Impact of tropical forest conversion on soil bacterial diversity in tropical region of China

Abstract

In Xishuangbanna, a China's tropical region, monoculture rubber plantations have expanded dramatically over the past two decades. However, the effect of conversion of tropical forests to rubber plantations on the soil microbial compositions and diversity remains poorly understood. This study investigated the bacterial diversity and biomass in rubber plantations, secondary tropical forest and tropical seasonal rainforest in Xishuangbanna, southwest China, based on an analyses of PCR-amplified 16S rRNA genes. Our findings revealed that soil of rubber plantation was different from secondary tropical forest and tropical seasonal rainforest in bacterial compositions at phylum, family as well as OTU (Operational Taxonomic Units) levels. The most abundant phylum in rubber plantations was Firmicutes, however, in secondary tropical forest and tropical seasonal rainforest it was Proteobacteria. In both dry season and rainy season, diversity indices of rubber plantations were significantly higher than those of secondary tropical forest and tropical seasonal rainforest, indicating that bacterial diversity increased after conversion. However, the total microbial biomass carbon (MBC) decreased after conversion. RDA results showed that soil pH and total phosphorus maybe the two most important factors controlling bacterial communities, and explained 49.2% and 38.1% of total variance of phylum compositions, respectively. Management practices, especially the application of fertilizers with phosphorous would thus probably influence the taxonomic composition and diversity of bacterial communities in this region.