Aims In subtropical forests, topographic heterogeneity drives ecosystem structure and species composition by regulating the available nutrients, water and light needed for tree growth. A gap in current research is the role of topographic heterogeneity in plant species diversity and distribution in monsoon evergreen broad-leaved forests. Our study aims to fill this gap, providing scientific grounds for the conservation of biodiversity through an exploration of floral structure and ecosystem development in monsoon evergreen broad-leaved forests.
Methods Within a 30 hm2 dynamics plot, we established 750 20 m × 20 m sample plots, using fuzzy C-mean clustering to classify different topographic types based on elevations, convexities, slopes, and aspects of each sample plots. We compared community composition and community species diversity between different topographic types, using Torus-translation tests to examine the relationship between floral species and topography.
Important findings We identified five distinct topography types: ridge (8.00 hm2), steep slope (6.04 hm2), less-steep slope (7.68 hm2), high plateau (2.76 hm2), and valley (5.52 hm2). We counted a total of 153 418 woody plant individuals with a diameter at breast height (DBH) ≥ 1 cm, belonging to 271 species, 179 genera and 79 families. Among the topographic types, we noted differences in species richness, plant density, proportion of different diameters, species diversity and the abundance of dominant species. When comparing species-area relationships between the five topographic types, we noticed that the ridge had the lowest number of species, while the valley had the highest. The cumulative species-individual relationships within the topographic types revealed that the ridge possesses the lowest cumulative rate. Of the 123 examined species, 67.5% were significantly related to at least one type of topography. Among species significantly related to topography, those species with significant negative correlation were more abundant in the ridge and steep slope topographic types. The opposite was true in steep slope, high plateau and valley. Based on our data, we determined that topographic heterogeneity contributed 7.8% to the maintenance of species diversity in our study area.