Exploring Successional Dynamics and Permafrost Thaw Post-Fire in Siberian Arctic Boreal Forest

Abstract:

Boreal forests are the largest forest biome on the planet, and a major factor affecting the Earth’s carbon cycle. However, these systems are warming at a rate nearly twice as rapid as the rest of the planet. One consequence of this warming is a projected increased rate of wildfire in northern forests. Open questions in this area are whether increased fire disturbance and warming may lead to conversion to shrub and grass dominated landscapes, and how these events impact the permafrost. In this study, we combined Landsat multispectral imagery and field data across six fires in the along the Kolyma River, in the Siberian Arctic. These fires ranged a time-span of 20 years to 4 years post-fire at the time of our study. Specifically we sought to explore 1) what factors influence rate of vegetation regeneration post-fire as measured by a time series of Normalized Burn Ratio (NBR), 2) if remotely sensed indices could provide insight into type of vegetation community, and 3) whether we could accurately model factors influencing permafrost thaw in burned areas. We found that rate of regeneration was most rapid in the first 5 years post-fire, however this was mostly driven by shrub and grass colonization. Rate of regeneration was significantly affected by burn severity, which affected observed NBR throughout the time series. Permafrost thaw was also positively correlated with burn severity and with distance into the burn scar. We expect to find remotely sensed indicators which are correlated with tree recruitment, to differentiate between shrub and grass vs forest dominated succession on the landscape.