School of Remote Sensing and Information Engineering, Wuhan University, Wuhan 430079, China; School of Life Sciences and School of Sustainability, Arizona State University, Tempe, AZ 85287, USA.
School of Remote Sensing and Information Engineering, Wuhan University, Wuhan 430079, China.
Sci Total Environ. 2020 Sep 15;735:139490. doi: 10.1016/j.scitotenv.2020.139490. Epub 2020 May 16.
Rapid urbanization and land expansion persistently shrink urban green field, which accelerates soil sealing and land degradation. Spatio-tempral pattern analysis of green field caused by soil sealing contributes to its protection but quantitative tools are rare. Taking Shanghai-Hangzhou Bay Urban Agglomeration (SHBUA) as an example, we interpreted Landsat imagery into three categories: green filed (such as farmland, grass, forest etc.), gray field (impervious surface) and water bodies in 1994, 2003, 2009, and 2015. We first analyzed swallowed green field by soil sealing and then calculated density (proportion) of green field in concentric rings using gradient analysis. Results show that green field density increases slowly around the city center followed by a sharp increase from urban core areas to urban fringe, and then slowly increases again until at a stable level, presenting an S-shape overall. We proposed an S-shaped function that can fit the spatial gradient of green field density well in nine represented cities. We further compare spatial gradients of densities of green field and gray field. This study provides a quantitative tool to characterize the spatial distribution of green field within cities, which supports to find hotspots of green field loss due to soil sealing and further identify prior areas for green field protection.
快速的城市化和土地扩张持续压缩城市绿地，加速了土壤封盖和土地退化。对土壤封盖导致的绿地时空格局进行分析有助于保护绿地，但定量工具却很缺乏。以上海-杭州湾城市群（SHBUA）为例，我们将 Landsat 图像解译为三类：绿地（如农田、草地、森林等）、灰色地（不透水面）和水体，解译时间分别为 1994 年、2003 年、2009 年和 2015 年。我们首先分析了土壤封盖吞噬的绿地，然后使用梯度分析计算了同心环内的绿地密度（比例）。结果表明，城市中心绿地密度增长缓慢，随后从城市核心区到城市边缘迅速增加，然后再次缓慢增加，直到达到稳定水平，总体呈 S 形。我们提出了一个 S 形函数，可以很好地拟合 9 个代表城市的绿地密度空间梯度。我们进一步比较了绿地和灰色地密度的空间梯度。本研究提供了一种定量工具，可以描述城市内部绿地的空间分布，有助于发现因土壤封盖而导致的绿地损失热点，并进一步确定优先保护绿地的区域。
