利用衛星影像探討高美濕地內雲林莞草生長範圍的變遷研究

Abstract

高美濕地是國內知名的沿海濕地之一。稀有保育植物「雲林莞草」在台灣西海岸分布中，高美濕地是最廣的。早期雲林莞草在西部海岸潮間帶均有分布，然而近幾十年來，因土地開發利用，人為行為的介入，促使雲林莞草生長範圍大量減少，而面臨頻於絕種的危機。在國內的雲林莞草研究，多以現地調查方法來探討雲林莞草的生物特性及其環境因子或保護區內生物種的棲息及繁殖等，但尚無探討雲林莞草生長範圍的時間變化，此主題乃為本文的研究主要目的。 本研究使用的方法包括影像處理的技術及植生範圍界定。先以IHS轉換法提高衛星影像圖的空間解析度，增加衛星影像辨識能力，以及將多時期影像進行幾何套合等影像前處理之動作，再以常態化差異植生指數判定雲林莞草的生長範圍，進一步本文利用馬可夫隨機場及各影像NDVI的植物界定值的平均值，來區分雲林莞草生長密集及稀疏區的範圍。 最後以往昔雲林莞草的生物量時間變化的研究成果修正不同時間影像所計算面積至最高生長量的相同時間，分析在2006年至2011年的高美濕地內雲林莞草生長範圍。由迴歸的直線顯示雲林莞草的生長範圍有每年減少11,981 m2的趨勢。

Gaomei wetland is one of famous coastal wetlands in Taiwan. Bolboschoenus planiculmis is one of protected rare species in the Gaomei wetland, which holds the biggest area distributed by Bolboschoenus planiculmis among western coasts of Taiwan. In the early time a large quantity of Bolboschoenus planiculmis was well distributed along western coasts of Taiwan. However, it has been suffering from human impact of land utilization for recent decades and being on the verge of extinction. Therefore some investigations by field surveying were carried out on biometric data processes, corresponding surrounding environments and animals in the natural habitat of Bolboschoenus planiculmis. The issue of temporal variation of distributed area by Bolboschoenus planiculmis in the Gaomei wetland was never discussed and is the aim of the thesis using satellite images. The methodology of the thesis includes techniques of image processing and area detection of plants. IHS method was used to improve spatial the spatial resolution of satellite images and NDVI was used to distinguish the area distributed by Bolboschoenus planiculmis from those by water or by sand. Markov random field (MRF) process with an average NDVI from five satellite images was used to figure out the area intensively and extensively distributed by Bolboschoenus planiculmis for each image. Finally depending on the previous measurement on the temporal variation of quantity of Bolboschoenus planiculmis over unit area in the Gaomei wetland the calculated areas of intensively and extensively distributed by Bolboschoenus planiculmis for each image in different time were corrected to those at the same time of maximum quantity over one year. The fitted straight line by linear regression on the data of calculated areas of five satellite images from 2006 to 2011 shows a decreasing trend of total area distributed by Bolboschoenus planiculmis at a rate of 11,981 m2 per year.