Climate warming and fire in a naïve biome: Using insights from boreal forest to understand causes and consequences of fire intensification in arctic tundra

• Michelle C. Mack

Abstract
Human-caused warming of climate at high northern latitudes appears to be increasing the intensity, frequency and size of wildfires in boreal and arctic tundra biomes. Because >40% of the worlds biological carbon stocks reside in these biomes, intensification of fire could be a strong, positive feedback to climate warming. Although fire has been part of the natural disturbance regime in many regions of the boreal forest, arctic tundra has experienced relatively little fire disturbance in the Holocene. Intensification of fire in arctic tundra represents the introduction of a novel disturbance regime that could reshape the structure and function of arctic ecosystems. The goal of my proposed sabbatical research is to synthesize data from my lab and others to examine controls over an important aspect of fire intensification—fire severity—and identify its consequences for ecosystem structure and function in both boreal and arctic Alaska. I propose to use statistical modeling techniques to address the following questions: (1) What are the important environmental and structural predictors of fire severity at the landscape-scale? (2) What are the consequences of fire severity for emissions of C and N, residual ecosystem C and N pools, organic layer thickness, and mineral soil exposure? (3) How do controls over and consequences of fire severity differ between boreal forest and a naïve biome, arctic tundra? Anticipated products include a publicly available dataset, a peer reviewed manuscript and a workbook for land and fire managers that provides step-by-step instructions for quantifying belowground fire severity in boreal forest and arctic tundra. This research will contribute to the mechanistic understanding of fire severity in high northern latitude systems important for predicting the net feedback of terrestrial ecosystems to a warming climate.