水生植物抗流機制之研究

A Study of Flow Resistance and Adaptation of Aquatic Macrophytes

陳湘媛(Shiang-Yuarn Chen)

指導教授 ： 林鎮洋

國立臺北科技大學/工程學院/工程科技研究所/博士(2010年)

https://doi.org/10.6841/NTUT.2010.00151

摘要

近年來，許多關於生態工程之研究在學界與工程界積極展開，然而研究重點多在河川護岸之型式、材質、工法，並以植栽之存活比率、綠覆速度做為適生植物種類之指標，對於曠日廢時的監測或實證研究較為少見，亦少有從植物之抗流能力（flow resistance）出發，針對植生對不同流速產生之抗流機制之探討，或者關於植生對不同流速之河床結構之適應性的實驗。本研究係從模擬之水工模型出發，探究水生植物對於不同流速之水道，在抗流力方面會產生如何之變化，並就植被之生長速率、莖葉組織強度的變化、抗流之耐度極限、抗沖刷反應等加以分析，期能找出植物面對不同流速時在生理上的反應機制。
根據研究結果，發現水生植物因應不同流速，確實在植物生理上產生不同的反應機制，以水芹菜為例，在面對較高流速沖刷時，其生長速度趨緩，莖芽組織變得矮小且柔軟，以增加植物的抗流彈性。此外，其平均根長變短，錨定能力降低，其地上莖葉與地下根系的生物量均受到流速之抑制，研究同時發現水生環境中生長的水芹菜其斷面的平均維管束數量雖然要較陸生者為低，然而實際上平均斷面之單位面積的維管束數量卻隨流速增加而提高，使水芹菜面臨高流速環境時能夠以降低表面積卻增加維管束密度的方式避免外力的傷害。研究過程中，植栽槽會出現自生性藻膜，其組成包括念珠藻、顫藻與舟型藻等，而水芹菜則提供藻膜附著的機會，使藻類較不易被水流沖走，可有效降低細粒坋土之沖刷，對表層土壤形成保護的作用。本研究成果除可進一步確認適性植生種類或先驅植物種外，亦可瞭解植物在生態工程上可扮演的角色與極限，未來可做為河道植生工程之設計依據。鑑於適性植物種類可能是多元化的組成，因此未來的實驗可進一步針對植生之配置模式，探討其面對不同流速之抗流機制變化，甚至嘗試以其他植栽物種為實驗材料，重覆實驗以比較是否在抗流機制上呈現種間差異。

關鍵字

抗流機制 ； 模擬水道 ； 水生植物 ； 生態工程

並列摘要

In recent years, ecological engineering has been widely studied in both theoretical academia and practical engineering fields. However, most studies stressed the types, materials and construction approaches of riverbank protection works, or the survival ratio of certain vegetation. There has been relatively little field evidences to verify the mitigation approaches and specifically on the effects of vegetation on channel and flow resistance mechanisms. The present study is carried out in a simulated channel. The aims are, firstly, to examine how aquatic macrophytes respond to different channel flow velocities in terms of changes in their flow resistance mechanisms; next, to examine the growth rate of the macrophytes, the growth rate and shape of macrophyte shoots, tissue strength of the shoots and roots, tolerance of plants, and erosion-resisting response to various velocities; finally, to clarify the physical reactive mechanism of the aquatic macrophytes when facing the different velocities.
Experimental results showed that Oenanthe javanica DC. (water celery) presented morphological variations at different flow velocities. In particular, the growth rate became slow and plant shoots were shorter and softer to increase plant flexibility as flow velocities increased. Root length and root anchorage decreased. Root, stem, and shoot mass were also found to be restricted to flow velocity. Study results also show that the number of vascular bundles in new shoots decreased in flowing water environments compared to terraneous planting environments. Actually, the average number of vascular bundles per square mm increased as flow velocity increased to provide compensating structural support mechanisms. By the way, the algal mats would form in the planters automatically, including Anabaena azollae, Oscillatoria, and Navicula sp. These algal mats played a topsoil protection role especially for the silt. This research is anticipated to verify the suitable planting materials or precursors for the riverbanks and, additionally, to clarify the roles and limitations of applying aquatic macrophytes in ecological engineering. Since suitable streambank vegetation may include a variety of several different plants, useful future studies could examine the flow-resistance mechanisms of clusters of water celery and other selected plants. Through repeated experiments, the existence and level of interspecific difference will be also examined.

並列關鍵字

flow resistance mechanism ； simulated channel ； aquatic macrophytes ； ecological engineering.

參考文獻

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