Does nitrogen addition to raised bogs influence peat phosphorus pools

Abstract

Two Sphagnum moss species occupying hummock areas (Sphagnum capillifolium) and wetter hollows (Sphagnum recurvum) on a raised bog in north east Scotland were treated every two weeks with NH4NO3 solutions to supply 3g N m−2 yr−1. Although S. recurvum moss contained a greater concentration of total P than S. capillifolium the amounts and N:P ratios were similar in both species. Larger amounts of total dissolved P (TDP) and molybdate reactive P (MRP) were extracted from beneath S. recurvum to 25 cm below the moss. Additions of N both increased and decreased the amounts of TDP at different times, and decreased MRP. The MRP fraction accounted for about 20 per cent of TDP and the difference was assumed to be in organic forms (DOP). Nitrogen addition had no effect on the amounts of DOP, but C:P ratios of this fraction changed with species, depth and N addition. Microbial P accounted for as much as 70 per cent of total P and showed seasonal variations, but no differences between the two moss species and N addition.