Treeline dynamics and its relation to climate variability in the Qingba Mts, central China

Background/Question/Methods Trees in the subalpine environment, a particularly vulnerable area being the first to reflect climate changes, are most likely to show strong effects of climate variability, and climate change may have caused treeline upward shift in the alpine environment. In this study, tree-ring chronologies and age structure of Abies fargesii are developed to examine subalpine treeline dynamics and its relation to climate variability in the Qingba Mountains of China.

Results/Conclusions Standard correlation functional analysis showed different growth responses of fir trees to climatic variables including temperature and precipitation between north and south aspects in the Qinba Mountains. Also, the importance of temperature increases along the altitudinal gradient. Analysis of age structure distribution displayed a decrease in number of mature fir trees and an increase in number of saplings/seedlings along the altitudinal gradient in both aspects. Fir aplings/seedlings only occur in the treeline environment, and this fir population is significantly younger than that at lower elevations. Recruitment of A. fargesii is positively influenced by temperature in March and April on the northern aspect and in February, March, and May on the southern aspect. Precipitation shows no significant correlation with radial growth or recruitment of A. fargesii on either aspect. Thus, fir trees show different radial growth patterns in response to climatic variability between north and south aspects, and age-class distributions along the altitudinal gradient imply an increase in tree density and upward shift of the treeline in the Qinba Mountains of China.