Extrazonal steppes and other temperate grasslands of northern Siberia-Phytosociological classification and ecological characterization

作者：Reinecke Jennifer^*; Troeva Elena; Wesche Karsten

来源：Phytocoenologia, 2017, 47(2): 167-196.

DOI：10.1127/phyto/2017/0175

• Carici rupestris-Kobresietea bellardii
• Cleistogenetea squarrosae
• cryophytic steppe
• extrazonal steppe
• Festucetalia lenensis
• Stipa krylovii
• Stipetalia krylovii
• Mammoth steppe
• Molinio-Arrhenatheretea
• northern Siberia
• phytosociological classification
• tundra steppe

Aims: Isolated outposts of eastern steppe vegetation (Cleistogenetea squarrosae and physiognomically related syntaxa) can be found on south-exposed slopes in the tundra and taiga zone of northern Siberia. They are considered relics of the Pleistocene cold steppe, but a number of Russian geobotanical studies reveal how these steppes differ among each other in floristic composition and environmental conditions. We aim at providing an overview of current phytosociology of northern Siberian steppes and co-occurring temperate grasslands through literature review and classification of our own data. Study area: Central and northeastern Yakutia, Russia. Methods: Phytosociological classification of 210 releves of meadow, steppe and tundra steppe vegetation using the Braun-Blanquet approach; samples were further characterized using macro-and microclimatic variables. Results: We found true steppes of the Stipetalia krylovii up to Central Yakutia and meadow steppes of the Festucetalia lenensis as far as northeastern Yakutia. Both are restricted to south-exposed slopes, with slope steepness increasing towards the north, compensating for a colder and wetter macroclimate. Both orders include typical (Stipetum krylovii, Pulsatillietum flavescentis) and petrophytic (Elymus reflexiaristatus community, Carici duriusculae-Festucetum lenensis) associations or communities, with meadow steppes additionally containing a unique cryophytic association (Astragalo pseudoadsurgenti-Calamagrostietum purpurascentis). So called tundra steppes occur north of the tree line. They belong to the class Carici rupestris-Kobresietea bellardii, and their occurrence is more related to disturbance than to slope exposure or inclination. Conclusions: Steppe vegetation of the Cleistogenetea squarrosae occurs as far north as the taiga zone of northeastern Yakutia, but tundra steppes are not steppes in the true sense, despite similar physiognomy and the contribution of xerophytes. This distinction is important when trying to find modern analogues of Pleistocene cold steppes.

• 出版日期2017