Ecosystem carbon emissions from 2015 forest fires in interior Alaska

Area of Science:

• Ecology
• Forestry
• Soil Science

Background:

• Alaska experienced extensive wildfires in 2015, burning over 1.6 million hectares of boreal forest and wetlands.
• Landsat imagery revealed approximately 60% of the burned area experienced moderate-to-high severity.
• Field studies were conducted near Tanana to validate Landsat burn severity classes.

Purpose of the Study:

• To investigate the impact of boreal forest fires on soil properties and carbon loss.
• To quantify changes in soil temperature, thaw depth, and carbon content following severe burns.

Main Methods:

• Field measurements were taken in burned and unburned forest sites near Tanana.
• Soil temperature profiles were recorded to a depth of 30 cm.
• Soil samples were analyzed for carbon and nitrogen content.

Main Results:

• Loss of surface organic layers significantly influenced post-fire soil temperatures and thaw depth.
• Burned sites showed average soil temperature increases of 8-10°C compared to unburned sites.
• Severely burned sites had a 65% reduction in soil carbon and a 58% reduction in soil nitrogen.

Conclusions:

• Boreal forest fires in Alaska lead to substantial carbon and nitrogen loss from the mineral soil layer.
• Total ecosystem carbon loss to the atmosphere likely exceeds previous estimates due to mineral soil decomposition and mass wasting.
• The 2015 Alaskan wildfires had a significant, long-term impact on ecosystem carbon stores.