Abstract:

Enclosure is widely used in steppe restoration as a brief and effective treatment in China but the effects on structures and functions of the steppe ecosystem by the increase in fencing time during this restoration requires further study. The vegetation composition and dynamic productivity characteristics were studied in both fenced and freely grazed plots during a five-year vegetation investigation on degraded Leymus chinensis steppe in Inner Mongolia. 1) The species diversity and community evenness were improved in the enclosure treatment compared with the freely grazed treatment, but the ecological dominance if the community decreased although the differences were not statistically significant (P＞0.05). 2) Dominant species were changed by the enclosure treatment. The dominant species were L. chinensis and Stipa grandis in the fenced plots, showing the characteristics of the typical steppe while L. chinensis and S. grandis were not always the dominant species in the freely grazed plots. 3) The average height of the community vegetation, the aboveground biomass and litter fall were initially increased under the enclosure treatment, but with time, the aboveground biomass gradually decreased and the litter fall increased. 4) The restoration of the structures and functions in the steppe was not isochronous in the enclosure treatment: Community biomass reached a peak only after two years but by four years the dominant species were restored to the typical steppe level. Community diversity was not improved even after a seven-year enclosure compared to the freely grazed treatment. In conclusion, the restoration purpose should be considered when planning enclosure treatment and a timetable established in order to improve sustainability and reduce the costs of restoring the steppe.