中文摘要：

围栏封育作为简便而有效的草原恢复措施,在我国草原恢复维护中得到广泛应用。但是有关围栏封育措施随着实施年限的增加,会对草原生态系统的结构与功能产生怎样的影响,仍然是需要关注的问题。本研究以内蒙古锡林郭勒盟退化羊草草原为研究对象,通过对围栏封育样地和自由放牧样地连续5年的植被调查资料,对比分析了围栏封育样地和自由放牧样地的植被组成和生产力的动态特征。结果表明,1）围栏封育措施使退化羊草草原的物种多样性和群落均匀度较自由放牧样地略有提高,群落生态优势度略有降低,但差异均未达到显著水平（P〉0.05）。2）围栏封育措施改变了退化草原的优势物种组成。随着封育措施的实施,总体上草原群落优势种为羊草和大针茅,反映出典型草原特征;而自由放牧样地,羊草和大针茅在群落中的地位不恒定。3）围栏封育措施显著提高了群落植被的平均高度、地上生物量和凋落物量。但随着围封时间的延长群落地上生物量逐渐降低,凋落物量增高。4）围栏封育对退化草原结构和功能的恢复存在不同步性。其中群落生物量受围封措施影响最为明显,2年围封已使其达到峰值;其次是群落的优势种,4年围封已使群落优势种恢复成典型草原群落代表种;反映最为缓慢的是群落多样性指标,7年围封措施并没有使群落的多样性指标与自由放牧样地形成显著差异。由此表明,采用围栏封育措施时需充分考虑恢复目的,制定恢复时间,从而提高草原的可持续利用能力,降低恢复成本。

英文摘要：

Enclosure is widely used in steppe restoration as effects on structures and functions of the steppe ecosystem b tion requires further study. The vegetation composition and d a brief and effective treatment in China y the increase in fencing time during this ynamic productivity characteristics were s but the restoratudied 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 c in th litter haracteristics of e freely grazed p fall were initiall The dominant species were L. chinensis and Stipa grandis in the fenced plots, showing the typical steppe while L. chinensis and S. grandis were not always the dominant species lots. 3） The average height of the community vegetation, the aboveground biomass and y 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 sustain ability and reduce the costs of restoring the steppe.