HR: 17:45h
AN: B14B-08    [Abstracts]
TI: Diurnal and Seasonal Variation in the Components of Soil Respiration in a Forest Exposed to Elevated CO2
AU: * Taneva, L
EM: ttanev1@uic.edu
AF: University of Illinois at Chicago, Ecology and Evolution 845 W. Taylor St. M/C 066, Chicago, IL 60607 United States
AU: Gonzalez-Meler, M A
EM: mmeler@uic.edu
AF: University of Illinois at Chicago, Ecology and Evolution 845 W. Taylor St. M/C 066, Chicago, IL 60607 United States
AB: Photosynthetic carbon inputs to the soil are returned to the atmosphere through the process of soil respiration. Soil respiration has many components within the soil system and soil-respired CO₂ can originate in a number of soil organic matter (SOM) pools--from fairly short-lived compartments such as current photosynthate, respired by the root and rhizosphere system, to decomposition of recalcitrant SOM. Because of the large range in turnover times of the carbon pools contributing to soil respiration, the effects of global environmental change on soil respiration components may have important implications for atmospheric CO₂ concentration and, consequently, global climate. Most studies report increased soil respiration rates under elevated CO₂ conditions; however, where the additional respired CO₂ originates within the soil, or how soil respiration components vary diurnally and seasonally, is unclear. At the Duke Forest Free-Air CO₂ Enrichment site (NC), the depleted signature of the fumigation CO₂ in the treatment plots functions as a continuous ecosystem label. This signature is reflected in plant tissues produced since fumigation began in 1996 and can be detected in SOM and soil-respired CO₂. We sampled soil-respired CO₂ diurnally throughout the 2004 growing season and, using its stable carbon isotope composition, we were able to determine the contributions of pre-treatment and post-treatment carbon to soil respiration. Removing the forest floor in a subset of the plots where CO₂ samples were collected allowed further partitioning of soil-respired CO₂ into root/rhizosphere respiration and SOM decomposition. Therefore, we were able to examine diurnal and seasonal variability in the contributions of litter decomposition, root respiration and SOM decomposition to soil respiration in a forest exposed to elevated CO₂ concentration.
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: 0439 Ecosystems, structure and dynamics (4815)
SC: Biogeosciences [B]
MN: Fall Meeting 2005