Recent evidence suggests that, similar to larger organisms, dispersal is a key driver of microbiome assembly; however, our understanding of the rates and taxonomic composition of microbial dispersal in natural environments is limited. Here, we characterized the rate and composition of bacteria dispersing into surface soil via three dispersal routes (from the air above the vegetation, from nearby vegetation and leaf litter near the soil surface, and from the bulk soil and litter below the top layer). We then quantified the impact of those routes on microbial community composition and functioning in the topmost litter layer. The bacterial dispersal rate onto the surface layer was low (7900 cells/cm²/day) relative to the abundance of the resident community. While bacteria dispersed through all three routes at the same rate, only dispersal from above and near the soil surface impacted microbiome composition, suggesting that the composition, not rate, of dispersal influenced community assembly. Dispersal also impacted microbiome functioning. When exposed to dispersal, leaf litter decomposed faster than when dispersal was excluded, although neither decomposition rate nor litter chemistry differed by route. Overall, we conclude that the dispersal routes transport distinct bacterial communities that differentially influence the composition of the surface soil microbiome.

最近的证据表明，与较大的生物体类似，扩散是微生物组组装的关键驱动因素；然而，我们对自然环境中微生物扩散的速率和分类组成的了解是有限的。在这里，我们描述了细菌通过三种传播途径（从植被上方的空气，从附近的植被和土壤表面附近的落叶，以及从表层以下的大块土壤和垃圾）扩散到表层土壤中的速率和组成。然后，我们量化了这些路线对微生物群落组成和最顶层垃圾层功能的影响。表面层的细菌扩散率很低（7900 个细胞/cm ²/天）相对于居民社区的丰富程度。虽然细菌以相同的速度通过所有三种途径扩散，但只有从土壤表面上方和附近扩散会影响微生物组的组成，这表明扩散的组成而不是速率会影响群落组装。扩散也影响了微生物组的功能。当暴露于扩散时，凋落物分解速度比排除扩散时更快，尽管分解率和凋落物化学都因途径而异。总的来说，我们得出的结论是，传播途径运输了不同的细菌群落，这些细菌群落对表层土壤微生物组的组成有不同的影响。