The plateau pika (Ochotona curzoniae) is a common small mammal species present in the alpine meadow ecosystem on the Qinghai-Tibetan Plateau (QTP), and is regarded as a pest in alpine meadows when population density exceeds a certain threshold. However, whether pikas with a low population density have a detrimental effect on alpine meadows in winter pasture is unknown. Vegetation and soil were sampled in eight individual pika patchy home ranges and eight control areas, and we found vegetation and soil properties showed different trends in the pika home ranges. Plateau pika activity significantly increased the below-ground biomass, soil pH and total potassium, but had no significant effect on the plant species richness or diversity, soil moisture, NH4-N, NO3-N, total phosphorus, available phosphorus and soil organic content. However, plateau pika activity reduced some vegetation and soil properties (e.g. vegetation cover, vegetation height, aboveground biomass, graminoids, soil bulk density and available potassium). These results imply that pika activity may improve some soil nutrients but have no destructive effect on winter pasture at a low population density.

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Plateau pikas are a keystone species and ecosystem engineers in alpine meadow ecosystems. A number of surveying methods have been used to estimate pika density, but the reliability of these methods is not known. In addition, better population density methodologies allow for more reliable density estimates. We therefore compared the relationship among several commonly used methods of estimating pika relative density and the absolute density (AD) of pika populations. This relationship was investigated in summer and winter pastures to determine whether distribution pattern of the pikas (patchy or uniform) would influence this relationship. During August of 2015 and August of 2016, we measured the relative and absolute population density of pikas in an alpine meadow in the County, Gansu province, northwestern China. Relative density was measured with three indirect and direct methods: the total burrow density (TBD), the active burrow density (ABD), and the direct counting density (DCD) at the peak of pika activity. AD was assessed by removal sampling. Our results showed that the relative population density with all three survey methods was significantly related to the absolute population density. In particular, DCD at the peak of the pika activity showed the best correlation with AD. A simple linear model showed the effect of grazing time by livestock had a significant effect on TBD and ABD. These results imply that using DCD as a method to survey at the peak of the pika activity is more reliable than other methods.