HR: 0800h
AN: H51H-0879    [Abstracts]
TI: Scaling Heterogeneous Soil Hydraulic Properties Using Canopy/Interspace Distributions in a Mojave Desert Ecosystem
AU: * Caldwell, T G
EM: todd.caldwell@dri.edu
AF: Desert Research Instute, 2215 Raggio Parkway, Reno, NV 89512, United States
AU: * Caldwell, T G
EM: todd.caldwell@dri.edu
AF: Univeristy of Nevada, Reno, Graduate Program of Hydrologic Sciences, Reno, NV 89557, United States
AU: Young, M H
EM: michael.young@dri.edu
AF: Desert Research Institute, 755 E. Flamingo Road, Las Vegas, NV 89119, United States
AU: Zhu, J
EM: jianting.zhu@dri.edu
AF: Desert Research Institute, 755 E. Flamingo Road, Las Vegas, NV 89119, United States
AU: Fenstermaker, L F
EM: lynn.fenstermaker@dri.edu
AF: Desert Research Institute, 755 E. Flamingo Road, Las Vegas, NV 89119, United States
AU: McDonald, E V
EM: eric.mcdonald@dri.edu
AF: Desert Research Instute, 2215 Raggio Parkway, Reno, NV 89512, United States
AB: Desert piedmonts are a mosaic of interspersed vegetation and open soil or interspaces. The distribution of perennial plants in arid regions is ultimately tied to available soil moisture. Surface soils in deserts undergo different pedologic processes depending on the proximity to plant canopies. For example, bioturbation and the accumulation of aeolian material and organic matter around plant canopies result in a mound-like formation around perennial plant canopies, whereas interspace areas tend to be microtopographic low points with reduced organic matter. Differences in soil structure and texture in undercanopy and interspace microsites can be significant, thus affecting infiltration, plant available water and ET. In this study, we sought to answer the questions: do soil hydraulic properties vary predictably from the undercanopy to interspace at the plot scale, and if so, how does this heterogeneous parameter field affect large-scale hydrologic processes of a heterogeneous landscape in the Mojave Desert? To answer these questions, a total of four radial transects was run on each of six shrubs (three each of L. tridentata and L. paladin) at the Mojave Global Change Facility (MGCF), located at the Nevada Test Site, USA. The extent of heterogeneity in soil physical and hydraulic properties (texture, bulk density, hydraulic conductivity functions K(h)) was measured across microsites by soil sampling and analysis, and by using up to 7 mini-disk tension infiltrometers (MDTI) spaced at 25-cm increments in linear array across a distance of 150 cm. Significant gradients of soil physical and hydraulic properties were observed from canopy to interspace microsites at 1.2 times the mean mound diameter. Despite a decrease in bulk density and fines under shrub canopies, a consistent trend of increasing K(h) and decreasing Gardner's alpha with increasing radial distance from shrubs was measured. Using the results of observed gradients around canopies, hydraulic property variability, and the large scale vegetation cover and distribution, two different methods of upscaling ( p-norm and site-specific pedotransfer function [PTF]) were compared during simulations of the ecosystem water balance. Results showed that effective K(h) from the p-norm approach resulted in a similar total water balance compared to the PTF method, but partitioning of water to root uptake differed significantly.
DE: 1813 Eco-hydrology
DE: 1839 Hydrologic scaling
DE: 1865 Soils (0486)
DE: 1866 Soil moisture
DE: 1875 Vadose zone
SC: Hydrology [H]
MN: 2007 Fall Meeting