Differences in growth pattern and response to climate warming between Larix olgensis and Pinus koraiensis in Northeast China are related to their distinctions in xylem hydraulics

Tree-ring analysis provides an effective way to detect complex responses of trees to climate warming and has been extensively used in ecological studies; however, there is often a lack of simultaneous physiological investigations explaining the observed patterns. Here, we paralleled dendroclimatic analyses with hydraulics measurements in co-occurring Larix olgensis and Pinus koraiensis trees along an elevational gradient (low, middle and high) in Northeast China. We aimed to detect potential differences in patterns of growth and responses to climate warming between the two conifer species considering their distinctions in life history strategy and key functional traits and to provide a mechanistic explanation for such differences. Our tree-ring analyses showed that L. olgensis trees exhibited a linear increase in basal area increment at the initial part of lifetime while Korean pine trees usually have a long slow growth period up to several decades at the juvenile stage. Consistent with their contrasts in growth rate, the larch species showed significantly higher hydraulic conductivity and functional traits favoring more efficient carbon gain at the shoot level compared to sympatric Korean pine trees. Results of the dendroclimatological analyses indicate that temperature rather than precipitation is the controlling factor for growth in both species under the current climate regime. Radial growth of both species overall accelerated accompanying the rapid warming since 1990s except a significant decrease in growth for Korean pine trees at the low elevation site, which is likely due to stronger competitions from co-occurring broadleaf trees in the mixed forest environments. In the larch species, the substantially lower degree of response in growth at the low elevation site compared to trees at higher elevations suggests that the drying effect of warming at the low elevation may have to a certain degree offset the beneficial effects of warming on growth of larch trees.