Response of radial growth of three conifer trees to climate change at their upper distribution limits in Potatso National Park, Shangri-La, southwestern China
In order to detect the response of tree growth to climate change in the northwestern Yunnan Plateau, we used residual chronologies of three major conifers, i.e. Picea brachytyla, Larix potaninii and Abies georgei at their upper distribution limits in Potatso National Park, to study the characteristics of the residual chronologies and the relationships between radial growth and climatic factors (temperature and precipitation). We aimed to find out the main climatic factors affecting tree growth in the area and to detect differences of growth responses to climates among the studied species. The results showed that: 1) The climatic factors (temperature and precipitation) of post growing season were the main factors affecting tree growth at the upper distribution limits in Potatso National Park, but varied with tree species. 2) The radial growth of P. brachytyla was mainly limited by temperature condition during the post growing season (September--October of previous year), and was negatively correlated with mean temperature of post growing season in previous year (September-October of previous year), meanwhile higher temperature during the growing season (June--August) of current year positively affected its radial growth. 3) Precipitation in October and the post growing season of previous year (September--October) was the main factor limiting the radial growth of L. potaninii, with a significant and negative correlation between the residual chronology and precipitation. 4) The radial growth of A. georgei was mainly limited by climatic factors of the growing season, presented by a significant and positive correlation between radial growth and mean temperature of growing season (June--August) and post growing season(September--October) in current year. This study can provide basic data for climate reconstruction in Shangri-La, northwestern Yunnan of southwestern China.