Study On Permanent Prime Farmland Demarcation Based On "Double Evaluation" And SA System ——A Case Study Of Fangshan Country

Food security is an important foundation for national security and has a bearing on China’s prosperity and people’s livelihood.Grain production is based on cultivated land,and the guarantee of food security depends on the amount of cultivated land,especially the permanent basic farmland.Demarcation of permanent basic farmland is the first in the system of "demarcation,construction,management and protection",and the scientific demarcation of the results is the prerequisite to improve the protection benefits of permanent basic farmland.At present,It is frequent that occupying of permanent basic farmland.On the one hand,That is because that It did not consider reasonable the coordination of food security and socio-economic development,which lead to not stable enough of permanent basic farmland.On the other hand,the construction of ecological civilization is the need to coordinate the current and long-term development,and its priority is much higher than agricultural production and urban construction.Under the background of scarce land resources,this premise brings severe challenges to the mountainous and hilly areas with heavy ecological protection tasks.Based on the existing research and related concepts,this study is adjusting the provincial and municipal research method of resource and environment carrying capacity and Land Space Development Suitability Evaluation（hereinafter referred to as "double evaluation"）proposed under the background of spatial planning at the county level,promoting the optimization of county-level permanent basic farmland delimitation methods and improving the scientificity of permanent basic farmland delimitation results.Specifically,combined with the existing research,this study,based on the "double evaluation",takes the agricultural production suitable area determined by the suitability evaluation of land and space development as the carrying capacity of cultivated land under the constraints of land resources,calculates the carrying capacity of cultivated land under the constraints of water resources according to the guidelines for the evaluation of resources and environment carrying capacity and the suitability of land and space development（hereinafter referred to as the "guidelines"）,and determines the upper limit of the number of permanent basic farmland in the study area.Then,the results of land space development suitability evaluation are applied to the delimitation process of permanent basic farmland,which is carried out from the following three aspects: First,under the concept of ecological civilization construction,based on the short board principle,judge the extremely important areas of ecological protection by integrating the importance of ecological service function and ecological sensitivity,and ensure the independence of the two red lines at the beginning of the delimitation of permanent basic farmland;Second,"high quality" is the basic premise for the selection of permanent basic farmland.According to the characteristics of the study area,a land resources evaluation index system with differentiation and significant and strong restrictive effect on the suitability of agricultural production in the study area is constructed,which reflects the restrictive factors and comprehensive restrictive degree of each evaluation unit based on the short board principle.Third,considering the coordination between economic and social development and food security,based on the purpose of urban construction,carry out the evaluation on the same scale and method,judge the conflict of urban construction on agricultural production,and assist the decision-making of selecting cultivated land into permanent basic farmland.Finally,the study believes that natural factors substantially determine whether cultivated land can be used for farming or urban construction,and under the concept of harmonious treatment between man and nature,the role of economic and social factors on land spatial use is also very significant.Therefore,based on the perspective of cultivated land itself,the site evaluation（SA）reflecting the impact of socio-economic conditions on farming stability is completed,It provides another reference for the selection decision of permanent basic farmland in the conflict area between agricultural production and urban construction.The results of permanent basic farmland delineation show that there are 5693 permanent basic farmland delineation spots in Fangshan County,with a total of 17243.38Hm2,accounting for 78.24% of the cultivated land in Fangshan County,and the average cultivated land quality is 12.53.Both in quantity and quality,it is slightly higher than the results of current permanent basic farmland delineation,and the coincidence degree with the results of current permanent basic farmland delineation is 82.46%,which proves the rationality of the evaluation method in this study to a certain extent.In terms of spatial layout,affected by the fact that Fangshan County is located in mountainous and hilly areas and the overall slope is large,the newly designated permanent basic farmland is still relatively concentrated near the Beichuan River and its tributaries along the central axis.Finally,according to the discussed in permanent basic farmland demarcated optimization ideas and its application in Fangshan county,this study,combined with "long teeth hard measures",puts forward different cultivated land zones undertake different missions（quality/quantity improvement）,establish reserve areas,ensure the supplementary planning needs of permanent basic farmland,and conduct dynamic monitoring from three perspectives,such as the responsibilities of each cultivated land in the whole permanent basic farmland,the supplementary planning of permanent basic farmland and the sustainable protection of permanent basic farmland to achieve permanent basic farmland management and protection.