NITROGEN AND PHOSPHORUS MINERALIZATION IN FENS AND BOGS

Release of inorganic N and P in 10 mires in The Netherlands with different vegetation and hydrology was measured. Size of the inorganic N pool was not related to depth, mire type or the presence of a Sphagnum cover. The labile inorganic P pool was significantly larger in Sphagnum-dominated bogs than in phanerogam-dominated fens. N and P mineralization were significantly faster in bogs with a Sphagnum cover than in phanerogam-dominated fens, and faster at 10 than at 25 cm. Cellulose decomposition rates were significantly higher in phanerogam-dominated fens. The depth patterns of the decomposition rates also showed a difference between these mire types: in fens, the rates were relatively low at the surface but increased to a sustained higher value at 10 cm and below; in bogs, the rates were highest at the surface but decreased steeply to very low values. The inverse relation between N and P mineralization and decomposition is probably due to the chemical properties of Sphagnum litter predominant in bogs. The N- and P-rich protoplasm breaks down and releases nutrients quickly, whereas the bulk of cell walls is decomposed so slowly that not much N and P is immobilized in microbial tissues. -from Authors