Litter, Root, and Mycorrhiza Input Affected Soil Microbial Community Structure in Schima superba Pure Forest in Subtropical China

During forest vegetation rehabilitation, changes in aboveground litter and underground root inputs affect soil microbial communities. Clarifying the effects of forest ecosystem carbon inputs on soil microbial community structure can provide a theoretical basis for the microbial driving mechanism of soil fertility evolution and ecosystem rehabilitation of vegetation rehabilitation in degraded red soil. Our research focuses on a Schima superba pure forest recovered from eroded and degraded red soil in a subtropical region. Five treatments were set as follows: control treatment (CT), mycorrhiza (M), root + mycorrhiza (RM), litter + root + mycorrhiza (LRM), and double litter + root + mycorrhiza (DLRM). We used Illumina HiSeq technology to study the effects of different organic carbon inputs on soil microbial community structure. The results showed that all organic carbon input treatments reduced the total population of soil bacteria by 55-79%; M, RM, and DLRM treatments increased the quantity of operational taxonomic units (OTUs) by 25-37%, ACE index by 25-34%, and Chao1 index by 28-39%. Acidobacteria, Proteobacteria, and Actinobacteria were the dominant bacteriophyta in the Schima superba pure forest soil. The relative abundance of Alphaproteobacteria decreased by 55% under LRM treatment, and Thermoleophilia increased by 81% under M treatment. The dominant fungal phyla were Basidiomycota and Ascomycota. RM, LRM, and DLRM treatments reduced the relative abundance of Sordariomycetes by 46-64% and increased the relative abundance of Mortierellomycetes by 251-615%. The order of effects of different organic carbon inputs on the bacterial community composition at the phylum level was LRM > RM > M > DLRM and that on the fungal community composition was DLRM > LRM and RM > M. Alphaproteobacteria, Thermoleophilia, Sordariomycetes, and Mortierellomycetes were the main microbial groups affected by changes in organic carbon inputs. Soil organic carbon and total nitrogen were the key factors affecting the change of Mortierellomycetes. The bacterial community mainly affected the activity of soil acid invertase, while the fungal community affected the activities of various enzymes, with positive or negative effects. We concluded that the organic carbon inputs changed the species and quantity of soil microorganisms in the Schima superba forest, and the influence of organic carbon input on the fungal community structure was greater than that of bacteria.