The analysis of flowering rhythm and its relationship with the distribution of populations of Rhododendron oldhamii Maxim. in western Taiwan
Date Issued
2009
Date
2009
Author(s)
Chi, Wei-Ting
Abstract
In studies of plant reproductive biology, flowering phenology and the classification of flowering types could discover further delicate and diversified flowering patterns. The genus Rhododendron is widely distributed throughout the world. Its flowering periods changed through the latitude and climate variation. The heterogeneity of flowering period of Rhododendron increased in tropical mountains. R. oldhamii Maxim. is an endemic species, and it spreads widely from low to high altitude in Taiwan. The previous study of investigation of R. oldhamii in Nantzuhsienhsi trail, Chiayi County, suggested where flowering time throughout the year and some individuals blooming twice in the year. Its flowering time differs from mass flowering in spring of most other Rhododendron species. This study was to clarify this special flowering rhythm of R. oldhamii for other than Nantzuhsienhsi trail. The 12 study sites were selected from north to south in western Taiwan since January 2007. Results showed that annual flowering period among 1634 individuals varied from 1 to 11 months, and the annual flowering frequency was 1~4 times. The obviously low flowering amounts were in February and June, and the flowering period was divided into two parts flowering in spring and flowering in summer-fall. The individuals of different flowering time were classified as 4 classes based on the number of flowering seasons in a year. These classes can differentiate into 22 types by the flowering seasons and sustainability. The important value index (IVI) of each flowering type was summed up the proportion of flowering individuals and the proportion of flowering amount. The top 4 IVI indicated the most important flowering types which were flowering in spring, in summer-fall, summer-fall-winter, and 4 seasons. The flowering periods were composed of the different individuals of flowering types in 12 sites. The individuals to the north of Dana River were flowering in spring. The individuals in southern Taiwan were flowering throughout the year, but there were low flowering amount in winter. Those at sites of high latitude were flowering in spring and summer. According to the distribution distance and the effect of the northeast monsoon, 12 sites were subdivided into 58 plots. The TWINSPAN resulted in two groups, flowering in spring and other seasons, and the indicators were flowering in spring and flowering in summer-fall. The CCA correlation among plots and environmental factors suggested that the latitude, altitude and the rainfall in May, June, August, and November were highly correlated in plots. This result showed the flowering rhythms were related to plum-rain, the southwest front and the northeast monsoon. The rhythms from floral bud initiation to flowering were classified to 3 types based on the floral bud riding out the winter and the frequency of floral bud formation. Type I was the floral bud initiation once in fall, riding out the winter, and flowering in next spring. Type II was the floral bud initiation once in summer, and flowering in later months. Type III was the floral bud initiation in summer, and flowering in later months, then new shoots sprout and floral bud initiation twice in a year. Results for flowering phenology showed that the phenomenon of flowering throughout the year in western Taiwan consisted of the individuals of flowering in different time and flowering throughout the year. There were constituted different flowering types in study sites. On the other hand, further study of flowering rhythm indicates that the diversity of the period and frequency of floral bud initiation. This study at first clearifies the floral bud to flowering rhythm of the widespread R. oldhamii, and provides the new information of phenology and reproductive evolution. The future perspective is worth discovering the mechanism of diverse flowering rhythm and the meaning for adaptation.
Subjects
Rododendron oldhamii
western Taiwan
flowering rhythm
flowering time
flowering phenology
SDGs
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