The conversion of primary forest lands to secondary forests and agricultural lands is the principal threat to tropical rainforests in Southeast Asia and elsewhere.

In contrast to the relatively large number of studies examining the soil microbial community across broad spatial ranges in terrestrial ecosystems, a comprehensive understanding of the distribution of the soil microbial community at a small scale of land-cover change is still lacking.  

Researchers from Xishuangbanna Tropical Botanical Garden (XTBG) compared soil bacterial and fungal communities from five different land-use types, that is, primary forest, secondary forest, pioneer plant community (dominated by Macaranga denticulata, a pioneer tree species), rubber plantation and Plukenetia volubilis plantation, in Xishuangbanna, a tropical region of China.

Their purpose was to elucidate the response of the soil microbial community structure and diversity relevant to forest secondary succession and agricultural lands. 

By using 16S rRNA and internal transcribed spacer (ITS) ribosomal DNA (rDNA) sequencing, the researchers compared bacteria and fungi community composition and diversity in soils between the three stages of forest succession and two agricultural drylands. 

Based on the high-throughput sequencing data, they found that even at a very small geographical scale (<4 km), tropical forest secondary succession and forest conversion to agricultural drylands strongly affected microbial community structures, especially for fungi. 

There is a strong degree of ecological differentiation in soil bacterial and fungal community composition in the forest secondary succession, exhibiting a unique dominant genus of bacteria and a site-specific fungal genus, but the microbial diversity may not always follow the same successional trajectories. 

Compared to the forests in the late successional stages (PF and SF), the agricultural drylands had higher bacterial richness but lower fungal richness, which was probably due to fertilisation and land-cover changes. 

The study entitled "Land-use type strongly shapes community composition, but not always diversity of soil microbes in tropical China" has been published in CATENA.