Abstract: Cercidiphyllum japonicum is one of the second-class national protected plant species in China, with extremely low ability of regeneration in isolated natural populations. The prediction of its suitable habitats can provide a scientific basis for delineating management units of C. japonicum in different regions. Based on the geographical distribution data of C. japonicum in China, 22 environmental indicators were adopted in the MaxEnt model to predict its potential suitable habitats in China. We further compared the population structure of C. japonicum in different regions to clarify the ecological factors determining its distribution and population characteristics. The results showed that the potential suitable habitats of C. japonicum were mainly located in the western margin of the Sichuan Basin, Shennongjia, Qinling-Daba Mountains, and isolated hills in east China. Climatic and topographic factors had a joint influence on the distribution of C. japonicum. The factors which had main contribution to its potential suitable habitats included annual precipitation, the minimum temperature in the coldest month, slope, and altitude. Results of principal component analysis showed that the 11 populations surveyed in different regions could be divided into three groups, including populations in Qinling-Daba Mountains, populations in the western margin of Sichuan Basin, and populations in eastern China. Environmental factors had different effects on population density and survival rate of C. japonicum at different growth stages, with stronger correlation between population characters and climate factors at the early growth stage.

Key words: Cercidiphyllum japonicum, MaxEnt model, potential distribution, population characteristics, ordination, environmental factor.