Altitudinal variability of climate–tree growth relationships along a consistent slope of Anyemaqen Mountains, northeastern Tibetan Plateau

Abstract

In order to investigate climate–tree growth relationships at different elevations, tree-ring width chronologies of Qilian Juniper ( Sabina przewalskii) were developed from four sampling sites at different elevations of a south-facing slope in the central Anyemaqen Mountains, northeastern Tibetan Plateau. Statistical characteristics of the chronologies indicated most tree-ring parameters decreased with the increase of elevations. Response analysis on the first principal component of all four chronologies indicated 76% of tree growth could be explained by climatic variations. Correlation analysis between chronologies and climate variables indicated there were significant differences in climate–tree growth relationships along the altitudinal gradients. The lower forest border chronology was negatively correlated with monthly mean temperature, except for previous October and current January–March, while the upper forest border chronology had positive correlations with monthly mean temperature, excluding previous September and current April–May. There was a decreasing trend from significantly negative to weakly negative correlations of tree growth with May–June temperature from low to high elevations, and an increasing trend from weakly negative to significantly positive correlations with July temperature. Meanwhile, there were significant positive correlations of prior August–October and current July precipitation with the two low-elevation chronologies. The correlations between tree growth and January–April precipitation varied from negative to positive with the increase of elevations, although there were no significant correlations between precipitation and high-elevation chronologies. Response analysis on all chronologies indicated tree growth was more limited by temperature along the entire slope, while precipitation tends to influence tree growth at some drier or lower-elevation sites.