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.