Geographical and aridity gradients along with species variation shape tree growth sensitivity in the Northern and Southern Transitional Zone of China

Understanding the spatial distribution of tree growth sensitivity in response to climate change is essential for developing effective adaptive forest management strategies, particularly in vulnerable ecotones and transitional zones. Here, we present a network of 70 tree ring width chronologies from 12 tree species to systematically investigate the radial growth responses to key climatic factors, including temperature, precipitation, and drought (scPDSI), across the North–South transitional zone in China (NSTZ). Our analysis reveals that late spring to early summer (April to June, r = 0.01 ‒ 0.53) precipitation exerts a positive influence on the growth of most species, whereas temperature tends to suppress tree growth during late spring (May, r = -0.44 ‒ -0.01) and early winter (December, r = -0.40 ‒ -0.03). Further redundancy (RDA) and GeoDetector (GD) analysis indicates that the spatial variability of growth sensitivity is primarily governed by combined geographic, aridity gradients, and species, with local microclimatic variables such as vapor pressure deficit (VPD) and soil moisture exerting comparatively weaker influences. Multi-model projections under the SSP2-4.5 and SSP5-8.5 scenarios suggest that the transitional zone is likely to experience a drier and increasingly heterogeneous eco-climatic regime (the mean coefficient of variation > 0.25). Such changes may intensify the spatial divergence and potential destabilization of tree growth–climate relationships, posing challenges for forest ecosystem long-term sustainability.