Abstract: Populus purdomii, a typical dioecious plant species, is often used as a pioneer species in vegetation succession and ecosystem restoration. It is important to understand the response and adaptation characteristics of dioecious species to environmental changes under the background of global climate change. In this study, we examined the differences of radial growth of tree rings between male and female P. purdomii at high (2600 m, malebiased ratio) and low altitude (2000 m, balanced sex ratio) in Gongga Mountain, and analyzed the correlations between radial growth and climatic factors. The results showed that: (1) There was no significant difference in average annual radial growth and basal area increment (BAI) between male and female P. purdomii at 2000 m, whereas male P. purdomiiexhibited higher radial growth than female at 2600 m. (2) At low altitude, the BAI of male and female P. purdomii was positively correlated with the highest temperature in last October and February and the average temperature in current February, while negatively correlated with precipitation in current February. The negative correlation between BAI and relative humidity in different months was more frequently found in male P. purdomii than in female. (3) At high altitude, there were significantly positive correlations between BAI and average temperature in last December and current May to July in both genders, while no significant correlations of BAI with precipitation and Palmer drought severity index (PDSI) were found. Therefore, the gender specific radial growth of P. purdomiicould partly explain the skewed sex ratio pattern at different altitudes. This study provides a theoretical reference for predicting the dynamics of population size and spatial characteristics of dioecious plants under future climate change.

Key words: Populus purdomii, radial growth, response to climate, adaptation characteristics.