1985-2010年南京市耕地变化轨迹及驱动力分析

随着经济的快速发展,城市化程度加剧,南京市的土地利用发生了巨大变化.基于1985-2010年覆盖南京市的Landsat MSS/TM卫星影像,利用最大似然法获取南京市历年土地利用数据,将其归纳为耕地和非耕地2类.基于分类结果,提取并归纳了恒定耕地、恒定非耕地、转变为耕地、转变为非耕地和短暂性耕地5种耕地类型的变化趋势,借助景观水平上的斑块占景观面积的比例以及散布与并列指数来分析5种耕地类型变化趋势的景观格局时空动态,以说明耕地扩张和遗弃的时空轨迹.结果表明：（1） 1985-2010年,耕地面积减少40.42％;（2）恒定耕地面积在方位3所占比例最大,为56.89％,转变为非耕地主要分布在方位1、6和8,揭示了城市扩张的主要方向;（3）恒定耕地类型主要分布于六合区,面积为895.92 km2,转变为非耕地主要分布于江宁区;（4）恒定非耕地集中于市中心附近,而恒定耕地则远离市中心分布;（5）恒定耕地仍占主导地位,转变为非耕地具有较高破碎度.短暂性耕地面积不稳定,较易发生土地撂荒乃至土地退化;（6）人口与产业重心转移、经济发展、政策和城市扩张是显著影响耕地空间格局的关键因素.

Trajectory and Driving Forces of Change in Farmland in Nanjing During the Period From 1985 to 2010.

With rapid economic development,urbanization of Nanjing is accelerated vigorously,thus causing tremendous change in land use in the region.Based on Landsat MSS/TM images of the region from 1985 to 2010,land use data of the past years were acquired using the maximum likelihood method and sorted into two categories,farmland and non-farmland.Based on the classification,the land was further sorted into five groups,that is,permanent farmland,permanent nonfarmland,transforming into farmland,transforming into non-farmland and tentative farmland,in light of their natures of land use,showing trends of the change in land use.Spatio-temporal dynamics of the landscape patterns of the five groups of land in change were analyzed using the percentage of landscape index （PLAND）,and the interspersion and juxtaposition index （IJI） to show spatio-temporal trajectories of the farmland in expansion and desertion.Results show that （1） the farmland decreased in area by 40.42% from 1985 to 2010; （2） permanent farmland in Azimuth 3 was the highest in area,accounting for 56.89% of the total; transformation into non-farmland occurred mainly in Azimuths 1,6 and 8,which reveals the main direction of urbanization; （3） permanent farmland was mainly distributed in Luhe District,making up 895.92 km2 and transformation into non-farmland occurred mainly in Jiangning District; （4） permanent non-farmland was mainly located in the urban region while permanent farmland was in the opposite direction; （5） permanent farmland was still in dominancy,land under transformation into non-farmland was highly fragmented and tentative farmland was not stable in area and susceptible to desertion and even degradation ; and （6） shifting of the population and industrial centers,economic development,policies and urban expansion were the key factors significantly affecting change in farmland.