Water table depth and plant species determine the direction and magnitude of methane fluxes in floodplain meadow soils.

Peacock, Mike ORCID: 0000-0002-3086-2854, Lawson, Clare, Gowing, David and Gauci, Vincent (2024) Water table depth and plant species determine the direction and magnitude of methane fluxes in floodplain meadow soils. Ecology and evolution, 14 (3). e11147-e11147.

Access the full-text of this item by clicking on the Open Access link.

Abstract

Methane (CH₄) is a powerful greenhouse gas with ongoing efforts aiming to quantify and map emissions from natural and managed ecosystems. Wetlands play a significant role in the global CH₄ budget, but uncertainties in their total emissions remain large, due to a combined lack of CH₄ data and fuzzy boundaries between mapped ecosystem categories. European floodplain meadows are anthropogenic ecosystems that originated due to traditional management for hay cropping. These ecosystems are seasonally inundated by river water, and straddle the boundary between grassland and wetland ecosystems; however, an understanding of their CH₄ function is lacking. Here, we established a replicated outdoor floodplain-meadow mesocosm experiment to test how water table depth (45, 30, 15 cm below the soil surface) and plant composition affect CH₄ fluxes over an annual cycle. Water table was a major controller on CH₄, with significantly higher fluxes (overall mean 9.3 mg m^-2 d^-1) from the high (15 cm) water table treatment. Fluxes from high water table mesocosms with bare soil were low (mean 0.4 mg m^-2 d^-1), demonstrating that vegetation drove high emissions. Larger emissions came from high water table mesocosms with aerenchymatous plant species (e.g. <i>Alopecurus pratensis</i>, mean 12.8 mg m^-2 d^-1), suggesting a role for plant-mediated transport. However, at low (45 cm) water tables <i>A. pratensis</i> mesocosms were net CH₄ sinks, suggesting that there is plasticity in CH₄ exchange if aerenchyma are present. Plant cutting to simulate a hay harvest had no effect on CH₄, further supporting a role for plant-mediated transport. Upscaling our CH₄ fluxes to a UK floodplain meadow using hydrological modelling showed that the meadow was a net CH₄ source because oxic periods of uptake were outweighed by flooding-induced anoxic emissions. Our results show that floodplain meadows can be either small sources or sinks of CH₄ over an annual cycle. Their CH₄ exchange appears to respond to soil temperature, moisture status and community composition, all of which are likely to be modified by climate change, leading to uncertainty around the future net contribution of floodplain meadows to the CH₄ cycle.

Item Type:	Article
Uncontrolled Keywords:	aerenchyma, ecosystem, greenhouse gas, hydrology, meadow, methane, plants, vegetation, water table, wetland
Divisions:	Faculty of Science and Engineering > School of Environmental Sciences
Depositing User:	Symplectic Admin
Date Deposited:	18 Mar 2024 10:09
Last Modified:	18 Mar 2024 10:09
DOI:	10.1002/ece3.11147
Open Access URL:	https://onlinelibrary.wiley.com/doi/10.1002/ece3.1...
Related URLs:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3179611