墾丁高位珊瑚礁樹種適應水逆境之研究

Water stress adaptation of tree species at the Kenting Uplifeed Coral Reef forests

蔡國鐘(Kuo-Chung Tsai)

指導教授 ： 郭耀綸

國立屏東科技大學/農學院/森林系所/碩士(2011年)

https://doi.org/10.6346/NPUST.2011.00015

摘要

墾丁高位珊瑚礁自然保留區內的礁頂及谷地兩類生育地，受東北季風影響程度不同，在地形、微環境及樹種組成均有很大的差異。本研究目的為了瞭解此兩類生育地樹種在生理及葉片結構等功能性狀上的差異
。供試樹種包括生育在礁頂的鐵色及紅柴，生育在谷地的皮孫木及蟲屎，以及兩生育地共有的黃心柿。於2009年12月開始在礁頂與谷地環境分別架設風速計及溫度計，測量兩地氣候因子的差異。在2010年乾季及雨季分別測定各樹種的黎明前水勢及光合作用潛力，並測定各樹種的葉厚度、葉面積、比葉重、葉片耐脫水能力等葉部性狀。在生理方面，生長在礁頂的兩樹種，在2010 年4月及5月乾季時，黎明前水勢平均為-3.5 MPa，顯著低於谷地樹種的-0.8 MPa，顯示礁頂植物在乾季時水逆境程度較谷地樹種大。礁頂樹種光合作用率在乾季時為1.5~5.5 µmol m-2 s-1，谷地樹種則可達9.0~12.0 µmol m-2 s-1；雨季時谷地樹種光合作用率平均為13.5 µmol m-2 s-1，與乾季時(10.5 µmol m-2 s-1)差異不大，相反的，礁頂樹種雨季時光合作用率為7.6 µmol m-2 s-1顯著大於乾季時的2.6 µmol m-2 s-1。兩地共有的黃心柿，生長在谷地的植株在乾雨季時光合作用皆顯著高於礁頂的同種植株。在葉片耐脫水能力方面，於乾燥條件下，礁頂樹種葉片比谷地樹種有較輕微的細胞損傷指數，顯示前者具有較高的耐脫
水能力。礁頂及谷地兩處黃心柿的植株，其耐脫水能力並無顯著差異。上述結果顯示，生長在礁頂的樹種紅柴及鐵色在乾季遭遇到水逆境時光合作用會受抑制，但仍能在極低的葉部水勢下(-3.5 MPa)，維持正值的光合作用(2.6 µmol m-2 s-1)。在葉部功能性狀方面，生長在礁頂的兩樹種，其比葉重顯著大於谷地樹種皮孫木及蟲屎。生長於礁頂及谷地的黃心柿植株，其葉片面積並無顯著差異，但比葉重及葉厚度均以礁頂植株顯著較大。生育在礁頂的樹種具有較大的葉厚度、比葉重及耐脫水能力，應為適應墾丁高位珊瑚礁礁頂，具強風及乾旱逆境環境的重要功能。

關鍵字

東北季風 ； 光合作用率 ； 比葉重 ； 水逆境 ； 耐脫水

並列摘要

There are two types of habitats, reef-top and valley, at the Kenting Elevated Coral-reef Natural Reserve, distinctly differ due to the differential impacts of wind stress produced by the northeasterly monsoon. These two habitats differ greatly in the topography, micro-environment, and species composition of forest community. This research investigated the differences in functional traits, including physiology and structure, in leaves of species growing at these two habitats. Five species were chosen for our investigation, including Drypetes littoralis and Aglaia formosana (at the reef-top), Pisonia umbellifera and Melanolepis multiglandulosa (at the valley), as well as Diospyros maritime (ubiquitous at both habitats). In December 2009, we placed an anemometer and a thermograph in the reef-top and valley. We measured predawn leaf water potential and photosynthetic capacity of each species during dry and rainy seasons respectively. In addition, functional traits such as leaf thickness, leaf area, leaf mass per area, and dehydration tolerance of each species were also measured. In the aspect of physiological
activities, two species growing at the reef-top, in April and May 2010 dry seasons, the mean predawn leaf water potential at -3.5 MPa, which was significantly less than that in the valley species -0.8 MPa. Average photosynthetic capacity for species at the reef-top was 1.5-5.5 µmol m-2 s-1, while it could reach 9.0-12.0 µmol m-2 s-1 for species at the valley in dry season. In rainy season, average photosynthetic capacity for species at the valley was 13.5 µmol m-2 s-1, which was not very different from that in the dry season(10.5 µmol m-2 s-1). On the contrary, average photosynthetic capacity for species at the reef-top was 7.6 µmol m-2 s-1, which was significantly more than that in the dry season(2.6 µmol m-2 s-1). Seedlings of the ubiquitous species, D. maritime, showed significantly lower physiological performance when growing at the reef-top than those growing at the valley during dry season, but showed no significant difference during rainy season. When subjected to water stress, leaves of the reef-top species exhibited lower injury indices than leaves of the valley species, indicating that the reef-top species had higher dehydration tolerance. These results indicated that seedlings growing at the reef-top experienced water stress during dry season and thus their physiological activities would be inhibited. They would have to endure the stress to survive in that environment. In the aspect of functional traits, leaf thickness and leaf mass per area in Pisonia umbellifera and Melanolepis multiglandulosa at the reef-top were significantly larger than those growing at the valley. The D. maritime growth for in reef-top and valley, leaf area has no significantly in reef-top and valley, but the leaf mass per area and leaf thickness, reef-top which was significantly more than that valley. It indicated that larger leaf thickness, leaf mass per area, and dehydration tolerance are key functional traits for species to cope with the windy and dry environments on reef-top habitats.

並列關鍵字

northeast monsoon ； photosynthetic rates ； leaf mass per area ； water stress ； higher dehydration tolerance

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