围栏禁牧对内蒙古典型草原群落特征的影响

Effects of Exclosure on Typical Steppe Community Properties in Inner Mongolia

采用样方法对内蒙古典型草原区围封26 a(E26)7、a(E7)2、a(E2)和未围封(G)样地的植物多样性、群落高度、盖度、地上与地下生物量进行实地调查分析,以研究围栏禁牧对草原植物群落特征的影响.结果表明:围封26a样地具有最高的丰富度指数和多样性指数,围封相对于放牧在一定程度上可以维持和保护植物多样性和丰富度.围封7 a样地的多样性指数与未围封样地(G)以及围封2 a样地(E2)无显著差异,说明放牧导致了该区植物多样性的降低,但围封并未显示出使其恢复的趋势;从自由放牧样地到围封样地,退化指示植物糙隐子草(Cleistogenessquarrosa)以及一年生植物猪毛菜(Salsola collina)、刺穗藜(Chenopodium aristatum)等的比重和出现频率呈减少的趋势;围封2 a样地的地上现存量显著低于围封7 a样地,而围封26 a样地相对于围封7 a样地又表现出显著减小的结果.说明围封在一定时期内可显著提高草地生产力,但围封时间过长将不利于其维持较高的生产力.

The effects of exclosure on plant diversity, community height, coverage, above and under ground biomass in Inner Mongolia typical steppe were investigated by quadrat method. The study was conducted in four treatments,viz. ,continuous grazed plot （G） ,2-year old exclosure （E2） ,7-year old exclosure （E7） and 26-year old exclosure （E26） plots. The results showed that E26 had the highest richness index and diversity index in the four plots;while E7 had not present increase in diversity index compared with E2 and G （P 〉0.05）. Exclosure might maintain or conserve,rather than increase,plant diversity in contrast to grazing. The indicator plant of degradation such as Cleistogenes squarrosa and annual plants such as Salsola colliha, Chenopodium aristatum from free grazing plot to exclosure plots showed decrease trend in relative weight and emergence frequency. The above ground biomass of E2 was significantly lower than that of E7; yet E26 had no increase tendency compared with E7. In conclusion, exclosure could significantly improve the grassland productivity in certain period,while there would be no help for grassland productivity if the exclosure lasts too long.