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We tested the hypothesis that acclimation of foliar dark respiration to CO 2 concentration and temperature is associated with adjustments in leaf structure and chemistry. Populus tremuloides Michx. , Betula papyrifera Marsh. , Larix laricina (Du Roi) K. Koch , Pinus banksiana Lamb., and Picea mariana (Mill.) B.S.P. were grown from seed in combined CO 2 (370 or 580 μ mol mol –1 ) and temperature treatments (18/12, 24/18, or 30/24 °C). Temperature and CO 2 effects were predominately independent. Specific respiration rates partially acclimated to warmer thermal environments through downward adjustment in the intercept, but not Q 10 of the temperature–response functions. Temperature acclimation of respiration was larger for conifers than broad‐leaved species and was associated with pronounced reductions in leaf nitrogen concentrations in conifers at higher growth temperatures. Short‐term increases in CO 2 concentration did not inhibit respiration. Growth in the elevated CO 2 concentration reduced leaf nitrogen and increased non‐structural carbohydrate concentrations. However, for a given nitrogen concentration, respiration was higher in leaves grown in the elevated CO 2 concentration, as rates increased with increasing carbohydrates. Across species and treatments, respiration rates were a function of both leaf nitrogen and carbohydrate concentrations ( R 2 = 0·71, P < 0·0001). Long‐term acclimation of foliar dark respiration to temperature and CO 2 concentration is largely associated with changes in nitrogen and carbohydrate concentrations.
Tjoelker et al. (Thu,) studied this question.