Assessment of damage caused by plateau zokor to an alpine meadow in eastern Qilian Mountain

Alpine grassland is an important and characteristic ecosystem of the Qinghai-Tibet Plateau,but has been severely degraded by the combined effects of climate change,human activity,over-grazing,and rodent damage. The plateau zokor( Myospalax baileyi) is one of the dominant rat species of the Qinghai-Tibet Plateau and has an important influence on alpine grassland ecosystems. At present,the damage to alpine meadow caused by plateau zokor is unclear,and few studies have assessed this. To objectively assess the damage to alpine meadow caused by plateau zokor,the effect on the yield of grass,plant diversity,soil,and suitable sampling area should be assessed. The present study analyzed the relationship between zokor population density and meadow quality on the eastern Qilian Mountain. Three paddocks with different zokor population densities were selected to investigate three variables of zokor damage( mound number,mound area and biomass on mounds),and six variables of habitat factors( biomass,coverage,botanical components,edible forage yield,soil moisture,and soil compaction). The relationship between variables and factors was determined using a one-way ANOVA.The results showed no significant differences between the three paddocks with different population densities( P 0. 05) in aboveground biomass, total coverage, edible forage yield, biomass on the mounds, botanical components, and the proportion that new mound areas occupied of the total investigated area of paddock. Generally,there were no significant differences in grassland quality between the three density areas. Regarding the influence of plateau zokor on the soil,except for the depth of zokor foraging in soil( 0-20 cm),there was no significant difference in soil compaction between the three paddocks( P 0. 05). However,there were significant differences in soil moisture at a soil depth of 0-30 cm between the three paddocks( P 0. 05),where the moisture increased with the increase in plateau zokor population density. The results indicated that the quality of the sampled paddocks was not significantly different under three zokor population densities in the study area. The present study indicated that the damage to alpine meadow caused by plateau zokor is not necessarily more serious at high population densities. A hazard rating for plateau zokor should be determined for the comprehensive treatment of damage to alpine meadows. Moreover,the sample size could also affect the results of the survey. The present s