Quantification of Temperature Effect on <i>Prunus yedoensis</i> Matsum. Flowering in Gyeongnam Province of Korea

Abstract

This experiment was conducted to predict the flowering time of cherry blossoms. The phenological model was used to predict the accurate flowering time, and investigate the daily temperature to calculate the chilling requirement for the flowering of Prunus yedoensis Matsum. Twigs of several decades-old trees were collected on January 3, 2010 and were kept in a 2℃ refrigerator. From January 16, 2010 onward, more twigs were collected from the same field every week. Twigs of both groups were laid in water in a 25℃ growth chamber. To determine the bud-burst date and the period required for dormancy break, the state of flower buds was observed every day. The daily maximum and minimum temperatures were also collected to calculate the accumulated degree hour of the chilling requirement until the dormancy was broken. To fined out the threshold temperature and chilling requirement for the approximate flowering date, the equation was used to set the threshold temperature from 5℃ to 9℃ at intervals of 0.1℃ and calculate chill days and anti-chill days repeatedly. The equations for calculating daily Cd and Ca, are given in Table 1 for each of the five cases. Based on this prediction model, the most optimized threshold temperatures and chilling requirements were predicted to be 5.8℃ and -116.8. The broken day of the rest was estimated to be February 17. The model, used for predicting the flowering day of Prunus yedoensis Matsum. from 2012 - 2019, showed that RMSE is 2.5 days when using the measured temperature and 4.4 days when used the average March temperature of 30 years (1980 – 2010). The results showed improvement compared with the previously announced predictions of flowering days.