Development of a subarctic peatland linked to slope dynamics at Lac Wiyâshâkimî (Nunavik, Canada)

A palaeoecological study of a subarctic minerotrophic peatland was undertaken to reconstruct the formation of the site as an archive of slope geomorphological processes. The study peatland is located about 400 m from Caribou slope (unofficial name) on Lepage Island, Lac Wiyâshâkimî, Nunavik (northern Québec, Canada). The site is close to the lakeshore and receives runoff directly from Caribou slope and its catchment. Gravity processes have been active on Caribou slope since the deglaciation of the region at approximately 6000 cal. yr BP. These processes may be differentiated in terms of Holocene stages of intensity. The objective of our study was to detect evidence of gravity processes in the peatland and to note their frequency since its establishment using loss-on-ignition testing, macrofossil analysis and radiocarbon dating. Our results indicate that peat began to accumulate over the sandy-gravelly sediments at around 4900 cal. yr BP. Larix Laricina, Carex aquatilis and Carex rostrata were present at this time until 4660 cal. yr BP, at which point these taxa were replaced by aquatic taxa such as Hippuris vulgaris and Daphnia (aquatic invertebrates). The percentage of mineral sediments (sand) remained high during this period, which could be linked to slope activity. After 4660 cal. yr BP, sandy sediments diminished while episodes of aquatic conditions and sand inflow occurred on at least three occasions (at 4660, 3905 and 3130 cal. yr BP). The increase in water flow and the introduction of more medium to fine sand into the peatland could be linked to slope movements and the long-distance runout of debris flow that we observed in the field. Given these factors, conditions at the study site remained wet from the earliest phases until the present. Unlike the subarctic permafrost peatlands in northern Québec, permafrost did not become established at the study site.

The role of <i>Phragmites</i> in the CH₄ and CO₂ fluxes in a minerotrophic peatland in southwest Germany

Peatlands are interesting as a carbon storage option, but are also natural emitters of the greenhouse gas methane (CH4). Phragmites peatlands are particularly interesting due to the global abundance of this wetland plant (Phragmites australis) and the highly efficient internal gas transport mechanism, which is called humidity-induced convection (HIC). The research aims were to (1) clarify how this plant-mediated gas transport influences the CH4 fluxes, (2) which other environmental variables influence the CO2 and CH4 fluxes, and (3) whether Phragmites peatlands are a net source or sink of greenhouse gases. CO2 and CH4 fluxes were measured with the eddy covariance technique within a Phragmites-dominated fen in southwest Germany. One year of flux data (March 2013–February 2014) shows very clear diurnal and seasonal patterns for both CO2 and CH4. The diurnal pattern of CH4 fluxes was only visible when living, green reed was present. In August the diurnal cycle of CH4 was the most distinct, with 11 times higher midday fluxes (15.7 mg CH4 m−2 h−1) than night fluxes (1.41 mg CH4 m−2 h−1). This diurnal cycle has the highest correlation with global radiation, which suggests a high influence of the plants on the CH4 flux. But if the cause were the HIC, it would be expected that relative humidity would correlate stronger with CH4 flux. Therefore, we conclude that in addition to HIC, at least one additional mechanism must be involved in the creation of the convective flow within the Phragmites plants. Overall, the fen was a sink for carbon and greenhouse gases in the measured year, with a total carbon uptake of 221 g C m−2 yr−1 (26 % of the total assimilated carbon). The net uptake of greenhouse gases was 52 g CO2 eq. m−2 yr−1, which is obtained from an uptake of CO2 of 894 g CO2 eq. m−2 yr−1 and a release of CH4 of 842 g CO2 eq. m−2 yr−1.

