71 Annual Greenhouse Gas Budget for a Recently Rewetted Raised Bog Ecosystem

Monday, 20 June 2016
Alta-Sundace (Sheraton Salt Lake City Hotel)
Sung-Ching Lee, University of British Columbia, Vancouver, BC, Canada; and A. Christen, A. Black, R. Jassal, M. Johnson, R. Ketler, Z. Nesic, and M. Merkens

Handout (1.5 MB)

Rewetting of peatlands drained and disturbed by peat mining facilitates their ecological recovery, and may help them revert to carbon dioxide (CO2) sinks. However, rewetting of disturbed peatlands may also cause substantial emissions of methane (CH4). We measured year-round fluxes of CO2 and CH4 from a disturbed and recently rewetted raised bog ecosystem located in the Burns Bog Ecological Conservancy Area (BBECA), a 20 km2 bog located in the Fraser River Delta, near Vancouver, BC, Canada. The ecosystem studied was disturbed by peat mining ~40 years ago. Since 2005, the bog has been declared a conservancy area, and a major restoration effort by rewetting using a large-scale ditch blocking program to maintain natural Sphagnum regeneration has been underway for five years.

We measured the year-round turbulent fluxes of CO2 and CH4 using the eddy-covariance (EC) approach from 10th June 2015 to 30th June 2016. The flux tower was built on a floating platform and equipped with EC systems comprising Campbell Scientific Inc. CSAT3 3-D sonic anemometers and CO2 and CH4 open-path analyzers (LI-COR Inc. LI-7500 and LI-7700, respectively), and several sensors for measuring micrometeorological variables. The daily average net ecosystem exchange (NEE) of CO2 was -0.98 (±2.74) and -0.14 (±1.54) g C m-2 day-1 in summer and winter months, respectively. The daily average CH4 emission was 0.15 (±0.36) and 0.09 (±0.96) g C m-2 day-1 in summer and winter months, respectively. The daily average net GHG flux from CO2 and CH4 totaled to 1.63 g CO2e m-2 day-1 (-2.33 for CO2, 3.96 for CH4) in the second half of 2015 by using global warming potential (GWP). Oxygen limitation due to the high water table caused by the restoration strategy suppressed ecosystem respiration (Re) and promoted substantial CH4 formation under anoxic conditions in the summer months. With low temperatures in winter months, CH4 emission was more suppressed than Re. The key environmental factors controlling the seasonal dynamics of these exchanges in the BBECA were soil temperature and water table depth.

Supplementary URL: http://ibis.geog.ubc.ca/~achristn/research/Burns-Bog/

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