牦牛放牧强度对甘南高寒草甸群落特征与牧草品质的影响

摘要

To study the effects of the intensity of yak grazing on the characteristics of plant communities and forage quality in alpine meadows under the effect of long-term yak grazing in the Qinghai-Tibetan Plateau (Maqu County,Gansu Province),this study analyzed aboveground and belowground biomass,species rich-ness,density of plant communities,surface soil water content at a depth of 0—10 cm,soil temperature,nutri-tive quality of forage,and correlation among other aspects.The results showed that:1)Yak grazing signifi-cantly (P<0.01)affected above- and belowground biomass.Aboveground biomass was the highest in the non-grazed area (418.15 g?m—2);contrastingly,belowground biomass was significantly higher (P<0.05)in the farm with high-intensity grazing compared with the other area.2)The density of plant communities and pro-portion of the biomass of edible grass were not significantly (P>0.05)affected by grazing,while species rich-ness was significantly reduced in the farms with moderate and high-intensity grazing compared with the non-grazed area.Moreover,surface soil water content at a depth of 0—10 cm was significantly (P<0.05)lower in the farm with high-grazing intensity compared with the non-grazed area,and contrastingly soil temperature was significantly higher.3)The intensity of yak grazing similarly affected forage quality;however,the difference was not significant (P<0.05)under the effect of long-term yak grazing.Therefore,yak grazing with moderate intensity may effectively promote the growth of underground biomass,which potentially affects different eco-nomic groups,biomass proportion,and forage quality,and maintains the health of the ecosystem.%为探究长期牦牛放牧干扰对高寒草地的影响,本研究分析了不同放牧强度下的牧草地上、地下生物量,植物物种丰富度、种群密度,表层(0—10 cm)土壤含水量、土壤温度,以及牧草营养品质等.结果表明,1)牦牛放牧强度对牧草地上、地下生物量有极显著影响(P<0.01).其中,在放牧压力为零的对照区牧草地上生物量最大,约418.15 g?m—2;在高强度(6.5牦牛?hm—2)放牧下,牧草地下生物量显著高于其他各处理(P<0.05);2)高强度放牧干扰降低了植被物种丰富度,但对植被群落密度、可食与不可食牧草生物量比重影响不显著(P>0.05);放牧强度对高寒草甸表层土壤(0—10 cm)含水量和地表温度(0—10 cm)有显著影响(P<0.05),随着放牧强度增大,表层土壤含水量总体呈下降趋势,地表温度呈递增趋势;3)放牧强度对牧草品质也有一定影响,但各放牧强度之间差异不显著(P>0.05).因此,适宜强度的牦牛放牧可能会促进牧草地下生物量生长,潜在影响不同经济类群的比重,维持高寒草甸生态系统健康.