季节性围封对内蒙古典型草原植被恢复的影响

Influence of Seasonal Exclosure on Vegetation Restoration in Typical Steppe,Inner Mongolia

针对退化草地恢复与合理利用问题,选取生长季围封调制干草、其他时间轻度放牧利用的草地为研究对象,同时选取自由放牧草地为对照,开展季节性围封对典型草原植被恢复影响的研究。结果表明:重度退化草地采用生长季围封措施后植被恢复演替,草地生产力、盖度、密度和地下生物量显著增加(P<0.05),围封13年达最大,之后降低。围封后各物种的优势地位发生较大改变,经20年围封,草地由星毛委陵菜(Potentilla acaulis)+冷蒿(Artemisia frigida)+糙隐子草(Cleistogenes squarrosa)演替为羊草(Leymus chinensis)+克氏针茅(Stipa krylov-ii)+冷蒿+糙隐子草。就围封后物种多样性的变化来看,经7年围封,物种的丰富度、多样性、均匀度和生态优势度指数显著增加(P<0.05)。但由于各物种的竞争能力不同,经10～13年围封,群落成为具有单优或寡优势种的群落,物种丰富度、均匀度和多样性指数降低,生态优势度指数急剧增加。之后,随着围封年限继续延长至20年,群落逐步趋于稳定,形成多优或优势不明显的群落,群落的丰富度、均匀度及多样性指数增加,生态优势度指数降低。综上所述,生长季围封调制干草、其他时间轻度放牧利用的管理方式可保证退化草地在一定程度上得到恢复,综合考虑草地产草量、群落结构及物种多样性,认为13年是较适宜的围封年限,但围封后的适宜利用问题(如适宜的割草制度)有待进一步研究。

In order to discuss the restoration and reasonable utilization of degradation typical steppe,natural grasslands fenced in growing season for hay production then lightly grazed for the rest of the year were selected as research objects.Continuously grazed grasslands were selected as control.Vegetation restoration was investigated after seasonal exclosure.Results showed as follows： the biomass,coverage and density of vegetation in degraded typical steppe increased significantly after seasonal exclosure（P0.05）,and reached the highest values after 13 years exclosure then decreased due to hay production developed continuously for many years.Dominant species changed significantly after seasonal exclosure.The community structure was changed from Potentilla acaulis＋Artemisia frigida＋Cleistogenes squarrosa to Leymus chinensis＋Stipa krylovii＋Artemisia frigida＋Cleistogenes squarrosa after 20 years exclosure.The species richness,evenness,diversity and dominance increased significantly after 7 years exclosure.But the community was mainly dominated by signal or minority species and the species richness,evenness and diversity decreased then the dominance increased remarkably after 10 to 13 years exclosure.Then the community stabilized gradually,the species richness,evenness and diversity increased and the dominance decreased with the exclosure period prolonged to 20 years.In conclusion,seasonal exclosure was a feasible management method in Chinese pastoral areas.Comprehensive analysis of community structure,yield and species diversity indicated that 13 years exclosure is a reasonable exclosure period.And some problems such as reasonable mowing systems needed further study.