Paradigm shift in the view of ectomycorrhizal symbiosis in boreal forest - but in which direction?

Does forestry contribute to increased greenhouse gas emissions or is it a useful tool in mitigation of climate change?

Much of the debate revolves around the choice of silvicultural method, especially if clear-felling followed by planting or seeding should be replaced by selective felling (e.g., continuous-cover forestry) and natural regeneration.It is crucial to consider the interactions between soil nitrogen supply and the function of the mycorrhizal symbiosis between trees and fungi in this context.

Research by us and our colleagues have revealed an unexpected role of mycorrhizal fungi as immobilizers of N in N-poor boreal forests in particular.

Under these conditions, the trees allocate relatively more C to roots and mycorrhizal fungi, which retain much N from their own use and export less to the tree canopies.

This explains the observation in practical forestry of the need for larger gaps to obtain successful regeneration of tree seedlings on N-poor soils.Here, we want to further explore the physiological responses of mycorrhizal mycelium.

We will employ a method, which allows the analysis of effects of natural variations in soil N supply and amendments of N on the growth and immobilization of N by the mycorrhizal mycelium.

We will use a combination of state-of-the-art isotopic and molecular techniques applied directly in the field, which is important to provide an informed and relevant basis for decision on choice of silvicultural method in practical forestry.