Suitability evaluation of urban construction land based on supply and demand in Yangzhou City
MENGLin1,, GUOJie1,2,3, SUNChi1, OUMinghao1,2,3, 1. College of Land Management, Nanjing Agricultural University, Nanjing 210095, China2. Center of Urban-rural Joint Development and Land Management Innovation, Nanjing 210095, China3. State and Local Joint Engineering Research Center of Rural Land Resources Utilization and Consolidation, Nanjing 210095, China 通讯作者:通讯作者:欧名豪,E-mail: mhou@njau.edu.cn 收稿日期:2017-05-10 修回日期:2017-11-14 网络出版日期:2018-01-20 版权声明:2018《资源科学》编辑部《资源科学》编辑部 基金资助:国家自然科学基金项目(71774086)国家自然科学基金项目(71774085)江苏省普通高校学术学位研究生创新计划项目(KYLX15_0540) 作者简介: -->作者简介:孟霖,女,山东济南市人,博士生,主要研究方向为土地利用规划与管理。E-mail: 465545167@qq.com
关键词:城镇建设用地;适宜性评价;供求理论;BP神经网络;扬州市 Abstract We established an evaluation index system of urban construction land suitability based on the theory of supply and demand, and calculated the suitability of urban construction land using BP neural networks in order to construct theoretical and practical foundations for the scientific allocation of urban construction land. Based on the theory of supply and demand, the suitability evaluation index system of urban construction land can be constructed according to background conditions, technical level, location and transportation, intensive degree, population density, and economic development. BP neural networks reflect the suitability of urban construction land for each evaluation unit, which helps to improve the precision of urban construction land suitability evaluation results. The research area can be divided into four regions. The highly suitable region area can be used for large-scale urban construction land development. The basically suitable region can fully develop relying on the highly suitable region and expand urban construction land moderately. The barely suitable region requires basic farmland protection and ecological protection, and the green industry with natural ecological protection and economic development benefits should be selectively developed. The unsuitable region should be given more policy support to ensure food security and ecological security. By comparing the suitability evaluation results of urban construction land and the layout of planning new urban construction land of ‘Rall Plan for Land Utilization of Yangzhou (2006-2020 year)’, most of the planning new urban construction land is located in the highly suitable area and the basically suitable region. However, some planning new urban construction land is located in the barely suitable region and unsuitable region respectively, so some or all of these should be eliminated or adjusted to highly suitable and suitable areas.
商品价格受供给与需求制约,供求关系是市场机制运行的基础[13,24]。市场经济条件下,作为生产要素之一的土地以“特殊商品”形式进入市场,必然受到供求规律的影响[25],供求理论是资源合理配置的理论基础[26]。城镇建设用地适宜性不仅受社会经济发展需求的影响,同样也受供给的制约,城镇建设用地规模实际上是土地供给与需求相互作用下的动态均衡[1]。由于城镇建设用地作为土地资源被设置为固定用途——用于城市社会经济发展,因此城镇建设用地供给主要为经济供给,即以无弹性的自然供给为基础,并受本底条件、技术水平、区位交通、土地利用集约化程度等条件制约[25],导致城镇建设用地供给存在极限;而伴随社会经济快速发展,人口密度增加导致生活空间需求增大,经济发展规模变高导致生产空间需求增强,促使城镇建设用地需求量不断增长。有限的城镇建设用地供给与不断增长的需求之间产生供求差,通过市场运行机制的调节作用,最终决定城镇建设用地开发的适宜性。因此,本文从土地供给与需求角度,构建城镇建设用地适宜性评价的理论分析框架(见图1、表1)。 显示原图|下载原图ZIP|生成PPT 图1供求影响城镇建设用地适宜性的理论框架 -->Figure 1The theoretical framework of supply and demand factors affecting the evaluation of urban construction land -->
