The balance of canopy and soil effects determines intraspecific differences in foundation species’ effects on associated plants

1. The impact of plant-plant interactions on species diversity patterns has been broadly addressed in stressful environments, such as alpine ecosystems, where foundation species promote species richness by creating habitat for other species. However, foundation species with contrasting phenotypes might modify the microhabitat differently, which would alter the subordinate community composition, and coincide with distinct feedback effects of those subordinate species on the foundation species. However, the precise interaction mechanisms that facilitate species are not fully understood, especially the relative contribution of above- and below-ground compartments of foundation species to subordinate species and the potential feedbacks they receive.
2. We explored whether two contrasted canopy phenotypes (tight and loose) of the shrub Cytisus galianoi differed in their effects on the microhabitat and on subordinate plant community composition in a dry subalpine system. We also experimental...