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|題 目：||南仁山亞熱帶雨林四種優勢種林木生態生理學之研究 （ Ecophysiological Studies of Four Dominant Tree Species of Subtropical Rain Forest in Nanjenshan）|
本研究以南仁山區四種具有代表性的植物為實驗樹種。大頭茶 (Gordonia axillaris (Roxb.) Dietr.) 及台灣柯 (Pasania formosana (Skan) Schottky) 為迎風坡分佈種；紅花八角(Illicium arborescens Hayata) 與奧氏虎皮楠 (Daphniphyllum glauescens Blume ssp. Oldhamii (Hemsl.) Huang) 為廣泛分佈種。測定各樹種的淨光合作用、蒸散作用、氣孔導度以及黎明前與中午的葉片水勢。
The 3-ha study area of a subtropical rain forest is located in Nanjenshan, southern Taiwan. The climate is markedly seasonal. The study area is subject to strong northeasterly monsoon winds, low temperature and short period of drought in winter season, while it is hot and rainy during the summer months. The purpose of this study is to understand and compare the physiological activities of four plant species between monsoon season and non-monsoon season.
Four plant species were selected in this study. Gordonia axillaris and Pasania formosana are dorminant species on windward sites (windward specialists). Illicium arborescens and Daphniphyllum glauescens are dorminated both on windward and leeward sites (generalist).
The physiological factor studies included net photosynthetic rate, transpiration, stomatal conductance, predawn as well as midday leaf water potential. The results of Duncan's new multiple range test and multiple regression analysis showed that the net photosynthetic rate of the windward specialists was higher than the generalists whether in monsoon or in non-monsoon season. The net photosynthetic rate of Gordonia axillaris was higher in monsoon season than in non-monsoon season and it was the highest among these four species during monsoon season. However, the predawn and midday leaf water potential of Pasania formosana is lowest both in monsoon season and non-monsoon season. For transpiration Illicium arborescens was lowest all the time, but it could maintain a higher water-use efficiency than other study species such as Gordonia axillaris. The water-use efficiency of Daphniphyllum glauescens was the lowest and the transpiration the highest among the study species. During the measure of diurnal course of physiological activities, the phenomenon of midday depression of photosynthesis did not occur in Daphniphyllum glauescens.
The stomatal conductance was higher during monsoon season than non-monsoon season in Illicium arborescens, and was lower during non-monsoon than monsoon season in Gordonia axillaris. The stomatal conductance was not significantly different between monsoon and non-monsoon seasons in these species except Illicium arborescens. There was a higher net photosynthetic potential for Gordonia axillaris.
The physiological activities were different among the four species. The net productivities of Gordonia axillaris and Pasania formosana were higher than other species. The water-use efficiency of Illicium arborescens was the highest among the study species. The phenomenon of midday depression of photosynthesis was not found in Daphniphyllum glauescens. Although different distribution pattern occurring among the four species, we suggest that all of them can adapt well to the windy environment of Nanjenshan.