Abstract: This study was taken the semi-arid grassland ecosystem in the farming-pastoral ecotone of Jinbei as the research object. In 2016,four grazing intensity treatments were set up,including no grazing,mild grazing,moderate grazing and heavy grazing. In order to determine the optimal grazing intensity,the influences of sheep on the diversity and productivity of grassland plant community under short-term grazing intensities were studied. The results showed that with the increase of grazing intensity,the abundance of plant communities showed a trend of increasing first and then decreasing,while the height and coverage decreased gradually with the increase of grazing intensity;Species diversity was the highest in moderate grazing and the lowest in heavy grazing. The aboveground biomass of plants changed in a parabolic form with the increase of grazing intensity and was the highest in moderate grazing,with 757.04 g·m^-2 and 398.37 g·m^-2,respectively. The underground biomass of plants decreased gradually with the increase of grazing intensity;Soil bulk density of grassland increased with the increase of grazing intensity. The plant community abundance,species diversity and aboveground biomass of moderate grazing were the highest under short-term grazing,the plant community height,coverage and underground biomass of light grazing were the highest,and the plant community diversity and productivity of heavy grazing were lower. Therefore,moderate grazing was conducive to maintaining the stability of grassland plant community.

Key words: Grazing intensity, Plant community, Species diversity, Productivity, Semi-arid grassland

摘要： 本文以晋北农牧交错带半干旱草地生态系统为研究对象，于2016年设置不放牧、轻度、中度和重度放牧4个不同放牧强度试验，研究短期放牧强度下羊对草地植物群落多样性与生产力的影响，以确定最佳放牧强度。研究结果表明，植物群落多度随放牧强度增加呈先升后降趋势，高度与盖度则随放牧强度的增加逐渐降低；物种多样性在中度放牧最高，重度放牧时最低；植物地上生物量随放牧强度增加呈抛物线形式变化，中度放牧时最高，分别为757.04 g·m^-2和398.37 g·m^-2，植物地下生物量随放牧强度增加逐渐降低；草地土壤容重随放牧强度的增加逐渐增大。短期放牧下中度放牧的植物群落多度、物种多样性与地上生物量最高，轻度放牧植物群落高度、盖度和地下生物量最高，重度放牧的物种多样性与生产力较低，因此适度放牧有利于保持草地植物群落稳定。

关键词: 放牧强度, 植物群落, 物种多样性, 生产力, 半干旱草地