HR: 1340h
AN: B33E-1675    [Abstracts]
TI: Relating Soil CO₂ Efflux and Root Respiration to Climate and Canopy Gas Exchange in Mature Ponderosa Pine
AU: * Irvine, J
EM: james.irvine@oregonstate.edu
AF: Oregon State University, College of Forestry Dept Forest Science, Corvallis, OR 97331, United States
AU: Law, B E
AF: Oregon State University, College of Forestry Dept Forest Science, Corvallis, OR 97331, United States
AU: Martin, J G
AF: Oregon State University, College of Forestry Dept Forest Science, Corvallis, OR 97331, United States
AU: Vickers, D
AF: Oregon State University, College of Oceanic and Atmospheric Sciences, Corvallis, OR 97331, United States
AB: Soil respiration (F_s) is the second largest flux of carbon in terrestrial ecosystems and will play a key role during global climate change, yet our understanding of factors that control F_s are notably weak. We examined a six year automated chamber based record of F_s and the underlying components at a seasonally drought stressed pine forest in relation to climate and canopy gas exchange. Inter-annual variability of F_s was large (CV=17%) ranging between 612 and 1039 gC m^-2y^-1. On average 76 % of the variation of daily mean F_s could be quantified using a simple empirical model with year specific basal respiration rate, that was a linear function of above ground annual net primary productivity (ANPP), modulated by a common response to soil temperature and moisture. Using the natural range of climate variability across the 6 yrs to determine the degree of control on F_s by temperature and soil moisture; seasonal total F_s was twice as sensitive to soil moisture variability during the summer months compared to temperature variability during the same period and almost insensitive to the natural range of variability in spring temperature. Soil autotrophic respiration showed a strong seasonal pattern that was tightly linearly correlated with tree transpiration measured using sapflow techniques (r²=0.87) and gross ecosystem productivity (r²=0.81) as determined using the eddy flux approach. Diel patterns of soil autotrophic and heterotrophic respiration were consistent with location of carbon source in the soil profile and a simple diffusion model. Collectively the results suggest future models of soil respiration should consider the inclusion of canopy processes.
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0428 Carbon cycling (4806)
DE: 0438 Diel, seasonal, and annual cycles (4227)
DE: 1615 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 4805, 4912)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting