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

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.