Biochar Amendments to Forest Soils: Effects on Soil Properties and Tree Growth

Bioenergy production from forest biomass offers a unique solution to reduce wildfire hazard fuel while producing a useful source of renewable energy. However, biomass removals raise concerns about reducing soil carbon (C) and altering forest site productivity. Biochar additions have been suggested as a way to mitigate soil C loss and cycle nutrients back into forestry sites; yet, little is known about the effects of intentional biochar amendments to temperate forest soil in conjunction with biomass removals for bioenergy production. This research evaluates the potential environmental implications of biochar application in forests by examining: (1) the potential for mobile bioenergy and biochar co-production systems in forests, (2) the influence of biochar and biochar application method on standard forest soil properties of three Inland Northwest soils, and (3) the effects of biochar and biochar application rate on poplar growth (a cultivar of Populus trichocarpa Torr. & Gray) in various forest soils. The results indicate that biochar contributes to notable short-term soil chemical alterations associated with blending the properties of biochar with those of various soil types, but the nature and scope of the alterations vary by soil type and application method. The soil nutrient alterations do not appear to affect tree growth in the short-term, as biochar had a neutral main effect on poplar growth. These results suggest that biochar produced from bioenergy production could be returned to forest soils to replenish soil nutrient stocks and enhance C storage, with little to no affect on tree growth in the short-term. Results from these studies provided a basic understanding of the potential for biochar in our region, and offer several primary implications for biochar management that could contribute to a comprehensive plan for continuing forest bioenergy production systems