Date of Award

4-1-2022

Publication Type

Thesis

Degree Name

M.Sc.

Department

Great Lakes Institute for Environmental Research

Keywords

Agricultural management, Fluorescent spectroscopy, Restoration, Soil organic carbon, Soil organic matter, Water extractable organic matter

Supervisor

C. Proctor

Supervisor

A. Grgicak-Mannion

Rights

info:eu-repo/semantics/openAccess

Abstract

Soil organic matter (SOM) is an important pillar of soil fertility and ecosystem health. However, uncertainty exists both in the evaluation of agricultural conservation measures for specific local contexts and the sensitivity of the analytical tools used. Therefore, the objective of this thesis was to characterize organic matter from agricultural soils, focusing specifically on addressing field- and analytically based uncertainties associated with the ultraviolet-Visible (UV-Vis) and fluorescence spectroscopy of water-extractable organic matter (WEOM), and using the clay-dominated soils of Essex County as a case study. Here I explored optical spectroscopy properties across a gradient of agricultural practices and restoration to evaluate the relationship between land management practice, soil health, and properties of WEOM. Differences between management practices were limited to shallow samples (0-15cm) only and soil organic carbon (SOC) levels in restored sites were nearly twice as high as all agricultural sites. Neither SOC concentration nor WEOM composition differed among the agricultural practices. At all sites, clay-plain soils displayed strong vertical zonation of SOC. Poorly drained shallow A horizon soils accumulated organic matter while deeper impermeable clay mineral horizons with lower concentrations of WEOM took on a more protein-like composition. My results show that reforestation drives increased soil carbon sequestration, but restoration of desired forest SOC composition may require multi-decadal time scales to be achieved. I further explored optical WEOM properties in response to freeze-thaw dynamics and found that absorbance but not fluorescence is more sensitive to freeze-thaws associated with freeze storage as compared to refrigeration. This thesis provided a more nuanced and mechanistic view of soil health beyond SOC accumulation and can help contribute a greater understanding of carbon transformations in agricultural landscapes.

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