臺灣東北部三種桫欏科樹蕨之物候表現

Abstract

本文針對臺灣東北部地區亞熱帶闊葉林之筆筒樹、臺灣桫欏、鬼桫欏三種桫欏科樹蕨樹蕨類植物之物候表現與葉片壽命進行研究，物候自2011年4月至2013年3月，逐月進行調查。調查發現筆筒樹、臺灣桫欏、鬼桫欏各主要分別生長於開闊地、林緣及森林內部。三種樹蕨物候調查項目包含葉片抽芽、展葉、凋萎，與孢子成熟和釋放，約有一半的物種物候表現具中度以上(r > 0.4) 的季節性表現強度，各種物候季節性之強度，因物種而異，三種樹蕨中，筆筒樹營養葉抽芽之季節性最為強烈，而台灣桫欏及鬼桫欏孢子成熟之季節性較為強烈。各物候因子與環境因子(如月平均溫度、降水量、幅射)之間具顯著相關性。三種樹蕨孢子葉主要集中於寒冷低日照的月份(2-4月)抽芽，營養葉則集中於溫暖、強日照且降雨量高峰月份(7-10月)抽芽，孢子成熟釋放主要在7-9月份發生。各樹蕨之孢子葉與營養葉壽命相同，但筆筒樹與臺灣桫欏之葉片壽命較鬼桫欏短(6-7個月vs. 15個月)，葉片壽命與葉片碳 / 氮比呈正相關。本研究證實不同微生育地之樹蕨具有不同強度的季節性表現及葉片壽命。

To clarify the phenology patterns and the physiological mechanisms of tree ferns, the phenology, including frond emergence, expansion, maturation, spore maturation and release, and senescence of three tree fern species, Cyathea lepifera, C. spinulosa, C. podophylla, which can be found in open site, edge of forest, and interior forest, respectively, in a subtropical broadleaf forest in northeastern Taiwan, was monitored monthly from April 2011 to March 2013. In these three tree ferns, more than 50 % of the monitored phenological events had the considerable seasonality. The variations in the intensity of the seasonality depended on the species. In C. lepifera, the seasonality of emergence in sterile fronds is the strongest, while in C. spinulosa and C. podophylla, the seasonality of spore maturation are the strongest. The phenological expressions have significant correlations with the environmental factors. Most fertile fronds emerged in cooler months with lower radiation (February-April), whereas most sterile fronds emerged in warmer months with higher radiation and precipitation (July-October). Spore maturation and release mainly from July to September. Cyathe lepifera and C. spinulosa had shorter life span comparing to C. podophylla (6-7 mo vs. 15 mo). We also found that frond C : N ratio were positively correlated with frond life span among species. C. podophylla, with the longest frond life span, had the highest frond C : N ratio (22.17 ± 1.95), followed by C. spinulosa (18.58 ± 1.37) and C. lepifera (18.68 ± 2.63). This study confirmed that tree ferns growing in different microhabitats have distinct intensities of seasonal phenological patterns and frond life span.