异质生境对荒漠草原植物群落组成和种群生态位的影响

为揭示荒漠草原不同植物种群生态位特征以及对有限资源的利用状况，以围栏内外不同土壤类型下植物群落为研究对象，运用经典生态位理论，探讨其群落组成和种群生态位特征。结果表明：在调查样方中共记录到15科36属42种植物，以豆科、禾本科、菊科和藜科的草本植物为主。风沙土生境中的植被生物量和密度最高，一年生植物生态位宽度值往往较高，以猪毛蒿的重要值最大。灰钙土生境中植被盖度较高，多年生植物生态位宽度值相对较高，以牛枝子和针茅的重要值最大。放牧会减少多年生草本的种类和数量，而一年生草本有所增加，对半灌木数量则影响不大。在不同生境下猪毛蒿生态位宽度和总宽度值均居首，是该区域主要优势种和典型的泛化种。在放牧和短期围栏内猪毛蒿与其他物种的生态位重叠指数均较高，但在长期围封样地中，特别是灰钙土生境下，重叠指数比重有所降低。基岩风化沉积土中物种间的重叠程度最大，而风沙土中则最小。猪毛蒿分布在生态位重叠指数DCA排序图的中心，说明其在群落中占有重要地位，对有限资源的竞争能力和对环境的适应能力较强。综上，生境的异质性是导致群落组成及生态位不同的关键因子，因此在荒漠草原进行植被恢复建设和保护措施时，应考虑不同土壤类型条件下各物种生态适应性，避免生态位功能冲突。

Effects of heterogeneous habitats on community composition and niche characteristics of different plant populations in the desert steppe of China

We selected plant communities in different soil types in enclosures and grazing lands on the desert steppe of China to explore community composition, niche characteristics of populations, utilization of limited resources, and mechanisms of inter-specific competition and co-existence, employing classical niche theory. A total of 42 species, belonging to 36 genera and 15 families, were recorded in 90 quadrats, and Leguminosae, Gramineae, Compositae, and Chenopodiaceae were the dominant families. The biomass and density of vegetation in aeolian sandy soil habitats were the highest, the niche breadth of annual plants was frequently higher, and the importance value of Artemisia scoparia was the largest. The vegetation coverage and the niche breadth of perennial plants was relatively higher than those of the annual plants, and the importance values of Lespedeza potaninii and Stipa capillata in sierozem soil habitats were the maximum. Grazing decreased the number of species and the density of perennial herbs, while annual herbs increased in number of species and density, and there was no significant effect on the density of semi-shrubs. As the dominant species in this area, A. scoparia had the highest niche breadth and total niche breadth in different habitats. The niche overlap index of A. scoparia and other species was higher in the grazing and short-term enclosure habitats, while the proportion of niche overlap index decreased in long-term enclosures, especially in sierozem soil habitats. The degree of niche overlap index among species in the weathering bedrock habitats was the largest, while it was the smallest in the aeolian sandy soil habitats. A. scoparia was mostly distributed in the center of the DCA ordination map, indicating that it played an important role in the community, had a strong competitiveness for limited resources, and showed good adaptability to the environment. The heterogeneity of habitats was the key factor leading to the difference in community composition and niche characteristics. Therefore, the ecological adaptability of species in different soil types should be considered in vegetation restoration and protection measures in the desert steppe to avoid niche function conflict.