Monday, November 5, 2007
98-7
Long-Term Effects of Grazing and Climatic Conditions on Carbon Sequesteration and Microbial Dynamics on Rangelands.
Gerald E. Schuman1, George F. Vance2, Justin D. Derner1, Lachlan J. Ingram2, Peter D. Stahl2, and Amitava Chatterjee3. (1) Agricultural Research Service, 11610 Blazer Road, Cheyenne, WY 82009, (2) Renewable Resources, University of Wyoming, 1000 E. University Ave., Laramie, WY 82071, (3) School of Natural Resources, Carbon Management and Sequestration Center, The Ohio State University, Room# 414 A, Kottman Hall, 2021 Coffey Rd, Columbus, OH 43210
Grazing at light to heavy stocking rates in northern mixed-grass rangeland increased C sequestration after 12 years (1982-1993); however, drought conditions 7 of the following 10 years (1993-2003) resulted in a 30% loss of the sequestered C where grazing was heavy with concurrent shifts in the plant community from cool-season to warm-season perennial grasses. Nitrogen mineralization, microbial biomass and microbial respiration were greater with light or no grazing compared to heavy grazing in 2003. In addition, phospholipids fatty acid analysis indicated soil microbial community structure was influenced by grazing. Amounts of annual precipitation were average or above from 2003-2005 with soil sampling conducted in early spring 2006 to assess short-term responses of C sequestration following these 3 years of average or better precipitation following drought. Grazing management can increase C sequestration in this rangeland ecosystem, but the dynamics of C sequestration are also dependent on precipitation amount and distribution.