围封对退化沙质草地植物群落的影响

对科尔沁沙地围封草地和放牧草地群落的种类组成、结构和多样性等特征进行比较研究。结果表明：（1）围封草地盖度、密度、地上生物量、高度均优于放牧草地（P<0.01）。与放牧相比，围封使植被盖度、密度、高度和地上生物量分别提高了237%、429%、77%和218%，植物群落结构得到明显改善。（2）与放牧草地相比，围封草地物种数增加了69%，多年生草本、灌木类种数和重要值均高于放牧草地。放牧草地的优势植物种依次是大果虫实（Corispermum macrocarpum）、狗尾草（Setaria viridis）、差巴嘎蒿（Artemisia halodendron），重要值占72%；而围封草地优势植物种依次是达乌里胡枝子（Lespedeza davurica）、糙隐子草（Cleistogenes squarrosa）、虎尾草（Chloris virgate）和画眉草（Eragrostis pilosa），重要值占57%，大果虫实、狗尾草和差巴嘎蒿逐渐处于群落的次要地位，取而代之的是与其环境条件相匹配的优质豆科和禾本科植物。围封使物种组成多样化，科属组成复杂化，优势物种发生了变化，群落结构和功能得到改善，沙地植被得以恢复。（3）围封草地的Shannon-Wiener指数、Simpson指数、Margalef指数、均匀度指数均大于放牧草地。围封增加了群落的物种多样性，群落的稳定性得以提高。

Effect of Enclosure on the Structure of Plant Community in Degraded Sandy Grasslands of Eastern Inner Mongolia

This paper examined the effects of enclosure management on the structure of community in degraded sandy grasslands. Several conclusions were drawn from this study. (1)The coverage, density, aboveground biomass and average height of the fencing grassland were all superior to those of the grazing grassland, and there was a significant different(P<0.01). Compared with the grazing grassland, coverage of the fencing grassland increased by 237%, density, height and aboveground biomass respectively increased by 429%, 77% and 218%. The structure of community was significantly improved by enclosure. (2) Compared with the grazing grassland, the species of the fenced grassland increased by 69%. Species and important values of perennial herbs and shrubs in the fencing grassland were higher than the grazing grassland. The dominant species of grazing grassland were Corispermum macrocarpum, Setaria viridis and Artemisia halodendron, the ration of important value accounted for 72%. Lespedeza davurica, Cleistogenes squarrosa, Chloris virgate and Eragrostis pilosa were the dominant species of fencing grassland, their important value accounted for 57%. In the fencing grassland, the largest families were Leguminosa and Gramineae plants, which were adapted to their growing environment. C. macrocarpum, S. viridis and A. halodendron were gradually in a secondary status. By enclosure, Species composition of the community was diversified, the structure and function were improved,and desertification of sandy grasslands was restored. (3) The Shannon-Wiener index, Simpson index, Margalef index and evenness index of the fencing grassland were all larger than those of the grazing grassland. Enclosure increased the species diversity and stability of community.