Restored peatlands

Carbon Exchange in Restored Peatlands

The demand for peat to be used in commercial bedding operations and in home gardening has increased in the past decades and a thriving industry - organized under the Canadian Sphagnum Peat Moss Association - has developed. As part of their operations, following peat extraction, producers are expected to take steps to restore the peatland to a its pre-extraction functioning. One way in which this is assessed is through a return of the system to a carbon sink. In partnership with Dr. Line Rochefort (Laval), Dr. Maria Strack (Waterloo) and Dr. Nigel Roulet (McGill), the AERlab has been assessing the carbon dynamics in two pairs of post-extraction restored peatlands. In each pair, one peatland has been restored using the moss-layer transfer technique while the other has not had any active vegetation restoration. We installed eddy covariance (EC) towers in each of the four peatlands and measured nearly continuously for the next 3-4 years. Our western pair is located near Seba Beach, Alberta. Measurements represent years 1-3 of restoration. Our eastern pair is located near Riviere du Loup, QC and measurements represent years 15-17 post-restoration.

Results:

Several graduate students have recently completed their theses:

Tracy Rankin completed MSc research on the unrestored 15yr old peatland site. Her results indicate that the resulting site is dry with a water table well below the surface. Only sparse Eriophorum spp, have been successful in colonizing the fields. The ecosystem therefore remains a source of CO2 to the atmosphere but despite the presence of the Eriophorum, ecosystem methane flux is small. The exceptions are the ditches which have been invaded by Typha and Phragmites spp.; both take up CO2 through rapid growth but are conduits for methane. However, the ditches are a small fraction of the total area and therefore the net result is that the site remains a source of C after 15 years.
Dr. Kelly Nugent's research indicated that a previously harvested peatland that has been actively restored was a net carbon sink 15 years after restoration with net C uptake well within the range of values found at undisturbed bogs (e.g. Mer Bleue). She used an atmospheric perturbation model to compute changes in radiative forcing (RF) over 500 years and demonstrated that active restoration reduced the RF by 89% within 20 years compared to a wide range of rewetting activities. From a management perspective, she showed that immediate restoration resulted in a neutral climate impact 155 years earlier than a 20-year delay in restoration.
Scott MacDonald completed MSc research at the western peatland. His results show that the restored site remains a source of carbon for the first three years but that the source of CO2 is decreasing as vegetation increases. In 2015, Scott installed a second EC tower at a wetter area of the restored site and found that the small topographic gradient had a large effect on site hydrology resulting in favourable conditions for vegetation and carbon uptake.
Sabrina Touchette completed MSc research (supervised by Maria Strack) focusing on the C exchange from species in the wetter areas of the restored site and the controls on their growth and functioning.

Publications and theses:

Nugent, K.A., Strachan, I.B.*, Strack, M., Roulet, N.T., Strom, L. and Chanton, J., 2021. Cutover peat limits methane production causing low emission at a post-extraction restored peatland. Journal of Geophysical Research – Biogeosciences 126(12), doi.org/10.1029/2020JG005909

Nugent, K.A., Strachan, I.B., Strack, M., Roulet, N.T., Frolking, S. and Helbig, M., 2019. Prompt active restoration of peatlands substantially reduces radiative forcing. Environmental Research Letters 14: 124030 doi:10.1088/1748-9326/ab56e6

Nugent, K.A., Strachan, I.B., Strack, M., Roulet, N.T., Rochefort, L., 2018. Multi-year net ecosystem carbon balance of a restored peatland reveals a return to C sink. Global Change Biol. 24(12): 5751-5768. doi:10.1111/gcb.14449

Rankin, T., Strachan, I.B. and Strack, M., 2018. Carbon dioxide and methane exchange at a post-extraction, unrestored peatland. Ecological Engineering 122: 241-251. doi:10.1016/j.ecoleng.2018.06.021

Strack, M., Cagampan, J., Hassanpour Fard, G., Keith, A.M., Nugent, K.A., Rankin, T., Robinson, C., Strachan, I.B., Waddington, J.M., and Xu, B., 2016. Controls on plot-scale growing season CO2 and CH4 fluxes in restored peatlands: Do they differ from unrestored and natural sites? Mires and Peat 17(5): 1-18. DOI: 10.19189/MaP.2015.OMB.216

Kelly Nugent 2019 “Carbon cycling at a post-extraction restored peatland: Small-scale processes to global climate impacts” PhD Thesis, McGill University

Scott MacDonald 2017 “Interannual variability and spatial heterogeneity in net carbon exchange at a restored peatland in Alberta” MSc Thesis, McGill University

Sabrina Touchette 2017 (as co-supervisor w. M. Strack) “Hydrological controls on GHG exchange in a post-restoration peatland” MSc Thesis, University of Waterloo

Tracy Rankin 2016 “An analysis of carbon dioxide and methane exchange at a post-extraction, unrestored peatland in Eastern Québec” MSc Thesis, McGill University