Table 1. Definitions of terms as used in this paper.

Term	Definition
Ponderosa pine andmixed-conifer forests ofWestern North America	Low- to mid-elevation, montane, non-coastal forests of western North America where a regime of low/moderate-severity fire (see Table 2 for explanation) that limit tree recruitment has traditionally been applied. These extensive forests are dominated by ponderosa pine (Pinus ponderosa), Douglas-fir (Pseudotsuga menziesii) and fir (Abies concolor and A. grandis) (see Methods). These forests are drier than coastal forests or most forests at higher elevations, though one region, the Klamath, is more mesic.
Fire dependent	Biota that occur most abundantly after high-severity fire, and which are largely or entirely absent where high-severity fire has not occurred for a long period.
Fire regime	The frequency, size, seasonality, impacts and other characteristics of naturally occurring fires that have occurred in a vegetation type over its lifespan, generally 1–3 millennia [133].
High-severity fire rotation (or moderate to high-severity fire rotation)	The length of time required for an area equal to the area of interest to burn [134]. For high-severity fire, this is calculated as the time period over which high-severity fire (or moderate- and high severity fire combined) is observed, divided by the proportion of the area of interest that burns in that time period at high- or moderate/high-severity.
High-severity fire	Fire that burns on the ground surface, and typically in the overstory canopy (crown fire) as well. Mortality of woody species as measured by basal area is generally >70%. However, sprouting canopy species, such as oaks (Quercus spp.) typically survive these fires. High-severity fire mainly occurs in relatively discrete patches under high winds that cause blow ups in fire behavior [108]. These patches range in size from the area occupied by a small group of trees to many thousands of ha in size, as in the case of the 1910 fires.
Low-severity fire	Fire that burns on the ground surface such that relatively little or no mortality of live, standing vegetation occurs. Mortality of woody species as measured by basal area is 0–20%, but is mostly 0–5%. See Table 2 for a detailed explanation of the effects of a regime of low-severity fire.
Moderate-severity fire	Fire that burns only on the ground surface and that has effects that are intermediate between low- and high-severity fire as defined here. Mortality of woody species as measured by basal area is generally 20–70% within a given area.
Mixed-severity fire	Fire that includes low-, moderate-, and high-severity effects. See Table 2 for a detailed explanation of the effects of a regime of mixed-severity fire.
Park-like forest	A forest of widely-spaced live, mature trees and very few, if any, dead trees (snags). The understory is open, often dominated by bunchgrasses, and is mostly lacking woody plants.
Stand age	The age within a stand of the dominant overstory canopy vegetation that recruited more or less as a cohort, typically after a previous disturbance.

These terms may have different meanings in the literature depending on the context in which they are used.