Evaluating the potential of Landsat TM/ETM+ imagery for assessing fire severity in Alaskan black spruce forests
Elizabeth E. Hoy A E , Nancy H. F. French B , Merritt R. Turetsky C , Simon N. Trigg A D and Eric S. Kasischke AA Department of Geography, University of Maryland, 2181 LeFrak Hall, College Park, MD 20742, USA.
B Michigan Tech Research Institute, Michigan Technological University, 3600 Green Court, Suite 100, Ann Arbor, MI 48105, USA.
C Department of Integrative Biology, University of Guelph, Guelph, ON, N1G 2W1, Canada.
D Department of Geographic Information Management, Cranfield University, Cranfield, Bedfordshire, UK.
E Corresponding author. Email: ehoy@umd.edu
International Journal of Wildland Fire 17(4) 500-514 https://doi.org/10.1071/WF08107
Submitted: 20 June 2008 Accepted: 26 June 2008 Published: 6 August 2008
Abstract
Satellite remotely sensed data of fire disturbance offers important information; however, current methods to study fire severity may need modifications for boreal regions. We assessed the potential of the differenced Normalized Burn Ratio (dNBR) and other spectroscopic indices and image transforms derived from Landsat TM/ETM+ data for mapping fire severity in Alaskan black spruce forests (Picea mariana) using ground measures of severity from 55 plots located in two fire events. The analysis yielded low correlations between the satellite and field measures of severity, with the highest correlation (R2adjusted = 0.52, P < 0.0001) between the dNBR and the composite burn index being lower than those found in similar studies in forests in the conterminous USA. Correlations improved using a ratio of two Landsat shortwave infrared bands (Band 7/Band 5). Overall, the satellite fire severity indices and transformations were more highly correlated with measures of canopy-layer fire severity than ground-layer fire severity. High levels of fire severity present in the fire events, deep organic soils, varied topography of the boreal region, and variations in solar elevation angle may account for the low correlations, and illustrate the challenges faced in developing approaches to map fire and burn severity in high northern latitude regions.
Additional keywords: composite burn index, Picea mariana, spectroscopic index.
Acknowledgements
The research in the paper was supported by NASA through Grant NNG04GD25G and the Bonanza Creek Long-Term Ecological Research program (USFS grant number PNW01-JV11261952–231 and NSF grant number DEB-0080609). We thank Evan Ellicott, Evan Kane, Gordon Shetler, Luz Silverio, Sam Upton, Richard Powell and Lucas Spaete for assisting in the collection of field data. We also thank the two anonymous reviewers who provided us with such valuable insight and direction.
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