Charcoal ecology: Its function as a hub for plant succession and soil nutrient cycling in boreal forests

We summarize current knowledge about the ecosystem functions of fire-produced charcoal in boreal forests with a special focus on its effects on soil carbon, nitrogen and phosphorous dynamics as well as on plant succession. Charcoal is a carbon-enriched material with a highly aromatic and porous structure. Charcoal is highly resistant to microbial decomposition and thus remains in soil for thousands of years, providing recalcitrant carbon to boreal forest soils. The abundant pores in and on charcoal surfaces have powerful adsorption abilities that can influence biogeochemical cycles and plant succession after fire. Our review details the influence of charcoal on plant and soil systems and explains the complex direct and indirect pathways of these influences that occur during succession after fires in boreal ecosystems. Among these pathways, the most important pathway through which charcoal influences plant and soil systems relates to the element composition and nutrient availability in soils and to the abundance of phenolics released fromEricaceaeplants in the understory of boreal forests. We found a strong bias in the studied processes towards nutrient mineralization rather than immobilization, which suggests that it is risky to draw general conclusions about the influence of charcoal on soil nutrient dynamics. Last, the latest studies shed light on the enhancement of litter and humus decomposition by charcoal, given the possibility that charcoal accelerates CO(2)release in a postfire forest. This review suggests comparative studies that are necessary to test the context-dependency of charcoal functions across a variety of boreal forest ecosystems