三位一体视角下三峡库区耕地资源内外转换轨迹和特征——以江津区为例

Trajectories and Characteristics of Internal and External Transformation of Cultivated Land Resources in the Three Gorges Reservoir Area from the Perspective of the Trinity——Taking Jiangjin District as an Example

耕地资源约束趋紧下,区域发展和多维消费需求取决于耕地数量、质量、生态“三位一体”保护,揭示变化耕地的转换轨迹及“数、质、生”特征是确保耕地得到有效三位保护的前提,也是未来耕地保护的施策重点。基于2009—2018年土地利用数据和耕地质量等级评价成果,采用土地利用转换矩阵和景观生态风险指数等方法,从耕地内部和外部变化两个方向切入,找出不同时段耕地内外转换的轨迹,解析转换水旱地的“三位”特征,探究了转换耕地的时空变化规律。结果表明:(1)耕地转换以外部转换为主,2009—2012年、2012—2015年、2015—2018年3个阶段均有发生,主要转换类型为耕地与城乡建设用地间的互转,内部转换仅发生在2015—2018年,旱地转水田和水田转旱地数量基本相当。(2)转换耕地质量总体偏高,其中转出旱地主要在10—11等,转出水田主要在8等,而转入旱地以8—12等为主,转入水田以8—9等为主。(3)转换耕地主要分布在低和较高生态风险区,其中旱地转出转入与水田转出均主要发生在低生态风险区,而水田转入主要发生在较高生态风险区。由此可见近10年来耕地转换轨迹从单一外部转换向内外部多元地类转换,同时水田与旱地互转存在显著的阶段性,且低生态风险中高质量的耕地更易被转换。

Under the tightening constraints on cultivated land resources, regional development and multi-dimensional consumption demand depend on the ‘trinity’ protection of quantity, quality and ecology of cultivated land quantity. Revealing the transformation trajectory and morphogenetic characteristics of the changed cultivated land is the premise to ensure the trinity protection of cultivated land effectively, and it is also the focus of policy implementation for future cultivated land protection. Based on the land use data and cultivated land quality grade evaluation results from 2009 to 2018, we used methods such as land use conversion matrix and landscape ecological risk index to cut in from the internal and external changes of cultivated land to find out the trajectory of internal and external conversion of cultivated land in different periods, to analyze the ‘trinity’ characteristics of the conversion of paddy fields and dry lands, and to explore the temporal and spatial variation of the conversion of cultivated land. The results show that:(1) the conversion of cultivated land to external conversion as the main practice in 2009—2012, 2012—2015, 2015—2018 three stages occurred, the main conversion type was the transfer between arable land and urban and rural construction land;the internal conversion only occurred in 2015—2018, and the number of drylands to paddy fields and paddy fields to drylands was basically equal;(2) the quality of the converted cultivated land was generally high, among which the dryland was mainly grade 10—11, the paddy field was mainly grade 8, the dryland was mainly grade 8—12, and the paddy field was mainly grade 8—9;(3) converted cultivated land mainly distributed in low and high ecological risk areas, among which drylands transfer out and paddy fields transfer out mainly occurred in low ecological risk areas, while paddy fields transfer mainly occurred in high ecological risk areas. The conversion trajectory of cultivated land had changed from a single external conversion to an internal and external multiple land type conversion in the past 10 years. At the same time, there were significant stages in the mutual conversion of paddy fields and drylands, and high-quality cultivated land with low ecological risk was more likely to be converted.