Land-use conversion from open field to greenhouse cultivation differently affected the diversities and assembly processes of soil abundant and rare fungal communities.

Soil fungal communities, consisting of a few abundant taxa but many rare taxa, play critical roles in terrestrial ecosystem functioning. However, little is known about ecological processes governing the assembly of abundant and rare sub-communities in response to agricultural intensification, which can threaten soil biodiversity. Here, we performed a regional-scale survey of soil fungal community assembly in different land-use types with an increasing gradient of agricultural intensity, i.e., open field cultivation of main crops (CF) or vegetables (VF), and greenhouse cultivation of vegetables (VG). Results showed that greenhouse cultivation decreased the alpha diversity and spatial turnover rate of soil fungal community. The abundant sub-community was more sensitive to land-use conversion than the rare sub-community. Partitioning the Bray-Curtis dissimilarity found that balanced variation in abundance (i.e., the substitution of individuals by the same number of individuals of a different species), rather than abundance gradients (i.e., one assemblage is a subset of another), accounted for the major shift in fungal beta diversity. Moreover, greenhouse cultivation reduced potential inter-species interactions, and the rare sub-community plays an important role in fungal co-occurrence network. Conversions from CF to VF or VG promoted deterministic processes, which was, to a large extent, associated with changes in soil physicochemical properties. However, conversion from VF to VG decreased deterministic processes. Compared with the rare sub-community, the abundant sub-community with wider niche breadths was more influenced by stochastic processes. Changes in the assembly processes induced by land-use conversion differed between abundant and rare sub-communities. Overall, abundant and rare sub-communities exhibited differential responses to land-use conversion and rare taxa might play a crucial role in maintaining the stability of fungal community.