The Study On Trade-Offs And Synergies Between Carrying Livestock And Soil And Water Conservation Functions From Grass Ecosystem In The Three Rivers Headwaters Region

With the development of the economy and human society,humans' excessive demand for ecosystems affects the structure,functions and processes of ecosystems,causing various ecological and environmental problems.The study of ecosystem service trade-off and synergy has become a key scientific issue in geography and ecology.The Three Rivers Headwaters Region(TRHR)is a typical ecologically fragile area and an important ecological function source area for the sustainable development of the TRHR Basin.Therefore,quantitative analysis of its ecosystem service trade-offs and synergies is of great significance for achieving regional sustainable development.Taking the second-stage ecological conservation and restoration project in the TRHR as an example,based on multi-source data such as meteorology,remote sensing and elevation,the relevant models were used to quantitatively measure grassland ecosystem grassland supply,soil erosion,wind erosion and water source in the TRHR from 2000 to 2014.Conservation services,analyze the spatial pattern and evolution characteristics of service functions before and after ecological engineering,and explore the contradictory changes of grassland animals;then use multiple linear regression analysis and spatial partial correlation analysis to analyze the impact of climate and vegetation factors on ecosystems,and explore The spatial and temporal characteristics of trade-offs and synergies between services;finally,the effects of different stocking capacities on soil erosion are simulated to provide guidance for the coordinated and sustainable development of grassland ecosystem services.The main conclusions are as follows:(1)From 2000 to 2014,the pasture supply service,theoretical stocking capacity,water conservation,and soil erosion in the TRHR showed a pattern of southeast-northwest decline,and the overall trend showed an increasing trend;however,the amount of wind erosion showed a downward trend.The theoreticalcarrying capacity is increased,the actual carrying capacity is reduced,the livestock load index is lowered,and the contradiction between grass and livestock is alleviated.(2)Since the implementation of ecological engineering in 2005,the amount of grass production and water conservation has been significantly improved,and the soil retention function has been strengthened.After the implementation of the grass yield project,it increased by 30.1%compared with that before the implementation,and increased to the largest in the northeast region.Since the reduction of livestock production,the theoretical carrying capacity has increased,the actual carrying capacity has decreased,and the carrying animal pressure index has decreased,which is 5.12% lower than that before the project,but it is still overloaded as a whole.The growth rate of soil erosion is gradually decreasing,and the growth rate is from 0.23 billion t/a to 0.049 billion t/a,and the soil retention function is strengthened.The amount of wind erosion first increased and then decreased,from 152 million t/a before the project to-0.45 billion t/a after the project was implemented,and the amount of wind erosion gradually decreased.The water conservation capacity has increased significantly,increasing by19%.The water conservation capacity has stabilized in the five years after the project is implemented.This indicates that the ecological status of TRHR has gradually improved,but there are obvious spatial differences in the changes of ecosystems.The ecological engineering and livestock reduction projects have achieved initial results.(3)Climate and vegetation factors are the main factors affecting the functional changes of ecosystems.However,with the differences in dry and wet conditions in the region,there are regional differences in the dominant factors and extent of the ecosystem.Among them,temperature and precipitation affect the change of grass yield,precipitation is negatively correlated with grass yield,temperature is the dominant factor;soil erosion is related to temperature,precipitation,vegetation coverage,precipitation is the dominant factor affecting soil erosion;soil wind erosion and Temperature and wind speed are positively correlated,and negatively correlated with vegetation coverage.Wind speed is the main factor affecting wind erosion degree;theincrease and decrease of water source conservation is directly affected by precipitation and potential evapotranspiration.However,there are spatial differences in the extent and dominant factors affecting ecosystem service change factors in different regions.(4)From the scale of the study area,the grass yield and the soil erosion have a trade-off relationship,and the grass yield is synergistic with wind erosion and water conservation.From the perspective of space,there is obvious spatial heterogeneity;the yield of grass and soil erosion are characterized by the pattern of “ East Weighing-Western Cooperation ”;the amount of grass yield and wind erosion are expressed as “most of the synergy of the whole region – the balance between east and west ” The amount of grass production and water conservation is a rule of differentiation of “most of the synergies in the whole region—the balance of the northwest part”.Under each grassland type,the grass yield and soil erosion and wind erosion are mainly based on the trade-off relationship,and the synergy relationship is mainly related to the water source conservation,but there are obvious differences.(5)There is a big difference in the relationship between actual carrying capacity and soil erosion,wind erosion and water conservation in the TRHR.The actual carrying capacity and soil erosion are in a synergistic relationship,among which Zaduo County is significantly synergistic;In a synergistic relationship,Banma,Jiuzhi,Zeku,etc.are significantly synergistic;they have a trade-off relationship with water conservation,and Banma,Malang,Gande,etc.are significant trade-offs.(6)With the increase of the stocking capacity,the degree of soil erosion and the total amount increase,and the change of the Langcang River basin is the most obvious.In order to maintain the sustainable development of the TRHR,it is necessary to focus on the treatment of soil erosion and to adapt to local conditions.