HR: 11:50h
AN: B12B-07    [Abstracts]
TI: The diel patterns of soil respiration in four arid California ecosystems: fluxes, sources and hypotheses
AU: * Carbone, M
EM: mcarbone@uci.edu
AF: Dept. of Earth System Science, University of California, Irvine, CA 92697, United States
AU: Trumbore, S
EM: strumbore@uci.edu
AF: Dept. of Earth System Science, University of California, Irvine, CA 92697, United States
AU: Winston, G
EM: gwinston@uci.edu
AF: Dept. of Earth System Science, University of California, Irvine, CA 92697, United States
AU: Serio, D
EM: dserio@uci.edu
AF: Dept. of Earth System Science, University of California, Irvine, CA 92697, United States
AB: Automated measurements provide the high-resolution information that enables us to analyze potential causes for diel variability in soil respiration. These diel patterns are the complex result of biological and physical processes that determine the production and diffusion of CO2 through the soil. We examined the diel patterns of soil respiration from four arid California ecosystems: (1) a pinon-juniper woodland in at the Burns Pinon Ridge Reserve near Joshua Tree National Park, (2) a cold desert shrub community and (3) a perennial grassland near the city of Bishop in the Owens Valley, and (4) a mixed oak-pine forest at the James Reserve in the San Jacinto Mountains. In addition to automated chamber and environmental measurements at these sites, we used isotopic (14C) partitioning techniques to separate the plant and microbial sources contributing to soil respiration at certain time points. Here we present the diel cycles of soil respiration and environmental variables, the source partitioning results, and hypotheses about what processes determine these diel patterns that both span, and are specific to the studied ecosystems. In these systems dominated by Mediterranean or desert climates, we observed that factors like relative humidity can dominate the diel variations in soil respiration for sites with very dry surface litter. At other sites and times of year, diel variation in soil respiration reflects photosynthetic and VPD influence on root respiration. The combination of automated chamber measurements with isotopes provides information useful for separating the plant and heterotrophic control on diel and seasonal soil respiration fluxes.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0428 Carbon cycling (4806)
DE: 0438 Diel, seasonal, and annual cycles (4227)
DE: 0454 Isotopic composition and chemistry (1041, 4870)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting