Fuel loads and plant traits as community‐level predictors of emergent properties of vulnerability and resilience to a changing fire regime in black spruce forests of boreal Alaska

Abstract

Black spruce forest communities in boreal Alaska have undergone self-replacement succession following low-to-moderate severity fires for thousands of years. However, recent intensification of interior Alaska's fire regime, particularly deeper burning of the soil organic layer, is leading to shifts to deciduous dominated successional pathways, resulting in many socioecological consequences. Both fuel load quantity and quality (or “burnability”) influence black spruce plant communities' potential to burn. Even relatively low fuel loads, such as those seen in black spruce forest understory, can be highly influential drivers of fire behavior due to their high flammability. Additionally, black spruce community self-replacement following fire can be largely attributed to the suite of functional and life history traits possessed by the species dominating these communities. We used fuel load (quantity and quality) and amount of within-population plant trait variation (coefficient of variation; CV) as community-level emergent properties to investigate black spruce forest vulnerability and resilience to a changing fire regime across the landscape. Our burn severity potential index (BSPI), calculated from fuel load quantity and quality measurements, indicates that drier, higher elevation stands with thicker active layers were the most vulnerable to fire-induced vegetation shifts under a changing fire regime. Forest resilience to fire-induced vegetation shift, represented by higher CV, was negatively associated with BSPI and greatest in ecoregions dominated by lowland black spruce forests. Together, these analyses provide critical information for determining the likelihood of stand-replacing shifts in dominant vegetation following fire and for implementing appropriate ecosystem management practices.

Citation

Grzesik, E. J.; Hollingsworth, T. N.; Ruess, R. W.; Turetsky, M. R. 2022. Fuel loads and plant traits as community‐level predictors of emergent properties of vulnerability and resilience to a changing fire regime in black spruce forests of boreal Alaska. Journal of Geophysical Research: Biogeosciences. 127(3): e2021JG006696. https://doi.org/10.1029/2021JG006696.