individual vegetation components to backscatter depends on polarization and frequency. A combination of microwave theory and a numerical study will be used to argue that the morning and evening passes of the L-band radar on the SMAP satellite could be combined to yield information on vegetation water stress and root zone soil moisture. An innovative data assimilation strategy will be presented that could be used to merge the SMAP radar observations with a microwave backscatter model and a resistance-capacitance model to estimate vegetation moisture status and infer root zone soil moisture.

Steele-Dunne, S. C.; Friesen, J.; van de Giesen, N.

2010-12-01

89

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

NASA Technical Reports Server (NTRS)

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

Zobler, L.; Lewis, R.

1988-01-01

90

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

Microsoft Academic Search

The cold grasslands of the Qinghai-Tibetan Plateau form a globally significant biome, which represents 6% of the world's grasslands and 44% of China's grasslands. Yet little is known about carbon cycling in this biome. In this study, we calibrated and applied a process-based ecosystem model called Organizing Carbon and Hydrology in Dynamic Ecosystems (ORCHIDEE) to estimate the C fluxes and

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

2010-01-01

91

Vegetation clutter model  

NASA Technical Reports Server (NTRS)

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

Ulaby, F. T.

1980-01-01

92

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

SciTech Connect

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

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

2004-04-19

93

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

94

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

95

Soil and Vegetation Management: Keys to Water Conservation on Rangeland  

E-print Network

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

Schuster, Joseph L.

2001-01-11

96

Aminopyralid soil residues affect rotational vegetable crops in Florida  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

97

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

Microsoft Academic Search

Abstract The Hydro-Thermodynamic Soil-Vegetation Scheme ,(HTSVS) coupled in a ,two-way mode,with the PennState\\/National Center for Atmospheric,Research (NCAR) Mesoscale Meteorological Model generation 5 (MM5), has been subjected to evaluation for a 5 day typical snow-melt period using BALTic sea Experiment Meteorological Data Centre’s soil temperature, snow depth, and precipitation datasets. The HTSVS-MM5 evaluation investigates the coupled ,system’s sensitivity to two ,cloud

Balachandrudu Narapusetty

2005-01-01

98

Transfer of metals from soil to vegetables in an area near a smelter in Nanning, China  

Microsoft Academic Search

A field survey was conducted to investigate the metal contamination in soils and vegetables, and to evaluate the possible health risks to local population through foodchain transfer near a smelter in Nanning, southern China. Contamination levels in soils and vegetables with cadmium (Cd), lead (Pb), zinc (Zn) and copper (Cu) were measured, and transfer factors (TF) from soils to vegetable

Yu-Jing Cui; Yong-Guan Zhu; Ri-Hong Zhai; Deng-Yun Chen; Yi-Zhong Huang; Yi Qiu; Jian-Zhong Liang

2004-01-01

99

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

100

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

101

Analyzing Groundwater-Vegetation Interactions using a Dynamic Agroecosystem Model  

NASA Astrophysics Data System (ADS)

Groundwater is a crucial source of water for vegetation, especially in arid and semiarid environments in many regions around the world and its availability controls the distribution and the physiology of plant species. However, the impact of groundwater on vegetation is not completely understood mainly due to the limited ability of current models to simulate groundwater and vegetation interactions. Existing land surface models (LSM) simulate water and energy fluxes among soil-vegetation-atmosphere systems in a process-based way, but lack a detailed simulation of soil water movement in the unsaturated zone, particularly when groundwater is present. Furthermore, there are only a few available LSM and/or process based vegetation models that can simulate agroecosystems, which are as important to understand as natural ecosystems considering they occupy approximately 40% of the global land surface. On the other hand, current physically-based, variably-saturated soil water flux models are able to accurately simulate water movement in the unsaturated zone. However, they often lack a detailed plant physiology component making it difficult to understand plant responses to both variations in energy fluxes and upward capillary fluxes in shallow groundwater environments. To connect these two different model types, the objectives of this study are (1) to incorporate an advanced dynamic agroecosystem model (Agro-IBIS) and a variably saturated soil water flow model (Hydrus-1D) into a single framework that is capable of simulating groundwater and plant/crop system interactions in a fully, physically-based fashion, and (2) to apply this model using observed climate records to better understand the responses of managed and natural ecosystems to varied water table depths under inter-annual climate forcing conditions. The model results show that as the water table becomes shallower, (1) soil temperature decreases due to the moisture content driven effects on the thermal diffusivity of the soil, and (2) specific humidity at the leaf level increases due to increased rates of evaporation. These changes alter plant productivity as well as phenology depending on seasonal weather and depth to groundwater. We conclude that integrating the Hydrus-1D algorithms within Agro-IBIS improves our understanding of how groundwater and different plant species interact dynamically. Although current models are already capable of simulating groundwater - vegetation relations to some degree, more sophisticated and advanced models like we used here are necessary to describe the important aspects of this relationship such as effects of soil temperature, anoxia, and vegetation growth.

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

2012-12-01

102

Polarimetric radar discrete scatter model of vegetation  

Microsoft Academic Search

A microwave bistatic scatter model which predicts the scattering matrix (or Mueller matrix) is developed by using the discrete modelling technique for the vegetation. Vegetation is modelled as a random collection of scatterers. Leaves are modelled by a circular disc and branches are modelled by a circular cylinder. The modelling procedure assumes that the fractional volume of the plant material

S. S. Seker; S. Evren

1994-01-01

103

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

104

Ecohydrological feedbacks between soil salinity and vegetation dynamics as mediated by interactions with the water table  

NASA Astrophysics Data System (ADS)

In areas with relatively shallow water tables, changes in vegetation cover may affect local hydrologic conditions and favor the accumulation of salt within different parts of the soil profile. Because most plants are sensitive to saline soil water, a salt-vegetation feedback may exist, whereby vegetation cover maintains deeper water tables and slower rates of salt accumulation. As a result of this feedback, both a state with vegetation cover, deep water table, and low salinity, and a state with sparse or no vegetation, shallow water table and high salinity can be stable. Such dynamics may be present in the Murray Darling Basin, Australia, where widespread conversion from sclerophyll woodlands and forests to agricultural use has resulted in a decrease in the water table depth that has mobilized salts accumulated in the vadose zone and strongly increased the rate at which salts are transported within the system. To investigate these dynamics, we present a model to relate vegetation-soil salinity feedbacks - mediated by hydrologic conditions - to the emergence of multiple stable states in the underlying dynamics and apply this model to the Murray Darling Basin. Results for this case study show the presence of a strong feedback resulting in bistable dynamics for a wide range of environmental conditions (i.e., a range of precipitation regimes, soil textures, and salinities of irrigation and groundwater). This bistability increases the susceptibility of these systems to abrupt, highly irreversible shifts to stable bare soil, saline conditions and has important economic implications for dryland agricultural regimes worldwide as the presence of a shallow, saline water table is known to require costly remediation measures.

Runyan, C.; D'Odorico, P.

2010-12-01

105

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

106

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

PubMed

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

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

2007-05-25

107

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

108

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

109

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

110

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

111

Investigation of Soil Moisture - Vegetation Interactions in Oklahoma  

E-print Network

INVESTIGATION OF SOIL MOISTURE ? VEGETATION INTERACTIONS IN OKLAHOMA A Thesis by TRENTON W. FORD Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree... of MASTER OF SCIENCE Approved by: Chair of Committee, Steven M. Quiring Committee Members, Oliver W. Frauenfeld John Nielsen-Gammon Head of Department, Vatche P. Tchakerian May 2013 Major Subject: Geography Copyright 2013 Trenton W. Ford...

Ford, Trenton W.

2013-03-06

112

Pocket gophers ( Geomys bursarius ), vegetation, and soil nitrogen along a successional sere in east central Minnesota  

Microsoft Academic Search

Pocket gophers (Geomys bursarius: Geomyidae Rodentia) are shown to affect soil resources and thus, indirectly, vegetation. Gophers reduce average soil nitrogen near the surface and increase point-to-point heterogeneity of soil nitrogen by moving nitrogen-poor subsurface soil to the soil surface. Data from 22 old fields at Cedar Creek Natural History Area, Minnesota, USA show correlations of soil nitrogen, vegetation, and

R. S. Inouye; N. J. Huntly; D. Tilman; J. R. Tester

1987-01-01

113

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

114

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

115

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

116

Effects of temperature seasonality on tundra vegetation productivity using a daily vegetation dynamics model  

NASA Astrophysics Data System (ADS)

Changes in the seasonality of air temperature will elicit interacting effects on the dynamics of snow cover, nutrient availability, vegetation growth, and other ecosystem properties and processes in arctic tundra. Simulation models often do not have the fine temporal resolution necessary to develop theory and propose hypotheses for the effects of daily and weekly timescale changes on ecosystem dynamics. We therefore developed a daily version of an arctic tundra vegetation dynamics model (ArcVeg) to simulate how changes in the seasonality of air temperatures influences the dynamics of vegetation growth and carbon sequestration across regions of arctic tundra. High temporal-resolution air and soil temperature data collected from field sites across the five arctic tundra bioclimate subzones were used to develop a daily weather generator operable for sites throughout the arctic tundra. Empirical relationships between temperature and soil nitrogen were used to generate daily dynamics of soil nitrogen availability, which drive the daily uptake of nitrogen and growth among twelve tundra plant functional types. Seasonal dynamics of the remotely sensed normalized difference vegetation index (NDVI) and remotely sensed land surface temperature from the Advanced Very High Resolution Radiometer (AVHRR) GIMMS 3g dataset were used to investigate constraints on the start of the growing season, although there was no indication of any spatially consistent temperature or day-length controls on greening onset. Because of the exponential nature of the relationship between soil temperature and nitrogen mineralization, temperature changes during the peak of the growing season had greater effects on vegetation productivity than changes earlier in the growing season. However, early season changes in temperature had a greater effect on the relative productivities of different plant functional types, with potential influences on species composition.

Epstein, H. E.; Erler, A.; Frazier, J.; Bhatt, U. S.

2011-12-01

117

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

118

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

119

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

120

Stochastic Modeling of Soil Salinity  

NASA Astrophysics Data System (ADS)

Large areas of cultivated land worldwide are affected by soil salinity. Estimates report that 10% of arable land in over 100 countries, and nine million km2 are salt affected, especially in arid and semi-arid regions. High salinity causes both ion specific and osmotic stress effects, with important consequences for plant production and quality. Salt accumulation in the root zone may be due to natural factors (primary salinization) or due to irrigation (secondary salinization). Simple (e.g., vertically averaged over the soil depth) coupled soil moisture and salt balance equations have been used in the past. Despite their approximations, these models have the advantage of parsimony, thus allowing a direct analysis of the interplay of the main processes. They also provide the ideal starting point to include external, random hydro-climatic fluctuations in the analysis of long-term salinization trends. We propose a minimalist stochastic model of primary soil salinity, in which the rate of soil salinization is determined by the balance between dry and wet salt deposition and the intermittent leaching events caused by rainfall events. The long term probability density functions of salt mass and concentration are found by reducing the coupled soil moisture and salt mass balance equation to a stochastic differential equation driven by multiplicative Poisson noise. The novel analytical solutions provide insight on the interplay of the main soil, plant and climate parameters responsible for long-term soil salinization. In fact, soil salinity statistics are obtained as a function of climate, soil and vegetation parameters. These, in turn, can be combined with soil moisture statistics to obtain a full characterization of soil salt concentrations and the ensuing risk of primary salinization. In particular, the solutions show the existence of two quite distinct regimes, the first one where the mean salt mass remains nearly constant with increasing rainfall frequency, and the second one where mean salt content increases markedly with increasing rainfall frequency. As a result, relatively small reductions of rainfall in drier climates may entail dramatic shifts in long-term soil salinization trends, with significant consequences e.g. for climate change impacts on rain-fed agriculture. The analytical nature of the solution allows direct estimation of the impact of changes in the climatic drivers on soil salinity and makes it suitable for computations of salinity risk at the global scale as a function of simple parameters. Moreover it facilitates their coupling with other models of long-term soil-plant biogeochemistry.

Suweis, Samir; Rinaldo, Andrea; van der Zee, Sjoerd E. A. T. M.; Maritan, Amos; Porporato, Amilcare

2010-05-01

121

Soil Bacterial Community Shift Correlated with Change from Forest to Pasture Vegetation in a Tropical Soil  

PubMed Central

The change in vegetative cover of a Hawaiian soil from forest to pasture led to significant changes in the composition of the soil bacterial community. DNAs were extracted from both soil habitats and compared for the abundance of guanine-plus-cytosine (G+C) content, by analysis of abundance of phylotypes of small-subunit ribosomal DNA (SSU rDNA) amplified from fractions with 63 and 35% G+C contents, and by phylogenetic analysis of the dominant rDNA clones in the 63% G+C content fraction. All three methods showed differences between the forest and pasture habitats, providing evidence that vegetation had a strong influence on microbial community composition at three levels of taxon resolution. The forest soil DNA had a peak in G+C content of 61%, while the DNA of the pasture soil had a peak in G+C content of 67%. None of the dominant phylotypes found in the forest soil were detected in the pasture soil. For the 63% G+C fraction SSU rDNA sequence analysis of the three most dominant members revealed that their phyla changed from Fibrobacter and Syntrophomonas assemblages in the forest soil to Burkholderia and Rhizobium–Agrobacterium assemblages in the pasture soil. PMID:10427058

Nüsslein, Klaus; Tiedje, James M.

1999-01-01

122

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

123

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

124

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

125

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

NASA Astrophysics Data System (ADS)

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

Yu, Kailiang; D'Odorico, Paolo

2014-04-01

126

Development of a deterministic downscaling algorithm for remote sensing soil moisture footprint using soil and vegetation classifications  

NASA Astrophysics Data System (ADS)

Soil moisture (SM) at the local scale is required to account for small-scale spatial heterogeneity of land surface because many hydrological processes manifest at scales ranging from cm to km. Although remote sensing (RS) platforms provide large-scale soil moisture dynamics, scale discrepancy between observation scale (e.g., approximately several kilometers) and modeling scale (e.g., few hundred meters) leads to uncertainties in the performance of land surface hydrologic models. To overcome this drawback, we developed a new deterministic downscaling algorithm (DDA) for estimating fine-scale soil moisture with pixel-based RS soil moisture and evapotranspiration (ET) products using a genetic algorithm. This approach was evaluated under various synthetic and field experiments (Little Washita-LW 13 and 21, Oklahoma) conditions including homogeneous and heterogeneous land surface conditions composed of different soil textures and vegetations. Our algorithm is based on determining effective soil hydraulic properties for different subpixels within a RS pixel and estimating the long-term soil moisture dynamics of individual subpixels using the hydrological model with the extracted soil hydraulic parameters. The soil moisture dynamics of subpixels from synthetic experiments matched well with the observations under heterogeneous land surface condition, although uncertainties (Mean Bias Error, MBE: -0.073 to -0.049) exist. Field experiments have typically more variations due to weather conditions, measurement errors, unknown bottom boundary conditions, and scale discrepancy between remote sensing pixel and model grid resolution. However, the soil moisture estimates of individual subpixels (from the airborne Electronically Scanned Thinned Array Radiometer (ESTAR) footprints of 800 m × 800 m) downscaled by this approach matched well (R: 0.724 to -0.914, MBE: -0.203 to -0.169 for the LW 13; R: 0.343-0.865, MBE: -0.165 to -0.122 for the LW 21) with the in situ local scale soil moisture measurements during Southern Great Plains Experiment 1997 (SGP97). The good correspondence of observed soil water characteristics ?(h) functions (from the soil core samples) and genetic algorithm (GA) searched soil parameters at the LW 13 and 21 sites demonstrated the robustness of the algorithm. Although the algorithm is tested under limited conditions at field scale, this approach improves the availability of remotely sensed soil moisture product at finer resolution for various land surface and hydrological model applications.

Shin, Yongchul; Mohanty, Binayak P.

2013-10-01

127

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

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

128

MICROBIAL POPULATIONS ASSOCIATED WITH SOIL DEPTH, SOIL PHOSPHORUS, AND VEGETATION CHANGES DOWNWIND OF A CATTLE FEEDYARD  

Technology Transfer Automated Retrieval System (TEKTRAN)

In a previous study, the 30-year effect (1970 to 2000) of a 25,000-head beef cattle feedyard upon a downwind native shortgrass pasture was documented. Vegetation changes and a soil phosphorus (P) gradient with respect to distance from the feedyard were determined. The objective of this study was t...

129

Selecting iodine-enriched vegetables and the residual effect of iodate application to soil.  

PubMed

A greenhouse pot experiment was conducted to select vegetables for iodine uptake. The residual effect of iodate fertilization on the growth of and iodine uptake by spinach plants were also investigated. Six vegetables, including leafy vegetables (pakchoi [Brassica chinensis L.], spinach [Spinacia oleracea L.]), tuber vegetables (onion [Allium cepa L.]), shoot vegetables (water spinach [Ipomoea aquatica Forsk.], celery [Apium graveolens L.]), and root vegetables (carrot [Daucus carota var. sativa DC.]) were examined. Results showed that the concentrations of iodate in soil had significant effect on the biomass of edible parts of pakchoi and spinach (p<0.01), whereas the concentrations of iodate in soil had no significant effect on that of carrots, water spinach, celery, and onion. Iodine concentrations in edible parts of vegetables and the transfer factors (TFedible parts) of soil-to-edible parts of vegetables significantly increased with increasing iodine concentrations in soil (p<0.001), and iodine concentrations in edible parts and TFedible parts of spinach were much higher than those of other vegetables at any treatment. Both transfer coefficients for edible parts (TCedible parts) and for aerial parts (TCaerial parts) of vegetables changed differently with increasing iodine concentrations in the soil, and TCedible parts and TCaerial parts of spinach were higher than those of other vegetables. Therefore, spinach was considered as an efficient vegetable for iodine biofortification. Further experiment showed that there is considerable residual effect of soil fertilization with iodate. PMID:15564656

Dai, Jiu-Lan; Zhu, Yong-Guan; Zhang, Min; Huang, Yi-Zhong

2004-12-01

130

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

NASA Astrophysics Data System (ADS)

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

Moreno, Jose; Moran, Susan

2014-05-01

131

Soil and vegetation response to soil compaction and forest floor removal after aspen harvesting. Forest Service research paper  

Microsoft Academic Search

Reduced soil porosity and organic matter removal have been identified as common factors associated with loss of forest productivity (Powers et al. 1990). In both agriculture and forestry, management activities can modify soil porosity and organic matter with resultant impacts on vegetative growth. As part of a nationwide long-term soil productivity (LTSP) study soil porosity and organic matter are being

D. H. Alban; G. E. Host; J. D. Elioff; D. Shadis

1994-01-01

132

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

133

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

134

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

Microsoft Academic Search

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

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

2004-01-01

135

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

136

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

137

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

138

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

139

Modeling post-fire vegetation succession and its effect on permafrost vulnerability and carbon balance  

NASA Astrophysics Data System (ADS)

Wildfires are one of the main disturbances in high latitude ecosystems and have important consequences for the large stocks of carbon stored in permafrost soils. Fire affects carbon balance directly by burning vegetation and surface organic material and indirectly by influencing post-fire vegetation composition and soil thermal and hydrological regimes. Recent developments of ecosystem models allow a better representation of the effects of fire on organic soil dynamics and the soil environment, but there is a need to better integrate post-fire vegetation succession in these models. Post-fire vegetation regeneration is sensitive to fire consumption of soil organic layer horizons, where high severity burning promotes the establishment of deciduous broadleaf trees. In comparison to conifers, deciduous forests are less flammable, more productive, have higher nutrient turnover, and deeper permafrost. However, deciduous forests generally store less soil carbon than conifer forests. Therefore, the fire-induced shifts in vegetation composition have consequences for ecosystem carbon balance. In this study, we present the development of an ecosystem model that integrates post-fire succession with changes in the structure and function of organic soil horizons to better represent the relationship between fire severity and vegetation succession across the landscape. The model is then used to assess changes in the carbon balance at a 1km resolution, in response to changing fire regime across the landscape in Interior Alaska.

