HR: 0830h
AN: B11D-0715    [PDF]
TI: Impacts of 130 years of grazing on ecosystem carbon dynamics in the subalpine zone of the Wasatch Plateau
AU: * Gill, R A
EM: rgill@wsu.edu
AF: Washington State University, Program in Environmental Science Box 6404430, Pullman, WA 99164 United States
AB: Intensive grazing by domestic livestock likely began in the subalpine region of the Wasatch Plateau by 1870, and has been a continuous disturbance since then. Eight sites within the Great Basin Experimental Range were identified, with each site containing an area that has been protected from livestock for 80-90 years and a continuously grazed area. I specifically evaluated the impacts of long-term protection from grazing on soil C dynamics, N-availability, and aboveground net primary production. I found that grazing leads to an accumulation of actively cycling soil organic matter (SOM); isotopic evidence suggests that the accumulation of active SOM may be due to lower soil moisture in long-term grazed areas compared to protected areas. While there is higher labile SOM C in grazed areas than in protected areas, in situ soil respiration rates were significantly higher in protected areas. This evidence of an environmental constraint on decomposition in grazed areas indicates that lower primary production in grazed sites is being offset by lower decomposition rates, with total ecosystem C storage remaining nearly unchanged between grazed and ungrazed plots. However, it does suggest that historically grazed areas have a larger pool of potentially mineralizable C that could be lost from this system if these subalpine areas become warmer and wetter with climate change.
DE: 0400 Biogeosciences
DE: 4805 Biogeochemical cycles (1615)
SC: Biogeosciences [B]
MN: 2003 Fall Meeting