Abstract: We explored the effects of community structure and topography on regeneration in a subtropical northern-margin evergreen broad-leaved forest on the southern slope of Shennongjia with Cyclobalanopsis myrsinifolia and Cyclobalanopsis oxyodon as dominant species. We classified all the plots into four topographic categories: ridge, gentle slope, steep slope, and valley. Surveys were conducted in terms of standing trees, dead trees, and regenerating seedlings. Correlation analysis and one-way ANOVA were applied to assess the effects of community structure and topography on seedling regeneration. A total of 15470 regenerating seedlings were recorded, belonging to 20 families, 31 genera, and 40 species. The regenerating seedlings of Neolitsea wushanica, Machilus faberi, Cyclobalanopsis oxyodon, and Cyclobalanopsis myrsinifolia had predominant importance values. The abundance of regenerating seedlings was positively correlated with species richness of both standing and dead trees (all P<0.01), and showed a parabolic relationship with the number and sum of basal area of standing trees. Most of dominant regenerating seedlings were significantly associated with community structural attributes (P<0.01). There were significant differences in abundance and richness of regenerating seedlings among different topographic types (P<0.01), with the highest abundance of regenerating seedlings occurring at ridges (P<0.01). The ridge and gentle slope topography also supported higher species richness of regenerating seedlings than the steep slope and valley ones. The importance values of Machilus faberi, Cyclobalanopsis myrsinifolia, and Cyclobalanopsis glauca regenerating seedlings varied greatly across topographic types. These results demonstrate that both community structure and topographic factors jointly influence the abundance and spatial distribution of regenerating seedlings. Rich species composition, moderate community density, and abundant deadwood resources significantly promote the establishment and survival of regenerating seedlings. Ridge topography, characterized by abundant light availability and favorable moisture condition, enhances regeneration capacity of trees and supports high species diversity. The differential responses of dominant regenerating species to community and topographic attributes demonstrate species-specific ecological adaptation strategies.

Key words: subtropical northern margin, evergreen broad-leaf forest, dead tree, promoting effect, ecological strategy