[Response of radial growth to climate change in Pinus koraiensis with different diameter classes]

Dendrochronological techniques were used to study the response of radial growth of Pinus koraiensis with different diameter classes to climate change throughout the natural range of broad-leaved Korean pine forests, including Baishilazi Nature Reserve (40.9° N), Changbai Mountain Nature Reserve (42.4° N), Liangshui Nature Reserve (47.2° N), and Shengshan Nature Reserve (49.4° N). We investigated the similarities and differences of growth responses of different diameter classes to climate factors and clarified the key climate factors affecting the growth of P. koraiensis at different latitude sites. We explored the dynamic changes of the radial growth of P. koraiensis from the latitudinal gradient over the past 40 years. The results showed many similarities in the response of two diameter classes to local climate factors. Small diameter (diameter at breast height of 10-20 cm) trees were more sensitive to the changes of average minimum temperature of the current growing season and the meteorological factors of the previous year, whereas large diameter (diameter at breast height >40 cm) trees were more sensitive to the changes of average maximum temperature and average relative humidity of the current growing season. The key meteorological factors that affecting radial growth of P. koraiensis differed along the latitude gradient. In Baishilazi Nature Reserve, the southernmost plot, the key climate factors were the average maximum temperature and the average maximum temperature in the current growing season. In Shengshan Nature Reserve, the northernmost sample plot, the key climate factors were low temperature factors, such as the minimum temperature in all seasons, the average maximum temperature in winter, the average temperature of all seasons except for the end of previous growing season and the current growing season. The Palmer drought severity index (PDSI) in the current growth season and the end of the current growth season and the precipitation in the current growth season were the key climate factors in Changbai Mountain Nature Reserve. The average temperature of the current growing season was the key climate factor of Liangshui Nature Reserve. In recent four decades, with the rising of temperature, the radial growth of P. koraiensis of two diameter classes significantly decreased in the southernmost point, significantly increased in the northernmost point, and had no significant variation in middle latitudes.