外來入侵種長穗木之個體生態學性狀及相剋作用潛力

Autecological Characteristics and Allelopathic Potential of the Invasive Species Stachytarpheta jamaicensis

郭耀綸(Yau-Lun Kuo)

《台灣林業科學》 16卷2期 (2001/06) Pp. 103-114

https://doi.org/10.7075/TJFS.200106.0103

摘要

長穗木是一種具侵凌性的外來植物，普遍入侵台灣南部地區。本研究探討此入侵種之個體生態學性狀及相剋潛能，藉此了解其入侵機制。本植物在無環境壓力下全年均可開花，一個植株平均可長出35個穗狀花序，因此在一個生長季即可生產一萬粒以上的種子。本值物莖部具有無性繁殖能力，植株耐淹性也很高。長穗木為非耐蔭種，在高光量下有較高之生物量，植株在相對光量50%以下花序數目顯著降低，花序形成時問也延後。種子在黑暗條件可發芽，但有光照時發芽率較高，達70%以上。長穗木在低光或高光條件下均有很高的光合作用率，未顯示光飽和現象，最大光合作用率可達26μmolm^(-2)s^(-1)以上，顯示長穗木有很高的初級生產力。本植物葉部水萃取液具有相剋作用，可抑制多種草本植物種子發芽及胚根生長。盆栽試驗顯示分解中的葉子也具植物相剋作用。推測長穗木強烈侵凌性之可能原因包括，(1)生產大量易風力傳播的種子；(2)莖部可萌蘗更新；(3)可產生具植物相剋作用及忌避啃食的化學成分；(4)初級生產力很高。文中對恆春半島乾旱生育地常見的相思樹、蒲姜、銀合歡及長穗木彼此間的相剋作用關係也加以討論。

關鍵字

相剋作用 ； 個體生態學 ； 入侵種 ； 光合作用率 ； 長穗木

並列摘要

Stachytarpheta jamaicensis, an introduced aggressive species, has invaded much of the southern part of Taiwan. To elucidate its invasive mechanisms, the autecological characteristics and allelopathic potential of this species were investigated. Each plant may have 35 spikes which flower for most of the year under favorable conditions. Therefore, a single plant may produce over 10,000 seeds in 1 growing season. In addition, it has the ability to reproduce by vegetative means and can withstand flooding. This plant is a shade-intolerant species. Biomass production was significantly higher under high light conditions. Under low light, the number of spikes was significantly reduced, and the time to spike formation was postponed. Although its seeds could germinate under dark conditions, the germination rates, when illuminated, increased to more than 70%. S. jamaicensis had remarkably high photosynthetic rates under both strong and low light conditions. Its photosynthetic rates were not light saturated, and its photosynthetic capacity was higher than 26 μmol m^(-2) s^(-1), indicating that it has a high primary production capacity. Aqueous leaf extracts of S. jamaicensis inhibited seed germination and radicle growth of many local herbaceous plants, implying it has allelopathic potential. Allelopathic activities were also observed in pot experiments using decaying leaves. The following ecological characteristics of S. jamaicensis may be suggested as reasons for its success as an aggressively invasive species: (1) prolific seed production and easy dispersal of seeds by wind; (2) ability of vegetative regeneration by stems; (3) production of allelopathic and repellent substances; and (4) a high primary production rate. Allelopathic relationships among Acacia confusa, Vitex negundo, Leucaena leucocephala, and S. jamaicensis, which inhabit the same drough-prone site of the Hengchun Peninsula, are also discussed in this paper.

並列關鍵字

allelopathy ； autecology ； invader ； photosynthetic rate ； Stachytarpheta jamaicensis