Effects of plant diversity, soil microbial diversity, and network complexity on ecosystem multifunctionality in a tropical rainforest

Plant and soil microbial diversity are important driving factors in sustaining ecosystem multifunctionality (EMF) in terrestrial ecosystems. However, the relative importance of plant diversity, soil microbial diversity, and network complexity on EMF is poorly understood in a tropical rainforest environment. This study quantified multiple ecosystem functions, including soil organic carbon stock, soil nutrient cycling, biomass production, water regulation, and the EMF in a tropical rainforest. We analyzed the effects of plant diversity, soil microbial diversity, network complexity, and environmental factors on the EMF in a tropical rainforest in Xishuangbanna, south Yunnan Province, China. We assessed the relative importance of plant and soil microbial diversity, soil microbial network complexity, and environmental factors on EMF. Our results exhibited that EMF decreased with increasing liana species richness, soil fungal diversity, and soil fungal network complexity, following a trend of initially increasing and then decreasing with soil bacterial diversity while increasing with soil bacterial network complexity. Soil microbial diversity primarily affected soil nutrient cycling, while plant species richness significantly and positively affected soil nutrient cycling. Additionally, liana species richness had significant negative effects on soil organic carbon stocks. The random forest model suggested that liana species richness, soil bacterial network complexity, and soil fungal network complexity were the most critical factors sustaining EMF. The structural equation model revealed the significant and direct positive influence of soil bacterial network complexity and tree species richness on EMF, while liana species richness significantly negatively affected EMF. We also observed that soil microbial diversity indirectly affected EMF through soil microbial network complexity. Soil bulk density had a significant and negative effect on liana species richness, thus indirectly influencing EMF. Therefore, liana species richness was the main indicator of sustaining EMF in a tropical rainforest, while soil bacterial diversity was the primary driving factor. Our findings provide new insights into the relationship between biodiversity and EMF in tropical rainforest ecosystems and contribute to maintaining the ecosystem functions necessary for anthropogenic interests.