Soil, Topography and Forest Structure Shape the Abundance, Richness and Composition of Fern Species in the Fragmented Tropical Landscape of Xishuangbanna, Yunnan, China

Abstract

Understanding how forest fragment size, topography, forest structure, and soil properties affect plant diversity remains a crucial question in conservation biology, with ferns often being understudied. To address this knowledge gap, we surveyed the abundance, species richness, and composition of ferns in a tropical landscape in south China using 75 sites in 42 forest fragments. We then used a multi-model inference approach to assess whether fern abundance, richness, and composition were better explained by (a) fragment size, (b) topography (slope, aspect), (c) forest structure (tree basal area, light availability), or (d) soil properties (pH, Carbon, Nitrogen, Phosphorous, Calcium, Magnesium, water availability, and proportion of clay, silt, and sand). We also conducted a nestedness analysis to examine whether the composition of the fern communities in smaller fragments (0.4–1 km²) differed or represented a subset of the communities found in larger fragments (e.g., >10 km²). We found that (a) fern abundance was mostly influenced by soil properties, slope, and aspect, (b) fern species richness by soil properties and slope, and (c) fern species composition by forest structure, specifically, tree basal area. We also found that fern species composition was not nested in the landscape, suggesting that smaller forest fragments had different communities from larger fragments. Our results suggest also that soil properties play an important role in maintaining fern abundance and diversity and therefore protecting soil can help conserve ferns in fragmented landscapes.