Supervised by:

Vincent Maire (Regular member)

Research project description

Assessment of the vulnerability of organic matter to decomposition in northern wetlands in a context of global warming.

IntroductionWetland conservation is a particularly important issue, because they represent both a carbon sink with productive vegetation adapted to redox conditions but also a significant carbon stock worldwide in the form of organic matter trapped in the soil. The increase in temperature envisaged by climate projections could stimulate the degradation of this organic matter leading to an increased emission of carbon dioxide (CO2) to the atmosphere and an amplification of global warming. However, the quality of organic matter trapped in Arctic wetland soils varies according to wetland and is considered recalcitrant. Moreover, it is not clear whether permafrost microorganisms have the enzymatic tools to degrade them. A better understanding of the vulnerability of organic matter to wetland decomposition is therefore necessary to anticipate climate feedbacks.ObjectivesThe objective is to compare the vulnerability of soil organic matter in several wetland types, including marsh, shrub swamp, fens, open fens, and palsas and lithalsas areas. A first component will focus on better quantifying and qualifying these organic matters of the different wetland types. The second component will focus on the risks of these organic matters to decompose with increasing temperature and shrub cover.Study sitesThe study site is located in Kangiqsualujjuaq, Nunavik, specifically in the wetlands surrounding the village. This is an area with discontinuous permafrost. The locations where the samples will be collected are selected based on the habitat types present and already mapped, namely the marsh, shrub swamp, fens, open fens and palsas and lithalsas.Material and methodsFor each of the five wetlands studied, soil samples from four sites will be collected at two depths: one at the surface and a deeper one chosen according to the beginning of the permafrost. Soil samples will be incubated at six temperatures. The respiration of microorganisms will be measured over approximately 80 days to translate the balance of enzymatic activities into CO2 emission. Experiments of enzymatic activities by fluorescence targeting a gradient of chemical complexity of organic matter, field pH and moisture measurements and soil component analyses will be conducted to target factors that affect the different rates of decomposition. In addition, other respiration experiments will be carried out at the same temperature, with treatments such as the presence and absence of exudates from woody plants, which are increasingly present in the north with the increase in temperature.ReferencesBracho, R., Natali, S., Pegoraro, E., Crummer, K., Schädel, C., Celis, G., Hale, L., Wu, L., Yin, H., Tiedje, J., Konstantinidis, K., Luo, Y., Zhou, J. et Schuur, E. (2016). Temperature sensitivity of organic matter decomposition of permafrost-region soils during laboratory incubations. Soil Biology & Biochemistry, 97:1-14. Conant, R., Drijber, R., Haddix, M., Paeton, W., Paul, E., Plante, A., Six, J., et Steinweg, M. (2008). Sensitivity of organic matter decomposition to warming varies with its quality. Global Change Biology, 14:868-877. Georgiou, K., Jackson, R., Vindušková, O., Abramoff, R., Ahlström, A., Feng, W., Harden, J., Pellegrini, A., Polley, H. Soong, J., Riley, W. et Torn, M. (2022). Global stocks and capacity of mineral-associated soil organic carbon. Nature Communications, 13:3797. Henneron, L., Balesdent, J., Alvarez, G., Barré, P., Baudin, F., Basile-Doelsch, I., Cécillon, L., Fernandez-Martinez, A., Christine, H. et Fontaine, S. (2022). Bioenergetic control of soil ca

Research Site Coordinates