Wildfire Influence Impacts on Carbon Storage in Arctic Tundra


Fernanda Santos1* (santosf@ornl.gov), Amy Breen2, Colleen Iversen1


1Oak Ridge National Laboratory, Oak Ridge, TN; 2University of Alaska–Fairbanks, AK



Understanding the impacts of novel wildfire regimes on soil carbon (C) storage and fluxes is critical to improve the ability to predict the vulnerability of Arctic systems to disturbances. Increased wildfire activities reported in the Arctic can disrupt vegetation-soil dynamics and accelerate carbon dioxide (CO2) emissions to the atmosphere, thereby increasing the vulnerability of permafrost C. Repeated burns and time since last fire are important when considering the response trajectory of ecosystems, especially when and under what conditions soils are a net C source or sink. The objective of this research is to measure the effects of fire frequency and time since last fire on soil C stocks and CO2 efflux rates from an Arctic tussock tundra ecosystem. Researchers hypothesize that stocks and fluxes will be more affected by repeated burning than by time since last burning, with more frequent burning leading to decreased total C stocks but increased fire-derived (pyrogenic) C stocks. Pyrogenic C is more stable in soil compared to bulk soil C and is considered an important carbon sink. The team also hypothesize that an increase in fire frequency will decrease CO2 flux rates from soils. In 2022, researchers measured organic layer thickness and thaw depth, and sampled organic layers from the Kougarok fire complex near Nome, AK from unburned sites and sites burned at different years (1971 and 2002) and more than once (twice: 2002 and 2019; three times: 1971, 2002, and 2019; and four times: 1971, 1997, 2002, and 2015). Organic layer samples were dried, ground, and will be analyzed for total elemental C and pyrogenic C. Researchers will present results for C stocks across the different fire treatments at Kougarok fire complex and the plan for soil CO2 efflux measurements at those sites in summer 2023.