垂穗披碱草／星星草混播草地优化牦牛放牧强度的研究

A study on optimal grazing intensity for yak in Elymus natans/Puccinellia tenuflora mixed-sown undegraded grassland in the forage growing season based on vegetation and yak productivity

以植被和牦牛生产力变化为目标研究草地不退化的最大放牧强度,在垂穗披碱草/星星草高寒混播草地3年的牦牛放牧试验结果表明,1)优良牧草比例和牦牛个体增重的平均年度变化随放牧强度的增加而减小,牦牛个体增重和优良牧草比例的平均年度变化之间存在着正相关,因此确立了不同放牧强度下优良牧草比例的年度变化是评价高寒混播群落放牧价值的直接度量指标。2)虽然群落相似性系数和草地质量指数可以评价草场的相对变化,但相似性系数的变化与牦牛个体生产力没有显著关系,因而不能反映草场放牧价值的变化,而计算草地质量指数时,不同植物类群盖度的测定和适口性的判别受人为因素的干扰较大,因此它也不是一个很客观的指标。3)当放牧强度为9.97头/hm2时,优良牧草比例和牦牛个体增重的年度变化能维持基本不变,因此,可以认为该放牧强度是高寒人工草地生长季放牧不退化的最大放牧强度。

A grazing trial of yaks for three grazing seasons in an Elymus natans/Puccinellia tenuflora mixedsown grassland showed that： 1） The average annual changes for the ratio of good quality forage and live-weight gain per yak reduced with an increase of grazing intensity, and the average annual change of live-weight gain per yak was positively correlated with the average annual change of ratio for good quality forage. Therefore, the annual change for the ratio of good quality forage grazing values under different grazing intensities in was established as a direct measuring index for evaluating alpine mixed-sown grassland; 2） Although a similarity index of community and grassland quality index could evaluate relative changes of grassland, there was no obvious relationship between change of similarity index and productivity per yak, so it did not reflect the change of grazing value. Moreover, estimate of edibility were when calculating grassland quality index, the measure of different plant groups and disturbed by artificial factors, thus it was not an external index; 3） A grazing intensity of 9.97 head/hm^2 could maintain the annual change of the ratio for good quality forage and live-weight gain per yak, and should be considered the maximum grazing intensity for undegraded alpine artificial communities in the plant growing seasons