Vertical fungal community distribution patterns along a stratified soil profile in subalpine Larix principis-rupprechtii plantations on China's Luya mountain

Soil microorganisms play important roles in the biogeochemical cycling of terrestrial ecosystems. Recent studies found that soil fungal composition and diversity varied significantly with soil depth. However, little is known about the vertical distribution patterns of soil fungal communities and their associated drivers. For this study, we collected soil samples from six soil layers (i.e., litter layer (P), humus layer (P0), 0-10 cm layer (P1), 10-20 cm layer (P2), 20-40 cm layer (P3), and 40-80 cm layer (P4)) within Larix principis-rupprechtii plantations to investigate fungal community composition, diversity, and associated drivers using Illumina MiSeq high-throughput sequencing. Results showed that the top 10 dominant genera with the highest relative abundance belonged to Ascomycota, Basidiomycota, and Mortierellomycota. A decreasing α-diversity trend was observed along with soil depth. Moreover, correlation analysis showed that ammonia nitrogen (NH₄⁺-N), pH, total carbon (TC), and total nitrogen (TN) content markedly correlated with fungal α-diversity. Significant β-diversity differences were found in soil fungal communities. Additionally, TN and total phosphorus (TP) content were the main environmental drivers that influenced the spatial distribution pattern of fungal communities. The βNTI showed a gradual increase with soil depth. In the surface layers of soil, the dominant factor of fungal community assembly was homogeneous selection, while in the deep layers of soil, it was variable selection. Co-occurrence network analysis showed that fungal community interactions in the deepest soil layer (40-80 cm) were more complex and were more positive. Results from this study provide a theoretical basis and data support to understand the mechanisms of soil fungal community assembly processes more deeply in L. principis-rupprechtii plantations.