Table 1 表1 表1扬州市城镇建设用地适宜性评价指标体系 Table 1Index system of suitability evaluation of urban construction land in Yangzhou City
依据《土地评价纲要》[38]中土地适宜性评价分级标准,将扬州市城镇建设用地适宜性划分为高度适宜、基本适宜、勉强适宜、不适宜四级。考虑到不同指标对城镇建设用地适宜性影响程度存在差异,因此对单因子同样划分为高度适宜、基本适宜、勉强适宜、不适宜四个等级,根据现有规程与相关研究,构建扬州市城镇建设用地适宜等级分级标准。其中,坡度参考中国地形地貌划分标准及相关研究分级[7,14,15,39];距建成区距离借鉴《城市用地分类与规划建设用地分类标准》[40]以及现有文献中的分级方案[30,41];距水域距离、距生态保护区距离依据《扬州生态市建设规划(2000-2020)》[33]、《江苏省重要生态功能保护区区域规划》[42]、《扬州市生态红线区域优化调整论证报告》[43]及相关研究进行分级[5,17];距公路距离参考《江苏省公路条例》[44]及其他相关研究进行量化分 级[28,45];距基本农田保护区距离参照已有研究量化分级[37,46];工业技改投入、地均固定资产投资、城镇人口密度、二三产业增加值采用自然段点法划分为四级[13,14,15,16](见表2)。 Table 2 表2 表2扬州市城镇建设用地适宜等级分级标准 Table 2Grading standard of urban construction land suitability in Yangzhou City
训练样本的选择是BP神经网络构建的关键,直接影响BP网络模型训练效果和城镇建设用地适宜性评价的结果[47,48]。将城镇建设用地适宜性评价BP神经网络模型的期望输出值限制在0到1之间,设定期望输出1.00~0.75为高度适宜,0.75~0.50为基本适宜,0.50~0.25为勉强适宜,0.25~0.00为不适宜。以扬州市城镇建设用地适宜性等级分级的临界值作为训练样本,样本期望输出分别设置为1.00、0.75、0.50、0.00,构成了四组样本数据(见表3)。 Tab. 3 表3 表3扬州市城镇建设用地适宜性评价BP模型训练样本 Tab. 3Samples of urban construction land suitability evaluation based on BP neural network in Yangzhou City
评价区域总面积为154 037.04hm2,运用训练好的BP网络模型进行网络仿真,测算各评价单元的城镇建设用地适宜性指数,得到城镇建设用地适宜性评价分级结果。叠加《扬州市土地利用总体规划(2006—2020年)》[22]中新增城镇建设用地布局,验证规划新增城镇建设用地布局的适宜性[8,15,39](见图3)。 显示原图|下载原图ZIP|生成PPT 图3扬州市城镇建设用地适宜性评价结果 -->Figure 3Suitability evaluation results of urban construction land in Yangzhou City -->
(1)本文基于供求理论,从土地供给与需求角度构建城镇建设用地适宜性评价理论框架,并从本底条件、技术水平、区位交通、集约程度、人口密度、经济发展等方面选择10个指标构建城镇建设用地适宜性评价指标体系,一定程度上提高了城镇建设用地适宜性评价指标体系建立的合理性。 (2)运用BP神经网络进行扬州市城镇建设用地适宜性评价,避免权重确定的主观性和对客观数据的过分依赖,具有传统方法不可比拟的优越性。由于BP神经网络具有自学习能力,在进行城镇建设用地适宜性评价时,评价指标对城镇建设用地的影响规律可以通过BP模型对样本的训练获得,不需要事先确定指标的具体权重,这在一定程度上避免权重确定的完全主观性和对客观数据的过分依赖性,准确反映不同的评价单元对城镇建设用地的适宜性,有助于提高城镇建设用地适宜性评价结果的精度。 (3)根据测算结果,研究区潜在城镇建设用地空间可分为城镇建设用地高度适宜区、基本适宜区、勉强适宜区及不适宜区,其中:①高度适宜区可进行大规模城镇建设,促进城镇建设用地组团式发展,注重产业结构优化升级,避免大规模城镇扩张对生态环境造成破坏;②基本适宜区可依靠高度适宜区发展,适度配置城镇建设用地,避免过度开发导致的城镇建设用地无序蔓延、征而不建和土地闲置等现象;③勉强适宜区应以基本农田与生态保护优先,着力提高粮食产量与生物多样性,选择性发展具有自然生态保护和经济开发效益的绿色产业;④不适宜区多近邻水域、生态保护区等生态敏感区,且社会经济基础十分薄弱,应注重通过政策扶持,着重增加区域植被覆盖,减少水土流失,保障粮食安全和生态安全,促进土地资源的可持续利用。 (4)将城镇建设用地适宜性评价结果与《扬州市土地利用总体规划(2006—2020年)》中新增城镇建设用地布局对比分析发现,规划新增城镇建设用地分别有64.97%、25.04 %位于高度适宜区与基本适宜区,城镇建设用地适宜性评价结果与土地利用总体规划吻合度较高,说明本研究方法具有可行性,且规划新增城镇建设用地配置基本满足区域供求关系。但有9.15 %与0.84 %规划新增城镇建设用地分别位于勉强适宜区与不适宜区,两区城镇建设用地供给条件较差,需求规模不高,城镇建设用地供求适宜性较差,规划配置新增城镇建设用地易导致不符合供给条件的地类转换为城镇建设用地,造成供给剩余,不利于区域土地市场供求平衡的维护;且新增城镇建设用地闲置,原有地类生产、服务功能降低,易导致土地社会、经济、生态效益下降,土地集约利用程度降低。为避免城镇建设用地盲目扩张,建议将区内部分或全部规划新增城镇建设用地剔除或调整至高度适宜区与基本适宜区。 (5)本文旨在为城镇建设用地适宜性评价提供一种科学、可行的方法,但适宜性评价指标繁多,且BP神经网络的模型函数的选择、训练参数等相关参数的确定也会对评价结果的准确性产生影响,如何更加科学地扩充适宜性指标体系、挑选BP神经网络的模型函数、训练参数等相关参数,仍有待进一步研究。 The authors have declared that no competing interests exist.
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