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A MIXED MODEL ANALYSIS OF SOIL CO2 EFFLUX AND NIGHT-TIME RESPIRATION RESPONSES TO ELEVATED CO2 AND TEMPERATURE
LEE, E. A MIXED MODEL ANALYSIS OF SOIL CO2 EFFLUX AND NIGHT-TIME RESPIRATION RESPONSES TO ELEVATED CO2 AND TEMPERATURE. Presented at Department of Statistics, OSU, seminar, Corvallis, OR, January 23, 2006.
Abstract: We investigated the effects of elevated soil temperature and atmospheric CO2 on soil CO2 efflux and system respiration responses. The study was conducted in sun-lit controlled-environment chambers using two-year-old Douglas-fir seedlings grown in reconstructed litter-soil systems. The study used a 2 x 2 factorial design with two soil temperature levels (ambient and elevated) and two atmospheric CO2 levels (ambient and elevated). A completely randomized design was used to allocate three replicate environmental chambers for each of the four treatment combinations. Soil CO2 efflux was measured every four weeks for 18 months during the third and fourth years of study. In addition, a second monitoring system continuously measured all CO2 fluxes into and out of the chambers and recorded CO2 exchange rates for 30-minute intervals. For each day, night-time respiration was calculated as the daily average CO2 exchange rate during the night (10 PM to 3 AM). We hypothesized that (1)elevated temperature would stimulate CO2 exchange rates and (2) elevated atmospheric CO2 would also stimulate exchange rates with stimulation being greater at higher temperatures. The effects of CO2 and temperature on monthly soil CO2 efflux and daily respiration rates were tested using a mixed model approach with covariates for soil moisture and seasonality.
Record Details:Record Type: DOCUMENT (PRESENTATION/ABSTRACT)
Organization:U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
NATIONAL HEALTH AND ENVIRONMENTAL EFFECTS RESEARCH LABORATORY
WESTERN ECOLOGY DIVISION
RISK CHARACTERIZATION BRANCH