HR: 1330h
AN: H32C-0590    [PDF]
TI: Small scale variations in soil depth affecting the patterns and relationships between soil moisture and transpiration
AU: * Tromp-van Meerveld, H J
EM: ilja.tromp@orst.edu
AF: Department of Forest Engineering, Oregon State University, Peavy 215, Corvallis, OR 97331 United States
AU: Peters, N E
EM: nepeters@usgs.gov
AF: U.S. Geological Survey, 3039 Amwiler Rd., Suite 130, Atlanta, GA 30360 United States
AU: Bond, B J
EM: Barbara.Bond@orst.edu
AF: Department of Forest Science, Oregon State University, 321 Richardson Hall, Corvallis, OR 97331 United States
AU: McDonnell, J J
EM: jeff.mcdonnell@orst.edu
AF: Department of Forest Engineering, Oregon State University, Peavy 215, Corvallis, OR 97331 United States
AB: Relations between the spatial patterns of soil moisture, soil depth, and transpiration and their influence on the hillslope water balance are not well understood. When determining a water balance for a hillslope, small scale variations in soil depth are often ignored. In this study we found that these variations in soil depth can lead to distinct patterns in transpiration rates across a hillslope. We measured soil moisture content at 5-10 cm depth intervals between the soil surface and the soil-bedrock boundary at 64 locations across the trenched hillslope in the Panola Mountain Research Watershed. We related these soil moisture data to transpiration rates measured in 16 trees across the hillslope using 32 constant heat sapflow sensors. Results showed a lack of spatial structure in soil moisture across the hillslope and with depth when the hillslope was in either the wet or the dry state. However, during the short transition period between the wet and dry state soil moisture did become spatially organized with depth and across the hillslope. Variations in soil depth and thus total soil water in the soil profile at the beginning of the growing season caused differences in soil moisture content and transpiration rates between upslope and midslope sections at the end of the summer. In the upslope section, which has shallower soils, transpiration became severely limited by soil moisture while in the midslope section with deeper soils transpiration was not limited by soil moisture. These spatial differences in soil depth, total water available at the beginning of the growing season and soil moisture content during the summer could be responsible for the observed spatial differences in basal area and species distribution between the upslope and midslope sections of the hillslope.
DE: 1818 Evapotranspiration
DE: 1836 Hydrologic budget (1655)
DE: 1851 Plant ecology
DE: 1866 Soil moisture
DE: 1875 Unsaturated zone
SC: Hydrology [H]
MN: 2003 Fall Meeting