營造都市生態溝為蛙類棲地－以臺北市永建生態園區為例

Abstract

都市發展改變原有地貌、破壞生物棲地，讓生物生存空間減少；為追求永續發展，都市環境的生物棲地營造逐漸受到重視。本研究選擇蛙類做為調查對象，以評估都市內棲地營造成效。無尾目的蛙類為臺灣常見的生物，其生長歷程及生理需求等特點反應棲息環境的品質。調查樣區位於台北市文山區的永建生態園區，包含十個樣點，區分為人工生態草溝、自然溼地與人工排水溝三種棲地類型。透過收集生物、水質、微氣候及微棲地等該區域資料，使用複迴歸分析與赤池信息準則進行分析，以找出影響蛙類數量及空間分布之關鍵環境因子模型，提供都市未來營造與管理蛙類棲地考量依據。 將本研究樣區環境因子與對數轉換之澤蛙（Fejervarya limnocharis）數量，作線性複迴歸分析，分成兩部分進行討論：(1)十個月平均環境因子與(2)各月份環境因子。平均環境因子（2014年4月至2015年1月）分析結果中，顯著的正向因子有空氣相對濕度與水中溶氧量，負向因子則為最高溫度。以上三個因子的變化範圍：空氣相對溼度在75至83 %，水中溶氧量範圍在1.95到5.14 mg/L，最高溫度在28.57至38.14°C。而各月份環境因子（2014年4月至2014年11月）對澤蛙的影響，透過赤池信息準則篩選，各個單月份迴歸模型所使用的參數組合都不同。然而，八個單月份模型中，遮蔽率、水域面積、植被覆蓋率、碳酸氫根與水中溶氧量，多呈正相關；水域邊坡坡度與水中硝酸態氮，則多呈負相關。永建生態園區內十個樣點的綜合分析顯示，人工生態草溝遮蔽率大於80 %、水域面積大於50 m2及水域邊坡坡度小於20°，硝酸態氮濃度小於0.1 mg/L，碳酸氫根濃度大於200 mg/L，有較高的澤蛙數量；自然溼地植被覆蓋率大於80 %，亦有次多之澤蛙數量。

Urban sprawl causes habitat loss and the conversion of natural landscapes to residential, business, and industrial areas. Recently, efforts have been put in place to create environments for wildlife in urban areas to achieve sustainable development. Amphibians were selected as target species in this study to evaluate the effectiveness of the habitat creation in the urban area. Anurans are common species in Taiwan and sensitive to the changes of environment conditions due to their physiology and life history. Field surveys were conducted at five natural wetlands, three constructed ecological ditches, and two drainage ditches within Yong-Jian Ecological Park, Wenshan District, Taipei City. Collected data included richness of frogs, water quality, microclimate and microhabitat of the ten wetlands. A multiple regression method and corrected Akaike information criterion (AICc) were used to analyze the data by two approaches. First, the relationship between the average frog (Fejervarya limnocharis) number and the average environmental parameters (April 2014 to January 2015) were analyzed to provide a general perspective. Dissolved oxygen (1.95 to 5.14 mg/L) and relative humidity (75 to 83%) are positively correlated to the average frog number whereas maximum air temperature (28.57 to 38.14 °C) is negatively. Second, the data from April 2014 to November 2014 (eight months) were calculated on monthly basis. The used parameters in the eight multiple regression models were all different from each other. However, tree canopy, grass coverage, pond surface area, dissolved oxygen, and bicarbonate ion are positively correlated with the number of the Fejervarya limnocharis. However, the occurrence of the Fejervarya limnocharis was negatively related to bank slope and nitrate concentration. According to this study, the number of the Fejervarya limnocharis was higher at the constructed ecological ditches sites with following attributes: tree canopy > 80%, water surface > 50 m2, bank slope < 20°, Nitrate concentration < 0.1 mg/L, hydrogen carbonate ion > 200 mg/L.