Date of Award

Spring 5-5-2025

Document Type

Thesis

Degree Name

Bachelor of Arts

Department

Biology

First Advisor

Siobhan Fennessy

Abstract

Historically, wetlands in the Glaciated Interior Plains (GIP) have been drained to make room for agriculture, causing a loss of the many ecosystem benefits wetlands provide. To combat this loss, the USDA developed conservation programs to restore wetlands, including the Conservation Reserve Program (CRP). The benefits of CRP wetlands have not been well documented, nor has their potential to mitigate climate change been evaluated. Therefore, we measured methane emissions and vegetation characteristics in 12 sites located in three states in the GIP (Ohio, Indiana, and Michigan) along a chronosequence of CRP restoration ages (3-26 years) in order to assess their climate mitigation potential. Additionally, we analyzed how the functional traits of dominant plant species in each sample plot influenced methane emissions. Methane flux rates were measured using the static chamber method monthly during the growing season (June, July, August) at six plots per site between 10 a.m. and 2 p.m. over a 20 minute sampling period. Sample plots were established over a water depth gradient, from wetland edge to center. We analyzed methane fluxes (mg CH₄-C m⁻² hr⁻¹) with respect to multiple plant traits, including whether species are native/non-native, their Regional Wetland Indicator Status, annual/perennial, monocot/dicot, growth habit, growth form, active growth period, and growth rate. These traits were gathered from existing databases. We also directly measured the % C and % N content of the dominant plant species’ tissues to understand their relationship to methane flux rates. We found a significant positive relationship between mean methane flux rates over the growing season and the years in a CRP contract. We also found an effect of chamber location and inundation on methane flux, with water depth having a positive relationship with flux rate. Several traits showed significant influence on mean methane flux rates, including the Regional Wetland Indicator Status, whether a species is an annual/perennial, a monocot/dicot, growth habit, growth form, and active growth period. We also found a significant negative relationship between flux and % C and C:N and a positive relationship between flux and % N. Using a stepwise model, we found 51% of the variation in mean methane flux could be explained by three variables: years in CRP, mean % C of the plot’s dominant plant tissue, and the growth form of the plot’s dominant plant. This study highlights the importance of conducting research in natural, restored wetlands across a chronosequence to understand how they change with time and how methane flux rates are mediated by plant traits in natural conditions.

Rights Statement

All rights reserved. This copy is provided to the Kenyon Community solely for individual academic use. For any other use, please contact the copyright holder for permission.

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