Infiltration Berm Physicochemical Properties Influence Soil Microbial Activity and Community Composition

Soil infiltration berms are green infrastructure that captures and decelerates runoff to enhance groundwater recharge. The increased infiltration can alter microhabitats within the soil by increasing the quantity and retention time of soil water. In this study, we investigated the soil physicochemistry, microbial activity, biomass carbon pool, and bacterial/archaeal and fungal community composition compared to an undeveloped natural area. We sampled mineral topsoils from spring 2021 to spring 2022 for a total of 5 sampling events in central Texas. Soil microbial activity was measured via targeting soil dehydrogenase activity (DHA). Microbial biomass carbon (MBC) was measured after chloroform fumigation and non-purgeable organic carbon was measured in extractants. We also determined bacterial/archaeal and fungal microbiomes via high-throughput 16S rRNA and ITS2 gene sequencing. Microbial alpha and beta diversity and the factors that shaped them were investigated with constrained multivariate analyses. The berm soils had greater DHA (p <0.001) than the undeveloped soil, but MBC was equivalent across land managements and seasons. Both land management types hosted unique community compositions (p<0.001) but were both dominated by relevantly few taxa. The infiltration berms soils' lower nutrients and higher water content compared to the undeveloped soils altered the taxonomic structures within the soil. The difference in microbial activity and biomass suggests a difference in carbon use by microorganisms within the undeveloped and berm soils.