围封年限对沙化草地群落结构及物种多样性的影响

目的]了解围封年限对宁夏回族自治区盐池县沙化草地群落结构及物种多样性的影响,揭示围封沙化草地植被变化规律。方法]在半干旱区运用空间代替时间法选取不同围封年限区(5,10,20a)和未封育区(对照)的沙化草地为研究对象,进行群落结构及物种多样性的对比研究。结果]1年和2年生草本是未封育区的优势种。灌木是封育5a区的优势种,而封育10a区的优势种是灌木和多年生草本,在封育20a区,优势种是多年生草本。与未封育区相比,围封5a,10a区植被数量特征值均有显著提高,而围封20a区特征值稍高,但相差不大。结论]并不是围封时间越长,植被生长状况就越好。小于5a的封育年限可以提高群落的物种多样性,封育年限大于10a,反而使物种多样性下降。围封措施对植被恢复起到了先促进后抑制的作用。

Influence of Enclosure Ages on Community Structure and Species Diversity of Sandy Grassland

Objective] To investigate the influence of enclosure ages on community structure and species diversity of sandy grassland in Yanchi County of Ningxia Hui Autonomous Region, for revealing the change rule of vegetation restoration in the enclosed sandy grassland. Methods] Taking the non-enclosure and enclosed sandy grasslands in 5, 10, 20 years as research objects, the influence of different enclosure ages on the community structure and species diversity in semi-arid region was carried out by using the method ofspace-for-time subotitution. Results] The dominant species in not enclosed areas were annual and biennial herbs. In enclosed areas, they were shrubs enclosed for 5 years, perennial herbs and shrubs for 10 years, perennial herbs for 20 years, respectively. Comparied with not enclosed area, the index values of vegetation cover, community density and biomass were increased obviously in 5 and 10 year enclosed areas, while decreased a little in 20 year enclosed area. Conclusion] The long-term enclosure could not improve the productivity of sandy grassland vegetation. The enclosure ages less than 5 years can promote vegetation restoration, but it plays an inhibitory role when the enclosure ages was more than 10 years. In the short term, enclosing measures promote vegetation restoration, but for long term, enclosure plays an inhibitory role.