The response of the soil bacterial community and function to forest succession caused by forest disease

Forest succession is a key driver of plant communities and understanding succession is central to forest restoration. Currently, the information on the response of the microbial community to the forest succession process, however, is limited. In the present study, we investigated the dynamics of the soil bacterial community in three forest types undergoing succession caused by pine wilt disease, representing the initial pine forest, gradual mixed pine and broadleaved forest, and eventual broadleaved forest, using Illumina MiSeq coupled with Functional Annotation of Prokaryotic Taxa (FAPROTAX) analysis. The results showed that the soil pH, contents of soil organic carbon (SOC) and soil total nitrogen (TN) increased after the occurrence of initial succession and differed among the forest sites. The mixed pine forest had significantly higher bacteria biomass (p < 0.05), whereas, the total microbial biomass did not differ during the succession. The bacterial community diversity and richness increased significantly following the succession process (p < 0.05). Proteobacteria, Actinobacteria, Acidobacteria and Bacteroidetes were the dominant phyla across the succession, in which the abundance of Bacteroidetes significantly increased (p < 0.05), whereas, Planctomycetes, WPS-2 andBurkholderdecreased in abundance after succession occurred (p < 0.05). The three forests formed distinct bacterial community structures during the succession (p < 0.05), whereas, only two functional structures were clustered, in which the mixed and pure broadleaved forest did not differ. The dominant functional groups involved in the C cycle in the initial pure pine forest were replaced gradually by the groups involved in N and S cycles following the subsequent succession. The soil pH, soil TN and SOC were the most important factors affecting the bacterial community and functional structures during the succession. These results indicate that the bacterial community and function shift drastically in the early stages of succession, which reflects the changes in ecological environment caused by succession. The findings provide useful information to better understand the response of microbes to natural forest disturbance and highlight the importance of microbes during forest succession. A freePlain Language Summarycan be found within the Supporting Information of this article.