Abstract:

Objective: This study aims to investigate the response characteristics and adaptability of three main pine species (Pinus densata, Pinus yunnanensis, and Pinus kesiya var. langbianensis) to regional climate change in Yunnan, for guiding the prediction of forest growth dynamics in southwest China in the context of climate change, and providing a theoretical basis for forest protection and management in this area. Method: According to the standardized dendrochronological methods, tree ring samples were collected in the distribution areas of various tree species to construct tree-ring chronologies. Combined with climate data including temperature, precipitation, and Palmer drought index at each sampling point from 1958 to 2018, response analysis, multiple regression analysis, and moving correlation analysis were used to determine the critical climate factors affecting the radial growth of the three pine species and their differences in response to climate change. Result: The climate at the sampling sites of the three pine species was warming and drying. The key factors limiting radial growth of P. densata were the precipitation in May and the mean temperature in January, which contributed 59.8% and 27.5% to the variance interpretation rate of the regression model. The critical factors limiting radial growth of P. yunnanensis were the precipitation in October, December of the previous year and January, which contributed 38.8%, 15.4% and 25.4% respectively to the variance interpretation rate of the regression model. The critical factors limiting radial growth of P. kesiya var. langbianensis were the precipitation in the current growing season (July), and precipitation in late growing season (September) of the previous year and current year, and their contribution to the variance interpretation rate of the regression model reached 53.8%, 30.9% and 15.3%, respectively. The radial growth of P. yunnanensis trees was more sensitive to drought than that of P. densata and P. kesiya var. langbianensis trees. Warming and drying enhanced the sensitivity of P. densata to temperature and precipitation in early growing season (May), warming and drying weakened the sensitivity of P. yunnanensis to precipitation in early growing season (May) and enhanced the sensitivity to temperature in growing season, and warming and drying weakened the sensitivity of P. kesiya var. langbianensis to mean and maximum temperature in July and enhanced the sensitivity to precipitation in late growing season (September) of previous year. Climate warming caused the response relationship between radial growth of each pine species and climate factors unstable, which occurred during the period of climate change, synchronized with regional climate fluctuations, and had consistency among different pine species. Conclusion: P. densata and P. kesiya var. langbianensis trees have stronger adaptability to droughts than P. yunnanensis trees. Climate warming weakens the promoting effects of temperature on radial growth of P. densata at high altitude. Warming transforms the sensitivity of P. yunnanensis from being sensitive to low precipitation in early growing season to being sensitive to low temperatures in growing season. Climate warming inhibits the promotion effect of sufficient water conditions on radial growth of P. kesiya var. langbianensis in the growing season, and enhances the lag effect of climate factors on radial growth. The response sensitivity of the three pine species to climate factors becomes unstable due to climate warming.

Key words: Pinus yunnanensis, Pinus densata, Pinus kesiya var. langbianensis, annual rings, climate change, climate response, sensitivity, stability