Seminar: Justine Karst

Carbon in, carbon out? The flow of carbon from fine roots of a deciduous boreal tree into mycorrhizal fungi and soils

Through seasonal gradients in carbon flow from tree canopies to roots, we examined the relationships between leaf phenology and fine root nonstructural carbon concentration, exudation, and colonization by ectomycorrhizal fungi. We found that fine root sugar concentration was low in fall, but otherwise variable across the growing season. Fine root starch concentration was variable in the fall, but otherwise low across the growing season. Fine root carbon exudation was consistently low and root colonization by ectomycorrhizal fungi was variable across seasons. The amount of carbon leaving fine roots, represented by exudation and extent of colonization, did not correspond to leaf phenology. A simple model of ‘carbon in, carbon out’ did not explain the belowground fate of carbon in this trembling aspen forest.