Acclimation and adaptation of leaf photosynthesis, respiration and phenology to climate change: A 30-year Larix gmelinii common-garden experiment

Acclimation and adaptation of leaf physiology and phenology to climate change have attracted substantial attention from forest ecology and global change science communities, but partitioning these two components in situ is challenging especially for adult trees. Here, we examined seasonal variations in leaf photosynthesis, respiration and phenology of Dahurian larch (Larix gmelinii) trees that were originated from six provenances and grown in a common garden for 30 years; and we partitioned these variations into genetic adaptation and phenotypic acclimation. Our results showed that both area-based maximum net photosynthetic rate (Pmax-a) and dark respiratory rate (Rd) differed significantly among the provenances, and co-varied with leaf nitrogen concentration and the environmental factors of the seed-source sites, which provides evidence for genetic adaptation of the leaf physiology to climate change. However, the leaf phenology (i.e., leaf unfolding and shedding) of the six provenances converged in the common garden, and was correlated with the local temperature, suggesting phenotypic acclimation of the leaf phenology to local habitat. The provenance differences in the Pmax-a and Rd varied with the growing stages, suggesting that measuring time at different growing stages can affect the comparison of the Pmax-a and Rd among the provenances. The temporal patterns of the Pmax-a, Rd and their correlations with the seasonal changes in the local temperature were indicative of a consistent thermal acclimation, but the magnitude and direction of the acclimation varied with temporal scale and provenance. The trees originated from cold habitats tended to have less thermal acclimation of Pmax-a and Rd to local temperature, implying that the trees from the cold edge of the larch range likely exhibit less responses to climate warming. Collectively, the acclimation and adaptation of the leaf physiology and phenology of Dahurian larch to climate change are of significance in managing and modeling responses of this important species in the Eurasian boreal forests to climate change.