河川流域為獨立完整的生態系統，可為自然保育的合理尺度和系統管理單元，然首須合理界定和分析流域內生態品質狀態，但因流域生態結構與功能極為複雜，有必要建立簡化分析方法。利用衛星遙測影像分析NDVI（常態化差異植生指數），可反映陸域環境基礎生產力，應能作為生態系統品質分析重要依據。本研究針對河川流域層級結構，利用SPOT衛星影像分析頭前溪各子流域NDVI分布，並以此界定流域潛在生態品質。再依據NDVI分布，運用地景外形指數、距離指數、和面積指數，分析流域自然地景結構，並將其分級與評分，最後綜合為地景效應總指數，以此評估各子流域生態棲地零碎化程度。結果顯示，此一方法程序，可合理有效研判流域整體生態品質與其空間結構，適用於流域地景尺度相關分析，應能具體應用在開發個案或政策環評、國土或區域規劃、與永續發展政策的研擬。 Being independent and wholistic ecosystems, river basins can be taken as the realistic scale and the systematic management unit for the natural conservation. However, it is necessary firstly to define and analyze the ecosystem quality in the basin. A simplified analysis method is required because the structure and function of watersheds is very complex. Using satellite remote-sensing image to analyze NDVI (Normalized Difference Vegetation Index), which can reflect the primary productivity in the land environment, could be taken as an important approach for the ecosystem quality analysis. According to river hierarchical structure, this study was dedicated to the analysis of NDVI distribution by the SPOT satellite image, and thereby to defining the ecological quality on the Toucian river basin. Based on the NDVI distribution, the study further analyzed the natural landscape structure of the watershed by the landscape shape, distance, and area index, furtherly integrating them into total index of landscape effects in order to assess the fragmentation level of the ecological habitat for each sub-watershed.The results showed that the method and procedure could reasonably and effectively describe the ecosystem quality and spatial structure of watersheds. It is appropriate for the related landscape-scale analysis of watersheds, and substantially for the environmental assessment in the policy or development cases, the national land or regional planning, and the policy-making with sustainable development.
