Strong conditionality in plant-fungal community assembly after soil inoculation in post-agricultural grasslands

Soil inoculation from plant species-rich into species-poor grasslands may enable the establishment of self facilitating networks between microbes and vegetation, thereby steering ecosystem development. We conducted a three-year experiment that covered a wide range of post-agricultural grasslands to determine how succession is affected by the interactive effects of edaphic properties, grass layer removal and hay or soil fragment transfer from a late-successional donor grassland.Soil inoculation generally impacted community assembly of vegetation and fungi, but not of prokaryotes. Effects were strongest when preceded by removal of the grass layer, indicating the importance of priority effects and dispersal limitation. Inoculation enabled the establishment of putative rhizosphere-associated fungal taxa, particularly from the families Helotiaceae, Glomeraceae and Archaeorhizomycetaceae. Nonetheless, effect sizes were mostly small, as was overall resemblance of the receptor grasslands to the donor. Fungal communities were primarily shaped by environmental filters and only reached a high resemblance to the donor in nutrient-poor sites. Shifts in the vegetation were strongest in those grasslands where the mycobiome more closely resembled that of the donor. Soil inoculation generally facilitates colonization by target plant and fungal communities, where establishment success of the former can be predicted by the latter, but the final outcome of succession is environmentally determined.

Automated summary

Soil inoculation from plant species-rich into species-poor grasslands can facilitate the establishment of self facilitating networks between microbes and vegetation, thereby influencing ecosystem development. The impact of inoculation on community assembly is stronger for vegetation and fungi than for prokaryotes. Environmental filters play a major role in shaping fungal communities, with nutrient-poor sites showing higher resemblance to the donor. The success of target plant colonization can be predicted by the establishment of fungal communities, but overall succession outcome is determined by environmental factors.