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Table 2 Fire regime groups (FRG) used in characterizing unburned islands within fires in the Inland Pacific Northwest from 1984 to 2014. Adapted from Malesky et al. 2018

From: Characterizing persistent unburned islands within the Inland Northwest USA

Fire regime

Frequency

  

Example cover type from

group

(yr)

Severity

Severity description

study area

I

0 to 35

Low or mixed

Generally low-severity fires replacing less than 25% of the dominant overstory vegetation; can include mixed-severity fires that replace up to 75% of the overstory (typical of perennial grasslands)

Ponderosa pine; dry mixed conifer forest

II

0 to 35

Replacement

High-severity fires replacing greater than 5% of the dominant overstory vegetation (annual grasslands and some forests with frequent surface fires)

Grassland

III

35 to 200

Mixed or low

Generally mixed severity; can also include low-severity fires (many forests and shrublands)

Big sagebrusha, lodgepole pineb

IV

35 to 200

Replacement

High-severity fires (forests and shrublands)

Big sagebrush, lodgepole pine

V

≥200

Replacement or any severity

Generally, replacement severity; can include any severity type in this frequency range (some moist forests, tundra, and deserts)

Very sparse big sagebrush steppe; spruce–fir forest

  1. a(Artemisia tridentata Nutt.)
  2. b(Pinus contorta Douglas ex Loudon)