Seasonal variations of soil fungal diversity and communities in subalpine coniferous and broadleaved forests

Soil fungi have essential roles in ecosystems, but the seasonal dynamics of soil fungal communities in forests remain unclear. To explore the pattern and variation of soil fungal community diversity and structural composition across forest types and seasons, and identify the main contributors to soil fungal communities, we collected soil samples from subalpine coniferous (Picea asperata and Larix gmelinii) and broadleaved plantations (Betula albosinensis and Quercus aquifolioides) in southwest China in different seasons. Soil fungal community structural composition was determined using the Illumina MiSeq sequencing platform. The results showed that soil fungal diversity and richness in broadleaved forests were higher than in conifer forests. From heatmap cluster analysis, distinct differences in fungal community composition among forest types (coniferous and broadleaved forests) and seasons (May and July, September) were observed. Fungal communities were dominated by Basidiomycota and Ascomycota regardless of forest type and season. Helotiales and Atheliales were abundant in coniferous forests, while Agaricales, Russulales and Thelephorales predominated in broadleaved forests. Fungal community diversity and composition were significantly driven by soil pH, moisture, organic carbon, ammonium (NH4+-N), fine root biomass and root tissue density, when controlling for the effects of forest type and season. Thus, forest type and season significantly affected soil fungal community diversity and composition by altering soil properties and root variables.