Bacterial community diversity for three selected land use systems as affected by soil moisture regime

Abstract

Despite their important role in soil nutrient cycling, soil bacterial communities' response to land management practices and soil hydrologic fluctuations are not sufficiently studied. The effects of land use and soil moisture regime on soil bacterial community structure and diversity in the Missouri River Floodplain have been investigated in this study. Three land use systems represented riparian forest (RF), pecan (Carya illinoinensis) orchard/hay agroforestry system (AF), and row crop corn [Zea mays L.]/soybean [Glycine max (L.) Merr.] agriculture system (AG). Microbial diversity indices and the abundance of selected bacterial phyla were investigated in bulk soil samples by performing 16 s rRNA amplicon sequencing. Soil samples were collected from three selected land use systems in September 2020 and May 2021. To simulate the hydrological dynamics of the riparian systems, intact soil cores were subjected to two different soil moisture regimes: saturated (FD) and alternately saturated and field capacity (FL) for 8 weeks of incubation. A control sample was maintained at field capacity for the entire duration of the experiment. Soil physicochemical properties substantially differed among land use. Soil organic matter (OM%) was significantly greater in AF and RF than in AG. Proteobacteria, Actinobacteriota, and Acidobacteriota were found to be the most dominant bacterial phyla across all samples. The bacterial richness and Shannon indices were not considerably different among land use systems. Soil FD conditions considerably increased the abundance of Actinobacteriota in AF soils. The abundance of these phyla was strikingly higher in AF with the greatest organic matter relative to AG and RF under all three water regimes. Further work may be needed to assess the effects of hydrological events on floodplain soils' microbial community indices.