As urbanization and urban sprawl speeding up, the contradiction between urban expansion and the pro-tection of basic farmland gets more and more serious. Studying the change of the basic farmland in the context of the rapid urbanization can provide scientific support for policies formulation and implementation. Based on the second land survey in 2009 and the planning in 2012 as basic data, this paper compared the differences of basic farmland from quantity, distribution and quality in Chang-an district of Xi′an using ArcGIS spatial overlay analysis, and analyzed the influence of the constructed land expansion on the spatial arrangement. The results showed that the quantity of basic farmland was increasing, but the quality was dropping; the degree of land fragmentation was in-creasing. The main source of urban expansion was incremental land, but the added constructed land changed from agricultural land. The main motivation of urban expansion was the huge value added space due to the basic farm-land transformation. Urban expansion will lead to a decline in basic farmland quality and the contradiction between basic farmland quantity and economic development.%[目的]随着城市化与工业化进程的加快,城市扩张与基本农田保护之间的矛盾日益突出.研究快速城市化下基本农田的变化,能够为相关规划的编制和保护政策的制定提供科学支撑.[方法]文章以西安市长安区为例,以2009年二调基本农田和2012年规划基本农田为基础数据,基于ArcGIS技术与景观格局分析方法,对比长安区基本农田的数量、 质量差异及空间分布特征,探讨城市建设用地扩张与土地增值收益对基本农田变化的影响.[结果](1)基本农田数量有所增加,质量有所下降;(2)基本农田空间分布呈现出由中心向外围扩散趋势,破碎化程度提高;(3)城市扩张的土地来源主要是增量土地,新增建设用地主要由农地转化而来,基本农田被侵占明显,且沿主要道路和乡镇边界被侵占严重;(4)基本农田转变用途后的巨大增值空间是城市扩张的主要动机.[结论]城市扩张会导致大城市周边基本农田质量的下降,同时既要保基本农田数量又要保经济发展的矛盾迫使基本农田破碎化程度提高.
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