| The continuous supply of ecosystem services is the foundation of the sustainable development of human society.Since ecosystem services are the direct or indirect contribution of ecosystems to human well-being,there is a close relationship between ecosystem services and human well-being.In social practice,there is an urgent need to answer the following scientific questions related to ecosystem services,such as which services are provided by which ecosystems and where,how many and types? What is the public’s demand for ecosystem services? Who consumes and how much? service? Does the supply and demand of ecosystem services match? For a long time,due to people’s lack of understanding of the importance of ecosystem services,the excessive use of natural resources has caused many problems and affected regional and even global ecological security.The traditional economic value evaluation is developing towards the research direction of deep coupling with the social economic system.Studying the supply-demand relationship and risk characteristics of ecosystem services can not only give priority to the initiative in development and promote the increase of human well-being,but also have important significance for the management of regional ecosystems and the effective allocation of resources.Thus,this article takes the Yi River Watershed,a tributary of the Yellow River Basin,as the research area,and selects water yield（WY）,carbon sequestration（CS）,food production（FP）and soil conservation（Soil conservation,SC）.)Serving 4 types of ecosystem services（Ecosystem services,ES）,using GIS platform and related models,combined with the physical geographic data and social statistics of the Yi River Watershed,to quantitatively evaluate the supply and demand in 2000,2008 and 2018,from Analyze the temporal and spatial distribution of ecosystem service supply and demand at the grid and sub-basin scales,reveal the temporal and spatial evolution of the ecosystem service supply and demand relationship,and further identify the four key ecosystem service supply and demand risk conditions,and divide the space management zone of the Yi River Watershed.Provide a foundation for the construction and optimization of the security pattern of ecosystem services in the river basin.The main conclusions of this article are as follows:（1）Temporal and spatial changes of ecosystem service supply.Spatial changes: From 2000 to 2018,the spatial pattern of the service demand for the four ecosystems in the Yi River Watershed was basically stable.The southwestern region for water production,carbon sequestration,and soil conservation services was higher than the northeast region,and the upstream water production service supply capacity was stronger.The food production service space is higher in the northeast and lower in the southwest,and the supply capacity of downstream food production is higher than that in the upper and middle reaches.Time-series changes in quantity: the total water production supply decreased from 10.71×108 m3/a in 2000 to 9.02×108 m3/a in 2018,a decrease of 15.78%.The water production service supply segment showed a first decrease and then an increase 25 th.The sub-basin is the area with the largest decrease in the supply of water production services,and the 8th sub-basin has the least decrease;the total supply of carbon sequestration services dropped from 4.10×108 t·C/a in 2000 to 4.08×108 t·C/a in 2018 a,a decrease of 0.49%,the carbon sequestration service supply segment shows a first decrease and then an increase change,the 23 rd sub-basin has the most significant decline in supply,and the 18 th sub-basin has the largest increase in supply;the total supply of food production services is 15.5×108 kg/a rose to 21.9×108 kg/a in 2018,a total increase of 41.29%.The food production service supply segment showed a first decrease and then an increase.Only the supply in the 24 th sub-basin decreased,and the rest increased and the 5th sub-basin.The watershed is the area with the largest increase in the whole area;the supply of soil conservation services is 9.47×1011 t/a.Change from 9.48×1011 t/a in 2018,the total supply of soil conservation services has increased by 0.11%,and the amount of soil conservation appears within the time period In the trend of first decrease and then increase,the 1st and 23 rd sub-basins are respectively the areas where the supply of soil conservation services increased the maximum and the decrease in the supply was the maximum.