Abstract
Knowledge regarding changes in soil microbial communities with forest succession is vital to understand soil microbial community shifts under global change scenarios. The composition and diversity of soil microbial communities across a subalpine forest successional series were therefore investigated in the Wanglang National Nature Reserve on the eastern Qinghai-Tibet Plateau, China. The calculated diversity indices of soil bacteria (8.598 to 9.791 for Shannon-Wiener, 0.997 to 0.974 for Simpson, 4131 to 4974 for abundance-based coverage estimator (ACE) and 3007 to 3511 for Species richness indices), and ACE (1323 to 921) and Species richness (1251 to 879) indices of soil fungi decreased from initial to terminal succession stages, but Shannon-Wiener and Simpson of soil fungi indices varied slightly with forest succession. Meanwhile, the composition and structure of soil microbial communities varied markedly with forest succession. The relative abundance of the dominant bacterial phyla (Acidobacteria, Firmicutes and Actinobacteria) and fungal taxa (Mortierellomycota, Rozellomycota and unassigned phylum clade GS01) varied considerably with forest succession. However, regardless of successional stage, Proteobacteria and Acidobacteria dominated soil bacterial communities and Ascomycota and Basidiomycota dominated soil fungal communities. Moreover, the changes in soil microbial diversity with forest succession were significantly affected by soil pH, soil organic carbon, soil temperature, altitude, and non-woody debris stock. Importantly, soil pH was the dominant driver of soil microbial community shift with forest succession. In conclusion, the forests at different succession stages not only conserve same microbial populations, but also nurse unique microbial diversity across the forest succession series; and the biodiversity of soil bacterial and fungal communities has differential responses to forest succession.
Highlights
redundancy analysis (RDA) showed that soil pH had the greater effect on the differences in the composition of soil communities across the forest successional series, while non-woody debris stock was correlated with only the composition of soil bacterial community, partly supporting our third hypothesis
Our observations showed that the composition of soil microbial communities across the successional series was significantly affected by forest variables, which was consistent with the findings of previous studies [61,74,75]
Our results found that the composition of soil bacterial communities, but not the composition of soil fungal communities, was significantly correlated with Soil organic carbon (SOC) and non-woody debris stock across the forest successional series, which was inconsistent with the findings of some previous studies [90,91]
Summary
Investigations on the changes in soil microbial community structure and diversity with environmental factors can provide key evidence for understanding the mechanisms driving bioelement cycles, managing forest ecosystems and conserving soil biodiversity. The present consensus is that the composition, structure and diversity of soil microbial communities can be driven by combinations of biotic and abiotic factors [4,5,6], making the responses of soil microbial communities to environmental changes relatively complex. The changes in forest community structure could simultaneously alter soil properties [7], microclimate [8], and the input and qualities of above- and below plant biomass [9,10]; these changes could lead to soil microbial community shifts. The vast majority of Actinobacteria are important saprophytes capable of breaking down a wide range of plant and animal debris in the process of decomposition [13]
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