Winter bud development was as sessed on well growth regrafts of 7 clones of Taiwania (Taiwania cryptomerioides Hay.) which were randomly divided into 2 sites at different elevations: 1,050m (Chitou) and 750 m (Yeou-Shoei-Keng). Air temperatures were record at both sites. The “chilling-heat sum sequential model” was used to estimate the threshold temperature, chilling requirement (h), and heat sum (degree-hrs) for bud burst of each clone. The differences in onset date of bud dormancy between the 2 sites and among the 7 clones in the year of 2000 were less than 2 wk. However, there was a considerable variation in bud burst date between the earliest clone and the latest one, which was as long as 5 wkat Chitou and 3 wk at Yeou-Shoei-Keng. The estimated threshold temperature for all 7 clones was 10℃. The chilling requirement was at least 55h or 58h, and the heat sums varied from 9,410 to 16,387 degree-hrs. The results revealed that the clones had undergone genetic differentiation of their phenol logical characteristics. Comparing individuals of same clone grown at 2 different sites, there was no significant difference in the heat sum for bud burst (P>0.05), but the end dates for releasing end odormancy differed from 1.5 to 2.5 mo.
Winter bud development was as sessed on well growth regrafts of 7 clones of Taiwania (Taiwania cryptomerioides Hay.) which were randomly divided into 2 sites at different elevations: 1,050m (Chitou) and 750 m (Yeou-Shoei-Keng). Air temperatures were record at both sites. The “chilling-heat sum sequential model” was used to estimate the threshold temperature, chilling requirement (h), and heat sum (degree-hrs) for bud burst of each clone. The differences in onset date of bud dormancy between the 2 sites and among the 7 clones in the year of 2000 were less than 2 wk. However, there was a considerable variation in bud burst date between the earliest clone and the latest one, which was as long as 5 wkat Chitou and 3 wk at Yeou-Shoei-Keng. The estimated threshold temperature for all 7 clones was 10℃. The chilling requirement was at least 55h or 58h, and the heat sums varied from 9,410 to 16,387 degree-hrs. The results revealed that the clones had undergone genetic differentiation of their phenol logical characteristics. Comparing individuals of same clone grown at 2 different sites, there was no significant difference in the heat sum for bud burst (P>0.05), but the end dates for releasing end odormancy differed from 1.5 to 2.5 mo.