Supervised by:

Vincent Maire (Regular member)

Research project description

Role of plant communities on organic carbon accumulation in Arctic soils in the Qarlikturvik Valley on Bylot Island, Nunavut

IntroductionClimate change is having an increasingly significant impact on the environment and can lead to major changes in ecosystem functioning, particularly in Arctic soils. Among other things, we observe an increase in the average temperature of the Arctic that is nearly four times faster than the rest of the globe (Rantanen et al. 2022). This increase can have direct effects on various ecosystems such as soil and indirect effects such as increased productivity, density and distribution of plant communities in these environments (Cadieux et al. 2008). Such ecosystem-level changes can potentially influence organic carbon stocks in Arctic soils, and the extent to which indirect effects through changes in plant communities can influence soil carbon storage is not well-known at this time.ObjectivesThe main objective of this project is to determine the functional traits of plant communities that are associated with organic carbon accumulation in Arctic soils, particularly in two categories of organic matter: particulate (POM) and mineral-associated (MAOM). The other objectives are to determine the quality, quantity of organic matter and carbon composition of these two categories as well as those of the microbial and root biomasses. Also, in order to study and separate direct environmental effects (e.g., soil temperature and moisture) from indirect effects through changes in plant communities on soil carbon stocks in the Arctic tundra, track analyses will be used.Study sitesThe study site is located in Nunavut in the Qarlikturvik Valley on Bylot Island (Sirmilik National Park). This site was established in 2002 and is characterized by a hydrological gradient and a nitrogen and phosphorus fertilization gradient. In addition, grazing pressure is exerted on this site by Snow Geese.Material and methodsSamples of the top 20 cm of the active soil layer will be taken at previously established stations at the study site in order to determine variations in organic carbon storage along the different gradients. Soil moisture, temperature, pH and conductivity measurements will also be taken before, during and after sampling. Samples will be frozen for analysis upon return. These analyses include, following the separation of organic matter categories, isotopic characterization and quantification of these categories and root and microbial biomass. Functional traits will be selected according to their ability to modify the storage of organic carbon in the soil either by promoting its accumulation (e.g. leaf area index or LAI), its mineralization (e.g. nitrogen demand) or its distribution in the soil (e.g. root density).ReferencesCadieux, M. C., Gauthier, G., Gagnon, C. A., Bêty, J., Berteaux, D., & Lévesque, E. (2008). Monitoring the environmental and ecological impacts of climate change on Bylot Island, Sirmilik National Park. Université Laval, Report, Quebec, Canada. Henneron, L., Kardol, P., Wardle, D. A., Cros, C., & Fontaine, S. (2020). Rhizosphere control of soil nitrogen cycling: a key component of plant economic strategies. New Phytologist, 228(4), 1269-1282. Luo, T., Pan, Y., Ouyang, H., Shi, P., Luo, J., Yu, Z., & Lu, Q. (2004). Leaf area index and net primary productivity along subtropical to alpine gradients in the Tibetan Plateau. Global Ecology and Biogeography, 13(4), 345-358. Rantanen, M., Karpechko, A. Y., Lipponen, A., Nordling, K., Hyvärinen, O., Ruosteenoja, K., ... & Laaksonen, A. (2022). The Arctic has warmed nearly four times faster than the globe since 1979. Communications Earth & Environment, 3(1), 1-10.

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