Abstract
We analyzed the effects of air temperature rises on dormancy period and flowering period of Japanese pear ‘Kosui’ at three locations (Chiba City, Ichikawa City and Ichinomiya Town) in Chiba prefecture. At these three locations, air temperatures tended to rise at a rate of 0.041–0.068°C per year between 1980 and 2009. The dates of full bloom at Chiba City and Ichikawa City have become earlier at a rate of 0.32–0.36 days per year. At Ichinomiya Town, the dates of full bloom did not change after 1992, although it became earlier until 1991. The dates for breaking of endodormancy at Ichikawa City and Ichinomiya Town tended to be delayed at a rate of 0.42–0.52 days per year, due to decreases in effective chilling exposure caused by air temperature rises. The duration of the ecodormancy stage was shortened at a rate of 0.49–0.78 days per year, due to air temperature rises from February to April. It was demonstrated that the model developed by Sugiura and Honjo (1997) can be adopted by Chiba City and Ichikawa City to predict the date of full bloom in the near future, but is not available to Ichinomiya Town, which has a warmer climate. In Ichinomiya Town, the breaking of endodormancy may become incomplete as air temperature rises by 0.59°C in the future.
