What Constitutes a Natural Fire Regime? Insight from the Ecology and Distribution of Coniferous Forest Birds in North America

Richard L Hutto,Courtney J Conway,Jeffrey R Walters,Victoria A Saab

doi:10.4996/fireecology.0402115

Abstract

Bird species that specialize in the use of burned forest conditions can provide insight into the prehistoric fire regimes associated with the forest types that they have occupied over evolutionary time. The nature of their adaptations reflects the specific post-fire conditions that occurred prior to the unnatural influence of humans after European settlement. Specifically, the post-fire conditions, nest site locations, and social systems of two species (Bachman’s sparrow [Aimophila aestivalis] and red-cockaded woodpecker [Picoides borealis]) suggest that, prehistorically, a frequent, low-severity fire regime characterized the southeastern pine system in which they evolved. In contrast, the patterns of distribution and abundance for several other bird species (black-backed woodpecker [Picoides arcticus], buff-breasted flycatcher [Empidonax fulvifrons], Lewis’ woodpecker [Melanerpes lewis], northern hawk owl [Surnia ulula], and Kirtland’s warbler [Dendroica kirtlandii]) suggest that severe fire has been an important component of the fire regimes with which they evolved. Patterns of habitat use by the latter species indicate that severe fires are important components not only of higher-elevation and high-latitude conifer forest types, which are known to be dominated by such fires, but also of mid-elevation and even low-elevation conifer forest types that are not normally assumed to have had high-severity fire as an integral part of their natural fire regimes. Because plant and animal adaptations can serve as reliable sources of information about what constitutes a natural fire regime, it might be wise to supplement traditional historical methods with careful consideration of information related to plant and animal adaptations when attempting to restore what are thought to be natural fire regimes.

Highlights

(Pinus ponderosa) vegetation type and are dominated by mixed- and high-severity fires rather than lowseverity fires. This fact is not widely appreciated, and is not the picture of natural fire regimes propagated by the popular press, from which one gets the impression that most western forest types historically burned frequently and only at low severity
We attempt to show how a consideration of biological information, information related to bird distribution and reproductive success in relation to environmental conditions, can provide insight into what constitutes a natural fire regime for any given system
Species that seldom occur outside recently burned forests can be confidently classified as fire specialists, with extreme fire specialists being those species that are entirely restricted to forest conditions created by fire

Summary

Ponderosa Pine System

Frequent surface fires are thought to have characterized the dry, warm woodlands and open-canopy ponderosa pine forests of the American southwest and the more xeric low-elevation ponderosa pine forests elsewhere (Schoennagel et al 2004). The bird species that appear to be most restricted to and, most dependent upon, burned forests in these systems (blackbacked woodpecker, and northern hawk owl) clearly require severe fires This is entirely consistent with our current understanding that infrequent, severe fires dominate fire regimes in the boreal conifer forest system (Johnson et al 2001), and it reinforces the idea that the extensive mixed-conifer forest zones throughout the western US were probably historically dominated by mixed-fire regimes that included either some infrequent severe fire events or, more likely, always included patches of severe fire during fire events that occurred at intermediate frequencies. This conclusion corresponds well with the fact that mixed- and high-severity fire regimes characterize the majority (see data from LANDFIRE) of forest types in North America (Johnson et al 2001, Graham 2003, Franklin et al 2005, Noss et al 2006), including even the more mesic ponderosa pine forests (Schoennagel et al 2004, Baker et al 2007, Sherriff and Veblen 2007)

Jack Pine System

Southeastern Pine System

Findings

Management Implications