- 期刊
- OpenAccess
2000年碧利斯颱風干擾前後福山試驗林NDVI變動之研究
Changes in the Normalized Difference Vegetation Index (NDVI) at the Fushan Experimental Forest in Relation to Typhoon Bilis of 2000
摘要
頻繁的颱風干擾對台灣森林生態系有廣大而深遠的影響，透過不同時期遙測資料所得植生指數的比較，可用來探討颱風干擾所造成的植生變動。本研究選定福山試驗林，利用2000年8月10日、2000年9月5日、2001年7月1日碧利斯颱風前後三個時期的SPOT影像，計算各期的常態化差異植生指數(normalized difference vegetation index，NDVI)及其變遷，以了解颱風干擾所造成的植生之時空變動。結果發現，福山試驗林植生覆蓋率高，區域內變異少；碧利斯颱風造成福山試驗林NDVI整體平均下降了48%，但隔年七月其整體平均亦上升了48%，回復到颱風前的數值。海拔高、坡向為東或東南的區域NDVI較高，但NDVI較高處其受颱風干擾及之後回復的量亦較大；無論是在海拔、坡度或坡向的比較上，三個時期同一組內之變異，常較不同組別間的差異為大，故欲完整掌握福山試驗林植生分布的空間變異，應對較小空間尺度變異做更深入的探討。
並列摘要
Frequent typhoon disturbances have major impacts on the dynamics of forest ecosystems in Taiwan. By analyzing multi-temporal satellite images, it is possible to detect large-scale forest canopy changes caused by typhoon disturbances. We calculated normalized difference vegetation index (NDVI) from 3 SPOT images (10 Aug. 2000, 5 Sept. 2000 and 1 July 2001) to detect vegetation changes in the Fushan Experimental Forest before and after typhoon Billis struck Taiwan on 21~23 Aug. 2000. Results indicated that the standard deviation of the NDVI was very small suggesting that the vegetative cover was rather homogenous at the Fushan Experimental Forest. Following typhoon Billis, the NDVI decreased 4.8%, but it subsequently increased 4.8% and therefore had returned to pre-typhoon levels by July 2001. The NDVI tended to be higher at higher elevations and on east-facing slopes than at lower elevations and on slopes with other aspects. There was a positive correlation between the rates of NDVI decrease caused by typhoon Bilis and the post-typhoon recovery. For each of the 3 images, the variation of the NDVI within the same category of elevation, slope, or aspect was typically higher than that among batch variations. Thus, a better characterization of small-scale variations is critical to our understanding of the spatial variations of the vegetation distribution in the Fushan Experimental Forest.