北京市植被覆盖度时空变化特征及其对城市化的响应

Spatial and Temporal Characteristics of Fractional Vegetation Cover and Its Response to Urbanization in Beijing

研究植被覆盖度(FVC)时空变化并分析其对不同尺度城市化的响应机制,对北京市生态环境保护和修复具有重要实践意义.利用长时间序列FVC数据集、土地利用数据等,运用Theil-Sen Median和Mann-Kendall等方法分析了2000~2020年北京市FVC时空变化特征;进而将城市化指数作为城市化进程的关键表征指标,采用剖面线分析和全域网格分析法探讨FVC对不同城市化梯度的响应.结果表明:①2000~2020年,北京市FVC呈现整体向好发展态势,以显著增加为主(28.68%),分布在生态涵养区和以天安门广场为中心,同心圆式外延10~12 km的范围内;海淀区、朝阳区、丰台区、石景山区和昌平区的城市化指数及FVC变化速率较大;②北京市人造地表20年间增幅11.50%,空间集聚态势显著且空间分异性强,整体表现为中心城区>平原区>生态涵养区;③FVC与城市化指数呈现显著负相关,表明城市化对区域FVC产生负面影响;但随着城市化进程趋于稳定,这种负相关性会逐渐减弱,表现为中心城区虽以低植被覆盖为主,但植被变化呈显著增加趋势.研究结果可为制定北京市植被修复方案和生态管理措施提供依据.

Exploration of the spatiotemporal changes in fractional vegetation cover(FVC)and its response characteristics to urbanization is of great significance for urban ecological protection and planning in Beijing.This study analyzed the spatiotemporal characteristics of vegetation cover changes in Beijing from 2000 to 2020 using the Theil-Sen Median and Mann-Kendall methods based on a long-term time series vegetation cover dataset.Then,this study used the urbanization index as a key indicator of spatial urbanization and utilized the transect line and global grid analysis methods to investigate the response characteristics of FVC to different urbanization gradients.The results indicated that:①FVC changes showed spatial and temporal heterogeneity.From 2000 to 2020,Beijing was predominantly covered by high vegetation,accounting for 65.22%of the total area,which was mainly distributed in ecological conservation areas consistent with the Jundu,Xishan,and Yaji Mountain ranges.The FVC presented an overall positive development trend,with a decreasing trend of areas with low FVC.The increase in FVC was significant(by 28.68%),mainly distributed in ecological conservation areas and within a range of 10-12 km in concentric circles centered around Tiananmen Square.The urbanization index and FVC change rate were relatively high in Haidian District,Chaoyang District,Fengtai District,Shijingshan District,and Changping District.②The artificial land surface in 2000,2010,and 2020 was 9.69%,13.64%,and 21.19%,respectively,with significant spatial agglomeration and strong spatial heterogeneity.During the urbanization process in Beijing,the increase in artificial land surface reached 11.5%,with the conversion from arable land to artificial land surface accounting for 53.83%of the total land use conversion area.③There was a significant negative correlation between FVC and the urbanization index,indicating that urbanization had a negative impact on regional FVC.However,as the urbanization process stabilized,this negative correlation tended to gradually weaken.Although the central urban areas were mainly characterized by low FVC,there was a significant increasing trend in the FVC,indicating a positive development in the FVC and an improvement in regional ecological quality,which was closely related to the governance of the mountain-water-forest-field-lake-grass-sand system.The results of the study can provide a basis for the development of vegetation restoration programs and ecological management measures in Beijing.