School of Ecology and Environmental Science, Yunnan University, Kunming 650091, China.
Institute of International Rivers and Eco-security, Yunnan University, Kunming 650091, China.
Ying Yong Sheng Tai Xue Bao. 2023 Sep;34(9):2436-2444. doi: 10.13287/j.1001-9332.202309.019.
Rapid urbanization would have significant impacts on vegetation phenology. However, the factors influencing the spatiotemporal changes in urban vegetation phenology are still unclear. We used five fitting methods to construct normalized difference vegetation index (NDVI) curves in the Beijing-Tianjin-Hebei urban agglomeration, and obtained the phenology characteristics of urban vegetation in this area from 2001 to 2019 by the threshold method. We compared the spring and autumn phenology in urban built-up areas and hilly areas, and analyzed the effects of precipitation, air temperature, and land surface temperature (LST) on vegetation phenology. The results showed that from 2001 to 2019, the start of the growing season (SOS) in urban built-up areas in the Beijing-Tianjin-Hebei agglomeration was on average 16.88 days earlier than that in hilly areas, and that the end of the growing season (EOS) in urban built-up areas was 12.22 days later than that in hilly areas. During the study period, the SOS of vegetation in urban built-up areas of the Beijing-Tianjin-Hebei region had been gradually delayed, while that in hilly areas was gradually advanced, and the rate of change of phenology in the urban built-up areas was faster than that in the hilly areas. The difference between the SOS of the two areas decreased significantly over time (-0.58 d·a). As for the EOS, the urban built-up areas and hilly areas both showed a trend of delayed, but the differences between them was not significant with time (-0.10 d·a). The contribution of LST in the urban built-up areas to SOS was close to that of air temperature, while the contribution of LST in hilly areas to SOS was only 1/2 of that of air temperature, indicating that the heat island effect and air temperature within the city jointly influenced urban vegetation phenology, and their contributions were almost equal. The results could help understand the role of urbanization in the variations of vegetation phenology and provide a reference for further assessment of carbon sink potential of urban vegetation.
快速的城市化进程将对植被物候产生重大影响。然而，影响城市植被物候时空变化的因素仍不清楚。我们使用了五种拟合方法来构建京津冀城市群归一化植被指数（NDVI）曲线，并通过阈值法获得了该地区 2001 年至 2019 年的城市植被物候特征。我们比较了城市建成区和丘陵区的春、秋物候，并分析了降水、气温和地表温度（LST）对植被物候的影响。结果表明，2001 年至 2019 年，京津冀城市群城市建成区的生长季开始时间（SOS）平均比丘陵区早 16.88 天，生长季结束时间（EOS）比丘陵区晚 12.22 天。研究期间，京津冀城市群城市建成区植被的 SOS 逐渐推迟，而丘陵区的 SOS 逐渐提前，城市建成区物候变化的速度比丘陵区快。两地区之间的 SOS 差异随时间显著减小（-0.58 d·a）。至于 EOS，城市建成区和丘陵区都表现出推迟的趋势，但随时间变化差异不显著（-0.10 d·a）。城市建成区的 LST 对 SOS 的贡献接近气温，而丘陵区的 LST 对 SOS 的贡献仅为气温的 1/2，表明城市热岛效应和城市内部气温共同影响城市植被物候，其贡献几乎相等。研究结果有助于理解城市化对植被物候变化的作用，为进一步评估城市植被碳汇潜力提供参考。
