Due to a history of clear cutting and fire suppression, 2.7 million acres in Washington State require thinning small diameter material in order to decrease fire danger and provide light, water, and nutrient access to the remaining trees. The traditional practice of processing to eliminate the excess woody biomass from forest restoration is burning the material in piles, which sterilize the biological activity in soil, provide habitat for invasive plant species, and off-gas the majority of the carbon held within the wood residue. Transitioning pile burning to charcoal has the potential to increase forest soil health and plant resiliency, improve tree growth rates and the value of timber harvests, and sequester carbon from the atmosphere.
A series of research papers illustrate biochar’s ability to increase forest soil organic carbon stock, porosity, moisture retension, raise soil pH, nutrient retention capacity, and improve biological activity. Specific studies are cited below.
Increasing Soil Carbon Storage
Research on biochar’s role on soil carbon in forest soils illustrate that biochar enhanced the belowground recovery of root derived carbon by 20%, and decreased the release of soil carbon into the air by 5.5%.
Sequestering carbon from woody biomass
converting small diameter material into biochar can mitigate soil carbon loss, with each pound of biomass converting into .56 pounds of carbon dioxide sequestered.
Water holding capacity and Aeration
One study shows biochar to increase water holding capacity by 10% in drought conditions, as well as 12% increased soil aeration at peak moisture saturation. These effects improve tree resiliency in both extended dry and wet weather patterns.
As charcoal holds a residence time in the soil between several hundred years to ten melleniums, these benefits could improve forest health for generations.
 Slash-pile biomass estimations and CarbonCycling in the Coastal Temperate Rainforest of the Pacific Northwest, Winterbourne, 2016
O’Neil et al, 2019. LIFE CYCLE ASSESSMENT OF BIOCHAR FROM POST-HARVEST FOREST RESIDUES. Corrium.