Implications of an Intensified Fire Regime Across Interior Alaska's Spatiotemporal Black Spruce Dominated Landscape: Relationships Among Plant Diversity, Functional Traits and Fire

Black spruce dominated plant communities in interior Alaska have been adapted to a low to moderate severity fire regime for thousands of years. The species composition and the occurrence of fire ecological plant traits within these communities is essential to the resilience of the ecosystem to fire. However, recent climate-related increases in warming and drying have resulted in a shift in interior Alaska's fire regime towards larger, more frequent and more severe fires. This intensified fire regime likely increases the susceptibility of boreal forests to shift from black spruce dominated to deciduous dominated communities, which would lead to widespread ecosystem impacts. Little is known about the quantity and quality of understory fuel loads present in these communities and how these understory fuels influence the potential for these communities to burn at high severities in the future. This study investigates the variability in phenotypic plasticity of fire-adaptive and fire-resistive plant traits and provides a quantification of understory (shrub, forb, and non-vascular) fuel loads in a subset of black spruce dominated sites from the Bonanza Creek Long-Term Ecological Research regional site network. These sites range across gradients of age (time-since-fire), site-moisture and previous burn severity. Trait plasticity was measured for Vaccinium uliginosum and Hylacomium splendens, two very ubiquitous species present within these sites. We asked whether variability in species trait plasticity is correlated to a site's previous burn severity, or more tightly linked to environmental gradients such as site moisture. Additionally, we measured understory vegetation and soil organic biomass to correlate fuel loads with percent cover data that has been collected at these sites. Investigation of patterns between fuel load and plant percent cover may reveal that these emergent properties can be used to indicate the potential of a site to reburn. Lastly, these results will be applied to a framework that can be used by fire managers to assess a community's ability to reburn based on site characteristics, plant composition and fuel load. The findings of this study will highlight the vulnerability of boreal black spruce dominated landscapes to severe burning and the ability of them to remain resilient to fire as a whole.