U.S. Forest Service Post-Fire Vegetation Conditions on the National Forests

 

Process

The Rapid Assessment of Vegetation Condition after Wildfire (RAVG) analysis starts with a map of vegetation burn severity that is derived from an index of relative change between pre- and post-fire LANDSAT imagery. The RAVG process produces a suite of geospatial and tabular outputs that are delivered within 30 days following containment of a wildfire that burns 1,000 acres or more of forested National Forest System (NFS) land. RAVG products include standard vegetation basal area loss summary tables and maps. The tables and maps are produced by integrating existing vegetation maps and burn severity maps. RAVG analysis produces data describing post-fire vegetation conditions. RAVG spatial data and summary products are generated using a consistent methodology and facilitate post-fire vegetation management decision-making by reducing planning and implementation costs. RAVG data also serve a variety of related agency objectives, such as wildlife habitat analyses, and the initial assessment of reforestation and restoration needs.

The existing vegetation data comes from the Landscape Fire and Resource Management Planning Tools Project (LANDFIRE, Rollins & Frame 2006) Existing Vegetation Type (EVT) layer. The burn severity maps are built from pre and post-fire Landsat Thematic Mapper (TM) imagery using the Relative Differenced Normalized Burn Ratio (RdNBR, Miller & Thode 2007). The continuous RdNBR data are calibrated to field collected tree mortality data (live and dead by species and size class) to provide estimates of tree mortality.

Following large wildfires, a rapid initial assessment of post-fire conditions is important to support management decisions on National Forest System lands. This is particularly important in areas where vegetation management activities are allowed: outside of congressionally designated wilderness, Wild and Scenic River corridors, or research natural areas (RNA) where under certain conditions, vegetation manipulation may take place to meet specific resource objectives.

Changes to RAVG from 2007 to 2008

The RAVG wildfire summary tables and maps displayed on this website for 2007 are different than the information displayed for 2008 and thereafter. After completion of 2007 RAVG processing, a technical review was conducted with RAVG stakeholders: regional silviculturists, reforestation specialists, remote sensing analysts, and managers. The following changes were implemented for the 2008 fire season based on the discussions and decisions that were made during the technical review.

  • The LANDFIRE EVT Vegetation Group, "Grassland / Shrubland / Non Veg," was changed from reporting only total acres in 2007 RAVG tables to full reporting in 2008 RAVG tables. This vegetation group includes herbaceous plants generally forming at least 25% cover and in which trees, shrubs, and dwarf shrubs generally account for less than 25% of total vegetation.
  • The "Ownership / Status" column was changed by adding Non-USFS Wilderness acres into the 2008 RAVG tables. This change is also reflected in the 2008 RAVG maps.
  • In the 2008 analysis, rather than reporting only two condition classes in the "Vegetation Condition" column, Forested (where less than 50% change in basal area took place) and Deforested (where a change greater than 50% took place), the tables now report four classes of percent change in basal area. The four class change is also reflected in the 2008 RAVG maps.

The "Slope" column was removed from the 2008 RAVG tables. This data layer is still included in the GIS summary analysis, and is still reported in the raw data of each RAVG table. The original intent for this column was to make an initial estimation of harvest-ability of the site and was not related to reforestation needs following a wildfire.

U.S. Forest Service
Attn: Forest Management
1400 Independence Ave., SW, Mailstop: 1103
Washington DC 20250-0003

 

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Location: http://www.fs.fed.us/postfirevegcondition/process.shtml
Last modified: Thursday, 28-Mar-2013 13:36:11 CDT