Genet, H.; McGuire, A. D.; Johnstone, J. F.; Breen, A. L.; Euskirchen, E. S.; Mack, M. C.; Melvin, A. M.; Rupp, T. S.; Schuur, E. A.; Yuan, F.

2013-12-01

140

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

141

EVALUATION OF SOIL WATER RETENTION MODELS BASED ON BASIC SOIL PHYSICAL PROPERTIES  

EPA Science Inventory

Algorithms to model soil water retention are needed to study the response of vegetation and hydrologic systems to climate change. he objective of this study was to evaluate some soil water retention models to identify minimum input data requirements. ix models that function with ...

142

Effect of soil surface sealing on the hydrological response and the vegetation cover of semi-arid areas (Invited)  

NASA Astrophysics Data System (ADS)

Bare soil surfaces in semi-arid areas are prone to sealing, which involves the formation of a compacted and thus less permeable layer at the vicinity of the soil surface. This particular interface of the soil-atmosphere system affects the two main hydrologic fluxes in such areas: infiltration and evaporation. It follows that local rainfall-runoff relations are directly impacted by the formation of this layer with logical consequences to water availability for vegetation development. The role of soil surface sealing in shaping such hydrological responses of a semi-arid hillslope in Southern Israel is described on a quantitative basis using a modeling approach that links the seal hydraulic properties to the physical characteristics of the hillslope. A two-dimensional surface runoff model is applied to represent the joint impact of the seal layer, the microtopography and the vegetation patches on spatial and temporal features of the rainfall-runoff relationship. The seal layer and the vegetation patches affect runoff generation, while microtopography affects mainly overland flow patterns. More water is supplied to the vegetation patches via runoff re-infiltration under soil surface sealing conditions, thus enabling establishment and development of vegetation cover.

Assouline, S.; CHEN, L.; Sela, S.; Svoray, T.; Katul, G. G.

2013-12-01

143

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

144

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

PubMed

Vegetation type and density exhibited a considerable patchy distribution at very local scales in the Yellow River Delta, due to the spatial variation of soil salinity and water scarcity. We proposed that soil respiration is affected by the spatial variations in vegetation type and soil chemical properties and tested this hypothesis in three different vegetation patches (Phragmites australis, Suaeda heteroptera and bare soil) in winter (from November 2010 to April 2011). At diurnal scale, soil respiration all displayed single-peak curves and asymmetric patterns in the three vegetation patches; At seasonal scale, soil respiration all declined steadily until February, and then increased to a peak in next April. But, the magnitude of soil respiration showed significant differences among the three sites. Mean soil respiration rates in winter were 0.60, 0.45 and 0.17 ?mol CO(2) m(-2) s(-1) for the Phragmites australis, Suaeda heteroptera and bare soil, respectively. The combined effect of soil temperature and soil moisture accounted for 58-68 % of the seasonal variation of winter soil respiration. The mean soil respiration revealed positive and linear correlations with total N, total N and SOC storages at 0-20 cm depth, and plant biomass among the three sites. We conclude that the patchy distribution of plant biomass and soil chemical properties (total C, total N and SOC) may affect decomposition rate of soil organic matter in winter, thereby leading to spatial variations in soil respiration. PMID:22576142

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

2012-07-01

145

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

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

146

Modelling global terrestrial vegetation-climate interaction  

PubMed Central

By coupling an atmospheric general circulation model asynchronously with an equilibrium vegetation model, manifold equilibrium solutions of the atmosphere-biosphere system have been explored. It is found that under present-day conditions of the Earth's orbital parameters and sea-surface temperatures, two stable equilibria of vegetation patterns are possible: one corresponding to present-day sparse vegetation in the Sahel, the second solution yielding savannah which extends far into the south-western part of the Sahara. A similar picture is obtained for conditions during the last glacial maximum (21 000 years before present (BP)). For the mid-Holocene (6000 years BP), however, the model finds only one solution: the green Sahara. We suggest that this intransitive behaviour of the atmosphere-biosphere is related to a westward shift of the Hadley-Walker circulation. A conceptual model of atmosphere-vegetation dynamics is used to interpret the bifurcation as well as its change in terms of stability theory.

Claussen, M.

1998-01-01

147

PIXE, 252Cf-PDMS and radiochemistry applied for soil and vegetable analysis  

NASA Astrophysics Data System (ADS)

The aim of this work is to identify the elements present in vegetables and soils using PIXE (particle induced X-rays emission) and 252Cf-PDMS ( 252Cf plasma desorption mass spectrometry) techniques in order to estimate the possible influence of soil and agricultural techniques in the metal absorption by the vegetables. In this work, metal concentrations were evaluated in soil and vegetable samples from several regions, where different agricultural techniques were employed. Si, Zr, Ce, Th, Sc and Pb identified in the soil samples were not biologically available. Ga, Ge, As and Br identified in the tubercles indicate that spray pesticide used on the vegetable leaves was absorbed by them. 232Th and 238U present in the soil were not absorbed by the vegetables. The airborne particles from anthropogenic sources (as CF n, VC n) were absorbed by the vegetables. Compounds from mineral sources present in soil as V +, VCO 3, HPO 4, Cr +, CrOH +, Mn +, FeH +, Fe(OH) n and in the bioorganic compounds as N +, Ca(CN)n+ and C nH + were identified in vegetables. The metal absorption by the vegetables is not dependent of the metal concentration in soil. Different tubercles cultivated in the same soil show similar metal absorption. The exogenous contributions such as the elements present in water irrigation, pesticides, fertilizers and airborne particles deposited on leaves can be absorbed by vegetables. The absorption by the roots depends on the chemical compound of the elements. The use of pesticide sprays and air pollution can cause more contamination in the vegetables than in soil. The use of this methodology allows the identification of possible sources of metals in soils and in vegetables and the metal speciation.

Dias da Cunha, K.; Cazicava, J.; Coelho, M. J.; Barros Leite, C. V.

2006-01-01

148

USING A GENERALIZED VEGETATION MODEL TO SIMULATE VEGETATION DYNAMICS IN NORTHEASTERN USA  

Microsoft Academic Search

Models based on generalized plant physiological theory represent a promising approach for describing vegetation responses to environmental drivers on large scales but must be tested for their ability to reproduce features of real vegetation. We tested the capability of a generalized vegetation model (LPJ-GUESS) to simulate vegetation structural and com- positional dynamics under various disturbance regimes at the transition between

Thomas Hickler; Benjamin Smith; Martin T. Sykes; Margaret B. Davis; Shinya Sugita; Karen Walker

2004-01-01

149

The effects of vegetation parameter aggregation on modeled evapotranspiration  

E-print Network

The effect of the scale of vegetation parameter aggregation on modeled evapotranspiration pattern and rate is explored. Vegetation biomass, height and fractional coverage per model grid cell were the vegetation parameters used in this research...

Hoffpauir, Richard James

2001-01-01

150

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

151

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

152

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

E-print Network

Radiometric Sensitivity to Soil Moisture Relative to Vegetation Canopy Anisotropy, Canopy Temperature, and Canopy Water Content at 1.4 GHz by Brian Kirk Hornbuckle A dissertation submitted in partial Sensitivity to Soil Moisture Relative to Vegetation Canopy Anisotropy, Canopy Temperature, and Canopy Water

Sarabandi, Kamal

153

GNSS reflections from bare and vegetated soils: Experimental validation of an end-to-end simulator  

Microsoft Academic Search

The detection of the land surface scattering of the signal radiated by navigation satellites may help estimating geophysical parameters such as soil moisture and vegetation biomass. In fact, the modulation of the GNSS signal and its frequency (L band) are particularly effective to sense vegetation attenuation and change of soil permittivity due to moisture. An experiment has been carried out

Nazzareno Pierdicca; Leila Guerriero; Roberto Giusto; Marco Brogioni; Alejandro Egido; Nicolas Floury

2011-01-01

154

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

E-print Network

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

Elmore, Andrew J.

155

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

E-print Network

Vegetation and climate controls on potential CO2, DOC and DON production in northern latitude soils in northern Alaska). Vegetation type strongly influenced carbon fluxes. The highest CO2 and DOC release. Of the fluxes, CO2 showed the greatest sensitivity to incubation temperatures and vegetation type, followed

Neff, Jason

156

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

157

[Optimization of application parameters of soil seed bank in vegetation recovery via response surface methodology].  

PubMed

The thickness of surface soil, the covering thickness and the number of adding arbor seeds are all important factors to be considered in the application of soil seed bank (SSB) for vegetation recovery. To determine the optimal conditions, the Box-Behnken central composite design with three parameters and three levels was conducted and Design-Expert was used for response surface optimization. Finally, the optimal model and optimal level of each parameter were selected. The quadratic model was more suitable for response surface optimization (P < 0.0001), indicating the model had good statistical significance which could express ideal relations between all the independent variable and dependent variable. For the optimum condition, the thickness of surface soil was 4.3 cm, the covering thickness was 2 cm, and the number of adding arbor seeds was 224 ind x m(-2), under which the number of germinated seedlings could be reached up to 6222 plants x m(-2). During the process of seed germination, significant interactions between the thickness of surface soil and the covering thickness, as well as the thickness of surface soil and the number of adding arbor seeds were found, but the relationship between the covering thickness and the number of adding arbor seeds was relatively unremarkable. Among all the parameters, the thickness of surface soil was the most important one, which had the steepest curve and the largest standardized coefficient. PMID:25509083

He, Meng-Xuan; Li, Hong-Yuan; Mo, Xun-Qiang; Meng, Wei-Qing; Yang, Jia-Nan

2014-08-01

158

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

159

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

160

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

161

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

162

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

163

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

E-print Network

EVALUATION OF VEGETATIVE COVER ON RECLAIMED LAND BY COLOR INFRARED VIDEOGRAPHY RELATIVE TO SOIL PROPERTIES A Thesis by ANNE AUGUSTA PFORDRESHER Submitted to the Graduate College of Texas ASM University in partial fulfillment... of the requirements for the degree of MASTER OF SCIENCE August 1988 Major Subject: Soil Science EVALUATION OF VEGETATIVE COVER ON RECLAIMED LAND BY COLOR INFRARED VIDEOGRAPHY RELATIVE TO SOIL PROPERTIES A Thesis by ANNE AUGUSTA PFORDRESHER Approved...

Pfordresher, Anne Augusta

1988-01-01

164

A new offline dust cycle model that includes dynamic vegetation  

NASA Astrophysics Data System (ADS)

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

Shannon, Sarah; Lunt, Daniel

2010-05-01

165

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

166

Comparison of deep soil moisture in two re-vegetation watersheds in semi-arid regions  

NASA Astrophysics Data System (ADS)

Soil moisture stored below rainfall infiltration depth is a reliable water resource for plant growth in semi-arid ecosystems. Along with the large-scale ecological restoration in Chinese Loess Plateau, identifying the ecohydrological response to human-introduced vegetation restoration has become an important issue in current research. In this study, soil moisture data in depth of 0-5 m was obtained by field observation and geostatistical method in two neighboring re-vegetation watersheds. Profile characteristics and spatial pattern of soil moisture was compared between different land use types, transects, and watersheds. The results showed that: (1) Introduced vegetation drastically decreased deep soil moisture when compared with farmland and native grassland. No significant differences in deep soil moisture were found between different introduced vegetation types. (2) An analysis of differences in soil moisture for different land use patterns indicated that land use had significant influence on deep soil moisture spatial variability. Land use structure determined the soil moisture condition and its spatial variation. (3) Vegetation restoration with introduced plants diminished the spatial heterogeneity of deep soil moisture on watershed scale. The improvement of land use management was suggested to improve the water management and maintain the sustainability of vegetation restoration.

Yang, Lei; Chen, Liding; Wei, Wei; Yu, Yang; Zhang, Handan

2014-05-01

167

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

168

The role of vegetation and soil properties on the spatio-temporal variability of the surface soil moisture in a maize-cropped field  

NASA Astrophysics Data System (ADS)

Soil moisture dynamics are affected by complex interactions among several factors. Understanding the relative importance of these factors is still an important challenge in the study of water fluxes and solute transport in unsaturated media. In this study, the spatio-temporal variability of surface soil moisture was investigated in a 10 ha flat cropped field located in northern Italy. Soil moisture was measured on a regular 50 × 50 m grid on seven dates during the growing season. For each measurement campaign, the spatial variability of the soil moisture was compared with the spatial variability of the soil texture and crop properties. In particular, to better understand the role of the vegetation, the spatio-temporal variability of two different parameters - leaf area index and crop height - was monitored on eight dates at different crop development stages. Statistical and geostatistical analysis was then applied to explore the interactions between these variables. In agreement with other studies, the results show that the soil moisture variability changes according to the average value within the field, with the standard deviation reaching a maximum value under intermediate mean soil moisture conditions and the coefficient of variation decreasing exponentially with increasing mean soil moisture. The controls of soil moisture variability change according to the average soil moisture within the field. Under wet conditions, the spatial distribution of the soil moisture reflects the variability of the soil texture. Under dry conditions, the spatial distribution of the soil moisture is affected mostly by the spatial variability of the vegetation. The interaction between these two factors is more important under intermediate soil moisture conditions. These results confirm the importance of considering the average soil moisture conditions within a field when investigating the controls affecting the spatial variability of soil moisture. This study highlights the importance of considering the spatio-temporal variability of the vegetation in investigating soil moisture dynamics, especially under intermediate and dry soil moisture conditions. The results of this study have important implications in different hydrological applications, such as for sampling design, ranking stability application, indirect measurements of soil properties and model parameterisation.

Baroni, G.; Ortuani, B.; Facchi, A.; Gandolfi, C.

2013-05-01

169

Insecticide residues in organic soils of six vegetable growing areas in Southwestern Ontario, 1976  

Microsoft Academic Search

Organic soils on 28 farms located in six widely separated vegetable growing areas in southwestern Ontario were sampled in 197 6 and analyzed for insecticide residues. Soil organic content generally was >65%. Organochlorine insecticide residues were detected in soil on all farms. Total DDT ranged from <0.1 to 29 ppm. Dieldrin, endo?sulfan, and endrin were present at levels up to

J. R. W. Miles; C. R. Harris

1978-01-01

170

WET SEWAGE SLUDGE APPLICATION EFFECT ON SOIL PROPERTIES AND ELEMENT CONTENT OF LEAF AND ROOT VEGETABLES  

Microsoft Academic Search

Pot experiments were conducted in a heated greenhouse to study the effects of increasing doses of sewage sludge application on vegetables grown for leaves (lettuce, endive, spinach) and roots (radish, carrots, beets), and on some soil properties. Results showed that sewage sludge application increased or decreased soil pH in cases of lower or higher values respectively, increased soil organic matter,

Efstathios Tamoutsidis; Ioannis Papadopoulos; Ioannis Tokatlidis; Stilianos Zotis; Theophilactos Mavropoulos

2002-01-01

171

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

172

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

173

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

174

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

PubMed Central

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

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

2014-01-01

175

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

176

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

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

177

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

178

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

179

Mercury in vegetation and soils at abandoned mercury mines in southwestern Alaska, USA  

USGS Publications Warehouse

We chemically analysed vegetation (willow and alder) and soil samples collected at three abandoned mercury (Hg) mines and at background sites in southwestern Alaska and compared Hg concentrations, speciation and distribution. Total Hg and methylmercury (MeHg) concentrations were higher in vegetation and soil samples from all the mine sites compared to samples from the background sites, but there was no correlation between total-Hg concentrations in vegetation and total-Hg concentrations in soil or between total-Hg and MeHg concentrations. However, the percent MeHg of the total Hg was higher in samples from the background sites compared to samples from the mine sites and is higher in vegetation samples than in corresponding soil samples. The percent MeHg is an order of magnitude higher in the willow samples than in corresponding alder or soil samples. The percent of divalent Hg [Hg(II)] is highest in soil samples from the retort and background areas. The higher percent MeHg in vegetation and soil in samples from background sites may be explained by the higher proportions of reactive Hg species, such as Hg(II), at these sites compared to the surface mined and tailings areas where most of the Hg is in the elemental and cinnabar (HgS) forms. Dissolved gaseous Hg species are more readily accumulated in vegetation and are more readily methylated than solid phases like HgS and liquid Hg.

Bailey, E.A.; Gray, J.E.; Theodorakos, P.M.

2002-01-01

180

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

181

Mechanical analysis of interaction between plant roots and rock and soil mass in slope vegetation  

Microsoft Academic Search

With the help of plant roots, slope vegetation makes the slope soil mass become a composite material of soil and roots, and\\u000a thus enhances shear strength of the slope soil mass and stability of the slope. However, the related studies at present are\\u000a still qualitative. In this paper, quantitative analysis of the interaction between roots and soil mass are made.

Zhi-xin Yan; Yun Song; Ping Jiang; Hou-yu Wang

2010-01-01

182

Phytoavailability of thallium - A model soil experiment  

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

183

Effects of soil moisture variations on deposition velocities above vegetation.  

SciTech Connect

The parameterized subgrid-scale surface flux (PASS) model provides a simplified means of using remote sensing data from satellites and limited surface meteorological information to estimate the influence of soil moisture on bulk canopy stomatal resistances to the uptake of gases over extended areas. PASS-generated estimates of bulk canopy stomatal resistance were used in a dry deposition module to compute gas deposition velocities with a horizontal resolution of 200 m for approximately 5000 km{sup 2} of agricultural crops and rangeland. Results were compared with measurements of O{sub 3} flux and concentrations made during April and May 1997 at two surface stations and from an aircraft. The trend in simulated O{sub 3} deposition velocity during soil moisture drydown over a period of a few days matched the trend observed at the two surface stations. For areas under the aircraft flight paths, the variability in simulated O{sub 3} deposition velocity was substantially smaller than the observed variability, while the averages over tens of kilometers were usually in agreement within 0.1 cm s{sup -1}. Model results indicated that soil moisture can have a major role in deposition of O{sub 3} and other substances strongly affected by canopy stomatal resistance.

Wesely, M. L.; Song, J.; McMillen, R. T.; Meyers, T. P.; Environmental Research; Northern Illinois Univ.; National Oceanic and Atmospheric Administration

2001-01-01

184

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.

