Fire and Mechanical Forest Management Treatments Support Different Portions of the Bird Community in Fire-Suppressed Forests

Abstract

Silvicultural treatments, fire, and insect outbreaks are the primary disturbance events currently affecting forests in the Sierra Nevada Mountains of California, a region where plants and wildlife are highly adapted to a frequent-fire disturbance regime that has been suppressed for decades. Although the effects of both fire and silviculture on wildlife have been studied by many, there are few studies that directly compare their long-term effects on wildlife communities. We conducted avian point counts from 2010 to 2019 at 1987 in situ field survey locations across eight national forests and collected fire and silvicultural treatment data from 1987 to 2016, resulting in a 20-year post-disturbance chronosequence. We evaluated two categories of fire severity in comparison to silvicultural management (largely pre-commercial and commercial thinning treatments) as well as undisturbed locations to model their influences on abundances of 71 breeding bird species. More species (48% of the community) reached peak abundance at moderate-high-severity-fire locations than at low-severity fire (8%), silvicultural management (16%), or undisturbed (13%) locations. Total community abundance was highest in undisturbed dense forests as well as in the first few years after silvicultural management and lowest in the first few years after moderate-high-severity fire, then abundance in all types of disturbed habitats was similar by 10 years after disturbance. Even though the total community abundance was relatively low in moderate-high-severity-fire habitats, species diversity was the highest. Moderate-high-severity fire supported a unique portion of the avian community, while low-severity fire and silvicultural management were relatively similar. We conclude that a significant portion of the bird community in the Sierra Nevada region is dependent on moderate-high-severity fire and thus recommend that a prescribed and managed wildfire program that incorporates a variety of fire effects will best maintain biodiversity in this region.

When bigger isn’t better—Implications of large high‐severity wildfire patches for avian diversity and community composition

“…If reestablishment of conifer or hardwood trees is successful and in the absence of repeated severe disturbance, the habitat will transition back to a forested state in the medium to long term (Agee, 1996; van Wagtendonk et al., 2018). In contrast, low‐ to moderate‐severity effects reduce tree and understory density but maintain mature canopy cover (Miller et al., 2009) and habitat structure more similar to unburned areas (Roberts et al., 2021). Many bird species in the Sierra Nevada, California are adapted to particular combinations of burn severity and time since fire, including early‐successional habitats created by high‐severity fire (Fontaine et al., 2009; Taillie et al., 2018; White et al., 2016).…”

“Forest fire emissions: A contribution to global climate change”

“…There is a need for a new indebtedness for what we are calling "pyrodiversity, " or the wide dissimilarity in the effects and fire responses (Roberts et al, 2021). Measuring spatiotemporal fire systems has many inaccuracies, a huge range of variation, and very little accuracy (Reinhardt et al, 2008;DellaSala et al, 2022), more studies are required for the full gradient of fire's effects.…”