干旱区生态环境知识资源中心

This paper presents the first detailed description of plant communities in the south-eastern Gobi Altay, covering the terrain of the Gobi Gurvan Sayhan National Park and adjacent areas. Phytosociological classification of 549 releves yielded 4 community groups with 39 communities. The distribution of communities is largely controlled by water availability, which is generally higher in the mountains. The upper slopes are covered by scrub with Juniperus sabina and by various types of mountain steppes with Stipa krylovii, while S. gobica desert-steppes dominate the upper piedmont areas. With decreasing humidity, Stipa glareosa-Allium polyrrhizum desert steppes occur and merge with semi-desertic, very open dwarf-shrublands towards the inter-montane basins and salt pans. Anabasis brevifolia, Salsola passerina, Zygophyllum xanthoxylon, and Haloxylon ammodendron are the most characteristic woody constituents of these semi-deserts. Extra-zonal vegetation types of minor spatial extent concentrate in water-surplus habitats in both extremes of the humidity range: Betula microphylla forests, Helictotrichon schelliani meadow steppes, and Kobresia myosuroides mats are restricted to the moistest slopes in the mountains; they contrast with Nitraria scrub, takyr communities, salt meadows, and Phragmites reeds in saline habitats of the inter-montane basins. The steppes have been grazed by both, wild and domestic herbivores for millennia, so all occurring plant species are well adapted to the grazing pressure. No regional grazing indicators could be identified, and grazing appears to be sustainable on the current level. However, rare occurrences of trees (Populus laurifolia gallery forest in the mountains, Populus diversifolia woodlands, and Ulmus pumila stands in the piedmont zones) indicate a certain potential for tree growth at favourable sites in the study area. Further studies