Relations Of Density Of Pika Holes With Plant Community Structure And Soil In Alpine Meadows On The Eastern Qinghai-Tibetan Plateau

The density gradient of pika(Ochotona curzoniae)holes was determined by the method of effective number of caves(which were expressed from low to high by I,II,III and IV level respectively).In order to explore the effects of pika activity on the soil and vegetation of alpine meadows in Guoluo Tibetan Autonomous Prefecture,and to scientifically understand the problem of pika,rationally divide the boundaries of harm of pika and provide data support for the balance of grass and livestock in Sanjiangyuan District,the relationship between the density of mouse caves and the total area of patchy bare ground,soil physical characteristics and vegetation characteristics of alpine meadow was analyzed.The results showed that:1)The number of effective mouse caves in the four gradients was?(4±3/100m~2)<?(15±2/100m~2)<?(24±2/100m~2)<?(37±5/100m~2);2)The effective cave number had extremely significant effect on the total area of patch bare ground(P<0.001),which was the largest(8.75m~2)under gradient?;3)The soil water content in the surface layer of meadow(0-10 cm)was affected by the mouse cave density gradient,and the difference between the gradients was significant(P<0.05).With the increase of density gradient of pika,the soil water content decreased sharply and remained below50%at the II-IV sampling plots;There was no significant correlation between the mouse cave density gradient and the soil compaction of alpine meadows(P>0.05),only gradient II was significantly higher than gradient I(P<0.05),and the other gradients were not significantly different from each other(P>0.05);4)The mouse cave density gradient had significant effect on the organic matter content of surface soil(P<0.05),the difference between gradient III and other gradients was significant(P<0.05),and the difference between gradients I,III and IV was not significant(P>0.05);5)The mouse cave density gradient had significant effect on the total carbon and total nitrogen content of soil surface(P<0.05).The difference of soil total carbon content in 10-20 cm soil layer and the mouse cave density gradient was not significant(P>0.05);6)The mouse cave density gradient had a significant effect on the coverage of alpine meadow communities(P<0.001),and the total coverage of plant community in gradient II-IV(42.25%—57.75%)was significantly lower than gradient I(97%);7)The mouse cave density gradient had significant effects on the aboveground biomass of alpine meadow vegetation(P<0.05),the difference between gradient I-III was not significant(P>0.05),and the difference between gradient IV and other gradients was significant(P<0.05);8)The mouse cave density gradient had significant effects on species richness and Shannon-Wienner index(P<0.05),but had no significant effect on Simpson index and Pielou index(P>0.05);9)The mouse cave density gradient affected the plant community structure of alpine meadow.With the increase of mouse cave density,although the important status of the dominant species Kobresia pygmaea and Kobresia humilis had not been changed,the important values of associated species Gentiana macrophylla,Saussurea hieracioides and Ligularia virgaurea were gradually increased,and Chamaesium paradoxum,Veronica ciliata and Plantago asiatica were gradually withdrew from the community structure;10)The results of principal component analysis showed that patch bare land,soil moisture content,soil organic matter,vegetation community species and total coverage were the main influencing factors for habitat selection of the pika.In summary,proper pika interference can improve the habitat of the pika and promote the positive succession of the alpine meadow ecosystem.When the disturbance of pika is too high,the decline of habitat quality will force the alpine meadow ecosystem to reverse succession.