Urban-suburban differences in the response of typical greening tree species to extreme drought in a subtropical city.

Introduction: Against the backdrop of global change, the mechanisms by which the urban heat island effect and climate warming influence tree growth in urban versus suburban areas remain poorly understood. Methods: We collected tree core samples of four common greening tree species from urban and suburban areas of Nanchong, a subtropical city in Sichuan Province, and established tree-ring width chronologies to analyze differences in radial growth responses to climatic factors. Results: Over the past decade, the growth rate of suburban trees was significantly higher than that of urban trees. Water availability was the key factor limiting urban tree growth, whereas rising temperatures promoted tree growth in both urban and suburban areas to a certain extent. Suburban trees were more sensitive to spring temperature, while summer high temperature had a more pronounced effect on urban trees. During extreme drought events, suburban trees exhibited higher recovery and resilience, likely attributable to the more favorable water environment in suburban areas. Ring-porous poplar exhibited the lowest resistance and resilience during extreme droughts, whereas the diffuse-porous evergreen broadleaf Discussion: This study reveals the urban-suburban differentiation in tree growth responses to climate change under urbanization, providing a theoretical basis for enhancing the climate adaptability and scientific management of urban forests in subtropical cities.