Landscape Assessment primarily addresses the need to identify and quantify fire effects over large areas, at times involving many burns. In contrast to individual case studies, the ability to compare results is emphasized, along with the capacity to aggregate information across broad regions and over time. Methods provide a quantitative picture of the whole burn as if viewed from the air, showing the spatial heterogeneity of burns, and how fire interacts with vegetation and topography. The data are suitable for moderate resolution (30 m) applications, and can be obtained within one year of the subject fire. They are adapted to remote sensing and GIS technologies, which can produce a variety of derived products such as maps, images and statistical summaries.
The quantity measured and mapped is "burn severity", defined here as a scaled index gauging the magnitude of ecological change caused by fire. In the process, two methodologies are integrated. One, BR, involves Landsat 30-meter data and a derived radiometric value called the Normalized Burn Ratio (NBR). The NBR is temporally differenced between pre- and post-fire datasets to determine the extent and degree of detected change. The other, BI, adds a complimentary field sampling approach, called the Composite Burn Index (CBI). It entails a relatively large plot; independent severity ratings for individual strata, and synoptic scores for the whole plot area. Ratings consider such criteria as color and condition of substrates, amount of fuel and vegetation consumed, regeneration from pre-fire vegetation, establishment of new seral species, and blackening or scorching of trees. Plot sampling may serve to calibrate and validate remote sensing results, to relate detected radiometric change with actual burn characteristics on the ground. Alternatively, plot sampling may be implemented in a stand-alone field survey for individual site assessment.