185

Soil erosion and environmental impact of vegetable production in the Cameron Highlands, Malaysia  

Microsoft Academic Search

Vegetable production in the Cameron Highlands of Malaysia has expanded over the past 25 years and has been implicated in the increase in sedimentation in reservoirs in the region. The present study was executed to evaluate current methods, patterns and profitability of vegetable production; study the causes, environmental impact and externality cost of soil erosion; assess the effectiveness and adoption

David J. Midmore; Hans G. P. Jansen; Robert G. Dumsday

1996-01-01

186

An Idealized Model of Plant and Soil Dynamics  

NASA Astrophysics Data System (ADS)

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

Burg, David; Malkinson, Dan; Wittenberg, Lea

2014-05-01

187

Field-derived spectra of salinized soils and vegetation as indicators of irrigation-induced soil salinization  

Microsoft Academic Search

Salinization is a major cause of soil degradation in the Murray–Darling Basin of Australia. The objective of this research is to evaluate the utility of field-derived spectra of saline soils and related vegetation for characterizing and mapping the spatial distribution of irrigation-induced soil salinization. A FieldSpec FR hand-held spectrometer was used to measure the spectra of a range of salinized

R. l. Dehaan; G. r. Taylor

2002-01-01

188

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

189

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

SciTech Connect

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

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

2004-01-09

190

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

191

Spatio-temporal variability of soil moisture and its effect on vegetation in a desertified aeolian riparian ecotone on the Tibetan Plateau, China  

NASA Astrophysics Data System (ADS)

SummarySoil moisture content is one of the limiting factors for natural vegetation succession in alpine river valleys on the Tibetan Plateau. However, its spatio-temporal variability and effect on artificial vegetation restoration has rarely been reported. In this paper, we conducted a case study to examine the spatio-temporal variability and vertical characteristics of soil moisture by setting up a 100 × 120 m experimental plot on aeolian sandy land in a riparian ecotone and analyzing the result data using a geo-statistical approach. The soil moisture contents at different depths all showed strong temporal variability, with the mean soil moisture ranging from 4% to 6% in spring, from 6% to 14% in summer and from 9% to 12% in autumn. The Gaussian semi-variogram model was the best fitted theoretical model for the spatial structure of soil moisture contents in different seasons, and soil moisture at the field scale showed strong spatial dependence. The spatial patterns of soil moisture all demonstrated strong similarity between depths with the strongest between 0-20 cm and 20-40 cm depths in autumn. The soil moisture content over the upper 60 cm was the key factor that restricted the seed germination and seedling growth, and it affected vegetation coverage and density. The precipitation, variations of river water level, elevation as well as landform types were the main factors determining the variations of soil moisture content in different seasons. The results have important implications for the ongoing vegetation restoration in the study area.

Li, Haidong; Shen, Weishou; Zou, Changxin; Jiang, Jiang; Fu, Lina; She, Guanghui

2013-02-01

192

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

193

Modeling hydrology and sediment transport in vegetative filter strips  

SciTech Connect

Sediment and sediment bounded pollutants carried by runoff from non-point sources is a major pollutant of water bodies. Vegetative filter strips (VFS) are bands of planted or indigenous vegetation used to control runoff and sediment outflow from disturbed areas. This work presents and validates a research model to study the hydrology and sediment movement in VFS. This was accomplished in four steps. The numerical solution of the overland flow kinematic wave equations is subject to numerical problems when a rapid change in parameters is encountered (kinematic shock). An improved finite element method, i.e. a Petrov-Galerkin (PG) formulation, is presented. The formulation depends on four parameters. The PG method decreased the mean sum of square error by about 65%. The finite element overland flow solution is modified and linked to the Green-Ampt infiltration equation to form a VFS-specific hydrology model. An analysis of the effect of different filter properties (soil type, slope, surface roughness, buffer length) on the major hydrological out-puts (runoff volume, velocity and peak flow rate) is made. Optimal filter performance (i.e. reduction in runoff volume, velocity and peak flow rate) is found for soils with high infiltration capacity, dense grass cover and small slopes. A sediment transport/filtration submodel (based on the University of Kentucky model) is added to the hydrology submodel. The interaction between submodels and a natural event application case to illustrate the capability of the model and its various outputs is presented in detail. An analysis of sensitivity and a field validation are performed. The most sensitive parameters are soil initial water content, vertical saturated hydraulic conductivity, particle class and grass spacing. The model predictions were compared with a set of natural events from an experimental site in the North Carolina Piedmont. In general the model performs well.

Munoz-Carpena, R.

1993-12-31

194

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

195

[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

196

Multi-discipline resource inventory of soils, vegetation and geology  

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

197

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

198

Relationship between vegetation and soil seed banks in an arctic coastal marsh  

Microsoft Academic Search

Summary 1 The effects of habitat degradation on the soil seed bank at La Pérouse Bay, Manitoba are described. Foraging by lesser snow geese leads to loss of vegetation, coupled with changes in soil abiotic conditions and an increase in salinity. 2 The density of seeds and the relative abundance in the seed bank of species charac- teristic of undisturbed

E. R. Chang; R. L. Jefferies; T. J. Carleton

2001-01-01

199

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

Microsoft Academic Search

This paper reports changes in vegetation distribution and species cover in relation to soil factors and hydrology in a semiarid Mediterranean salt marsh adjacent to the Mar Menor saline lagoon. Species cover, soil salinity, and the groundwater level were monitored between 1991 and 1993 and between 2002 and 2004, and total organic carbon, total nitrogen, total phosphorus, nitrates, ammonium and

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

2007-01-01

200

[Soil water environment of artificial vegetation in Jinshajiang dry-hot volley].  

PubMed

Jinshajiang dry-hot volley has the characteristics of extremely hot and dry climate due to its specific local climate, where universally exists moisture deficit and the problem of soil water environment of artificial vegetation becomes more serious than other arid and semi-arid areas. The environmental determination in the typical sector of dry-hot volley Yuanmou showed that the existed arboreous forests evidently showed the characteristics of soil drying. Soil was short of moisture for a long term. In November after the rain season was over, soil water content in two-meter-deep soil layer was only 15% (equal to 35% of field capacity). Later on, soil water content continued decreasing and reached the lowest point in May (9%), which was near to wilting moisture of trees (the wilting moisture of surface eroded dry red soil of Yuanmou was 9.0%). As a result, trees grew slowly. As for Radonaea wiscosa shrubbery, its soil water content at the same layer was relatively 42.68% higher than that of arboreous trees. The soil moisture of natural grass slope was evidently better than that of arboreous trees and shrubbery, and was 34.36% and 22.22% higher, respectively. This kind of soil drying problem didn't come into notice in the vegetation restoration of Jinshajiang dry-hot volley, which would greatly restrict the sustainable development of artificial vegetation. PMID:15320399

Wang, Keqin; Shen, Youxin; Chen, Qibo; Wang, Zhenhong

2004-05-01

201

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

NASA Technical Reports Server (NTRS)

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

Wang, J. R.

1985-01-01

202

The influence of vegetation cover on soil organic matter preservation in Antarctica during the Mesozoic  

NASA Astrophysics Data System (ADS)

A possible biological component of the explanation for the lack of substantial coal formation on Antarctica between the Late Jurassic and Late Cretaceous is hypothesised. Forcing a process-based terrestrial biogeochemistry model with climate model simulations for three successive intervals of the Mesozoic [Late Jurassic (150 Ma), mid-Cretaceous (100 Ma) and Late Cretaceous (65 Ma)], predicts the establishment of productive terrestrial ecosystems with substantial soil carbon pools throughout the land surface of Antarctica between 150 and 65 million years ago. Sensitivity analyses indicate the annual land surface hydrological budget of Antarctica 150-65 Ma was largely balanced due to the effects of canopy transpiration on soil moisture. Post-depositional erosion and tectonic setting must have played an important role in determining coal preservation on the continent. However, the model results indicate that an active vegetated land surface precluded the preservation of the substantial soil organic carbon inputs by minimising the potential for anaerobic preservation (i.e. water logging).

Beerling, D. J.

2000-01-01

203

Calibrating a Soil-Vegetation-Atmosphere system with a genetical algorithm  

NASA Astrophysics Data System (ADS)

Accuracy of model prediction is well known for being very sensitive to the quality of the calibration of the model. It is also known that quantifying soil hydraulic parameters in a Soil-Vegetation-Atmosphere (SVA) system is a highly non-linear parameter estimation problem, and that 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. The SVA system in this study concerns a pine stand on a heterogeneous sandy soil (podzol) in the north of Belgium (Campine region). Throughfall and other meteorological data and water contents at different soil depths have been recorded during one year at a daily time step. The water table level, which is varying between 95 and 170 cm, has been recorded with a frequency of 0.5 hours. Based on the profile description, four soil layers have been distinguished in the podzol and used for the numerical simulation with the hydrus1D model (Simunek and al., 2005). For the inversion procedure the MYGA program (Yedder, 2002), which is an elitism GA, was used. Optimization was based on the water content measurements realized at the depths of 10, 20, 40, 50, 60, 70, 90, 110, and 120 cm to estimate parameters describing the unsaturated hydraulic soil properties of the different soil layers. Comparison between the modeled and measured water contents shows a good similarity during the simulated year. Impacts of short and intensive events (rainfall) on the water content of the soil are also well reproduced. Errors on predictions are on average equal to 5%, which is considered as a good result. A. Ben Haj Yedder. Numerical optimization and optimal control : (molecular chemistry applications). PhD thesis, Ecole Nationale des Ponts et Chaussées, 2002. Šim?nek, J., M. Th. van Genuchten, and M. Šejna, The HYDRUS-1D software package for simulating the one-dimensional movement of water, heat, and multiple solutes in variably saturated media. Version 3.0, HYDRUS Software Series 1, Department of Environmental Sciences, University of California Riverside, Riverside, CA, 270 pp., 2005.

Schneider, S.; Jacques, D.; Mallants, D.

2009-04-01

204

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

205

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

206

Spectral mixture analysis to assess post-fire vegetation regeneration using Landsat Thematic Mapper imagery: Accounting for soil brightness variation  

NASA Astrophysics Data System (ADS)

Post-fire vegetation cover is a crucial parameter in rangeland management. This study aims to assess the post-fire vegetation recovery 3 years after the large 2007 Peloponnese (Greece) wildfires. Post-fire recovery landscapes typically are mixed vegetation-substrate environments which makes spectral mixture analysis (SMA) a very effective tool to derive fractional vegetation cover maps. Using a combination of field and simulation techniques this study aimed to account for the impact of background brightness variability on SMA model performance. The field data consisted out of a spectral library of in situ measured reflectance signals of vegetation and substrate and 78 line transect plots. In addition, a Landsat Thematic Mapper (TM) scene was employed in the study. A simple SMA, in which each constituting terrain feature is represented by its mean spectral signature, a multiple endmember SMA (MESMA) and a segmented SMA, which accounts for soil brightness variations by forcing the substrate endmember choice based on ancillary data (lithological map), were applied. In the study area two main spectrally different lithological units were present: relatively bright limestone and relatively dark flysch (sand-siltstone). Although the simple SMA model resulted in reasonable regression fits for the flysch and limestones subsets separately (coefficient of determination R2 of respectively 0.67 and 0.72 between field and TM data), the performance of the regression model on the pooled dataset was considerably weaker ( R2 = 0.65). Moreover, the regression lines significantly diverged among the different subsets leading to systematic over-or underestimations of the vegetative fraction depending on the substrate type. MESMA did not solve the endmember variability issue. The MESMA model did not manage to select the proper substrate spectrum on a reliable basis due to the lack of shape differences between the flysch and limestone spectra,. The segmented SMA model which accounts for soil brightness variations minimized the variability problems. Compared to the simple SMA and MESMA models, the segmented SMA resulted in a higher overall correlation ( R2 = 0.70), its regression slope and intercept were more similar among the different substrate types and its resulting regression lines more closely resembled the expected one-one line. This paper demonstrates the improvement of a segmented approach in accounting for soil brightness variations in estimating vegetative cover using SMA. However, further research is required to evaluate the model's performance for other soil types, with other image data and at different post-fire timings.

Veraverbeke, S.; Somers, B.; Gitas, I.; Katagis, T.; Polychronaki, A.; Goossens, R.

2012-02-01

207

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

208

Effect of Vegetation Patterns on SAR derived Surface Soil Moisture Distribution  

NASA Astrophysics Data System (ADS)

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

Koyama, C. N.; Schneider, K.

2012-12-01

209

Soil and vegetation response to soil compaction and forest floor removal after aspen harvesting. Forest Service research paper  

SciTech Connect

Reduced soil porosity and organic matter removal have been identified as common factors associated with loss of forest productivity (Powers et al. 1990). In both agriculture and forestry, management activities can modify soil porosity and organic matter with resultant impacts on vegetative growth. As part of a nationwide long-term soil productivity (LTSP) study soil porosity and organic matter are being experimentally manipulated on large plots to determine the impacts of such manipulations on growth and species diversity for a wide range of forest types.

Alban, D.H.; Host, G.E.; Elioff, J.D.; Shadis, D.

1994-01-01

210

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

211

soil to compaction, organic matter removal, and vegetation control1  

Microsoft Academic Search

We tested three disturbance hypotheses in young conifer plantations: H,: soil compaction and removal of surface organic matter produces sustained changes in microbial community size, activity, and structure in mineral soil; H2: microbial community characteristics in mineral soil are linked to the recovery of plant diversity; and H3: community responses are strongly modified by regional climate. Microbial biomass, respiration, carbon

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

212

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

213

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

214

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

215

Modeling gap probability in discontinuous vegetation canopies  

NASA Technical Reports Server (NTRS)

In the present model for the gap probability of a discontinuous vegetation canopy, the assumption of a negative exponential attenuation within individual plant canopies will yield a problem involving the distribution distances within canopies through which a ray will pass. If, however, the canopies intersect and/or overlap, so that foliage density remains constant within the overlap area, the problem can be approached with two types of approximations. Attention is presently given to the case of a comparison of modeled gap probabilities with those observed for a stand of Maryland pine, which shows good agreement for zenith angles of illumination up to about 45 deg.

Li, Xiaowen; Strahler, Alan H.

1987-01-01

216

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

217

[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

218

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

219

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

220

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

PubMed

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

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

2013-09-01

221

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

222

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

223

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

224

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

225

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

226

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

Microsoft Academic Search

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

Kirk J. Havens

1997-01-01

227

Grid Scale Effects on Watershed Soil Erosion Models Rosalia Rojas1  

E-print Network

Grid Scale Effects on Watershed Soil Erosion Models Rosalia Rojas1 ; Mark Velleux2 ; Pierre Y Database subject headings: Soil erosion; Hydrologic models; Sediment; Watersheds; Mississippi. Introduction erosion losses are influenced by spatial variations in to- pography, vegetation, soil types, and land use

Julien, Pierre Y.

228

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

229

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

230

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

231

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

232

[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

233

Long-term investigations on the water budget quantities predicted by the hydro-thermodynamic soil vegetation scheme (HTSVS) – Part I: Description of the model and impact of long-wave radiation, roots, snow, and soil frost  

Microsoft Academic Search

Summary ¶An earlier version of HTSVS was further developed to numerically investigate the long-term evolution of water budget elements (water supply to the atmosphere, ground water recharge, change in storage) in climate studies. In doing so, parameterizations of root effects, infiltration, soil frost, and snow insulation were included into HTSVS to predict these water budget elements for a period of

N. Mölders; U. Haferkorn; J. Döring; G. Kramm

2003-01-01

234

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...

235

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

236

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

237

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

NASA Astrophysics Data System (ADS)

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

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

2011-05-01

238

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

239

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

240

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

241

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

NASA Astrophysics Data System (ADS)

The relationship between vegetation and soil water was studied on the Syncrude South West Sand Storage facility in the Athabasca Oil Sands region of Alberta, Canada. Soil water and relevant soil chemical and physical properties were measured at the soil surface, as well as above and below the reclamation soil and tailings sand interface, in areas of low and high vegetation cover. The interface between the reclamation soil and the tailings sand acted as a capillary barrier. Water content was highest under low vegetation cover but soil water conditions above field capacity were rare and unlikely to have impacted vegetation. Periods of water stress occurred, where volumetric water content was below wilting point; these periods were of short duration and generally typical of ecosystems in the study area. Differences in surface soil water between the two vegetation covers were attributed to evapotranspiration and/or canopy interception. Differences above and below the interface were attributed to variation in canopy cover at the surface and resulting quantities of water available for percolation through the soil profiles. At the interface of the reclamation soil and tailings sand, water movement was restricted. High and low canopy covers responded differently to precipitation events; low vegetation cover areas had greater fluctuations in volumetric water content at all depths. The occurrence of a capillary barrier effect will need to be accounted for in developing reclamation soil profiles.

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

242

The association of selected soil properties with the distribution of native vegetation  

E-print Network

of NASTER OF SCIENCE August 1991 Najor Subject: Wildlife and Fisheries Sciences THE ASSOCIATION OF SELECTED SOIL PROPERTIES WITH THE DISTRIBUTION OF NATIVE VEGETATION A Thesis by JAMES HUGH YANTIS Approved as to style and content by: Nova J. Shelvy... (Chair of Committee) H E. William E. Grant (Merrber) Michael T Longnecker (Menber) Charles T. Hallmark (Member) id J. Schmidly ( ead of Department) August 1991 111 ABSTRACT The Association of Selected Soil Properties with the Distribution...

Yantis, James H

1991-01-01

243

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

244

Dryland ecosystems: the coupled stochastic dynamics of soil water and vegetation and the role of rainfall seasonality.  

PubMed

In drylands the soil water availability is a key factor ruling the architecture of the ecosystem. The soil water reflects the exchanges of water among soil, vegetation, and atmosphere. Here, a dryland ecosystem is investigated through the analysis of the local interactions between soil water and vegetation forced by rainfall having seasonal and stochastic occurrence. The evolution of dryland ecosystems is represented by a system of two differential equations, having two steady states, one vegetated and the other unvegetated. The rainfall forcing is described by a diffusion process with monthly parameters. In each of the two possible steady states, the probability density functions of soil water and vegetation are derived analytically in terms of the rainfall distribution. The results show how the seasonality of rainfall influences the oscillation of the ecosystem between its vegetated steady state during the wet season and its unvegetated steady state during the dry season. PMID:18643103

Vezzoli, R; De Michele, C; Pavlopoulos, H; Scholes, R J

2008-05-01

245

[Spatial variation of heavy metals contamination in the soil and vegetables of Huludao City].  

PubMed

Hg, Pb, Cd, Zn, and Cu concentrations in the soil, vegetables and crop of Huludao city were investigated. The Hg, Pb, Cd, Zn, and Cu concentrations in soils of the smelting areas are 1.422, 443.1, 60.94, 4084, and 247.8 mg x kg(-1), thus 6.092, 3195, 341.7, 35 157, and 1 557 mg x kg(-1) for the maximal concentrations, respectively. Spatial distribution maps of heavy metals concentrations in top soils in Huludao City were separately laid out by using Kriging. Heavy metals spatial distribution patterns in soils show that Ph, Cd, Zn, Cu emissions from Huludao Zinc Plant are the main pollution sources of heavy metals to the top soils in Huludao City, but Hg emission from Huludao Zinc Plant and chlor-alkali industry is the main pollution source of mercury to the top soils. Heavy metals concentrations in top soils decrease exponentially with distance from the zinc smelting area. Except Hg, the exponential equation could be better to fit the variety forother heavy metals. Heavy metals in vegetable and crop cultivated around Huludao Zinc Plant are higher than from markets, suggests that heavy metals affect the local soil and crops seriously. PMID:19775010

Zheng, Na; Wang, Qi-Chao; Liu, Jing-Shuang; Wang, Yang; Zhang, Zhong-Sheng

2009-07-15

246

Soil property variations in relation to topographic aspect and vegetation community in the south-eastern highlands of Ethiopia  

Microsoft Academic Search

Study of soil property variations resulting from topographic aspect and vegetation changes will have implication on the proper management of marginal and environmentally sensitive areas. This study addressed the effects of topographic aspect and vegetation community types on soil physical and chemical properties in the Bale Mountains, south-eastern highlands of Ethiopia. At each stratified vegetation community; Schefflera–Hagenia, Hypericum–Erica–Schefflera, and Erica

Fantaw Yimer; Stig Ledin; Abdu Abdelkadir

2006-01-01

247

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

PubMed

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

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

2014-12-01

248

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

249

Inter-sensor relationship of two-band spectral vegetation index based on soil isoline equation: derivation and numerical validation  

NASA Astrophysics Data System (ADS)

Differences in spectral response function among sensors have known to be a source of bias error in derived data products such as spectral vegetation indices (VIs). Numerous studies have been conducted to identify such bias errors by comparing VI data acquired simultaneously by two different sensors. Those attempts clearly indicted two facts: 1) When one tries to model a relationship of two VIs from different sensors by a polynomial function, the coefficients of polynomial depends heavily on region to be studied: 2) Although increase of the degree of polynomial improves the translation accuracies, this improvement is very limited. Those facts imply that a better functional form than a simple polynomial may exist to model the VI relationships, and also that the coefficients of such a relationship can be written as a function of variables other than vegetation biophysical parameters. This study tries to address those issues by deriving an inter-sensor VI relationship analytically. The derivation has been performed based on a relationship of two reflectances at different wavelengths (bands), called soil isoline equation. The derived VI relationship becomes a form of rational function with the coefficients that depend purely on the soil reflectance spectra. The derived relationship has been demonstrated numerically by a radiative transfer model of canopy, PROSAIL. It is concluded that a rational function is a good candidate to model inter-sensor VI relationship. This study also shows the mechanism of how the coefficients of such a relationship could vary with the soil reflectance underneath the canopy.

