Radial Growth Response of Abies georgei to Climate at the Upper Timberlines in Central Hengduan Mountains, Southwestern China

Climate change has an inevitable impact on tree radial growth, particularly at mountain timeberlines. To understand climate effects on conifer radial growth in the central Hengduan Mountains, and the potential impacts of future climate change on conifer forests, we studied the growth responses to climate variables in Abies georgei, the major tree species of conifer forest in the Hengduan Mountains. We collected tree ring samples from four sites near the timberlines and analyzed the relationship between principle components (PC#1) of four chronologies and climatic variables (monthly mean temperature and monthly total precipitation) by using response function analysis (RFA), redundancy analysis (RDA), and moving interval analysis (MIA). A. georgei growth was affected by both temperature (positive effects) and precipitation (negative effects). Specifically, the radial growth of A. georgei was significantly and positively correlated with current July (by 6.1%) and previous November temperature (by 17.3%) (detected by both RFA and RDA), while precipitation of current June (by 6.6%) and September (by 11.7%) inhibited tree growth (detected by RDA). More rapid warming in the most recent 20 years (1990–2010) clearly enhanced growth responses to July and November temperature, whereas the relationship was weakened for June and September precipitation, according to MIA. Under the climate trend of the study area, if the increasing temperature could offset the negative effects of excessive precipitation, A. georgei radial growth would likely benefit from warming