根据20个样地的调查资料,应用重要值计算多样性指数、均匀度指数、丰富度指数、优势度指数,对库姆塔格沙漠南缘荒漠植物群落物种多样性进行分析。结果表明: 1)荒漠植物群落分布随其生境地貌不同而不同,山前戈壁上分布有合头草(Sympegma regelii)群落,冲积河道低地分布有荒漠林胡杨(Populus euphratica)、多枝柽柳(Tamarix ramosissima)、胀果甘草(Glycyrrhiza inflata)群落,戈壁沙漠过渡带为梭梭(Haloxylon ammodendron)群落,低海拔的沙山上分布有沙拐枣(Calligonum mongolicum)群落、膜果麻黄(Ephedra przewalskii)群落和梭梭群落。2)荒漠植物群落物种多样性水平较低,群落结构简单,物种组成单一。群落Shannon-Wiener物种多样性水平表现为合头草群落最高(1.706),具有草原化荒漠植被类型的成分;梭梭群落、膜果麻黄群落居中(0.875~0.890),荒漠植被类型特征明显;沙拐枣群落、胡杨群落、多枝柽柳群落、胀果甘草群落较低(0.079~0.495),荒漠林、盐地沙生灌丛及盐化草甸植被均有零星分布。3)荒漠植物群落结构层次中,灌木层占居主导地位,群落灌木层物种多样性水平(0.769~1.451)远远大于草本层(0.193~0.254),且草本层物种多样性受灌木层影响较大。4)荒漠植物群落物种多样性分布格局表现为经向、纬向和海拔梯度的变化,经向、纬向变化为物种多样性水平较高的草原化植物合头草群落(1.706)向物种多样性水平较低的荒漠植物梭梭群落(1.379)和盐化植物多枝柽柳群落(0.376)的过渡,海拔梯度则呈现低水平的沙拐枣群落(0.819)到高水平的膜果麻黄群落(0.890)向低水平的梭梭群落(0.645)变化。荒漠植物群落过渡地带一般具有较高的物种多样性和较低的生态优势度。

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.