Taniguchi, Kenta; Obata, Kenta; Matsuoka, Masayuki; Yoshioka, Hiroki

2013-09-01

250

Contents and sources of polycyclic aromatic hydrocarbons and organochlorine pesticides in vegetable soils of Guangzhou, China  

Microsoft Academic Search

We investigated contents, distribution and possible sources of PAHs and organochlorine pesticides (Ops) in 43 surface and subsurface soils around the urban Guangzhou where variable kinds of vegetables are grown. The results indicate that the contents of PAHs (16 US EPA priority PAHs) range from 42 to 3077?g\\/kg and the pollution extent is classified as a moderate level in comparison

Laiguo Chen; Yong Ran; Baoshan Xing; Bixian Mai; Jianghua He; Xiuguo Wei; Jiamo Fu; Guoying Sheng

2005-01-01

251

Temperature sensitivity of greenhouse gas production in wetland soils of different vegetation  

E-print Network

decomposition regulates rates of carbon loss (CO2 and CH4) in wetlands and has implications for carbon on vegetation (source of carbon substrate to soil). Under anaerobic incubations, the proportion of gaseous C (CO production as compared with anaerobic CO2 (1.3­2.5) or aerobic CO2 (1.4­2.1) production. The increasing

Florida, University of

252

[Cesium-137 in soil and vegetation from Spitsbergen and continental Norway (Suldal) 1981].  

PubMed

Concentration of Cesium-137 in samples of soil and vegetation from Spitsbergen (Svalbard) and Suldal (Western-Norway) has been measured. The results indicate that different diets can account for the large difference (1:100), in Cesium-137 concentration in reindeer meat from Spitsbergen and mainland Norway. PMID:7187488

Kjos-Hanssen, B; Tørresdal, O

1982-03-01

253

EFFECTS OF A RESTORED ELK POPULATION ON SOILS, VEGETATION, AND WATER QUALITY IN EASTERN KENTUCKY  

Microsoft Academic Search

A restored elk (Cervus elaphus) population in eastern Kentucky may be affecting ecosystem processes in a landscape composed of reclaimed grassland expanses and isolated forest remnants. Elk routinely select forested ridge-tops as resting and ruminating sites. These locations are characterized by sparse or absent leaf litter, trampled and diminished vegetation, large deposits of dung, and urine-saturated soils. In fall 2003,

Julia M. Ter Beest

2005-01-01

254

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...

255

Changes in faunal and vegetation communities along a soil calcium gradient in northern hardwood  

E-print Network

Changes in faunal and vegetation communities along a soil calcium gradient in northern hardwood, but these impacts remain largely unknown. Because snails, salamanders, and plants play essential roles in the Ca cycle of northern hardwood forests, we hypothesized that their community diversity, abundance

Vermont, University of

256

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

257

A three-tiered approach for coupled vegetation and soil sampling to develop ecological descriptions  

Technology Transfer Automated Retrieval System (TEKTRAN)

Ecological site descriptions (ESDs), alongside similar land classification systems, are used to describe the breadth of plant community types, community changes, and soil surface conditions that can occur within a particular land area. Vegetation dynamic processes and management may change the ident...

258

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...

259

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, rivers and aquifers (Meidinger and Pojar, 1991). High nitrogen concentration can cause lake quality (Vitousek and Howarth, 1991; Carpenter et al., 1998). As nitrogen (N) is a major determinant

Mazumder, Asit

260

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...

261

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

PubMed Central

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

Liu, Zhanfeng; Zhou, Lixia; Fu, Shenglei

2014-01-01

262

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

263

[Effects of land use and vegetation restoration on soil quality in a small catchment of the Loess Plateau].  

PubMed

Soil quality improvement plays an important role in sustaining global biosphere. This paper studied the changes of soil quality after 25 years' land use and vegetation restoration at the Anjiapo catchment of western Loess Plateau. The analyses of soil characteristics of wasteland, almond land, farmland, pineland, shrub land and fallow land showed that different land use and vegetation restoration had different effects on soil integrated fertility index. Soil organic matter content was increased due to planting shrubs and forests. Both vegetation restoration and fallow could improve soil quality. Cultivation practice could decrease soil nutrient levels, and cropland soil was degraded. Shrub soil formed "fertile island" in the semi-arid region. Fallow could improve soil fertility to some extent. Human activities and vegetation restoration could affect soil nutrient contents after land use pattern was changed. With the launch out into the "Grand development of Western China", "Grain for Green Project" and ecological restoration, both shrub planting and fallow (natural restoration) should be the optional choices to restore soil fertility, as they could decrease soil erosion and improve soil condition at catchment scale, especially in the hilly and gully loess area. Integrative control of small catchment may be the best way for the sustainable development of the semi-arid hilly area of Loess Plateau. PMID:15825444

Gong, Jie; Chen, Liding; Fu, Bojie; Li, Yanmei; Huang, Zhilin; Huang, Yilong; Peng, Hongjia

2004-12-01

264

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

PubMed

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

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

2008-08-01

265

Relative Skills of Soil Moisutre and Vegetation Optical Depth Retrievals for Agricultural Drought Monitoring  

NASA Astrophysics Data System (ADS)

Soil moisture condition is an important indicator for agricultural drought monitoring. Through the Land Parameter Retrieval Model (LPRM), vegetation optical depth (VOD) as well as surface soil moisture (SM) can be retrieved simultaneously from brightness temperature observations from the Advanced Microwave Scanning Radiometer (AMSR-E). This study aims to investigate added skills of VOD in addition to SM for agricultural drought monitoring using monthly LPRM-SM and VOD products from 2002 to 2011. First, the lagged rank cross-correlation between Normalized Difference Vegetation Index (NDVI) and the SM/VOD retrievals is used to evaluate the skills of the SM and VOD for drought monitoring. Interestingly, the highest rank cross-correlation between NDVI and VOD is found with lag of (+1) month (temporally lagged behind ranks of NDVI by 1 month), while the highest rank cross-correlation coefficient of SM is found with lag (-1) month (temporally precedes the ranks of NDVI by 1 month). Lagged responses of plants to the available water capacity in the root zone may explain this lagged peak of correlation of VOD. In order to understand this finding more systematically, additional analysis on the microwave polarization difference index and vertical/horizontal brightness temperature are conducted. Next, different types of observations (SM, VOD and NDVI) and hydrologic model results (Palmer model) are merged to improve predictive power. We adopt two different merging approaches (simple weighting method and auto-regressive model) to quantify the added skills of those different drought-related indices. The results show that adding more information rather than using solely SM observation increases lag (-1) month cross-correlation coefficient with NDVI. This result indicates that different observations/models have independent information to some degree. Therefore further analysis on error-correlations between the observations/model results is also conducted. This study suggests necessity of incorporating additional available information (e.g. VOD) for advanced agricultural drought monitoring techniques. In addition, in-depth analysis on the error correlations between different drought-related observations is expected to provide useful insights for data assimilation studies.

Han, E.; Crow, W. T.; Holmes, T. R.; Bolten, J. D.

2012-12-01

266

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

267

Vegetation heterogeneity and landscape position exert strong controls on soil CO2 efflux in a moist, Appalachian watershed  

NASA Astrophysics Data System (ADS)

In topographically complex watersheds, landscape position and vegetation heterogeneity can alter the soil water regime through both lateral and vertical redistribution, respectively. These alterations of soil moisture may have significant impacts on the spatial heterogeneity of biogeochemical cycles throughout the watershed. To evaluate how landscape position and vegetation heterogeneity affect soil CO2 efflux (FSOIL) we conducted observations across the Weimer Run watershed (373 ha), located near Davis, West Virginia, for three growing seasons with varying precipitation (2010 - 1042 mm; 2011 - 1739 mm; 2012 - 1244 mm; precipitation data from BDKW2 station, MesoWest, University of Utah). An apparent soil temperature threshold of 11 °C at 12 cm depth on FSOIL was observed in our data - where FSOIL rates greatly increase in variance above this threshold. For analysis, FSOIL values above this threshold were isolated and examined. Differences in FSOIL among years were apparent by elevation (F4,633 = 3.17; p = 0.013) and by vegetation cover (F4, 633 = 2.96; p = 0.019). For the Weimer Run watershed, vegetation exerts the major control on soil CO2 efflux (FSOIL), with the plots beneath shrubs at all elevations for all years showing the greatest mean rates of FSOIL (6.07 ?mol CO2 m-2 s-1) compared to plots beneath closed-forest canopy (4.69 ?mol CO2 m-2 s-1) and plots located in open, forest gaps (4.09 ?mol CO2 m-2 s-1) plots. During periods of high soil moisture, we find that CO2 efflux rates are constrained and that maximum efflux rates in this system occur during periods of average to below average soil water availability. These findings offer valuable insight into the processes occurring within these topographically complex, temperate and humid systems, and the interactions of abiotic and biotic factors mediating biogeochemical cycles. With possible changing rainfall patterns as predicted by climate models, it is important to understand the couplings between water and carbon cycling at the watershed and landscape scales, and their potential dynamics under global change scenarios.

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

2014-12-01

268

Soil and vegetation carbon in urban ecosystems: The importance of urban definition and scale  

NASA Astrophysics Data System (ADS)

There is conflicting evidence about the importance of soils and vegetation in urban carbon metabolism that is caused, in part, by inconsistent definitions of 'urban' land use. In Massachusetts, the US census estimates that 36% of the state is 'urban', yet remote sensing observations reveal that 50% of this urban area is forest or forested wetlands. While both of these estimates can be correct, the importance of soils and vegetation on the carbon metabolism of urban areas is clearly dependent on whether municipal, physical, or social definitions of urban are applied. We quantified urban ecosystem contributions to terrestrial C pools in the Boston Metropolitan Statistical Area (MSA) using several alternative urban definitions. Aboveground biomass (DBH ? 5 cm) for the MSA was 7.2 ± 0.4 kg C/m2, reflecting a high proportion of forest cover. Vegetation C was highest in forest (11.6 ± 0.5 kg C/m2) followed by residential (4.6 ± 0.5 kg C/m2) and then other developed (2.0 ± 0.4 kg C/m2) land uses. Soil C (0 to 10 cm) followed the same pattern of decreasing C concentration from forest, to residential, to other developed land uses (4.1 ± 0.1, 4.0 ± 0.2, and 3.3 ± 0.2 kg C/m2, respectively). Soil N concentrations were higher in urban areas than non-urban areas of the same land use type, except for residential areas, which had similarly high soil N concentrations. Urban soil (1 m depth) and vegetation C stocks spanned a wide range, from 14.4 to 54.5 Tg C and from 4.2 to 27.3 Tg C, respectively, depending on the urban definition that was used. Conclusions about the importance of soils and vegetation in urban ecosystems are very sensitive to the definition of urban used by the investigators. Urban areas are rapidly expanding in their extent; a systematic understanding of how our development patterns influence urban carbon metabolism, including vegetation and soils, is necessary to inform future development choices.

Raciti, S. M.; Hutyra, L.; Rao, P.; Finzi, A. C.

2011-12-01

269

Growth response to different constant soil moisture levels in maize ( Zea mays L.) during the vegetative phase  

Microsoft Academic Search

The effect of different constant soil moisture levels (90, 60, 30% and 90, 60, 40% respectively, of the maximum capillary\\u000a capacity) on the vegetative growth of maize was studied by the methods of growth analysis. The constant soil moisture in vegetation\\u000a pots was maintained by means of the injection method. The constantly decreased soil moisture was applied in one experiment

J. Václavík

1967-01-01

270

Pesticide residues in soils, sediments, and vegetables in the Red River Delta, northern Vietnam.  

PubMed

This study assessed pesticide residues in soils, sediments, and vegetables in the Xuan Khe and Hop Ly communes located along the Chau Giang River in the Red River Delta, northern Vietnam. Samples were collected from agricultural areas within and outside of embankments built to prevent flooding. In Xuan Khe, the soils outside of the embankment were more clayey with higher organic matter contents compared with the inside, due to selective deposition during river flooding. Many of the soils contained significant amounts of pesticides including dichlorodiphenyltrichloroethane (DDT), dicofol, isoprothiolane, and metalaxyl although their levels were below the maximum allowable concentration set by the Vietnamese government. The spectrum of DDT derivatives found suggested that the source of DDTs was not contaminated dicofol. Soils in Hop Ly resembled soils in Xuan Khe but were relatively sandy; one field showed appreciable contents of DDT derivatives. The ratios of (p,p(')-dichlorodiphenyldichloroethylene + p,p(')-dichlorodiphenyldichloroethane)/ summation operatorDDT in the surface and subsurface soils in Hop Ly were 0.34 and 0.57, suggesting that the DDTs originated from recent application. Pesticide residues in soils were not likely to translocate into vegetable crops, except for metalaxyl. High concentrations of cypermethrins in kohlrabi leaves could be ascribed to foliar deposition. PMID:19757109

Nishina, Takuro; Kien, Chu Ngoc; Noi, Nguyen Van; Ngoc, Ha Minh; Kim, Chul-Sa; Tanaka, Sota; Iwasaki, K?z?

2010-10-01

271

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

PubMed

Controlled trampling was conducted to investigate the trampling resistance of contrasting high fertility basaltic and low fertility rhyolitic soils and their associated highland tropical rainforest vegetation in north east Australia's Wet Tropics. Although this approach has been taken in numerous studies of trampling in a variety of ecosystem types (temperate and subtropical forest, alpine shrubland, coral reef and seagrass beds), the experimental method does not appear to have been previously applied in a tropical rainforest context. Ground vegetation cover and soil penetration resistance demonstrated variable responses to trampling. Trampling, most noticeably after 200 and 500 passes reduced organic litter cover. Bulk density increased with trampling intensity, particularly on basalt soils as rhyolite soils appeared somewhat resistant to the impacts of trampling. The permeability of the basalt and rhyolite soils decreased markedly with increased trampling intensity, even after only 75 passes. These findings suggest physical and hydrological changes may occur rapidly in tropical rainforest soils following low levels of trampling, particularly on basalt soils. PMID:12927152

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

2003-09-01

272

Insights into biogeochemical cycling from a soil evolution model and long-term chronosequences  

NASA Astrophysics Data System (ADS)

Despite the importance of soil processes for global biogeochemical cycles, our capability for predicting soil evolution over geological timescales is poorly constrained. We attempt to probe our understanding and predictive capability of this evolutionary process by developing a mechanistic soil evolution model, based on an existing model framework, and comparing the predictions with observations from soil chronosequences in Hawaii. Our soil evolution model includes the major processes of pedogenesis: mineral weathering, percolation of rainfall, leaching of solutes, surface erosion, bioturbation, the effects of vegetation in terms of organic matter input and nutrient cycling and can be applied to various bedrock compositions and climates. The specific properties the model simulates over timescales of tens to hundreds of thousand years are, soil depth, vertical profiles of elemental composition, soil solution pH and organic carbon distribution. We demonstrate with this model the significant role that vegetation plays in accelerating the rate of weathering and hence soil profile development. Comparisons with soils that have developed on Hawaiian basalts reveal a remarkably good agreement with Na, Ca and Mg profiles suggesting that the model captures well the key components of soil formation. Nevertheless, differences between modelled and observed K and P are substantial. The fact that these are important plant nutrients suggests that a process likely missing from our model is the active role of vegetation in selectively acquiring nutrients. This study therefore indirectly indicates the valuable role that vegetation can play in accelerating the weathering and thus release of these globally important nutrients into the biosphere.

Johnson, M. O.; Gloor, M.; Kirkby, M. J.; Lloyd, J.

2014-12-01

273

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

SciTech Connect

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

P.R. Fresquez

2004-10-01

274

Improving sensitivity to vegetation variability in the EC-Earth Earth System Model  

NASA Astrophysics Data System (ADS)

The EC-Earth earth system model has been recently developed to include the dynamics of vegetation through the coupling with the LPJ-Guess model. In its original formulation, the coupling between atmosphere and vegetation variability is simply operated by the vegetation Leaf Area Index (LAI), which affects climate by only changing the vegetation physiological resistance to evapotranspiration. This coupling with no implied change of the vegetation fractional coverage has been reported in previous work to have a weak effect on the surface climate modeled by EC-Earth. The effective vegetation fractional coverage can vary at seasonal and interannual time-scales as a function of leaf-canopy growth, phenology and senescence, and therefore affect biophysical parameters such as the surface roughness, albedo and soil field capacity. To adequately represent this effect in EC-Earth, we included an exponential dependence of the vegetation density to the LAI, based on a Lambert-Beer formulation. By comparing historical 20th-century simulations and retrospective forecasts performed applying the new effective fractional-coverage parameterization with the respective reference simulations using the original constant vegetation-fraction, it is demonstrated an increased effect of vegetation on the EC-Earth surface climate. The analysis shows noticeable sensitivity of EC-Earth surface climate at seasonal to interannual time-scales due to the variability of vegetation effective fractional coverage. Particularly large effects are shown over boreal winter middle-to-high latitudes, where the cooling effect of the new parameterization appears to correct the warm biases of the control simulations.

Alessandri, Andrea; Catalano, Franco; De Felice, Matteo

2014-05-01

275

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

PubMed Central

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

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

2014-01-01

276

Biomarker patterns in present-day vegetation: consistency and variation - A study on plaggen soils  

NASA Astrophysics Data System (ADS)

Biomarker patterns in present-day vegetation are commonly used as proxies to reconstruct paleo-vegetation composition, land use history and to elucidate carbon cycling. Plaggen soils are formed by diverse vegetational inputs during century-long plaggen (i.e. sod) application associated with plaggen-agriculture on poor soils in north-western Europe. This resulted in remarkably stable organic matter. Plant source identification by biomarkers could provide insight in yet unknown stabilization mechanisms and the fate of organic matter upon ongoing land use change. The current rationale behind biomarker-based source identification is that patterns observed in present-day vegetation are generally representative with little random variation. However, our knowledge on variability and consistency of biomarker patterns is yet scarce. Therefore, to assess the applicability of biomarkers for source identification in plaggen soils, we analyzed published n-alkane and n-alcohol patterns of species and their various parts which contribute(d) input to plaggen soils. We considered shrubs, trees and grass species and evaluated rescaled patterns (i.e. relative abundances in chain-length range C17-36), odd-over-even predominance (OEP) and predominant n-alkanes. In addition, we explicitly looked into potential sources of systematic variation, e.g. spatial variation (climate, site conditions), temporal variation (seasonality, ontogeny) and laboratory methodology (extraction technique: washing/shaking, Soxhlet/ASE, saponification). We found meaningful clustering of n-alkanes C27, C29, C31 and C33, allowing for clear distinction of input by shrubs, trees and grasses to plaggen soils. Combination of these homologues with complete n-alkane patterns (C17-36) and OEP enabled further differentiation, while n-alcohols patterns were less distinct. Current limitation is the lack of extended and diverse quantitative records on biomarker patterns, especially for n-alcohols, non-leaf and belowground tissues, which hindered full statistical analysis. On species level we also recognized outliers and spreading. Systematic variation was indicated among tree species according to spatial conditions and by ontogeny. Yet, observed effects were ambiguous for other variation sources. This study highlights clear opportunities for application of biomarker patterns for source identification and elucidation of stabilization processes in (plaggen) soils. At the same time, application is challenged by systematic variation. Further research is key to quantify controls, magnitude and potential correction factors for such systematic variation. This would validate the use of n-alkane and n-alcohol patterns across broad spatial and temporal scales or identify boundaries wherein their consistency is ensured. Likely, these challenges apply to vegetation in a broad perspective, transcending plaggen vegetation, as assessment and application of present-day vegetation patterns is emerging.

