The relationship between urban climate and plant phenology in Kumagaya city (1)

Recent changes of plant phenology such as budding, flowering and coloring and falling of leaves are related to global warming and heat islands developing in city areas. For example leaf - color - change dates (LCC dates) of Ginkgo biloba and Acer palmatum have been getting later annually. There are some studies of the relationship between recent urban heat islands and plant phenology. However, many of them are about Cherry blossoms <Prunus yedoensis> (Omoto and aono, 1990; Masuda, Yoshino and Park, 1999). In this study the authors researched the relationship between urban climate and the LCC dates of Ginkgo biloba and Acer palmatum in Kumagaya, Saitama Prefecture, Japan. The objects of this study are as follows : First, is to evaluate how urban climate influences the LCC dates of these trees. Second, is to search whether these LCC dates are possible indicators that show climatic changes such as urban warming including global warming. As a result, it is clear that LCC dates are earlier in the suburbs of the city than in the center. For example, Ginkgo biloba is about 2~3 weeks earlier and Acer palmatum is about 1 week ~10 days earlier. However, in the case of LCC dates of Ginkgo biloba, there are general wide variances (about 3~4 weeks maximum) and variations exist among a group of trees at one observation point. It is considered therefore, that in addition to temperature, botanical factors (such as a difference of budding dates and the difference between male and female) are related to the LCC dates of Ginkgo biloba. On the other hand, in the case of Acer palmatum, the LCC dates correspond to urban temperatures around midnight, when heat islands are noticeable. So it is concluded that heat islands influence the LCC dates of Acer palmatum, and therefore the LCC dates of Acer palmatum are possible indicators that show climatic changes and urban warming.<br>