© 1996 Heron Publishing—Victoria, Canada
Correlations between stable carbon-isotope abundance and hydraulic conductivity in Douglas-fir across a climate gradient in
Oregon, USA
Jeanne A. Panek (1, 2)
1. Department of Forest Science, Oregon State University, Corvallis, OR 97331, USA / 2. Environmental Science, Policy and Management, University of California, Berkeley, CA 94720, USA / Received July 21, 1995
Summary
Stomatal conductance in trees is related to both foliar carbon-isotope abundance and stem hydraulic properties. By combining
these relationships, I hypothesized that carbon-isotope abundance in foliage should vary with limitations to water movement
through supporting branches. I sampled Douglas-fir branches (Pseudotsuga menziesii (Mirb.) Franco) from six sites across a climate gradient in Oregon, USA for foliar carbon-isotope abundance and stem hydraulic
properties. I used a forest growth model to quantify climate-induced stomatal limitations, expressed as reduced potential
transpiration, across the gradient. Foliar stable carbon-isotope abundance showed a strong inverse relationship with branch
specific conductivity (hydraulic conductivity per unit functional sapwood area) and leaf-specific conductivity (hydraulic
conductivity per unit leaf area). Foliar stable carbon-isotope abundance was correlated with modeled reductions in potential
transpiration; however, the inclusion of leaf-specific conductivity improved the correlation by more than 30%. Combined, leaf-specific
conductivity and climate-induced stomatal constraints explained 84% of the variation in foliar isotope abundance in 1994 foliage.
This model was confirmed on foliage classes 1990–1993.
Keywords:
cavitation, climate stress, leaf-specific conductivity, stomatal conductance, transpiration.
