| The loess hilly region is an ecologically fragile region.With the implementation of Grain for Green project the ecological system has been restored and improved,and the social and economic system has been also developed.Evaluating the benefit of such project to study the coupling of Grain for Green and agricultural eco-economic system has been arising scientists attention in restoration ecology research.This paper,taking Ansai County in the ecologically fragile loess hilly region as an example,studies the coupling effect,coupling situation,coupling direction and intensity between Grain for Green and Agro-eco-economic system based on field survey and modelling,and explores the interaction and synergistic relationship between Grain for Green and Agro-eco-economic system.Further sustainable developments are suggested to provide scientific basis of the region.The main results are as follows:(1)The coupling between Grain for Green and agricultural eco-economic system is demonstrated.Based on the perspectives of ecological theory,eco-economical theory and sociology theory,this paper analyzed the theoretical basis of the coupling between Grain for Green and agricultural eco-economic and social system.From the idea of resilience research framework,the theoretical framework of coupling between Grain for Green and agricultural eco-economic system in process of the project was established.Taking the typical Zhifanggou watershed as an example,through the demonstration of the evolution process of the relationship between the conversion of farmland and the Agro-eco-economic system during 1938-2015,the interaction process between Agro-eco-economic system and Grain for Green was analyzed.It could be fund there were there phase in the interaction process including: the negative synergy phase(1938-1972),coupling-negative coupling-coupling phase(1973-1998),coupling sustainable development stage(1999-2015).It showed that there exited a coupling between the Grain for Green and the agricultural eco-economic system in actual development.The VAR model was used to study the relationship between returning farmland and Agro-eco-economic system in Ansai County,which further clarified the synergistic and reciprocal relationship between returning farmland and Agro-eco-economic system.This paper demonstrates the coupling between the Grain for Green and agricultural eco-economic system from the perspectives of theory,practical development process of the case area and model operation.(2)The coupling effect of the Grain for Green and agricultural eco-economic system was clarified.The effect implementation of agricultural eco-economic system under the Grain for Green action was analyzed by using spatial techniques such as RS and GIS and NDVI.The result showed that the soil erosion intensity of the converted farmland decreased significantly from 2000 to 2013 in Ansai County.The proportion of soil erosion area(except slight erosion)decreased from 95.31% to 38.19%,declining by 57.12%.It is pointed out that the implementation of the Grain for Green acted a key fact to reduce the soil erosion intensity in the study area,and the regional output value with a small comprehensive index of soil erosion is higher.The implementation of the Grain for Green has improved the structure of land use,agriculture,forestry and animal husbandry industry as well as the pattern of labor force in the region.On this basis,the vector autoregressive model(VAR)is used to calculate the coupling effect between the Grain for Green and agricultural eco-economic system.The results showed that the highest contribution rate of the Grain for Green to agricultural economic system is of 20.28%,and the highest contribution rate to agricultural social system is of 26.77%.The impact of agricultural ecosystem on the Grain for Green is stable at around 6%-7% in the long run,and the impact of agricultural economic system on the Grain for Green is the most obvious,with the highest contribution rate reaching 55.3%,which is consistent with the real situation.(3)The process of synergistic state evolution of farmland conversion and agricultural eco-economic system may be divided into four stages.By using the statistical yearbook data of Ansai County from 1995 to 2014 and the questionnaire data of relevant personnel,the change trend of comprehensive index of the Grain for Green system and agricultural eco-economic system in Ansai County from 1995 to 2014 was systematically analyzed.The results of comprehensive index showed that: the Grain for Green and the agricultural eco-economic system in Ansai County had an upward trend on the period from 1995 to 2014,and the change trend of the two systems was basically the same.The comprehensive index of returning farmland in 2014 increased nearly twice as much as that in 1995.After peaking in 2012,the agricultural eco-economic system declined slightly,and overall,it increased by 56.8% in 2014 compared with 1995.Based on the comprehensive index analysis,the coupling degree model was established.The synergic could be divided into four quadrants: Ⅰ.Cooperative Promotion and Development Stage II.Contrary stage III.Disorder imbalance stage disorder.IV.Inhibiting the development stage.Among them,the stage III is supposed to be a theoretical results and will not appear in actual policy constraints;and the stage II and IV may be appeared in a short-term.And from 1995 to 2014,Ansai County has passed through the contrary stage and the cooperative promotion and development stage.At present,the Ansai County at a declining period in stage Ⅰ.(4)The direction and intensity of coupling relationship between Grain for Green and agricultural eco-economic system were determined.By using the structural equation model and the analysising of 494 households data in Ansai County in 2015,the synergistic effect and synergistic intensity between Grain for Green and Agro-eco-economic system were clarified.The results showed that the agricultural eco-economic system is key factor for successful coupling between Grain for Green and agricultural system development.These coupling benefits are derived from through linkages between the program and various chains in the agricultural system.Under the effect of Grain for Green,the direct impact coefficient of ecosystem and synergistic effect is of 0.87,which indicates that the optimization of agricultural ecosystem in Ansai County at this stage provides the basic material and energy support for the coordinated development of returning farmland and agricultural eco-economic system.The direct impact coefficient of the economic system is of-0.76,which means that the agricultural development in the region at this stage has not been able to transform agricultural resources into agricultural economic advantages,resulting in the relatively backward development of the regional agricultural economic system.Eventually,the coordinated development between farmland conversion and Agro-eco-economic system has not been eatablished.(5)The policy on optimizing the coordinated development of Grain for Green and agricultural eco-economic system were suggested.Combining with the dual objectives of ecological restoration in short-term and the sustainable development of ecological economic and social in long-term,the prerequisite is to promote the emergence of potential ecological functions in the area of Grain for Green project.On the basis of continuously improving the quality and structure of woodland,the structure of agricultural industry chain network with forest and grass resources as the core is constructed,so as to promote the optimization and coordination of Grain for Green and agricultural eco-economic system. |
