Recent Trends in Blooming Dates of Spring Flowers in Korea

The spring season in Korea features a dynamic landscape with a variety of flowers such as magnolias, azaleas, forsythias, cherry blossoms and royal azaleas flowering sequentially one after another. This enables local governments to earn substantial sightseeing revenues thanks to festivals featuring spring flowers, and bee keepers who move from the southern tip of the Korean Peninsula all the way northward in quest of spring flowers to secure nectar sources over a sustained period of time. However, the narrowing of areal differences in flowering dates and those among the flower species is taking a toll on economic and shared communal values of seasonal landscape. Data on flowering dates of forsythias and cherry blossoms, two typical spring flower species, as observed for the recent 60 years in 7 weather stations of Korea Meteorological Administration (KMA) indicate that the difference spanning the flowering date of forsythias, the flower blooming earlier in spring, and that of cherry blossoms that flower later than forsythias was 30 days at the longest and 14 days on an average in the climatological normal year for the period 1951 - 1980, comparing with the period 1981 - 2010 when the difference narrowed to 21 days at the longest and 11 days on an average. The year 2014 in particular saw the gap further narrowing down to 7 days, making it possible to see forsythias and cherry blossoms blooming at the same time in the same location. The synchronized flowering of the two flower species is attributable to the fact that acceleration of flowering due to abnormally high spring temperature was more significant in cherry blossoms that flower later than forsythias. In the case of the 1951-1980 normal year, while cherry blossom flowering dates as observed by 7 weather stations across the nation ranged from March 31 to April 19 (an areal difference of 20 days), for the 1981 - 2010 normal year the difference ranged from March 29 to April 12 (with an areal difference of 16 days), thus further narrowing the gap, and in 2014 the gap in flowering dates further shrank to a duration spanning March 25 and March 30 (with an areal difference of 6 days). On the other hand, in the case of forsythias for the 1951-1980 normal year, flowering dates from the 7 weather stations ranged from March 17 through April 5 (an areal difference of 20 days), comparing with the 1981 - 2010 normal year when the flowering dates narrowed down to a duration from March 17 through April 2 (an areal difference of 17 days), and the year 2014 saw the range of flowering dates further narrowing from March 16 to March 27 (an areal difference of 12 days), with the gap of decrease getting narrower than in cherry blossoms. It is presumed that the latest climate change pattern in the Korean Peninsula as indicated by rapid temperature hikes in late spring contrastive to slow temperature rise in early spring immediately after dormancy release brought forward the flowering date of cherry blossoms which comes later than forsythias which flowers early in spring. A phenology-based flowering model that can explain this phenomena could contribute toward the clarifying of multi-faceted and complex effects of the flowering pattern change on terrestrial ecosystems.