HR: 10:35h
AN: C41D-02 INVITED     [PDF]
TI: Relating Snow Transport to Ecosystem Structure and Function: Lessons from Libby Flats
AU: * Hiemstra, C A
EM: hiemstra@atmos.colostate.edu
AF: Department of Atmospheric Science, Colorado State University, 1371 Campus Delivery, Fort Collins, CO 80523-1371 United States
AU: Reiners, W A
EM: reiners@uwyo.edu
AF: Department of Botany, University of Wyoming, PO Box 3165, Laramie, WY 82071-3165 United States
AB: The effects of variable snow cover on ecosystem structure and function have been well-documented in cold, temperate ecosystems, especially in high-elevation treeline and alpine landscapes where long, windy winters can produce dramatic variations in snow depths over short distances. Additionally, wind directions, snowfall, and resultant snow-distribution patterns are essentially the same year after year, allowing for relatively steady state environmental conditions and ecosystem properties. These chronic and heterogeneous snow-cover patterns have been associated with ecosystem structure (e.g., plant species distributions, soil characteristics) and function (e.g., decomposition, primary production, nutrient cycling, water balance) in systems where winters are long and most precipitation falls as snow. We sought to determine the impacts of a heterogeneous snow distribution on ecosystem properties in a 6.25 km$^{2}$ upper-treeline ecotone, called Libby Flats, in south-central Wyoming. This involved modeling and validating snow accumulation, ablation, and meltwater flow spatially coupled with observations of snow depth and density, soil moisture, soil temperature, plant species composition and cover, biomass, gross decomposition, and gopher activity. Model simulations successfully represented the general spatial patterns of snow redistribution and ablation, but field measurements pointed the way for model improvements. Dominant cover types varied with snow depth, meltwater flow, and soil temperature. Decomposition rates changed with soil moisture, soil temperature, snow depth, and length of time covered by snow. Gopher activity was inversely related to soil moisture and positively related to soil depth, soil temperature, snow water equivalent, and graminoid biomass. The role of snow in this landscape is best understood as a function of transport. Transport of snow and snow meltwater play distinctive roles in the spatial patterns of cover within the Libby Flats landscape. Snow is transported to areas where wind speeds are reduced, and once snowmelt ensues during the spring and summer, water is absorbed into the soil, evaporated, or transported downslope. These concatenated factors involving water movement produce temporally shifting gradients of available moisture and site conditions (e.g., soil temperature and moisture) that influence, and are influenced by, ecosystem structure and function.
DE: 1851 Plant ecology
DE: 1863 Snow and ice (1827)
DE: 1866 Soil moisture
DE: 3322 Land/atmosphere interactions
SC: Cryosphere [C]
MN: 2003 Fall Meeting