Intra- and interspecific variation in mycorrhizal associations across a heterogeneous habitat gradient in alpine plant communities

Spatial and temporal variation in mycorrhizal associations may significantly impact plant community dynamics. In this study we evaluated the distribution and abundance of mycorrhizal associations in alpine plant communities to gain a better understanding of the potential effects of microhabitat and host identity on plantfungus mutualisms. We surveyed the abundance of ectomycorrhizae (ECM) associated with Salix sp. and the abundance of arbuscular mycorrhizae (AMF) associated with Taraxacum ceratophorum, T. officinale, Polemonium viscosum, and P. delicatum in plots under willow canopies and in adjacent open meadows. AMF colonization of T. ceratophorum, T. officinale, and P. viscosum was greater in open meadow than in understory habitats. Conversely, ECM abundance was greater in the willow understory than in the surrounding open meadow. AMF abundance in three of the four host species was negatively correlated with ECM abundance in the soil microsite. Taraxacum ceratophorum showed consistently high colonization by AMF regardless of habitat or ECM abundance. Our results suggest that willow-mediated heterogeneity in light and nutrient availability influence the distribution of AMF associations across the willow-meadow ecotone. Furthermore, species-specific plant life history traits related to growth strategies, carbon allocation patterns, and stress tolerance likely affect mycorrhizal dependence and interspecific variation in mycorrhizal associations.