Abstract: In the context of global warming, we investigated the growth dynamics and climatic response mechanisms of Populus cathayana in the Jiuzhaigou region, western Sichuan Plateau, an endemic broadleaf species in China. We developed a standardized tree-ring width chronology to analyze radial growth response to climatic factors from 1959 to 2022. Moving correlation analysis was applied to assess the stability of climate-growth relationships, and growth change percentage (PGC) method was used to identify growth release and suppression events. The results showed that the tree-ring width of P. cathayana was significantly positively correlated with May-June average maximum temperature (r=0.525), mean temperature (r=0.548), and average minimum temperature (r=0.341), but significantly negatively correlated with precipitation (r=-0.260), relative humidity (r=-0.579), and cloud cover (r=-0.483) during the same period. PGC analysis revealed three significant growth release events (1937-1940, average PGC=32.8%; 1977-1978, average PGC=42.2%; 1999-2004, average PGC=43.3%) and one significant growth suppression event (2008-2010, average PGC=-28.9%). Moving correlation analysis revealed a marked shift in climate-growth relationship during the 1970s, characterized by the transition of growing-season temperatures from negative to significantly positive, while relative humidity and self-calibrated Palmer drought severity index correlations shifted from positive to significantly negative. These findings underscore the non-stationary climatic responses of P. cathayana in western Sichuan, suggesting that warmer and drier conditions in the growing season favor the radial growth.

Key words: tree ring, radial growth, broadleaf tree, climate change, western Sichuan Plateau, Populus cathayana