Nutrient availability in the Mer Bleue bog as indicated by Plant Root Simulator probes

English Abstract:

There are a variety of methods employed to assess nutrient availability from soils, such as total analyses, differential extractions, laboratory incubations and pore-water analyses. The adsorption of nutrient cations and anions onto exchange resins placed in the soil provides an alternative approach. We used Plant Root Simulators (PRS^TM) at the Mer Bleue bog to provide some baseline data on nutrient availability and its variability. In particular, we focused on ammonium, nitrate, phosphate, calcium, magnesium and potassium, expressed as μg/cm²/week. We placed PRS probes at a depth of 5 – 15 cm in the bog for 4 weeks and determined the availability of these nutrients, from spring through to fall. Probes were also placed beneath the water table in hummock and hollow and along a transect including part of the bog which had been drained through the creation of a ditch 80 years ago. Probes were placed in the long term N (P+K) fertilization experiment. The result showed the paucity of available ammonium, nitrate and phosphate in the bog, a seasonal pattern associated with rates of mineralization driven by temperature, an increase in the availability of some nutrients as a result of drainage, and the relative availability of nutrients compared to the input from fertilization. We suggest that careful placement of the probes (e.g. exposure period, depth relative to water table etc.) may provide valuable information on variations in nutrient availability within and among wetlands.