高寒小嵩草草甸牦牛优化放牧强度的研究

高寒小嵩草草甸牦牛放牧强度试验表明:(1)不同放牧强度下各植物类群的地上生物量和总的地上生物量之间差异极显著,莎草科植物地上生物量的百分比组成之间差异极显著,禾本科和杂类草地上生物量的百分比组成之间差异显著,而且禾本科和莎草科(除对照外)植物的地上生物量及其百分比组成随放牧强度的增加而减小,杂类草的变化与之相反;(2)优良牧草比例和草地质量指数与放牧强度之间均呈负相关,而优良牧草比例的年度变化和牦牛个体增重的年度变化之间呈正相关;(3)群落的相似性系数随放牧强度的增加而减小.通过建立植被变化度量指标,认为优良牧草比例的年度变化是评价高寒小嵩草草甸放牧价值的直接度量指标,而相似性系数的变化和草地质量指数的变化与牦牛生产力没有明显的联系,不能反映草场植被放牧价值的变化,只能指示植物群落整体的相对变化程度;牦牛的放牧强度约为1.86头/hm2是小嵩草高寒草甸暖季草场可持续生产而不退化的最大放牧强度.

Optimized Grazing Intensity of Yak in Alpine Kobresia parva Meadow

The experiment about the grazing intensities of yak in alpine Kobresia parva meadow revealed that(1)at different grazing intensities the aboveground biomasses extremely significantly differed from the total aboveground biomass in different plant groups,the aboveground biomass percentage compositions of Cyperaceae plants extremely significantly differed,and the aboveground biomass percentage of Gramineae plants significantly differed from those of forbs;furthermore,the aboveground biomasses and their percentage compositions of Gramineae and Cyperaceae plants(except control plants) decreased as the grazing intensities decreased and those of forbs appeared to be vary in an opposite manner;(2) The quality forage percentages and grassland quality indexes appeared negatively correlated with the grazing intensities and the annual quality forage percentages appeared positively correlated with the annual weight gains of yak;(3) The community-similarity coefficients decrease as the grazing intensities increased.It was thought by means of the establishment of the indexes for vegetation measurement that annual quality forage percentage was the direct indicator for evaluating the grazing value of alpine Kobresia parva meadow and the variations in similarity index and grassland quality index did not have a remarkable relation to yak productivity,so that they were only capable of indicating the relative variation of plant communities as a whole other than being able to reflect the variation in the grazing value of grassland vegetations.The grazing intensity of yak was approximately 1.86 yaks per hectare,the maximum grazing intensity at which alpine Kobresia parva meadow could keep sustainable production and suffer non degeneration.