Kirkels, Frédérique; Jansen, Boris; Kalbitz, Karsten

2013-04-01

277

The Impact of Soil Reflectance on the Quantification of the Green Vegetation Fraction from NDVI  

NASA Technical Reports Server (NTRS)

The green vegetation fraction (Fg) is an important climate and hydrologic model parameter. A common method to calculate Fg is to create a simple linear mixing rnodeP between two NDVI endmembers: bare soil NDVI (NDVI(sub o)) and full vegetation NDVI (NDVI(sub infinity)). Usually it is assumed that NDVI(sub o), is close to zero (NDVI(sub o) approx.-0.05) and is generally chosen from the lowest observed NDVI values. However, the mean soil NDVI computed from 2906 samples is much larger (NDVI=0.2) and is highly variable (standard deviation=O. 1). We show that the underestimation of NDVI(sub o) yields overestimations of Fg. The largest errors occur in grassland and shrubland areas. Using parameters for NDVI(sub o) and NDVI(sub infinity) derived from global scenes yields overestimations of Fg ((Delta) Fg*) that are larger than 0.2 for the majority of U.S. land cover types when pixel NDVI values are 0.2soil reflectance.

Montandon, L. M.; Small, E. E.

2008-01-01

278

Coupling a Canopy Reflectance Model with a Global Vegetation Model  

Microsoft Academic Search

Assimilation of Earth Observation (EO) data into Dynamic Vegetation Models (DVMs) can either be via derived products (e.g., LAI or fAPAR) or through radiances. Successful assimilation generally requires that the distribution of errors in an observed variable is well known. Radiance measurements conform to this requirement more strongly than derived products which have undergone more complex processing and whose relation

Tristan Quaife; Philip Lewis; Mathias Disney; Mark Lomas; Ian Woodward; Ghislain Picard

2004-01-01

279

Estimating soil water retention using soil component additivity model  

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

280

CLASSIFICATION OF COAL SURFACE MINE SOIL MATERIAL FOR VEGETATION MANAGEMENT AND SOIL WATER QUALITY  

EPA Science Inventory

An Alabama minesoil classification system was developed based on soil texture, soil color value and soil pH. Only five different soil classes were found in this study. However, the classification scheme allows for the inclusion of any minesoil that occurs on the basis of its text...

281

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

SciTech Connect

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

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

2002-08-01

282

Methane uptake and nitrous oxide emission in Japanese forest soils and their relationship to soil and vegetation types  

Microsoft Academic Search

To determine the means and variations in CH4 uptake and N2O emission in the dominant soil and vegetation types to enable estimation of annual gases fluxes in the forest land of Japan, we measured monthly fluxes of both gases using a closed-chamber technique at 26 sites throughout Japan over 2 years. No clear seasonal changes in CH4 uptake rates were observed

Tomoaki Morishita; Tadashi Sakata; Masamichi Takahashi; Shigehiro Ishizuka; Takeo Mizoguchi; Yoshiyuki Inagaki; Kazuhiko Terazawa; Satoshi Sawata; Masanori Igarashi; Hiroshi Yasuda; Yasuhiro Koyama; Yoshihito Suzuki; Nobuyuki Toyota; Masamichi Muro; Masaru Kinjo; Hirokazu Yamamoto; Daitaro Ashiya; Yoichi Kanazawa; Tetsu Hashimoto; Hidetaka Umata

2007-01-01

283

Evaluation of a new model of aeolian transport in the presence of vegetation  

USGS Publications Warehouse

Aeolian transport is an important characteristic of many arid and semiarid regions worldwide that affects dust emission and ecosystem processes. The purpose of this paper is to evaluate a recent model of aeolian transport in the presence of vegetation. This approach differs from previous models by accounting for how vegetation affects the distribution of shear velocity on the surface rather than merely calculating the average effect of vegetation on surface shear velocity or simply using empirical relationships. Vegetation, soil, and meteorological data at 65 field sites with measurements of horizontal aeolian flux were collected from the Western United States. Measured fluxes were tested against modeled values to evaluate model performance, to obtain a set of optimum model parameters, and to estimate the uncertainty in these parameters. The same field data were used to model horizontal aeolian flux using three other schemes. Our results show that the model can predict horizontal aeolian flux with an approximate relative error of 2.1 and that further empirical corrections can reduce the approximate relative error to 1.0. The level of error is within what would be expected given uncertainties in threshold shear velocity and wind speed at our sites. The model outperforms the alternative schemes both in terms of approximate relative error and the number of sites at which threshold shear velocity was exceeded. These results lend support to an understanding of the physics of aeolian transport in which (1) vegetation's impact on transport is dependent upon the distribution of vegetation rather than merely its average lateral cover and (2) vegetation impacts surface shear stress locally by depressing it in the immediate lee of plants rather than by changing the bulk surface's threshold shear velocity. Our results also suggest that threshold shear velocity is exceeded more than might be estimated by single measurements of threshold shear stress and roughness length commonly associated with vegetated surfaces, highlighting the variation of threshold shear velocity with space and time in real landscapes.

Li, Junran; Okin, Gregory S.; Herrick, Jeffrey E.; Belnap, Jayne; Miller, Mark E.; Vest, Kimberly; Draut, Amy E.

2013-01-01

284

A model of goal directed vegetable parenting practices  

Technology Transfer Automated Retrieval System (TEKTRAN)

The aim of this study was to explore factors underlying parents' motivations to use vegetable parenting practices (VPP) using the Model of Goal Directed Vegetable Parenting Practices (MGDVPP) (an adaptation of the Model of Goal Directed Behavior) as the theoretical basis for qualitative interviews. ...

285

Patch dynamics in arid lands: localized effects of Acacia papyrocarpa on soils and vegetation of open woodlands of south Australia  

Microsoft Academic Search

Although the importance of plant-created heterogeneity in arid lands has long been recognized, little information is available on the dynamics of these patches. We studied the changes in soil and vegetation associated with the presence of a long-lived tree, Acacia papyrocarpa, in arid lands of south Australia. The soil under young individuals was not different from the soil in the

Jose M. Facelli; Daniel J. Brock

2000-01-01

286

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

E-print Network

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

Winter, Jonathan (Jonathan Mark)

2010-01-01

287

Vegetation, soil property and climatic controls over greenhouse gas fluxes in a blanket peatland hosting a wind farm  

NASA Astrophysics Data System (ADS)

Peatlands are important carbon (C) stores, with boreal and subarctic peatlands containing 15-30 % of the world soil carbon stock (Limpens et al., 2008). Research has demonstrated that greenhouse gas (GHG) fluxes in peatlands are influenced by vegetation, soil property and climatic variables, including plant functional type (PFT), water table height and temperature. In this paper we present data from Black Law Wind Farm, Scotland, where we examined the effect of a predicted wind turbine-induced microclimatic gradient and PFT on carbon dioxide (CO2) and methane (CH4) fluxes. Moreover, we determined the role of vegetation, soil property and climatic variables as predictors of the variation in CO2 and CH4 emissions. We measured CO2 and CH4 at 48 plots within Black Law Wind Farm at monthly intervals from May 2011 to April 2012. Four sampling sites were located along a predicted wind turbine-induced microclimatic gradient. At each site four blocks were established, each with plots in areas dominated by mosses, sedges and shrubs. Plant biomass and PFT (vegetation factors); soil moisture, water table height, peat depth, C content, nitrogen (N) content and C:N (soil properties); and soil temperature and photosynthetically active radiation (PAR) (climatic variables) were measured. Analysis of variance (ANOVA) models based on the microclimatic gradient site, PFT and season when measurements were made explained 58 %, 44 % and 49 % of the variation in ecosystem respiration, photosynthesis and CH4, respectively. Site, PFT, season and their interactions were all significant for respiration and photosynthesis (with the exception of the PFT*site interaction) but for CH4 only the main effects were significant. Parsimonious ANOVA models using the biotic, soil property and climatic explanatory data explained 62 %, 55 % and 49 % of the variation in respiration, photosynthesis and CH4, respectively. Published studies (Baidya Roy and Traiteur 2010; Zhou et al., 2012) and preliminary results from this study suggest that a wind turbine-induced microclimatic effect may exist. Consequently, given that the climatic variables, factors influenced by changes in the climate, and their interactions affect GHG fluxes, the operational effects of wind farms on peatland ecosystems may need to be taken into account when considering their full life cycle carbon budget. Baidya Roy, S. and J. J. Traiteur (2010). Impacts of wind farms on surface air temperatures, Proceedings of the National Academy of Sciences, 109: 15679-15684. Limpens, J. et al. (2008). Peatlands and the carbon cycle: from local processes to global implications - a synthesis, Biogeosciences, 5(5): 1475-1491. Zhou, L., et al. (2012). Impacts of wind farms on land surface temperature, Nature Climate Change, 2: 539-543.

Armstrong, Alona; Waldron, Susan; Ostle, Nick; Whitaker, Jeanette

2013-04-01

288

Modelling Vegetation Cover Dynamics of the Niger Floodplain in Mali, Westafrica, Using Multitemporal MERIS Full Resolution and TERRA -ASTER Data  

NASA Astrophysics Data System (ADS)

This presentation aims at showing the potential of a combined use of multi-temporal data from two different sensors (MERIS and TERRA ASTER) for an analysis of vegetation cover changes in semi-arid environments. While MERIS data mainly provide information about the vegetation cover density, ASTER data were used to analyse soil properties -especially soil brightness and soil wetness. An algorithm is proposed that uses atmospherically corrected surface reflectance values from MERIS and ASTER measurements. These values are subsequently splitted into a signal component that is caused by the vegetation cover and the background component (triggered by soil properties) using a linear spectral unmixing approach. Vegetation cover then is described by Vegetation Indices (MGVI, NDVI / SAVI) that were calculated from the vegetation signal component. Finally, these vegetation parameter were classified for all multi-temporal MERIS data using the EM algorithm to derive the temporal behaviour of vegetation pattern at the Inland Delta. The algorithm provides, as results, a fractional vegetation cover, a vegetation density value and information on the soil type. A detailed mapping of the spatio-temporal vegetation cover patterns for the Niger Inland Delta during the period of 2002 -2005 is another outcome of this study in addition to an in-depth evaluation of the applicability of the used VIs for environments with sparse vegetation covers. Located in the western Sahel of Africa, (1330' N -17 N and 230' W -530' W), the Niger Inland Delta is one of the largest floodplains in the world. The geographic term "Niger Inland Delta" represents a vast, extremely flat area of around 40.000 km extend, which is annually inundated by water of the Niger -Bani riversystem. In contrast to its semi -arid surrounding, the delta's ecology can be described as a mosaic of permanent, periodical and episodically flooded areas. Their extend varies both in scale and time due to irregularities of amount as well as seasonal distribution of the annual rainfall in the catchment areas and the resulting water supply contributed by the river system. Due to the relatively good availability of (surface) water, the Niger Inland Ecosystem serves as stop-over for many migrating birds and other wildlife species as well as an eonomic base for farmers and pastoral people. As a consequence, the entire Niger Inland Delta has been declared as protected RAMSAR site in 2004. Interaction among pre-flood, flood and post-flood conditions strongly affect the patterns of landcover in and around the delta as vegetation cover is strongly correlated with the availability of surface water. The Inland Delta is dominantly covered by (irrigated) fields or grasslands during flood and post-flood periods (October to January), while most of the photosynthetically active vegetation withers during the rest of the year. This yields in highly vibrant vegetation cover, although the vegetation cover density remains low even during flood period for most of the Inland Delta. This study analyses the intra-annual dynamics as well as changes in vegetation cover between individual years by interpreting 17 MERIS full resolution data over the period from Aug. 2002 to June 2005. MERIS sensor provides measurements from 15 spectral bands within the VIS and NIR part of the EMS with 300 m spatial resolution. Thus allowing for analyses at a regional scale level with high sensitivity for the amount of green vegetation. Short time dynamics of vegetation are related to changes in vegetation cover density. These changes were modelled with Vegetation Indices (VI) as parameter. To overcome well known problems related with NDVIs dependence of illumination and viewing angle, background signal (soil brightness) and changes in humidity, the MGVI was used as indix to derive more sophisticated biophysical information in addition to the classical NDVI. Soil types influence the remotely sensed signal significantly due to the overall sparse vegetation cover. Information about soil brightness and wetness were derived from dat

Seiler, Ralf

289

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

290

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

291

Stochastic Modeling of Soil Salinity  

E-print Network

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

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

2012-01-01

292

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

PubMed Central

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

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

2002-01-01

293

Environmental controls and the influence of vegetation type, fine roots and rhizomorphs on diel and seasonal variation in soil respiration.  

PubMed

Characterization of spatial and temporal variation of soil respiration coupled with fine root and rhizomorph dynamics is necessary to understand the mechanisms that regulate soil respiration. A dense wireless network array of soil CO2 sensors in combination with minirhizotron tubes was used to continuously measure soil respiration over 1 yr in a mixed conifer forest in California, USA, in two adjacent areas with different vegetation types: an area with woody vegetation (Wv) and an area with scattered herbaceous vegetation (Hv). Annual soil respiration rates and the lengths of fine roots and rhizomorphs were greater at Wv than at Hv. Soil respiration was positively correlated with fine roots and rhizomorphs at Wv but only with fine roots at Hv. Diel and seasonal soil respiration patterns were decoupled with soil temperature at Wv but not at Hv. When decoupled, higher soil respiration rates were observed at increasing temperatures, demonstrating a hysteresis effect. The diel hysteresis at Wv was explained by including the temperature-dependent component of soil respiration and the variation dependent on photosynthetically active radiation. The results show that vegetation type and fine root and rhizomorph dynamics influence soil respiration in addition to changes in light, temperature and moisture. PMID:19086292

Vargas, Rodrigo; Allen, Michael F

2008-07-01

294

Pan-Arctic linkages between snow accumulation and growing season air temperature, soil moisture and vegetation  

NASA Astrophysics Data System (ADS)

Arctic field studies have indicated that the air temperature, soil moisture and vegetation at a site influence the quantity of snow accumulated, and that snow accumulation can alter growing season soil moisture and vegetation. Climate change is predicted to bring about warmer air temperatures, greater snow accumulation and northward movements of the shrub and tree lines. Understanding the response of northern environments to changes in snow and growing season land surface characteristics requires: (1) insights into the present-day linkages between snow and growing season land surface characteristics; and (2) the ability to continue to monitor these associations over time across the vast pan-Arctic. The objective of this study was therefore to examine the pan-Arctic (north of 60° N) linkages between two temporally distinct data products created from AMSR-E satellite passive microwave observations: GlobSnow snow water equivalent, and NTSG (growing season air temperature, soil moisture and vegetation transmissivity). Due to the complex and interconnected nature of processes determining snow and growing season land surface characteristics, these associations were analyzed using the modern non-parametric technique of Alternating Conditional Expectations (ACE), as this approach does not impose a predefined analytic form. Findings indicate that regions with lower vegetation transmissivity (more biomass) at the start and end of the growing season tend to accumulate less snow at the start and end of the snow season, possibly due to interception and shading. Warmer air temperatures at the start and end of the growing season were associated with diminished snow accumulation at the start and end of the snow season. High latitude sites with warmer mean annual growing season temperatures tended to accumulate more snow, probably due to the greater availability of water vapor for snow season precipitation at warmer locations. Regions with drier soils preceding snow onset tended to accumulate greater quantities of snow, likely because drier soils freeze faster and more thoroughly than wetter soils. Understanding and continuing to monitor these linkages at the regional scale using the ACE approach can allow insights to be gained into the complex response of Arctic ecosystems to climate-driven shifts in air temperature, vegetation, soil moisture and snow accumulation.

Luus, K. A.; Gel, Y.; Lin, J. C.; Kelly, R. E. J.; Duguay, C. R.

2013-01-01

295

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

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

296

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

SciTech Connect

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

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

2008-03-31

297

INTERCOMPARISON OF ALTERNATIVE VEGETATION DATABASES FOR REGIONAL AIR QUALITY MODELING  

EPA Science Inventory

Vegetation cover data are used to characterize several regional air quality modeling processes, including the calculation of heat, moisture, and momentum fluxes with the Mesoscale Meteorological Model (MM5) and the estimate of biogenic volatile organic compound and nitric oxide...

298

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

SciTech Connect

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

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

1994-06-01

299

A fully traits-based approach to modeling global vegetation distribution  

PubMed Central

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

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

2014-01-01

300

Impact of vegetation removal and soil aridation on diurnal temperature range in a semiarid region: Application to the Sahel  

PubMed Central

Increased clouds and precipitation normally decrease the diurnal temperature range (DTR) and thus have commonly been offered as explanation for the trend of reduced DTR observed for many land areas over the last several decades. Observations show, however, that the DTR was reduced most in dry regions and especially in the West African Sahel during a period of unprecedented drought. Furthermore, the negative trend of DTR in the Sahel appears to have stopped and may have reversed after the rainfall began to recover. This study develops a hypothesis with climate model sensitivity studies showing that either a reduction in vegetation cover or a reduction in soil emissivity would reduce the DTR by increasing nighttime temperature through increased soil heating and reduced outgoing longwave radiation. Consistent with empirical analyses of observational data, our results suggest that vegetation removal and soil aridation would act to reduce the DTR during periods of drought and human mismanagement over semiarid regions such as the Sahel and to increase the DTR with more rainfall and better human management. Other mechanisms with similar effects on surface energy balance, such as increased nighttime downward longwave radiation due to increased greenhouse gases, aerosols, and clouds, would also be expected to have a larger impact on DTR over drier regions. PMID:17986620

Zhou, Liming; Dickinson, Robert E.; Tian, Yuhong; Vose, Russell S.; Dai, Yongjiu

2007-01-01

301

Impact of vegetation removal and soil aridation on diurnal temperature range in a semiarid region: application to the Sahel.  

