Basal Area – The cross-sectional area of a tree stem, including the bark, measured at breast height (4.5 feet above the ground).
Basal Area Loss – In the context of Rapid Assessment of Vegetation Condition after Wildfire analysis, the percent change in basal area relative to the pre-fire condition. Basal area loss does not describe a permanent loss of basal area within a forest, but simply describes the amount of change in live basal area at the time of assessment. Also called basal area mortality or percent change in basal area.
Burn Severity – A qualitative assessment of the heat pulse directed toward the ground during a fire. Burn severity relates to soil heating, large fuel and duff consumption, consumption of the litter and organic layer beneath trees and isolated shrubs, and mortality of buried plant parts. (NWCG Glossary of Wildland Fire Terminology)
Burned Area Boundary – The boundary defining the area burned by a fire. In the context of satellite-based post-fire burn severity mapping, burned areas are typically delineated using remote sensing indices and/or spectral data, and may include unburned “island” areas.
Burned Area Emergency Response (BAER) Team – BAER teams are formed to analyze post-fire conditions and to take immediate emergency stabilization action to prevent loss of life and property and critical and natural resources. It is the Agency Administrator’s responsibility to order or designate a BAER Team (NWCG Glossary of Wildland Fire Terminology).
Burned Area Reflectance Classification (BARC) – A satellite-derived data layer of post-fire vegetation condition. The BARC has four thematic classes representing burn severity: high, moderate, low, and unburned. This product is used as an input to the soil burn severity data/map product produced by the Burned Area Emergency Response teams.
Canopy Cover – The ground area covered by the crowns of trees or woody vegetation as delineated by the vertical projection of crown perimeters. It is commonly expressed as a percent of total ground area. Also called crown cover. (Society of American Foresters. The Dictionary of Forestry, John A. Helms, Editor, 1998).
Canopy Cover Loss – In the context of Rapid Assessment of Vegetation Condition after Wildfire analysis, the percent change in live canopy cover relative to the pre-fire condition. Depending on the vegetation type and fire characteristics, the canopy cover loss estimate for an extended assessment may differ significantly from that of an initial assessment. Also called canopy cover mortality or percent change in canopy cover.
Closed Tree Canopy – Vegetation dominated by trees with interlocking crowns, typically at least 60% crown cover.
Composite Burn Index – A numerical, synoptic rating calculated from a field-based estimate of fire effects on individual strata within a plot or site in a burned area. Estimates the overall impact to a site based on post-fire conditions averaged across the burnable portion of the site.
Deforested Vegetation Condition – A temporary condition of the forest vegetation after a wildfire has burned at such high severity that not enough trees were left alive for the forest to naturally regenerate and function normally. It is a signal that reforestation treatments are required to re-establish forest cover promptly. As a rule, this describes a resulting forest with less than 20% canopy cover. A follow-up diagnosis followed by a silvicultural prescription is required to complete the final assessment and determine the type of management activities that are needed to recover the area.
Differenced Normalized Burn Ratio (dNBR) – A differenced NBR image, or change image, created where the post-fire NBR is subtracted from the pre-fire NBR. The dNBR may be used to discriminate burned from unburned areas and identify vegetation burn severity classes. The dNBR is calculated as:
dNBR = NBR pre-fire – NBR post-fire
Differenced Normalized Difference Vegetation Index (dNDVI) – A differenced NDVI image, or change image, created where the post-fire NDVI is subtracted from the pre-fire NDVI. The dNDVI may be used like the dNBR to discriminate burned from unburned areas and identify vegetation burn severity classes. The dNDVI is calculated as:
dNDVI = NDVI pre-fire – NDVI post-fire
Emergency Assessment – Fire mapping assessments that rely on satellite data typically required at or near fire containment in order to assist in identifying imminent post-fire threats to life, safety, property, and critical natural and cultural resources, and support emergency stabilization measures before significant storms occur.
Emergency Stabilization – Planned actions to stabilize and prevent unacceptable degradation to natural and cultural resources, to minimize threats to life or property resulting from the effects of a fire, or to repair/replace/construct physical improvements necessary to prevent degradation of land or resources (NWCG Glossary of Wildland Fire Terminology).
