溪頭地區崩塌裸露地歷史變遷及植生恢復監測

Abstract

本研究透過遙感探測技術，對台大實驗林溪頭地區進行崩塌裸露地的植生恢復監測，同時也利用歷年的衛星影像來瞭解本區的崩塌裸露地歷史，進而得知數個崩塌裸露地的熱點。 從過去11年的崩塌裸露地可以看出，溪頭地區的崩塌裸露地多發生在1996年、1999年及2001年，這三年分別有賀伯颱風、921集集大地震以及桃芝颱風等三個大型的天然災害發生，尤其是921集集大地震以及桃芝颱風，兩者分別新造成112.88公頃及140.54公頃的崩塌裸露。不過在這些大型天災發生後的兩、三年，植群的恢復相當迅速，均可達到八成以上的覆蓋率。 利用SPOT衛星影像的資料選出六種崩塌裸露地類型，分別為短恢復期人工造林地和天然復育地、中恢復期人工造林地和天然復育地、長恢復期人工造林地和天然復育地，經進行地面調查，得知這些區域有60科116種植物，在進行植群分析之後依照六種崩塌裸露地類型分為五節芒型、長梗紫麻-大花曼陀羅型、剛莠竹型、狼尾草型、冷清草-棕葉狗尾草-糯米糰型、江某-長梗紫麻型等六種植群型態。 崩塌裸露地區的NDVI值也顯示，植群受到天然災害的影響相當大，在三個主要的天災年度中，NDVI值均呈現比其他年度下降的狀況，此顯示植物所受到的傷害相當可觀。從歷年的NDVI值可以得知歷史越久的崩塌裸露地由於恢復時間長，所以NDVI值均較高；反之，歷史越短的崩塌裸露地由於恢復時間短，NDVI值均較低。

In this study, we use remote sensing measurement technology to monitor the plant recovery on landslide in Chitou area, National Taiwan University Experimental Forest during 1994-2004. We also learn the history of the landslide area, and landslide hot points through this process. From the landslide history we can see most of the landslide happened in the year 1996, 1999, and 2001. In these years, three major natural disasters stroke Chitou, they were typhoon Herb, the 921 earthquake, and typhoon Toraji. Especially the 921 earthquake and typhoon Toraji, both brought 112.88 hectare and 140.54 hectare of landslide to Chitou. But despite the large area of landslide, the plant recovers very fast after major natural disasters. In two or three years of recovery, the recovery rates were all over 80%. Using the data gathered form SPOT images, we select 6 types of landslides and started the land examine. The result showed that there 60 family, 116 species of plants in these 6 types of landslide areas. They are short term recovery-artificial forest, short term recovery-nature forest, mid term recovery-artificial forest, mid term recovery-nature forest, long term recovery-artificial forest, and long term recovery-nature forest. Using the information we gathered form the field, we can divided the plant society into six groups, the Miscanthus floridulus type, the Villebrunea pedunculata - Brugmansia suaveolens type, the Microstegium ciliatum type, the Pennisetum alopecuroides type, Elatostema lineolatum var. majus - Setaria palmifolia - Gonostegia hirta, and the Schefflera octophylla - Villebrunea pedunculata type. The NDVI in the landslide areas also showed, the natural disaster affected the plant a lot. The NDVI during each year of the three major natural disasters were lower than other years. It shows the plants suffered form some serious damages during those years. Yet, from the changes of NDVI in each year, we know that the longer the landslide area existed, the higher the NDVI are, and the shorter the landslide area existed, the lower the NDVI were.