Assessing climatic response and drought resilience in growth of Pinus tabulaeformis Carr. and Tsuga chinensis Pritz. on the southern slope of the Qinling Mountains

Abstract

Climate anomalies have significant impacts on forest productivity and tree mortality worldwide, leading to ecological disturbances. Understanding the climate-growth relationship and species-specific responses to climate and drought events are crucial for developing effective conservation strategies for tree growth. However, studies on such issues are scarce in the Qinling Mountains (QLM), a significant geo-ecological boundary for climate, vegetation distribution, and river systems in China. This study focuses on the southern slope of the QLM, where we developed tree-ring-width chronologies for Pinus tabulaeformis Carr. and Tsuga chinensis Pritz. in the same habitat, and analyzed their response to climate and two extreme drought events. Both species were found to have a positive correlation with temperature, but their responses to precipitation and scPDSI differed. Specifically, P. tabulaeformis showed a negative correlation with precipitation and scPDSI, while T. chinensis exhibited a positive correlation with precipitation. These differences in response may be attributed to species-specific preferences and interspecific competition between the two coniferous species. Results of the 31-year sliding correlation analysis and K-S test analysis, which aimed to explore the dynamic relationship between chronologies and their most limiting climate factors, demonstrated that both P. tabulaeformis and T. chinensis have experienced a qualitative change in their response patterns to certain climatic factors. Under the backdrop of warming climate, the response of P. tabulaeformis to the maximum temperatures from June to September of the previous year has diminished to a non-response; the response to precipitation from July to September of the previous year, although still significantly negatively correlated, has seen a decrease in significance. In contrast, T. chinensis has exhibited an increasing sensitivity to precipitation from September of the previous year to June of the current year. Study on resistance (Rt), recovery (Rc), and resilience (Rs) of tree growth to drought events revealed that P. tabuliformis and T. chinensis did not exhibit a negative response to the transient drought event in 1933 AD. However, when faced with the prolonged and severe drought event in 1941–1944 AD, both species experienced a decline in growth. It was observed that T. chinensis displayed weaker drought tolerance compared to P. tabuliformis and was more susceptible to the negative impacts of drought conditions. These findings suggest that forest management in the context of climate change should be species-specific, and more effort is needed for species with weaker drought resistance in the QLM, such as T. chinensis.