都市农业功能空间分异研究——以西安都市圈为例

Spatial differentiation of urban agricultural ecosystem services —A case study of Xi'an metropolitan zone

城市化导致都市农业功能呈现明显的空间分异特征,其研究有助于实现都市农业功能的空间合理布局与优化、协调与城市社会经济功能的发展。结合西安都市圈都市农业的发展现状,构建都市农业的生产经济功能、就业功能、文化休闲功能和生态功能的评价指标体系,运用ArcGIS的格网化技术从0.5 km×0.5 km尺度测评并分析都市农业功能的空间分异特征。结果表明:受农业自然资源条件和城市化水平空间分布差异的影响,生产经济功能整体上表现出从西南向东北递增、从近郊平原区向中远郊平原区递增的空间格局;就业功能受区县农业发展水平以及社会经济综合发展水平的作用,表现出秦岭山区低于平原区、近郊平原区向中远郊平原区递增趋势的空间分布规律;文化休闲功能受距离衰减规律支配表现出明显的中心—外围型的圈层空间结构,道路、河流、旅游景区又进一步影响各种功能值分布区的具体空间形态;西安都市圈的地貌地形、都市农业用地类型及其破碎化程度决定都市农业生态功能在空间上表现出由都市圈边缘区域至中心区域逐渐下降的趋势特征,并且各种生态功能值分布区的破碎零散化现象比较严重。

In recent years, study of urban agriculture has shifted from definition, characterization and its services to development evaluation, modeling, spatial distribution and ecological security. It has also shifted from qualitative analysis to quantitative research. Most studies on spatial differentiation of urban agriculture have mainly focused on spatial distribution of specific industries to show urban agricultural spatial regulation. However, spatial differentiation research in terms of services is few. Thus exploring spatial distribution of urban agricultural services is critical for breakthrough discoveries in spatial characteristics of urban agriculture, as well as spatial rules of urban agro-ecosystem services. This study was designed in that effort, to explore the governing laws of spatial distribution of urban agricultural ecosystem services. It aimed to accomplish rational spatial distribution and optimization of urban agricultural ecosystem services by coordinating urban agricultural development and urban social and economic functional services. In reference to previous studies and current circumstances of urban agricultural development in Xi’an metropolitan zone, this paper set up an evaluation index system to quantify urban agricultural ecosystem services. The services included production, economy, employment, culture and recreation, and ecological services. In order to show the spatial characteristics of urban agricultural ecosystem services at a high spatial precision, the paper used ArcGIS-based grid （0.5 km × 0.5 km） analysis to map spatial differentiation of each services of urban agriculture in Xi’an metropolitan zone. Driven by the distribution of agricultural resources and differentiation of urbanization level, production and economic services were higher in plain areas than in mountain and loess hilly-gully regions. These services gradually increased from southwest to northeast and from suburban plains to outer-suburb plains. Based on differentiation of urban agricultural land types, production efficiency and urbanization level in each county, the employment service increased from suburban plains to outer-suburb plains, with lower values for Qinling Mountains than those for plain areas. Different rationalities of spatial distribution were noted in regional social stability. Culture and recreational services showed the core-periphery distribution patterns, driven by law of decay with distance. Roads, rivers and scenic spots constituted further distribution patterns of group concentration, shaft strips or shaft agglomeration. Based on topography and level of urbanization, ecological service decreased from edge-zone to center zone of city circle. Urban agriculture in outer-suburbs constituted of ecological shelter zone of Xi’an metropolitan zone. After mastering the laws and the current conditions of spatial distribution of urban agricultural ecosystem services, it was critical to evaluate the rationality of spatial distribution of urban agricultural ecosystem services in the study area.