中文摘要：

在宁夏自治区盐池县人工封育区采用样方调查法对不同封育年限封育区植被的群落结构和生物量进行调查分析，并运用丰富度指数（R）、均匀度指数（E）和综合性多样性指数（Y）分析生物多样性变化．结果表明：大部分优势植物种在封育第4、第5年重要值最大，随着封育时间增加，重要值降低；多样性指数变化不明显，表明长期完全封育对于植物物种多样性的恢复效果不显著；封育第3～7年地表出现结皮，有毒植物生物量降低，总的地上生物量也呈降低的趋势，说明长期封育并不能提高草场的生产力．

英文摘要：

Applying quadrat method, the vegetation of Yanchi county of Ningxia Ningxia Hui Autonomous Region was investigated to study the influence of different fencing time on community structure and biomass. The change of biodiversity was analyzed by using richness indexes （R）, evenness indexes （E） and comprehensive diversity indexes （Y）. The results showed that the highest important value of most dominant species occurred on the 4th and 5th year after fencing, then the importance value decreased as the increasing of fencing time. The change of diversity index was not significant, which indicated that long term enclosure has no significant effect on recovery of plant species diversity. Three to seven years after fencing, soil surface crust occurred, the biomass of poisonous plant decreased, the total biomass overground showed the tendency of decrease, which implied that long time of fencing could not increase the production capability of grassland.