Supervised by:

Line Rochefort (Regular member)

Research project description

Selection and application of phenolic compounds to reduce decomposition of Sphagnum moss

IntroductionStudies showed that phenolic compounds could be effective at reducing decomposition by inhibiting enzymes according to the mechanism called "enzymic latch" (Alshehri, A. et all. 2020; Dunn, C. et Freeman; C. 2018, Fenner, N. et Freeman, C. 2020). The enzymic latch is a concept developed by Freeman, C. et all. (2001) whereby the accumulation of phenolic compounds would explain the slow decomposition in peatland due to their inhibitory role on enzymes. However, there are contradictory results in the literature (Romanowicz, K. J. et all. 2015) and this mechanism is still very new. Therefore, it is important to continue the research in this field. ObjectivesThe aim of this research project is to verify if phenolic compound applications in peatland mesocosms would decrease decomposition and increase biomass accumulation according to the hypothesis that phenolic compounds strengthen the enzymic latch mechanism. Study sitesThis experiment is taking place in a greenhouse at Université Laval, Québec City. However, for the establishment of the experimental units, Sphagnum mosses have been collected in the natural sector of the Pointe-Lebel's peatland. This peatland is a bog of the Côte-Nord in the province of Quebec (49ᵒ8’N, 68ᵒ13’O) and is used for peat extraction activities. Material and methodsThis master thesis project is a greenhouse experiment of four months and is conducted following a completely randomized design. Nine treatments will be tested such as barks from black spruce, white spruce, cedar and larch, barks from black spruce and white spruce soaked in a 10% lignin solution, strawberry leaves, bio-charcoal and a control. Each treatment will be replicated five times for a total of 45 experimental units (EU). An EU is a peat mesocosm created in a bin filled with peat where a Sphagnum carpet has grown, and the water table is kept stable at 10 cm under the peat surface. To verify if the decomposition decreases, carbon flux, such as carbon dioxide and methane, will be taken every two weeks. Enzyme activity will be measured at the beginning and at the end of the experiment. Finally, phenolic content of peat will be taken every two weeks and biomass will be measured at the end of the experiment. ReferencesAlshehri A, Dunn C, Freeman C, Hugron S, Jones T G, Rochefort L (2020) A potential approach for enhancing carbon sequestration during peatland restoration using low-cost, phenolic-rich biomass supplements. Frontiers in Environmental Science, 8(48): 1-8. Dunn C, Freeman C (2018) The role of molecular weight in the enzyme-inhibiting effect of phenolics: the significance in peatland carbon sequestration. Ecological Engineering, 114:162-166. Fenner N, Freeman C (2020) Woody litter protects peat carbon stocks during drought. Nature Climate Change. 10(4):363-369. Freeman C, Ostle N, Kang H (2001) An enzymic 'latch' on a global carbon store. Nature, 409(6817):149-149. Romanowicz K J, Kane E S, Potvin L R, Daniels A L, Kolka R, Lilleskov E A (2015) Understanding drivers of peatland extracellular enzyme activity in the PEATcosm experiment: mixed evidence for enzymic latch hypothesis. Plant and Soil, 397(1-2):371-386.