Decades of Change in Vascular Plant Composition in High-Latitude Ecosystems: Shifting Prevalence of Pollination Strategies.

The composition of high-latitude plant communities has changed over the past decades in response to several global change drivers. However, less is known about how these compositional long-term changes are reflected in the total cover of plant species that do or do not interact with pollinators. Using species-specific indicator values for pollinator dependence and nectar production, we provide empirical evidence on how compositional changes in vascular plant communities over the past 50 years are reflected in the cover of pollinator-dependent and pollinator-independent plants, as well as the cover of pollen- and nectar-rewarding and non-nectar plants, in two ecosystems in northern Fennoscandia. We show that the average cover of pollinator-independent plants greatly increased in both tundra and herb-rich forest communities over time. Average cover of pollinator-dependent plants slightly increased in tundra but decreased in herb-rich forests. The average cover of pollen-nectar plants increased in the tundra but decreased in herb-rich forests over time. At the same time, the cover of non-nectar plants increased in both ecosystems. The observed changes were strongly driven by the increased cover of evergreen dwarf shrubs in the tundra and the decline of forb cover in herb-rich forests. The observed changes were comparable between sites that had been disturbed by human land use and sites that remained in a natural or semi-natural state. Our results suggest that, in terms of average plant coverage, high-latitude plant communities have broadly become less dependent on insect pollination over the past 50 years. By documenting long-term changes in the pollination strategies of high-latitude plant communities, our study underscores the need to explore how shifts in plant community composition are linked to pollination processes and broader plant-pollinator dynamics. We highlight patterns that warrant further investigation and offer perspectives for future research on plant-pollinator interactions in northern ecosystems under global change.