Abstract:Different perturbation regimes, including disturbance caused by cultivation or the process of natural restoration, can have significant effects on the soil bacterial community in marshland. In this study, we investigated the relationship between soil bacterial community composition and perturbation in marshland to quantify the extent of such disturbance-related changes in northeast China. We assessed the diversity of bacterial communities in twelve samples of marsh soil collected from pristine marsh, neighboring cropland, and a wetland restoration area. High-throughput sequencing of a bacteria-specific genomic sequence, the internal transcribed spacer (16S rRNA) region, was used to identify bacterial taxa. We obtained 358,737 sequences that represented 2263 bacterial OTUs across the three types of sampling sites. Of these, 1411 OTUs occurred at all three site types, 99 were shared between cultivated land and pristine marshland, 322 were shared between cultivated land and wetland converted from cropland, and 126 were shared between pristine marshland and wetland converted from cropland. All sites also hosted unique fungal OTUs, with 218 OTUs exclusive to cultivated land, 52 exclusive to pristine marshland, and 35 exclusive to wetland converted from cropland. Sequences were affiliated to 36 different phyla throughout the dataset. Sequence abundance showed that members of the Proteobacteria were more frequently identified in all soil samples than Acidobacteria, and included members of Chloroflexi, Actinobacteria, Bacteroidetes, Firmicutes, Gemmatimonadetes, Verrucomicrobia, Nitrospirae, Saccharibacteria, and Chlorobi, which represented an overwhelming proportion of the soil bacterial communities with an average relative abundance of > 1%, and another 25 phyla with an average relative abundance were <1%. The dominant phyla that showed the greatest variation among habitat types (> 1% of the average relative abundance) were Gemmatimonadetes (P < 0.01), Bacteroidetes (P < 0.01), Firmicutes (P < 0.01), and Chlorobi (P < 0.01). The soil bacterial community diversity decreased from a maximum in cultivated land, through the wetland restoration area, to a minimum in pristine marshland. Redundancy and correlation analyses demonstrated that chronic disturbance through cultivation, especially dry cultivation, significantly altered the bacterial community composition of marsh soil. The α-diversity of the soil bacterial community was most affected by soil moisture, soil pH, total carbon, soil organic carbon, soil dissolved organic carbon, available nitrogen, microbial biomass of carbon, and microbial biomass of nitrogen. Meanwhile, the soil bacterial community composition was significantly affected by soil moisture, soil pH, total carbon, soil organic carbon, and soil dissolved organic carbon. Overall, the results from our study showed that the state of soil carbon and nitrogen is affected by the disturbance by agricultural cultivation, causing long-term accumulated soil nutrients to become available as an energy source that can be rapidly mineralized by soil bacteria. In addition, our results also indicate that cultivation and natural restoration influenced the bacterial community structure and diversity. Natural restoration can significantly enhance the recovery of bacterial diversity; however, once the composition of the marshland bacterial community has been altered by cultivated disturbance, it might be difficult to restore to its original state. These findings highlight the importance of effectively managing the soil bacterial community to maintain a naturally functioning soil ecosystem.