Evaluating the potential of Landsat TM/ETM+ imagery for assessing fire severity in Alaskan black spruce forests

摘要

Satellite remotely sensed data of fire disturbance offers important information; however, current methods tonstudy fire severity may need modifications for boreal regions. We assessed the potential of the differenced NormalizednBurn Ratio (dNBR) and other spectroscopic indices and image transforms derived from Landsat TM/ETM+ data fornmapping fire severity in Alaskan black spruce forests (Picea mariana) using ground measures of severity from 55 plotsnlocated in two fire events. The analysis yielded low correlations between the satellite and field measures of severity, withnthe highest correlation (R2nadjustedn=0.52, P <0.0001) between the dNBR and the composite burn index being lower thannthose found in similar studies in forests in the conterminous USA. Correlations improved using a ratio of two Landsatnshortwave infrared bands (Band 7/Band 5). Overall, the satellite fire severity indices and transformations were more highlyncorrelated with measures of canopy-layer fire severity than ground-layer fire severity. High levels of fire severity presentnin the fire events, deep organic soils, varied topography of the boreal region, and variations in solar elevation angle maynaccount for the low correlations, and illustrate the challenges faced in developing approaches to map fire and burn severitynin high northern latitude regions.