Comprehensive Evaluation And Classification Of Permanent Basic Farmland In Metropolitan Area From The Perspective Of Farmland Multi-function

Permanent basic farmland(referred to as "Yongnong")protection system is the most stringent farmland protection system at present.However,there is still a large amount of high-quality farmland occupied,which indicates the "rigidity" and"permanency" of Yongnong protection has not been executed efficiently.With the upgrading of people’s demand structure,the value of multi-functional and compound utilization of farmland in metropolitan areas have became increasingly prominent.In the implementation of the rural revitalization strategy,the conflict between "rigidity"of Yongnong protection and infrastructure construction and agricultural compound utilization has intensified.And the flexibilty of Yongnong protection is limited.Therefore,in order to implement permanent protection of high-quality farmland effectively and achieve multi-functional composite utilization of farmland,it is of great importance to develop a systematical and technical method of Yongnong comprehensive evaluation and grading delimitation from the multi-function of farmland perspective.The research focused on the requirement of Yongnong protection bottom line and the multi-functional demand of farmland in metropolitan area.Firstly,a comprehensive evaluation indicator system was constructed from three aspects including farmland production,ecology and landscape culture.Secondly,combined with traditional land use data and Point of Interest(POI)geospatial data,the multi-functional value of Yongnong was calculated comprehensively by means of GIS spatial analysis and model analysis.Thirdly,based on the principle of "high-quality farmland aggregation and demand-supply balance",we developed a grading delimitation rule using the diversified characteristics of Yongnong.They were divided into Yongnong Protection Baseline Zone,Yongnong Protection Key Zone and Yongnong Protection General Zone.Then,taking the metropolis,Hangzhou city as the study area,an empirical study on the comprehensive evaluation and classification of Yongnong was conducted.The suggestions of differentiated and hierarchical management were further put forward The results were as follows:(1)The Yongnong in Hangzhou showed obvious spatial heterogeneity on farmland production,landscape ecological and cultural function:In terms of the farmland production function,the northeast plain area and the central valley plain area represented stronger compared with Southwest Hilly back area.In terms of the farmland ecological function,the western Tianmu Mountains and the southern Qianligang Mountains with the low hills and gentle slopes were relatively high,while the northeastern plain area was relatively low.In terms of the farmland landscape cultural function,the suburban plain area,the ancient villages and the surrounding areas of famous scenic spots were much higher.It was found that the magnitude of each function is closely related to natural conditions and location.It showed a strong trend in the northeast and weak in the southwest,and there was a certain synergistic relationship between the production function and the landscape cultural function.(2)The results of Yongnong classification and the suggestions of differential control were as follows:①Yongnong Protection Baseline Zone was the core of Yongnong Protection mainly for the continuous production and economic fields,landscape inheritance fields.It was a comprehensive representation of the multi-functional value attribute of farmland,which integrates agricultural production,rural pastoral features and farming cultural experience.The baseline areas were generally located in the water network plains in the northeast,the coastal plains and the central valley plains.Concerning the spatial control,the most stringent farmland protectionsystem and built-up land control system should be implemented,and permanent protection should be implemented from the planning source.Its spatial layout shall not be adj usted through planning at will,and no construction proj ect shall occupy or change its use.②Yongnong Protection Key Zone were mainly high-quality farmland with good contiguousness.They were widely distributed in all districts and counties with its overall trend from the plain area around the town to the semi-mountainous area.③Yongnong Protection General Zone were mainly the Yongnong blocks in scattered and fragmented form with relatively low multi-functional value.The blocks displayed as islocated islands and scattered in the hilly back area of the western hilly area.In terms of spatial control,a positive list for projects allowed to access should be formulated and special protection should be implemented in accordance with current Yongnong Protection requirements in Yongnong Protection Key Zone and Yongnong Protection General Zone.(3)Taking Hangzhou as an example,the multi-functional comprehensive evaluation and grading exploration of Yongnong has important practical significance in solving the contradiction between farmland protection and urban development,rigidity and elasticity of Yongnong protection.Also,it can provide valuable basis for the national spatial planning in Hangzhou.In addition,our research might be helpful for policy-makers and managers to make proper arrangements on the multi-functional compound utilization of farmland and bottom line management of farmland protection in metropolitan area.