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.