Variation of radial growth patterns in trees along three altitudinal transects in north central China.

Fourteen tree-ring width chronologies were developed along three altitudinal gradients for three mountain ranges in arid north central China. The chronology statistics, combined with results of a rotated principle component analysis (RPCA), suggest that physiological gradients play a more important role in determining tree-growth patterns than altitudinal gradients. As indicated by climate-growth relationships, temperature is mainly related to the low-frequency tree-ring variability, while precipitation is more influential on the high-frequency tree-ring variability. At the low-frequency band, chronologies across species from lower and upper forest limits were generally well correlated, except at the upper site of the Xinglong Mountain. It is plausible that similar temperature-shaped climate-growth relationships in the low-frequency domain may lead to similar growth patterns at this frequency band. Regarding the differing results for the Xinglong Mountain, our interpretation is that the changed growth patterns resulted from the varying climate-growth correlation patterns along the larger altitudinal gradients. The temperature and precipitation limitations for tree growth decrease along the increasing altitudinal gradients.