Fire-derived charcoal affects fine root vitality in a post-fire Gmelin larch forest: field evidence

Abstract

Fine roots are only a small part of total ecosystem biomass, but substantially contributing to soil carbon accumulation in boreal forests. Wildfires may influence fine root dynamics directly via heating and indirectly via interactions with wildfire-deposited charcoal. We tested if the presence of charcoal in a recently burned larch forest affected fine root vitality. This study was stratified across vegetation type (understorey and overstorey), soil depth (upper and lower layers), and root diameter classes: fine (≥0.5 mm but <2 mm diameter), and very fine (diameter < 0.5 mm) in a recently surface-burned Gmelin larch (Larix gmelinii (Rupr.) Rupr.) forest in the Russian Far East. Charcoal content and fine root vitality were positively correlated for overstorey vegetation, but negatively correlated for understorey vegetation. On the other hand, total charcoal content did not significantly correlate with very fine root vitality, biomass or necromass. Our study provides the first field evidence that fine root dynamics are influenced by fire-derived charcoal in frequently burned boreal forest. Furthermore, the effect of charcoal on fine root vitality depends on the vegetation type, root diameter, and soil depth, which indicates the necessity of complicated modeling of soil organic carbon derived from fine roots in post-fire boreal forests.