Response of radial growth of Abies georgei and Tsuga dumosa to climate change at upper distributional limits on Laojun Mountain, Lijiang, Yunnan, China

Based on the dendrochronological method,tree width data of Abies georgei and Tsuga dumosa at their upper distributional limit in Laojun Mountain were used to develop tree-ring residual chronologies. In order to clarify the main climatic factors affecting the radial growth of two conifer species,we used response function and moving interval analysis to study relationships between chronologies and temperature and precipitation,and the stability of the relationships. The results showed that the response of the two tree species was consistent in cumulative effects of precipitation,but different in monthly climatic factors,and the relationships were stable. The detail results were as follows:( 1) November mean temperature in last year and growing season( July-August) precipitation in current year promoted the radial growth of A.georgei at the upper distributional limit.( 2) The radial growth of T. dumosa was significantly and positively correlated with the precipitation in March,the dormant period( January-March) and growing season of current year,but the growth was significantly and negatively correlated with July temperature in last year,May temperature and post-growing season( September-October) precipitation in current year.( 3) The relationships between radial growth and climatic factors were stable by presenting significant correlations in most or whole analysis periods( 1951-2017),and the stability of T. dumosa was stronger than A. georgei. The result of this paper can provide a theoretical basis for the prediction of tree growth and the management and protection of forest ecosystems in the northwestern Yunnan Plateau under the background of climate change.