Soil pore space heterogeneity increases microbial community stability to short-term flooding

We conducted a laboratory incubation to determine if greater soil pore heterogeneity supports more microbial stability during and after experimental flooding and how this is modulated by land use. We collected intact agriculture and grassland soil and kept half of the soil cores intact as our heterogenous treatment and sieved the other half for our homogenous treatment. Soil cores were flooded for three weeks followed by drying to pre-flood moisture. Compared to the homogenized soils, the intact heterogeneous soils exhibited either an increase or stability in biomass, enzyme activity, heterotrophic respiration, and bacterial community diversity over the course of the flood event. Our results suggest that more heterogenous soils protect resources and well-adapted communities in the case of the grassland, or functionally diverse microbial communities, in the case of the agricultural soil, that can be dispersed during and after the flood event to furnish a more stable community. Our study provides strong evidence for microbial functional and compositional stability in more structurally heterogenous soils, suggesting soil physical structure is an important factor in determining microbial flood responses, and in this case in minimizing changes to the microbial communities.