HR: 1340h
AN: B33E-1093    [Abstracts]
TI: Grazing impacts on soil carbon fractions and soil water dynamics in subalpine ecosystems
AU: * Gill, R A
EM: rgill@wsu.edu
AF: Washington State University, PO Box 64-4430 Program in Environmental Science, Pullman, WA 99164 United States
AB: The mountain lands of the intermountain west are vital to the wellbeing of human communities in the adjacent valleys, providing these communities with water, important summer forage for wildlife and domestic livestock, and possibly the sequestration of anthropogenic carbon. In this work, I build on a 90-year old grazing experiment in mountain meadows on the Wasatch Plateau in central Utah. Long-term grazing significantly reduced aboveground net primary production (ANPP) in all years compared with plots within grazing exclosures, even though these plots were not grazed during the study period. Livestock grazing had no impacts on total soil C or particulate organic matter stocks, although grazing did alter soil C chemistry and soil water dynamics. Grazing significantly increased the proportion of total soil C stocks that were potentially mineralizable in the laboratory. Volumetric soil moisture was consistently higher in ungrazed plots than grazed plots. In addition, there was a 0.5-1% increase in „13C in grazed plots compared to paired ungrazed plots, supporting the conclusion that grazing significantly increases periods of water stress. Because grazing has resulted in an accumulation of easily decomposable organic material, if temperatures warm and summer precipitation increases as is anticipated, these soils may become net sources of carbon to the atmosphere creating a positive feedback between climate change and atmospheric CO2.
DE: 0428 Carbon cycling (4806)
DE: 0476 Plant ecology (1851)
DE: 0486 Soils/pedology (1865)
SC: Biogeosciences [B]
MN: Fall Meeting 2005