紫芋蘭生育地干擾因子與生理特性之研究

Study of physiological characteristics and habitat disturbance of Eulophia dentate

紫芋蘭 (Eulophia dentate Ames) 為臺灣特有種植物，僅分布於3-4 個分布地，族群數量約50-250 株，對其物候、生長環境及生態生理特性均不甚了解，其重要生育地苗栗縣卓蘭地區大峽谷因火燒及淹水等原因遭到破壞，導致族群銳減，列為嚴重瀕臨絕滅植物，亟需保育及研究。本研究調查紫芋蘭生育地植群結構，可知外來入侵種銀合歡 (Leucaena leucocephala) 及大花咸豐草 (Bidens alba) 的生長強勢，能覆蓋生育地，取代原生之紫芋蘭、臺灣白及 (Bletilla formosana) 和甜根子草 (Saccharum spontaneum)，可能會成為改變植群結構之重要因子。透過非破壞性之葉綠素螢光及氣體交換之量測，可知紫芋蘭為自營性生物，適合光度範圍為1,200-1,500 μmol photon m-2 s-1，屬於偏陽性植物，對生育地環境的需求為適宜的開闊度，易受生長勢強之入侵植物遮蔽覆蓋而消失，且遇淹水逆境其假球莖及根系易腐爛，顯示紫芋蘭的脆弱性，研究之結果可供紫芋蘭復育工作之參考。

Eulophia dentata Ames is a native plant endemic to Taiwan. It is only found in three to four areas in the past 80 years, each with a population of 50-250 plants. The phenology, growth environment, and ecological and physiological characteristics of E. dentata are not well documented. The habitat in Grand Canyon in the Zhuolan area of Miaoli County was destroyed by fire and flood, resulting in a sharp decline in the ethnic groups. Conservation and research are urgently needed. In this study, we investigated the vegetation structure of E. dentate habitat. The invasive species Leucaena leucocephala and Bidens alba have been growing rampantly and showing superiority in the habitat. They are replacing the native E. dentata, Bletilla formosana, and Saccharum spontaneum, which might lead to change in the vegetation structure. Through the measurement of non-destructive chlorophyll fluorescence and gas exchange, we found that E. dentata is a self-supporting organism, and its suitable luminosity range is 1,200-1,500 μmol photon m-2 s-1. Therefore, it is prone to be covered by invasive plants with strong growth potential, and its pseudobulb and root system can easily rot under flooding, showing its fragility. The results of this study can be used for restoration of E. dentate in the future.