中文摘要：

在甘肃环县典型草原6年的轮牧试验表明：不同践踏强度下各样地0～20 cm层地下生物量占0～30 cm层的90%以上,随着放牧践踏强度的增加,0～10 cm土层中的根量先增长后降低,其中以中度践踏（80次羊践踏/m^2·期）最高,约为对照（0次羊践踏/m^2·期）和轻度践踏（40次羊践踏/m^2·期）的1.7倍,10～20 cm土层以轻度践踏（40次羊践踏/m^2·期）最高,20～30 cm土层地下生物量与践踏强度相关不显著,相关系数仅为0.12;以地下生物量最大化为准则,对0～10 cm、10～20 cm土层地下生物量与践踏强度的回归模型进行解析和寻优分析,确定出环县典型草原适宜的放牧强度是3.5～5羊单位/hm^2。

英文摘要：

Tan-sheep rotational grazing trails were conducted for six years in steppe grassland of Huanxian County, Gansu Province. The results indicate： the underground biomass tended to gather in surface layer of soil with the underground biomass in depth 0～20 cm accounted for more than 90% for the entire 0～30 cm depth in all sampled sites. Along with the increase of trampling intensity, the underground biomass of 0～10cm soil layer increased at first and then dropped rapidly; the highest underground biomass of 0～10 cm layer was detected under moderate trampling intensity and approximately 1.7 times of the control and light trampling intensity. For underground biomass of 10～20 cm soil layer, the highest underground biomass was achieved under light trampling intensity. No significant relationship was detected between the underground biomass in depth 20～30 cm and trampling intensities and the correlation coefficient was 0.12 only. Taking the rule of highest underground biomass, the most suitable grazing intensity for the steppe grassland of Huanxian County was found to be 3.5～5 sheep unit/hm^2 based upon the analysis and optimization of the regression model for underground biomass of 0～10cm and 10～20 soil layers with trampling intensity as the independent variable.