Thermal acclimation of leaf dark respiration of Larix gmelinii: A latitudinal transplant experiment.

The response of tree leaf dark respiration (R) to temperature change is important in modeling and predicting forest carbon (C) cycling under climate change, but it has rarely been investigated in nature. We conducted a field experiment by transplanting the trees of Larix gmelinii - the dominant tree species in Chinese boreal forests from four latitudinal sites to a common garden near the warm border of its range. Our objective was to explore thermal acclimation of R and the underlying mechanisms by comparing the temperature-response curves of R and related leaf traits both in the common garden and at the original sites. We found that warming significantly decreased R and its temperature sensitivity (Q), which changed across the growing season and were correlated with the mean annual temperature of the original sites, reflecting a combination of both short- and long-term respiratory acclimation to warming. The trees from the southern sites tended to have higher thermal acclimation of R and lower Q than that from the northern sites. R and Q were highly correlated with the concentrations of leaf nitrogen and soluble sugars, which may be used as proxies for assessing thermal acclimation of respiration. Considering both short- and long-term thermal acclimation of R likely improves the prediction of forest C cycling in response to climate change.