街区尺度城市内部动态度的量化——以深圳市为例

Quantifying within-city landscape dynamics at the block level: a case study of Shenzhen

城市动态度反应城市土地利用/土地覆盖动态变化的剧烈程度,对其进行量化是理解城市景观变化和进行城市生态空间监管的基础。现有研究主要聚焦城市扩张引起的特定地类(如人工表面、植被等)的动态变化,缺乏对城市内部精细尺度上(如街区尺度)景观动态的研究。以深圳市为例,首先利用多等级道路数据划分街区,进而基于高分辨率卫星影像解译的土地覆盖数据,利用土地利用动态度和土地利用强度指数量化街区尺度城市内部动态度。研究结果表明:(1)深圳市城市内部动态度较高,2017—2018年期间,14.93%的街区发生了不同程度的变化,热点区域主要分布在南山区、宝安区、盐田区等。(2)街区的变化包括多种地类的转变,其中,林地转变为裸土最为常见,占比为12.59%。由城市更新引起的地类变化也较普遍,如其他不透水地表向裸土的转移和建筑到裸地的转变分别为6.20%、5.59%。此外,深圳市街区的土地利用强度也存在较大差异,表现为土地利用强度增加的街区多分布在城市外围,而土地利用强度降低的街区则多分布在城市内部。(3)街区动态度与街区大小之间呈现非线性关系,街区动态度随着街区面积的增大,先急剧下降,后趋于平缓。本研究揭示了深圳市城市内部街区尺度上土地覆盖的动态变化特征,可为城市规划和生态空间管理提供科学支撑。

Urban landscapes are highly dynamic. Understanding the within-city dynamics in land cover and land use is important. Previous studies have largely focused on the changes of specific land use type(impervious surface, urban vegetation etc.) resulted from urban sprawl on large or medium scales. However, research on quantifying the urban dynamics on block scale is lacking. Taking Shenzhen as a case study area, this paper aims to use the land cover thematic maps interpreted from very high-resolution remote sensing images to quantify the urban dynamics within city at street block level. The results showed that:(1) there was high dynamics at street block level in Shenzhen, which was manifested as that the blocks with dynamic changes account for 14.93%. The hotspots of degree of urban dynamics were distributed in Nanshan, Baoan and Yantian district.(2) The contribution of dynamic changes(CDC) was significantly different between different land use changes on block scale. For all blocks, the CDC of change from woodland to bare soil was the highest(12.59%). In addition, CDC of land use and land cover changes which mainly resulted from urban renewal was high. For example, CDC of changes from other impervious surface and building to bare soil were 6.20% and 5.59%, respectively. In addition, the land use intensity of different block was obviously different. The blocks with increased land-use intensity were mostly distributed in the periphery of the city, while the blocks with decreased land-use intensity were mostly distributed in the interior of the city.(3) The relationship between dynamics of block and block size was nonlinear. With the block size increasing, the dynamics of block decreased sharply and then the decreasing trend became flat. Our study revealed the characteristics of the land use dynamics at street block level in Shenzhen, and it would provide a reference for urban planning and ecological space management.