Rangelands are estimated to cover 30 to 50 percent of the world's land surface and have significant belowground carbon (C) storage potential. Given their geographical extent, many have suggested that even modest changes in C storage via management practices could alter the global C cycle, creating climate change mitigation opportunities. Our objective was to investigate soil organic carbon (SOC) stability across a managed annual grassland, savanna, and oak woodland landscape. We sampled A and AB horizons from 20 soil profiles to assess long-term SOC stabilization pathways using combined physical and chemical SOC laboratory fractionation techniques. We found that although total SOC was positively correlated with woody plant cover, the SOC stabilization mechanisms differed only slightly across this gradient of woody cover (0 to 100 percent)—for all practical purposes, the relative proportions of physically protected C, biochemically protected C, and unprotected C were largely non-responsive to woody cover. Therefore, we found woodland and savanna soil carbon stores were not more resilient to disturbances than grassland carbon stores, and so can be quickly degraded and lost upon removal of woody cover.
soil organic carbon stabilization
Roche, Leslie M.; Chang, James F.; Six, Johan; O'Geen, Anthony T.; Tate, Kenneth W. 2015. Soil organic carbon stability across a Mediterranean oak agroecosystem. In: Standiford, Richard B.; Purcell, Kathryn L., tech. cords. Proceedings of the seventh California oak symposium: managing oak woodlands in a dynamic world. Gen. Tech. Rep. PSW-GTR-251. Berkeley, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: 219-230.