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Enhancing Cherry Blossom Predictions Amid Climate Change
Japan’s iconic cherry blossoms, known as sakura, attract millions of visitors each spring as they bloom from the southern Kyushu region up to the northern reaches of Hokkaido. The most prevalent variety, Somei Yoshino, is particularly celebrated for its synchronized flowering, creating a breathtaking display of delicate white-pink blossoms that captivates both locals and tourists. Anticipation builds around the blooming forecasts, with detailed tracking of flowering times influencing travel plans and local festivities. However, the effects of climate change are complicating these predictions, altering the timing of these beloved blooms.
Recently, a collaborative research effort between Kyushu University and the Forestry and Forest Products Research Institute has developed a groundbreaking model aimed at accurately predicting when Somei Yoshino cherry buds will emerge from dormancy. Their study, released in the journal Plants, People, Planet on September 19, offers insight into the implications of climate change on the cherry blossom flowering schedule, particularly in southern Japan.
For cherry trees to blossom, their buds must successfully navigate two crucial dormancy phases: endodormancy and ecodormancy. The former requires a chilling period characterized by cool winter temperatures, whereas the latter phase demands warmer conditions in spring to stimulate bud growth.
As explained by Atsuko Miyawaki-Kuwakado, the lead author and a JSPS Research Fellow at Kyushu University’s Faculty of Science, the dual requirements for cooling and heating lead to unpredictable flowering times. “Depending on the thermal conditions in autumn, winter, and spring, the timing of the cherry blossom could either arrive early, be delayed, or fail to occur entirely,” she noted.
The transition from ecodormancy to blooming is rapid, but determining precisely when endodormancy concludes is more complex, as no significant visual changes occur in the buds during this critical phase. To explore these nuances, Miyawaki-Kuwakado and senior author Professor Akiko Satake investigated the genetic activity within the buds to pinpoint this key moment.
From October onward, the researchers collected leaf and bud samples monthly from Yoshino cherry trees at locations across Japan, including Fukuoka, Tsukuba, and Hokkaido. This extensive sampling allowed them to monitor gene expression patterns across five distinct seasons: early summer, summer, autumn, winter, and spring, closely tied to temperature variances.
Focusing on a specific group of genes associated with bud dormancy, known as DAM genes, the researchers identified that DAM4 plays a pivotal role in facilitating endodormancy. The findings revealed that while DAM4 expression was high at the onset of winter, its levels dropped as temperatures consistently fell below 10.1°C. This reduction signified the end of dormancy, with the buds able to flower upon exposure to sufficiently warming conditions.
Based on their observations, the research team determined that Yoshino cherry trees need an average of 61 days of temperatures below the 10.1°C threshold to break endodormancy. They utilized historical climate data from the Japan Meteorological Agency to conclude that between 1990 and 2020, the onset of endodormancy has shifted approximately 2.3 days later each decade.
The implications of this model are significant for future forecasting, as it may enhance the accuracy of bloom predictions for Yoshino cherry trees. Researchers are also assessing how climate change could further impact flowering patterns, emphasizing the need for proactive measures.
“The ability of Yoshino buds to flower hinges on having sufficient cool periods during winter. Without those necessary conditions, the buds remain dormant and fail to bloom,” commented Miyawaki-Kuwakado. “Understanding the potential effects of global warming, especially in southern Japan, is crucial for developing strategies to mitigate these changes.”
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