Responses of radial growth of <i>Populus cathayana</i> to climate change in the western Sichuan Plateau, China.

In the context of global warming, we investigated the growth dynamics and climatic response mechanisms of <i>Populus cathayana</i> 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 <i>P. cathayana</i> was significantly positively correlated with May-June average maximum temperature (<i>r</i>=0.525), mean temperature (<i>r</i>=0.548), and average minimum temperature (<i>r</i>=0.341), but significantly negatively correlated with precipitation (<i>r</i>=-0.260), relative humidity (<i>r</i>=-0.579), and cloud cover (<i>r</i>=-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 <i>P. cathayana</i> in western Sichuan, suggesting that warmer and drier conditions in the growing season favor the radial growth.