| With extreme climate change,as well as human interventions such as urban expansion resulting from population growth,urbanization and industrialization,surface vegetation destruction,soil degradation and soil erosion have been exacerbated,leading to significant losses in agricultural production and weakening the capacity of soil to store and recycle carbon,nutrients and water,which has been seen as a serious problem for the ecological environment of Wei River Catchment.Considering the seriousness of ecological environment problems,it is a realistic and effective way to slow down and improve the ecological environment of the catchment to carry out the ecological restoration project on a large scale led by the government.Therefore,how to integrate socio-economic and natural disciplines at the present stage,under the background of climate change uncertainty,objectively recognize and evaluate the effect of ecological restoration projects represented by terraces and sloping land conversion program to improve soil and water loss in the Wei River Catchment? Taking into account the financial burden of local governments,such as meeting the needs of socio-economic development and balancing land use planning for ecological and non-ecological land,is the implementation of ecological restoration project effective? How to improve the path that affects the efficiency of ecological restoration project at the present stage,and realize the sustainable supply of ecological environment in the future? These practical problems are the focus and difficulties to be overcomed in further research.In Shaanxi Province,the ultimate goal of ecological restoration of Wei River Catchment is to prevent and control soil and water loss.In this paper,under the guidance of multidimensional theoretical systems such as externality theory,human-land relationship system theory and ecological related theories,realizing the superposition of catchment vector map layer and county region vector layer by means of remote sensing technology.The panel data covering natural,economic,social and policy implementation indicators of 44 counties flowed through by Wei River from 2000 to 2015 are constructed,and the relevant data of social and natural disciplines are integrated,from the perspective of the government.Taking the soil and water loss and vegetation cover change of Wei River Catchment as the research objects,the ecological restoration effect and ecological restoration efficiency of Wei River Catchment have been evaluated.Firstly,the time series analysis of ecological restoration project,multi-year runoff,sediment concentration and sediment transport of important hydrological stations,terrace and sloping land conversion program were carried out by using statistical descriptive analysis.It provides accurate and objective data support for the proposition of practical problems and the construction of econometric model in this study.Based on software ArcGIS 10.2,the conversion pattern of land-use pattern,spatio-temporal changes of vegetation coverage index and vegetation primary productivity in the study area were analyzed.Secondly,the structural equation model is used to quantify and verify the path of ecological restoration projects,natural and socio-economic factors on regional land use / cover change,and select the key variables to lay the foundation for the establishment of the later model.Thirdly,the simultaneous equations model is used to solve the endogenous problem of soil and water loss mechanism,the internal correlation among runoff,sediment concentration and sediment transport is stripped at the same time.Then quantifying the elastic coefficient of ecological restoration programs,natural factors,socio-economic indicators on the soil and water environment.Finally,taking vegetation cover index,sediment concentration and sediment transport as output,taking rainfall,ecological restoration project area and funds as input,the efficiency of ecological restoration is calculated by data envelopment analysis(DEA)model.Using panel Tobit and geographical weighted regression(GWR)model to quantify factors that affect the efficiency of ecological restoration,select relaxation variable model to analyze the input redundancy and output shortage of each county,and take the prefecture-level city as the administrative unit to summarize.By objectively evaluating the effect and efficiency of ecological restoration measures,it is helpful to enrich and perfect the current evaluation system of ecological restoration projects dominated by socio-economic evaluation.Providing insight and analysis of the linkages between ecological restoration projects,ecosystem services and human economic and social development,thereby contributing to the design of future land use and ecological restoration policies in order to realize the sustainable and healthy development of watershed ecology and socio-economic system.Main conclusions have been shown that:(1)As an important driving force to promote the transformation of land use in the study area,the sloping land conversion program and terraces in 2000-2015 realized the absolute increase in the number of grassland and forest land(especially shrubs)in the study area.From 2000 to 2015,the significant changes of forest and grassland were concentrated in the slope of 15 °-25 °,and the largest increase of forest land was in the area of slope greater than 25 °.The variation trend of normalized vegetation index(NDVI)and net primary productivity(NPP)of vegetation in the study area showed that the quantity and quality of vegetation cover showed an improvement trend in the past 16 years,especially in the counties through which Beiluo River and Jing River flowed.The restoration of vegetation is better than that of the counties through which the main stream of Wei River flows,and the development trend of vegetation cover and productivity in the north bank of Wei River Catchment is better than that in the south bank.There is a certain spatial correlation between the change trend of NDVI and NPP,that is,the higher the coverage and growth of green vegetation,the stronger its ability to play an ecological effect.Ecological restoration project is the key driving force for the significant change of water and sediment environment in each county,which is mainly manifested in the fact that when the inter-annual fluctuation of runoff is small,the sediment transport and sediment concentration show a significant downward trend.(2)Considering the sloping land conversion program,the effect of the first stage of this project is slightly better than that of the second stage of the project.At the same time,the ecological restoration project is regarded as an economic means,the direct driving effect on the latent variables of socioeconomic factors is significant,which to a certain extent reflects that the implementation of ecological restoration projects is helpful to liberate the surplus labor force dominated by agricultural production from the land.The results showed that without the intervention of human factors,the changes of runoff and sediment concentration showed a significant positive effect on sediment transport,and the sediment transport showed a positive correlation with sediment concentration.For every 1% increase in the area of the sloping land conversion program,the sediment concentration per cubic meter will be reduced by 1.894 kg.The negative effect of terrace on sediment transport is more prominent,which shows that when the proportion of terrace area increases by 1%,the sediment transport can be reduced by 31.2 million tons under the superposition of the decrease of sediment concentration.In the case of considering human interventions,in the runoff equation,the order of marginal contribution of different influencing factors is terrace > slope > precipitation;in the sediment concentration equation,the order is soil type > ploughing index > sediment transport > the sloping land conversion program > the proportion of output value of industrial and mining;in the equation of sediment transport,the order is terrace > runoff > sediment concentration.(3)Assuming that the ecological benefits of forest and grass need to be lagged by 3-5 years,from 2000 to 2010,the overall average ecological restoration efficiency of the study area increased from 0.695 to 0.784,which showed the phenomenon of "club convergence" converging to the lower and higher classes.And the transfer trend of ecological restoration efficiency to a higher class is significantly greater than that to a lower class.The spatial distribution of ecological restoration efficiency in each county has certain clustering characteristics and has a positive correlation.The hot area of ecological restoration efficiency is mainly concentrated in the upstream of the study area,and the cold point area is concentrated in the county where the two tributaries of Jing River and Beiluo River converge into the main stream of Wei River.The order of the contribution of each influencing factor to ecological restoration efficiency is the proportion of non-agricultural employment > per capita grain output > per capita GDP > population density.The contribution of each factor to ecological restoration efficiency varies from different years.The order of contribution in 2000 was per capita grain output > the proportion of non-agricultural employment > per capita GDP > population density,in 2005 the order was non-agricultural employment > per capita grain output > population density > per capita GDP,in 2010 the order was the proportion of agricultural employment > per capita grain output > per capita GDP > population density.The proportion of non-agricultural employees is selected as the key factor to characterize economic and social development,and incorporated into the efficiency measurement model to recalculate the efficiency of ecological restoration.The new ecological restoration efficiency measurement value increased from 0.788 in 2000 to 0.808 in 2010.The overall trend is better than the original efficiency measurement value,the degree of inefficient use of funds and land has reduced,the ability to control the amount of sediment and sediment has increased. |
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