Determining the Impacts of Sub-Surface Irrigation on Sphagnum Moss Carbon Uptake in a Reclaimed Peatland

English Abstract:

Sphagnum biomass production is a feasible and sustainable alternative to current peatland harvesting practices; however, maintaining optimal hydrological conditions for fiber accumulation (i.e. net carbon sequestration) can be challenging, and water requirements remain uncertain. The objectives of the research are to evaluate the efficacy of different sub-surface irrigation techniques on water distribution within Sphagnum fiber production plots, and to assess the optimal hydrological conditions for Sphagnum biomass accumulation. An abandoned block-cut peatland in Shippagan, New Brunswick, has been manipulated to control the water table in six Sphagnum biomass production basins. The hydrology of each basin is controlled by a change in irrigation arrangement or position of the water table (-20cm or -10cm) below the surface. Instantaneous CO₂ fluxes under various light conditions were measured to calculate the gross ecosystem productivity (GEP) of each basin. GEP values were compared to various hydrological variables, such as water table level, soil water tension, and volumetric soil moisture content. Preliminary data suggests that there is a weak relationship between instantaneous water table and carbon flux measurements, but there is a strong relationship between the average seasonal mean water table and productivity values between basins with sub-surface irrigation. The most productive site had an average seasonal water table of -7.8 cm and GEP of -4.1 g C m^-2 d^-1. The two least productive sites were the only basins without sub-surface irrigation, and had average seasonal water table of -14.1 cm and -8.1 cm, and GEP of -3.0 C m^-2 d^-1. and -2.5 C m^-2 d^-1, respectively. The least productive site had a high water table (-8.1 cm), but combined with saturated soil conditions and frequent pooling of water at the surface, could indicate that frequent saturation may decrease productivity, and that sub-surface irrigation is a better method of water management.