Carbon stocks and fluxes from a boreal conifer swamp: filling a
knowledge gap for modelling the boreal C cycle
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
(CO2) and methane (CH4) fluxes from a representative wooded 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 wooded 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 CO2 and CH4 fluxes indicated that the ground layer of the
site is a source of greenhouse gases (GHG) 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.