Environmental perturbation, grazing pressure and soil wetness jointly drive mountain tundra toward divergent alternative states

1. Plant communities are structured by complex interactions between multiple factors, which veil our understanding of the effects of environmental changes on communities and ecosystems. Besides the relative role of biotic and abiotic factors as community-structuring processes, addressing how they jointly affect the ecological resilience and resistance of plant communities is crucial to understand better the long-term response of communities facing global changes. 2. Here, we used the results from a long-term (23 years) perturbation experiment set up in Fennoscandian mountain tundra to test these mechanisms. The experiment consisted of a transplantation of twenty blocks of Vaccinium myrtillus heath vegetation including upper soil layer from a lower elevation tundra heath habitat to a snowbed habitat 150 m higher in elevation where V. myrtillus lies at its upper limit. In the snowbed with contrasting levels of soil wetness, half of the transplanted blocks were protected from mammalian her...