Abstract: Objective This study aims to investigate the effects of changes in litter and root carbon input on the structure and diversity of soil microbial communities in a mature Pinus elliottii plantation, so as to provide a theoretical basis for the sustainable management of P. elliottii plantation. Method The mature P. elliottii plantation at the northern of subtropical area in China was selected as the research object, and five treatments were set up in situ, including control (CK), root removed (NR), litter removed (NL), double litter (DL), and root and litter removed (NRNL). After 4 years of those treatments, the high-throughput sequencing technology was used to sequence the 16S rDNA of bacteria and the ITS genes of fungi in the 0-20 cm soil layer, and then the effects of carbon input change on the composition and diversity of soil bacterial and fungal communities were analyzed in combination with the soil physicochemical characteristics. Result 1) A total of 3 496 bacterial operational taxonomic units (OTUs) were obtained through soil sequencing, belonging to 30 phyla and 186 genera, and the dominant phyla were Acidobacteria, Proteobacteria, and Chloroflexi, and 2 547 fungal OTUs belonging to 13 phyla and 248 genera, and the dominant phyla were Basidiomycota, Ascomycota and Mortierellomycota. Compared with the control treatment, the root removal treatment significantly reduced the relative abundance of Proteobacteria and Verrucomicrobia (P<0.05), whereas carbon input alteration had no significant effect on soil fungal community structure. 2) Compared with the control treatment, root removal significantly reduced the Alpha diversity index of soil bacterial community (P<0.05), and the double litter treatment significantly decreased the bacterial Pielou evenness index and ACE index. Root removal, and simultaneous root and litter removal treatments significantly reduced the soil fungal ACE index. 3) Redundancy analysis showed that soil dissolved organic carbon (DOC) and nitrate nitrogen (NO₃^–-N) contents were significantly positively related with the bacterial community structure of Proteobacteria. Soil pH-value was negatively related with the fungal community of Mortierellomycota, but was significantly positively related with the relative abundance of Mucoromycota.Conclusion The root removal and double litter input significantly alter the soil bacterial community structure and Alpha diversity index, while root removal, and both root and litter removal treatments significantly alter the soil fungal ACE index. DOC and NO₃^–-N contents may be the determining factors of soil bacterial community structure in P. elliottii plantation, while soil pH value and DON content may be the determining factor of the soil fungal community.

Key words: litter, root, bacterial and fungal community, Alpha diversity index, Pinus elliottii plantation