Soil bacterial community assembly during succession

Understanding the contribution of ecological processes structuring microbial communities and predicting their dynamics are ongoing challenges in ecology. To address these challenges, this thesis focused on the interplay of selection, dispersal and ecological drift mediating soil bacterial community assembly during succession. The results revealed a higher temporal turnover of RNA-inferred communities in comparison with DNA-inferred communities, as RNA-inferred communities were more closely associated with selection driven by environmental variations than DNA-inferred communities. Greater attention was also given to members of the rare biosphere (i.e., a collection of low abundance taxa in a community) due to their high diversity and relevance for ecosystem functioning. The findings show that the rare biosphere of soil bacterial communities was composed of different types of rarity. In particular, selection driven by stringent environmental conditions explains the prevalence of permanently rare taxa, whereas selection driven by environmental variations explains the dynamics of conditional rare taxa. Furthermore, this thesis investigated the influence of dispersal through sea water inundation on soil bacterial communities from the early and late stages of succession and found that a stronger influence of sea water inundation on the rare biosphere of soil bacteria communities at the early successional stage rather than the late stage. Altogether, this thesis provides microbial ecologists with more insights on how bacterial communities are assembled during ecological succession, and how the bacterial rare biosphere is structured by a dynamic interplay of quantifiable ecological processes.