Document: XIA-3-34-49

Elevated CO₂ effects on plant respiration: Empirical and meta-analytical results.

WANG, X.* ^1,2 and P.S.CURTIS ¹

The Ohio State University, Columbus, OH 43210 ¹
Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964 ²

Abstract:
We studied the effects of elevated CO₂ and soil N on leaf and stem dark respiration (Rd) of Populus tremuloides in 1995 and 1996. Overall, area-based leaf Rd (Rd_a) was significantly higher at elevated than ambient CO₂, while mass-based leaf Rd (Rd_m) was higher for high-N soil grown trees than for low-N soil grown trees, regardless of CO₂ concentration. However, no CO₂ or soil N effect was observed for leaf Rd_aor leaf Rd_m for a given sampling date. In order to resolve some inconsistencies in the literature regarding elevated CO₂ effects on leaf Rd, we used meta-analysis to quantitatively summarize 45 leaf Rd_a and 44 leaf Rd_m observations from independent studies on 33 species. Our analysis showed that across all studies, leaf Rd_m was significantly reduced (-18%, P < 0.05), while leaf Rd_a was marginally increased (+8%, P < 0.15) under elevated CO₂. There were significant differences among categorical groups in CO₂ effect on leaf Rd_a and Rd_m. For example, leaf Rd_a of herbaceous species increased 28%, but leaf Rd_a of woody species remained unchanged under elevated CO₂. Plants exposed to elevated CO₂ for < 60 days had significantly higher leaf Rd_a at elevated compared to ambient CO₂, while plants exposed to elevated CO₂ for longer period of time showed no response. The magnitude of reduction in leaf Rd_m for plants exposed to elevated CO₂ for > 100 days was significantly greater than that for plants exposed to elevated CO₂ for < 100 days. Our empirical study of P. tremuloides and meta-analysis of published results demonstrated the strong dependency of Rd responses to elevated CO₂ on experimental conditions. Our analysis suggest that total leaf Rd will likely increase in a higher CO₂ environment because of greater leaf area and marginally higher leaf Rd_a as well as proportionally greater leaf biomass increase than leaf Rd_m reduction at elevated CO₂.

Keywords: leaf dark respiration, meta-analysis, Populus tremuloides, soil N, stem respiration

This abstract is being presented at: 10:30 AM in session:
Poster Session #18: Elevated CO₂.