Document: MAR-3-34-51

Genetic vs. environmental control of respiration in jack pine in contrasting climates.

TJOELKER, M.G.* ¹, J.OLEKSYN ^1,2 and P.B.REICH ¹

University of Minnesota, St. Paul, MN 55108 U.S.A ¹
Institute of Dendrology, Kornik, Poland PL-62-035 Poland ²

Abstract:
Climate warming may alter the carbon balance of plants and ecosystems through increased respiration. However, genetic and environmental sources of variation in respiration across large climate gradients are poorly quantified. We tested the hypothesis that biogeographic variation in respiration is genetic in origin and associated with long-term adaptation of local populations to climate. Moreover, acclimation of respiratory metabolism to thermal environment and its biogeographic variation could mediate respiratory carbon losses. We measured rates of needle maintenance respiration in trees of 20 geographically diverse jack pine (Pinus banksiana) populations (44 to 57 degrees N) grown in common-garden plantations in northwestern Ontario, Minnesota, and Michigan, spanning the climatic range of the species (0.5 to 9.0 degrees C). Respiration rates at a standard temperature tended to track seasonal variation in ambient temperature, increasing in fall and declining in spring and summer, consistent with a thermal-acclimation response. Populations did not differ in their seasonal pattern of temperature acclimation, except in fall when temperatures declined below freezing. Differences in the degree of cold-temperature acclimation among populations were highly correlated with aspects of climate of origin. Populations originating in warmer climates exhibited greater plasticity in respiration rates than did those from colder climates. Overall, these findings demonstrate that thermal acclimation of respiration modulates realized rates of respiratory carbon loss. Genetic differences in respiration rate in jack pine will be less important than ubiquitous temperature acclimation in governing biogeographic variation in respiratory carbon losses with climate warming.

Keywords: Respiration, temperature acclimation, biogeography, climate change

This abstract is being presented at: 3:30 PM in session:
CLIMATE CHANGE