نتایج جستجو برای: soil moisture stress
تعداد نتایج: 635198 فیلتر نتایج به سال:
Spatial and temporal soil moisture dynamics are critically needed to improve the parameterization for hydrological and meteorological modeling processes. This study evaluates the statistical spatial structure of large-scale observed and simulated estimates of soil moisture under pre- and post-precipitation event conditions. This large scale variability is a crucial in calibration and validation...
Soil moisture is a key variable for the water and energy exchanges at the land surface. The determination of soil moisture dynamics from space is one of the most prominent, but also most challenging applications for recent active microwave sensor systems. Since the launch of ENVISAT ASAR, more than 4 years of data is available for the retrieval of soil moisture information. The wide area covera...
The Kalman filter assimilation technique is applied to a simplified soil moisture model for retrieval of the soil moisture profile from near-surface soil moisture measurements. First, the simplified soil moisture model is developed, based on an approximation to the Buckingham–Darcy equation. This model is then used in a 12month one-dimensional field application, with updating at 1-, 5-, 10-, an...
The spatial pattern of soil moisture varies at different scales due to evapo-transpiration and precipitation which are transformed by topography, soil texture, and vegetation. The mapping of soil moisture by remote sensing has several advantages over conventional field measurement techniques especially in the case of heterogeneous landscapes. However, validation of low resolution satellite soil...
s: A combination of field measurements, continuous monitoring, and numerical modeling were used to evaluate soil moisture regimes at four sites across a landscape gradient of the Heihe River Basin (HRB). Recorded data of precipitation, irrigation, and floods were used to build the model, and an optimization technique was employed to calibrate the parameters. Based on the optimized parameters an...
The biodiversity of microbial communities has important implications for the stability and functioning of ecosystem processes. Yet, very little is known about the environmental factors that define the microbial niche and how this influences the composition and activity of microbial communities. In this study, we derived niche parameters from physiological response curves that quantified microbi...
Abiotic global change drivers affect ecosystem structure and function, but how they interact with biotic factors such as invasive plants is understudied. Such interactions may be additive, synergistic, or offsetting, and difficult to predict. We present methods to test the individual and interactive effects of drought and plant invasion on native ecosystems. We coupled a factorial common garden...
BACKGROUND AND AIMS Deciduous trees have a seasonal carbon dioxide exchange pattern that is attributed to changes in leaf biochemical properties. However, it is not known if the pattern in leaf biochemical properties - maximum Rubisco carboxylation (V(cmax)) and electron transport (J(max)) - differ between species. This study explored whether a general pattern of changes in V(cmax), J(max), and...
This research investigates the interannual variability of soil moisture as related to large-scale climate variability and also evaluates the spatial and temporal variability of modeled deep layer (40–140 cm) soil moisture in the Upper Colorado River Basin (UCRB). A three layers hydrological model VIC-3L (Variable Infiltration Capacity Model – 3 layers) was used to generate soil moisture in the ...
Passive microwave sensors have many advantages including the ability to directly measured soil moisture at large spatial scales regardless of weather conditions or time of day. However, microwave-sensed soil moisture’s inevitable limitation is that it cannot describe hydrology at the watershed because its retrieved soil moisture scale is too large. Thus, microwave-sensed soil moisture requires ...
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