Extended Assessment – Fire mapping assessments that rely on satellite data typically acquired during the growing season following a fire in order to include delayed first order effects (e.g., latent tree mortality) and dominant second order effects that are ecologically significant (e.g., initial site response and early secondary effects).
Fire Atlas – A compendium of geospatial layers, maps, and tabular information that illustrate fire activity at the individual fire level for a given geographic area and/or period of time.
Fire Effects – The physical, biological, and ecological impacts of fire on the Environment (NWCG Glossary of Wildland Fire Terminology).
Fire Intensity – The amount of energy or heat release per unit time or area during the consumption of organic matter (Field Guide for Mapping Post-Fire Soil Burn Severity).
Fire Severity – Degree to which a site has been altered or disrupted by fire; loosely, a product of fire intensity and residence time (NWCG Glossary of Wildland Fire Terminology).
First Order Fire Effects – The effects that concern the direct or immediate consequences of fire, such as biomass consumption, crown scorch, bole damage, and smoke production. First order effects form an important basis for predicting secondary effects such as tree regeneration, plant succession, and changes in site productivity, but these involve interaction with many other non-fire variables (NWCG Glossary of Wildland Fire Terminology).
Forested Vegetation Condition – A post-fire condition in which fire severity was classified as low, with the initial assessment showing enough live trees remaining for the forest to function normally. Most of the area has more than 20% canopy cover. A follow-up diagnosis and silvicultural prescription may be required to complete the final assessment and determine what type of management activities are needed to maintain the growth and vigor of the forest. Also, a severity class used in Rapid Assessment of Vegetation Condition after Wildfire assessments in 2007, in which percent basal area loss is less than 50%.
Ground Cover – Organic cover including litter, duff, and woody debris that can mitigate runoff and erosion (Field Guide for Mapping Post-Fire Soil Burn Severity).
High Burn Severity – A discrete burn severity class identified when thresholding dNBR data for Burned Area Emergency Response or Monitoring Trends in Burn Severity assessments, dNDVI for BAER assessments or RdNBR data for Rapid Assessment of Vegetation Condition after Wildfire assessments. In forested ecosystems, it typically represents areas affected by fire where:
- Substrates, litter is totally consumed; duff is typically nearly entirely consumed;
- Medium and heavy woody debris are at least partially consumed and at least deeply charred with mostly ash and charcoal remaining;
- Overstory trees typically exhibit greater than 75 percent mortality;
- Crown char is typically 100 percent from torching fire, and significant branch loss is present at the highest crown levels.
In grassland and shrubland ecosystems, it typically represents areas affected by fire where:
- Over half of the site exhibits over 50 percent cover of newly exposed mineral soil or rock fragments;
- Herbaceous plants and shrubs are almost completely charred or consumed above ground, often with notable branch loss on taller shrubs;
- Resprouting from perennial plants, except grasses, is strongly reduced.
Hydrophobicity – Resistance to wetting exhibited by some soils, also called water repellency. The phenomenon may occur naturally or may be fire-induced. It may be determined by water drop penetration time, equilibrium liquid-contact angles, solid-air surface tension indices, or the characterization of dynamic wetting angles during infiltration (NWCG Glossary of Wildland Fire Terminology).
Increased Greenness – A discrete burn severity class identified when thresholding dNBR data for Monitoring Trends in Burn Severity assessments. It typically represents areas that burned but display more vegetation cover, density, and/or productivity, usually within one growing season after fire. This is a fire-caused effect from release of nutrients into soil, and/or reduced competition for nutrients, light and water. These areas are usually herbaceous or low shrub communities that undergo little change in species composition after fire.
Initial Assessment – Fire mapping assessments that rely on satellite data typically acquired at the first opportunity after fire to capitalize on the maximum post-fire data signal and is used primarily in ecosystems that exhibit rapid post-fire vegetation response (i.e. herbaceous and particular shrubland systems).
