Age-dependent radial growth responses of Larix chinensis to climatic factors in Qinling Mountains, northwestern China

Qinling Mountains, located in northwestern China, is the most typical distribution area of temperate coniferous forests, and is also one of the most significant areas affected by global climate change. Several studies have demonstrated that tree physiological characteristics undergoes changes with age. This may cause growth-related climate signals to vary over time. To explore this age-dependent effect, in this study, we tested the consistency of climate-growth responses in tree-ring series from L.chinensis trees of different age classes in relation near the alpine timberline in Qinling Mountains, a total of 240 tree-ring cores were sampled in the Aoshan, second peak of Qinling Mountains. In the concentrated distribution area of the upper limit, L. chinensis was grouped into three age classes: trees younger than 40 years (young age class, YAC), trees of 41-80 years of age (middle age class, MAC) and trees older than 81 years (old age class, OAC). Residual chronologies of the three age classes were built to analyze the climate-growth relationships using correlation and response functions. The results were as follows:1)differing among the three age classes, the chronology of old age class was more sensitive to climate change than the others, which was suitable for dendroclimatological analysis. 2)Response function analyses indicated that early growing season, early spring temperature and spring precipitation were the principal factors limiting its growth in the old age classes. However, there was no significant correlation between young age classes and all climate variables. Overall, the effects of age on the response of tree-ring width of L. chinensis to climate change, and the results of this study confirmed that the climate signal was maximized in older trees. Our study provides some basic data for the rational management of L.chinensis forest in relation near the alpine timberline in Qinling Mountains and the climate reconstruction in the region.