Drivers of fire severity in western north American boreal deciduous forests

Black, Betsy (2023) Drivers of fire severity in western north American boreal deciduous forests. Masters thesis, Northern Arizona University.

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Abstract

Boreal forests store a large portion of the Earth’s terrestrial carbon. Recently, warmer temperatures and drought have driven severe wildfires that result in carbon combustion losses that may exceed what can be sequestered by post-fire regrowth. However, these severe fires sometimes initiate shifts from conifer- to deciduous-forest dominance. Deciduous forests sequester more carbon for longer than the black spruce forests they replace because they accumulate combustion-resistant aboveground biomass more rapidly. However, as the climate of boreal ecosystems continues to warm, it is uncertain if the relative resilience of deciduous trees to wildfire will persist. To understand what a more deciduous boreal forest means for the future of boreal carbon, we quantified carbon combustion and investigated drivers of fire severity in deciduous and mixed conifer-deciduous stands. We sampled 139 plots across eight fire scars in Alaska and the Yukon. We assessed the relative influence of bottom-up variables related to stand composition and top-down climate variables on wildfire carbon combustion. On average, deciduous stands lost half as much carbon to wildfire combustion as conifer stands lost. Pre-fire fuel loads and vegetation stress were the primary controls on fire severity in mixed and aspen stands, whereas birch stand combustion was additionally influenced by spring precipitation. Our findings suggest that if deciduous tree dominance increases, carbon emissions from boreal wildfires will decline substantially, though wildfire carbon emissions from come deciduous forests may increase if climate change makes precipitation more stochastic in the far north.

Item Type:	Thesis (Masters)
Publisher’s Statement:	© Copyright is held by the author. Digital access to this material is made possible by the Cline Library, Northern Arizona University. Further transmission, reproduction or presentation of protected items is prohibited except with permission of the author.
Keywords:	boreal; carbon sequestration; deciduous; fire severity; forest ecology; wildfire
Subjects:	Q Science > QK Botany
NAU Depositing Author Academic Status:	Student
Department/Unit:	Graduate College > Theses and Dissertations College of the Environment, Forestry, and Natural Sciences > Biological Sciences
Date Deposited:	24 Oct 2025 00:00
Last Modified:	24 Oct 2025 00:00
URI:	https://openknowledge.nau.edu/id/eprint/6277

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