| As a means of regulation and control in macro view,policies regulate and change human activities,affect land use and ultimately lead to changes in regional ecological environment.As a typical inland river basin in arid area of Northwest China,Shule River has been resettled and exploited many times under the impetus of national policy,which has caused tremendous changes in the ecological environment of the river basin,resulting in a series of environmental problems.Therefore,this study combs the policies implemented in the middle and lower reaches of the Shule River Basin since 1987,and takes the“Comprehensive Development Project of Agricultural Irrigation and Resettlement in the Shule River Basin”as an example,establishes a quantitative policy index system,calculates the comprehensive policy intensity with the weighted summation model,analyses the characteristics of the change of policy intensity,and then based on land use/cover data and socio-economic statistics in 1987,1996,2007and 2015,the ecosystem service value of the study area was estimated,and the temporal and spatial characteristics of ecosystem service value change in the middle and lower reaches of Shule River basin from 1987 to 2015 were analyzed.Finally,the correlation and lag between the two are analyzed by Pearson.We discussed the response of ecosystem service value in the process of immigration policy implementation,studied the relationship between policy test intensity and ecosystem service value in the middle and lower reaches of Shule River basin.Aim to provide theoretical basis for the protection of ecological environment and the rational development of land resources and promote the coordinated and sustainable development of regional socio-economic and ecological environment.The main conclusions of this study are as follows:(1)The policy comprehensive intensity index of“Integrated Development of Agricultural Irrigation and Immigrant Settlement in Shule River Basin(1996–2006)”increased with the increase of the investment and development area.In the base year of policy implementation in 1996,there were fewer investments.Limited new cultivated land area and afforestation area,and the policy comprehensive intensity was only0.0162.The policy investment amount increased rapidly from 1999 to 2002,and the policy intensity comprehensive index was clearly increase.(2)From 1987 to 2015,the structure of land use haven't change significantly in the middle and lower reaches of Shule River.The main types of land use were grassland,arable land and unused land.Oasis which composed of grassland,woodland,water wetland,arable land and construction land showed an overall increasing trend,with a total growth of 549.15 km~2 in 29 years.The area of cultivated land in the study area increased the most,the speed of change of construction land was the fastest and the dynamic degree was 5.3724%.From 1996 to 2007,the types of land use as well as the speed of land change and the speed of land transfer were more severe than the other two periods,and this period was the implementation stage of the Comprehensive Development Project of Agricultural Irrigation and Immigration Resettlement in Shule River Basin.(3)From 1996 to 2007,it was the main period for the expansion of cultivated land and construction land in the study area.The extended spatial change coincides with the immigration settlement and time in Shule river basin,indicating that immigration policy is the main driving factor affecting regional land use change.(4)From 1987 to 2015,the total value of ecosystem services in the study area showed an upward trend,but the overall increase was relatively small and the growth trend was slow,with a total increase of 6.21×10~8 yuan in 28 years.The ecosystem service value of all kinds of ecosystems in the study area is in a state of fluctuation,in which the service value of cultivated land and woodland has increased significantly.The value of each ecosystem function in the middle and lower reaches of Shule River shows a slight fluctuation,and the value of each ecosystem service contribution remains unchanged in the year.(5)The value of ecosystem services in the study area is significantly correlated with the comprehensive policy intensity and its indicators at the level of 0.01.Forestry investment,resettlement investment,new irrigation area,afforestation area and immigrant population are the main factors causing the change of ecosystem services in the policy indicators.The service value of grassland,forest land,water area,arable land and desert ecosystem is significantly correlated with the comprehensive intensity of policy and various policy indicators.Immigrant population,afforestation area and new irrigation area are the main factors affecting the change of ecosystem services.Supply services,regulatory services and support services are positively correlated with the overall strength of policy,while the value of cultural services is negatively correlated.(6)The lag period of policy implementation on the change of ecosystem service value is three years,among which the second and third years have a greater impact on the change.From the cumulative perspective,the impact year is mainly divided into four years.The lag period of policy impact on ecosystem service value of grassland,woodland and cultivated land is three years,while that of water and desert ecosystems is four years.From the perspective of policy accumulation,the lag period is longer.The lag period of the policy influence of the change of ecosystem service function value is three years,which is more than one year from the perspective of policy accumulation.(7)Policy factors impact to the ecosystem service value impacts significantly and plays an important role in the chage of environment and ecological system.This effect not only can timely and directly reflect the ecological environment change,but also has lagging and cumulative effect.To a certain extent,policy factors can be considered the main reason leading to ecological environment change. |
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