| Ecosystem service was defined that the ecosystems provide tangible products and intangible services for human beings.Ecosystem service flow is the spatial transmission path of ecosystem services from source area to beneficiaries.Ecosystem service supply and demand is most separated in temporal and spatial.Ecosystem service flow establishes a spatial connection between the place of service supplied and the place of service demanded.Moreover,it defines the transmission path of ecosystem service flow.The ecosystem service flow makes it possible for people to satisfy the needs of a certain commodity and service.Elaborating on the balance of supply and demand for ecosystem services.Moreover,on the basis of which the transmission path of service flows and the law of flow variation were clearly defined.And it was beneficial for assessing ecosystem service value accurately.Taking Yuncheng section of Fenhe River Basin and the upper reaches of Sushui River Basin as the study area.Including Wanrong County,Hejin City,Jishan County,Xinjiang county,Wenxi county and Jiangxian county in the northern of Yuncheng.Based on Geographic Information System(GIS)and Remote Sensing(RS),using the RUSLE model and SPANs model,and taking remote sensing data,meteorological data,land use data,soil data,elevation data,vegetation data and so on as the base data,we quantified and mapped the supply,demand and the flow path of soil erosion conservation service and flood regulation service in 2000,2005,2010 and 2015,respectively.And then analysis the variations and the factors of the service flow.The purpose of the study is to clarify the surplus of supply and demand space,as well as the transmission path and flow rate variation of soil erosion conservation services and flood rugulation services.The goal of the study is to offer proofs for making scientific and reasonable policies of ecological compensation and management of watershed in Shanxi province.The following are the main conclusions of the study:(1)The supply area of soil erosion conservation service is forest and grass,which mainly located in the Gufeng Mountains.The quantity supplied of soil erosion conservation service of 2000,2005,2010 and 2015 were 3.15×10~6t/(km~2·a),3.38×10~6t/(km~2·a),3.41×10~6t/(km~2·a)and 9.87×10~5t/(km~2·a),respectively.The increasing trend from 2000 to 2010 showed that the function of the soil erosion conservation service has been improved.The sparse woodland and covered grassland were relativily large.We standardized the quantity provided by different types of vegetation in the study area and make the value varies from zero to one.Then the supply was divided into 0-4 levels and mapped by using the ArcGIS.From 2000 to 2015,the medium supply,the high supply and the higher supply were mainly distributed in Wanrong County and the north of Jishan County,Hejin County and Xinjing County in the study area.The low supply area was less distributed and lacated in Jishan County and Wanrong County.(2)The demand area chiefly contains the reservoir in the Yuncheng section of Fenhe River Basin,the farmland and rural residential areas in the middle and lower reaches of the alluvial plain.We quatified and standardized the demand of soil control ecosyetem service according to the quantity of the ecological restoration work and make the value varies from zero to one.Then the demand was divided into 0-4 levels and mapped by using the ArcGIS.From 2000 to 2015,the study area was dominated by low level demand.Nevertheless,the high level demand only appeared during the period from 2000 to 2010.Moreover,the high level demand area was mainly distributed in Wanrong County.However,the low level demand and the lower level demand appeared merely in 2015.Furthermore,the low level demand area is located in Hejin county,Wanrong county and Xinjiang county.The soil erosion was increasingly from 2000 to 2010,especially Wanrong ounty was seriously.But it was decreased from 2010 to 2015.(3)The service flow path is determined principally according to the topography and hydrographic net.The topography of the study area is high in north and south,low in the middle,and the relative height is obvious.The rivers mainly include Sanjiao River,Sanquan River,Huanghuayu River,and Mabiyu River,that flow direction was from the north and the south to the middlie and into the Fenhe River finally.In accordance with the amount of soil erosion conservation provided by the green vegetation(forest and grassland)in the sub watershed,the size of service flow is divided into five levels.From 2000 to 2015,the high level service flow appeared in Xinjiang County and Jishan County.Moreover,the higher level service flow appeared in Hejin city(2000 without higher service level flow).However,the medium level service flow chiefly appeared in Wanrong county(2005 without medium level service flow).The low level service flow mainly appeared in Hejin city and Jishan County.Further,the lower level service flow mainly appeared in the main river course of Fenhe River.It is mainly due to the lower vegetation coverage and near the main river course of Fenhe River and the highter sediment content entering the river.(4)The supply area of flood regulation service is forest,grass and reservoir,which mainly located in the upper reaches of the Sushui River and Shaqu River and so on.The quantity supplied of flood regulating service of 2010 in Wenxi County,2010 in Jiangxian County,2015 in Wenxi County and 2015 in Jiangxian County were 1.76×10~6m~3,3.28×10~6m~3,1.15×10~6m~3 and 3.61×10~5m~3,respectively.The high supply area was mainly distributed in Jiangxian County in 2010 and 2015.The quantity supplied of forest and grassland in 2010 and2015 in Wenxi County,2010 and 2015 in in Jiangxian County accounted for 99.43%,99.13%,99.99%and 99.45%,respectively.Therefore,the flood regulation capacity of vegetable was very important.(5)The demand area of flood regulation service comprises towns,residential sites and farmland on the alluvial plain of the middle and lower reaches of Sushui River and Shaqu River.The region can be classified into six grades in view of the terrain and sensitivity of damage caused by flood.The high demand area were mainly located in the towns of Wenxi County and Jiangxian County.The higher demand area were mainly in the area of rural residential sites.The lower demand area were mainly in the farmland of Jiangxian County and Wenxi County.There was no medium demand area and low demand area in study.(6)The flood regultion service flow path is determined principally according to the related data of the topography,hydrographic net and alluvial plains.The flood gully were extracted from the DEM data.The rivers are mainly contain the Sushui River and Shaqu River,which flow direction generally from southeast to southwest.According to the percentage of flood volume were reduced and the residual flood volume that enter in the sub watershed,the size of service flow is divided into five levels by the standardized processing.The low service flow was mainly at study area in 2010 and 2015.Among them,there were appeared high service flow and the higher service flow in Wenxi County in 2010 and 2015,respectively.Which were mainly distributed in Dongzhen town.The reason that the reservoirs distributed in the area was relatively large,about 59.664 million cubic meters.However,the storage capacity of the reservoir is 15.794 million cubic meters in Jiangxian County.So the reservoirs have a greater effect on the reduction of flood in Wenxi County.In addition,the high service flow and medium service flow appeared in Jiangxian County in 2015.The high service flow was mainly distributed in Weizhuang Town and the middle service flow was distributed in Anyu Town,Dajiao Town and Nanfan Town.It mainly because that the vegetation coverage is relatively low,about 35%.At the same time,the soil has a weaker ability to reduce flood in the study area. |
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