Response Of Plant Community To The Clipping Behavior By Plateau Pika In Alpine Meadow

Plateau pika(Ochotona curzoniae)is an endemic and small herbivore in the Qinghai-Tibetan Plateau,and is an important component of the alpine meadow ecosystem in this plateau,and the activites of this small animal can affect the plant community of alpine meadow.Clipping is a behavior of plateau pika by which plateau pika often bites off tall and upright plants around the active burrow entrance to keep an open vision for finding their predator,which can inevitably alter the composition and structure of plant communities around active burrow entrance.However,the current knowledge about the clipping behavior by plateau pika is limited to the discovery of its natural enemies,and how clipping behavior impacts plant community of alpine meadow receives little attention.Therefore,examining the effect of clipping behavior by plateau pika on plant community is an indispensable to completely reveal plant community of alpine meadow in relation to activites of plateau pikas.Since plateau pikas can live in many types,topography and microclimates,this study selected the alpine meadows at Gangcha County and Gonghe County in Qinghai Province and Luqu County in Gansu Province to investigate the the effects of clipping behavior by plateau pika on plant community component,plant community characteristics,plant group characteristics,and plant population characteristics,avoiding soil,topography and microclimate effects,which can discover the general pattern concerning plant community in relation to the clipping behavior by plateau pika,and provide the basis of effective information for the mechanism of plateau pika affecting alpine meadow.The main conclusions are as follows: 1.The clipping behavior by plateau pika increased the number of plant species and decreased the important value of dominant species in plant communityThe effects of clipping behavior by plateau pika on the number of plant species and the important value of dominant species in plant community were similar among three sites.The clipping behavior by plateau pika increased the number of plant species in plant communities at Gangcha County,Gonghe County,and Luqu County,and the new species were weed.The number of plant species increased by 12.0%,10.0% and 19.2% at Gangcha County,Gonghe County,and Luqu County,respectively.The clipping behavior decreased the important value of dominant Kobresia pygmaea at each site,and decreased by 10.2%,13.0% and 21.1% at Gangcha County,Gonghe County,and Luqu County,respectively,whereas Kobresia pygmaea was still the dominat among all species at each site.2.The clipping behavior by plateau pika increased the plant cover,species richness index and diversity index,decreased the plant height,and had no effect on species evenness index and biomass of plant communityThe effects of clipping behavior by plateau pika on plant height,cover,and biomass and species diversity were similar among three sites.The clipping behavior by plateau pika increased plant cover,species richness index and diversity index of plant community,and increased by 4.2%,10.0%,and 4.3%,respectively.The clipping behavior decreased plant community height with 3.7%,whereas the clipping behavior had no effect on species evenness index and biomass of plant community.These indicate that the clipping behavior by plateau pika increased plant species diversity,whereas it had no significant effect on plant community productivity.3.The effect of clipping behavior by plateau pika on characteristics of plant groups was differentThe effects of clipping behavior by plateau pika on characteristics of each plant group were similar among three sites.The clipping behavior by plateau pika decreased the height,cover,plant biomass,species diversity index and evenness index of graminoid group and decreased by 7.8%,7.6%,7.2%,7.5% and 5.5%,respectively.However,the clipping behavior had no significant effect on the species richness index of the graminoid group and the height of forb group at each site,but it increased cover,plant biomass,species richness index,species diversity index and evenness index of the forb group,and increased by 11.4%,10.2%,13.3%,9.0% and 2.9%,respectively.These results show that the clipping behavior can reduce the grazing quality of alpine meadow.4.The clipping behavior by plateau pika decreaed the niche width of dominant species,increased the niche similarity coefficient and the niche overlap coefficient,and encouraged the overall interspecific association to turn into from uncorrelated at abondaned burrow entrances to negative correlation at active burrow entrancesThe effects of clipping behavior by plateau pika on the niche width of dominant species,the niche similarity coefficient and the niche overlap coefficient of the population,and the overall interspecific association were similar among three sites.The clipping behavior by plateau pika decreaed the niche width of dominant Kobresia pygmaea in plant community,whereas it increased the niche similarity coefficient and the niche overlap coefficient of the population at each site.The niche width of Kobresia pygmaea decreased by 0.2%,0.1% and 1.1% at Gangcha County,Gonghe County,and Luqu County,respectively.The average niche similarity coefficient increased by 26.6%,12.5% and 14.7% at Gangcha County,Gonghe County,and Luqu County,respectively.The average niche overlap coefficient increased by 20.6%,8.0% and 7.6% at Gangcha County,Gonghe County,and Luqu County,respectively.The clipping behavior encouraged the overall interspecific association between plants species from non-significantly positively correlated to be significantly negative correlated.These results indicated that the clipping behavior reduced the ability of dominant species to utilize resources,strengthened inter-species competition in plant community,and encrouaged plant community to be more instable.In summary,the data from multiple sites have confirmed that the clipping behavior by plateau pika strengthened inter-species competition,reduced the relative stability of plant community though increasing the niche similarity coefficient and the niche overlap coefficient of population,and encouraging the overall interspecific association from uncorrelated at abandoned burrow entrances to negative correlation at active burrow entrance.The clipping behavior deteriorated the grazing quality of alpine meadow since it decreased the plant biomass of graminoid group,whereas it increased the plant species diversity.Therefore,the clipping behavior by plateau pika is one of the important ways to affecting the plant community of alpine meadow in the Qinghai-Tibetan Plateau.