中文摘要：

为检验荒漠草原封育恢复的效果,对宁夏盐池围封9年的退化草场进行了植被调查,共记录34个物种,分属于12个科、27个属,其中豆科（9种）、禾本科（7种）、菊科（6种）所含物种数较多。与封育前相比,物种组成基本相同,常见种和建群种发生了明显变化。采用PCA排序和分层聚类将80个样方分为长芒草、白草、赖草3个群系,依据建群种或优势种的生物学特性将其生境划分为旱生生境、中生生境和轻度盐渍化生境。3个群系的演替速率不同,其中长芒草群系演替进入反应阶段,赖草群系的演替等级相对较高。群系间存在激烈的资源竞争关系,风蚀能够促进赖草群系的进一步扩大。建议通过划区轮牧的方式合理调控长芒草群系和赖草群系的放牧时期,以提高草场的放牧利用价值,降低赖草群系的扩张危险。

英文摘要：

In order to examine the restoration effect of exclosure on desert steppe,an investigation was carried out on the plant communities in a degraded grassland after 9-year exclosure in Yanchi County of Ningxia.A total of 34 plant species were recorded,including 12 families and 27 genera.As compared with those before exclosure,the plant species composition after exclosure had less change,but the common species and constructive species changed remarkably.By using PCA ordination and hierarchical clustering methods,the 80 quadrats investigated were grouped into 3 plant formations,i.e.,Stipa bungeana,Pennisetum centrasiaticum,and Leymus secalinus,which were characterized by arid,mesophytic,and light salinization habitats,respectively,according to the biological characteristics of the constructive or dominant species.These three plant formations belonged to different succession stages,with the S.bungeana formation as a reaction stage and the L.secalinus formation as a higher stage.There was a strong competition on resources between these formations,and wind erosion could expand L.secalinus formation.Therefore,the rational regulation of grazing time in S.bungeana formation and L.secalinus formation by rotation grazing could improve the use efficiency of the grassland,and decrease the expansion risk of L.secalinus formation.