Quantitative measure of the cultivated land change rationality in Metropolitan Mountainous Areas: A case study in Mentougou District
都市山区耕地资源演变的定量测度——以北京市门头沟区为例

Beijing is facing many land use problems brought by fast economic growth, especially in the mountainous areas. Many researchers have attached great importance to the studies of cultivated land change. Taking Mentougou District (a typical mountainous area in Beijing) as a case, based on the detailed data of land use status quo (2001, 2008) and the conversion matrix of cultivated land data among other land use types from 2001 to 2008, we selected several geography factors such as slope related to the change and distances away from rural settlements and traffic lines to analyze the evolution trends of cultivated land in this District with the support of GIS technology. Theoretically, coupling relationship between income of rural residents and cultivated land conversion may affect the sustainability of agricultural production and rural development. Coupled with the relationship between average income of rural residents and cultivated land conversion matrix, rationality of cultivated land changes were quantitatively measured based on village-level statistical data. The results indicate that areas with slopes between 0~2° are mostly bothered by cultivated land loss, which decreased continuously with the increase of distances away from rural settlements. Conversions of cultivated land also show close relationship with the distribution of traffic roads. Newly added cultivated lands tend to expand around rural settlements and traffic lines, but they are of high probability for being abandoned due to enlarged farming radius and low quality. After coupling the cultivated land conversion matrix and income of rural residents, the rationality of cultivated land change was divided into four types, namely irrational increase, irrational decrease, rational increase and rational decrease. The increasing rate of rural residents'income in 87 villages exceeds corresponding decreasing rate of cultivated land and they belong to rational decrease type. 36 villages fall into the type of irrational decrease for the increasing rate of rural residents'income is lower than corresponding decreasing rate of cultivated land. Because of the marginality of newly added cultivated land, 14 villages are classified as irrational increase type for the increasing rate of cultivated land is higher than that of rural residents 'income. Conversely, 27 villages are of rational increase type. At the end of this paper, strategies about how to use system to protect cultivated land, how to innovate the protection concept and how to consolidate the land were put forward to prompt the sustainable utilization of cultivated land resource in metropolitan mountainous areas.