Study On Soil Denudation And Plant Community Succession In Pika Mound

This paper analyzed the Succession law of Pika mound vegetation?denudation and properties of Pika mound soil under different temporal and spatial scale in Pika outbreak areas of alpine Kobresia meadow,to explore the responses of alpine grassland soil to plateau pika activities.The results showed that:The total coverage and plant height of the new Pika mound increased with the extension of the age of the mound.The coverage,height and biomass in the outer circle of Pika mound were higher than inner circle,and the inner ring is dominated by Annuals and biennials,and the outer ring is dominated by Forbs.The Shannon-Wienerh index decreased year by year with succession and was lower than native vegetation.The degree of succession was the highest in 3 years'Pika mound.The species richness index was the lowest in 3 years'Pika mound.The index of Shannon-Wienerhspecies richnessand degree of succession of the outer circle were higher than inner circle.This paper analyzed the denudation of pika mound soil under different temporal and spatial scale in pika outbreak areas of alpine Kobresia meadow,to explore the responses of rat mound soil to topography,climate and vegetation in alpine grassland.The height of rat mound decreasing during spring and summer and increasing during autumn and winter,In the fall of 2016,the height of the pika mound increased to20.36 cm.The diameter and surface area of the rat mound reached their maximum after the first winter and then gradually decreased and trend to stability,which were81.9 cm and 10235.21 cm~2,respectively.The denudation rate of rat mound soil was highest in Kobresia pygmaea grassland,followed by Elymus nutans grassland,and the forb dominated grassland had the lowest denudation rate.The order of the denudation rate for studied site was Menyuan County,Zeku County and Henan County,Flat beach is higher than sloping land,while the highest value was occurred only in summer for the second and third year.The amount of denudation by wind and water decreased gradually from the formation of mound.The soil texture of the Pika mound was mainly the sandy loam.The soil water content decreasedgradually with the succession of Pika mound.The bulk density of the Pika mound soil was also lower than that of the native vegetation.The soil tempe temperature of the first-year Pika mound was higher than that of the second-year.The content of soil organic matter and nitrogen in Pika mound was decreased from 3 years'Pika mound,through 2 years'to the 1 year's Pika mound.The total nitrogen content of the Pika mound increased gradually from spring to autumn,while the available nitrogen content reached the highest in summer.The total phosphorus content was gradually decreased after formation of the Pika mound,and the highest available phosphorus content was in the 1st year's Pika mound as well as summer.The highest value of soil potassium and soil total potassium for Pika mound was appeared in summerand in 1st year'srespectively.The content of available potassium increased with the duPikaion of Pika mound.