[Tree architecture variation of plant communities along altitude and impact factors in Maoer Mountain, Guangxi, China].

Three typical plant communities (evergreen broad-leaved forest at low-altitude 1100 m, evergreen and deciduous mixed broad-leaved forest at mid-altitude 1500 m, and evergreen conife-rous and broad-leaved mixed forest at high-altitude 1900 m) in Maoer Mountain, Guangxi, China were surveyed along an altitude gradient. We measured the tree layer plant architecture and environmental factors, to analyze the variation of plant architecture traits among the three communities and its influencing factors. The results showed that the tree layer canopy area, basal diameter at 45 cm height, diameter at breast height (DBH), and leaf convergence increased with increasing altitude, whereas tree height, branch height, and canopy thickness first increased and then decreased. Horizontal branches occurred more often in communities at lower altitude , less frequent at high altitude, and the least frequent in middle altitude communities. Correlations among tree layer plant architecture traits were stronger in the mid-altitude community than that in the other altitude communities. Results from the redundancy analysis showed that soil organic matter and total solar radiation were the main factors driving the variation of plant architecture traits in the tree layers, accounting for 39.6% and 23.9% of the total variation, respectively. Soil organic matter had a greater positive impact on canopy area and branch height, whereas total solar radiation was more influential on the DBH and 45 cm basal diameter. In conclusion, tree layer architecture of communities along the altitude gradient in Maoer Mountain was divergent, with soil organic matter and total solar radiation as the main driving forces.