基于动态遥感数据的北京主城区环带间植被覆盖变化

20世纪80年代以来,北京市进入高速城市化进程,主城区(六环内)植被覆盖发生了巨大变化。分别利用1984年、1995年、2004年和2014年的8—9月北京六环内的Landsat遥感数据,对其进行辐射定标、大气校正和拼接裁剪,以计算归一化植被指数(NDVI),获取3个10年间和各环带植被覆盖面积及覆盖度的变化。结果显示:六环内植被覆盖度由1984年的76.80%(1 742.44 km ²)降至2014年的48.73%(1 105.61 km ²)。虽然2014年与1984年相比二环内和二环至三环植被覆盖度分别增加8.43和4.33个百分点,但三环至四环、四环至五环、五环至六环植被覆盖度降幅逐渐增大,降幅分别为12.23、27.62、32.97个百分点。建议通过空间规划手段为不同环带间以植被覆盖为代表的城市生态系统建设提供差异化思路:如三环内应结合城市精细化治理为核心区留白增绿,见缝插绿;三环至五环间随着城市建设趋于稳定,为中型城市生态空间的增建带来机遇;五环至六环间可结合百万亩造林,增加都市农田等方式,建设多种类大型城市绿色空间,进而综合提升北京主城区城市生态系统服务功能。

Study on the spatial-temporal change of vegetation coverage between the belts of Beijing's main urban area based on dynamic remote sensing data

Beijing has been undergoing rapid urbanization since 1980s. A tremendous change in vegetation coverage can be observed in main city area (the 6th-Ring Road). Based on the Landsat remote sensing database collected during the periods of August or September in 1984, 1995, 2004 and 2014 respectively, a comprehensive study on radiometric calibration, atmospheric correction, and splicing combined with cutting in the 6th-Ring Road of Beijing was carried out. By using NDVI and other methods, the change of vegetation coverage over the three decades of each ring was obtained. The results indicated that the percentage of internal vegetation coverage decreased from 76.80% (1 742.44 km 2) to 48.73% (1 105.61 km 2) in three decades from 1984. The vegetation coverage in the 2nd-Ring road and to the 3rd-Ring road increased by 8.43 and 4.33 percentage point respectively in 2014 and 1984, however the vegetation coverage outside of the 3rd-Ring decreased growing, which was 12.23, 27.62, 32.97 percentage point respectively. Research conclusion include that it is necessary to propose differentiation ideas on urban ecosystem construction, e.g., vegetation coverage between different zones through spatial planning means. The inner 3rd-Ring Road demands urban fine governance aiming to encourage the development of green space rather than building areas. As the urban construction between the third to the 5th-Ring Road tends to stabilize, more opportunities appear for the expansion of the medium-sized urban ecological space. Moreover, the afforestation of million acres and the increase of urban farmland could be accomplished for 5th-Ring and 6th-Ring Road. Through these planning approaches, it is expected to build a variety of urban green spaces system, and furthermore, comprehensively enhance the urban ecosystem services of Beijing’s main urban area.