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DIVISION S-10-WETLAND SOILS

Placic and Ortstein Horizon Genesis and Peatland Development, Southeastern Newfoundland

^a Eastern Cereal and Oilseed Research Centre, Agriculture Canada, Ottawa, ON, Canada K1A 0C6

lapend{at}em.agr.ca

There is considerable speculation about relationships between soil development and local-scale blanket bog formation in southeastern Newfoundland. This study examined podzolization along a catena in southeastern Newfoundland. The specific objective was to investigate pedogenic processes, in particular placic and ortstein horizon development, as well as potential links between soil and peatland formation. Chemical, hydrological, and physical processes potentially responsible for pedogenesis were examined. Placic genesis appears to be linked to the precipitation of Fe at oxidizing and higher soil pH contacts at depth in the soil. Placic formation in the well-drained heathlands is apparently precluded by constraints on Fe mobilization at the surface, in particular, Fe-oxidizing conditions and the presence of sufficient supplies of metals neutralizing mobile organic substances. Organic-complexed Al is the dominant cementing agent in ortstein horizons. Cementation is augmented by minimal bioturbation by roots and high coarse-fragment content, which concentrates Fe and Al to a limited soil matrix. Weathering, podzolization, elevated water tables, and peatland processes are promoted by groundwater discharge from adjacent bogs as well as by sesquioxide pans that impede vertical drainage.

Abbreviations: Al_d, dithionite aluminum • Al_o, oxalate aluminum • Al_p, pyrophosphate aluminum • D_b, bulk density • Fe_d, dithionite iron • Fe_o, oxalate iron • Fe_p, pyrophosphate iron • K_sat, bulk hydraulic conductivity • K_x, horizontal hydraulic conductivity • K_z, vertical hydraulic conductivity • Mn_d, dithionite manganese • LB, lowland bog • LPF, lowland poor fen • OC, organic carbon • P1–8, pedon numbers • S, relative saturation • Si_o, oxalate silicon • TDR, time domain reflectometry • UB, upland bog • UPF, upland poor fen