D Sex-Specific Responses Of Tree-Ring Growth To Climate In The Dioecious Tree Populus Cathayana

AimsRadial growth in response to climate has been reported in many trees, but the sex-specific responses of tree-ring growth associated with altitude in dioecious trees are still poorly known. This study aims to examine whether (i) there are sex-related responses of treering growth to climate in dioecious trees; (ii) these responses could be changed with altitude elevation.MethodsThe tree-ring width and basal area increment (BAI) were measured over the past 30 years (1982-2011), and the sexual differences in relationship between BAI and time span and correlations between ring width and climatic factors were investigated in Populus cathayana trees at two altitude sites (1,450 m and 1,750 m a.s.l.) in Xiaowutai Mountain, Hebei, north China.Important FindingsThe BAI was increased over the past 30 years. Trees at high-altitude sites had significantly lower mean ring width and mean BAI than those trees at low-altitude sites (P < 0.001). In addition, sexual differences in tree-ring growth and its response to climate were more pronounced by altitude elevation. Male trees had a significantly larger mean ring width and mean BAI than did females at high-altitude sites, whereas no significant sexual differences in these traits were detected at low-altitude sites. Female trees were sensitive to previous October-November temperatures at high altitude but to current February and April precipitation at low altitude (P < 0.05), whereas male trees were sensitive to current June temperature at high altitude but to January precipitation at low altitude (P < 0.05). Our results indicated that the responses of tree-ring growth to climate are sex dependent and can be changed with altitude elevation.