Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Master of Science

Program

Geology

Collaborative Specialization

Environment and Sustainability

Supervisor

Webb, Elizabeth

Abstract

Soil organic carbon (SOC) enhances nutrient retention, structural stability, porosity, aeration, water infiltration, and overall soil health. Understanding SOC turnover and its preservation in soils is paramount to managing carbon sequestration. On Pelee Island, we used δ13C, δ15N and C/N of SOC at various depths to identify the sources and evolution of SOC with time. At depths >150 cm, SOM was from a mixture of aquatic and terrestrially derived sources. We also analyzed the impact of permanent cover crops called ‘resident vegetation’ on the ability of soils to store carbon in different aggregate size fractions. SOC increased with increasing duration of resident vegetation in each aggregate fraction. Under prolonged resident vegetation we found a greater proportion of new carbon stored in the smallest and most resilient aggregate fraction (mm). These results are significant for measuring carbon capture at the Pelee Island winery, necessary for obtaining agricultural carbon credits.

Summary for Lay Audience

Regenerative farming is a holistic approach to agriculture which strives to rebuild healthy soils and make agriculture more sustainable. At the core of regenerative farming are management techniques such as cover cropping and reduced tillage, which add more soil organic carbon to soils. The government of Canada has proposed a carbon credit system to incentivize the use of regenerative farming to increase carbon in soils, offsetting greenhouse gas emissions. To implement such a system requires a robust method of quantifying carbon stock in soils, and subsequent changes under different soil management techniques. Quantifying carbon changes requires a detailed understanding of how carbon cycles in soils, how it is preserved with time, and how it is lost. On Pelee Island, we studied different forms of carbon and nitrogen at various depths in the soil to characterize how older forms of soil organic matter, deeper in the soil, changed with time. We concluded that soil organic carbon deep in the soils of Pelee Island, originated from a mixture of terrestrial plants, and aquatic sources, which were deposited in a post glacial-lake environment.

In a separate yet related portion of our study, we examined the effect of permanent cover crops called ‘resident vegetation’. Our objective was to establish whether soil organic carbon increased under resident vegetation and if so, whether carbon was added to the soil in stable fractions which were resistant to degradation/volatilization or loss from the system. Our work showed that, with increasing duration of resident vegetation, soil organic carbon increased considerably in all fractions of the soil, stable and labile. These results will be crucial in obtaining carbon credits, but also guiding future management towards more sustainable agriculture at the Pelee Island Winery.

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