Dr Nicolas Valette1,2, Dr Eric Gelhaye2, Dr Gry Alfredsen3, Dr Barry Goodell4, Dr Delphine Derrien1
1INRA, Biogeochemistry of Forest Ecosystems, Nancy, France, 2INRA-Lorraine University, Interactions Arbres Micro-organismes, Nancy, France, 3Norwegian institute of bioeconomy reseach, As, Norway, 4University of Massachusetts, Departement of microbiology, Amherst, USA
Forest soils represent a third of the terrestrial area and have a key role in carbon cycle and climate mitigation, as they store between 50 and 80% of the global stock of soil organic carbon (SOC). The major precursor of forest SOC is the dead wood mainly composed by three polymers: cellulose, hemicellulose and lignin. In coniferous forest, they are recycled mainly by brown rot fungi and specific bacterial communities. Brown rot fungi are able to mineralize polysaccharidic part and only modify the lignin chemically using hydroxy radicals in a mediated-Fenton reaction. Some recent findings suggest that the associated bacterial communities could be responsible for the degradation of the persisting altered lignin residues.
According to the Home Field Advantage theory the decomposition rate is more rapid and efficient when litter is placed beneath the natural plant species than beneath a different plant species. We hypothesize that the specific bacterial communities, which co-occur with brown rot are important for the velocity and efficiency of lignin degradation. Therefore, microbial communities from a broadleaf stand would be less efficient than coniferous communities. To test this hypothesis, wood blocks from Poplar, Norway spruce and Beech were pre-degraded by Gloeophyllum trabeum a brown rot fungus. When mass loss reached around 25 %, they were buried under litter layer either in a Norway spruce stand or a Beech stand. After 6 months, wood blocks will be collected. Wood mass loss and chemical changes will be assessed. Moreover, a metabarcoding approach will be performed to determine the microbial communities potentially responsible for wood degradation. These results could be translated into recommendations for forest management to optimize soil carbon sequestration under altered lignin form.