HR: 0800h
AN: B11D-0773    [Abstracts]
TI: Long-Term Influence of Wildfire on Greenhouse Gas Fluxes in Southwestern United States Ponderosa Pine Forest Soils
AU: * Sullivan, B W
EM: bws34@nau.edu
AF: School of Forestry, Northern Arizona University, P.O. Box 15018, Flagstaff, AZ 86011, United States
AU: Kolb, T
EM: tom.kolb@nau.edu
AF: School of Forestry, Northern Arizona University, P.O. Box 15018, Flagstaff, AZ 86011, United States
AU: Hart, S
EM: steve.hart@nau.edu
AF: School of Forestry, Northern Arizona University, P.O. Box 15018, Flagstaff, AZ 86011, United States
AU: Dore, S
EM: sabina.dore@nau.edu
AF: School of Forestry, Northern Arizona University, P.O. Box 15018, Flagstaff, AZ 86011, United States
AU: Montes-Helu, M
EM: mario.montes-helu@nau.edu
AF: School of Forestry, Northern Arizona University, P.O. Box 15018, Flagstaff, AZ 86011, United States
AB: The southwestern United States is home to the largest contiguous ponderosa pine forest in the world. Climate change and historical fire suppression have placed this forest at risk of stand-replacing wildfire. Ponderosa pine forest soils emit carbon dioxide (CO₂) and consume methane (CH₄) by biological oxidation. This study addresses how fire effects the source and sink strength of ponderosa pine forest soil. Fluxes of CO₂ and CH₄ were measured simultaneously in a dense unburned forest and a forest that experienced a high- severity fire 10 years previously using a static chamber technique and gas chromatography. We hypothesized that wildfire would reduce CO₂ efflux due to a reduction in respiring belowground plant biomass and would increase CH₄ consumption due to increased substrate diffusion into the soil. Our results supported these hypotheses. Additionally, CO₂ efflux responds differently to changes in soil water content and soil temperature at the two sites, and models of the two environmental drivers produce significantly different results between sites. Ten years after fire, soil CO₂ efflux is still depressed when compared to a dense forest; however, a reduction in net ecosystem production causes the burned site to be a net source to the atmosphere. The greater CH₄ sink at the burned site does not offset the annual source of CO₂ to the atmosphere. Wildfire in Southwestern ponderosa pine forests has lasting impacts on soil gas fluxes.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0428 Carbon cycling (4806)
DE: 0486 Soils/pedology (1865)
DE: 0490 Trace gases
SC: Biogeosciences [B]
MN: 2007 Fall Meeting