Landsat Imagery – Thematic Mapper, Enhanced Thematic Mapper Plus, and Operational Land Imager image data from the Landsat 5, Landsat 7, and Landsat 8 satellites, respectively. Image scenes have a footprint area of approximately 34,000 square kilometers and a pixel resolution of 30 meters. Spectral information is contained in several bands representing distinct wavelengths in the visible, infrared, and thermal portions of the electromagnetic spectrum.
Low Burn Severity – A discrete burn severity class identified when thresholding dNBR data for Burned Area Emergency Response or Monitoring Trends in Burn Severity assessments, dNDVI for Burned Area Emergency Response assessments or RdNBR data for Rapid Assessment of Vegetation Condition after Wildfire assessments. It includes areas where more than a small proportion of the site burned. All vegetation strata are slightly altered from the pre-fire state, but some may show pronounced burn effects. In forested ecosystems, it typically represents areas affected by fire where:
- Substrates, litter often exhibits fairly high consumption (up to 100 percent).
- Duff, woody debris and newly exposed mineral soil typically exhibit some change.
- Low vegetation (<1 meter) and shrubs or trees (1-5 meters) may show significant aboveground scorch, char or consumption, and vegetation density or cover may be greatly altered.
- Intermediate and large overstory trees may exhibit up to 25 percent mortality evidenced by crown char or scorch.
- Char height from ground flames is typically less than 3 meters.
Moderate Burn Severity – A discrete burn severity class identified when thresholding dNBR data for Burned Area Emergency Response or Monitoring Trends in Burn Severity (MTBS) assessments, dNDVI for Burned Area Emergency Response assessments or RdNBR data for Rapid Assessment of Vegetation Condition after Wildfire assessments. It includes areas that exhibit conditions that are transitional in magnitude and/or uniformity between characteristics within low and high burn severity classes.
Fire Occurrence Database – Relevant spatial and aspatial fire occurrence data elements for each fire mapped and assessed.
National Forest – A unit formally established and permanently set aside and reserved for National Forest purposes. There are 154 National Forests in the United States, located in 43 states and Puerto Rico.
National Forest System - A nationally significant system of Federally owned units of forest, range, and related land consisting of national forests, purchase units, national grasslands, land utilization project areas, experimental forest areas, experimental range areas, designated experimental areas, other land areas, water areas, and interests in lands that are administered by the U.S. Forest Service or designated for administration through the Forest Service. Also see Section 11 of Forest and Rangeland Renewable Resources Planning Act of 1974 (P.L. 93-378, 88 Stat. 476, 16 U.S.C. 1609).
Non-Processing Mask – A discrete class assigned in Burned Area Emergency Response, Rapid Assessment of Vegetation Condition after Wildfire and Monitoring Trends in Burn Severity assessments representing areas of the fire masked out from the analysis. It includes pixels/areas where a reliable burn severity assessment cannot be conducted due to one or more satellite data or atmospheric/terrain interference issues (e.g. data gaps in Landsat 7 Scan Line Corrector-off imagery, clouds, cloud shadows, active fire, smoke, snow, and open water).
Normalized Burn Ratio (NBR) – A normalized index that leverages the contrast in response by the near-infrared (NIR) and short-wave infrared (SWIR) bands to leaf area, plant productivity and moisture. Healthy, green vegetation has a high reflection of NIR light and strongly absorbs SWIR light resulting in high NBR values. Increasing damage to vegetation by fire and the exposure of dry, rocky soils results in low NBR values. NBR is calculated for each pre-fire and post-fire scene as:
NBR = (NIR - SWIR) ÷ (NIR + SWIR)
Normalized Difference Vegetation Index (NDVI) – A normalized index that emphasizes the contrast in response by the red (R) and near-infrared (NIR) bands to chlorophyl and the cell structure of vegetation. The chlorophyl in healthy, green vegetation absorbs visible (R) light while the cell structure of the healthy vegetation reflects NIR light resulting in high NDVI values. Increasing damage to vegetation by fire and/or seasonal vegetation senescence results in low NDVI values. NDVI is calculated for each pre-fire and post-fire scene as:
NDVI = (NIR - R) ÷ (NIR + R)
Open Tree Canopy – Vegetation dominated by trees with crowns not usually touching, typically with 25-60% crown cover.
