Biogeochemical processes in the soil-groundwater system of a forest-peatland complex, North Coast British Columbia, Canada

There is a limited understanding of the distribution and transport of solutes in the coastal forest-peatland systems of northern British Columbia, Canada. The purpose of this research was to evaluate the sources, concentration and flux of major ions and dissolved organic carbon (DOC) in the soil-groundwater system of a forest-peatland complex in the coastal western hemlock (CWH) forest zone. DOC dominated the groundwater flux, with most of it exported during high flow conditions. Inorganic ion concentration increased and DOC decreased with ground surface slope and community type from open peatland to bog woodland, bog forest, swamp forest and upland forest. Base cations, HCO₃^- and DOC in the peatland forest communities differed significantly (P < 0.05) from concentrations in the upland forest. The greatest concentrations of ions derived from mineral weathering were found in the upland forest where the absence of peat, deep mineral soil (85-465 cm) and steep surface slope (26%) combined to increase dissolution by recharging groundwater. NO₃^-, SO₃^2- and PO ₄ ^3- were at or below detection limits. Concentrations of DOC, metals and HCO₃ ^- decreased from summer to spring with dilution by rainfall and decreasing decomposition. In addition to providing novel data in a data-sparse region, this study provides an analysis of the processes controlling runoff production and the transport and transformation of biogeochemical elements impacting stream water quality.