Thesis Defence: Floodplain organic-carbon dynamics modulated by meandering-channel migration: Vermilion River, Ontario, Canada

Melissa Barrera, supervised by Dr. Alessandro Ielpi, will defend their thesis titled “Floodplain organic-carbon dynamics modulated by meandering-channel migration: Vermilion River, Ontario, Canada” in partial fulfillment of the requirements for the degree of Master of Science in Earth and Environmental Sciences.

An abstract for Melissa Barrera thesis is included below.

Defences are open to all members of the campus community as well as the general public. Registration is not required for in person defences.

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ABSTRACT

Floodplains are important organic carbon (OC) storage sites, and the evolution of watercourses modulates the transport, burial, and reworking of organic matter with cascading effects on watershed CO2 budgets. The migration of adjacent channels can transport and bury OC that is then preserved in reducing environments. If OC is later exposed subaerially, it undergoes oxidation by reacting with oxygen – a reaction that de facto reverses photosynthesis and releases carbon dioxide (CO2) back into the atmosphere. Imbalances between burial and oxidation can modulate watershed CO2 budgets, such that it is important to establish models of OC sequestration and export by rivers. Meandering rivers have broadly predictable patterns of channel-planform evolution, providing an opportunity to assess floodplain OC budgets in relation to characteristic migration paces and floodplain ages. However, complexities associated with the natural geomorphic variability of meandering rivers has delayed the assessment of quantitative relationships between channel and OC dynamics. We illustrate evolving OC budgets in relation to channel migration in the Vermilion River (Ontario) located in the boreal forest of eastern North America. We combine photogrammetric analyses and dynamic time warping of channel centrelines with analysis of top-soil bulk density and OC. We found that variations of OC stock per unit surface area and soil development are modulated by meander migration through the development of typical boreal-forest vegetation successions. Furthermore, we explained the observed dependency of channel migration rate to integration timescale in terms of occasional occurrence of migration reversals, imprecisions in imagery’s georeferencing, and intermittent bankfull discharge stages. Our results provide a quantification of the degree to which meander migration controls soil development, forest age, and floodplain OC budgets over characteristic timescales related to meander growth and abandonment. We anticipate our study to inform wider applications to rivers in different bioclimates – an approach that may in turn help carbon assessment in the context of changing climate or land use.