Annual carbon balance of a peatland 10 yr following restoration

Abstract

Undisturbed peatlands represent long term net sinks of carbon; however, peat extraction converts these systems into large and persistent sources of greenhouse gases. Although rewetting and restoration following peat extraction have taken place over the last several decades, very few studies have investigated the longer term impact of this restoration on peatland carbon balance. We determined the annual carbon balance of a former horticulturally-extracted peatland restored 10 yr prior to the study and compared these values to the carbon balance measured at neighboring unrestored and natural sites. Carbon dioxide (CO<sub>2</sub>) and methane (CH<sub>4</sub>) fluxes were measured using the chamber technique biweekly during the growing season from May to October 2010 and three times over the winter period. Dissolved organic carbon (DOC) export was measured from remnant ditches in the unrestored and restored sites. During the growing season the restored site had greater uptake of CO<sub>2</sub> than the natural site when photon flux density was greater than 1000 µmol m<sup>−2</sup> s<sup>−1</sup>, while the unrestored site remained a source of CO<sub>2</sub>. Ecosystem respiration was similar between natural and restored sites, which were both significantly lower than the unrestored site. Methane flux remained low at the restored site except from open water pools, created as part of restoration, and remnant ditches. Export of DOC during the growing season was 5.0 and 28.8 g m<sup>−2</sup> from the restored and unrestored sites, respectively. Due to dry conditions during the study year all sites acted as net carbon sources with annual balance of the natural, restored and unrestored sites of 250.7, 148.0 and 546.6 g C m<sup>−2</sup>, respectively. Although hydrological conditions and vegetation community at the restored site remained intermediate between natural and unrestored conditions, the site acted as a smaller source of carbon than the natural peatland suggesting that near natural carbon balance can be returned ~ 10 yr post-restoration

Carbon balance of rewetted and drained peat soils used for biomass production: a mesocosm study

“…The concentration of DOC may increase under anoxic conditions due to less efficient anaerobic (than aerobic) decomposition leading to higher concentrations of water‐soluble intermediate metabolites (Mulholland et al ., ; Kalbitz et al ., ), due to decrease in DOC adsorption (Kaiser & Zech, ) and due to slower conversion of released DOC to CO 2 (Moore & Dalva, ). However, an increase in DOC concentration may not necessary increase the total DOC fluxes from the rewetted system as the hydrological changes made during the rewetting would lower the discharge and thereby total DOC export (Strack & Zuback, ). Further studies are needed to specifically address the role of waterborne C fluxes for the total carbon balance at different GWL managements.…”

Methane Feedbacks to the Global Climate System in a Warmer World

“…Rewetting may lead to excessive CH 4 emission initially, when vegetation is flooded and dies off becoming available for methanogenesis (Augustin & Chojnicki, ). The evolution of CH 4 emission patterns following rewetting can vary depending on the previous land use (Abdalla et al, ), but rewetting is generally considered to reduce net GHG emissions in the long run (Joosten, ; Strack & Zuback, ). This may not remain the case if rising global temperatures drive CH 4 emissions higher.…”

An overview of peatland restoration in North America: where are we after 25 years?

“…Additional information is needed to quantify how different restoration techniques modify GHGs (Wilson et al ). This is important for restoration that involves rewetting because filled and blocked ditches can be hotspots for methane (CH 4 ) emissions (Waddington & Day ; Strack & Zuback ), but it is unknown if this is a short‐term pulse or a longer‐term process. Rewetting can also release N 2 O in former agricultural fields (Schrier‐Uijl et al ).…”