以衛星遙測多光譜影像探討台中環山地區森林火燒嚴重度分類及植生恢復

森林火災發生後，火燒跡地(Post Fire)的生態監測，是森林保育的重要議題。應用衛星影像的植生指標分析，可建立地面覆蓋狀態與衛星植生指標的關係模式，並可發展出以衛星植生指標進行森林火燒嚴重度的空間評估模式。而利用衛星多光譜影像，以紅光與近紅外光所組成的植生指標，以判別分析所發展的森林火災嚴重度的判別式，有較高的判識率，本研究以Landsat 7 ETM+(The Enhanced Thematic Mapper Pluss) 影像數據進行火燒嚴重度的製圖與分類，其所使用的規整化差異指數 (Normalized Difference Burn Ratio, dNBR)及相對規整化差異指數(Relativized Normalized Difference Burn Ratio, RdNBR)對火燒嚴重程度評估具有良好的效果。而利用物件導向分類，隸屬函數多層次的分割和分類進行，這種方法簡單，更適合用於評估區分3類以上的火燒嚴重度。在火災後植生恢復評估，環山地區於火燒後第3~5年，火燒重嚴重度地區VRR 值50-100達50%以上，於火燒後10年全區VRR(Vegetation Recovery Rate)達95%以上。目前美國NASA可提供免費的Landsat 衛星影像，其波譜解析力與空間解析力，應用於森林火燒發生後之植被受害程度評估與火燒跡地植生恢復監測為未來研究發展之重要角色。

關鍵字

植生指標；影像分類；植生恢復率；多光譜影像；火燒嚴重度

並列摘要

Monitoring the ecological change via post fire after forest fire is an important issue in forest conservation. The spatial model of forest fire severity had been developed by the establishment of the relational model of burned- site land cover and satellite vegetation index. The red and near-infrared band multi-spectral satellite images, which were used to estimate the vegetation index and to discriminate analysis to develop forest fire severity, showed a higher discriminative rate. This study used the Landsat 7 ETM + infrared band (band 7,2.08 -2.35 μm) to classify and map the severity of forest fire. We found Normalized Difference Burn Ratio (dNBR) and Relativized Normalized Difference Burn Ratio (RdNBR) are effective to assess fire severity. Using object-based image analysis, which is a multilevel segmentation and a classification, is easier to evaluate and distinguish at least 3 kinds of forest fire severities. The evaluation of vegetation recovery after forest fire showed VRR value was up to 50% in the high-severity burned areas after 3 to 5 years, and VRR value was more than 95% after 10 years. NASA provides free Landsat satellite images currently. The spectral resolution and spatial resolution are suitable to assess forest fire severity and monitor the vegetation recovery after forest fire.

並列關鍵字

Vegetation Index ； Fire Severity ； Multi-Spectral Image ； Normalized Difference Index ； Vegetation Recovery Rate

參考文獻

林朝欽、邱祈榮、周巧盈 (2005) 森林火災嚴重度之界定與評估：以武陵森林火災為例。台灣林業科學 20(3)：203-13。

Brewer, C. K., J. C. W., R.L. R., D. W. O., M. V. M. (2005) Classifying and mapping wildfire severity: A comparison of methods. Photogrammetric Engineering and Remote Sensing 71:1311-1320.

Chafer C., M. Noonan, E. Macnaught (2004) The post-fire measurement of fire severity and intensity in the Christmas 2001 Sydney wildfires. International Journal of Wildland Fire 13:227-240. DOI: doi:10.1071/WF03041.

Cocke A. E., P. Z. Fulé, J. E. Crouse (2005) Comparison of burn severity assessments using Differenced Normalized Burn Ratio and ground data. International Journal of Wildland Fire 14:189-198. DOI: doi:10.1071/WF04010.

Congalton R. G., K. Green (1999) Assessing the accuracy of remotely sensed

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以衛星遙測多光譜影像探討台中環山地區森林火燒嚴重度分類及植生恢復

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