Figures for Gemal <i>et al.</i> (2024)

Figures for the journal article by Gemal et al. (2024), "Reindeer grazing and soil wetness interact to drive tundra plant community structure in northern Sweden".AbstractQuestions: The relative importance of abiotic versus biotic factors on structuring plant communities is debated, especially in the Arctic tundra where the harsh environment is limiting together with effects of grazing by reindeer. To understand the relative and interactive effect of abiotic(bottom-up) and biotic (top-down) factors on vegetation in the Swedish mountain tundra we ask: how do bottom-up factors and their interaction affect reindeer grazing activity and vegetation composition?Location: Summer pastures of Gran reindeer herding district, in Vindelfjällen mountain tundra (northern Sweden).Methods: We surveyed the composition of vascular plants, bryophytes and lichens across 34 sites (17 north-facing, 17 south-facing) along a grazing duration gradient based on data collected fromaccelerometers collared on reindeer. Data on the bottom-up factors slope, soil wetness, soil depth, primary productivity and the top-down factor grazing duration were extracted for each of our sampled plots (n = 102). The relative and interactive effect of all factors on vegetation composition and species richness was analysed using generalized linear models.Results: Reindeer grazed for a longer time in drier than wetter sites, indicating an important interaction between grazing and soil wetness. Bottom-up factors prevailed as the dominant driver of local vegetation patterns, while grazing duration had weak effects on the vegetation. Wetter sites with longer grazing duration exhibited an increase in graminoid species, while drier sites with shorter grazing duration had more shrub and lichen species.Conclusions: This study shows that soil wetness has a strong effect in structuring tundra plant communities, but also highly influences reindeer grazing intensity. Based on these results, we stress the importance to further investigate the interaction between grazing and soil wetness in order to foresee changes in the tundra vegetation; especially as plant communities might change under altered grazing regimes and future hydrological conditions as an effect of predicted climate change.