| Summary: | 碩士 === 國立臺灣大學 === 森林環境暨資源學研究所 === 107 === 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.
|
|---|