PubMed

Increased clouds and precipitation normally decrease the diurnal temperature range (DTR) and thus have commonly been offered as explanation for the trend of reduced DTR observed for many land areas over the last several decades. Observations show, however, that the DTR was reduced most in dry regions and especially in the West African Sahel during a period of unprecedented drought. Furthermore, the negative trend of DTR in the Sahel appears to have stopped and may have reversed after the rainfall began to recover. This study develops a hypothesis with climate model sensitivity studies showing that either a reduction in vegetation cover or a reduction in soil emissivity would reduce the DTR by increasing nighttime temperature through increased soil heating and reduced outgoing longwave radiation. Consistent with empirical analyses of observational data, our results suggest that vegetation removal and soil aridation would act to reduce the DTR during periods of drought and human mismanagement over semiarid regions such as the Sahel and to increase the DTR with more rainfall and better human management. Other mechanisms with similar effects on surface energy balance, such as increased nighttime downward longwave radiation due to increased greenhouse gases, aerosols, and clouds, would also be expected to have a larger impact on DTR over drier regions. PMID:17986620

Zhou, Liming; Dickinson, Robert E; Tian, Yuhong; Vose, Russell S; Dai, Yongjiu

2007-11-13

302

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

NASA Astrophysics Data System (ADS)

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

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

2007-07-01

303

Understanding Groundwater Uptake by Phreatophytic Vegetation using a System Dynamics Modeling Approach  

NASA Astrophysics Data System (ADS)

Modeling root water uptake provides a powerful tool for illustrating the tight linkage of phreatophytic vegetation with spatial and temporal soil water content variation and groundwater level fluctuations. In this study, we develop a new model framework to simulate root water uptake of phreatophytic vegetation using system dynamics approach. The model simulates root water uptake from saturated and unsaturated zones driven by the potential gradients along the groundwater-soil-plant-atmosphere continuum (GSPAC). It incorporates variable soil and plant hydraulic conductivity properties. A new water stress function is introduced; it considers the influence of both soil water and groundwater on phreatophyte water stress. This function is based on the "vulnerability curve" theory that the loss of hydraulic conductance along the soil-plant pathway limits the plant's capability of extracting and transporting water for transpiration. The model calculates energy balance (water potential changes) and water balance (water content changes) in both soil and plant media simultaneously and has the ability to simulate hydraulic redistribution. This model is applied to simulate water uptake of Quercus douglasii (blue oak) in a California savanna; this species has previously been identified as an obligate phreatophyte. The model results show good agreement with the measured ET, soil moisture, and leaf water potential data. The model indicates that the primary water source of blue oak switches from soil water in wet season to groundwater in dry season. In June, July and August, the average groundwater uptake rate is 13 mm/month, which contributes over 90% of dry season transpiration. During the extreme dry period, the rhizosphere resistance increases significantly and becomes the dominant resistance along the GSPAC. Under such conditions, uptake of groundwater becomes more thermodynamically favorable than uptake of soil water. In addition, the model predicts that during the dry season, cavitation will lead to a hydraulic conductivity loss of approximately 85% in the shallow roots, further constraining soil water uptake. The new water stress function shows good performance in simulating daily transpiration with R-squared value of 0.68. The function also reproduces the physiological interactions and feedbacks between transpiration and root and stomatal conductance—root hydraulic conductance loss reduces stomatal conductance and stomatal conductance reduces transpiration rate to regulate plant water potential and prevent plant hydraulic failure. Hydraulic redistribution leads to significant soil water redistribution and promotes over 8% water uptake for annual transpiration. The model illustrates that with the existence of phreatophytes, deep groundwater can hydraulically impact top soil layers through plant water uptake and hydraulic redistribution.

Gou, S.; Miller, G. R.

2012-12-01

304

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

Microsoft Academic Search

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

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

2010-01-01

305

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

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

306

Impacts of Experimentally Applied Mountain Biking and Hiking on Vegetation and Soil of a Deciduous Forest  

Microsoft Academic Search

Many recent trail degradation problems have been attributed to mountain biking because of its alleged capacity to do more\\u000a damage than other activities, particularly hiking. This study compared the effects of experimentally applied mountain biking\\u000a and hiking on the understory vegetation and soil of a deciduous forest. Five different intensities of biking and hiking (i.e.,\\u000a 0, 25, 75, 200 and

EDEN THURSTON; RICHARD J. READER

2001-01-01

307

Measurement of directional thermal infrared emissivity of vegetation and soils  

SciTech Connect

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

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

1995-10-01

308

Inaccuracies in soil heat flux measurement and modeling: a matter of vertical and temporal resolution?  

Microsoft Academic Search

We here demonstrate with a conceptual model of the land-atmosphere interaction and a high vertical resolution Soil Vegetation Atmosphere Transfer model that the high daily frequencies of incoming radiation play a fundamental role in the soil heat flux signal. These high frequencies remain concentrated in a very shallow layer at the surface of about 1cm, which precludes the use of

P. Gentine; D. Entekhabi

2010-01-01

309

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

USGS Publications Warehouse

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

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

2002-01-01

310

Improvements of a dynamic global vegetation model and simulations of carbon and water at an upland-oak forest  

Microsoft Academic Search

The interest in the development and improvement of dynamic global vegetation models (DGVMs), which have the potential to simulate\\u000a fluxes of carbon, water and nitrogen, along with changes in the vegetation dynamics, within an integrated system, has been\\u000a increasing. In this paper, some numerical schemes and a higher resolution soil texture dataset were employed to improve the\\u000a Sheffield dynamic Global

Jiafu Mao; Bin Wang; Yongjiu Dai; F. I. Woodward; Paul J Hanson; M. R. Lomas

2007-01-01

311

Spreading topsoil encourages ecological restoration on embankments: soil fertility, microbial activity and vegetation cover.  

PubMed

The construction of linear transport infrastructure has severe effects on ecosystem functions and properties, and the restoration of the associated roadslopes contributes to reduce its impact. This restoration is usually approached from the perspective of plant cover regeneration, ignoring plant-soil interactions and the consequences for plant growth. The addition of a 30 cm layer of topsoil is a common practice in roadslope restoration projects to increase vegetation recovery. However topsoil is a scarce resource. This study assesses the effects of topsoil spreading and its depth (10 to 30 cm) on two surrogates of microbial activity (?-glucosidase and phosphatase enzymes activity and soil respiration), and on plant cover, plant species richness and floristic composition of embankment vegetation. The study also evaluates the differences in selected physic-chemical properties related to soil fertility between topsoil and the original embankment substrate. Topsoil was found to have higher values of organic matter (11%), nitrogen (44%), assimilable phosphorous (50%) and silt content (54%) than the original embankment substrate. The topsoil spreading treatment increased microbial activity, and its application increased ?-glucosidase activity (45%), phosphatase activity (57%) and soil respiration (60%). Depth seemed to affect soil respiration, ?-glucosidase and phosphatase activity. Topsoil application also enhanced the species richness of restored embankments in relation to controls. Nevertheless, the depth of the spread topsoil did not significantly affect the resulting plant cover, species richness or floristic composition, suggesting that both depths could have similar effects on short-term recovery of the vegetation cover. A significant implication of these results is that it permits the application of thinner topsoil layers, with major savings in this scarce resource during the subsequent slope restoration work, but the quality of topsoil relative to the original substrate should be previously assessed on a site by site basis. PMID:24984137

Rivera, Desirée; Mejías, Violeta; Jáuregui, Berta M; Costa-Tenorio, Marga; López-Archilla, Ana Isabel; Peco, Begoña

2014-01-01

312

Soil warming and CO2 enrichment induce biomass shifts in alpine treeline vegetation.  

PubMed

Responses of alpine treeline ecosystems to increasing atmospheric CO2 concentrations and global warming are poorly understood. We used an experiment at the Swiss treeline to investigate changes in vegetation biomass after 9 years of free air CO2 enrichment (+200 ppm; 2001-2009) and 6 years of soil warming (+4°C; 2007-2012). The study contained two key treeline species, Larix decidua and Pinus uncinata, both approximately 40 years old, growing in heath vegetation dominated by dwarf shrubs. In 2012, we harvested and measured biomass of all trees (including root systems), above-ground understorey vegetation and fine roots. Overall, soil warming had clearer effects on plant biomass than CO2 enrichment, and there were no interactive effects between treatments. Total plant biomass increased in warmed plots containing Pinus but not in those with Larix. This response was driven by changes in tree mass (+50%), which contributed an average of 84% (5.7 kg m(-2) ) of total plant mass. Pinus coarse root mass was especially enhanced by warming (+100%), yielding an increased root mass fraction. Elevated CO2 led to an increased relative growth rate of Larix stem basal area but no change in the final biomass of either tree species. Total understorey above-ground mass was not altered by soil warming or elevated CO2 . However, Vaccinium myrtillus mass increased with both treatments, graminoid mass declined with warming, and forb and nonvascular plant (moss and lichen) mass decreased with both treatments. Fine roots showed a substantial reduction under soil warming (-40% for all roots <2 mm in diameter at 0-20 cm soil depth) but no change with CO2 enrichment. Our findings suggest that enhanced overall productivity and shifts in biomass allocation will occur at the treeline, particularly with global warming. However, individual species and functional groups will respond differently to these environmental changes, with consequences for ecosystem structure and functioning. This article is protected by copyright. All rights reserved. PMID:25471674

Dawes, Melissa A; Philipson, Christopher D; Fonti, Patrick; Bebi, Peter; Hättenschwiler, Stephan; Hagedorn, Frank; Rixen, Christian

2014-12-01

313

Spreading Topsoil Encourages Ecological Restoration on Embankments: Soil Fertility, Microbial Activity and Vegetation Cover  

PubMed Central

The construction of linear transport infrastructure has severe effects on ecosystem functions and properties, and the restoration of the associated roadslopes contributes to reduce its impact. This restoration is usually approached from the perspective of plant cover regeneration, ignoring plant-soil interactions and the consequences for plant growth. The addition of a 30 cm layer of topsoil is a common practice in roadslope restoration projects to increase vegetation recovery. However topsoil is a scarce resource. This study assesses the effects of topsoil spreading and its depth (10 to 30 cm) on two surrogates of microbial activity (?-glucosidase and phosphatase enzymes activity and soil respiration), and on plant cover, plant species richness and floristic composition of embankment vegetation. The study also evaluates the differences in selected physic-chemical properties related to soil fertility between topsoil and the original embankment substrate. Topsoil was found to have higher values of organic matter (11%), nitrogen (44%), assimilable phosphorous (50%) and silt content (54%) than the original embankment substrate. The topsoil spreading treatment increased microbial activity, and its application increased ?-glucosidase activity (45%), phosphatase activity (57%) and soil respiration (60%). Depth seemed to affect soil respiration, ?-glucosidase and phosphatase activity. Topsoil application also enhanced the species richness of restored embankments in relation to controls. Nevertheless, the depth of the spread topsoil did not significantly affect the resulting plant cover, species richness or floristic composition, suggesting that both depths could have similar effects on short-term recovery of the vegetation cover. A significant implication of these results is that it permits the application of thinner topsoil layers, with major savings in this scarce resource during the subsequent slope restoration work, but the quality of topsoil relative to the original substrate should be previously assessed on a site by site basis. PMID:24984137

Rivera, Desirée; Mejías, Violeta; Jáuregui, Berta M.; López-Archilla, Ana Isabel; Peco, Begoña

2014-01-01

314

Biostimulation of natural microbial assemblages in oil-amended vegetated and desert sub-Antarctic soils.  

PubMed

A field study was initiated in December 2000 in two selected soils of The Grande Terre (Kerguelen Archipelago) with the objective of determining the long-term effects of fertilizer addition on the biodegradation rate and the toxicity of oil residues under severe sub-Antarctic conditions. Two soils were selected. The first site supports an abundant vegetal cover; the second one was desert soil, devoid of plant material. These two soils were located in the vicinity of the permanent station of Port-aux-Français (69 degrees 42'E; 49 degrees 19'S). A series of five experimental plots (0.75 x 0.75 m) were settled firmly into each of the studied soils. Each plot received 500 mL of diesel or Arabian light crude oil, and some of them were treated with a bioremediation agent: slow-release fertilizer Inipol EAP-22 (Elf Atochem). All the plots were sampled on a regular basis over a 1 year period. Heterotrophic and hydrocarbon-degrading microorganisms increased by two orders of magnitude during the first month of the experimentation in all treated enclosures, but differences appeared between the different plots. The microbial response was improved by bioremediation treatments. However, fertilizer addition had a greater impact on the desert soil when compared to the vegetated one. All chemical indices show a reduction of alkanes and light aromatics. Toxicity results show a high variability between treatments and environmental conditions. As a conclusion, it is clear that the microbial response was rapid and efficient in spite of the severe weather conditions, and the rate of degradation was improved by bioremediation treatments. However, after 1 year of treatment, the signal of a relatively high toxicity of oiled residues remained present in the two studied soils. PMID:14681739

Delille, D; Coulon, F; Pelletier, E

2004-05-01

315

Mercury in vegetation and organic soil at an upland boreal forest site in Prince Albert National Park, Saskatchewan, Canada  

Microsoft Academic Search

We studied an upland boreal forest plot located in the Prince Albert National Park, Saskatchewan, Canada, to measure the total mercury content in vegetation and organic soil with a view to assessing the potential for mercury release during forest fires. The study area consists of two stands of vegetation regrown after fires 39 and 130 years ago, with different carbon

H. R. Friedli; L. F. Radke; N. J. Payne; D. J. McRae; T. J. Lynham; T. W. Blake

2007-01-01

316

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

PubMed

Both soil nematodes and microorganisms have been shown to be sensitive bioindicators of soil recovery in metal-contaminated habitats; however, the underlying processes are poorly understood. We investigated the relationship among soil microbial community composition, nematode community structure and soil aluminum (Al) content in different vegetated aluminum-rich ecosystems. Our results demonstrated that there were greater soil bacterial, fungal and arbuscular mycorrhizal fungal biomass in Syzygium cumini plantation, greater abundance of soil nematodes in Acacia auriculiformis plantation, and greater abundance of soil predatory and herbivorous nematodes in Schima wallichii plantation. The concentration of water-soluble Al was normally greater in vegetated than non-vegetated soil. The residual Al and total Al concentrations showed a significant decrease after planting S. cumini plantation onto the shale dump. Acid extractable, reducible and oxidisable Al concentrations were greater in S. wallichii plantation. Stepwise linear regression analysis suggests the concentrations of water-soluble Al and total Al content explain the most variance associated with nematode assembly; whereas, the abundance of early-successional nematode taxa was explained mostly by soil moisture, soil organic C and total N rather than the concentrations of different forms of Al. In contrast, no significant main effects of either Al or soil physico-chemical characteristics on soil microbial biomass were observed. Our study suggests that vegetation was the primary driver on soil nematodes and microorganisms and it also could regulate the sensitivity of bio-indicator role mainly through the alteration of soil Al and physico-chemical characteristics, and S. cumini is effective for amending the Al contaminated soils. PMID:22732942

Shao, Yuanhu; Zhang, Weixin; Liu, Zhanfeng; Sun, Yuxin; Chen, Dima; Wu, Jianping; Zhou, Lixia; Xia, Hanping; Neher, Deborah A; Fu, Shenglei

2012-11-01

317

Interactions of aluminum with forest soils and vegetation: Implications for acid deposition  

SciTech Connect

Recent evidence suggests that an important ecological consequence of acidic deposition is increased aluminum mobilization. There is concern that increased aluminum activity may produce toxic effects in forested ecosystems. My studies were concerned with the behavior of pedogenic and added aluminum in soils derived from chemically different parent material. Soil aluminum was related to the aluminum content of the vegetation found growing in the soils. In addition, aluminum levels of forest litter was compared to levels determined 40 years ago. Field, greenhouse, and laboratory investigations were conducted in which the effects of aluminum concentration on germination and early growth was determined. Soils were then used in greenhouse and laboratory studies to establish patterns of soil and plant aluminum behavior with implications to acid deposition. Results show that the amount of aluminum extracted was related to the pH value of the extracting solution and to the chemical characteristics of the soil. Some acid rain solutions extracted measurable amounts of aluminum from selected primary minerals. Germination and early growth of Pinus radiata was controlled by levels of aluminum in the soil or in solution. Field studies indicated that most forest species were sensitive to rising levels of aluminum in the soil. In general, ferns and fern allies were less sensitive to very high levels of aluminum in the soil, continuing to grow when more advanced dicots have disappeared. Aluminum tissue levels of all species were related to the concentration of aluminum in the soil as was the reappearance of species. Aluminum levels in leaf litter have risen at least 50% in the last 40 years. These values were consistent over 3 years. The implications to acid deposition were discussed.

Maynard, A.A.

1989-01-01

318

Linking riparian dynamics and groundwater: an ecohydrologic approach to modeling groundwater and riparian vegetation.  

PubMed

The growing use of global freshwater supplies is increasing the need for improved modeling of the linkage between groundwater and riparian vegetation. Traditional groundwater models such as MODFLOW have been used to predict changes in regional groundwater levels, and thus riparian vegetation potential attributable to anthropogenic water use. This article describes an approach that improves on these modeling techniques through several innovations. First, evapotranspiration from riparian/wetland systems is modeled in a manner that more realistically reflects plant ecophysiology and vegetation complexity. In the authors' model programs (RIP-ET and PRE-RIP-ET), the single, monotonically increasing evapotranspiration flux curve in traditional groundwater models is replaced with a set of ecophysiologically based curves, one for each plant functional group present. For each group, the curve simulates transpiration declines that occur both as water levels decline below rooting depths and as waters rise to levels that produce anoxic soil conditions. Accuracy is further improved by more effective spatial handling of vegetation distribution, which allows modeling of surface elevation and depth to water for multiple vegetation types within each large model cell. The use of RIP-ET in groundwater models can improve the accuracy of basin scale estimates of riparian evapotranspiration rates, riparian vegetation water requirements, and water budgets. Two case studies are used to demonstrate that RIP-ET produces significantly different evapotranspiration estimates than the traditional method. When combined with vegetation mapping and a supporting program (RIP-GIS), RIP-ET also enables predictions of riparian vegetation response to water use and development scenarios. The RIP-GIS program links the head distribution from MODFLOW with surface digital elevation models, producing moderate- to high-resolution depth-to-groundwater maps. Together with information on plant rooting depths, these can be used to predict vegetation response to water allocation decisions. The different evapotranspiration outcomes produced by traditional and RIP-ET approaches affect resulting interpretations of hydro-vegetation dynamics, including the effects of groundwater pumping stress on existing habitats, and thus affect subsequent policy decisions. PMID:16222461

Baird, Kathryn J; Stromberg, Juliet C; Maddock, Thomas

2005-10-01

319

Simulating the effects of soil organic nitrogen and grazing on arctic tundra vegetation dynamics on the Yamal Peninsula, Russia  

NASA Astrophysics Data System (ADS)

Sustainability of tundra vegetation under changing climate on the Yamal Peninsula, northwestern Siberia, home to the world's largest area of reindeer husbandry, is of crucial importance to the local native community. An integrated investigation is needed for better understanding of the effects of soils, climate change and grazing on tundra vegetation in the Yamal region. In this study we applied a nutrient-based plant community model—ArcVeg—to evaluate how two factors (soil organic nitrogen (SON) levels and grazing) interact to affect tundra responses to climate warming across a latitudinal climatic gradient on the Yamal Peninsula. Model simulations were driven by field-collected soil data and expected grazing patterns along the Yamal Arctic Transect (YAT), within bioclimate subzones C (high arctic), D (northern low arctic) and E (southern low arctic). Plant biomass and NPP (net primary productivity) were significantly increased with warmer bioclimate subzones, greater soil nutrient levels and temporal climate warming, while they declined with higher grazing frequency. Temporal climate warming of 2 °C caused an increase of 665 g m-2 in total biomass at the high SON site in subzone E, but only 298 g m-2 at the low SON site. When grazing frequency was also increased, total biomass increased by only 369 g m-2 at the high SON site in contrast to 184 g m-2 at the low SON site in subzone E. Our results suggest that high SON can support greater plant biomass and plant responses to climate warming, while low SON and grazing may limit plant response to climate change. In addition to the first order factors (SON, bioclimate subzones, grazing and temporal climate warming), interactions among these significantly affect plant biomass and productivity in the arctic tundra and should not be ignored in regional scale studies.

