Ecophysiological Characteristics of Three ＂Cyathea＂ Species in Northeastern Taiwan

樹蕨為亞熱帶及熱帶雨林中顯著物種，一些近緣樹蕨常在森林中共存，然而，其共存機制鮮為瞭解。本研究調查生長在台灣東北部森林筆筒樹、台灣桫欏與鬼桫欏三種樹蕨生態生理特性。結果顯示筆筒樹偏好生長於開闊生育地（平均樹冠開闊度29.2%），而台灣桫欏與鬼桫欏則偏好生長於鬱閉生育地（平均樹冠開闊度分別為7.0及5.0%）。筆筒樹光飽和光合作用速率顯著高於鬼桫欏，台灣桫欏居中（筆筒樹、台灣桫欏及鬼桫欏分別為11.46, 8.27及6.34 μmol CO_2 m^(-2) s^(-1)）；鬼桫欏光飽和點顯著低於其它兩物種（筆筒樹、台灣桫欏及鬼桫欏分別為1220, 1100及808 μmol photon m^(-2) s^(-1)）；筆筒樹的光補償點與暗呼吸率顯著高於台灣桫欏及鬼桫欏。另外，此三種物種以筆筒樹具最短之葉片壽命（孕性葉6.6月，營養葉7.2月），台灣桫欏其次（孕性葉7.2月，營養葉7.3月），鬼桫欏之葉片壽命則為最長（孕性葉13.0月，營養葉12.0月）。根據它們的棲地偏好及生態生理特性，筆筒樹、台灣桫欏及鬼桫欏分別屬於非耐陰性物種、中度耐陰性物種及耐陰性物種。道路及步道、頻繁颱風干擾和偶發性樹倒創造出不同樹冠開闊度棲地，提昇這三種桫欏屬植物共存在此一森林中的機會。

關鍵字

樹冠開闊度；筆筒樹；鬼桫欏；台灣桫欏；葉片壽命

並列摘要

Tree ferns are conspicuous in subtropical and tropical rainforests. Some closely related species of tree ferns often coexist in the forest; however, the mechanisms are poorly understood. The ecophysiological characteristics of 3 tree ferns, ＂Cyathea lepifera＂, ＂C. spinulosa＂, and ＂C. podophylla＂, growing in forests of northeastern Taiwan were investigated. Results showed that ＂C. lepifera＂ preferred an open habitat (mean canopy openness (MCO) of 29.2%), while ＂C. spinulosa＂ and ＂C. podophylla＂ preferred a shaded habitat (MCOs of 7.0 and 5.0%, respectively). The light-saturated photosynthetic rate of ＂C. lepifera＂ was significantly higher than that of ＂C. podophylla＂, and ＂C. spinulosa＂ had a medium one (11.46, 8.27, and 6.34 μmol CO_2 m^(-2) s^(-1) for ＂C. lepifera＂, ＂C. spinulosa＂, and ＂C. podophylla＂, respectively). The light saturation point of ＂C. podophylla＂ was significantly lower than those of the other 2 species (1220, 1100, and 808 μmol photon m^(-2) s^(-1) for ＂C. lepifera＂, ＂C. spinulosa＂, and ＂C. podophylla＂, respectively). The light compensation point (LCP) and dark respiration rate (Rd) of ＂C. lepifera＂ were significantly higher than those of ＂C. spinulosa＂ and ＂C. podophylla＂. ＂Cyathea lepifera＂ had the shortest frond life spans (6.6 mo for fertile fronds and 7.2 mo for sterile fronds) among the 3 species, which was followed by those of ＂C. spinulosa＂ (7.2 mo for fertile fronds and 7.3 mo for sterile fronds), and the longest frond life spans were in ＂C. podophylla＂ (13.0 mo for fertile fronds and 12.0 months for sterile fronds). ＂Cyathea lepifera＂, ＂C. spinulosa＂, and ＂C. podophylla＂ respectively belonged to shade-intolerant species, mid-shade-tolerant species, and shade-tolerant species as inferred from their habitat preference and ecophysiological characteristics. Roads, trails, frequent typhoons, and occasional tree falls create habitats with different canopy openness levels which increase the opportunity of these 3 ＂Cyathea＂ species to coexist in this forest.

並列關鍵字

canopy openness ； Cyathea lepifera ； Cyathea podophylla ； Cyathea spinulosa ； frond life span

國際替代計量

Ecophysiological Characteristics of Three ＂Cyathea＂ Species in Northeastern Taiwan

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