Temporal and spatial succession and dynamics of soil fungal communities in restored grassland on the Loess Plateau in China

Natural secondary succession of degraded soil has improved the ecological environment of the Loess Plateau, profoundly influencing the succession and dynamics of soil fungal communities restored grasslands in particular. This chronosequence and the varied topography of the Loess Plateau thus provide a unique opportunity to synchronously investigate the variation of soil quality and fungal communities as they develop over time and space. Here, we used high-throughput sequencing of the ITS rRNA gene region to analyze the fungal community at a local scale. Edaphic variables and fungal community characteristics were compared among three restoration durations (5, 20, and 30 years), two soil layers (topsoil and subsoil), and different topographic factors (slope positions and aspects). Edaphic variables displayed varying patterns with significant differences among restoration durations and soil layers, but no such topographic patterns were found. As succession proceeded, alpha and beta diversities of fungal communities changed as space changed; whereas, over time, the discrepancy in community composition between the two soil layers declined. Constructed co-occurrence networks of edaphic variables combined with fungal community composition and distribution patterns based on indicator and keystone species also varied among three durations. Fungal trophic guilds showed a contrasting distribution between the two soil layers, but they closely followed the soil nutrient conditions and metabolic characteristics of keystone species. Our results demonstrated that predictable spatial variation occurs in soil fungal communities in tandem with temporal succession and dynamics of indicator and keystone species in restored grassland on the Loess Plateau.