牦牛干扰下草原毛虫对小嵩草高寒草甸植物群落特征的影响

Effect of grassland caterpillar on the characteristics of the vegetation of Kobresia pygmaea alpine grassland under the interference of the yak grazing

采用野外受控放牧试验(放牧和不放牧)和人工控制草原毛虫(Gynaephora qinghaiensis)方法(草原毛虫移除和未移除),研究了牦牛干扰下草原毛虫对高寒草甸小嵩草(Kobresia pygmaea)草地植被群落(植被盖度、群落高度、地上生物量及植物多样性等)的影响。结果表明,在试验期内,草原毛虫种群数量随着时间的推移呈现出先增加后降低的趋势。在牦牛(Bos mutus)放牧区内草原毛虫种群数量及增长趋势均高于无牧区。草原毛虫单独存在时群落的盖度、高度及地上总生物量与对照(牦牛与草原毛虫都不存在,CK)差异不显著(P>0.05),而牦牛与草原毛虫共存时群落盖度、高度及地上总生物量都显著低于CK(P<0.05)。牦牛干扰了草原毛虫对群落中主要植物种的作用,植物重要值发生了显著变化。草原毛虫单独存在时植物多样性指数与CK间无显著差异,单独放牧牦牛和牦牛与草原毛虫共存时的植物多样性指数均显著低于CK(P<0.05)。本研究表明,牦牛显著加剧了草原毛虫对小嵩草高寒草甸植被的影响。

In this study, we investigated the effects of grassland caterpillar on the vegetation （community cover, height, above-ground biomass, and plant diversity） of a Kobresia pygmaea alpine grassland under the interference of yak grazing using artificial grazed methods （grazed and ungrazed） and caterpillar field control methods （caterpillar presence and absence）. The study included four treatments： yak alone （Y）, grassland caterpillar alone （C）, both yak and grassland caterpillar （YC）, and without yak and grassland caterpillar （CK）. The results showed that the density of grassland caterpillar increased during the first phase of the experiment and decreased thereafter. Density and growth trends of grassland caterpillar were higher in the grazed plots than ungrazed plots. There were no significant differences in community cover, height, and total above ground biomass between C and CK （P〉0.05）, but these values were significantly lower in YC. The important values of the main plant species were changed in YC. Plant diversity indices such as richness index, Simpson index, Shannon-Wiener index, and Pielou index were significantly lower in Y and YC compared to CK （P 〈0.05）. However, these four diversity indices were not observed in the C plots. Based on our findings, we conclude that yaks significantly affected the influence of caterpillars on the vegetation of the Kobresia pygmaea alpine grassland.