UBC Theses and Dissertations
Net ecosystem carbon balance for a peat bog undergoing restoration by integrating flux tower and aquatic flux measurements D'Acunha, Brenda
Peatlands are wetlands where gross primary production exceeds organic matter decomposition causing an accumulation of partially decomposed matter, also called peat. Peat ecosystems can accumulate more carbon (C) than tropical rainforests. However, dissolved fluxes of C (as dissolved organic carbon (DOC), carbon dioxide (CO₂) and methane (CH₄)) must also be considered to determine if these ecosystems are net sinks or sources of greenhouse gases (GHGs) to the atmosphere. This research was conducted in Burns Bog, Delta, BC, Canada, one of the largest bogs on the west coast of the Americas, but which has been heavily impacted by a range of human activities. Currently, ecological restoration efforts are underway by a large-scale ditch blocking program, with the aim of re-establishing water table conditions that promote peat accumulation. Here I present data on ecosystem-scale fluxes of CO₂ and CH4 determined by eddy covariance (EC), together with data on (i) evasion fluxes of CO₂ and CH₄ from the water surface, and (ii) the flux and characteristics of DOC in water draining Burns Bog. The net ecosystem carbon balance (NECB) was determined as the sum of EC fluxes and DOC export. Concentrations of dissolved CO₂ and CH₄ were determined by headspace equilibration, and evasion rates from the water surface were quantified and used to estimate the role of the hydrosphere in the ecosystem-scale measurements. Water samples collected from five saturated areas in the flux tower footprint were analyzed for DOC concentrations and characteristics. Satellite imaging showed that during the dry season 10% of the area was covered by water, while on the wet season, it was 60%. The hydrosphere was found to be a continual C source, emitting 271 g C m-² yr-¹. NECB was found to be -98 g C m-² yr-¹. DOC export was found to offset about 60% of the apparent net C emissions determined by EC during the wet season and 3% of the net C uptake during the dry season, indicating that the EC measurements by themselves underestimate C emissions during the wet season and overestimate C accumulation in the dry season by not accounting for DOC drainage.
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