Abstract:

The southern fringe of Kumtag Desert is a transition zone for vegetation from rangeland desert type in the Gobi in front of eastern Aerjingshan to wind-accumulation desert type. The diversity of plant species in 20 plots in this area was investigated by calculating the indices of species diversity, richness, evenness and dominance from important values. The results indicated that: 1) The distribution of desert plant community differs with various habitats and landforms. Sympegma regelii community is distributed in the Gobi in front of the mountain; Populus euphratica, Tamarix ramosissima, Glycyrrhiza inflata communities are distributed at the alluvial river course or lowland; Haloxylon ammodendron community is distributed in transitional region from Gobi to desert; and Ephedra przewalskii, Calligonum mongolicum and Haloxylon ammodendron communities are distributed on the sandy mountain with low elevation. 2) The structure and composition of desert plant community are simple, and the species diversity is low. Sympegma regelii community, a rangeland desert vegetation, has the highest Shannon-Winner species diversity indices (1.706); the communities of Haloxylon ammodendron and Ephedra przewalskii, which have obvious feature of desert vegetation, are in the middle in species diversity indices (0.875-0.890); the communities of Calligonum mongolicum, Populus euphratica,Tamarix ramosissima and Glycyrrhiza inflata, characterized by desert forest of which saline desert bushes and saline meadows are scattered in the communities, have lowest value of the species diversity indices (0.079-0.495). 3) The structure of desert plant community is dominated by the bush layer. The species diversity indices of bush layer (0.769-1.451) is much higher than that of herb layer (0.193-0.254), and the diversity in herb layer is strongly influenced by bush layer. 4) The species diversity of desert plant communities shows a gradient of change with respect to longitude, latitude and elevation. For example, rangeland plant Sympegma regelii, with a high level of diversity indices (1.706), is in transition to desert plants Haloxylon ammodendronn community (with a low level of diversity indices of 1.379) in a longitude gradient and to saline Tamarix ramosissima community (with a low level of diversity indices of 0.376) in a latitude gradient. Calligonum mongolicum community, with a low level of species diversity (0.819), is in transition to Ephedra przewalskii (with a low level of diversity indices of 0.890) and Haloxylon ammondendron community (with the diversity indices of 0.645) in an elevational gradient. The transition zone of desert plant communities generally has high level of species diversity and relatively low degree of ecological dominance.

Key words: Kumtag desert, Desert plants community, Species diversity