Prescribed Fire – Any fire ignited by management actions to meet specific objectives (NWCG Glossary of Wildland Fire Terminology).
Relative differenced Normalized Burn Ratio (RdNBR) – a normalized version of the dNBR that removes the biasing effect of the pre-fire conditions (Miller et al 2009). The algorithm for RdNBR is calculated as: RdNBR = dNBR / SquareRoot(ABS(NBR pre-fire / 1000))
Sentinel 2 Imagery – Multispectral Instrument image data from the European Space Agency’s Sentinel 2A and Sentinel 2B satellites. Image scenes (tiles) have a footprint area of approximately 10,000 square kilometers and a pixel resolution of 10-20 meters. Spectral information is contained in several bands representing distinct wavelengths in the visible, infrared, and thermal portions of the electromagnetic spectrum.
Silvicultural Examination – The process of gathering field data for a forest stand to determine its current condition. Silvicultural and other management decisions are based on the data collected from these examinations. Rapid Assessment of Vegetation Condition after Wildfire data can be a useful tool for prioritizing field exams.
Silvicultural Prescription – A written document that describes management activities needed to implement treatments. It documents the results of an analysis of present and anticipated site conditions and management direction. It also describes desired future vegetation conditions in measurable terms. The desired conditions are a basis for treatment, monitoring, and evaluation.
Spatial Resolution – The areal extent of the smallest unit, pixel, or feature that can be resolved on an image, map, or surface. Typically expressed as a measure of distance, i.e., 30 meter pixel, but can also be expressed as a unit of area.
Spectral (Remote Sensing) Index – A mathematical calculation derived from two or more image bands. Typically used to enhance the spectral properties of a feature or condition of interest on the ground, i.e., burn scars.
Thematic Resolution – The finest level of content for a given map or thematic layer attribute.
Treatment – Any of a set of management activities that can assist in the prompt recovery of forestlands. Treatments can include any combination of live, dead, or dying wood removal or disposal (with or without commercial value) by logging, piling, masticating, burning, or other methods. In addition, planting or seeding, with or without site preparation, are appropriate management activities designed to foster prompt recovery following wildfire. In some cases, the preferred "treatment" is natural regeneration and monitoring.
Unburned to Low – A discrete burn severity class identified when thresholding dNBR data for Burned Area Emergency Response or Monitoring Trends in Burn Severity assessments or dNDVI for Burned Area Emergency Response assessments. It includes areas that are either unburned, or when visible fire effects occupy a small proportion of the site, on the order of less than 5 percent. The class may also include areas that recover very quickly after fire, such as grasslands or light surface burns under dense, non-impacted forest canopies.
Unmappable – A reported fire that is attempted to be mapped for a Burned Area Emergency Response, Rapid Assessment of Vegetation Condition after Wildfire or Monitoring Trends in Burn Severity assessment, but due to one or more technical issues, a publishable product cannot be generated.
Vegetation Group – In the context of Rapid Assessment of Vegetation Condition after Wildfire analysis, broad vegetation classes used for spatial analysis of burned area.
Wilderness Area – Areas designated by Congress as a part of the National Wilderness Preservation System.
Wildfire – A wildland fire originating from an unplanned ignition, such as lightning, volcanos, unauthorized and accidental human caused fires, and prescribed fires that are declared wildfires (NWCG Glossary of Wildland Fire Terminology).
Wildland Fire – Any non-structure fire that occurs in vegetation or natural fuels. Includes Wildfires and Prescribed Fires (NWCG Glossary of Wildland Fire Terminology).
Wildland Fire Use (Obsolete) – The application of the appropriate management response to naturally-ignited wildland fires to accomplish specific resource management objectives in predefined designated areas outlined in Fire Management Plans. Also called Wildfire for Resource Benefit.