• 作者： 周昌弘; 侯美慧
• 作者服務機構： 中央研究院植物研究所
• 中文摘要： 在本省山坡地1500公尺以下常長有天然及人工竹林，且經常可以發現竹林內之地被植物密度小，雜草不易生長於林內。一般人咸認為此現象乃是竹林之遮蔭效果，或養分之競爭所致。作者在臺大溪頭實驗林區選了兩個人工林即柳杉林及孟宗竹林以比較其植生分佈，其結果顯示柳杉林內之地被植物密度四倍高於孟宗竹林者。然而，孟宗竹林內之光線強度，土壤有機質含量，土壤含水量及土壤陽離子的含量均顯著高於柳杉林者。此顯示孟宗竹林或其他竹林內之地被植物密度小並非由於上述物理因子之競爭，而可能由於植物相剋作用（allelopathy）所致。作者在溪頭實驗林區內選擇十四種竹類植物，以比較竹葉中水溶萃取液之植物毒性程度，其結果顯示麻竹之植物毒性最高，其次為綠竹，八芝蘭竹，孟宗竹，佛竹，及桂竹。從上述十四種竹林之土壤所萃得的水溶萃取液做生物分析，所得植物毒性之程度與竹葉者相似。從性葉中所分離出的植物毒性物質包括一些酚酸化合物及類黃素（flavonoids）。其中酚酸化合物已被鑑定的有o-hydroxyphenylacetic,p-coumaric, p-hydroxybenzoic, ferulic, vanillic,及syringic acids。除了類黃素外，其餘之酚酸亦被發現於竹林之土壤中。酚酸之濃度隨植物品種及土壤而異。以目前的結果尚難肯定植物毒性與上述酚酸之含量呈正相關關係，此可能是酚酸之濃度及其他尚未被鑑定之植物毒物質所致。
• 英文摘要： A unique pattern of weed exclusion by bamboo vegetation is often found on many hillsides ofmountains at elavations below 1500m in Taiwan. The experimental field results showed that the density ofunderstory in a pure stand of Phyllostachys edulis (bamboo) was significantly lower than that of Cryp-tomeria japonica (conifer), although the total number of understory species was higher in the former thanin the latter. The light intensity, soil moisture, and soil nutrient contents were much in favor of the former,indicating that the low density of understory in the bamboo stands was not due to the competition forlight, nutrient, and soil moisture. Fourteen bamboo species were selected for evaluation of allelopathicpotential. The pH of aqueous extracts of bamboo leaves and their soils ranged from 5.1 to 8.3, and osmoticconcentrations of these extracts were below 23 milliosmols. At these ranges of pH and osmotic concentra-tion, the inhibition of plant growth by these extracts was not due to the effects of both. However, theextracts did exhibit significant phytotoxicity on seed germination and radicle growth of lettuce, rye grass,and rice plants, indicating that the inhibition was due to a phytotoxic effect. Among the 14 bamboospecies, Sinocalamus latiflorus showed the highest phytotoxicity, and Bambusa oldhami, B. pachinensis,B. ventricosa, Phyllostachys edulls, and P. makinoi revealed significant phytotoxicity upon the test plants.The aqueous extracts obtained from the associated bamboo soils also exhibited some inhibition which inmost extracts was correlated to that of leaf extracts. The allelopathic substances isolated from the bambooleaves and their soils were identified as phenolic acids, namely, o-hydroxyphenylacetic, p-coumaric, p-hydroxybenzoic, ferulic, vanillic, and syringic acids. Some unidentified flavonoids and others may alsocontribute to the allelopathic dominance of bamboo vegetation.
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