Net Ecosystem Carbon Balance of a Peat Bog Undergoing Restoration: Integrating CO2 and CH4 Fluxes From Eddy Covariance and Aquatic Evasion With DOC Drainage Fluxes. Issue 4 (11th April 2019) - D′Acunha, Brenda
Abstract: Peatland ecosystems are generally carbon (C) sinks. However, the role of dissolved organic C (DOC) relative to gaseous fluxes of CO2 and CH4 in the C balance of these ecosystems has not often been studied. Dissolved C fluxes are important for understanding C partitioning within the peatland and the potential C drainage from it. This research was conducted in Burns Bog, a heavily impacted ecosystem near Vancouver, Canada, undergoing ecological restoration efforts by rewetting. Here we present data on (i) ecosystem‐scale fluxes of CO2 (net ecosystem exchange, NEE) and CH4 (FCH4 ) determined by eddy covariance, (ii) evasion fluxes of CO2 and CH4 from the water surface to estimate the role of open water in ecosystem‐scale fluxes, and (iii) DOC flux (fDOC) in water draining from the peatland. Our results showed that open water areas inside the footprint were a continual C source, emitting 47.0 ± 2.4 g C·m −2 ·year −1 . DOC export (15.6 g C·m −2 ·year −1 ) was significant to the net ecosystem C balance, decreasing the magnitude of the eddy covariance‐determined C balance (i.e., NEE + FCH4 ) of −45.0 ± 16.8 g C·m −2 ·year −1 by 35%, resulting in a net ecosystem C balance (i.e., NEE + FCH4 + fDOC) of −29.7 ± 17.0 g C·m −2 ·year −1 . Most of this offset occurred during the wetter nongrowing season when gross primary production was low and fDOC was relatively high. Plain Language Summary: Healthy peatlands can store large amounts of carbon, but disturbance may turn a peatland into a carbon emitter. We studied the amount of carbon entering and leaving a disturbed peatland that has recently undergone ecological restoration by rewetting. We measured climate conditions and ecosystem‐scale CO2 and CH4 fluxes in Burns Bog, a heavily impacted raised bog in the Fraser River Delta, BC, Canada. We also collected water samples and estimated evasion fluxes of CO2 and CH4 from the open water, as well as drainage fluxes of dissolved organic carbon. From these data, we estimated the amount of carbon entering and leaving the ecosystem. We found that open water areas continually emit carbon to the atmosphere, but the ecosystem as a whole is accumulating carbon on an annual basis. Accounting for the dissolved carbon exported by water reduces the estimates of carbon accumulation based on gas fluxes alone. These results have implications for restoration management of peatlands, which mainly consist of raising the water table level, and the role of peatland ecosystems within the context of global climate change. Key Points: NECB of −29.7 g C m −2 year −1 as NEE + FCH4 + fDOC showed the bog ecosystem to be a weak C sink during the study period Open water areas had comparable areal fluxes of CO2 and CH4 during both growing and nongrowing seasons DOC export increased total C export by 21% over net gaseous fluxes (CO2 ‐C plus CH4 ‐C) during the wetter nongrowing season