在城乡协调发展的背景下,本文以自然属性为基础分析了北京具有不同经济属性的5类耕地的空间结构。波谱分析显示,不同类型耕地的空间分布具有不同的周期,它们共同形成了距天安门约23～44km(近郊平原)、44～66km(远郊平原)、66～126km(山区)的耕地宏观空间结构。通过计算各类耕地的空间维数和Hurst指数,认为景观农田区、美化农田区、近郊山区22～47km圈层的耕地不具备分形特征;规模农田区、景观廊道带、中远郊山区48～126km圈层的耕地由于受城市发展、自然条件、距离等因素的影响具有明显的分形特征。总体上,北京不同类型的耕地处于一种离散、连续和具有共度性、没有公度性的融合状态。

The spatial structures of five types of cultivated land with various economic attributes in Beijing are analyzed in this paper based on natural attributes in the context of harmonious development of urban and rural functions.The spectrum analysis shows that the layout of different types cultivated land has different periodicity,and that they together form the spatial structure of macroscopic suburban agriculture,about 23-44 km(suburban plain),44-66 km(exurb plain),66-126 km(mountain) from Tian'anmen.Based on this analysis,the paper calculates the spatial dimension and Hurst index of four cultivated land types,and argues that the cultivated lands of landscape greening area,beautified farmland area and the 22-47 km circle of suburban mountainous areas do not have fractal characteristics.The development of scale farmland area is affected by distance,and landscape corridor belt is impacted by urban development,and the 48-126 km circle of central suburbs and mountainous areas is affected by natural conditions.The fractal characteristics of the cultivated lands of the three are obvious.On the whole,cultivated land in Beijing is in a discrete-continuous and commensurability-incommensurability integration status.