Connectivity of soil microhabitats via soil mixing and soil saturation; also a dive into the effects of anoxic conditions

This SRA submission included samples from two overlapping lab experiments that are in preparation for publication. One experiment explores the intersection of selection and dispersal that arises in field-moist versus saturated soil. We were interested in the effects of saturation because it applies selective pressure on soil communities but also changes soil pore connectivity, and thus is also expected to affect dispersal. This is a follow-up experiment to the soil mixing work that explored the effects of soil mixing on community composition and community assembly (West and Whitman, 2022), but here, instead of physically disturbing and mixing soil, we use saturation of the soil matrix to manipulate connectivity.In the other experiment, we incubated small soil samples and evaluated the effects of periodic disturbance via soil mixing on community composition and community assembly processes (e.g., selection and dispersal), including under 16 weeks of static anoxic conditions. We found that anoxic conditions generally decreased bacterial richness and suppressed the influence of mixing-driven selection. Consistent with our previous findings, increased mixing frequency homogenized bacterial communities and increased fast growth potential, regardless of oxygen regime. Further, we confirmed our hypothesis regarding a stronger relative importance of homogenizing dispersal under anoxic conditions, compared to homogeneous selection, which dominated under oxic conditions. Together, these results confirm that the generally disconnected and isolated nature of soil microhabitats is a fundamental driver of soil bacterial community composition and assembly processes across, supporting vast diversity across both well-aerated as well as anoxic soil conditions.