（2）The demand for ecosystem services changes in time and space.Spatial changes: From 2000 to 2018,the spatial pattern of the service requirements of the four ecosystems in the Yi River Watershed was basically stable.The demand for water production,carbon sequestration,and food production was downstream> midstream> upstream,while the areas with high demand for soil conservation services were mainly located Areas with large terrain undulations or low vegetation coverage.Time-series changes in quantity: the total demand for water production services increased from 4.32×108 m3/a in 2000 to 5.77×108 m3/a in 2018,an increase of 33.56%,showing a trend of first decrease and then increase within the sub-section 3rd.The watershed is the area with the largest increase in the demand for water production services,and the area with the least increase in the 18 th sub-basin;the total demand for carbon sequestration services has continued to rise from 7.12×105 t·C/a in 2000 to 2.42×106 t·C /a in 2018,the overall trend is increasing,the total demand has increased by 239.89%,the largest increase in the demand for carbon sequestration services is in the 3rd sub-basin,and the smallest increase is in the No.18 sub-basin;the demand for food production services increased from 9.40×108 kg /a gradually increased to 11.60 ×108 kg/a,and the demand increased by 23.40%,showing an upward trend.The largest increase in demand for food production services was the 3rd sub-basin and the smallest increase was the 18 th sub-basin;soil conservation services in 2000 The total demand was 5.33×109 t/a.From 5.37×109 t/a in 2018,the water demand increased by 0.75%.The demand first increased and then decreased.The overall level increased slowly.The largest change in the demand for soil conservation services was On the 23 rd,the sub-watershed with the largest reduction is 1st.（3）The temporal and spatial evolution of the supply-demand relationship of ecosystem services.The supply-demand ratio of water production services remains high in the southwest and low in the northeast in the spatial pattern.Most areas in the middle and lower reaches are in short supply.There are 13 sub-basins with mismatched supply and demand.The water supply in the basin can meet the water demand of the region,but the supply and demand of water production services The average value of the ratio is gradually decreasing,and the regional differentiation is serious,and the supply distribution is severely uncoordinated,causing the deficit to gradually increase;the supply and demand matching space of carbon sequestration services is higher in the southwest and lower in the northeast,and the supply is much greater than the demand.The supply-demand ratios of each sub-basin are all positive.The supply-demand ratio of the overall carbon sequestration service within the segment increased first and then decreased;the spatial pattern of the supply-demand ratio of food production services was lower than that of the northeast during the study period,the supply in the middle and lower reaches exceeded the demand,the upstream area was insufficiently supplied,and the supply and demand did not match the sub-basin There is only one.The supply in the study area can meet the demand.The supply-demand ratio of food production services is on the rise.Within the segment,it first decreases and then increases.The demand ratio fluctuates at a value of 0,which is close to a balanced state.The supply-demand ratio of soil conservation services is relatively high overall The upper reaches of the spatial distribution is higher than that of the middle and lower reaches.The supply-demand ratio of each sub-basin is positive,and the average supply-demand ratio has a slow upward trend;the comprehensive supply-demand ratio of ecosystem services in the Yi River Watershed is higher in the southwest and lower in the northeast in terms of the overall supply.More than demand,the overall supply-demand ratio has a downward trend.（4）Risk analysis and spatial control of the supply and demand of ecosystem services.From 2000 to 2018,the supply and demand of water production services faced more serious risks.The risk areas were concentrated in the middle and lower reaches,and the risk of water production services increased slightly.The spatial distribution of the supply and demand risks of food production services is opposite to that of water production services,and the transition from safety levels to fragile levels requires serious attention.The overall supply and demand risk of carbon sequestration services and soil and water conservation services in the basin is relatively small and gradually improved.At the sub-basin scale,half of the sub-basin water production service supply and demand risks from 2000 to 2018 are at a high risk level,and there is a serious mismatch between the water production service supply and demand within the watershed.Among the other three services in the sub-basin,the low-risk level is the main one,and the risk is relatively small.Based on the assessment results of the supply and demand risks of ecosystem services,the Yihe River Basin is divided into 8 types of supply and demand space management zones,and 3 types of ecosystem service supply and demand risk optimization zones are divided according to the characteristics of different management zones,Instant water service key replenishment area,food supply improvement area and core key protection area. |
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