The contribution of respiration in tree stems to the Dole Effect
- 1The Institute of Earth Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
- 2Department of Biogeochemical Processes, Max-Planck Institute for Biogeochemistry, Jena, Germany
- 3Ecology and Evolutionary Biology, Tulane University, 400 Lindy Boggs, New Orleans, LA, USA
- 4Universidad Nacional de la Amazonía Peruana, Facultad de Ciencias Forestales, Iquitos, Peru
- 5Lawrence Berkeley National Laboratory, Climate Sciences Department, Berkeley, CA, USA
Abstract. Understanding the variability and the current value of the Dole Effect, which has been used to infer past changes in biospheric productivity, requires accurate information on the isotopic discrimination associated with respiratory oxygen consumption in each of the biosphere components. Respiration in tree stems is an important component of the land carbon cycle. Here we measured, for the first time, the discrimination associated with tree stem oxygen uptake. The measurements included tropical forest trees, which are major contributors to the global fluxes of carbon and oxygen. We found discrimination in the range of 12.6–21.5‰, indicating both diffusion limitation, resulting in O2 discrimination values below 20‰, and alternative oxidase respiration, which resulted in discrimination values greater than 20‰. Discrimination varied seasonally, between and within tree species. Calculations based on these results show that variability in woody plants discrimination can result in significant variations in the global Dole Effect.