Wind Effects on Stomatal Conductance and Leaf Temperature of Tree Seedlings Distributed in Various Habitats of the Nanjenshan Forest, Southern Taiwan

風對南仁山森林不同生育地分布型樹種苗木氣孔導度與葉溫的影響

郭耀綸(Yau-Lun Kuo) ； 李彥屏(Yan-Ping Lee) ； 楊月玲(Yeh-Lin Yang)

《台灣林業科學》 26卷1期 (2011/03) Pp. 1-16

https://doi.org/10.7075/TJFS.201103.0001

摘要

台灣南部的南仁山森林，每年遭受東北季風的擾動長達半年，但風的作用對當地林木葉片的氣孔活動有何影響，目前所知仍少。本研究選定南仁山森林迎風坡樹種、背風坡樹種，以及兩處共有的廣泛分布樹種共8種的樹苗，於進入式生長箱內在風速1~4ms^(-1)的處理下，測定各樹種葉片氣孔導度的變化。結果發現在風速及2ms^(-1)的處理下，18樹種的氣孔導度即分別有9及17樹種顯著低於未吹風時。在3及4ms^(-1)風速處理下，迎風坡樹種氣孔導度降低程度均顯著小於另二類樹種，背風坡樹種在風速4ms^(-1)時，氣孔導度的下降率平均達43%，廣泛分布樹種為34%，而迎風坡樹種僅27%。背風坡樹種氣孔導度下降率與風速直線迴歸的斜率，也顯著較迎風坡樹種陡。另將各供試樹苗在風速6ms^(-1)下處理10分鐘，發現迎風坡樹種葉溫平均下降3.4℃，而背風坡樹種葉溫下降達4.8℃，二者具顯著差異。本研究也發現比葉重較大或單葉面積較小的樹種，因風吹致葉溫及氣孔導度下降的程度均較小。迎風坡樹種相較於背風坡樹種，兼有較小的葉面積與較大的比葉重，在吹風條件下氣孔導度與葉溫並不會大幅度減小。迎風樹種葉片具備上述形態與生理性狀，顯示已適應南仁山森林長期慢性的東北季風逆境。

關鍵字

葉面積 ； 背風樹種 ； 風速 ； 東北季風 ； 迎風樹種

並列摘要

Forests of Nanjenshan, located in southern Taiwan, are chronically disturbed by strong winds of the northeasterly monsoon for as long as 6 mo each year. However, not much is known about the effects of wind on stomatal activities of trees that are found there. This research chose seedlings of 18 species representing tree species either growing specifically at a windward site, a leeward site, or ubiquitously at both sites. We measured variations in stomatal conductance of these species in a walk-in growth chamber, where the wind speeds were adjusted to 1~4 m s^(-1). Results showed that at wind speeds of 1 and 2 m s^(-1), 9 and 17 species, respectively, of the 18 tested species showed significantly lower stomatal conductance than that of the control. Under wind speeds of 3 and 4 m s^(-1), reductions in the stomatal conductance of windward species were significantly less than those of species from the other 2 habitat types. At a wind speed of 4 m s^(-1), stomatal conductance of leeward species and ubiquitous species had decreased 43 and 34%, respectively, but had only decreased by 27% in windward species. The slope obtained from a linear regression analysis of variation in the percentages of stomatal conductance vs. increasing wind speeds of each species was also significantly steeper in leeward species than in windward species. In another experiment, we exposed seedlings of all 18 tested species to a wind speed of 6 m s^(-1) for 10 min and monitored variations in leaf temperatures. The leaf temperature of windward species decreased 3.4℃ on average, while it decreased 4.8℃ (significantly differing from the former) in leeward species. Species with a larger leaf mass per unit area or smaller leaf area were less affected by wind, in terms of both lowered leaf temperatures and decreased stomatal conductance. Windward species of the Nanjenshan forest, in contrast to leeward species, had larger leaf masses per unit area and smaller leaf areas; they did not exhibit substantial reductions in stomatal conductance or leaf temperatures under windy conditions. Possessing the aforementioned morphological and physiological characteristics, the windward species of the Nanjenshan forest clearly have adapted to the chronic wind stress of the northeasterly monsoon.

並列關鍵字

leaf area ； leeward species ； northeasterly monsoon ； wind speed ； windward species