© 2001 Heron Publishing—Victoria, Canada
Ecosystem respiration in a young ponderosa pine plantation in the Sierra Nevada Mountains, California
Ming Xu (1), Terry A. DeBiase (1), Ye Qi (1), Allen Goldstein (1) and Zhigang Liu (2)
1. Department of Environmental Science, Policy, and Management, University of California, 207 Giannini Hall, Berkeley, CA 94720-3310,
USA / 2. Institute for Tropical Ecosystem Studies, University of Puerto Rico, PO Box 363682, San Juan, PR 00936, USA / Received November 1, 2000
Summary
We estimated total ecosystem respiration from a ponderosa pine (Pinus ponderosa Dougl. ex Laws.) plantation in the Sierra Nevada Mountains near Georgetown, California, from June to October, 1998. We apportioned
ecosystem respiration among 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
was 5.7 ± 1.3 μmol m–2 s–1(based on daily mean), comprising about 67% from soil-surface CO2 efflux, 10% from stem and 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. We conclude that 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 total
ecosystem respiration could be explained by a linear regression.
Keywords:
leaf respiration, microclimate, Q10, soil respiration, soil-surface CO2 efflux, stem respiration.
