雪山地區玉山杜鵑物候之研究

Phenology of Rhododendron pseudochrysanthum in Mt. Xue

高山植物位處於侷限的高山環境，有如島嶼生態系相對脆弱，其物候在氣候變遷研究是值得深入探討之對象。本研究針對雪山地區之玉山杜鵑物候進行調查，探討海拔、光照、坡向等因子與物候之關係。2010年調查發現，玉山杜鵑之始花期、終花期、展葉期與海拔呈現顯著正相關；開花歷時、每花序花朵數、每枝條新葉數與海拔呈顯著負相關。此現象反映出玉山杜鵑物候期隨海拔升高而愈慢開始，每枝條的花朵數與葉數隨海拔升高而減少。再者，玉山杜鵑的始花期、展葉期在 3種不同海拔環境呈顯著差異，由於海拔反映溫度的變化，顯示隨海拔升高，熱量累積較緩慢，熱量多寡為造成玉山杜鵑物候時序變化的主因。玉山杜鵑的始花期與展葉期在光環境和坡向類別上無顯著差異，經事後檢定比較發現始花期及展葉期在不同生育地間均以草生地的植株最早發生，此可能與其所在生育地的溫度和光度有關。此外，不同光照環境生育地的玉山杜鵑，在每花序花朵數、每枝條新葉數呈現顯著差異，事後檢定比較顯示，玉山杜鵑在陽光充足的生育地的每花序花朵數和每枝新葉數較森林陰暗環境高，可能顯示光度環境對植物生物量累積具重要影響。另外，坡向對各種物候現象不顯著，但事後分析檢定發現，南向和西南向坡的個體，其始花期較其它坡向早，此可能由陽光照射時間長短差異不同所致。圈谷的玉山杜鵑開花期與雪山較低海拔植株有明顯錯開現象，導致圈谷個體在開花時缺乏與其他地區個體交流的機會，此可能為造成玉山杜鵑種複合群的因子之一。 Alpine is one of the most sensitive and fragile environments, where the plant live and its phenology is an important indicator to climate change. Phenology of Yushan azalea (Rhododendron pseudochrysanthum) was surveyed in Mt. Xue from February to December 2010. The purposes are carried on the relationship between habitats as altitude, lighting environment and aspect, etc., and phenologies as flowering and leaf expansion fi rst fl owering date (FFD), end fl owering date (EFD) and leaf expansion date (LED) showed signifi cantly positive correlated with altitude; however, fl owering duration, fl ower number/ branch, leaf number/branch were signifi cantly negative correlated with altitude. These phenomena indicated Yushan azalea phenology initiate late and reduced the number of fl owers and leaf per branch along with altitude. Furthermore, FFD and LED of Yushan azalea were significant difference at different altitudes. According to altitude is an indirect factor which reflects temperature and heat. And heat accumulated is more slowly with altitude increasing, that indicate heat accumulated is the major factor of FFD and LED of R. pseudochrysanthum. Although, FFD and LED were correlate insignifi cant difference in lighting and aspect habitats. The LSD post hoc tests indicated that FFD and LED of individuals at grassland were initiated earliest than other habitats. It might indicate the phenology was associate with temperature and light. In addition, the number of flowers and leaves per branch at different lighting habitat showed significant difference. LSD post hoc tests showed that Yushan azalea which under the forest with the lowest number of fl owers and leaves per branch. It showed lighting environment is an important impact on plant biomass accumulation. Although, the phenomena of phenology were showed insignificantly between different aspects; the post hoc tests indicate the FFD of Yushan azalea at aspect of south ~ southwest was earlier than the other aspects. It might refl ect the duration of sunlight. Flowering phenology of Yushan azalea at cirque was not overlap with other individuals at low altitudes, which indicate these cirque individuals miss the opportunity of gene fl ow. And the fl owering phenology character might be one of the conformational factors to be R. pseudochrysanthum species complex