不同强度短期放牧对高寒草甸植被特征的影响

Effects of different intensity of short-term grazing on vegetation characteristics of alpine meadow

为探索不同强度短期放牧对高寒草甸植被特征的影响,在碌曲县加仓村选择禁牧5年的高寒草甸草地作为试验样地,通过不同强度放牧试验,探究其地上生物量变化规律及其相互之间的关系,结果表明:对照组禁牧的地上生物量值最大,为1084 g/m^(2),当放牧强度不断增大时,地上生物量逐步减小;重度放牧物种丰富度、Shannon-Wiener多样性指数最低,中度放牧最高,与“中度干扰理论”相契合;禾草和莎草在中度放牧条件下密度最大,重度放牧使禾草物种丰富度和株高减小,与禁牧差异显著(P<0.05);杂类草在重度放牧条件下所占比重最高,其中,当放牧强度逐渐增大时,毒草和可食杂草物种丰富度明显减小,毒草密度随着放牧强度增大而增加,但差异不显著(P>0.05),重度放牧可食杂草密度与禁牧、轻度放牧差异显著(P<0.05);试验区出现的毛茛科植物绝大多数为毒草,其物种丰富度和密度表现出了和毒草相似的变化趋势,即物种丰富度逐渐下降,密度逐渐增加,禁牧株高与三个放牧实验组差异显著(P<0.05)。因此适宜强度的牦牛放牧可使草地植被结构与功能得以改善,当高寒草甸发生退化时,可利用围栏禁牧作为有效恢复手段。

This study explored the effects of short-term grazing with different intensity on the vegetation characteristics of alpine meadow,which had prohibited from grazing for five years and located at Jiacang Village,Luqu County,Gansu,China.The results showed that the aboveground biomass was highest in the non-grazed control(1084 g/m^(2)),and decreased gradually along with the increasing grazing intensity.The species richness and Shannon Wiener diversity index were the highest under moderate grazing,and lowest under heavy grazing,which was consistent with“the moderate disturbance theory”.The density of grasses and sedges was the highest under moderate grazing.Heavy grazing significantly reduced the species richness and plant height of grasses compared with the control group(P<0.05).With the increasing grazing intensity,the species richness of poisonous weeds and edible weeds decreased significantly.In response to the increasing grazing intensity,the density of poisonous weeds increased but not significantly(P>0.05),while the density of edible weeds was significantly higher than that of the control group and light grazing(P<0.05).Most Ranunculaceae plants in the experimental area were poisonous weeds,and their species richness and density showed a similar trend with poisonous grass.Plant height of the control group was significantly higher than that of the three grazing treatments(P<0.05).Therefore,yak grazing with appropriate intensity could improve the structure and function of grassland vegetation and alleviate grassland degradation.In face of severe grassland degradation such as the sharp decrease of biomass and the loss of biodiversity,fencing could be used as an effective way to stop grazing.