The importance of local climate and biodiversity in tropical forest's ability to provide critical ecosystem services is well documented, whereas the relationship among local climatic factors and biodiversity with soil ecosystem functions largely remain unclear. We investigated the importance of local rainfall regime and indicators of plant (tree, herb, and shrub) diversity (richness and abundance) on soil ecosystem functions in two tropical forest ecosystems of north-east Bangladesh. We considered six soil parameters, i.e. soil water regulation (SWR), soil physical stability (SPS), soil microbial habitat (SMH), soil pH (pH), medium of plant growth (MPG), and soil aggregate stability (SAS) as indicators of soil ecosystem functions. Our study finds four rainfall parameters having significant (p < 0.05) positive effects on soil water regulation, soil physical stability, microbial habitat, soil pH, medium of plant growth, and soil aggregate stability. Tree species abundance had positive effects on SPS (p < 0.001) and MPG (p < 0.05), while tree species richness had negative effects on SMH (p < 0.001) and MPG (p < 0.01). Soil aggregate stability was negatively (p < 0.05) affected by tree species abundance, whereas tree species richness positively (p < 0.0001) affected SAS. We found no significant effects of tree species abundance and richness on pH and SWR. The abundance of herbaceous species had positive impacts on MPG (p <0.01) and negative impact on SAS (p < 0.001). In contrast, the richness of herbaceous species had significant negative effects on SMH (p < 0.01) and SPS (p < 0.05). Shrub abundance had no significant effects on six soil ecosystem functions in our study sites, but shrub species richness had a significant (p < 0.05) negative effect on SPS. Our study provides critical insights into the synergistic role of local climate and biodiversity on soil ecosystem functions that can guide actions to restore degraded soils in tropical forest ecosystems.
