Post-Fire (1983-2024) Boreal Forest Demography, Interior Alaska

As one of the resilient and largest land biomes on Earth, boreal forest (comprising 30% of the global forest area) provides ecosystem services that benefit society at levels ranging from local to global including climate regulations. Nonetheless, stoked by arctic warming, wildfires are remaking the boreal forest. In recent decades’ boreal wildfires' extent and severity increased and reached record levels. In the last two decades (2001-2020: 31.4 million acres) wildfires in Alaska have burned more than twice as many acres than the previous two decades (1981-2000: 14.1 million acres). Severe fires lead to the most extensive regrowth of broadleaf shrubs and trees. Previous studies predict that broadleaf stands, which accounted for less than half of interior Alaska’s forests in 2001, will expand to cover two-thirds of the forested area. Some studies predict forests being permanently replaced by shrubland and grassland. Whatever the new shape of the forest, the change will ripple through wildlife. Given consensus on the value of boreal forest to the climate system, biodiversity, and society, data and policy-driven improvement in forest protection and management is needed. Current and reliable map products and up to date post-fire forest demography will be valuable to new policy formulation to sustain forest cover, and reduce fire risk. Given that fire frequency and severity are expected to increase the prevalence of early-successional broadleaf species, it is particularly important to monitor forest demography to better understand how changing climate conditions and wildfires are affecting overall forest health, resilience, and carbon drawdown. Post-fire forest cover changes from one type to another need to be mapped and documented every 2-5 years to support effective forest protection and management efforts. Satellite imaging provides a consistent, enduring record of the landscape, and repeated imaging has potential to map forest recovery and demography post-fire. In this study, we investigate the post-fire forest demography within select historic burn scars from the 1980s using satellite remote sensing. Our goal is to gain novel insights on post-fire forest recovery and composition i.e. post-fire what percentage of a burn scar is conifer vs broadleaf and how do their composition evolve with time? For a select historic fires from the 1980s, we will employ a time-series analysis of post-fire vegetation recovery by species at 2-5 years interval. We will use peak growing season spectral indices (NDVI, NBR) along with spring (leaf off) images for mapping vegetation by spices. We will use Random Forest image classifier to generate the final vegetation maps and composition statistics. The research will offer novel insights on post-fire forest recovery and composition, and its findings will provide a locally relevant record of forest change by (i) being spatially explicit, (ii) quantifying gross forest loss and gain, and (iii) quantifying trends in forest demography. The derived map products and statistics will empower the U.S. Forest Service, Alaska DNR, and private landowners to take measures for effective management of forest land and resources to sustain ecosystem services benefiting society and climate regulations.