恆春西海岸十樹種黎明前水勢與光合作用潛力在乾雨季間之比較

Comparison in Predawn Leaf Water Potential and Photosynthetic Capacity between Dry and Wet Season in Saplings of Ten Tree Species Inhabit at West Coast of Hengchun, Taiwan

楊雅萍(Ya-Ping Yang)

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.2011.00013

摘要

臺灣南部恆春地區每年11月至翌年5月中旬有長達半年之乾季。本研究比較該處天然更新之9種原生樹種稚樹，以及外來入侵種銀合歡，由乾季到雨季歷程的葉部黎明前水勢(PWP)及光合作用潛力(Acap)之變化，藉以瞭解不同樹種生理及形態上對長期缺水的反應。現地測定結果發現，在2009年12月至2010年5月乾季期間，臺灣海桐並未遭受水逆境，在此期間PWP僅比雨季降低-0.09 MPa；銀合歡與蟲屎在乾季之PWP只比雨季降低-0.47 MPa；在乾季時白樹仔、構樹、樹青及黃槿等4種樹種之PWP較雨季時降低-0.63至-0.89 MPa，而恆春厚殼樹、止宮樹及紅柴乾季的PWP則降低-1.35 MPa以上，在乾季時遭嚴重水逆境。供試樹種在乾季時的Acap均會顯著較雨季時低，臺灣海桐在乾季時Acap可維持雨季時的88%，銀合歡與黃槿可維持70%以上，蟲屎、恆春厚殼樹、構樹及止宮樹等4種樹種可維持60%以上，而樹青、白樹仔及紅柴乾季時的Acap只有雨季時的一半，生理受抑制較明顯。在乾季期間，恆春厚殼樹有部份葉片會枯黃掉落，構樹與止宮樹則超過半數的葉片會凋落，其餘7種則維持常綠。本研究發現臺灣海桐在乾季仍可維持與雨季類似的生理表現，而紅柴則呈現另一極端，生理活動在乾季時顯著降低。外來入侵種銀合歡砍伐後的萌蘖苗在乾季時仍能維持較高的水勢及光合作用潛力，顯現銀合歡萌蘖苗強勢的競爭能力。

關鍵字

乾季 ； 水逆境 ； 海岸林 ； 原生樹種 ； 外來種銀合歡

並列摘要

In Hengchun area of southern Taiwan, the dry season lasts from November of each year to mid May of the next year. This research compared the seasonal variations, from dry season to rainy season, of predawn water potential (PWP) and photosynthetic capacity (Acap) in ten tree species, including nine saplings of native tree species and one invasive species, Leucaena leucocephala. These results would provide information on the physiological and morphological responses to prolonged water deficiency of these tested species. Field measurements showed that sapling of Pittosporum pentandrum did not suffer water stress since its PWP during dry season (December 2009 to May 2010) was only -0.09 MPa less than during rainy season; PWP of L. leucocephala and Melanolepis multiglandulosa decreased only -0.47 MPa, while PWP of Gelonium aequoreum, Broussonetia papyrifera, Planchonella obovata, and Hibiscus tiliaceus decreased -0.63 to -0.89 MPa. On the other hand, PWP of Ehretia resinosa, Allophylus timorensis, and Aglaia formosana dropped at least -1.35 MPa, indicating that these species experienced severe water stress. All tested species showed significantly lower Acap in dry season than in rainy season. Comparing the measurements of Acap during dry season versus rainy season in each species, P. pentandrum could maintain at around 88%; L. leucocephala and M. multiglandulosa could maintain at above 70%; M. multiglandulosa, E. resinosa, B. papyrifera, and A. timorensis showed above 60%; yet Acap of P. obovata, G. aequoreum, and A. formosana in dry season had only half of their Acap in rainy season, showing that their physiological activities were obviously inhibited. During the dry season, some leaves in saplings of E. resinosa, and more than half of the leaves in saplings of B. papyrifera and A. timorensis, would turn yellow and fall, while the other 7 species remain green. Overall, P. pentandrum could still maintain similar physiological performances in dry season as compared to in rainy season, but A. formosana physiological activities was significantly decreased in dry season. The invasive species, L. leucocephala, maintained its water potential and photosynthetic capacity during dry season at relatively higher levels, exhibiting its strong competitive capability.

並列關鍵字

dry-season ； water stress ； coastal forests ； native trees ； exotic species Leucaena leucocephala

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