B33C-0675
Eddy covariance measurements of greenhouse gases from a restored and rewetted raised bog ecosystem.

Wednesday, 16 December 2015
Poster Hall (Moscone South)
Sung Ching Lee1, Andreas Christen2, Thomas A Black3, Mark S. Johnson4, Rick Ketler2, Zoran Nesic3 and Markus Merkens5, (1)University of British Columbia, Vancouver, BC, Canada, (2)University of British Columbia, Geography, Vancouver, BC, Canada, (3)University of British Columbia, Biometeorology Group, Faculty Land and Food Systems, Vancouver, BC, Canada, (4)University of British Columbia, Institute for Resources, Environment and Sustainability, Vancouver, BC, Canada, (5)Policy, Planning and Environment, Metro Vancouver, Vancouver, BC, Canada
Abstract:
Wetland ecosystems play a significant role in the global carbon (C) cycle. Wetlands act as a major long-term storage of carbon by sequestrating carbon-dioxide (CO2) from the atmosphere. Meanwhile, they can emit significant amounts of methane (CH4) due to anaerobic microbial decomposition.

The Burns Bog Ecological Conservancy Area (BBECA) is recognized as one of Canada’s largest undeveloped natural areas retained within an urban area. Historically, it has been substantially reduced in size and degraded by peat mining and agriculture. Since 2005, the bog has been declared a conservancy area, and the restoration efforts in BBECA focus on rewetting the disturbed ecosystems to promote a transition back to a raised bog. A pilot study measured CH4, CO2 and N2O exchanges in 2014 and concluded to monitor CO2, CH4 fluxes continuously. From the perspective of greenhouse gas (GHG) emissions, CO2 sequestered in bog needs to be protected and additional CO2 and CH4 emissions due to land-cover change need to be reduced by wise management.

In this study, we measured the growing-season (June-September) fluxes of CO2 and CH4 exchange using eddy covariance (EC). A floating platform with an EC system for both CO2 (closed-path) and CH4 (open-path) began operation in June 2015. During the growing-season, gross ecosystem photosynthesis (GEP) and ecosystem respiration (Re) averaged 5.87 g C m-2 day-1 and 2.02 g C m-2 day-1, respectively. The magnitude of GEP and Re were lower than in previous studies of pristine northern peatlands. The daily average CH4 emission was 0.99 (±1.14) g C m-2 day-1 and it was higher than in most previous studies. We also characterized how environmental factors affected the seasonal dynamics of these exchanges in this disturbed peatland. Our measurements showed that soil temperature and soil water content were major drivers of seasonal changes of GHG fluxes.

The daily average GHG warming potential (GWP) of the emissions in the growing seasons (from CO2 and CH4) totals to 37.09 g CO2e m-2 day-1. CH4 was the significant constributor (99 % of GHG emissions) indicating that GHG exchange due to photosynthesis and respiration was of secondary order. Although oxygen limitation due to the high water table caused by the restoration strategy suppressed the Re it also promoted substantial CH4 formation under anoxic conditions.

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