基于地貌分区的1990-2015年中国耕地时空特征变化分析

地形地貌通过分配地表水分和热量制约耕地的利用形式和成效,对耕地质量具有非常重要的决定意义,以地貌分区的视角研究中国耕地变化具有重要意义。根据1990-2015年中国6期土地利用空间数据和地貌分区数据,运用GIS空间叠加分析方法,分析中国耕地1990-2015年的面积变化和空间分布格局,进一步探讨不同地貌分区下的耕地新增与流失方向。结果表明,中国耕地面积略有增加,但总体变化不大,耕地面积从1990年的17715万hm²增加到2015年的17851万hm²,平均每年增加5.44万hm²,每年增幅仅为0.03%。耕地主要分布在平原地区,台地、丘陵次之;新增耕地主要来源为草地、林地和未利用地。东部平原低山丘陵区（I）耕地面积最大,而西北高中山盆地高原区（IV）耕地动态度明显高于其他地貌区。空间上呈现“南减北增,新增耕地的重心向西北移动”的特征。1990-2015年间,西北高中山盆地高原区（IV）和东部平原低山丘陵区（I）为耕地面积增长区,平均每年增加耕地面积分别为8.9万hm²和5.4万hm²;东南低山丘陵平原区（II）和西南中低山高原盆地区（V）为耕地面积减少区,平均每年减少耕地面积分别为5.9万hm²和2.8万hm²;而华北—内蒙东中山高原区（III）和青藏高原高山极高山盆地谷地区（VI）耕地面积几乎没有变化,平均每年变化仅为0.15 万hm²和0.06万 hm²。耕地流失主要发生在东部平原低山丘陵区（I）和东南低山丘陵平原区（II）,主要原因为城镇化进程加快带来的建设用地对优质耕地的大量占用;而新增耕地主要发生在西北高中山盆地高原区（IV）,多来自于对草地和未利用地的开垦。

Spatial-temporal distribution of cropland in China based on geomorphologic regionalization during 1990-2015

Landform is an important factor determining the spatial pattern of cropland through allocating surface water and heat. Therefore, it is of great significance to study the change of cropland distribution from the perspective of geomorphologic division. Based on China's multi-year land cover data (1990, 1995, 2000, 2005, 2010 and 2015) and geomorphologic regionalization data, we analyzed the change of cropland area and its distribution pattern in six geomorphologic regions of China over the period 1990-2015 with the aid of GIS techniques. Our results showed that the total cropland area increased from 177.1 to 178.5 million hectares with an average increase rate of 0.03%. Cropland acreage decreased in southern China and increased in northern China. Region I (eastern hilly plains) had the highest cropland increase rate, while the dynamic degree of Region IV (northwestern middle and high mountains, basins and plateaus) was significantly higher than that of other regions. The barycenter of China's land cultivation had shifted from North China to northwest over the 25 years. Regions IV and I were the two high-growth regions of cultivated land. Region II (southeastern low-middle mountains) and Region V (southwestern middle and low mountains, plateaus and basins) were the main decreasing regions of cultivated land. The area of cultivated land remained almost unchanged in Region III (north China and Inner Mongolia eastern-central mountains and plateaus) and Region VI (Tibetan Plateau). The loss of cropland occurred mostly in regions I and II as a result of growing industrialization and urbanization, while the increase of cropland occurred mainly in Region IV because of reclamation of grasslands and other wastelands.