Abstract: Tree growth variability is a key determinant of forest stabilities. Previous studies have shown that recent climate change has increased variability in tree growth, while others have challenged this viewpoint, leading to ongoing debate in this field. Moreover, gaps remain in understanding the climatic mechanisms driving increased tree growth variability, particularly for species simultaneously limited by multiple climate factors. In this study, we assessed the temporal trends in variability of Picea purpurea radial growth and its linkage with growth-climate sensitivity utilizing dendrochronological methods. Our results revealed a significant increase in P. purpurea radial growth variability from 1960 to 2020, as indicated by continuous rises in the standard deviation, coefficient of variation, and mean sensitivity of tree-ring width indices. The increased frequency of extreme growth declines further supported this finding. Furthermore, moisture condition in July was identified as a key limiting factor of P. purpurea growth. Notably, the strengthening relationship between tree-ring width indices and vapor pressure deficit (VPD) suggests that the moisture sensitivity for P. purpurea growth has increased over the period 1960–2020. This enhanced sensitivity to VPD, whose interannual variability has also increased synchronously, may have contributed to the rise in P. purpurea growth variability. Additionally, the maximum temperature in May was positively correlated with P. purpurea growth; however, there is little evidence that this factor contributed to the observed increase in growth variability. These findings provide new insights into P. purpurea growth trends and improve our understanding of the potential future impacts of climate change on forest ecosystems.

Key words: Tree growth variability, Growth-climate response, Tree-ring, Picea purpurea