福山試驗林九種常見樹種的植食現象及葉部特性

Abstract

本研究主要目的在了解台灣森林生態系中的植食現象，研究區域位於宜蘭福山試驗林，屬於亞熱帶雨林氣候，我們選擇福山9個常見樹種(山龍眼、黃杞、白校欑、三斗石櫟、錐果櫟、長葉木薑子、紅楠、綠樟及山紅柿)，實驗從2005年3月24日開始，至2006年1月16日為止，實驗期間共採集植物樣本8次。本研究觀察7種葉片受害型式(咀嚼式、骨骼化、潛葉、蟲癭、捲葉、刺吸式及撕裂)中以葉片遭受咀嚼式型式的受害頻度最高，顯示森林內的各種植食動物中，應以咀嚼式口器昆蟲的數量佔有較高比例；本研究以葉面積損失量來量化福山地區主要樹種植食程度，植食程度在種間及月份間具有顯著差異，各樹種8月至11月葉面積損失平均值由高至低分別為黃杞(14.52 %)、山龍眼(11.56 %)、三斗石櫟(10.86 %)、白校欑(7.60 %)、長葉木薑子(6.77 %)、錐果櫟(6.77 %)、紅楠(6.00 %)、山紅柿(5.72 %)及綠樟(3.81 %)，綜合整理9個樹種葉面積損失比率後得出福山試驗林2005年因植食行為造成的年葉面積損失為8.18 %，此外各樹種葉面積損失大部分出現在幼葉階段；本研究分析5個主要影響植食性動物取食行為的葉部特性(葉硬度、全酚類化合物、縮聚單寧、葉部氮及磷)，結果發現5個葉部特性在樹種間均有顯著差異，其中以綠樟與黃杞的植食程度較符合前人研究中對葉部特性所預測出的結果，植食程度最低的綠樟葉硬度較高、全酚類化合物及縮聚單寧的含量較多、氮與磷濃度較低，而植食程度最高的黃杞葉硬度較低、全酚類化合物及縮聚單寧的含量較少、氮與磷濃度較高；5個葉部特性在月份間均有顯著差異，各樹種的葉硬度、全酚類化合物與縮聚單寧會在幼葉最低，之後隨著葉齡增加而上升，葉部氮與磷濃度則隨葉齡增加而逐漸降低，這可以解釋為什麼幼葉的植食程度高於成熟葉；各樹種植食程度與幼葉及成熟葉葉部特性間相關分析中，葉硬度與氮濃度呈現顯著相關，顯示葉硬度與氮濃度對植食程度而言最具有指標性。

This study investigated herbivory in the subtropical forest of Fushan experimental forest, northeastern of Taiwan. Nine common species of Fushan were selected in this study, including Helicia formosana, Engelhardia roxburghiana, Castanopsis cuspidata var. carlesii f. sessilis, Pasania hancei var. ternaticupula f. ternaticupula, Cyclobalanopsis longinux var. longinux, Litsea acuminate, Machilus thunbergii, Meliosma squamulata, and Diospyros morrisiana. Leaves were sampled on eight sampling dates from 24 March, 2005 to 16 January, 2006. Seven types of leaf damages were examined on each leaf, including chew, skeletonize, mine, insect gall, roll, suck and laceration. Among seven types of leaf damages, chewing occurred most frequently on leaves. In addition, the leaf area loss was used as an index to evaluate the level of herbivory. Leaf area loss differed significantly among species and sampling dates. The leaf area loss of mature leaves, average from Aug11, Sep13 and Nov06, was 14.52 % for E. roxburghiana, H. formosana (11.56 %), P. hancei var. ternaticupula f. ternaticupula (10.86 %), C. s cuspidata var. carlesii f. sessilis (7.60 %), L. acuminate (6.77 %), C. longinux var. longinux (6.77 %), M. thunbergii (6.00 %), D. morrisiana (5.72 %), and M. squamulata (3.81 %). From nine species, the leaf area loss averaged 8.21 %. For all nine species, leaf area loss occurred mostly before leaves matured. All five leaf traits differed significantly among species. Herbivory rate of M. squamulata and E. roxburghiana were more consistent with the palatability predicted by leaf traits. With the lowest leaf area loss, M. squamulata had higher leaf toughness, total phenol and condense tannin, and lower N and P concentration. By contrast, with the highest leaf area loss, E. roxburghiana had lower leaf toughness, total phenol and condense tannin, and higher N and P concentration. Leaf toughness, total phenol and condense tannin were usually lower in young leaves, and then increased rapidly afterwards. By contrast, the foliar concentrations of N and P decreased in aging leaves. Due to their higher palatability, young leaves suffered higher loss of leaf area. The leaf area loss of nine species was significantly correlated with leaf toughness and nitrogen concentration, suggesting that toughness and nitrogen concentration were the better indicators of herbivory.