ABSTRACT. Using a new DNA hybridization technique that does not require culturing, we compared the species composition of natural planktonic bacterial assemblages before and after confinement in 20 1 containers for ca 2 d Although confinement is known to cause species shifts, possibly by stimulating growth of certain types of cells near the container wall, we found that such shifts were minor; 5 to 15 % of the communities had changed during confinement. The greatest shifts occurred in the samples that had the fastest bacterial growth rate measured by [Hlthymidine incorporation. Despite the minor changes in species composition, the fraction of the cultivable cells (colony forming units; CFU) increased 4-to 23-fold, but amounted to < 2 % of total counts even after confinement Interestingly, CFU on unsupplemented media increased more rapidly than CFU on supplemented media. Comparisons to previous studies suggest that our use of large (20 1) containers and our efforts to minimize contamination with organic material may have decreased the 'wall effect.' We conclude that confined microbial communities did not undergo drastic changes of species composition in 2 d in 20 1 containers.

Resistance is the capacity for a community to remain unchanged, and resilience the capacity to return to an original state, in response to disturbance. Increasing species richness may increase both dynamics. In a long-term agricultural field experiment incorporating conventional (CON), integrated (INT), conservation (CA) and organic (ORG) cropping systems, the effects of crop harvest and fallow period on the disturbance of prokaryote, fungal and arbuscular mycorrhizal fungi (AMF) communities were investigated. It was hypothesised that: 1) change in composition observed over time due to disturbance differs between systems; 2) species-rich prokaryote communities demonstrate greater resistance and resilience than speciespoor AMF; 3) key functional groups are more stable under systems that promote richness. Prokaryote community structure shifted over the growing season, forming distinct saprotroph-and rhizosphere-dominated communities over-winter and under mature crops, respectively. Management did not alter their response to disturbance, and they demonstrated the highest resistance/resilience. Fungal richness and resistance/resilience was highest under CA with a unique composition. AMF richness and resistance/resilience was lowest under CON with a fractured composition.Prokaryote plant-growth promoters and saprotrophs, but not ammonia oxidisers and methylotrophs, were stable functional groups. Diverse, cosmopolitan soil fungal genera were stable, but most were not. Glomus AMF were stable, while most other genera were stable under CA and ORG. These results demonstrate that practices promoting richness increase the stability of soil fungal communities, while prokaryote communities are more dynamic in structure. This may have consequences for the stability of fungal-and specific prokaryote-driven functions in response to crop harvest. 2015; Banerjee et al., 2019) and shift communities to favour Proteobacteria over