In the forest-tundra ecotone of the North Fennoscandian inland, summer and winter temperatures have increased by two to three centigrades since 1965, which is expected to result in major vegetation changes. To document the expected expansion of woodlands and scrublands and its impact on the arctic vegetation, we repeated a vegetation transect study conducted in 1976 in the Darju, spanning from woodland to a summit, 200 m above the tree line. Contrary to our expectations, tree line movement was not detected, and there was no increase in willows or shrubby mountain birches, either. Nevertheless, the stability of tundra was apparent. Small-sized, poorly competing arctic species had declined, lichen cover had decreased, and vascular plants, especially evergreen ericoid dwarf shrubs, had gained ground. The novel climate seems to favour competitive clonal species and species thriving in closed vegetation, creating a community hostile for seedling establishment, but equally hostile for many arctic species, too. Preventing trees and shrubs from invading the tundra is thus not sufficient for conserving arctic biota in the changing climate. The only dependable cure is to stop the global warming.

Department of Arctic and Marine Biology University of Tromsø The Arctic University of Norway Alta Norway

Department of Botany and Zoology Masaryk University Brno Czech Republic

Department of Ecology and Environmental Science Umeå University Umeå Sweden

Department of Ecology and Genetics University of Oulu Oulu Finland

Department of Physiological Diversity Helmholtz Center for Environmental Research UFZ Leipzig Germany

German Centre for Integrative Biodiversity Research Halle Jena Leipzig Leipzig Germany

Section of Ecology Department of Biology University of Turku Turku Finland

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Plant traits poorly predict winner and loser shrub species in a warming tundra biome