There is no enough data or evidence to reach a firm conclusion for tree species diversity and related mechanism in an evergreen broad-leaved forest in Ailao Mountains, Yunnan, China. A 6-hm2 plot was established in Ailao Mountains State Nature Reserve for the purpose of monitoring long-term dynamics of tree populations. All free-standing trees with diameter at breast height (DBH) ≥ 1 cm were tagged, mapped, measured (girth) and identified to species in the plot. The spatial distribution patterns of four dominant canopy tree species in the plot were analyzed using a point pattern analysis Ripley’s L-function. A total of 12131 free-standing individuals with DBH ≥ 1 cm were recorded in the plot, including 68 species belonging to 49 genera and 25 families. Lithocarpus hancei had the largest basal area and the largest importance value. Camellia forrestii, an understory tree species was ranked the second in terms of importance value, although it showed the highest abundance (1712 individuals). The four canopy dominant species had a large number of seedlings and saplings and tend to be patchily distributed. And the spatial distributions of 26 tree species with ≥40 individuals was examined at each life history stage (diameter at breast height ≥1 cm), and 37 of 57 life history stages showed aggregated distribution pattern. It showed that it may be not density dependence but habitat heterogeneity as a prevalent mechanism for regulating the population spatial structure of most tree species in the subtropical forest studied here.
Key words: Evergreen broad-leaved forest, habitat heterogeneity, spatial distribution pattern, tree species diversity.
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