Effects of plant neighborhood on arbuscular mycorrhizal fungal attributes in afforested zones

Arbuscular mycorrhizal (AM) fungi are an important determinant of plant performance, and conversely their community composition greatly depends on host plants and their neighbors. Understanding how the interaction of host plants and their neighbors affects AM fungal communities in afforested zones is of primary interest in forest ecology. We sampled roots and rhizosphere soils in monocultures and mixtures of black locust (Robinia pseudoacacia) and oriental arborvitae (Platycladus orientalis) to define AM fungal colonization level, spore density and communities using 454 sequencing. Neighboring oriental arborvitae only affected AM fungal community in black locust rhizosphere. For oriental arborvitae, however, growing in a mixture with black locust changed AM fungal colonization, sporulation and communities in the roots and rhizosphere. In particular, neighboring black locust modified the rhizosphere- and root-inhabiting AM fungal pool through improving soil NO3-N and water contents and reducing soil catalase activity, and the modification in the root AM fungal resource, especially the Glomus and Rhizophagus genera, further affected AM fungal colonization and sporulation under oriental arborvitae. All the results presented here suggest that both hosts and neighbors can largely affect AM fungal attributes mainly through changing soil nutrient levels and enzyme activity, whereas the reciprocal effects are not always symmetric.