Soil organic matter dynamics in boreal forests – the role of mycorrhizal mycelia and microbial communities

Chemical and biological mechanisms underpinning long-term soil carbon storage in boreal forests are poorly known, but a high proportion of stable soil organic matter (SOM) consists of microbial residues.

The aim is to increase our understanding of how ectomycorrhizal (ECM) fungal mycelia and associated microbial communities contribute to long-term stable SOM formation.

The 4-year project is organised in three parts focusing on 1) mycelial decomposition under varying growth conditions, 2) investigations of the chemical quality and community composition of in situ mycelial communities, and 3) quantification of SOM fractions and their associated microbial communities and functions.

We make use of environmental gradients to perform experiments testing how decomposition is affected by fungal traits and environmental conditions, and we collect composite mycelial samples by incubating sand-filled in-growth mesh bags in situ.

Methods include chemical characterization of mycelia using Fourier Transform Infra-Red spectroscopy, SOM fractionations, visualization and elemental analysis using SEM, together with quantification and meta-barcoding of microbial communities, and activity measurements (e.g. enzyme activities).

The project will contribute to the fundamental understanding of links between microbial phylogenetic and functional biodiversity, and SOM dynamics, motivated by a lack of in-depth mechanistic understanding of SOM transformations, and the role of soil microbial communities.