| The plateau pika(Ochotona curzoniae)is a key species in the Qinghai-Tibet Plateau,and its digging and foraging behaviors often aggravate the degradation of alpine meadow.The caves of plateau pika are widely distributed in the alpine region and become an important landscape feature of alpine meadow ecosystem.At present,it has been confirmed that the caves have positive or negative impacts on the vegetation and soil in alpine meadow ecosystem,but the influence of plateau pika caves on slope hydrological process and alpine meadow ecosystem multifunctionality in alpine region remains unclear.Taking the caves as the research object,this study explored the differences in vegetation communities,soil hydrothermal conditions,soil physical and chemical properties of the alpine meadow under the different positions of the pika cave(the pika cave entrance and the pika cave burrow).The process and mechanism of water storage and flow production in burrow,and the effects of pika caves on ecosystem multifunctionality was evaluated.The main results are as follows:(1)The pika cave promoted the invasion and diffusion of forbs,and reduced the stability of the alpine meadow vegetation community by weakening the dominance of sedges.The vegetation coverage decreased by pika cave in alpine meadow.and the plant coverage above the cave entrance and the burrow was 73.64% and 90.41% of that of the native alpine meadow.Compared with the native alpine meadow,the belowground biomass from 0-10 cm of the cave entrance decreased by 62.90%,and the aboveground biomass above the burrow decreased by 23.58%.The pika burrow increased the richness of plant species in the alpine meadow,and 51 plant species appeared in the hole,which was much 54.55% higher than the 33 species in the original alpine meadow.Compared with the native alpine meadow,the ShannonWeiner index and functional group evenness of forbs in pika entrance were significantly increased by 7.79% and 9.38%,respectively,while the functional group evenness of sedges was significantly decreased by 10.53%.Compared with the native alpine meadow,the species asynchrony at the pika entrance increased by 6.33%,while the species asynchrony above the burrow decreased by 7.59%,and the community stability decreased by 62.61% and 50.04%,respectively.(2)The plateau pika burrow changed the water and heat conditions of the alpine meadow and damaged the thermal insulation property of the alpine meadow.The daily mean temperature of the growing season decreased by 0.59-0.85 ℃,and the minimum temperature at night decreased from 12 ℃ to less than 10 ℃,which aggravated the fluctuation of daily mean temperature of soil.Pika caves resulted in desiccation of the surface soil of the alpine meadow,and the soil moisture content of0-10 cm above the burrow significantly decreased by 8.85%.However,the break of mattic layer increased the water content of the deep soil of the entrance and the burrow by 101.18% and 23.08%.(3)The pika caves changed the physical and chemical properties of the alpine meadow soil,resulting in the reduction of soil quality,and promoting the degradation of the alpine meadow.The bulk density of 0-10 cm soil at the entrance increased by13.60%,the total porosity of soil and the average weight diameter of aggregate decreased by 4.69% and 22.58%,respectively.The sand content in surface soil increased,and the water retention capacity decreased.Pika burrowing disturbed soil and increased soil non-capillary porosity.The non-capillary porosity of 0-30 cm soil increased by 22.47% and 7.59%,respectively,under the influence of cave entrance and tunnel.The pika cave reduced the content of soil organic matter in 0-30 cm soil layer by 19.39% and 10.21%,respectively.The index of soil physical quality following: alpine meadow > burrow > entrance.(4)The pika cave destroyed the impermeability of mattic layer,promoted the water infiltration by changing soil properties,and then shifted the slope hydrological process.Compared with alpine meadow,the entrance and burrow increased the average water infiltration rate by 2.2 times and 3 times,respectively.Non-capillary porosity and burrow depth were positively correlated with soil infiltration rate,while belowground biomass and soil organic matter content were negatively correlated with soil infiltration rate.According to the "Fill and Spill" model,the burrow had a certain capacity to store runoff,with an average water storage coefficient of 45.49%.The water storage and flow production capacity of pika burrow was changed by burrow structure indexes such as the number of burrow entrance,burrow linearity,microtopographic volume and water flow length.The linearity of burrow is positively correlated with runoff,and the number of water intakes is positively correlated with water storage and water storage coefficient.(5)The effects of different parts of burrow on ecosystem function indexes were various.Plateau pika burrow reduced the carbon sequestration function of the ecosystem.The water conservation function and biodiversity protection function were improved,and soil physical quality index was seriously reduced in entrance,while the productivity supply function of the ecosystem was reduced in burrow.Overall,the burrow reduced the multifunctionality of the alpine meadow ecosystem.In conclusion,the plateau pika burrow exerts different effects on the productivity supply,biodiversity conservation,carbon sequestration,soil structure maintenance and water conservation and other ecosystem functions by affecting the vegetation species composition and community structure of the alpine meadow,changing the hydrothermal conditions,reducing soil physical properties and organic matter content,and regulating the slope hydrological process.Therefore,it is beneficial to the healthy and sustainable development of alpine meadow ecosystem in the headwaters of Three rivers headwaters region to take appropriate measures to control the population of plateau pika. |
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