Altered Trends in Spring- and Autumn-Flowering Species in Japan in Response to Global Warming

Abstract

Recent phenological studies have shown that the onset of flowering is significantly affected by global warming, which causes plant phenological shifts. It has been reported that spring-flowering species bloom earlier and autumn-flowering species bloom later when the temperature increases, but it was unclear whether both trends were prevalent in Japan. In this study, we examined responses to temperature increase and trends in phenological shifts using the flowering records of 350 Japanese native taxa collected at the Tsukuba Botanical Garden over the past 20 years. We observed that 64 taxa showed a significant negative correlation with temperature and advanced trends, whereas 17 taxa showed a significant positive correlation with temperature and delayed trends. The former bloomed mainly in spring (March–June), whereas the latter bloomed mainly in autumn (September–November). The distributions of 57 taxa that were significantly correlated with temperature increases but did not show any clear advanced/delayed trends were spring-biased, suggesting that spring-flowering phenology should be carefully monitored.