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北京市植物物候对热岛效应的响应

花匠小妙招
2024-11-12 02:32

摘要： 都市的快速发展致使城市热岛效应日渐加剧。城市绿化对缓解热岛效应有一定的作用，但同时其物候也受到了影响。本文基于遥感影像数据，通过对照北京市热岛区与非热岛区、不同热岛强度等级的植物物候差别，研究热岛效应对植物物候的影响。采用Landsat 8影像对北京市地表温度进行反演，结合空间分析进行热岛效应分区分级识别；通过MOD13A1的归一化植被指数（NDVI）数据，采用Dallimer平均值法和动态阈值法提取植被生长季始期(SOG)、生长季末期（EOG）、生长季长度（LOG）等重要植被物候参数，研究植被物候在热岛区与非热岛区、不同热岛强度等级之间的差异。结果表明：北京市夏季与冬季相比，热岛效应更为显著；利用Dallimer平均值法提取的北京市热岛区SOG比非热岛区提前4 d，EOG延迟9 d，LOG延长13 d；利用动态阈值法提取的SOG提早10 d，EOG推迟4 d，LOG延长14 d，动态阈值法提取的物候信息与观测的物候信息更为接近；随着热岛强度等级提高，SOG提前，EOG推迟，LOG延长。本研究丰富了我国华北地区植被物候对热岛效应的响应机制，同时对研究全球变暖对生态系统的影响具有一定价值。

关键词: 热岛效应, 植物物候, NDVI, 北京市, 动态阈值法

Abstract: The rapid development of cities increases urban heat island (UHI) effect. Urban greening can alleviate the heat island effect, but plant phenology could be affected by the heat island effect. Using remote sensing images, we compared the plant phenology between UHI areas and non-UHI areas as well as the different levels of UHI intensity in Beijing. Landsat-8 images for Beijing were used to invert the land surface temperature (LST). Spatial analysis methods were used to identify UHI zones and the UHI intensity classification. With data of normalized differential vegetation index (NDVI) of MOD13A1, three phenological parameters (start of growth season (SOG), end of growth season (EOG), and length of growth season (LOG)) were extracted by the Dallimer mean value method and dynamic threshold method. The three parameters were used to examine the differences in plant phenology between the UHI areas and the non-UHI areas and between different UHI intensity levels. The UHI effect of Beijing in summer was more obvious than that in winter. The SOG in the UHI areas extracted by Dallimer mean value method was four days earlier, the EOG was nine days later, and the LOG was 13 days longer than that in non-UHI areas. The SOG in UHI areas extracted by dynamic threshold method was 10 days earlier, the EOG was four days later, and the LOG was 14 days longer than that in nonUHI areas. Compared with the Dallimer mean value method, the phenology calculated by the dynamic threshold method was closer to the observation data. Under higher UHI intensity, the SOG would be earlier, the EOG would be later, and the LOG would be longer. This study enriches the response mechanism of plant phenology to the UHI effect in North China, which helps us to understand the effects of global warming on ecosystems.

Key words: heat island effect, plant phenology, NDVI, Beijing, dynamic threshold method.