The initial biometerology of the constructed Sandhill Fen Watershed in Alberta, Canada
Clark, M. G. 2018. Carleton University
Abstract
Resource extraction has led to the loss of boreal landscapes.Recently, novel
integrated landscapes have been constructed to return ecological functions lost due to
disturbance. The Sandhill Fen Watershed (SFW) is one of the first of two such projects in
the boreal plains ecozone. The SFW is a mix of upland, midland and lowland topographical
features designed to develop into integrated boreal plains ecosystems.This thesis
quantifies the initial carbon cycling dynamics within the SFW and contextualizes this
development with studies on conventional reclamation projects and undisturbed
ecosystems.
Construction, vegetation seeding and planting of the SFW was mostly completed
by 2012, and an initial wetting occurred in 2013.Methane fluxes remained low over the
first three years. However, mobile ions of sulphur declined over this same period and could
indicate shifting reduction-oxidation conditions favourable for future rates of
methanogenesis. In the lowland, biogeochemical fluxes were indicative of highly reduced
soil conditions. This was confirmed in 2015 with reduction-oxidation potential monitoring.
Downscaled eddy covariance flux measurements showed that vegetation increased
evapotranspiration (ET) rates in the lowland relative to non- vegetated water surfaces. S ince
there were no other substantial outflows of water from the SFW, greater rates of ET may
lower the water table in the future and limit the carbon storage potential of the ecosystem
through peat accumulation. Measurements of the CO2 exchange between the surface and
the atmosphere showed that, with no other substantial carbon outputs, by its third year the
SFW lowland had become a net carbon sinkand had daily, monthly, and annual carbon
cycling behaviour similar to undisturbed boreal wetlands. Net sequestration of CO2 in the lowland occurred because the design of the SFW promotedsaturated anoxic conditions
which suppressed soil respiration while also promoting hydrophytic vegetation
productivity. Since past efforts to restore degraded wetlands have not always succeeded in
recreating carbon cycling functions similar to those of undisturbed wetlands, the SFW may
be an effective approach to achieve post-mining landscape closure.
