Predicting the Potential Distribution of the Endangered Plant Eucommia ulmoides in China under the Background of Climate Change

Eucommia ulmoides, a single extant species of Eucommiaceae, is a perennial deciduous tree distributed across central China. The bark of E. ulmoides is rich in chlorogenic acid and flavonoids that possesses high medicinal value, whereas its leaves and seeds contain abundant Eucommia ulmoides gum (EUG), which is a unique strategic resource in China that can be used as a substitute for natural rubber. Under the background of global warming, the evaluation of habitat suitability is of great significance for the protection and management of E. ulmoides. For this study, maximum entropy (MaxEnt) modeling was employed to simulate the potentially suitable region for E. ulmoides over four periods (current, 2050s, 2070s, and 2090s) under four climate change scenarios (SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5), as well as to analyze changes in the spatial patterns of E. ulmoides and the essential environmental factors affecting the growth and distribution of E. ulmoides. The results revealed that the current potentially suitable region for E. ulmoides was 211.14 x 10(4) km(2), which accounted for 21.99% of China's territory. The low impact areas for E. ulmoides were distributed in Guizhou, Zhejiang, Sichuan, eastern Chongqing, southern Shaanxi, western Hubei, eastern Shandong, southern Anhui, southern Gansu, and northern Yunnan Provinces. The key bioclimatic variables affecting the distribution of E. ulmoides were mean diurnal range and mean temperature of the coldest quarter, with their contribution rates of 53.8% and 41.4%, respectively. Furthermore, core distributional shift analysis indicated that the center of the potentially suitable regions of E. ulmoides exhibited a general trend of shifting to the northwest and high latitudes. Finally, conservation strategies are proposed, such as the establishment of ex situ protection sites and germplasm resource collection. Future researchers can conduct further studies by integrating the quality of E. ulmoide herbs and environmental variables. In this study, for technical reasons, we only considered the effect of climate on species distribution without considering other biotic and abiotic factors, which can be further addressed by future researchers.