Root colonisation and spore numbers of the arbuscular mycorrhizal fungi in subalpine grasslands vary depending on the host shrub species

Background While woody plants and their relationship with fertile islands (nutrient hot-spots) have been extensively studied, how the fertile-island effect on arbuscular mycorrhizal fungi (AMF) differs among shrub species remains unexplored.Aims We compared AMF communities (root colonisation and spore density) in three shrub species with distinct phylogenetic lineages and architectural traits: Onobrychis cornuta (compact cushion-forming, deciduous), Berberis integerrima (open canopy, deciduous) and Juniperus sabina (procumbent, evergreen).Methods At 13 sites where all three shrub species co-occurred, root segments and soil samples were collected to quantify AMF root colonisation, spore density and relate them to soil variables. For comparison, spore density was also determined in the adjacent herbaceous patches.Results Soil under O. cornuta and J. sabina had the highest spore densities (2019 and 1976 spores 100-g−1 soil, respectively), while herbaceous patches had the lowest (1130 spores100-g−1 soil). O. cornuta roots had the greatest AMF root colonisation (79.5%) and B. integerrima (41.3%) had the least. Correlations between soil parameters and AMF colonisation and spore density differed with shrub species and soil variables.Conclusions Species-specific AMF traits reflect fungal adaptation to microhabitat conditions under shrub canopies. These findings can guide shrub selection for restoring degraded subalpine ecosystems by aligning fungal symbionts with optimal environmental niches.