HR: 0800h
AN: B41B-0112    [Abstracts]
TI: Soil Carbon and Nitrogen Dynamics in Fire-Suppressed, Wildfire-Burned, and Prescribe-Burned Chaparral in the Sierra Nevada Foothills
AU: * Norton, J B
EM: jbnorton@ucdavis.edu
AF: University of California Cooperative Extension, County of Tuolumne 2 S. Green Street, Sonora, CA 95370 United States
AU: Horwath, W R
EM: wrhorwath@ucdavis.edu
AF: University of California Department of Land, Air, & Water Resources, One Shields Avenue, Davis, CA 95616 United States
AU: Norton, U
EM: urszula@goldrush.com
AF: University of California Department of Land, Air, & Water Resources, One Shields Avenue, Davis, CA 95616 United States
AB: Chaparral shrublands cover 13 percent of California's land area and are very dynamic, productive, and flammable. While chaparral supports potentially destructive stand-replacing fires that provide opportunity for rapid, large-scale vegetation manipulation for range management and fire hazard reduction, there has been little investigative work describing soil organic matter dynamics in chaparral. We report findings of research on vegetation cover and soil organic matter fractionation in passive, slow, and rapidly cycling pools under different fire history regimes and soil types in chamise-manzanita-toyon chaparral of the Sierra Nevada Foothills. We used detailed fire history overlays and soil-vegetation maps to identify five fire history scenarios: 1) long-term fire-suppressed; 2) 20-year wildfire frequency (1950-1972-1992); 3) four-year wildfire frequency (1997-2001); 4) one-time wildfire (2001); and 5) prescribed reburn (2001-2005-2006) where the management goal is to type convert dense, resprouting shrub cover to a grass-shrub mosaic in a strategic fire hazard reduction zone. We replicated these sampling areas on three soil types ubiquitous to Sierra Nevada Foothills chaparral: soil derived from residuum of granite, basic igneous and metamorphic rocks, and serpentine. Vegetation cover analysis shows that the four-year fire recurrence interval has significantly lower shrub cover and higher annual grass cover compared to all the other treatments. Results of vegetation cover analysis, soil organic carbon fractionation, estimates of microbially available carbon, and indices of potentially mineralizable nitrogen will be presented.
DE: 1615 Biogeochemical processes (4805)
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting