Effects of plateau pika activities on seasonal plant biomass and soil properties in the alpine meadow ecosystems of the Tibetan Plateau

摘要

The foraging and burrowing activities of small mammalian herbivores may have either detrimental or beneficial effects on grassland ecosystems;the direction of the effect is determined by the species, population abundances and fluctuations.Twelve survey sites with active burrow of plateau pika were classified into four degrees of density: approximately zero-density, low-density, medium-density and high-density, to evaluate the impact of different pika densities on vegetation, plant biomass, soil organic carbon and nutrients in a whole growing season.We show that pika activities caused a decrease in the number of plant species, vegetation cover, plant height and seasonal mean biomass.Values at the zero-density site were the greatest, while those with medium-density site were the lowest.With the exception of available potassium, soil organic carbon, nitrogen, total phosphorus and soil water content, zero-density areas were significantly higher than those of pika occupied areas, in which large pika populations may promote soil organic carbon and nutrients enhancement.However, there were slight or no differences in vegetation characteristics and soil properties between medium-and high-density sites.Our study suggests that low-density activity, with 110 pikas or/and 512 active burrows ha-1 could be regarded as an economic threshold abundance or density of pika control in practice.