Fire-derived charcoal might promote fine root decomposition in boreal forests

Abstract Boreal forest soils are a huge carbon sink, but the forests are regularly subjected to fire disturbance. The fine roots in these forests substantially contribute to soil carbon accumulation. Charcoal is a fire by-product that influences ecosystem processes including soil organic matter decomposition. However, the extent to which charcoal affects fine root decomposition is unclear. We performed field litterbag experiments over 515 days involving the incubation of fine larch roots with varying concentrations of charcoal in soil. At the end of experiment the loss of root mass in samples incubated with higher concentrations of charcoal was greater (42% and 40%) than that in the control (30%) and a treatment containing the average measured soil charcoal content (27%). The degree of mass loss generally increased with increasing charcoal content. Our result provides the first field evidence that fire-derived charcoal may enhance the decomposition of fine larch roots, and consequently CO 2 release from boreal forests.