Yu, Qin; Epstein, Howard; Walker, Donald

2009-10-01

320

Remediation of trichloroethylene-contaminated soils by star technology using vegetable oil smoldering.  

PubMed

Self-sustaining treatment for active remediation (STAR) is an innovative soil remediation approach based on smoldering combustion that has been demonstrated to effectively destroy complex hydrocarbon nonaqueous phase liquids (NAPLs) with minimal energy input. This is the first study to explore the smoldering remediation of sand contaminated by a volatile NAPL (trichloroethylene, TCE) and the first to consider utilizing vegetable oil as supplemental fuel for STAR. Thirty laboratory-scale experiments were conducted to evaluate the relationship between key outcomes (TCE destruction, rate of remediation) to initial conditions (vegetable oil type, oil: TCE mass ratio, neat versus emulsified oils). Several vegetable oils and emulsified vegetable oil formulations were shown to support remediation of TCE via self-sustaining smoldering. A minimum concentration of 14,000mg/kg canola oil was found to treat sand exhibiting up to 80,000mg/kg TCE. On average, 75% of the TCE mass was removed due to volatilization. This proof-of-concept study suggests that injection and smoldering of vegetable oil may provide a new alternative for driving volatile contaminants to traditional vapour extraction systems without supplying substantial external energy. PMID:25528233

Salman, Madiha; Gerhard, Jason I; Major, David W; Pironi, Paolo; Hadden, Rory

2015-03-21

321

Soil bacterial community shifts in response to vegetation and soil temperature change in moist acidic tundra of Northern Alaska  

NASA Astrophysics Data System (ADS)

The effects of rising temperatures on Earth's ecosystems remain largely unknown and are an active area of research. In temperate systems, plant species often respond directly to climate forcing factors causing complex cascading effects in ecosystem C and nutrient cycling. Similarly, in the Arctic tundra, shifts in aboveground species composition and distribution have been observed in response to warming and other climate change factors, following increases in active layer depth and soil temperature. These abiotic changes provide soil microorganisms access to previously unavailable soil organic matter via thawing soils and increases soil microbial mineralization rates, suggesting that soil microorganisms may be eliciting the plant response. It is hypothesized that this release of nutrients may be providing a competitive advantage to N rich woody species, such as dwarf birch and diamond-leaf willow, over grassy species such as cottongrass tussock. Here we examine how microbial communities respond to increases in soil thermal insulation and vegetative change caused by the accumulation of winter precipitation at a snowfence installed in 1998 at Toolik Field Station, Alaska. In addition to soil temperature, increased snow depth also results in increased surface moisture, soil temperature, and active layer depth. Bacterial phylogenies and relative abundances from soils collected in August of 2012 were determined by sequencing 16S rRNA genes and analyzed using the QIIME software package. We found many significant relative abundance shifts between snow depth treatments (deep, intermediate, low) and soil depths (organic, transition, mineral), most notable of which include in an increase in Deltaproteobacteria in the deep treatment zones, a decrease in Alphaproteobacteria with increased soil depth, and a marked increase in Chloroflexi Anaerolineae (a green non-sulfur bacteria found in a wide range of habitats) in the deep treatment and mineral layers. Other interesting results include the presence of two novel, uncultured phyla of Bacteria, AD3 (phylogenetically related to green non-sulfur bacteria) which was found in mineral layers across all treatments, and OP8 (yet to be characterized), found only in the mineral layers of the deep snow depth treatment.

Ricketts, M. P.; Gonzalez-Meler, M. A.

2013-12-01

322

Assessing environmental drivers of vegetation greenness by integrating multiple earth observation data in the LPJmL dynamic global vegetation model  

NASA Astrophysics Data System (ADS)

Recently produced satellite datasets of vegetation greenness demonstrate a widespread greening of the earth in the last three decades. These positive trends in vegetation greenness are related to changes in leaf area, vegetation cover and photosynthetic activity. Climatic changes, CO2 fertilization, disturbances and other land cover changes are potential drivers of these greening trends. Nevertheless, different satellite datasets show different magnitudes and trends in vegetation greenness. This fact raises the question about the reliability of these datasets. On the other hand, global vegetation models can be potentially used to assess the effects of environmental drivers on vegetation greenness and thus to explore the environmental reliability of these datasets. Unfortunately, current vegetation models have several weaknesses in reproducing observed temporal dynamics in vegetation greenness. Our aim is to integrate multiple earth observation data sets in a dynamic global vegetation model in order to 1) improve the model's capability to reproduce observed dynamics and spatial patterns of vegetation greenness and 2) to assess the spatial and temporal importance of environmental drivers for the seasonal to decadal variability of vegetation greenness. For this purpose, we developed a data integration system for the LPJmL dynamic global vegetation model (LPJmL-DIS). We implemented a new phenology scheme in LPJmL to better represent observed temporal dynamics of FAPAR (fraction of absorbed photosynthetic active radiation). Model parameters were globally optimized using a genetic optimization algorithm. The model optimization was performed globally against 30 year FAPAR time series (GIMMS3g dataset), against 10 year albedo time series (MODIS) and global patterns of gross primary production as up-scaled from FLUXNET eddy covariance measurements. Additionally, we directly prescribed satellite observations of land and tree cover in LPJmL to better represent global vegetation distribution by still keeping major processes of vegetation dynamics like mortality and competition among plant functional types. We prescribed observed burnt areas from the GFED dataset as well as from the Alaskan and Canadian national fire databases in LPJmL to better reproduce observed fire dynamics. We evaluated LPJmL with optimized parameters against independent data streams. LPJmL with a new phenology scheme and optimized parameters better represents spatial patterns of gross primary production, biomass, soil organic carbon, evapotranspiration and tree cover than the original model. LPJmL-DIS is able to reproduce spatial patterns and observed temporal dynamics of FAPAR from seasonal to decadal scales in all major biomes. We performed several model experiments to disentangle the spatial and temporal importance of temperature, radiation, water availability, CO2 fertilization, fire activity and permafrost changes on the seasonal to decadal variability of vegetation greenness. Our results indicate that water availability is a major driver for the seasonal to decadal variability of vegetation greenness in tropical, temperate and boreal biomes. The developed LPJmL data integration system enables to reanalyse recent trends in vegetation greenness and their environmental drivers by combining earth observation data of multiple environmental variables in a consistent process-based global vegetation model framework.

Forkel, Matthias; Carvalhais, Nuno; Schaphoff, Sibyll; von Bloh, Werner; Thurner, Martin; Thonicke, Kirsten

2014-05-01

323

Contemporary “green” water flows: Simulations with a dynamic global vegetation and water balance model  

Microsoft Academic Search

“Green water”—the water stored in the soil and productively used for plant transpiration—is an important quantity particularly in rainfed agriculture (in contrast to “blue water” available in streams and lakes, on which irrigation relies). This study provides preliminary estimates of contemporary (1961–1990) global green water flows (i.e. plant transpiration), using a well-established, process-based dynamic global vegetation and water balance model,

Dieter Gerten; Holger Hoff; Alberte Bondeau; Wolfgang Lucht; Pascalle Smith; Sönke Zaehle

2005-01-01

324

Model for the genesis of coastal dune fields with vegetation  

NASA Astrophysics Data System (ADS)

Vegetation greatly affects the formation and dynamics of dune fields in coastal areas. In the present work, we use dune modeling in order to investigate the genesis and early development stages of coastal dune fields in the presence of vegetation. The model, which consists of a set of coupled equations for the turbulent wind field over the landscape, the saltation flux and the growth of vegetation cover on the surface, is applied to calculate the evolution of a sand patch placed upwind of a vegetated terrain and submitted to unidirectional wind and constant sand influx. Different dune morphologies are obtained, depending on the characteristic rate of vegetation growth relative to wind strength: barchans, transverse dunes with trailing ridges, parabolic dunes and vegetated, alongshore sand barriers or foredunes. The existence of a vegetation-free backshore is found to be important for the nucleation timescale of coastal dune generations. The role of the sand influx and of the maximum vegetation cover density for the dune shape is also discussed.

de M. Luna, Marco C. M.; Parteli, Eric J. R.; Durán, Orencio; Herrmann, Hans J.

2011-06-01

325

Simulation of soil temperature dynamics with models using different concepts.  

PubMed

This paper presents two soil temperature models with empirical and mechanistic concepts. At the test site (calcaric arenosol), meteorological parameters as well as soil moisture content and temperature at 5 different depths were measured in an experiment with 8 parcels realizing the combinations of the fertilized, nonfertilized, irrigated, nonirrigated treatments in two replicates. Leaf area dynamics was also monitored. Soil temperature was calculated with the original and a modified version of CERES as well as with the HYDRUS-1D model. The simulated soil temperature values were compared to the observed ones. The vegetation reduced both the average soil temperature and its diurnal amplitude; therefore, considering the leaf area dynamics is important in modeling. The models underestimated the actual soil temperature and overestimated the temperature oscillation within the winter period. All models failed to account for the insulation effect of snow cover. The modified CERES provided explicitly more accurate soil temperature values than the original one. Though HYDRUS-1D provided more accurate soil temperature estimations, its superiority to CERES is not unequivocal as it requires more detailed inputs. PMID:22792047

Sándor, Renáta; Fodor, Nándor

2012-01-01

326

Effects of various uranium leaching procedures on soil: Short-term vegetation growth and physiology. Progress report, April 1994  

SciTech Connect

Significant volumes of soil containing elevated levels of uranium exist in the eastern United States. The contamination resulted from the development of the nuclear industry in the United States requiring a large variety of uranium products. The contaminated soil poses a collection and disposal problem of a magnitude that justifies the development of decontamination methods. Consequently, the Department of Energy (DOE) Office of Technology Development formed the Uranium Soils Integrated Demonstration (USID) program to address the problem. The fundamental goal of the USID task group has been the selective extraction/leaching or removal of uranium from soil faster, cheaper, and safer than what can be done using current conventional technologies. The objective is to selectively remove uranium from soil without seriously degrading the soil`s physicochemical characteristics and without generating waste that is difficult to manage and/or dispose of. However, procedures developed for removing uranium from contaminated soil have involved harsh chemical treatments that affect the physicochemical properties of the soil. The questions are (1) are the changes in soil properties severe enough to destroy the soil`s capacity to support and sustain vegetation growth and survival? and (2) what amendments might be made to the leached soil to return it to a reasonable vegetation production capacity? This study examines the vegetation-support capacity of soil that had been chemically leached to remove uranium. The approach is to conduct short-term germination and phytotoxicity tests for evaluating soils after they are subjected to various leaching procedures followed by longer term pot studies on successfully leached soils that show the greatest capacity to support plant growth. This report details the results from germination and short-term phytotoxicity testing of soils that underwent a variety of leaching procedures at the bench scale at ORNL and at the pilot plant at Fernald.

Edwards, N.T.

1994-08-01

327

Appropriate scale of soil moisture retrieval from high-resolution radar imagery for bare and minimally vegetated soils 1859  

Technology Transfer Automated Retrieval System (TEKTRAN)

This research investigates the appropriate scale for watershed averaged and site specific soil moisture retrieval from high resolution radar imagery. The first approach involved filtering backscatter for input to a retrieval model that was compared against field measures of soil moisture. The seco...

328

Effects of coal-bed methane discharge waters on the vegetation and soil ecosystem in Powder River Basin, Wyoming  

USGS Publications Warehouse

Coal-bed methane (CBM) co-produced discharge waters in the Powder River Basin of Wyoming, resulting from extraction of methane from coal seams, have become a priority for chemical, hydrological and biological research during the last few years. Soil and vegetation samples were taken from affected and reference sites (upland elevations and wetted gully) in Juniper Draw to investigate the effects of CBM discharge waters on soil physical and chemical properties and on native and introduced vegetation density and diversity. Results indicate an increase of salinity and sodicity within local soil ecosystems at sites directly exposed to CBM discharge waters. Elevated concentrations of sodium in the soil are correlated with consistent exposure to CBM waters. Clay-loam soils in the study area have a much larger specific surface area than the sandy soils and facilitate a greater sodium adsorption. However, there was no significant relation between increasing water sodium adsorption ratio (SAR) values and increasing sediment SAR values downstream; however, soils exposed to the CBM water ranged from the moderate to severe SAR hazard index. Native vegetation species density was highest at the reference (upland and gully) and CBM affected upland sites. The affected gully had the greatest percent composition of introduced vegetation species. Salt-tolerant species had the greatest richness at the affected gully, implying a potential threat of invasion and competition to established native vegetation. These findings suggest that CBM waters could affect agricultural production operations and long-term water quality. ?? Springer 2005.

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

2005-01-01

329

Regression models for vegetation radar-backscattering and radiometric emission  

NASA Technical Reports Server (NTRS)

Simple regression estimation of radar backscatter and radiometric emission from vegetative terrain is proposed, based on the exact radiative transfer models. A vegetative canopy is modeled as a Rayleigh scattering layer above an irregular Kirchhoff surface. The rms errors between the exact and the estimated ones are found to be less than 5 percent for emission, and 1 dB for the backscattering case, in most practical uses. The proposed formulas are useful in quickly estimating backscattering and emission from the vegetative terrain.

Eom, H. J.

1986-01-01

330

Geothermal environmental assessment baseline study: Vegetation and soils of the Roosevelt Hot Springs geothermal resource area  

NASA Astrophysics Data System (ADS)

Identification and elemental concentrations of indigenous soil and plant systems found on the Roosevelt Hot Spring KGRA are described. Twenty-three different soils and five separate plant communities are geographically mapped and identified. One hundred forty-seven plant species were identified. Forbs, shrubs, and grasses are represented by 58, 53, and 36 species respectively. Three sites each measuring 25 hectares were selected for long-term vegetative assessment. At these locations a permanent enclosure measuring 24.4 meters x 24.4 meters was constructed to assess long-term effects livestock grazing. Biomass plant species, percentage composition, ground cover and livetock carrying capacities were determined at each site. Surface soils and Artemisia tridentata leaf tissue were collected for elemental analysis.

Brown, K. W.; Wiersma, G. B.

1981-07-01

331

Geothermal environmental assessment baseline study: vegetation and soils of the Roosevelt Hot Springs Geothermal Resource Area  

SciTech Connect

Identification and elemental concentrations of indigenous soil and plant systems found on the Roosevelt Hot Spring KGRA are described. Twenty-three different soils and five separate plant communities are geographically mapped and identified. One hundred forty-seven plant species were identified. Forbs, shrubs, and grasses are represented by 58, 53, and 36 species respectively. Three sites, each measuring 25 hectares, were selected for long-term vegetative assessment. At these locations a permanent enclosure measuring 24.4 meters x 24.4 meters was constructed to assess long-term effects of livestock grazing. Biomass, plant species, percentage composition, ground cover and livestock carrying capacities were determined at each site. Surface soils and Artemisia tridentata leaf tissue were collected for elemental analysis.

Brown, K.W.; Wiersma, G.B.

1981-07-01

332

Checking various vegetation indices for estimating vegetation in arid regions and Presented a model (Case Study:Sadough- Yazd)  

NASA Astrophysics Data System (ADS)

Vegetation is one of the natural recourses components and achieve Quantitative information of them have a major role in the management of land. Using satellite images is one of the new techniques in the field of qualitative and quantitative studies of the vegetation .Studies show that the use of spectral vegetation indices and ratios may serve as a useful approach in this area, especially in the desert zoon. In this study, using Landsat TM imagery sensors, to calculate different vegetation indices and their ability checking vegetation in arid regions. After multivariate regression analysis between the actual values and parameters, and validation of models optimal model was selected. The results showed that the index of ARVI with the corresponding coefficients is better results in estimating the amount of vegetation in arid regions. Keywords: vegetation, satellite images, vegetation index, arid region, Saduq

Kalantari, Saeideh; Zehtabian, Gholamreza; Azarnivand, Hossein; Ahmadi, Hassan

2013-04-01

333

Modeling the Hydrologic and Mechanical Effects of Riparian Vegetation on Streambank Stability  

Technology Transfer Automated Retrieval System (TEKTRAN)

Riparian vegetation reduces the risk of streambank failure by increasing bank shear strength. First, soil tensile stresses are transferred to the root system thereby reinforcing the streambank material. Second, canopy interception of rainfall and transpiration increases soil suction, increasing re...

334

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

SciTech Connect

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

Schneider, J.F.; Tomczyk, N.A.; Zellmer, S.D. [Argonne National Lab., IL (United States); Banwart, W.L. [Argonne National Lab., IL (United States)]|[Univ., of Illinois, Urbana, IL (United States). Dept., of Agronomy

1994-01-01

335

Effects of short- and long-term disturbance resulting from military maneuvers on vegetation and soils in a mixed prairie area  

USGS Publications Warehouse

Loss of grassland species resulting from activities such as off-road vehicle use increases the need for models that predict effects of anthropogenic disturbance. The relationship of disturbance by military training to plant species richness and composition on two soils (Foard and Lawton) in a mixed prairie area was investigated. Track cover (cover of vehicle disturbance to the soil) and soil organic carbon were selected as measures of short- and long-term disturbance, respectively. Soil and vegetation data, collected in 1-m 2 quadrats, were analyzed at three spatial scales (60, 10, and 1 m2). Plant species richness peaked at intermediate levels of soil organic carbon at the 10-m2 and 1-m2 spatial scales on both the Lawton and Foard soils, and at intermediate levels of track cover at all three spatial scales on the Foard soil. Species composition differed across the disturbance gradient on the Foard soil but not on the Lawton soil. Disturbance increased total plant species richness on the Foard soil. The authors conclude that disturbance up to intermediate levels can be used to maintain biodiversity by enriching the plant species pool. ?? 2005 Springer Science+Business Media, Inc.

Leis, S.A.; Engle, D.M.; Leslie, D.M., Jr.; Fehmi, J.S.

2005-01-01

336

Wind erosion in semiarid landscapes: Predictive models and remote sensing methods for the influence of vegetation  

NASA Technical Reports Server (NTRS)

The objectives of this research are: to develop and test predictive relations for the quantitative influence of vegetation canopy structure on wind erosion of semiarid rangeland soils, and to develop remote sensing methods for measuring the canopy structural parameters that determine sheltering against wind erosion. The influence of canopy structure on wind erosion will be investigated by means of wind-tunnel and field experiments using structural variables identified by the wind-tunnel and field experiments using model roughness elements to simulate plant canopies. The canopy structural variables identified by the wind-tunnel and field experiments as important in determining vegetative sheltering against wind erosion will then be measured at a number of naturally vegetated field sites and compared with estimates of these variables derived from analysis of remotely sensed data.

Musick, H. Brad

1993-01-01

337

VARIABILITY IN SOILS AND VEGETATION ASSOCIATED WITH HARVESTER ANT (POGONOMYRMEX RUGOSUS) NESTS ON A CHIHUAHUAN DESERT WATERSHED  

EPA Science Inventory

The effects of harvester ant (Pogonomyrmex rugosus) nests on the density and cover of spring annual plants and on soil characteristics were measured at three locations characterized by different soils and dominant vegetation on a desert watershed. There were few differences in ve...

