Abstract. Many peatlands have been drained and harvested for peat mining, agriculture, and other purposes, which has turned them from carbon (C) sinks into C emitters. Rewetting of disturbed peatlands facilitates their ecological recovery and may help them revert to carbon dioxide (CO 2 ) sinks. However, rewetting may also cause substantial emissions of the more potent greenhouse gas (GHG) methane (CH 4 ). Our knowledge of the exchange of CO 2 and CH 4 following rewetting during restoration of disturbed peatlands is currently limited. This study quantifies annual fluxes of CO 2 and CH 4 in a disturbed and rewetted area located in the Burns Bog Ecological Conservancy Area in Delta, BC, Canada. Burns Bog is recognized as the largest raised bog ecosystem on North America's west coast. Burns Bog was substantially reduced in size and degraded by peat mining and agriculture. Since 2005, the bog has been declared a conservancy area, with restoration efforts focusing on rewetting disturbed ecosystems to recover Sphagnum and suppress fires. Using the eddy covariance (EC) technique, we measured year-round (16 June 2015 to 15 June 2016) turbulent fluxes of CO 2 and CH 4 from a tower platform in an area rewetted for the last 8 years. The study area, dominated by sedges and Sphagnum, experienced a varying water table position that ranged between 7.7 (inundation) and −26.5 cm from the surface during the study year. The annual CO 2 budget of the rewetted area was −179 ± 26.2 g CO 2 -C m −2 yr −1 (CO 2 sink) and the annual CH 4 budget was 17 ± 1.0 g CH 4 -C m −2 yr −1 (CH 4 source). Gross ecosystem productivity (GEP) exceeded ecosystem respiration (R e ) during summer months (June-August), causing a net CO 2 uptake. In summer, high CH 4 emissions (121 mg CH 4 -C m −2 day −1 ) were measured. In winter (December-February), while roughly equal magnitudes of GEP and R e made the study area CO 2 neutral, very low CH 4 emissions (9 mg CH 4 -C m −2 day −1 ) were observed. The key environmental factors controlling the seasonality of these exchanges were downwelling photosynthetically active radiation and 5 cm soil temperature. It appears that the high water table caused by ditch blocking suppressed R e . With low temperatures in winter, CH 4 emissions were more suppressed than R e . Annual net GHG flux from CO 2 and CH 4 expressed in terms of CO 2 equivalents (CO 2 eq.) during the study period totalled −22 ± 103.1 g CO 2 eq. m −2 yr −1 (net CO 2 eq. sink) and 1248 ± 147.6 g CO 2 eq. m −2 yr −1 (net CO 2 eq. source) by using 100-and 20-year global warming potential values, respectively. Consequently, the ecosystem was almost CO 2 eq. neutral during the study period expressed on a 100-year time horizon but was a significant CO 2 eq. source on a 20-year time horizon.

<p><strong>Abstract.</strong> Many peatlands have been drained and harvested for peat mining, which has turned them from carbon (C) sinks into C emitters. Rewetting of disturbed peatlands facilitates their ecological recovery, and may help them revert to carbon dioxide (CO<sub>2</sub>) sinks. However, rewetting may also cause substantial emissions of the more potent greenhouse gas (GHG) methane (CH<sub>4</sub>). Our knowledge on the exchange of CO<sub>2</sub> and CH<sub>4</sub> following rewetting during restoration of disturbed peatlands is currently limited. This study quantifies annual fluxes of CO<sub>2</sub> and CH<sub>4</sub> in a disturbed and rewetted area located in the Burns Bog Ecological Conservancy Area in Delta, BC, Canada. Burns Bog is recognized as the largest raised bog ecosystem on North America's West Coast. Burns Bog was substantially reduced in size and degraded by peat mining and agriculture. Since 2005, the bog has been declared a conservancy area, with restoration efforts focusing on rewetting disturbed ecosystems to recover Sphagnum and suppress fires. Using the eddy-covariance (EC) technique, we measured year-round (16<sup>th</sup> June 2015 to 15<sup>th</sup> June 2016) turbulent fluxes of CO<sub>2</sub> and CH<sub>4</sub> from a tower platform in an area rewetted for the last 8 years. The study area, dominated by sedges and Sphagnum, experienced a varying water table position that ranged between 7.7 (inundation) and −26.5 cm from the surface during the study year. The annual CO<sub>2</sub> budget of the rewetted area was −179 g CO<sub>2</sub>-C m<sup>−2</sup> year<sup>−1</sup> (CO<sub>2</sub> sink) and the annual CH<sub>4</sub> budget was 16 g CH<sub>4</sub>-C m<sup>−2</sup> year<sup>−1</sup> (CH<sub>4</sub> source). Gross ecosystem productivity (GEP) exceeded ecosystem respiration (Re) during summer months (June–August), causing a net CO<sub>2</sub> uptake. In summer, high CH<sub>4</sub> emissions (121 mg CH<sub>4</sub>-C m<sup>−2</sup> day<sup>−1</sup>) were measured. In winter (December–February), while roughly equal magnitudes of GEP and Re made the study area CO<sub>2</sub> neutral, very low CH<sub>4</sub> emissions (9 mg CH<sub>4</sub>-C m<sup>−2</sup> day<sup>−1</sup>) were observed. The key environmental factors controlling the seasonality of these exchanges were downwelling photosynthetically active radiation and 5-cm soil temperature. It appears that the high water table caused by ditch blocking which suppresses Re. With low temperatures in winter, CH<sup>4</sup> emission was more suppressed than Re. Annual net GHG flux from CO<sub>2</sub> and CH<sub>4</sub> expressed in terms of CO<sub>2</sub> equivalents (CO<sub>2</sub>e) during the study period totaled to −55 g CO<sub>2</sub>e m<sup>−2</sup> year<sup>−1</sup> (net CO<sub>2</sub>e sink) and 1147 g CO<sub>2</sub>e m<sup>−2</sup> year<sup>−1</sup> (net CO<sub>2</sub>e source) by using 100-year and 20-year global warming potential values, respectively. Consequently, the ecosystem was almost CO<sub>2</sub>e neutral during the study period expressed on a 100-year time horizon but was a significant CO<sub>2</sub>e source on a 20-year time horizon.</p>