Net nitrogen mineralization in boreal fens: a potential performance indicator for peatland reclamation

The Sandhill Fen reclamation watershed, commissioned by Syncrude Canada Ltd., is the first attempt to reclaim a self-sustaining peat-forming wetland on a previously mined area. Here, we quantified net nitrogen mineralization rates at Sandhill Fen in the first and second years since initiation (2013–2014). Our main objective was to determine whether nitrogen production potentials at Sandhill Fen were similar to six regional fens sampled across an ombrotrophic–minerotrophic peatland gradient. In the second year, net nitrogen mineralization rates across Sandhill Fen (2014 mean = 20.2 mg N·m−2·day−1; 0.9 mg N·kg−1·day−1) were quite comparable with the benchmark fen sites (2013–2014 pooled means = 20.6 mg N·m−2·day−1; 5.9 mg N·kg−1·day−1). However, in areas exhibiting low gravimetric soil moisture content at Sandhill Fen, net nitrification contributed more than 50% to the net N mineralization total, an uncommon observation in natural fen type wetlands. These findings highlight the importance of managing soil moisture levels during the early stages of reclamation to (1) maintain relatively anaerobic soil conditions, and (2) facilitate microbial-mediated processes to fall within an acceptable range of variation comparable to undisturbed Albertan fens.

Reintroduction of fen plant communities on a degraded minerotrophic peatland

We have developed an approach to restore bogs after peat extraction, but, when sedge-peat layers are exposed, the minerotrophic remnant peat conditions require restoration towards a fen ecosystem. Three restoration techniques, all including rewetting actions, were tested to assist fen vegetation recovery. None of the restoration techniques were effective at establishing fen bryophytes. However, for vascular plants, two techniques gave promising results in terms of species composition, although the vascular plant cover remained lower than in the reference fens. Depending on the site conditions, we suggest applying two restoration techniques to restore peatlands in areas of exposed sedge peat. In areas where sparse cover of fen species may have spontaneously established, rewetting should be carried out to raise water levels and create favourable conditions for their expansion. In areas covered with undesirable species or with inadequate topography for rewetting, surface peat should be remodeled and vegetation introduced. Since mechanized diaspore transfer did not result in a satisfactory cover of fen plants, other means of introduction could be considered, alone or in combination. A complementary fertilization experiment showed that fertilization with phosphorus could be an effective solution to enhance the establishment of mechanically introduced plant diaspores.

The role of <i>Phragmites</i> on the CH₄ and CO₂ fluxes in a minerotrophic peatland in Southwest Germany

Peatlands are interesting as carbon storage option, but are also natural emitters of the greenhouse gas methane (CH4). Phragmites peatlands are particularly interesting due to the global abundancy of this wetland plant (Phragmites australis (Cav.) Trin. ex Steud.) and the highly efficient internal gas transport mechanism, which is called Humidity Induced Convection (HIC). The research aim was to (1) clarify how this plant-mediated gas transport influences the CH4 fluxes, (2) which other environmental variables influence the CO2 and CH4 fluxes, and (3) whether Phragmites peatlands are a net source or sink of greenhouse gases. CO2 and CH4 fluxes were measured with the eddy covariance technique within a Phragmites-dominated fen in Southwest Germany. One year of flux data (March 2013 to February 2014) shows very clear diurnal and seasonal patterns for both CO2 and CH4. The diurnal pattern of CH4 fluxes was only visible when living green reed was present. In August the diurnal cycle of CH4 was most distinct, with 11-times higher midday fluxes (15.7 mg CH4 m−2 h−1) than night fluxes (1.41 mg CH4 m−2 h−1). This diurnal cycle correlates the highest with global radiation, which suggest a high influence of the plants on the CH4 flux. But if the cause would be the HIC, it is expected that relative humidity would correlate stronger with CH4 flux. Therefore, we conclude that in addition to HIC, at least one additional mechanism must be involved in the creation of the convective flow within the Phragmites plants. Overall, the fen was a sink for carbon and greenhouse gases in the measured year, with a total carbon uptake of 221 g C m−2 yr−1 (26 % of the total assimilated carbon). The net uptake of greenhouse gases was 52 g CO2-eq m−2 yr−1, which is summed from an uptake of CO2 of 894 g CO2-eq m−2 yr−1 and a release of CH4 of 842 g CO2-eq m−2 yr−1.