基于核密度估算的大都市耕地数量空间分布特征分析*——以天津市为例

ANALYSIS OF SPATIAL DISTRIBUTION CHARACTERISTICS OF CULTIVATED LAND BASED ON KERNEL DENSITY ESTIMATION IN METROPOLIS*——A CASE STUDY IN TIANJIN

关键词:  耕地分布特征核密度大都市天津市

Key words:  cultivated land  distribution characteristics  nuclear density  metropolis  Tianjin city

摘要:

［目的］耕地资源是人类生存和发展的基础性资源，通过研究大都市耕地空间分布特征，为耕地保护和优化耕地空间布局提供科学依据。［方法］文章利用土地利用现状矢量数据在ArcGIS 101中提取出耕地要素图层，采用重心模型确定城市重心位置，运用象限分析法把天津市分成8个方位，分析天津市的耕地空间数量分布特征，利用核密度估算法计算天津市耕地数量的核密度值，继而采用自然断点法进行核密度分区来确定天津市耕地密度等级，分析的耕地空间聚集分布特征，总结出影响耕地空间分布的主导因素，针对性地提出耕地保护建议。［结果］（1）耕地核密度变化范围为0~8687 point/km2，核密度值由小变大，耕地整体呈由分散向聚集状态演变，天津市主要是以中低密度区（36525 696万hm2）为主，整个区域内的耕地呈分散状态分布； （2）中心城区无耕地可用，耕地核密度等级结构单一； 近郊区的耕地核密度等级结构复杂多样且变化趋势相似，耕地聚集程度适中； 远郊区的耕地面积较多，耕地核密度等级结构不同，耕地聚集程度相差较大。（3）天津市耕地分布主要受到地形地势、土壤、经济发展、城镇扩展、土地相关规划及政策等多方面因素影响。［结论］天津市耕地在各区各方位的空间分布呈现不同特征，借助核密度估算法能更加细致深入地研究大都市耕地在不同空间的聚集程度，对促进耕地空间优化布局与合理利用具有重要的研究意义。

Abstract:

Cultivated land resources are the basic resources for human survival and development. By studying the spatial distribution characteristics of cultivated land in metropolitan areas, this paper provides scientific basis for protecting and optimizing the spatial distribution of cultivated land. It used the vector data of land use status to extract the cultivated land element layer by ArcGIS 10.1, applied gravity center model to determine the position of city gravity center, and it used quadrant analysis method to divide Tianjin into eight orientations, and analyzed the spatial distribution characteristics of cultivated land, then it utilized nuclear density estimation method to calculate the number of cultivated land, exploited Jenks for dividing the nuclear density to determine the density grade of cultivated land, analyzed the spatial distribution characteristics of cultivated land, summarized the dominant factors affecting the spatial distribution of cultivated land, put forward specific proposals for cultivated land protection. The results showed that: (1) The change range of nuclear density of cultivated land was 0~86.87 point/km2, the nuclear density value increased from small to large, the whole cultivated land changed from scattered to aggregated, the main area of Tianjin was low density zone (365 256.96 hm2), and the cultivated land in the whole area was scattered. (2) There was no arable land available in central urban area, and the nuclear density grading structure of arable land was single; the nuclear density grading structure of arable land in the suburbs was complex and diverse, and the change trend was similar, and the degree of arable land aggregation was moderate; the arable land area in the outer suburbs was more, the nuclear density grading structure of arable land was different, and the degree of arable land aggregation was quite different. (3) The distribution of cultivated land in Tianjin was mainly affected by many factors, such as topography, soil, economic development, urban expansion, land related planning and policies. The spatial distribution of cultivated land in Tianjin showed different characteristics in different areas, with the help of nuclear density estimation method, the cultivated land aggregation degree of metropolis in different spaces could be studied more carefully and deeply, it was of great significance to promote the optimal spatial distribution and rational utilization of cultivated land.