北京城市化进程中早春草本植物开花物候期的变化响应

Abstract

植物物候对城市化的响应是全球变化与城市生态环境效应研究的重要内容.2012 年3 月到6 月,结合气象观测数据,对北京市西北向城市化梯度上7种早春草本植物开花物候期进行观测与研究,发现温度因子和早春草本植物开花物候期均随城市化梯度发生变化,即越靠近城市中心区,温度和积温累计值越高;早春草本植物开花物候期出现时间越早,平均提前2-4 d;但开花期持续时间与开花速率并不随城市化梯度发生明显变化.此外,研究发现北京市7 种早春草本植物开花期对5℃积温变化响应最为敏感;开花期提前时间梯度变化显著性与生活型密切关联,多年生草本植物对城市化梯度变化的响应比一年生或一二年生草本植物明显.未来城市植物物候期研究中,应更关注城市化进程中土地利用/覆被变化与热岛效应对城市气候及植物生理生态特征的累积影响特征,以期进一步揭示植物物候期对城市化及气候变化的响应规律.;The response of vegetation phenology to urbanization and climate changes is one hotpot in the field of urban ecological effect research. Climate changes is expected to alter seasonal biological phenomena such as vegetation growth and animal migration, so vegetation phenology is regarded as a useful indicator to track climate changes. Recent years, many related studies have focused on the long-term response of arbor phenology to regional climate changes. Our research focused on the impact of urban climate change on early spring herbs flowering phenophase with spatial variation. Based on the observation of the flowering times of 7 kinds of early spring herbs from May to June in 2012 along the northwest urbanization gradient in Beijing, this paper analyzed the flowering phenophase change characteristics and mechanism of early spring herbs in the urbanization gradient. The results showed that early spring herbs flowering times were affected by the urbanization process, like woody plants. The average flowering time of the herbs within the 5th Ring Road was 2.3 to 3.6 days earlier than common cases out of them. But the flowering duration and rate of 7 kinds of early spring herbs did not distinctly change with the urbanization gradient, with the exception of the longer flowering duration and faster flowering rate of the herbs between 3th and 4th Ring Road, which might be explained by the new center of the urban heat island caused by the high speed of city construction in this area. The advanced time of the flowering phenophase time changed with the urbanization gradient, that is, the closer to the city center, the earlier of flowering time. Especially the flowering end time was much clearer than the flowering starting and flourishing time. Moreover, the advanced time of the flowering phenophase time of the early spring herbs had a close relationship with life forms of the herbs, which means, perennial herbs were more sensitive to the urbanization gradient than the annual herbs regarding flowering phenophase. It was induced that spring herb flowering phenology has remarkable response to the accumulated impact of urbanization process and the resulting urban heat island. Based on the temperature data from Automatic Weather Stations along the northwest gradient in Beijing, the correlation between the average advanced flowering time and the mean temperature (MT) and accumulated temperature (AT) was examined. It was found that both the Pearson coefficient of MT and AT were no less than 0.85, but the coefficient of AT is larger than that of MT, and the Pearson coefficient of the correlation between AT of 5℃ and the advanced flowering time was the highest and the value of Two-tailed test was the lowest. It was tested that where was closer to the city center, both MT and AT became higher that lead to the flowering time occurred earlier, however, more dominantly affected by AT, especially AT of 5℃. The results contribute to the conclusion that urban heat island during the urbanization process has distinct cumulative effects on the phenophase of herbs. It is suggested that future studies should give more emphasis on the cumulative effects of urban heat island on urban climate change and vegetation phenology.