Relations of density of pika burrows with plant community structure and soil in alpine meadows on the eastern Qinghai-Tibetan Plateau

The density gradient of pika (Ochotona curzoniae) burrows was determined using effective number of caves method (which were expressed from low to high as levelⅠ, Ⅱ, Ⅲ and Ⅳ respectively). To explore the effects of pika activity on the soil and vegetation of alpine meadows in Guoluo Tibetan Autonomous Prefecture, China, the relationships between the density of pika burrows and the total area of patchy bare ground, soil physical characteristics, and vegetation characteristics of alpine meadow were analyzed. The results showed that 1) The number of effective pika burrows across the four gradients was Ⅰ (4 ± 3)·100 m^–2 < Ⅱ(15 ± 2)·100 m^–2 < Ⅲ (24 ± 2)·100 m^–2 < Ⅳ (37 ± 5)·100 m^–2. 2) The soil water content in the surface layer of the meadows (0–10 cm) was affected by the pika burrow density gradient, and the difference between the gradients was significant (P < 0.05). With an increase in the density gradient of pika, the soil water content decreased sharply and remained below 50% in Ⅱ, Ⅲ, Ⅳ sampling plots. 3)There was no significant correlation between the pika burrow density gradient and the soil compaction of alpine meadows (P > 0.05); only gradient Ⅱ was significantly higher than gradient Ⅰ(P < 0.05), and the other gradients were not significantly different from each other. 4)The effective burrow number had an extremely significant effect on the total area of patch bare ground (P < 0.001), which was the largest at gradient Ⅳ(accounting for 8.75%); 5)The mouse cave density gradient had a significant effect on the coverage of alpine meadow communities (P < 0.001), and the total coverage of plant community at gradients Ⅱ, Ⅲ, Ⅳ(46.55%～41.15%) was significantly lower than gradientⅠ (98.7%); 6) The pika burrow density gradient affected the plant community structure of the alpine meadows. With an increase in the pika burrow density, the populations of Gentiana macrophylla, Elymus nutans, and Veronica eriogyne gradually increased and that of Chamaesium paradoxum, Viola kunawarensis, and Trollius farreri gradually declined, although the populations of the dominant species Kobresia pygmaea and Kobresia humilis did not change. 7) There was no significant difference of plant diversity index between different gradients (P > 0.05). In summary, properly managed pika populations can improve the habitat of the pika and promote the positive succession of the alpine meadow ecosystem. When the disturbance from pikas is too high, the resultant decline in habitat quality will cause the alpine meadow ecosystem to reverse succession.