Phoebe hui is a rare wood species in China and belongs to the national second-class protected species. The simulation of regional changes in the suitable physiology of P. hui since the middle of Holocene, the investigation of its response to historical climate change, and the prediction of its future geographical distribution pattern can provide a reference for the formulation of resource conservation strategies and afforestation regionalization of P. hui.

Based on the existing geographic distribution data and climatic factors, the R language Kuenm package was invoked to adjust and optimize the feature combination (FC) and regularization multiplier (RM) of MaxEnt prediction model for modeling. The main climatic factors affecting the distribution of P. hui were tested and evaluated by the contribution rate of climatic factors and cutting method. The reliability and accuracy of the model results were evaluated by the area under the receiver operating characteristic curve (AUC) of the model output. Based on the output results of MaxEnt and ArcGIS software, the geographical distribution of the suitable areas from the middle Holocene to the future (2050s, 2070s, 2090s) under different climate scenarios (SSP2-4.5, SSP5-8.5) was obtained to analyze the migration trend of its distribution center in the future.

Model optimization results showed that when RM=0.7 and FC=QH, MaxEnt model complexity and overfitting degree were low, and model prediction accuracy was high. The AUC of the receiver operating characteristic curve is 0.984±0.005, which indicates that the prediction result is good. Based on the contribution rate of climatic factors and the assessment results of the knife cutting method, Annual precipitation (contribution rate=42.1%), Precipitation of Coldest Quarter (contribution rate=15.7%), Precipitation of Warmest Quarter (contribution rate=9.9%), Mean Temperature of Warmest Quarter, Temperature Seasonality (contribution rate=7.6%), Min Temperature of Coldest Month (contribution rate=7.3%) and Mean Diurnal Range Mean of monthly (contribution rate=6.1%) were the dominant limiting factors for the geographical distribution of P. hui. The prediction results of the model showed that P. hui was mainly distributed in southwest China and a few areas in central and South China from the middle of Holocene to the present, and the overall suitable area showed a decreasing trend. In the future, the habitat area of P. hui will continue to decrease, and the distribution center will gradually migrate to the north, only in Wulong District and Nanchuan District of Chongqing, as well as in the junction area between Chongqing and southwest Hubei, Yunnan and southwest Guizhou, there will be small areas of high habitat.

The optimized MaxEnt model can accurately predict the potential geographical distribution area of P. hui, which is mainly restricted by precipitation and temperature climate factors, and the precipitation factor plays a leading role. Since the middle of the Holocene, the suitable distribution area of P. hui has been decreasing and fragmentizing, especially under the high emission concentration of greenhouse gases in the future. The distribution center tends to migrate from low latitude to high latitude, and the population extinction risk is high. The results of this study can provide theoretical reference for exploring the mechanism of response to climate change, and explore the future suitable growth areas according to the distribution change and migration trend of P. hui maximus to reduce the extinction risk.