The Mechanism Of Action Among Ecosystem Services And Their Coordinated Development In Retired Farmland Area

With the implementation of the Grain to Green Program(GTGP),the ecological restoration has achieved remarkable results in retired farmland area.As a bridge between natural ecosystems and human well-being,ecosystem services undergo a series of changes in the process of returning farmland to forests.Understanding the changes and mechanisms of action in ecosystem services during the process of returning farmland to forests and their interaction mechanisms,and revealing the relationship between human well-being and ecosystem services has become one of the key needs of current academic research and ecological management.Taking Ansai District,one of the earliest counties in China to implement the GTGP,as the study area,this study analyzes the temporal and spatial evolution of land use/cover in retired farmland area.Based on the In VEST model,the spatiotemporal changes,the interaction relationship,the scale effect and the differentiation mechanism of ecosystem services were evaluated.Finally,from the perspective of the consumers of ecosystem services—farmers,the pathways of ecosystem services on human well-being is revealed,and the changes in human well-being under different scenarios are simulated,and suggestions and countermeasures for regional sustainable development are put forward.The main results and conclusions are as follows:(1)The land use structure and spatial allocation in the conversion area have been optimized in the process of returning farmland to forest.During the study period,the cultivated land area decreased sharply and the forest and grassland increased;affected by the hilly and gully terrain,the cultivated land and grassland present a staggered distribution pattern in space.In the early stage of returning farmland,the land use is mainly from cultivated land to forest land;In the later stage,the conversion from cultivated land to grassland occupied a dominant position,the manual intervention began to decrease,and the returned farmland areas began to enter the stage of ecological restoration dominated by natural restoration.(2)The GTGP has achieved remarkable ecological restoration results,and ecosystem services such as carbon storage,soil conservation and habitat quality have been effectively improved.Affected by land use/cover,topography,climate and human activities,ecosystem services are spatially heterogeneous.This heterogeneity presents corresponding scale characteristics on different spatial scales:ecosystem services have spatial positive correlation on grid scale,and the spatial correlation decreases with the increase of grid spatial scale;At the township and watershed scales,spatial heterogeneity shows different characteristics with the types of ecosystem services.(3)In retired farmland area,the synergistic relationship between ecosystem services is dominant.Among them,the synergistic relationship between regulatory service and support service is the strongest,while the trade-off relationship occurs between the cultural service and other services.From the time series point of view,the relationship between regulatory service and support service is relatively stable,and the degree of synergy increases after the returning farmland to forest,which further indicates that the GTGP improves the supporting function of the ecosystem.It is in line with the ecological management goal of "ecosystem services strengthening coordination and reducing conflict" of returning farmland to forests.(4)The relationship between ecosystem services is dependent on the spatial scale.On different spatial scales,the direction and significance of the interaction between ecosystem services are different.With the increase of scale,natural and socio-economic factors such as different land use types,topography and slope have been reorganized and newly configured in the research unit,which has affected the functional relationship of ecosystem services to a certain extent.Affected by the change of spatial sample size,the significance of the relationship between ecosystem services decreases with the increase of spatial scale.The spatial scale dependence of ecosystem services further shows that when management policies and measures are adjusted to their respective appropriate spatial scales,the trade-off relationship between some supply services,regulation services and support services can be reduced,and the synergy between various regulation services can be enhanced.(5)The trade-off and synergy of ecosystem services is the result of the joint action of natural factors and social factors.Due to less disturbance from human activities,in retired farmland area,the natural factors play a decisive role in ecosystem services,and the key factors affecting a certain ecosystem service play an important role in the relationship.The results of factor interaction show that the combined effect of any two factors is greater than the influence of a single factor on the relationship between ecosystem services.Among them,the interaction between natural factors and social factors is significantly higher than the combined effect of two social factors.In the interaction between different factors,there are two types of interaction:nonlinear enhancement and two-factor enhancement.Among them,the interaction between the land use degree factor and the terrain factor(slope and elevation)shows a two-factor enhancement effect,and further shown that the interaction between land use and topography is the main focus of ecosystem service management in retired farmland area.Influenced by natural factors,the synergistic relationship between ecosystem services was significant in areas with slopes>25°,showing the same direction of development.At 0° to 15°,the interaction relationship between different ecosystem services is relatively stable.However,since the 15° to 25° slope land is not within the scope of GTGP and is obviously disturbed by human activities,the synergy between different ecosystem services is reduced and the trade-off relationship is strengthened.It is an area with strong conflict between ecosystem services.(6)The pathways of ecosystem services on human well-being shows that supply service,support service and cultural service have a direct impact on the economic income,social well-being and health security of human well-being respectively,while regulatory service have an impact on human well-being by affecting the livelihood of farmers.The implementation of the GTGP has changed the production and life style of farmers.The economic development of the retired farmland area has low demand for various means of production and ecological resources in the system,and there is a negative effect between the supply of services and economic income.On the other hand,farmers who are in the stage of "life development needs" pursue economic development,so they pay less attention to cultural services such as tourism and recreation.Cultural services have a negative effect on livelihood and economic income.(7)The enhancement of supply service and cultural service is of great significance for the realization of ecosystem conservation and human well-being in parallel.When support service and regulatory service are diminished,ecosystem services and human well-being decline significantly.Therefore,in order to achieve the coordinated development of ecosystem services and human well-being,it is of great significance to encourage farmers who return farmland to maintain the results of returning farmland to forests.