LAUSR

Abstract Sulfate reduction is an essential process in the biogeochemical sulfur cycle in soils. It is mainly driven by dissimilatory sulfate-reducing bacteria (DSRB). The responses of the DSRB community in a rapeseed-rice rotation system to the environmental variability caused by the shift from the upland to the paddy stages, and the effects of the long-term straw returning on this shift remains unclear. We surveyed the sulfate reducing potential (SRP) and the structure of the DSRB community by high-throughput sequencing that targeted dsrB (and the xenologous dsrB) in soils. The SRP, ranging from 1.2 to 5.8 μmol d−1 d w g−1, was increased in the paddy stage, and it was likely to be enhanced by the long-term straw returning. Highly abundant DSRB optimal taxonomic units (OTUs) were found to be affiliated with the Nitrospirae supercluster (including the uncultured DsrAB lineage WX, lineage 10, and an unknown clade with GU372064), the Environmental supercluster 1 (including the uncultured DsrAB lineage 8 and an unknown lineage related to EF065019), and the Firmicutes group (including the uncultured DsrAB lineage 6 and an unknown lineage between the uncultured DsrAB lineages 2 and 3). The environmental transformation from the upland to the paddy stages led to a decrease in the α-diversity and the number of detectable OTUs. The abundance of a few dominant DSRB OTUs was changed by either the environmental transformation from the upland to the paddy stages or the effects caused by the long-term straw returning. In this study, the changes in the DSRB community structure correlated with the decrease in soil pH and total phosphorus content, and the increase in available sulfate and moisture contents.