Macquarie University
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Methane emissions and soil carbon in floodplain wetlands of the Macquarie Marshes

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posted on 2022-03-29, 00:56 authored by Saadu Umar Wali
Methane (CH₄) emission in wetlands is critical because CH₄ has 25 times the global warming potential of carbon dioxide (CO₂), and wetlands play a critical role in global carbon cycling. Using flux chambers this research investigated CH4 emissions in three wetland zones in the Macquarie Marshes: reed bed, dry floodplain and dryland. Methane emissions were highly heterogenous and CH₄ production only occurred in the reed bed (1.73E+01 kg ha⁻¹ d⁻¹). In contrast, CH₄ was oxidised in the dry floodplain (-1.03E-03 kg ha⁻¹ d⁻¹) and there was no production or oxidation of CH₄ in the dryland. Methane flux was strongly correlated with in situ moisture content. The median isotopic signature of CH₄ (δ¹³C;-56.3±2.36 ‰) agrees with wetlands globally and can be used in regional mixing models. The reed bed (809.h ha) has the potential to release 4.97E-03 Tg yr⁻¹, and an equivalent area of dry floodplain could oxidise -2.97E-07 Tg yr⁻¹, yielding a net CH₄ flux of 4.97E-03 Tg yr¹. The results demonstrate for the first time that freshwater floodplain wetlands in dry landscapres can both sequester and emit CH₄, and that where freshwater floodplainwetlands emit CH₄ the rate is comparable to coastal mangroves.


Table of Contents

1. Introduction -- 2. Review of methane emissions ans soil carbon in wetlands in dry landscapes -- 3. Methane emissions and soil carbon in the Macquarie Marshes -- 4. Conclusion.


Theoretical thesis. Bibliography: pages 52-59

Awarding Institution

Macquarie University

Degree Type

Thesis MRes


MRes, Macquarie University, Faculty of Science and Engineering, Department of Environmental Sciences

Department, Centre or School

Department of Environmental Sciences

Year of Award


Principal Supervisor

Tim Ralph


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