338

Representing the effects of alpine grassland vegetation cover on the simulation of soil thermal dynamics by ecosystem  

E-print Network

Representing the effects of alpine grassland vegetation cover on the simulation of soil thermal and atmospheric factors on the estimation of soil surface temperature for alpine grassland ecosystems has the potential to substantially improve our understanding of the vulnerability of alpine grassland

Ickert-Bond, Steffi

339

Composition and Diversity of Soil Microbial Communities Following Vegetation Change from Grassland to Woodland: An Assessment Using Molecular Methods  

E-print Network

Composition and Diversity of Soil Microbial Communities Following Vegetation Change from Grassland) were used to quantify the diversity of soil microbial communities. La Copita Research Area, Ben Bolt microbial biomass pool. These profound changes in ecosystem structure and function are likely to influence

340

The effect of land use change on soils and vegetation over various lithological formations on Lesvos (Greece)  

Microsoft Academic Search

The effect of land use change, from arable to abandoned pasture, on soil properties and vegetation establishment was studied in hilly areas of the island of Lesvos. The main purpose of this study was to establish key indicators or land parameters that can be used for defining environmentally sensitive areas to desertification. 106 soil sites were selected in fields cultivated

C. Kosmas; M Marathianou

2000-01-01

341

Carbon mineralization in the soils under different cover crops and residue management in an intensive protected vegetable cultivation  

Microsoft Academic Search

Continuous cropping under plastic greenhouses, a common practice in intensive Chinese vegetable production systems, has led to the decline of soil productivity and crop yields. A 4-year greenhouse experiment on cucumber double-cropping systems was conducted in Changping country, Beijing, China, to investigate the effects of summer cover crops and residue management on soil microbial biomass carbon (MBC), C mineralization and

Yongqiang Tian; Juan Liu; Xuhui Wang; Lihong Gao

2011-01-01

342

Potential effects of large linear pipeline construction on soil and vegetation in ecologically fragile regions.  

PubMed

Long-distance pipeline construction results in marked human disturbance of the regional ecosystem and brings into question the safety of pipeline construction with respect to the environment. Thus, the direct environmental impact and proper handling of such large projects have received much attention. The potential environmental effects, however, have not been fully addressed, particularly for large linear pipeline projects, and the threshold of such effects is unclear. In this study, two typical eco-fragile areas in western China, where large linear construction projects have been conducted, were chosen as the case study areas. Soil quality indices (SQI) and vegetation indices (VI), representing the most important potential effects, were used to analyze the scope of the effect of large pipeline construction on the surrounding environment. These two indices in different buffer zones along the pipeline were compared against the background values. The analysis resulted in three main findings. First, pipeline construction continues to influence the nearby eco-environment even after a 4-year recovery period. During this period, the effect on vegetation due to pipeline construction reaches 300 m beyond the working area, and is much larger in distance than the effect on soil, which is mainly confined to within 30 m either side of the pipeline, indicating that vegetation is more sensitive than soil to this type of human disturbance. However, the effect may not reach beyond 500 m from the pipeline. Second, the scope of the effect in terms of distance on vegetation may also be determined by the frequency of disturbance and the intensity of the pipeline construction. The greater the number of pipelines in an area, the higher the construction intensity and the more frequent the disturbance. Frequent disturbance may expand the effect on vegetation on both sides of the pipeline, but not on soil quality. Third, the construction may eliminate the stable, resident plant community. During the recovery period, the plant community in the work area of the pipeline is replaced by some species that are rare or uncommon in the resident plant community because of human disturbance, thereby increasing the plant diversity in the work area. In terms of plant succession, the duration of the recovery period has a direct effect on the composition and structure of the plant community. The findings provide a theoretical basis and scientific foundation for improving the environmental impact assessment (EIA) of oil and gas pipeline construction as it pertains to the desert steppe ecosystem, and provide a reference point for recovery and management of the eco-environment during the pipeline construction period. PMID:25112841

Xiao, Jun; Wang, Ya-Feng; Shi, Peng; Yang, Lei; Chen, Li-Ding

2014-11-01

343

Effects of Land Cover / Land Use, Soil Texture, and Vegetation on the Water Balance of Lake Chad Basin  

NASA Astrophysics Data System (ADS)

Lake Chad Basin (LCB) has experienced drastic changes of land cover and poor water management practices during the last 50 years. The successive droughts in the 1970s and 1980s resulted in the shortage of surface water and groundwater resources. This problem of drought has a devastating implication on the natural resources of the Basin with great consequence on food security, poverty reduction and quality of life of the inhabitants in the LCB. Therefore, understanding the effects of land use / land cover must be a first step to find how they disturb cycle especially the groundwater in the LCB. The abundance of groundwater is affected by the climate change through the interaction with surface water, such as lakes and rivers, and disuse recharge through an infiltration process. Quantifying the impact of climate change on the groundwater resource requires reliable forecasting of changes in the major climatic variables and other spatial variations including the land use/land cover, soil texture, topographic slope, and vegetation. In this study, we employed a spatially distributed water balance model WetSpass to simulate a long-term average change of groundwater recharge in the LCB of Africa. WetSpass is a water balance-based model to estimate seasonal and spatial distribution of surface runoff, interception, evapotranspiration, and groundwater recharge. The model is especially suitable for studying the effect of land use/land cover change on the water regime in the LCB. The present study describes the concept of the model and its application to the development of recharge map of the LCB. The study shows that major role in the water balance of LCB. The mean yearly actual evapotranspiration (ET) from the basin range from 60mm - 400 mm, which is 90 % (69mm - 430) of the annual precipitation from 2003 - 2010. It is striking that about 50 - 60 % of the total runoff is produced on build-up (impervious surfaces), while much smaller contributions are obtained from vegetated, bare soil and open water surfaces. The result of this study also shows that runoff is high in the clay, clay loam and sandy-clay loam due to the lack of infiltration process in clay soil from capping or crusting or sealing of the soil pores, therefore this situation will aid runoff. The application of the WetSpass model shows that precipitation, soil texture and land use / land cover are three controlling factors affecting the water balance in the LCB. Key words: Groundwater recharge, surface runoff, evapotranspiration, water balance, meteorological, draught, Landuse changes, climate changes, WetSpass, GIS.

Babamaaji, R. A.; Lee, J.

2013-12-01

344

Vegetation canopy PAR absorptance and the normalized difference vegetation index - An assessment using the SAIL model  

NASA Technical Reports Server (NTRS)

Relationships are studied between the normalized-difference vegetation index (NDVI) and absorbed photosynthetically active radiation (APAR) in a vegetation canopy. The SAIL model of bidirectional canopy radiative transfer is employed to compare NDVI measurements that are instantaneous with diurnally integrated canopy APAR capacity. The NDVI measurements - taken at solar-zenith angles of more than 60 deg and sensor views of less than 40 deg from nadir - give stable near-linear estimates of diurnal APAR capacity. Discrepancies in the relations between APAR and NDVI are associated with variations in the optical properties of the canopy and with background spectral reflectance. The results are significant for the practical use of these remote sensing techniques but suggest that instantaneous observations can be used to characterize the diurnally integrated APAR in vegetation canopies.

Goward, Samuel N.; Huemmrich, Karl F.

1992-01-01

345

Availability of arsenic, copper, lead, thallium, and zinc to various vegetables grown in slag-contaminated soils.  

PubMed

To anticipate a possible hazard resulting from the plant uptake of metals from slag-contaminated soils, it is useful to study whether vegetables exist that are able to mobilize a given metal in the slag to a larger proportion than in an uncontaminated control soil. For this purpose, we studied the soil to plant transfer of arsenic, copper, lead, thallium, and zinc by the vegetables bean (Phaseolus vulgaris L. 'dwarf bean Modus'), kohlrabi (Brassica oleracea var. gongylodes L.), mangold (Beta vulgaris var. macrorhiza ), lettuce (Lactuca sativa L. 'American gathering brown'), carrot (Daucus carota L. 'Rotin', 'Sperlings's'), and celery [Apium graveiolus var. dulce (Mill.) Pers.] from a control soil (Ap horizon of a Entisol) and from a contaminated soil (1:1 soil-slag mixtures). Two types of slags were used: an iron-rich residue from pyrite (FeS2) roasting and a residue from coal firing. The metal concentrations in the slags, soils, and plants were used to calculate for each metal and soil-slag mixture the plant-soil fractional concentration ratio (CRfractional,slag), that is, the concentration ratio of the metal that results only from the slag in the soil. With the exception of TI, the resulting values obtained for this quantity for As, Cu, Pb, and Zn and for all vegetables were significantly smaller than the corresponding plant-soil concentration ratios (CRcontrol soil) for the uncontaminated soil. The results demonstrate quantitatively that the ability of a plant to accumulate a given metal as observed for a control soil might not exist for a soil-slag mixture, and vice versa. PMID:11401283

Bunzl, K; Trautmannsheimer, M; Schramel, P; Reifenhäuser, W

2001-01-01

346

Simulating the effects of soil organic nitrogen and grazing on arctic tundra vegetation dynamics on the Yamal Peninsula, Russia  

NASA Astrophysics Data System (ADS)

Sustainability of tundra vegetation under changing climate on the Yamal Peninsula, northwestern Siberia, home to the world’s largest area of reindeer husbandry, is of crucial importance to the local native community. An integrated investigation is needed for better understanding of the effects of soils, climate change and grazing on tundra vegetation in the Yamal region. In this study we applied a nutrient-based plant community model (ArcVeg) to evaluate how two factors (soil organic nitrogen [SON] levels and grazing) interact to affect tundra responses to climate warming across a latitudinal climatic gradient on the Yamal Peninsula. Model simulations were driven by field-collected soil data and expected grazing patterns along the Yamal Arctic Transect (YAT), within bioclimate subzones C (High Arctic), D (northern Low Arctic) and E (southern Low Arctic). Plant biomass and NPP (net primary productivity) were significantly increased with warmer bioclimate subzones, greater soil nutrient levels and temporal climate warming, while they declined with higher grazing frequency. Temporal climate warming of 2 °C caused an increase of 665 g/m2 in total biomass at the high SON site in subzone E, while only 298 g/m2 in the low SON site. When grazing frequency was also increased, total biomass increased by only 369 g/m2 in the high SON site in contrast to 184 g/m2 in the low SON site in subzone E. When comparing low grazing to high grazing effects on soil organic nitrogen pools over time (Figure 1), higher grazing frequency led to either slower SON accumulation rates or more rapid SON depletion rates. Warming accentuated these differences caused by grazing, suggesting the interaction between grazing and warming may yield greater differences in SON levels across sites. Our results suggest that low SON and grazing may limit plant response to climate change. Interactions among bioclimate subzones, soils, grazing and warming significantly affect plant biomass and productivity in the arctic tundra and should not be ignored in regional scale studies.

Yu, Q.; Epstein, H. E.; Walker, D. A.

2009-12-01

347

Land surface phenologies viewed in the middle infrared: seasonal contrasts between vegetation, soils, and impervious surfaces  

NASA Astrophysics Data System (ADS)

The middle infrared (MIR) region of the electromagnetic spectrum spans 3-5 microns. It is the mixing zone between reflected sunlight and emitted earthlight in roughly equal proportions. This region has received very little attention in terrestrial remote sensing. Yet the MIR merits exploration of how it could be used for monitoring land surface phenologies (LSP) and seasonalities due to five characteristics. First, green vegetation is MIR-dark, reflecting just 2-5% of the incident radiation. Second, soils are MIR-bright, reflecting up to one-third of the incident radiation. Third, impervious surfaces, such as concretes, asphalts, and other building and paving materials are also MIR-bright. Fourth, the resulting seasonal contrast in MIR between vegetated and non-vegetated surfaces lets urbanized areas emerge from the vegetated landscape. Fifth, MIR wavelengths penetrate anthropogenic haze and smoke because the particle radii are smaller. Here we use MODIS (MYD02) image time series to illustrate the temporal progressions of MIR at various wavelengths and how they compare to and diverge from the more familiar NDVI and derived LSP metrics.IR portrait of the USA east of W98: maximum value composite of Aqua MODIS MIR band 23 during DOY 219-233 of 2010.

Henebry, G. M.; Krehbiel, C.; Kovalskyy, V.

2012-12-01

348

The response of Arctic vegetation and soils following an unusually severe tundra fire.  

PubMed

Fire causes dramatic short-term changes in vegetation and ecosystem function, and may promote rapid vegetation change by creating recruitment opportunities. Climate warming likely will increase the frequency of wildfire in the Arctic, where it is not common now. In 2007, the unusually severe Anaktuvuk River fire burned 1039 km(2) of tundra on Alaska's North Slope. Four years later, we harvested plant biomass and soils across a gradient of burn severity, to assess recovery. In burned areas, above-ground net primary productivity of vascular plants equalled that in unburned areas, though total live biomass was less. Graminoid biomass had recovered to unburned levels, but shrubs had not. Virtually all vascular plant biomass had resprouted from surviving underground parts; no non-native species were seen. However, bryophytes were mostly disturbance-adapted species, and non-vascular biomass had recovered less than vascular plant biomass. Soil nitrogen availability did not differ between burned and unburned sites. Graminoids showed allocation changes consistent with nitrogen stress. These patterns are similar to those seen following other, smaller tundra fires. Soil nitrogen limitation and the persistence of resprouters will likely lead to recovery of mixed shrub-sedge tussock tundra, unless permafrost thaws, as climate warms, more extensively than has yet occurred. PMID:23836794

Bret-Harte, M Syndonia; Mack, Michelle C; Shaver, Gaius R; Huebner, Diane C; Johnston, Miriam; Mojica, Camilo A; Pizano, Camila; Reiskind, Julia A

2013-08-19

349

[Change characteristics of soil available nitrogen and phosphorus and heavy metal contents after long-term cultivation of vegetables].  

PubMed

Soil samples were collected from three vegetable fields under different years of cultivation in Changsha suburbs of Hunan Province, South-central China to study the accumulation characteristics, risks, and sources of soil available nitrogen and phosphorus and heavy metals in the fields. With the increasing year of vegetable cultivation, the soil NO3(-)-N, Olsen-P, and heavy metals contents in the fields increased significantly. The average contents of soil NO3(-)-N, Olsen-P, and Cd in the vegetable fields having been cultivated for 1-2 years in Ningxiang County, 10-15 years in Changsha County, and 30 years in Kaifu District were 21.1, 31.9 and 0.33 mg x kg(-1), 42.0, 146.9 and 0.52 mg x kg(-1), and 49.5, 219.9 and 1.40 mg x kg(-1), respectively. The cumulative index (CI) of soil heavy metals generally followed the sequence of Cd > Cu > Pb > Ni > Zn. Principal component analysis and cluster analysis showed that compared with soil NH4 OAc-extracted potassium, pH, organic matter and NH4(+)-N, that were dominated by natural factors, the soil Olsen-P and NO3(-)-N had the similar accumulation characteristics with the soil heavy metals, being mainly controlled by fertilization. It was considered that the soil environment and health quality of the vegetable fields in Changsha suburbs were not optimistic. The longer the cultivation year of vegetables, the more the soil NO3(-)-N, Olsen-P, and heavy metals accumulated in the fields. The accumulation of these elements in the fields could be primarily due to the long-term fertilization. PMID:22303670

Quan, Zhi; Wu, Jin-Shui; Wei, Wen-Xue; Qin, Hong-Ling; Zhu, Yi-Jun; Liu, Xin-Liang; Shu, Rong-Bo; Li, Ming-De

2011-11-01

350

? 13C values of soil organic carbon and their use in documenting vegetation change in a subtropical savanna ecosystem  

Microsoft Academic Search

Plants with C3, C4, and CAM photosynthesis have unique ?13C values which are not altered significantly during decomposition and soil organic matter formation. Consequently, ?13C values of soil organic carbon reflect the relative contribution of plant species with C3, C4, and CAM photosynthetic pathways to community net primary productivity, and have been utilized to document vegetation change, to quantify soil

Thomas W Boutton; Steven R Archer; Andrew J Midwood; Stephen F Zitzer; Roland Bol

1998-01-01

351

Numerical modeling of diazinon transport through inter-row vegetative filter strips.  

PubMed

A numerical simulation model of pesticide runoff through vegetative filer strips (PRVFS) was developed as a tool for investigating the effects of pesticide transport mechanisms on VFS design in dormant-sprayed orchard. The PRVFS model was developed applying existing theories such as kinematic wave theory and mixing zone theory for pesticide transport in the bare soil area. For VFS area, the model performs flow routing by simple mass accounting in sequential segments and the pesticide mass balance by considering pesticide washoff and adsorption processes on the leaf, vegetative litter, root zone and soil. Model sensitivity analysis indicated that pesticide transfer from surface soil to overland flow and pesticide washoff from the VFS were important mechanisms affecting diazinon transport. The VFS cover ratio and rainfall intensity can be important design parameters for controlling diazinon runoff using inter-row VFS in orchard. The PRVFS model was validated using micro-ecosystem simulation of diazinon transport for 0, 50 and 100% VFS cover conditions. The PRVFS model is shown to be a beneficial tool for evaluating and analyzing possible best management practices for controlling offsite runoff of dormant-sprayed diazinon in orchards during the rainy season. PMID:14550658

Watanabe, Hirozumi; Grismer, Mark E

2003-10-01

352

Vegetation cover in a warmer world simulated using a dynamic global vegetation model for the Mid-Pliocene  

Microsoft Academic Search

In this study we employ the TRIFFID (Top-down Representation of Interactive Flora and Foliage Including Dynamics) Dynamic Global Vegetation Model (DGVM) and the Hadley Centre Atmospheric General Circulation Model version 3 (HadAM3 GCM) to investigate vegetation distributions and climate–vegetation feedbacks during the Mid-Pliocene, and examine the implications of these results for the origins of hominid bipedalism. The TRIFFID model outputs

Alan M. Haywood; Paul J. Valdes

2006-01-01

353

Stochastic modeling of soil salinity  

NASA Astrophysics Data System (ADS)

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

Suweis, S.; Rinaldo, A.; Van der Zee, S. E. A. T. M.; Daly, E.; Maritan, A.; Porporato, A.

2010-04-01

354

Modeling the interaction between flow and highly flexible aquatic vegetation  

NASA Astrophysics Data System (ADS)

Aquatic vegetation has an important role in estuaries and rivers by acting as bed stabilizer, filter, food source, and nursing area. However, macrophyte populations worldwide are under high anthropogenic pressure. Protection and restoration efforts will benefit from more insight into the interaction between vegetation, currents, waves, and sediment transport. Most aquatic plants are very flexible, implying that their shape and hence their drag and turbulence production depend on the flow conditions. We have developed a numerical simulation model that describes this dynamic interaction between very flexible vegetation and a time-varying flow, using the sea grass Zostera marina as an example. The model consists of two parts: an existing 1DV k-? turbulence model simulating the flow combined with a new model simulating the bending of the plants, based on a force balance that takes account of both vegetation position and buoyancy. We validated this model using observations of positions of flexible plastic strips and of the forces they are subjected to, as well as hydrodynamic measurements. The model predicts important properties like the forces on plants, flow velocity profiles, and turbulence characteristics well. Although the validation data are limited, the results are sufficiently encouraging to consider our model to be of generic value in studying flow processes in fields of flexible vegetation.

Dijkstra, J. T.; Uittenbogaard, R. E.

2010-12-01

355

Ecological restoration and recovery in the wind-blown sand hazard areas of northern China: relationship between soil water and carrying capacity for vegetation in the Tengger Desert.  

PubMed

The main prevention and control area for wind-blown sand hazards in northern China is about 320000 km(2) in size and includes sandlands to the east of the Helan Mountain and sandy deserts and desert-steppe transitional regions to the west of the Helan Mountain. Vegetation recovery and restoration is an important and effective approach for constraining wind-blown sand hazards in these areas. After more than 50 years of long-term ecological studies in the Shapotou region of the Tengger Desert, we found that revegetation changed the hydrological processes of the original sand dune system through the utilization and space-time redistribution of soil water. The spatiotemporal dynamics of soil water was significantly related to the dynamics of the replanted vegetation for a given regional precipitation condition. The long-term changes in hydrologic