HR: 0800h
AN: H51C-0375    [Abstracts]
TI: Ecosystem-controlled Erosion in a Loess-mantled Landscape in Eastern Washington
AU: * Walther, S C
EM: swalther@uoregon.edu
AF: University of Oregon, Dept of Geological Sciences 1272 University of Oregon, Eugene, OR 97405 United States
AU: Roering, J J
EM: jroering@uoregon.edu
AF: University of Oregon, Dept of Geological Sciences 1272 University of Oregon, Eugene, OR 97405 United States
AU: Almond, P C
EM: almondp@lincoln.ac.nz
AF: Lincoln University, Agriculture and Life Sciences Division PO Box 84 Lincoln University, Canterbury, 666 New Zealand
AU: Hughes, M
EM: hughesm1@lincoln.ac.nz
AF: Lincoln University, Agriculture and Life Sciences Division PO Box 84 Lincoln University, Canterbury, 666 New Zealand
AB: Vegetation varies with climate so it is important to constrain how different vegetation types affect sediment transport. In forested landscapes, tree throw plays a large role in increased sediment transport relative to shrub and grassland. In this study, we quantify soil transport rates in a coniferous forest using hillslope profiles and tephra abundance. The loess-mantled hillslopes of Robinette Mountain in the Blue Mountains, confining the southeastern edge of the Columbia Plateau in southeast Washington State, USA, have been forested since the Holocene transition. Approximately 6800 years ago, the eruption of Mt. Mazama blanketed the region with tephra. Near the crest of hillslopes of different degrees of convexity, we identified and sampled soils for cryptotephra analysis. The depth of the tephra abundance spike is used as a proxy for erosion/exhumation rate since deposition. The slope dependent sediment transport model suggests that the change in elevation with time (or landscape lowering rate) is proportional to the hillslope curvature, with the constant of proportionality referred to as K (m2 yr-1). Therefore, we surveyed slope morphology for comparison with erosion rate at each site. K generally depends on processes such as soil creep, rain splash, variations in soil moisture (wet/dry) and temperature (freeze/thaw), tree throw, and faunal burrowing/biogenic activity. By estimating the value of K we can relate sediment transport to dominant processes in our forested landscape, such as frequency of tree turnover or faunal burrowing, and determine the spatial variability of erosion rates and sediment delivery using topographic hillslope surveys.
DE: 1815 Erosion
DE: 1824 Geomorphology: general (1625)
DE: 1826 Geomorphology: hillslope (1625)
DE: 1862 Sediment transport (4558)
SC: Hydrology [H]
MN: Fall Meeting 2005