Plant–soil feedbacks between arbuscular- and ecto-mycorrhizal communities

AbstractSoil microbiomes of adult trees exert species-specific effects on the survival and growth of seedlings1-6, yet empirical evidence that such plant–soil microbiome interaction drives seedling community assembly remains scarce. Here we show that mycorrhizal fungal communities determine seedling community assembly by controlling how resident plant communities alter the growth of newly established seedlings. We reciprocally introduced seedling communities of arbuscular-and ecto-mycorrhizal plant species to replicated mesocosms to follow the effects of mycorrhizal type match/mismatch with resident plant communities on seedling growth rates. The growth rates of recruited seedlings were generally higher under resident trees of the same mycorrhizal types than under those of different mycorrhizal types, generating positive plant–soil feedbacks through mycorrhizal-type matching. Such positive effects of matching were linked with seedlings’ greater acquisition rates of mycorrhizal symbionts from matched resident plants than from mismatched plants, and such linkage was pronounced for ecto-mycorrhizal plant species. In contrast, under the condition of mycorrhizal-type matching between resident plants and seedlings (i.e., within-mycorrhizal-type comparison), plant–soil feedback effects varied considerably in their sign and strength among resident–seedling species combinations. Consequently, the assembly of a temperate tree seedling community is driven by a combination of species-specific plant–soil feedbacks and the match/mismatch of mycorrhizal type between resident plants and seedlings.