Lower 48 Overview
Consumption and carbon emission estimates from biomass burning in the Lower-48 combine spatial fuel datasets and fire effects models that together describe the primary interacting physiographic and environmental compartments involved in fires. The ultimate goal is to create a generalized framework for estimating consumption and emissions from historical burn data then expanding the methodology into a predictive context for evaluating present and future consumption/emission probabilities. In addition, the utility of post-fire remote sensing burn ratios (i.e Differenced Normalize Burn Ratio [dNBR]) for assessing biomass consumption will be tested by combining spatial fuel consumption models with dNBR images to search for spatial correlations between fuel-type, fuel moisture, and burn severity. Principle input data, data characteristics, fire effects models, and results are described below.
Spatial Datasets
Data Characteristics
Fire Effects Models
Results
Spatial Datasets
FCCS (Fuel Characteristics Classification System)
FCCS is a 1-km fuelbed map for the contiguous United States. Fuel attributes contained within each fuel code provide the fuel loading inputs for the Consume consumption model. A fact sheet for the FCCS can be found here. Please visit the FERA (Fire and Environment Research Applications) webpage for complete FCCS system documentation and references.
Right: FCCS (Fuel Characteristics Classification System) fuel beds for the Western United States overlayed by Omernik's ecoregions. Also visible in the graphic are example burn perimeters derived using dNBR. The current fire database contains over 250 fire perimeters and dNBR images.
Below: FCCS fuel bed composition by ecoregion for the three main Western U.S. ecoregions examined in this study.
Interior Basin Range |
Western Cordillera |
Upper Gila Mountains |
USGS Burn Severity Data
Burn perimeters and dNBR images for post-2000 fires are freely distributed by the USGS via the Monitoring Trends in Burn Severity (MTBS) effot. Data is downloadable and comes in GIS-ready formats. Visit the project's website for more information.
Burn severity (dNBR or Differenced Normalized Burn Ratio) is a remote sensing change detection technique utilizing the two Landsat TM/ETM+ bands most responsive to fire-induced environmental change. dNBR is best described as the magnitude of environmental change occurring during a fire. Attempting to link dNBR to biomass consumption is one of the primary challenges this study addresses. Click here for an example summary of dNBR response by fuel type for three large fires. At left, burn severity mapped using the dNBR approach by the National Burn Severity Mapping program is compared to the Fuel Characteristic Classification System (FCCS) fuelbed map, developed by FERA, to learn the distribution of fuels burned at various severities.
Data Characteristics
Burn Severity and Forest Structure by Fuel Bed
Three main FCCS fuel types in the western U.S. are characterized below by dNBR burn severity distribution (top) by ecoregion (from 261 fires from 1984-2005) and forest structure (bottom - from FCCS analysis).
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Fire Effects Models
Consume 3.0
The Consume 3.0 model developed by FERA is capable of making biomass consumption estimates using FCCS descriptors and fuel moisture as model inputs. A goal of this project was to make the Consume model spatially explicit to analyze the geographic distribution of consumption patterns. More information on Consume can be found here. Consumption as a function of fuel moisture for the three ecoregions of interest in the Lower-48 (below left) are shown below.
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Similarly, above right shows consumption as a function of fuel moisture for the five most common fuel beds in the Western U.S. but divided into categories to show the use dNBR severity classes as a surrogate for fuel moisture. Error bars represent the range of modeled consumption within each severity class.
Below are charts showing the amounts of area burned for seven burn severity classes by fuelbed (top) and ecoregion (bottom) for a preliminary set of fires mapped by MTBS (97 fires).
Results
Applying Consume 3.0 to dNBR Values
Equating dNBR burn severity classes to Consume 3.0 fuel moisture classes as above yielded consumption estimates for fuel types and. ecoregions. The table below shows the distribution and consumption level of each fuel type by ecoregion.
Estimates of typical fuel consumption by fire size per ecoregion are shown below. These estimates were made by assuming typical fuel type distribution and consumption levels as described in the table above. Uncertainty ranges were derived by extracting the upper and lower limits in the range of modeled consumption within each severity class (as respresented by the error bars in the consumption graph to the right above).
