Abstract
The Siberian mammoth steppe ecosystem changed dramatically with the disappearance of large grazers in the Holocene. The concept of Pleistocene rewilding is based on the idea that large herbivore grazing significantly alters plant communities and can be employed to recreate lost ecosystems. On the other hand, modern rangeland ecology emphasizes the often overriding importance of harsh climates. We visited two rewilding projects and three rangeland regions, sampling a total of 210 vegetation relevés in steppe and surrounding vegetation (grasslands, shrublands and forests) along an extensive climatic gradient across Yakutia, Russia. We analyzed species composition, plant traits, diversity indices and vegetation productivity, using partial canonical correspondence and redundancy analysis. Macroclimate was most important for vegetation composition, and microclimate for the occurrence of extrazonal steppes. Macroclimate and soil conditions mainly determined productivity of vegetation. Bison grazing was responsible for small-scale changes in vegetation through trampling, wallowing and debarking, thus creating more open and disturbed plant communities, soil compaction and xerophytization. However, the magnitude of effects depended on density and type of grazers as well as on interactions with climate and site conditions. Effects of bison grazing were strongest in the continental climate of Central Yakutia, and steppes were generally less affected than meadows. We conclude that contemporary grazing overall has rather limited effects on vegetation in northeastern Siberia. Current rewilding practices are still far from recreating a mammoth steppe, although large herbivores like bison can create more open and drier vegetation and increase nutrient availability in particular in the more continental Central Yakutian Plain.
Highlights
The Siberian mammoth steppe ecosystem changed dramatically with the disappearance of large grazers in the Holocene
Zimov et al.[5,13,14,15] have developed a herbivore-vegetation-model (“Ecosystem hypothesis”), claiming that a cold steppe, which once existed under dry-cold Pleistocene glacial s tages[16,17,18], would still be the natural vegetation of NE-Siberia today
According to pollen and macrofossil analysis, the Pleistocene mammoth steppe was characterized by typical steppe and tundra p lants[18,20]
Summary
The Siberian mammoth steppe ecosystem changed dramatically with the disappearance of large grazers in the Holocene. The concept of Pleistocene rewilding is based on the idea that large herbivore grazing significantly alters plant communities and can be employed to recreate lost ecosystems. Current rewilding practices are still far from recreating a mammoth steppe, large herbivores like bison can create more open and drier vegetation and increase nutrient availability in particular in the more continental Central Yakutian Plain. There is evidence that large herbivores have shaped vegetation structure, ecosystem processes, landscape heterogeneity and even entire biomes in their time[8,9,10]. During Pleistocene cold stages, the non-glaciated northern latitudes were characterized by extensive herbdominated grassland vegetation that supported a wide array of large herbivores in a now-extinct cold steppe biome—the mammoth s teppe[17,19] (see Appendix S1: Table S1_1 for details). Productivity of vegetation should have been relatively high compared to current conditions to support high densities of large h erbivores[10,19,30], and soils should have been more fertile[19] than today in the arctic, where nutrient deficiency is often the limiting factor[31]
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