Stand age influences the climate response and growth resilience of Picea wilsonii to extreme drought and cold events.

Global climate change has intensified the frequency and severity of extreme climate events, posing significant threats to forest ecosystem stability. While the impacts of drought have been extensively studied, the comparative resilience of trees to different types of stressors (such as extreme cold) and how these responses vary across developmental stages remains poorly understood. In this study, two standard chronologies of middle-aged and mature Picea wilsonii in the eastern Loess Plateau were developed and climate-growth relationships were assessed via bootstrapped correlation, and calculated resistance, recovery, and resilience indices were compared using one-way ANOVA. Results showed that middle-aged growth is primarily promoted by moisture during the late growing season (July-September), whereas mature trees are governed by pre-growing season moisture levels. Under extreme drought, middle-aged stands exhibited higher resistance but lower recovery than mature stands; this pattern was reversed under extreme cold, with both age classes reaching comparable resilience. Intra-stand analyses revealed that middle-aged trees have lower resistance but higher recovery and resilience under cold than drought. Conversely, mature trees showed higher resistance and resilience under cold than drought, but similar recovery across stressors. These findings indicate that different age classes follow divergent stabilization strategies: an opportunistic strategy in middle-aged trees versus a conservative strategy in mature trees. These findings indicated that management should be age-specific, prioritizing drought mitigation for younger stands and protecting the structural integrity of mature forests to ensure their function as stable carbon reservoirs in a changing climate.