南仁山亞熱帶雨林四種優勢種林木生態生理學研究

Abstract

位於屏東縣滿州鄉欖仁溪上源的南仁山三公頃永久樣區，全年氣候可明顯分為兩個季節。十月至翌年三月之冬季受東北季風吹拂，寒冷低溫，並有短暫乾旱發生，是屬於南仁山的風季。其餘月份高溫多雨，則為非風季。本研究目的在探討南仁山區不同種植物之間生理特性的差異，及其在不同季節的生理反應。 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。 所有實驗數據經由鄧肯新多變域分析。結果發現，無論在風季或非風季期間，迎風坡分佈種的淨光合作用率皆高於廣泛分佈種。大頭茶在風季時淨光合作用率較非風季高，是四種樹種中最高的。台灣柯的黎明前與中午的葉片水勢，無論在風季或非風季皆低於其他樹種。紅花八角的蒸散作用率低於其他三種樹種，但紅花八角和大頭茶一樣，皆能維持較其他二種樹種為高的用水效率。奧氏虎皮楠的用水效率最低，蒸散作用卻比其他樹種高，但在幾個日變化測定日當中，皆未發生強光造成的午休現象。在四種樹種中，除了紅花八角風季時氣孔導度會增加之外，其餘三種樹種氣孔導度並不因季節不同而有所改變，大頭茶則具有相當高的光合作用潛力。 四種樹種的生理特性各有不同，淨光合作用生產力以大頭茶和台灣柯最高，紅花八角有較高的用水效率，奧氏虎皮楠淨光合作用不易遭受到因強光引起的午休現象。雖然四種樹種的分佈優勢度不同，但都可以適應生長於南仁山區受東北季風強烈影響的環境中。

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.