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Title: Relative suitability of indices derived from Landsat ETM+ and SPOT 5 for detecting fire severity in sagebrush steppe

Author
item NORTON, JILL - IDAHO STATE UNIVERSITY
item GLENN, NANCY - IDAHO STATE UNIVERSITY
item GERMINO, MATT - IDAHO STATE UNIVERSITY
item WEBER, KEITH - IDAHO STATE UNIVERSITY
item Seefeldt, Steven

Submitted to: International Journal of Applied Earth Observation and Geoinformation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/16/2009
Publication Date: 7/23/2009
Citation: Norton, J., Glenn, N., Germino, M., Weber, K., Seefeldt, S.S. 2009. Relative suitability of indices derived from Landsat ETM+ and SPOT 5 for detecting fire severity in sagebrush steppe. International Journal of Applied Earth Observation and Geoinformation. 11:360-367.

Interpretive Summary: Vegetation management after fire on rangelands will differ based on the severity of the fire and the vegetation that was burned. Western rangelands cover large areas and are often difficult to access to measure vegetation or record burn severity. Satellite imagery may provide a solution to this problem as it has in forestry applications. The purpose of this paper was to test a combination of five remote sensing indices from two satellite systems (Landsat 7 ETM+ and SPOT 5) and determine which process was most useful at delineating burned from unburned areas and fire severity (unburned, moderately burned, completely burned). The study was conducted as part of a prescribed fire research project at the USDA/ARS U. S. Sheep Experiment Station in 2005 in sagebrush steppe rangelands. All systems were better at delineating burned versus unburned areas than delineating levels of fire severity. The Soil Adjusted Vegetation Index (SAVI) calculated from SPOT 5 had the greatest overall accuracy (100%) in delineating burned versus unburned areas. For delineating fire severity, the relative differenced Normalized Burn Ratio (RdNBR) using Landsat provided the highest accuracies (73% overall accuracy). Though SPOT’s spatial resolution likely conferred advantages for determining burn boundaries, Landsat’s higher spectral resolution (particularly band 7, 2.21 'm) appeared necessary for detecting differences in fire severity. These results indicate that satellite imagery can be used to to effectively map burn areas and determine fire severity in rangelands. These relatively inexpensive processes may serve as valuable aid to land managers of western rangelands.

Technical Abstract: Indices of burn area and fire severity based on remotely sensed data have been developed for forest ecosystems, but not semiarid shrublands in which large wildfires are a common occurrence and a major issue for land management. Our goal was to determine whether available satellite data could be used to remotely sense burn area and fire severity (completeness of vegetation removal) in shrublands. We compared the performance of five remote sensing indices with extensive ground-based cover assessments made before and after the burning of a 3 km2 area. The different indices were based on either Landsat 7 ETM+ or SPOT 5 data, using either single or multiple dates of imagery. Remote sensing indices delineating burned versus unburned areas had better overall, user, and producer’s accuracies than indices delineating levels of fire severity. The Soil Adjusted Vegetation Index (SAVI) calculated from SPOT had the greatest overall accuracy (100%) in delineating burned versus unburned areas. The relative differenced Normalized Burn Ratio (RdNBR) using Landsat provided the highest accuracies (73% overall accuracy) for delineating fire severity. Though SPOT’s spatial resolution likely conferred advantages for determining burn boundaries, Landsat’s higher spectral resolution (particularly band 7, 2.21 'm) appeared necessary for detecting differences in fire severity.