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

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.