Ecosystem Services Evaluation Of Danjiangkou Reservoir Area And Upper Reaches Based On 3S Technology

The research on evaluation of ecosystem service value is one of the hotspots of current ecosystem sustainablility research,which attracts broad participation of a large number of researchers from different disciplines,especially the scholars of ecology and economy.It is a future study direction using 3S technology to quantify the ecosystem services.The Middle Route of South-to-North Water Transfer Project is a large-scale trans-basin water transfer project,and the ecological environment of Danjiangkou reservoir area and upper reaches is the key factor that the Middle Route of South-to-North Water Transfer Project brings its social, economic and ecological benefits.According to the appraisal theory and method of the ecosystem service,the paper takes the Danjiangkou reservoir area and the upstream ecosystem as the objects of the study,uses remote sensing,geographical information system and the mathematical statistic method by adopting the multi-source remote sensing images,geosciences data and the field-work GPS localization sampling data.This paper carries out effective analysis and localization,rational and dynamic evaluation on each term of services in the study area.The conclusions are as follow:Evaluation of soil conservation service value:(1) As far as the total amount of soil conservation in the study area is concerned,the forestland is the highest,followed by grassland.What's more,soil conservation amount in water and other types of soil are very low,which is consistent with the vegetation coverage and the distribution of net primary productivity and it indicates that the vegetation in the high vegetation coverage type distribution area can prevent and control the soil erosion effectively.(2) Among the soil conservation value of the ecosystem in the study area,the soil conservation value of forestland and shrub land ecosystems accounted for nearly 60 percent, grassland ecosystem accounted for nearly 30 percent,while forest-shrub-grass accounted for nearly 90 percent of the total value of services.So,forest,shrub,grass play a decisive role in the ecosystem services of soil conservation.Evaluation of temperature adjustment service:(1) The average temperature of LST monthly products is basically consistent with the mean air temperature changing tendency of each month.The most extreme maximum and average maximum temperature both occurred in July while the extreme minimum and average temperature both occurred in January.(2) LST and NDVI changes have similar changing tendency in a year,between which there is an obvious linear relationship.The vegetation coverage and the altitude are major influencing factors of LST,and there exists an obvious negative correlation linear relationship between LST and the above two factors.(3) Forestland,grassland and water area exert a significant regulatory effect on LST.The heat island effect of the town is very prominent and the value concerning the temperature adjustment of woodland,grassland and water area is estimated by using the energy substitution method in the study area in 2008.Evaluation of the value of maintaining soil moisture service:(1) There exists significant difference of the surface soil moisture in each month of the study area,and significant change in the surface soil moisture takes place with the seasonal change.In the view of the spatial distribution,the soil moisture in mountain area is significantly higher than that in the plain and basin area,consistent with the spatial difference of the topography.In the area where lakes and rivers lies,the soil moisture reduced gradually and expressed as from sub-humid to arid with the dropping moisture of lakes and rivers extending to the all directions.In general,the change in the dry soil moisture situation is more complex in the area due to the complex impact of micro-topography.(2) In the view of soil moisture maintenance value of different land use or cover types,the order from high to low is as followl: forest,shrub land,grassland,farmland and other types,in accordance with per unit area value of soil moisture retention in the study area.In the view of the total value of soil moisture malntainance, forestland,shrub land and grassland accounted for more than 80%in the Danjiangkou reservoir area and upper reaches,which is the key to ensure water conservation and the quality and quantity of water.Comprehensive evaluation of service value based on net primary productivity:(1) From the view of the inter-annual change,the total NPP of the study area shows irregular change from 2000 to 2006 because the change is affected by the temperature,precipitation and other natural and human factors apart from its land use and cover change.(2) In the view of the spatial distribution,NPP shows changing trend of first increase and then decrease,which is relevant to hydrothermal conditions change and state of cultivation brought by topography of the study area.(3) The service value concerning net primary productivity includes the aspects of the organic matter production of the ecosystem,the maintenance of atmospheric carbon dioxide and oxygen in the dynamic balance, nutrient cycling and purification of the role of environmental pollution.And in the view of the above service value,the service value of forest land,shrub land and grass land accounted for more than 75 percent of the total,which plays a decisive role for the maintenance of the entire ecosystem balance and stability.The combination of 3S intergrated technology and service value evaluation of ecosystem provides as a preferable technique-support tool in the aspects of quantitative and timely acquisition of the location information,as well as the more accurate evaluation of the ecosystem service.And this new method will solve the problem the conventional method can not do in the aspect of the lack of dynamic and spatial heterogeneity existed in the current ecosystem service.The service value of the Danjiangkou reservoir area and upper reaches is demonstrated in the form of currency in the end, which will improve cognition of the people in the study area.Meanwhile,it can provide as a reference for ecological compensation to find reasonable fund sources for the conservation of the natural resources and ecological environment.In additon,sensitive spatial distribution features of the ecosystem in the area can be found to provide further scientific basis for the division of ecological function region and the plan of ecological construction.As a result,the rational resource distribution both in the temporal and spatial scale will guarantee the fairness between the contemporary people and intergeneration both in intra-region and inter-region,realizing the sustainable development in the region finally.