ABSTRACT 26
Ecosystem respiration in a young ponderosa pine plantation in the Sierra Nevada Mountains, California
Ming Xu, Terry A. Debiase, Ye Qi, Jianwu Tang, Allen Goldstein, and Zhigang Liu
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We estimated the total ecosystem respiration from a ponderosa pine (Pinus ponderosa Dougl. ex Laws.) plantation in the Sierra Nevada Mountains (close to the Blodgett Forest Research Station at UC Berkeley) near Georgetown, California from June to October 1998. We apportioned the ecosystem respiration between heterotrophic, root, stem, and foliage based on relationships for each component that considered microclimate and vegetation characteristics. We measured each respiration component at selected sampling points, and scaled the measurements up to the ecosystem based on modeled relationships. Over the study period, total mean ecosystem respiration (ER) was 5.7 ± 1.3 mmol m-2 s-1 (based on daily mean), comprised of about 67% from soil surface CO2 efflux, 10% from stem and branch (stem+branch) respiration, and 23% from foliage respiration. Shrub leaves contributed about 24% to total foliage respiration, and current-year needles (1998 age class) accounted for 40% of total tree needle respiration. Root respiration accounted for 47% of soil surface CO2 efflux. Ecosystem respiration can be estimated based on daily mean air and soil temperatures through exponential relationships with R2 values of 0.85 and 0.87, respectively. When based on both air and soil temperatures, about 91% of the variation in ER could be explained through a linear regression.
Keywords: Soil surface CO2 efflux, soil respiration, stem respiration, leaf respiration, Q10, microclimate.
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Contact Author: Ming Xu, Department of Environmental Science, Policy, and Management, University of California, 135 Giannini Hall #3312, Berkeley, CA 94720-3312, USA, (510) 643-3263, Fax – (510) 643-5438, email: mingxu@nature.berkeley.edu
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