2024 Abstracts

Impacts of Wildfire on Arctic Shrub Expansion


Zelalem A. Mekonnen1* ([email protected]), William J. Riley1, Robert F. Grant2, Colleen Iversen3


1Lawrence Berkeley National Laboratory, Berkeley, CA; 2Department of Renewable Resources, University of Alberta, Edmonton, Canada; 3Oak Ridge National Laboratory, Oak Ridge, TN



Northern high-latitude regions have experienced rapid warming and more frequent and intense wildfire in recent decades. These changes contribute to a complex set of soil-plant-atmosphere interactions, potentially altering competitive interactions, plant species composition and abundance, and ecosystem carbon stocks. Increases in woody plants, particularly tall deciduous shrubs, have been observed across much of the Arctic tundra region. However, the role wildfire plays on observed shrub expansion is uncertain. Here, the team applied a process-rich ecosystem model, ecosys, to examine changes in tundra shrub growth driven by wildfire across Alaska.

After thoroughly evaluating model simulations against site observations and data-driven regional products, researchers found that the impact of wildfire on Arctic shrub growth is spatially heterogeneous. The team modeled that changes in soil moisture postfire are a key factor that controls successful establishment and relative competitiveness of shrubs. Fire generally enhances the growth of shrubs in areas that are sufficiently drained and have optimal soil moisture versus in areas with postfire saturated conditions. The project shows that postfire deepening of the active layer, driven by warmer soil, accelerates nutrient cycling. Further, changes in soil moisture regime control trajectories of shrub growth and their ability to compete with herbaceous plants under increased wildfire and climate warming.