華江濕地小水鴨度冬棲地之適應性管理

Adaptive management on the wintering habitat of common teals (Anas crecca) in Hwajiang estuarine wetland

黃國文(Gwo-Wen Hwang)

指導教授 ： 李鴻源

國立臺灣大學/工學院/土木工程學研究所/博士(2012年)

https://doi.org/10.6342/NTU.2012.02443

摘要

本研究整合生態學與水利學觀點，以棲地適合度指標模式（HSI model）量化小水鴨喜好之度冬棲地條件，建置一套適用於感潮濕地之小水鴨度冬棲地適應性管理模式。華江濕地為東亞小水鴨重要度冬棲地之一，惟近年來受到自然營力及人為干擾，環境劇烈變遷。河床大幅回淤，植被面積也隨之快速擴增，使小水鴨喜好之灘地及水域面積大量減少。因此小水鴨度冬棲地復育及管理，為當前極為重要且迫切之課題。
本研究於2008年10月至2009年3月在華江濕地三個固定位置，進行22次小水鴨數量及棲息位置調查，共紀錄小水鴨3615隻次。同時調查高程、坡度及距植被最短距離等環境因子，以地理資訊系統記錄於5m×5m之數值地形網格。接著以單位努力收穫量的概念，繪製網格內單次調查小水鴨最大數量與環境因子關係之包絡線，作為各環境因子之適合度指標（SI）。以最小值法整合三個環境因子之適合度指標，建置棲地適合度指標（HSI）模式。分析結果顯示，小水鴨喜好低緩坡度、高低潮位間之高程及鄰近植被邊緣之棲地環境，其棲地之最適坡度介於0.7%至1.4%間，最適地表高程介於EL. 0.3m至EL. 0.7m間，最適距植被最短距離則為0 m至4m。另以網格內小水鴨最大數量與棲地適合度指標進行驗證，兩者成高度顯著相關，顯示本研究建立之小水鴨度冬棲地適合度指標模式具高度可靠性及實用性。本研究依據棲地適合度指標將本區之環境品質分為不良（0 -0.25）、普通（0.25-0.50）、良好（0.50-0.75）及最佳（0.75-1.0）等4個等級，最佳棲地的比例在新潮池、內河道及次潮溝分別為41.9%、17.4%及26.4%。
本研究以小水鴨度冬棲地適合度指標及量化之棲地特性研擬棲地復育原則，主要為坡度小於1.5%、高程於EL. 0.0m至EL. 0.5m間、在灘地營造潮池或潮溝，退潮時仍保有水域、距植被最短距離不超過25m、復育棲地寬度至少100m及長度至少250m、復育地點儘量於小水鴨主要棲息地附近，以增加適合棲地之連續性。規劃三個華江濕地復育方案，僅以復育地點為操縱變因，再以CCHE2D模式進行數值實驗，以分析不同復育地點之優劣。主要考量為造床流量條件下之減淤效益，模擬結果進一步計算水流底床剪應力分布，並假設水流底床剪應力愈大、淤積潛勢愈低、復育效果愈佳。分析結果顯示，位於華江濕地上游側之復育地點淤積趨勢相對較低，為較佳之復育地點。
本研究引用適應性管理之架構，以棲地適合度指標模式作為量化評估工具，建置華江濕地小水鴨度冬棲地適應性管理模式。此模式包括監測、評估及決策三部分，可作為華江濕地小水鴨度冬棲地復育及管理參考使用，並可供其他類似濕地之復育及永續管理參考。

