多尺度行政区平衡视角下耕地空间布局优化

优化耕地空间布局对提升耕地生产能力、促进农业可持续发展具有重要意义。该研究以广东封开县为例,基于“现状耕地调出-可恢复地类调入”的微观调整逻辑,综合运用空间叠加、综合评价及蚁群优化算法,构建了耕地空间布局调整模型,以调入调出数量平衡为约束条件实现了不同行政区尺度下的耕地布局优化。结果表明：1）研究区共调出耕地1 689.89 hm²,占耕地总面积的7.62%,整体上呈现出“全局零散、局部聚集”的分布特征。2）研究区可恢复地类农业生产适宜性均值为67.04,具有开展作物种植的良好禀赋条件。3）不同行政区尺度平衡情景下,调入结果在研究区北部空间差异显著,与镇内平衡情景相比,县内平衡情景下,调入耕地的农业生产适宜性均值提高了2.08,综合生态系统服务均值下降了0.67。4）两种情景下,耕地的连片性、质量及稳定性均得到提升,因不受调入规模和行政单元空间范围限制,县内平衡情景下的提升效果更加明显,适当扩大可恢复地类筛选范围有利于提升整体耕地质量并降低重要生态用地筛选概率。该研究构建的耕地空间布局调整模型具有良好的适用性,可为制定农用地布局优化与整治提升方案提供参考依据。

Optimization of the spatial layout of farmland from the perspective ofmulti-scale administrative balance

The optimal spatial layout of farmland is of great significance in improving the production capacity. The agricultural and geographical patterns can also be better matched for the national food security. However, the previous researches focus mainly on the spatial layout at the scale of specific administrative districts. It is still lacking in the replacement of farmland with the restored land. Taking Fengkai County in Guangdong Province as an example, this study aims to follow the micro adjustment on "transferring out existing farmland and transferring in restored land". Firstly, the spatial superposition and comprehensive evaluation methods were used to identify the farmland that transferred out with the fragmented, unstable and low production potential. Secondly, the screening utility function was constructed based on the three objectives of the maximization of agricultural production suitability, the minimization of the importance of ecosystem service functions, and the maximization of layout compactness of the restored land. An optimal model was also constructed to adjust the spatial layout of farmland, according to the two aspects of transferring in and out. Taking the balance of the number of transfers in and out as a constraint, the spatial layout of farmland was optimized at different administrative scales. The results showed that: 1) A total of 1,689.89 hm² of farmland was transferred out of the study area, accounting for 7.62% of the total area of farmland. The overall distribution of farmland was characterized by "global fragmentation and local aggregation". 2) The average suitability of agricultural production and integrated ecosystem services in the restored land were 67.04 and 40.52, respectively, indicating the superior resource endowment in agricultural and ecological production. 3) There were significant differences in farmland that transferred in at administrative scales. The average suitability of agricultural production increased by 2.08 in the farmland that transferred in, whereas, the mean value of comprehensive ecosystem services decreased by 0.67 in the intra-county balance scenario, compared with the intra-town one. The screening of farmland that transferred in was more effective at a wider spatial scale. 4) The quality, stability, and contiguity of optimal farmlands were improved in both scenarios. The optimization was much more outstanding in the intra-county balance scenario, compared with the intra-town one. There were also significant impacts on the administrative scales. An optimal expansion in the screening scale of restored land can be expected to improve the overall quality of farmland and reduce the probability of screening ecologically important land. There were two contributions of this study. Firstly, an optimal model was constructed on the spatial layout with better applicability. The dynamic adjustment was realized to optimize the current farmland and the restored land. Secondly, there were some differences in the spatial layout of farmland at the scale of administrative regions. The administrative regions can be considered to formulate the policies for farmland protection. The finding can provide a strong reference for the decision-making on the optimization of spatial layout of restored land and farmland.