Pernille Bronken Eidesen

1 Introduction Arctic tundra vegetation covers over 7 million km2 of the Earth's surface (Raynolds et al. 2019). Climate warming is contributing to notable changes in the composition of Arctic tundra vegetation, particularly shrub expansion (‘shrubification’) (Myers-Smith et al. 2011). Shrub expansion has and will have Arctic-wide impacts on vegetation communities, tundra ecosystems, Arctic surface energy and carbon balance, and potentially global climate feedbacks (Mekonnen et al. 2021).