| The alpine meadow on the Qinghai-Tibet Plateau is one of the important pastoral areas in China and it is an important material basis and natural production base for the development of animal husbandry.Grazing livetock dung is collected in large quantities as an important local energy material,which seriously damages the nutrient cycling process of the alpine grassland ecosystem and the healthy and sustainable development of the grassland.In recent years,with the rapid development of animal husbandry and the transformation of energy policies and the improvement of residents’ consumption levels,the energy consumption of traditional livestock excrement has decreased,resulting in a large amount of grazing livetock dung will be retained on the grassland in the future.Therefore,it is of great scientific significance to explore the ecological benefits of yak and sheep dung retention under the background of human activities for the recycling and sustainable development of the ecosystem of the Qinghai Tibet Plateau.Taking the alpine meadow on the Qinghai Tibet Plateau as the research object,different types of dung(yak dung and Tibetan sheep dung)and different retention(high retention and low retention)treatments were set up in September 2019.The changes of community structure and soil properties of alpine meadow after yak and sheep dung retention were systematically studied,and the effects of yak and sheep dung retention on species diversity,aboveground-underground productivity of the alpine meadow,community heterogeneity and soil quality changes were comprehensively analyzed and evaluated,.The trade-off relationship of its ecological functions and its overall ecological benefits were comprehensively analyzed and evaluated,and the main influencing factors and action processes were explored.The main conclusions of this study were as follows:(1)The retention of yak and sheep dung effectively improved the physical and chemical properties of the alpine meadow soil and improves the soil quality of the alpine meadow.Among them,the low retention of sheep dung increased the mesroaggregates and microaggregates by 8.5%,while the high retention of sheep dung increased 11.6%.The increase of mesroaggregates and microaggregates improved the aeration and water vapor exchange of the soil,increased soil moisture content.The accumulation of yak dung can better improve soil fertility.By effectively increasing the content of soil available nutrients(the organic matter content of the low and high rentention of yak dung increases by 18.92% and 29.26%,respectively,the total nitrogen increases 12.85% and 12.94%),it could improve the nutrient pool and biological activity of the originally poor and shallow soil,and improved the biological viability of the alpine meadow.The comprehensive analysis results showed that the soil quality retained by yak dung is 37.22% higher than that of sheep dung,and with the increase of retention,the soil quality retained by sheep dung improved 0.21%,while the soil quality retained by yak dung improved by 10.41%.(2)The retention of yak and sheep dung increased the species richness of the alpine meadow community,improved the community structure,and improved the heterogeneity of the community.On the premise of continuing to maintain the dominant position of the two dominant functional groups: Gramineae functional group and Composition functional group in the alpine meadow,the retention of yak and sheep dung also increased the species composition and richness of community,and promoted the greening and development,such as Thalictrum aquilegiifolium var.sibiricum Linnaeus and Lancea tibetica Hook.F.et Thoms.Compared with the control,the average community height with low retention of sheep dung,high retention of sheep dung,low retention of yak dungand high retention of yak dung decreased by-7.55%,-0.66%,-34.91%,-25.46 %,respectively,while the community heterogeneity with low retention of sheep dung,high retention of sheep dung,low a retention of yak dung,and high retention of yak dungincreased by 76.60%,5.06%,62.64% and 92.40%,respectively.(3)The retention of yak and sheep dung changed the trade-off relationship between original ecological functionsof the alpine meadow ecosystem,and improved the ecosystem service function.Specifically,the effect of yak dung retention on soil quality is greater than that of sheep dung,and the effect of sheep dung retention on community structure is smaller than that of yak dung retention,so the ecosystem benefits of alpine meadows under the treatment of yak dung accumulation were more inclined to the benefits of soil quality,followed by the benefits of species diversity;the ecosystem benefits of alpine meadows under the cumulative treatment of sheep dung were more inclined to the benefits of species diversity.The comprehensive analysis showed that the high retention of sheep dung made the ecological functions of the alpine meadow ecosystem more balanced and stable.Overall,the retention of yak and sheep dung effectively improved the site conditions and soil fertility of alpine meadows,increased species richness,improved the three-dimensional structure of the community,increased the community heterogeneity,and changed the original ecological balances and functional trade-offs optimize the ecological service function of the alpine meadow ecosystem,especially when the retention of sheep dung is high,it is easier for the alpine meadow ecosystem in a balanced and stable manner. |
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