The Fungal Functional Guilds at the Early-Stage Restoration of Subalpine Forest Soils Disrupted by Highway Construction in Southwest China

Soil fungi often operate through diverse functional guilds, and play critical roles in driving soil nutrient cycling, organic matter decomposition and the health of above-ground vegetation. However, fungal functional guilds at the early-stage restoration of disrupted subalpine forest soils remain elusive. In the present study, we collected 36 soil samples along an altitudinal gradient (2900 m a.s.l., 3102 m a.s.l., and 3194 m a.s.l.) from cut slopes (CS) (from Wenma highway) and natural soils (NS) at the Miyaluo of Lixian County, Southwest China. By applying nuclear ribosomal internal transcribed spacer (ITS) sequencing, this study revealed the ecological characteristics of fungal functional guild in the early-stage restoration of cut slope soils. The results showed that the predicted prevalence of ectomycorrhizal fungi decreased, while plant pathogens and arbuscular mycorrhizal fungi increased in CS. In the high-altitude regions (3102 m a.s.l. and 3194 m a.s.l.), the differences in communities between natural and cut slope soils were more pronounced for total soil fungi, soil saprotroph, litter saprotroph, arbuscular mycorrhizal fungi and ectomycorrhizal fungi, in contrast to the low altitude communities (2900 m a.s.l.). An opposite pattern was evident for plant pathogens. Variations in the differences of both soil properties (mainly soil pH) and community assembling processes (e.g., heterogeneous selection, dispersal limitation and drift) between natural and cut slope soils across the altitudinal gradient likely shaped the shifting patterns of community difference. This study provides valuable insights for devising restoration approaches for cut slopes in subalpine forest ecosystems, emphasizing the importance of taking soil fungal functional guilds into account in evaluating the restoration of cut slopes, and underscoring the necessity for increased attention to the restoration of soil fungi in cut slopes at the high-altitude ecosystems.