秦淮河流域近30年不透水面景观格局时空演变研究

不透水面作为表征城市化的重要指标,具有极其重要的生态学意义。本文选取多时相Landsat影像,以秦淮河流域为研究区,通过旋转森林算法得到9年土地利用覆盖图,并综合不透水率动态变化分析、土地利用变化轨迹分析、景观格局指数分析探究大流域尺度在近30年间不透水面景观格局的演变过程,旨在揭示其在城市化背景下的时空演变规律。研究结果表明：近30年来,秦淮河流域城市化进程推动下的景观格局变化显著,不透水面积增长近4倍,景观优势度大幅提升;城市化格局演变在2001-2003年前后具有明显差异,前期城市扩张以南京城区与江宁区为主,后期南京城区不透水面扩张大大减缓,而溧水区与句容市扩张速度大幅提升;城市化建设后期,流域内不透水面斑块形状复杂度降低、散布与并列情况减少、斑块的连通性、聚集度逐步增加,其中连通性水平较高的地区主要集中在南京城区和江宁区。

Quantifying the Spatial-Temporal Changes of Impervious Surface Landscape Pattern from1988 to 2015 in Qinhuai River Basin

Urbanization has made natural and semi-natural landscape to be gradually replaced by impervious surface, which has caused significant reduction of surface permeability in urban region. Along with these changes, profound transformations have occurred in hydrological processes, water environment, urban thermal environment, and ecological service system. Impervious surface is an important indicator of characterizing the urban expansion, which has extremely important ecological implications. We chose the multi-temporal Landsat images as our data sources, and took Qinhuai River Basin as the research area in this study. Rotation forest algorithm, which belongs to the category of ensemble learning that synthesizes the advantages of different classifiers and effectively addresses the limits of the information provided by a single image, was used to produce the nine-year land cover maps of Qinhuai River Basin. Focusing on the large watershed scale, we explored the changing process of the urban landscape pattern in the research area during the past 30 years. Impervious surface coverage dynamic analysis was used to reveal the changes of impervious surface area. Land cover change trajectory analysis was used to explore the resources of impervious surface and transformation process of land cover. Landscape metrics analysis was used to quantify the spatial and temporal changes of impervious surface pattern. We aimed to reveal the spatial-temporal changing characteristics of urban landscape configuration against the background of urbanization. The results showed that the landscape pattern has changed significantly during the past 30 years. Overall, the impervious area has increased by nearly four times. The dominance of the impervious surface has increased greatly. The analysis suggested that the turning point of urban expansion is between 2001 and 2003. Urban expansion mainly occurred in Nanjing city and Jiangning district before the turning point, while the impervious surface expansion rate of Nanjing city has greatly decreased after that. At the same time, there is a sharp rise in the expansion rate of Lishui and Jurong districts. The impervious surface within the 2001-2003 period had the highest spatial heterogeneity, which then decreased significantly after the turning point until 2015. The shape of the impervious patches has becoming simpler at the latter stage, and the impervious surface has turned from a dispersed distribution into a distribution pattern with higher connectivity. Besides, the area with high level of connectivity is mainly distributed in Nanjing city and Jiangning district.