北京市耕地功能空间差异及其演变

城市化对耕地及其功能具有深刻影响，这在大都市郊区尤为明显。立足北京市，构建耕地功能评价指标体系，运用极差标准化法处理数据，采用层次分析法确定指标权重，最后运用加权求和法得出功能值。研究表明：① 在北京各区县，2004-2011 年间单位面积耕地的生产、生态、文化和社会功能几乎均增强，空间差异表现为生产和社会功能远郊平原区高于远郊山区和近郊区，生态功能远郊平原区高于远郊山区，文化功能近郊区高于远郊区。② 北京远郊平原区的粮食、蔬菜和瓜类生产功能均较强，但农业污染较严重。受距市中心距离影响，近郊区耕地文化功能需求量较大，远郊区供给量较大。③ 2004-2011 年间绝大部分区县单位面积耕地的总功能增强，受地形和市中心经济辐射影响，远郊平原区高于远郊山区和近郊区。④ 根据耕地总功能组成比重，把北京市耕地分为四种类型：生产型（远郊平原区）、生态型（近郊区）、文化型（丰台区和门头沟区）与社会型（远郊山区）.

Spatial differences and evolution of arable land functions in Beijing

The development of rapid urbanization exerts influence in arable land and also deeply affects transformation of its functions, especially in the suburb of metropolises. Using Beijing as a case study, this paper establishes an evaluation index system of arable land functions, then standardizes data with extreme difference value method and determines index weights with the AHP method. Finally, we use weight sum method to calculate function values. The main conclusions include: (1) Production, ecological, cultural and social functions in per unit area of arable land were enhanced in almost all districts during the period 2004-2011. The spatial differences show that: production and social functions in outer suburban plain areas were higher than those in outer suburban mountain areas and inner suburban districts, ecological function in outer suburban plain areas was higher than that in outer suburban mountain areas, and cultural function in inner suburban districts was higher than that in outer ones. (2) The production functions of grain, vegetables and melons in outer suburban plain areas were all stronger, but the agricultural pollution in these areas was more serious. In addtion, influenced by distance from city center, the demand of cultural function in inner suburban areas was higher than that in outer suburban districts. (3) The total function of arable land was enhanced in most districts during the period 2004-2011. Similarly, influenced by terrain condition and central economic radiation, the total function of arable land in the outer suburban plain areas was stronger than that of other districts. (4) According to the proportion of total function, arable land can be divided into four categories: production type (outer suburban plain areas), ecological type (inner suburban areas), cultural type (Fengtai and Mentougou districts), and social type (outer suburban mountainous areas).