ORCID

Abstract

The carbon (C) dynamics of boreal coniferous swamps are a largely understudied component of wetland carbon cycling. We investigated the above- and below-ground carbon stocks and growing season carbon dioxide (CO 2) and methane (CH 4) fluxes from a representative boreal coniferous swamp in northern Alberta, Canada in 2022. Tree inventories, understory vegetation biomass and peat cores were collected across three sub-sites within the broader swamp, with gas flux collars placed in the dominant plant communities present. Alongside the C flux measurements, environmental variables such as water table depth, soil temperature and growing season understory green leaf phenology were measured. Our results show that these boreal coniferous swamps store large volumes of organic C in their biomass and soil (134 kg C m −2), comparable with other wetland and forest types, although 95% of the total C stock at our site was within the soil organic carbon. We also found that understory CO 2 and CH 4 fluxes indicated that the ground layer of the site is a source of greenhouse gases (GHGs) to the atmosphere across the growing season. However, we did not measure litterfall input, tree GHG fluxes or net primary productivity of the overstory, therefore we are not able to say whether the site is an overall source of C to the atmosphere. This study provides a much-needed insight into the C dynamics of these under-valued wetland ecosystems, and we highlight the need for a coordinated effort across boreal regions to try to improve inventories of C stocks and fluxes.

Publication Date

2024-05-15

Publication Title

Journal of Geophysical Research: Biogeosciences

Volume

129

Issue

5

ISSN

2169-8953

Acceptance Date

2024-04-23

Deposit Date

2024-09-03

Funding

The authors would like to acknowledge that this research takes place within the boundaries of Treaty 8, traditional lands of the Dene and Cree, as well as the traditional lands of the M\u00E9tis of northern Alberta. The University of Waterloo is located on the traditional territory of the Neutral, Anishnaabeg, and Haudenosaunee Peoples. The University of Waterloo is situated on the Haldimand Tract, land promised to Six Nations, which includes six miles on each side of the Grand River. Funding for this project was provided by a Natural Sciences and Engineering Research Council of Canada (NSERC) Collaborative Research and Development (CRD) grant to MS (CRDPJ-523334-18), co-funded by Suncor Energy Inc., Imperial Oil Resources Limited, Teck and Shell Canada Energy, and an NSERC Discovery Grant (RGPIN-2020-04098) and Canada Research Chair (CRC-2019-00299) awarded to MS. MP acknowledges funding from Formas under projects LEAF-PAD (2020-00950) and PUDDLE-JUMP (2022-02138). We thank Dr Matthew Elmes for providing details on the hydrologic characteristics of the site. We thank Prof. James W. Waddington and Dr. Nicholas Girkin and an anonymous reviewer for useful feedback on an earlier version.

Keywords

boreal, carbon dioxide, conifer swamp, methane, soil organic carbon

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Davidson_et_al_boreal_swamp_C_dynamics_final.pdf (7527 kB)

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