Impacts of Climate Change on Suitable Habitat Areas of Larix chinensis in the Qinling Mountains, Shaanxi Province, China

Larix chinensis Mill., the sole tree species that can form pure forests at the timberline of the Qinling Mountains, plays a crucial role in maintaining the stability of high-altitude ecosystems. Owing to its special habitat requirements and fragmented distribution pattern, populations of L. chinensis are in a clear degenerating stage. Numerous studies have underscored the significant effect of climate change on high-altitude vegetation. However, studies focusing on the shifts in the distribution of L. chinensis habitats and the key environmental factors hindering their suitable distribution remain limited. Therefore, this study aimed to explore the influence of climate change on the future potential distribution of L. chinensis in order to understand the response of timberlines to climate change. In this study, random forest algorithms were applied to project the future potential distribution of L. chinensis across the Qinling Mountains. The results found that temperature and precipitation play crucial roles in limiting the distribution of L. chinensis, particularly in cold-humid climates and rainy, foggy environments, which contribute to its patchy distribution pattern. Currently, L. chinensis populations are distributed in Taibai Mountain and its surrounding alpine areas, concentrated at elevations of 2900-3300 m and on southern slopes of 15-35 degrees, covering approximately 3361 km2. The ecological niche of L. chinensis is relatively narrow in terms of these environmental variables differing from the prevailing climate in the Qinling Mountains. During past climatic conditions or the last interglacial period (LIG period), the potential distribution range of L. chinensis gradually reduced, especially in low-elevation areas, nearly disappearing altogether. Projections under future climate scenarios suggest the contraction and fragmentation of suitable habitats for L. chinensis. The response of L. chinensis to the RCP 8.5 scenario exhibited the most pronounced changes, followed by the RCP 4.5 scenario. Under all climate scenarios in the 2050s, L. chinensis-suitable distribution exhibited varying degrees of reduction. Under the RCP 8.5 scenario, a significant decrease in suitable distribution is projected. Suitable distribution will continually decrease by the 2070s, with the most significant decline projected under the RCP 2.6 scenario. In conclusion, our findings not only offer management strategies for the populations of L. chinensis amidst climate change but also serve as crucial references for some endangered tree species in climate-sensitive areas.