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Research article - Peer-reviewed, 2019

The full carbon balance of a rewetted cropland fen and a conservation-managed fen

Peacock, M.; Kaduk, J.; Morrison, R.; Page, S.; Pan, G.; Ridley, L. M.; Williamson, J.; Worrall, F.; Evans, C. D.; Gauci, V.; Baird, A. J.; Burden, A.; Chapman, P. J.; Cumming, A.; Evans, J. G.; Grayson, R. P.; Holden, J.

Abstract

On a global scale, the release of greenhouse gases (GHG) from peatland drainage and cultivation are believed to account for similar to 5% of estimated anthropogenic GHG emissions. Drainage generally leads to peat subsidence and extensive soil loss, resulting in a diminishing store of soil carbon (C). This is a challenge for maintaining drainage -based agriculture, as such practices will eventually lead to the loss of organic soils that arable cultivation depends on. The conversion of croplands on peat to semi-natural grasslands, alongside raising water tables, is one possible way to reduce the loss of these valuable C stores. Here, we report the net ecosystem carbon balances (NECB) of two lowland peatlands in East Anglia, south-east UK. One site is a relic conservation-managed fen on deep peat, subject to active hydrological management to maintain water levels, and dominated by Cladium and Phragmites sedge and reed beds, whilst the other is a former cropland that has been converted to seasonally inundated grazed grassland. Despite occasionally experiencing severe water table drawdown, the conservation managed fen was a strong C sink of-104 g C m(-2) yr(-1). In contrast, the grassland was a C source of 133 g C m(-2) yr(-1), with gaseous carbon dioxide (CO2) emissions being the main loss pathway, due to low water tables exposing the soil profile in summer. At each site, ditch emissions of CO2 were moderately large (22 and 37 g C m(-2) yr(-1)), whilst ditch methane (CH4) emissions (0.2 and 1.8 g C m(-2) yr(-1)) made a negligible contribution to the NECB, but are important when considering the ecosystem GHG balance in terms of CO2 equivalents. Excluding dissolved inorganic carbon (DIC), fluvial C losses were 6 g C M-2 yr(-1) for the conservation-managed fen and 12 g C m(-2) yr(-1) for the former cropland, and were dominated by dissolved organic carbon (DOC). The small fluvial C loss is the result of both sites being hydrologically isolated from the surrounding agricultural landscapes. Although the partially re-wetted cropland was still acting as a net C source, our estimates suggest that seasonal rewetting has reduced net annual C losses to similar to 20% of their former cropland values. Maintaining high water tables year round would potentially further reduce C losses, and shallow inundation might allow the return of wetland species such as Phragmites and Typha, perhaps as floating rafts.

Keywords

Peatland; Net ecosystem carbon balance; Greenhouse gas; Dissolved organic carbon; Restoration; Drainage

Published in

Agriculture, Ecosystems and Environment
2019, volume: 269, pages: 1-12

Authors' information

The Open University
Swedish University of Agricultural Sciences, Department of Aquatic Sciences and Assessment
Gauci, V.
Open University - UK
Baird, A. J.
University of Leeds
Burden, A.
NERC Centre for Ecology and Hydrology
Chapman, P. J.
University of Leeds
Cumming, A.
University of Leicester
Evans, J. G.
NERC Centre for Ecology and Hydrology
Grayson, R. P.
University of Leeds
Holden, J.
University of Leeds
Kaduk, J.
University of Leicester
Morrison, R.
NERC Centre for Ecology and Hydrology
Page, S.
University of Leicester
Pan, G.
University of Leicester
Ridley, L. M.
Bangor University
Williamson, J.
NERC Centre for Ecology and Hydrology
Worrall, F.
Durham University
Evans, C. D.
NERC Centre for Ecology and Hydrology

Sustainable Development Goals

SDG6 Clean water

UKÄ Subject classification

Environmental Sciences
Climate Research

Publication Identifiers

DOI: https://doi.org/10.1016/j.agee.2018.09.020

URI (permanent link to this page)

https://res.slu.se/id/publ/96809