中文摘要：

科尔沁沙地草地退化、沙漠化过程存在着疏林草地、沙质草场、半流动沙地和流动沙地等明显的逆行演替阶段，并且不同的阶段对应着适合本生境的典型群落类型，每一群落优势种的作用明显。草地退化过程中，原生地带性群落及演替早期群落物种丰富、多样性高．结构复杂，随着草地退化、沙漠化过程，群落组成物种数、科属减少．禾本科植物衰退，物种多样性降低，草地群落结构趋于简单、质量下降。在退化的各个阶段，一年生、二年生和旱生植物功能群在各个阶段始终保持着较高的优势地位．对群落生态功能的发挥和维持起着重要作用。草地退化过程中不同群落的组成变化是物种适应性和群落环境变化相互作用的结果．物种、功能群组成的变化，基本反映草地生态系统退化、群落结构简单化和环境基质稳定性减弱等一系列植被与生境系统变化的趋向。

英文摘要：

Grasslands, such as tree-scattered grassland, sandy grassland, semi-shift sand land and shift sand land, were obviously in a series of degradation stages of Horqin sand land. Each stage was dominant of a species. Moreover, role of the dominant species in every community was prominent for its performance of the most functions of the community. In the early stage of grassland degradation, tree-scattered grassland had a high diversity and relatively stabile community structure, and the species richness, diversity, grass and family number were continually decreased with degradation and/or desertification of grassland. The annual and biennial herbs and xerophytes were dominant in every degraded stage of grassland, and played important roles in maintaining stability and ecological function of the community. The changes of species and functional groups that resulted from mutual interaction between species adaptability and environment, in degraded process of grassland, showed a series of trends in vegetation and environment, such as ecosystem degradation, simplification of community structure, decreased stability of environment matrix and so on.