The Responses Of Meadow Plant Communities And Soil To Density Changes Of Ochatona Curzoniae In Qinghai-Tibetan Plateau

As one of the key components of alpine meadow ecosystem, Ochatona curzoniae plays an important role in the stability and health of alpine meadow when its population density is below the warning threshold value, however, this small mammal causes the great disaster to alpine meadow when its population density surpass the warning threshold value. Therefore, it is important to determine the response of alpine meadow community and soil characteristics to changes of population density in Ochatona curzoniae for quantifying the warning threshold value. A field survey was conducted to disclose the relationship between soil, plant communities and population density of Ochatona curzoniae by measuring the species composition of plant community, cover, height, biomass characteristics, functional group, soil moisture, bulk density, particle size composition, pH, organic matter, N, P, K content and organic matter, and Main conclusions were drawn as following,Firstly, General height and cover of alpine meadow community firstly decreased and then increased with the increase of population density in Ochatona curzoniae, however, the biomass gradually decreased. The types of noxious weeds was the lowest, and the types of grasses and the important value of sedges was biggest when the burrow density was 14 number/625m2.Secondly, the richness index of plant community firstly decreased and then increased with the increase of population density in Ochatona curzoniae and the evenness index of plant community firstly increased and then decreased with the increase of population density in Ochatona curzoniae. However, the diversity index of plant community showed a peak and small peak when burrow density was 14 and 54 number/625m2, respectively. This study indicated that diversity index of plant community was the biggest when burrow density was 14 number/625m2 and three indexes were the lowest when burrow density was 34 number/625m2.Thirdly, The height of forage functional groups and poisonous weeds functional groups were all declined with the increase of population density in Ochatona curzoniae, and the cover of forage functional groups was lowest when burrow density was 34 number/625m2, and the cover of poisonous forbs functional groups was lowest when burrow density was 14 number/625m2. The forage biomass was not different at burrow density with 3 number /625m2 to 14 number/625m2, but significantly higher than those at burrow density with 34 number/625m2 and 54 number/625 m2 (P<0.05)Fourthly, the increase of Ochatona curzoniae density led soil water content of bare patches of 0-10cm layer to reduction, while the soil water content of bare patches of 10-20cm layer firstly increased and then declined. Soil silt percentage firstly increased and then decreased and sand percentage firstly decreased and then increased with the increase of population density in Ochatona curzoniae, in turn, pH value increased at first then decreased, indicating that rational burrow increased soil permeability, accelerated soil moisture to penetrate deeply, and increased the proportion of soil silt.Fifthly, soil organic matter, organic carbon and nitrogen content firstly increased and then decreased with increase of the density of Ochatona curzoniae, and peaking at 14 number/625m2 burrow density, while potassium and phosphorus content in soil did not respond to change of population density in Ochatona curzoniae, indicating that an rational amount of the plateau pika activities improved the soil nutrient.