Changes of community composition and plant diversity of enclosing grassland in Yili Valley

The grassland vegetation characteristics and plant diversity were analyzed to study the effect of enclosure on degraded grassland natural recovery in Yili Valley. The results showed that the dominant species transferred from Thymus asiaticus + Carex liparocarpos to Stipa capillata + Carex liparocarpos with enclosing. The aboveground yields and community height increased highest in the 5th enclosure year and then decreased, however, the community coverage and the fine forage ratio continued increased and reached highest in the 6th enclosure year. The richness index reached climate in the 6th enclosure years, and it was significantly different with other sample areas. The diversity index and evenness index reached climate in the first enclosure year, and the dominance index reached climate in the 6th enclosure year. The similar index was over 0.65 is different enclosure times. The similar index reached highest between enclosure 6 years and 5 years, which demonstrated the grassland community tended to stable after the grassland recovery, and the nonenclosure grassland was easy to disturbance which had lower similar index.