Associations between plant composition/diversity and the abiotic environment across six vegetation types in a biodiversity hotspot of Hainan Island, China

Aims Exploring the associations between vegetation and abiotic environments might increase our understanding of biodiversity formation mechanisms. Here, we explore variation in plant composition/diversity and their abiotic determinants across six vegetation types in a biodiversity hotspot of Hainan Island, China. Methods We established twelve 1-ha permanent plots, two in each of the six old-growth forest types. All woody stems (dbh ≥ 1 cm) and six soil and two microclimatic factors were measured. Associations between the abiotic factors and plant composition/diversity were analyzed by a spatial regressive model. Results Plant diversity/composition changed with forest types. The key factors correlated with species composition in deciduous monsoon forest were canopy openness and soil water content. Soil total nitrogen and pH were the vital determinants of diversity in coniferous forest. Soil water content, phosphorus and canopy openness were associated with higher diversities in lowland- and montane- rain forests. Soil organic matter and pH were the major factors influencing composition in the montane evergreen forest, whereas air temperature and soil total nitrogen were associated with the lowest diversity of the stunting statured montane dwarf forest. Conclusions Variation patterns of plant composition/diversity across different forest types were closely associated with the changes in the six soil and two microclimatic factors within each forest.