Deposition of eroded soil significantly increases bacterial community diversity and soil multifunctionality in a Mollisol agricultural ecosystem

Topography plays a significant role in shaping soil biogeochemical cycling through its influence on the composition and function of bacterial communities. However, little is known about how the community composition of soil bacteria is interlinked with soil multifunctionality across an eroding landscape. Herein, understanding the relationship between microbes and soil multifunctionality is crucial for promoting sustainable agriculture. In this study, we examined microbial responses to topographic gradients (flat slope, middle slope, lower slope, valley) in a Mollisol sloping landscape. The poorly drained sites of the lower slope and valley exhibited a higher richness of species and greater diversity in bacterial community at the operational taxonomic unit level compared to the flat slope. Notably, changes induced by topography in soil bulk density, moisture, soil organic carbon, total nitrogen, dissolved organic carbon, nitrates, and ammonium were significantly correlated with bacterial taxonomy and functional composition. Soil multifunctionality was 8.98–14.31% greater in the valley than in other topographic positions. In terms of the relative abundance of soil bacteria, the subsets (OTUs) of Chloroflexi, Proteobacteria, and Firmicutes were identified as key contributors to soil multifunctionality. Topographic effects on bacterial taxonomy and functions largely depend on indices related to soil nitrogen. Overall, our study highlights that erosion processes and land management dramatically changed the characteristics of the bacterial community, bacterial potential functions, the responses of soil multifunctionality, and their relationship via altering the soil micro-environment.