RAVG Glossary

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The cross-sectional area of a tree stem, including the bark, measured at breast height (4.5 feet above the ground).

In the context of RAVG 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.

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).

In the context of RAVG 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.

Vegetation dominated by trees with interlocking crowns, typically at least 60% crown cover.

See Canopy Cover

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.

An assessment based on post-fire imagery that was acquired near the peak of green following fire containment (most often from the following year). An extended assessment is conducted when an initial assessment is not a good option (e.g., late season fires) or when an estimate of delayed mortality is needed. For fires that occur in deciduous forests early in the year (leaf-off conditions), imagery from same year may be used. See also Initial Assessment.

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 RAVG assessments in 2007, in which percent basal area loss is less than 50% .

An assessment based on post-fire imagery that was acquired within approximately 45 days after fire containment. An initial assessment is the default for RAVG. See also Extended Assessment.

An on-going project designed to consistently map burn severity and perimeters of large fires that have occurred since 1984 across all lands of the United States. The data generated by MTBS are used to identify national trends in burn severity, providing information necessary to monitor the effectiveness of the National Fire Plan and the Healthy Forests Restoration Act.

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. 

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).

Vegetation dominated by trees with crowns not usually touching, typically with 25-60% crown cover.

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. RAVG data can be a useful tool for prioritizing field exams.

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.

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.

As used in RAVG products, any pixels/acreage that are masked because of any condition in the pre- or post-fire imagery that would prevent a valid vegetation condition assessment. They include clouds, cloud shadows, active fire, smoke, snow, and open water. Data gaps in Landsat 7 imagery caused by the failure of the scan-line corrector are also routinely masked.

In the context of RAVG analysis, broad vegetation classes used for spatial analysis of burned area.

Areas designated by Congress as a part of the National Wilderness Preservation System.

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