부산대학교 도서관

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.sub.2) sinks. However, rewetting may also cause substantial emissions of the more potent greenhouse gas (GHG) methane (CH.sub.4). Our knowledge of the exchange of CO.sub.2 and CH.sub.4 following rewetting during restoration of disturbed peatlands is currently limited. This study quantifies annual fluxes of CO.sub.2 and CH.sub.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.sub.2 and CH.sub.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.sub.2 budget of the rewetted area was -179 ± 26.2 g CO.sub.2 -C m.sup.-2 yr.sup.-1 (CO.sub.2 sink) and the annual CH.sub.4 budget was 17 ± 1.0 g CH.sub.4 -C m.sup.-2 yr.sup.-1 (CH.sub.4 source). Gross ecosystem productivity (GEP) exceeded ecosystem respiration (R.sub.e) during summer months (June-August), causing a net CO.sub.2 uptake. In summer, high CH.sub.4 emissions (121 mg CH.sub.4 -C m.sup.-2 day.sup.-1) were measured. In winter (December-February), while roughly equal magnitudes of GEP and R.sub.e made the study area CO.sub.2 neutral, very low CH.sub.4 emissions (9 mg CH.sub.4 -C m.sup.-2 day.sup.-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.sub.e . With low temperatures in winter, CH.sub.4 emissions were more suppressed than R.sub.e . Annual net GHG flux from CO.sub.2 and CH.sub.4 expressed in terms of CO.sub.2 equivalents (CO.sub.2 eq.) during the study period totalled -22 ± 103.1 g CO.sub.2 eq. m.sup.-2 yr.sup.-1 (net CO.sub.2 eq. sink) and 1248 ± 147.6 g CO.sub.2 eq. m.sup.-2 yr.sup.-1 (net CO.sub.2 eq. source) by using 100- and 20-year global warming potential values, respectively. Consequently, the ecosystem was almost CO.sub.2 eq. neutral during the study period expressed on a 100-year time horizon but was a significant CO.sub.2 eq. source on a 20-year time horizon.
Byline: Sung-Ching Lee, Andreas Christen, Andrew T. Black, Mark S. Johnson, Rachhpal S. Jassal, Rick Ketler, Zoran Nesic, Markus Merkens To access, purchase, authenticate, or subscribe to the full-text of [...]