Evaluation of spatial distribution of basic farmland conservation area in Yinchuan

Abstract: Basic farmland area determined by overall land use planning in China, is regarded as important measures to guarantee the grain quantity and food security. The quantity of basic farmland is strictly restrained by the government, but the quality relate to the location is not well supervised. Thus, with land reclamation planning and high-standard basic farmland project, it is of importance to evaluate the spacial allocation of basic farmland for raising the quality of basic farmland. We pick Yinchuan as study area, which is a rapid development city in the west of China. There are many contradictions between economic development and protection of farmland in recent years. Firstly, according to the requirement of basic farmland delineation, we construct a methodology consisting of suitability and coordination, which represents the impact of natural conditions and land-use system of basic farmland protection areas. Secondly, we choose various index based on the local situation. The suitability index contains slope, soil texture, river system distance, and degree of soil salinization. The coordination index contains the distance to the center town, polygon area, the proportion of arable land, and proportion of overlapping planning zone. The weight of each index is determined by the Delphi method with relevant reference information as well as provincial experienced experts. Besides, with the help of ArcGIS9.3, we use Comprehensive Fitness Evaluation Model and Experience Index Method to calculate and drawing the suitability classification map and land-use system coordination classification map. Lastly, we use GIS spatial analysis to superimpose two classification maps, and mutually exclusive matrix classification is used to integrate these two reciprocally independent indicators. The result shows that, the basic farmland is divided into five different types according to the classification matrix: I. Completely rational zone; II. Basic rational zone; III. Development reserve zone; IV. Reduction zone and V. Unreasonable zone. The rational region (I, II and III types) accounted for 90.76% of total basic farmland protection area in Yinchuan, which means that the current planning scheme is basically rational. Unreasonable regional area (IV and V types) accounted for 9.24%, which mainly distribute in the edge of basic farmland concentration area, with patchy distribution. These districts are influenced by two aspects of the suitability and coordination. It is suggested that delineating basic farmland area does not only mean selecting high quality arable land by technical, but also focusing on the influence of the coordination between the various factors of the land use system. This study provides a new way of evaluating basic farmland's spatial layout, points out the techniques and methods, and shows specific evaluation and decision-making process. The innovation of this paper is that: 1) Establishing evaluation index of system coordination; 2) Applying mutually exclusive categories to integrating natural conditions and system coordination; 3) By selecting Yinchuan city as study area, demonstrating the problems in basic farmland protection areas delineated in western regions of China.