Quantitative estimation of stochastic and deterministic processes for soil prokaryotic community assembly in the Yellow River floodplain

The floodplain ecosystem plays an important role in the mediation or regulation of regional ecological functions, and is the heart of ecosystem functions based on soil microbial communities. In the present study, we investigate the patterns and assembly processes of soil microbial communities along nine profile depths (up to 280 cm in depth) of three stages of floodplain community succession (channel bar, newly deposited river beach and tender floodplain) and farmland in the floodplain of the lower Yellow River. Generally, the bacterial community in agricultural soil had the highest diversity, whereas the archaeal community in the tender floodplain had the highest diversity. Compared to bacteria, the co-occurrence network of archaea was more complex and stable and had high connectivity. Our data suggest that the resistance of bacteria and archaea to environmental changes in deep soil was higher when compared to that in surface soil. Furthermore, stochastic and deterministic processes acted concurrently to regulate the assembly of the soil microbial community in the floodplain ecosystems. However, the relative contributions of the stochastic process and deterministic process are different between the bacterial community and the archaeal community. The lowest contribution of the stochastic process in the bacterial community was in the subsoil, whereas in the archaeal community, it was the opposite. For ecological selection, bacterial communities in different soil profiles, in the succession stages and in the farmland, were mainly selected through homogeneous selection, whereas archaeal communities were selected through heterogeneous selection. Compared with the three floodplain succession stages, the microbial communities of agricultural lands were more assembled by deterministic processes. Highlights Stochastic and deterministic processes act concurrently to regulate the assembly of soil microbial community in the floodplain ecosystems. The assembly of the bacterial community was mainly affected by the homogeneous selection. The archaeal community was mainly affected by the heterogeneous selection. The microbial communities of agricultural lands were more assembled by deterministic processes.