The disturbance and disturbance intensity of small and semi-fossorial herbivores alter the belowground bud density of graminoids in alpine meadows

Do semi-fossorial herbivores influence the trajectory of plant community succession by altering belowground bud density in alpine meadows? Field surveys were carried out to investigate the effect of disturbance and disturbance intensity of the plateau pika (Ochotona curzoniae) on the belowground bud density in alpine meadows at two sites. The Linear Mixed Model (LMM) test and Linear Model (LM) test were used to analyze the relative effect of plateau pika disturbance on bud density and to clarify the response of belowground bud density to disturbance intensity. Our results showed that disturbance by the plateau pika increased belowground bud density of graminoids and plants from the grass and sedge families, including Kobresia pygmaea and Elymus nutans, but had no effect on forbs bud density. The bud density of graminoids, grass and sedge plants, and K. pygmaea and E. nutans showed a downward parabolic trend in response to increased disturbance intensity of the plateau pika, implying that there was an optimal level of disturbance intensity that maximized belowground bud density of graminoids. These results suggest that disturbance by the plateau pika has different effects on belowground bud densities of graminoids versus forbs. Additionally, disturbance by plateau pika up to the optimal intensity may improve grazing quality of alpine meadow in the long term through increasing graminoid bud density, resulting in a higher proportion of graminoids in pasture, while higher levels of disturbance by plateau pika may deteriorate alpine meadows through a reduction in graminoid bud density.