Abstract: Fagus hayatae Palib. is a rare and endemic tree species in China. It is classified as a national secondgrade key protected wild species of China, and is the only species of genus Fagus that has been intermittently distributed from the subtropical mountains of mainland to Taiwan Island of China. In this study, we constructed a Biomod2 ensemble model to predict the potential suitable distribution area of F. hayatae and the environmental factors that limit its distribution, providing theoretical support for formulating effective protection measures. Based on the geographic distribution data of 82 raw occurrence records of F. hayatae, the suitable distribution range, the main environmental variables affecting its distribution, the changes in suitable habitats and the centroid shift under future climate conditions were evaluated and analyzed with three types of data: climate, topography, and soil, and the Biomod2 ensemble model. The results showed that the evaluation scores of the individual models-Random Forest (RF), Generalized Additive Model (GAM) and Generalized Boosted Model (GBM)-in the Biomod2 ensemble model were all close to 1, indicating that the ensemble model reached an excellent standard. The monthly mean diurnal range (Bio2), isothermality (Bio3), and elevation (elev) were the main environmental factors affecting the suitable distribution of F. hayatae. The total suitable area of F. hayatae under the current climatic conditions was about 5.10×10⁵ km², and the highly suitable areas were mainly distributed in the southwest and Taiwan of China. The potential distribution area and the actual distribution area showed a high degree of coincidence. Under future climate conditions, the highly suitable distribution area of F. hayatae will be significantly reduced. Among them, the reduction will be the greatest under the SSP24.5 emission scenario from 2081 to 2100, and the centroid of the suitable distribution area will mostly shift towards higher latitudes. In the future climate, F. hayatae will be drastically reduced in Southwest China and grow stably in Taiwan of China. It is suggested that nature reserves should be established in advance in the drastically reduced areas in Southwest and Central China. The results can provide scientific basis for in situ conservation of this endangered species, and also offer a reference for the selection of ex-situ conservation sites.

Key words: climatic change, distribution dynamics, relict plant, endangered species