建物擴張與棲地管理對宜蘭休耕水稻田鳥類多樣性及棲地偏好的影響

Abstract

在全球濕地生物多樣性快速流失下，水田被視為天然濕地的補充棲地，然而全球農田生物多樣性亦因農業集約化、地景破碎化等因素而快速減少。宜蘭的休耕水田是許多水鳥的重要棲地，而近年農舍建物擴張現象卻可能對水鳥造成衝擊。為釐清建物擴張的影響及鳥類棲地偏好，本研究分為兩個部分，第一部分於2016/17、2017/18冬季分別於蘭陽平原選擇42及51塊水田進行鳥類調查，並記錄田內因子（水深、植被覆蓋度、泥灘地覆蓋度、樣田面積）及樣田周圍500公尺內之地景結構（道路鄰接程度、道路密度、離建物最近距離、區塊形狀指數總和、建物分散程度、水體面積比例、植被面積比例、建物面積比例、離都市邊緣距離）以檢驗環境因子對鳥類多樣性的影響; 第二部分則於2017/18冬季在宜蘭新南以操作試驗比較田內水深、植被覆蓋度與田埂雜草有無對鳥類多樣性的影響。 第一部份結果顯示，離建物最近距離對鳥種豐富度與豐度呈顯著正相關，道路相鄰程度呈負相關。路徑分析結果顯示，離建物最近距離與建物分散程度對鳥類多樣性有直接影響，而離都市邊緣距離、道路密度與建物面積比例則為間接影響。田外植被對草生性水鳥之物種豐度呈正相關，水體面積比例與雁鴨科之物種豐富度及豐度呈正相關。田內尺度下，雁鴨科偏好深水環境，草生性水鳥偏好較高植被覆蓋度，中小型鷸鴴科則偏好淺水且植被稀疏的環境。第二部分的結果說明低水位（0–5 cm）水田之鳥類多樣性顯著高於中（6–10 cm）、高水位（>10 cm），而植被覆蓋度與田埂雜草有無則無顯著效果。因此，建物擴張嚴重衝擊了宜蘭農田之鳥類多樣性，且建議未來宜採聚居模式發展，以降低建物擴張的衝擊。在地景尺度下，保留或增加田間植被、水體亦有助於提高水田鳥類多樣性，田內尺度則建議在休耕期水田維持低水位(0–5 cm)，並保留少量雜草與再生稻提供敏感鳥種棲息，亦有助於提高宜蘭水田鳥類多樣性。

Under decreasing trend of natural wetlands, rice paddies have been regarded as compensative habitats for natural wetlands. However, agricultural intensification and landscape fragmentation have threatened farmland biodiversity worldwide. Fallow rice paddies of Yilan County are important habitats for waterbirds, but have been seriously encroached by urban sprawl. To examine effects of urban sprawl on bird species diversity and habitat preferences of birds, this study was divided into two section. In section 1, I conducted bird surveys in 42 and 51 sampling paddies in 2016/17 and 2017/18 winter respectively on Lanyang Plain, and measured field conditions (water depth, vegetation coverage, mudflat coverage, and sampling paddy area) and landscape structures within 500 m buffer zone (road adjacency, road density, distance to the nearest building, nearest neighbor index of building, sum of shape index, water area ratio, built area ratio, vegetated area ratio, and distance to urban area) to examine effects of environmental variables. In section 2, field experiments were conducted in 2017/18 winter in Xinnan Village to examine effects of water depth, vegetation coverage, and presence/absence of ridge grass on bird species diversity. Results of section 1 revealed that distance to the nearest building and road adjacency were positively and negatively correlated with bird species richness and abundance respectively. Distance to the nearest building and nearest neighbor index of buildings had direct effects, while distance to urban area, road density and built area ratio had indirect effects. Vegetated area ratio was positively correlated with species richness of vegetation-dependent species, and water area ratio was positively correlated with species richness and abundance of waterfowls. At within-filed scale, waterfowls preferred deep water, vegetation-dependent species preferred high vegetation coverage, and medium-size and small-size waterbirds preferred low water depth and low vegetation coverage. In section 2, both species richness and abundance in low water depth (0–5 cm) sampling sites were significantly higher than in medium (5–10 cm) and high water depth (>10 cm), and vegetation coverage and presence/absence of ridge grass had non-significant effect on bird species richness and abundance. In conclusion, urban sprawl would seriously impact on bird species diversity in rice paddies of Yilan, and collecting housing is strongly suggested to mitigate the impacts by concentrate disturbances from buildings. At landscape scale, preserving or generating waterbody and vegetated area would increase bird species diversity. At within-field scale, maintaining low water depth (0–5 cm) and less vegetation coverage for sensitive species were also suggested to increase bird species diversity in fallow rice paddies of Yilan.