Tree-line dynamics in relation to climate variability in the Shennongjia Mountains, central China

Subalpine tree lines are particularly sensitive to climate variability. In this study, tree-ring chronologies and age structure of the subalpine fir Abies fargesii Franch. are developed to examine subalpine tree-line dynamics in relation to climate variability on the northern and southern aspects of the Shennongjia Mountains in central China. Response function analysis shows that radial growth is significantly positively correlated with temperatures during the previous November and in February and March of the current year on the northern aspect and with temperatures during the previous October and in March, April, and June of the current year on the southern aspect. 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, spring temperatures are the major factor limiting both radial growth and seedling establishment of this subalpine fir species. Radial growth and recruitment of A. fargesii show similar responses to climate variability and provide critical information for assessing the impacts of climate warming on tree-line dynamics, such as an increase in tree density and an upward shift of the altitudinal tree line in this mountainous region of central China.