The fate of soil organic matter in Northern ecosystems - missing pieces in the plant-soil-microbe interactions puzzle

Northern forest and peatland ecosystems store enormous amounts of carbon (C) and nitrogen (N) in the soil organic matter (SOM). Human-induced global warming may shift northern forests and peatlands from a C sink into a C source thereby accelerating the emission of greenhouse gases into the atmosphere. We currently lack a holistic view of SOM transformations, i.e., decomposition or stabilization, which is essential for the prediction of future climate and the implementation of mitigation and adaptation strategies. This project focuses on a new scientific viewpoint with plant-soil-microbe interactions as key mediators of SOM stabilization. With the use of a field study and laboratory studies, I will provide a novel framework on how plant roots regulate SOM decomposition and stabilization through the reaction of plant secondary metabolites with soil microbial residues. This is important especially in plant secondary metabolite-rich northern forests and peatlands, in which such feedback can contribute to the formation of enormous reservoirs of SOM. I will unravel mechanisms, extrapolate them into the future climate using warming and drought experiments and into Northern forests and peatlands globally using an environmental gradient. In this study, I will go beyond the state-of-the-art by a unique combination of plant and soil biochemistry, compound-specific isotope analysis, metagenomics, metatranscriptomics, and ecological modelling.

The improved understanding of SOM decomposition and stabilization at the Northern hemisphere allows more accurate estimation of ecosystem responses to environmental or land-use changes and finds ways to increase soil C sequestration by land management to mitigate the climate change.