關鍵字

感潮濕地 ； 小水鴨 ； 度冬 ； 棲地適合度指標 ； 復育 ； 適應性管理

並列摘要

This study aimed at constructing an adaptive management model for wintering habitat of Common Teal (Anas crecca) in Hwajiang Wetland. A habitat suitability index (HSI) was developed to quantify the physical environments of the Teals’ preferred habitat. The Hwajiang wetland is an important wintering site for migratory Common Teal, whose population has dramatically declined in recent years, due most likely to the persistent degradation of habitats in this wetland. Due to river morphology, the changes of sediment deposition and vegetation expansion, have reduced the available habitat for the wintering Teal. Therefore, the rehabilitation of the Teals’ habitat is urgently needed for a sustainable management in this wetland.
Point-count surveys of the Common Teal were conducted at a tidal pool, an inner channel and a tidal creek in Hwajiang Wetland and Teals’ positions were recorded from October 2008 to March 2009. Twenty-two sets of data and 3615 counted individuals were collected. Three habitat variables, including slope, elevation and the distance to the nearest vegetation, were displayed on 5 m × 5 m grid cells and analyzed with GIS software. Suitability index (SI) values of habitat variables were determined using the envelop curve of maximum abundance of common teals versus the habitat variables. The results showed that Common Teal preferred habitats with gentle slopes, median elevations and areas close to vegetation. The abundance of the Common Teal was highest in the grid cells with slopes ranging from 0.7 to 1.4%, bed elevation varying from 0.3 to 0.7 m above the mean sea level, and distance to the nearest vegetation shorter than 4 m. The HSI model was constructed by calculating the minimum value of the three SIs, and the suitability map of wintering common teals was generated to represent an integrated map of habitat quality in the area. A simple regression analysis indicated that the HSI model is a reliable indicator as the maximum numbers of the Common Teal in each grid cell increased significantly with the HSI values. Four types of habitat conditions, poor, fair, good and excellent, were determined based on the HSI values. The proportions of excellent habitat were 41.9%, 17.4% and 26.4% in the tidal pool, the inner channel and the tidal creek, respectively.
A principle of rehabilitation was derived from the HSI model, with slopes smaller than 1.5%, elevations between 0.0m and 0.5m, and distance of less 25 m to the nearest vegetation. The rehabilitation area should be larger than 100 m in width and 250 m in length and adjacent to the existing Teal habitat. Three rehabilitation scenarios were simulated and characterized based on field survey and the HSI model. In addition, a horizontal two dimension numerical model, CCHE2D, was employed to simulate bank-full flow characteristics such as water surface elevation, flow velocity, shear stress and so on. The bathymetry and vegetation cover were assumed the same while the location was different. The shear stress evaluation indicated that the rehabilitation of the most upstream location is the best scenario because it has the lowest sediment deposition rate and represents a minimum maintenance effort needed in the future.
This study provided a foundation for determining potential habitats and information on how to mitigate a degraded wetland for the Common Teal. It encompassed the aspects of monitoring, evaluation, and decision making that would benefit future management plans directed toward the Common Teal and other waterfowl species in Taiwan. It also provided an adaptive management model for application to similar projects of wetland rehabilitation and sustainable management.

並列關鍵字

Common Teal ； Wintering waterfowl ； Estuarine wetland ； Habitat suitability Index ； Rehabilitation ； Adaptive management

參考文獻

2. 方偉達、薛怡珍、何一先，2008，河川匯流處低水護岸之生態影響現象─以華江雁鴨自然公園為例，國立臺南大學「環境與生態學報」第1卷第2期，pp.1-16。

6. 施上粟，2005，潮間帶濕地生態水理模式建置及量化之研究，國立台灣大學土木系博士論文。

80. Larson, M.A., Dijak, W.D., Thompson, F.R.III, & Millspaugh, J.J., 2003, Landscape-level habitat suitability models for twelve species in southern Missouri, U.S. Department of Agriculture, Forest Service General Technical Report NC-233, North Central Research Station, St. Paul, Minnesota, USA.

33. Acuna R., Contreras, F., & Kerekes, J., 1994, Aquatic bird densities in two coastal lagoon systems in Chiapas State, Mexico, a preliminary assessment, Hydrobiologia, 279/280: 101–106.

34. Ariathurai, R., & Krone, R.B., 1976, Finite element model for cohesive sediment transport, Journal of the Hydraulics Division, ASCE, 102: 323-338.