In this study, we quantified the ecosystem-scale CO 2 exchange of two different but typical low-latitude vegetation types, para grass and reed, in a subtropical wetland ecosystem by integrating flux observation with the parameterization of environmental variables. In addition, we explored how seasonal dynamics of environmental factors affected variations in CO 2 budget. The results suggest that gross primary production (GPP, in the order of 1700 gC m −2 yr −1 ) of CO 2 was higher in this site than in previous studies of northern peatlands and estuarial wetlands because of the direct effect of environmental factors. Temperature and radiation had a larger effect than water status (soil moisture content and vapor pressure deficit) on GPP for the two low-latitude ecosystems, which differ from the results for high-latitude regions. Environmental variables had a strong but different impact on the CO 2 budget for para grass and reed areas. This diversity led to different potential shifts and trends of biomass accumulation and distribution of these two typical low-latitude vegetation types under different scenarios of environmental change. The findings from this study can sufficiently provide quantitative understanding of CO 2 budgets in low-latitude wetlands.

Monitoring peatland restoration can be labour intensive, and monitoring activities can result in further disturbance, suggesting that remote sensing can play an important role in assessing ecosystem responses to restoration efforts. In this study, we assessed the response of plant phenological parameters for Burns Bog, a highly disturbed peatland in Western Canada, to restoration efforts. We evaluated the potential for rewetting of disturbed areas to reverse impacts from prior changes in NDVI and ET were strongly correlated to precipitation, temperature and the change in water table height at each transect. We found that NDVI was more effective than ET for investigating the impacts of disturbance events (e.g., fires in the bog), whereas ET provided a better index to monitor the ecohydrological functioning of the bog in response to restoration efforts.

Abstract. A short, but severe, wildfire smoke episode in July 2015, with an aerosol optical depth (AOD) approaching 9, is shown to strongly impact radiation budgets across four distinct land-use types (forest, field, urban and wetland). At three of the sites, impacts on the energy balance are also apparent, while the event also appears to elicit an ecosystem response with respect to carbon fluxes at the wetland and a forested site. Greatest impacts on radiation and energy budgets were observed at the forested site where the role of canopy architecture and the complex physiological responses to an increase in diffuse radiation were most important. At the forest site, the arrival of smoke reduced both sensible and latent heat flux substantially but also lowered sensible heat flux more than the latent heat flux. With widespread standing water, and little physiological control on evapotranspiration, the impacts on the partitioning of turbulent fluxes were modest at the wetland compared to the physiologically dominated fluxes at the forested site. Despite the short duration and singular nature of the event, there was some evidence of a diffuse radiation fertilization effect when AOD was near or below 2. With lighter smoke, both the wetland and forested site appeared to show enhanced photosynthetic activity (a greater sink for carbon dioxide). However, with dense smoke, the forested site was a strong carbon source. Given the extensive forest cover in the Pacific Northwest and the growing importance of forest fires in the region, these results suggest that wildfire aerosol during the growing season potentially plays an important role in the regional ecosystem response to smoke and ultimately the carbon budget of the region.