近30年长江中下游平原典型区耕地覆盖变化

Change of cropland in typical area of Middle-Lower Yangtze Plain over the past 30 years

以长江中下游平原苏皖边界的10个县市为研究区,利用1984,1990,1995,2000,2005和2010年6期的TM/ETM+图像提取土地覆盖信息,从时间和空间2个方面研究耕地覆盖变化。结果表明:①从时间变化来看,研究区近30 a耕地总体呈减少趋势,经历了快速减少、缓慢减少和急剧减少3个过程,1984—1990年、1990—2000年及2000—2010年耕地分别减少了374.10 km2,66.09 km2及1 724.33 km2,主要表现为城镇和水体侵占耕地,但林地开垦使耕地增加;②从空间变化上看,沿江城市周围大面积耕地转变为建设用地,以1984年的南京市区、马鞍山市区和芜湖市区为主,且城镇化速度在加快;1990年以来沿石臼湖和固城湖周边地区的部分耕地转变成养殖塘,其西部地区转换较频繁;1984—2000年耕地沿山体和耕地交界处增加,2000年之后又因实施退耕还林和营造经济林而有所减少。

In order to analyze the spatial-temporal change characteristics of the cropland in typical areas of Middle-Lower Yangtze Plains from 1984 to 2010 , the authors extracted the land cover information of the study area in 1984, 1990, 1995, 2000, 2005 and 2010 from Landsat TM/ETM＋ images. The results show that the amount of cropland decreased over the past 30 years. There were three stages of the cropland change： Fast reduction, slow reduction, and sharp reduction. The total area of cropland loss was 374. 10 km2 from 1984 to 1990. The decrease of cropland was 66. 09 km2 from 1990 to 2000, and the loss speed was relatively slow. The cropland in the study area was reduced rapidly to 1 724. 33 km2 from 2000 to 2010. Most of the lost cropland was transformed into the construction land, and the cropland in cities along the Yangtze River, such as Nanjing, Maanshan, and Wuhu, was decreased more seriously than that in counties. The speed of urbanization was accelerated. Moreover, plenty of cropland was turned into ponds to breed fish and crabs around the Shijiu Lake and the Gucheng Lake, particularly in western regions where the conversion was prominently frequent from 1990. On the other hand, cropland was increased along the boundary of cropland and mountain from 1984 to 2000. After that, the cropland decreased because of the implementation of returning cropland to forest and creating economic forest.