大城市近郊县域耕地保护预警方法

县域是耕地保护及预警最为合理的研究尺度，综合应用土地利用规划、年度计划和农用地分等定级成果，预测耕地资源“量”与“质”的变化趋势是科学合理地保护耕地的有效手段。该文在单项指标和综合指标2个层次上，从耕地数量、稳定生产能力、易变养分的空间变化和综合4个方面构建了县域耕地保护预警体系，并对北京市顺义区进行了耕地保护预警研究。顺义区耕地保护单项指标预警结果表明，2007、2008年顺义区耕地数量出现轻警，2009、2010年则为无警；耕地稳定生产能力在2007、2009年为中警，2008年为重警，2010年为轻警；而易变养分含量变化的警情则不尽相同。综合指标预警结果表明：2007年顺义区耕地保护出现重警，2008年和2009年为中警，2010年为轻警。研究结果从预警的时间尺度和空间尺度出发，全面考虑了耕地的数量变化和质量变化，并使警情判定与土地管理和农业生产工作相衔接，是进行区域耕地保护预警研究的有效方法。

Methods for early-warning of cultivated land protection in outskirts of megapolis

It is the county level that is the most reasonable scale for research of arable land protection and warning. To protect arable land scientifically and rationally, prediction of the trend of its quantity and quality, with land use planning, annual plan and agricultural land classification and gradation results, is supposed to be an effective means. An early-warning study of cultivated land protection was carried out based on constructing a warning system from the aspects of farmland quantity, stability of grain yield capacity, spatial changes of the volatile nutrient and harmony degree between development and land protection, taking Shunyi District, Beijing, as study area. Among the four aspects, the first three were early-warning types of single index, the last one was the type of an comprehensive one. The single index early-warnings results indicated that the farmland quantity changes in Shunyi District, Beijing, took on light warning in 2007 and 2008, and no warnings in 2009 and 2010; the grain yield production capacity showed middle warnings in 2007 and 2009, serious warning in 2008, light warnings in 2010; and the nutrient changes differs from one another. Moreover the results of the comprehensive indices early-warning indicated a serious warning result in 2007, middle warnings in 2008 and 2009, a light one in 2010. This paper provide an efficient method to carry on the early-warning of cultivated land, which can pre-warn the quantity changes and quality changes of the cultivated land from both temporal scales and spatial scales, and it was closely connected with the practice of land resource management and agriculture production.