Distinct patterns of abundant and rare subcommunities in paddy soil during wetting-drying cycles

Wetting-drying cycles typically result in a wide range of soil moistures and redox potentials (Eh) that significantly affect the soil microbial community. Although numerous studies have addressed the effects of soil moisture on soil microbial community structure and composition, the response of active microbes to the fluctuation in soil Eh is still largely unknown; this is especially true for the ecological roles of abundant and rare taxa. To explore the dynamics of active and total microbial communities in response to wetting-drying cycles, we conducted a microcosm experiment based on three wetting-drying cycles and 16S rRNA transcript (active) and 16S rRNA gene (total) amplicon sequencing. We found that both active and total microbial communities during three wetting-drying cycles were clustered according to the number of wetting-drying cycles (temporal factor) rather than soil moisture or Eh. Dynamics of the active microbial community, however, were redox dependent during the first wetting-drying cycle. In addition, rare taxa in the active microbial community exhibited more obvious differences than abundant ones during three wetting-drying cycles. Species turnover of abundant and rare taxa of total and active microbes, rather than species richness, explained the highest percentage of community variation. Rare taxa exhibited the most marked temporal turnover during three wetting-drying cycles. Members of Rhodospirillaceae were the major contributor to the resilience of abundant taxa of active microbes during the first wetting-drying cycle. Overall, these findings expand our current understanding of underlying assembly mechanisms of soil microbial communities responding to wetting-drying cycles.