Variations of monthly radial growth of Chinese fir [Cunninghamia lanceolata (Lamb.) Hook.] considering its responses to climatic factors

The relationship between tree radial growth and climate factors is intricate and affected by various factors related to global climate change. Chinese fir [ Cunninghamia lanceolata (Lamb.) Hook.)] is a crucial fast-growing timber species in subtropical China. Its productivity, primarily determined by radial growth, has been influenced by climate change. Our study aimed to explore growth patterns and elucidate the correlation between radial growth and climate factors in Chinese fir plantations across four distinct climatic regions. Through correlation analysis and structural equation model (SEM), we explained the relationship between radial growth trends and climate factors. The results showed that monthly radial growth differed among the four production areas, with an “unimodal curve” in Fujian and Jiangxi, a “bimodal curve” in Hunan, and a “trimodal curve” in Yunnan. Radial growth was positively correlated with temperature and precipitation. The dryness index had a weak correlation with radial growth in Fujian and Jiangxi but a significant positive correlation in Hunan and Yunnan. SEM analyses indicated path coefficients for biological factors influencing radial growth (0.352 in Fujian, 0.616 in Jiangxi, 0.595 in Hunan, and 0.528 in Yunnan) and climate factors ( -0.003 in Fujian, 0.150 in Jiangxi, 0.265 in Hunan, and 0.005 in Yunnan). The factors affecting radial growth were the least in Fujian and the most in Yunnan, indicating greater climate sensitivity in the radial growth of Chinese fir from coastal to inland areas. These results enhance our understanding of climate impacts on forest productivity and offer a scientific basis for sustainably managing subtropical plantations under climate change.