围封对草地的影响研究进展

Advances in research on the effects of exclosure on grasslands

围封是草地管理的重要手段。围封通过排除家畜的践踏、采食及排便等干扰,从而使其群落向着一定方向演替。由于草地生态系统本身的复杂性和放牧历史、环境因子等的迭加作用导致退化草地群落围封后出现3种可能的演替模式,即单稳态模式、多稳态模式和滞后模式。由于围封后种群的消长、某些种群的消失及新种的进入导致草地在围封后的植物多样性也发生变化。从"中度干扰"理论、对放牧敏感性植物种消失、以及特殊环境因子下群落恢复缓慢等方面总结了草地围封后植物多样性的3种可能变化方向。总结了围封对土壤种子库的影响及其在草地恢复中的作用。阐述了围封对草地土壤理化性质的作用机制。总之,围封对草地的作用具有两面性。对围封作用要有全面的科学认识,把握好围封的时间尺度,以充分发挥其在退化草地恢复中的作用,避免由于利用不当而对草地产生的负面影响。建议加强对已有相关研究成果的总结与分析,对不明确和有争议的课题进一步深入研究,并建立长期的围封研究项目,增加围封研究的站点建设。

Exclosure plays an important role in grassland management. The effects of exclousure on grassland ecosystems were reviewed from the following aspects such as plant community diversity and productivity, seed bank and soil properties. Grassland community would change toward certain direction after exclosure by eliminating trample, feed intake, dejection of domestic animals. Degraded grassland followed three succession patterns after exclosure, that is mono-stale-state model, multi-stable-state model and lag model. The plant diversity of the grassland would be changed after exclosure due to population growth and decline, disappearance of some species and immigrant of new species. Three change trends of the degraded grassland community diversity were identified as the theory of ＂ moderate disturbance＂, elimination of some species and the slow process of community restoration under specific environment. The effects of exclosure on the recovery of degraded grassland by influencing seed bank were reviewed. The effects of exclosure on soil properties were analyzed. In short, exclosure has different influence on grasslands under different situation. Therefore, we should control the exclosure time scale well to exert its positive effects on recovery of degraded grassland and avoid the negative influences on grassland due to the improper utilization of exclosure measure. We suggest that the summarization and analysis for present research results should be enhanced, the more intensive study should be conducted for the disputed issue, the long term exclosure research programs should be maded, and the exclosure research station should be increased.