Soil conditions are a more important determinant of microbial community composition and functional potential than neighboring plant diversity

Replanting is an important tool for ecological recovery. Management strategies, such as planting areas with monocultures or species mixtures, have implications for restoration success. We used 16S and ITS rRNA gene amplicon sequencing and shotgun metagenomics to assess how the diversity of neighboring tree species impacted soil bacterial and fungal communities, and their functional potential, within the root zone of mānuka (Leptospermum scoparium) trees. We compared data from monoculture and mixed tree species plots and confirmed that soil microbial taxonomic and functional community profiles significantly differed (p < 0.001). Compared to the diversity of neighboring tree species within the plot, soil environmental conditions and geographic distance was more important for structuring the microbial communities. The bacterial communities appeared more impacted by soil conditions, while the fungal communities displayed stronger spatial structuring, possibly due to wider bacterial dispersal. The different mechanisms structuring bacterial and fungal communities could have implications for ecological restoration outcomes.