HR: 09:00h
AN: B21C-05    [Abstracts]
TI: Is the pool of soil carbon undergoing decomposition changing with temperature?
AU: * Diochon, A
EM: adiochon@stfx.ca
AF: Environmental Sciences Research Centre, St. Francis Xavier University, 1 West Street, Antigonish , NS B2G2W5, Canada
AU: Kellman, L M
EM: lkellman@stfx.ca
AF: Environmental Sciences Research Centre, St. Francis Xavier University, 1 West Street, Antigonish , NS B2G2W5, Canada
AU: Beltrami, H
EM: hugo@stfx.ca
AF: Environmental Sciences Research Centre, St. Francis Xavier University, 1 West Street, Antigonish , NS B2G2W5, Canada
AB: Forest harvesting alters the structure of the mineral soil organic carbon pool but the response of an altered pool structure to changes in temperature is not well known. A site with more carbon and/or a higher quality carbon pool would, intuitively, produce more CO₂ and, based on kinetic theory, exhibit a lower temperature sensitivity. We identified a set of sites that differ only in their time since harvest and that are separated by no more than 5 km. To examine the temperature dependence of decomposition as a function of carbon quality and quantity, we incubated soils from 6 depth strata in the top 50 cm of mineral soil from each site across the region's annual temperatures range (1 C to 31 C) at constant moisture. The headspace of the incubation chambers was measured weekly for 5 weeks for CO₂ production and δ¹³C after flushing the headspace with CO₂ free air. Rates of respiration indicate multiple temperature optima, and respiration rates and δ¹³C ratios of respired C suggest that the pool of available substrate shifts with temperature. A substrate addition experiment corroborated our findings suggesting that the diversity and structure of the microbial community may be as important as temperature in determining the pool of carbon that is actually available for decomposition.
DE: 0428 Carbon cycling (4806)
DE: 0454 Isotopic composition and chemistry (1041, 4870)
DE: 1615 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 4805, 4912)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting