Differential Performance of Distribution Shifts Between Endangered Coniferous and Broad-Leaved Tree Species in Subtropical China Under Climate Change

Global warming has become one of the most serious threats to biodiversity. However, the responses of endangered tree species in subtropical regions to climate change and their potential distribution shifts remain elusive. In this study, we selected nine rare and endangered tree species in the subtropical forests of China encompassing both coniferous and broad-leaved groups, and conducted an assessment of their suitable distribution patterns and spatial shifts under current and future climate scenarios (SSP126, SSP370, and SSP585). For this we utilized an optimized MaxEnt model integrating multidimensional environmental variables including climate, soil, and topography. The results show that the model has high predictive accuracy after parameter optimization, with mean AUC values exceeding 0.98 for both broad-leaved and coniferous tree species. Our analysis of environmental factors indicates clear differences in distribution-limiting factors between the two functional groups. Broad-leaved species are primarily constrained by temperature-related variables, particularly the mean temperature of the coldest quarter (Bio11) and the mean diurnal range (Bio2), whereas coniferous species are more sensitive to moisture conditions, with the precipitation of the driest quarter (Bio17) as the key limiting factor for their potential distributions. Under current climatic conditions, highly suitable habitats for both functional groups are mainly concentrated in the middle and lower reaches of the Yangtze River. Under future climate scenarios, broad-leaved species are in general expected to expand in marginal areas, while coniferous species show pronounced scenario dependence, with significant contractions occurring under certain scenarios and time periods. Despite the evident changes at distribution margins, the overall shifts in the centroids of potential distributions for both functional groups will be limited, with core suitable areas remaining relatively stable. This study reveals differences in the spatial response patterns between conifers and broad-leaved trees, and provides a scientific basis for the development of differentiated conservation strategies and the identification of conservation priority areas under climate change.