Maxent Modeling for Predicting the Potential Geographical Distribution of Castanopsis carlesii under Various Climate Change Scenarios in China

Castanopsis carlesii (Hemsl.) Hayata. 1917 is an established subtropical evergreen broad-leaved tree species with rapid growth rates and a strong plasticity to environmental changes. It is widely distributed in East Asia; however, it is unclear how climate change influences the distribution of this tree species. Based on 210 valid occurrence records and 10 environmental variables, we used maximum entropy model (Maxent) to predict its potential geographical distribution under present and three future climate scenarios (SSP126, SSP245 and SSP585) in both the 2050s and 2070s, and determined the influence of climate on the distribution of C. carlesii. The area under the curve (AUC) value of the simulated training and the test were 0.949 and 0.920, respectively, indicating an excellent forecast. The main climatic factors affecting the distribution of C. carlesii are mainly precipitation, especially that of the driest month (Bio14, 75.5%), and annual precipitation (Bio12, 14.3%); its total contribution rate is 89.8%. However, the impact of average mean temperature is lesser in comparison (Bio1, 5.7%). According to the present-day predictions, C. carlesii has a suitable habitat of 208.66 × 104 km2 across most of the tropical and subtropical regions south of the Yangtze River. The medium and high suitability areas are mainly in Taiwan, Fujian, Jiangxi, Guangdong, Hainan and Guangxi Provinces. With the climate projected to warm in the future, the distribution area of C. carlesii exhibited a tendency of northward expansion along the Qinling–Huaihe line, mainly manifested as the increase in low and medium suitable areas. The area of high-suitable areas decreased significantly under the three climate scenarios both for the 2050s and 2070s, and only a few areas showed contraction of suitable areas. Therefore, expansion areas can be used for cultivation or introduction trials, while contraction areas require enhanced preservation and collection of genetic resources. Our findings provide a theoretical basis for formulating the adaptation and protection strategies to cope with future climate change as well as theoretical guidance for the introduction, cultivation and sustainable development of C. carlesii.