Researchers propose ectomycorrhizal fungi’s role to be integrated into carbon accounting

Researchers from the University of Helsinki, Natural Resources Institute Finland and Swedish University of Agricultural Sciences propose that the role of the ectomycorrhizal fungi should be taken into account in models of carbon accounting.

A new study led by the University of Helsinki provides evidence that the observed decline of carbon use efficiency and net ecosystem exchange from south to north in the boreal forest may be caused by the abundance of ectomycorrhizal fungi. 

The proposed approach could easily be included in carbon balance models for quantifying ectomycorrhizal fungi carbon use without having to engage in more complex analysis of carbon and nutrient interactions underlying ectomycorrhizal fungi processes. 

“The results of the study underline the need for a better understanding of the role of micro-organisms as users of carbon but also as a machinery generating carbon residues that may have longer lifespans,” says the first author of the study Annikki Mäkelä from theFaculty of Agriculture and Forestry, University of Helsinki. 

The study suggests that this approach can improve prediction of biomass growth across different soils with different microbial composition.  

More accurate prediction of biosphere carbon sinks

According to researchers these features of ectomycorrhizal fungi as carbon consumers and litter producers should also be incorporated into global vegetation models in order to have more precise and accurate prediction of biosphere carbon sinks and their feedbacks to climate change.  

Carbon use efficiency, i.e., the ratio between net and gross primary production, describes the efficiency of vegetation to accumulate photosynthetic carbon to biomass. Other uses of carbon include maintenance and construction respiration. In this study, ectomycorrhizal fungi were included as additional consumers of plant-originating carbon.  

Original article

Mäkelä A., Tian X., Repo A., Ilvesniemi H., Marshall J., Minunno F., Näsholm T., Schiestl-Aalto P., Lehtonen A. 2022. Do mycorrhizal symbionts drive latitudinal trends in photosynthetic carbon use efficiency and carbon sequestration in boreal forests? Forest Ecology and Management 520:120355, September 2022, DOI: 10.1016/j.foreco.2022.120355 

Researchers' contact info: 
What are ectomycorrhizal fungi?

Ectomycorrhizal fungi (ECM) are mutualistic fungi that typically cover fine roots of trees. ECM form a symbiotic relationship with the tree.  Unlike other mycorrhiza, ECM do not penetrate the cell membranes of tree roots, but form a dense hyphal sheath (i.e., mantle) around the root surface and a network of hyphae inside the root as well as a dense network of hyphae extending out from the mantle. ECM help the tree to acquire nutrients, water and minerals. In exchange, the tree provides significant amounts of carbohydrates for ECM.