Spatial patterns and temporal evolution of tree radial growth responses to climate in the Tianshan Mountains

Understanding how tree growth in alpine forests in arid and semi-arid areas responds to climate variability is a crucial concern. We collected 1549 samples from 44 sites across the Tianshan Mountains and established a network of tree-ring width chronologies for Picea schrenkiana. Principal component analysis revealed spatial heterogeneity in tree radial growth in the western and eastern subregions of the Tianshan Mountains. We also found that precipitation from previous July to current June (before and early growing season) was a key driver of tree growth throughout the Tianshan Mountains, moisture availability in the April-October (growing season) was more limiting in the eastern region, which led to spatial heterogeneous responses of tree growth to climate. Following the transition from warm-wet to warm-dry conditions in 1998, tree growth responses to climate also shifted. The influence of precipitation in the pre-growing-season remained dominant, the impact of temperature during the growing season increased significantly. We also found that temperature suppressed tree growth in the western region through drought stress, while the limiting effect of precipitation on tree growth became more pronounced in the eastern region. Both spatial and temporal characteristics of tree growth responses to climate intensified with decreasing annual precipitation. Therefore, prioritizing moisture availability is imperative for effective forest management and ecological protection in the Tianshan Mountains.