Losses of dry mass of the dominant litter, a standard litter (Carer aquatilis), and cellulose (Whatman filterpaper) were examined by the litter bag technique in three fens (riverine sedge fen, lacustrine sedge fen, floating sedge fen) and two marshes (lacustrine marsh, riverine marsh). Local Carex lasiocarpa had a similar mass loss in marshes (mean of 63%) and in fens (mean of 59%) over 456 days in 1993 and 1994. Typha latifolia decomposed at a similar rate as the local C. lasiocarpa in the lacustrine marsh, whereas Salix pedicellaris decomposed significantly slower than the local C lasiocarpa in the floating sedge fen (FSF). Overall, the mass loss of the standard plant litter was not significantly different between the fens (mean of 72%) and the marshes (mean of 69%). However, cellulose decomposed significantly faster in the marshes (mean of 67%) than it did in the fens (mean of 28%) over 100 days in 1994. Decay of Carer aquatilis was best related to ammonium (NH4+) (r = 0.73) in fens and the water level relative to the peat surface (r = 0.74) in marshes. Standard plant litter decomposition was best explained by surface water concentrations of NH4+(r = 0.89) in fens and by soluble reactive phosphorus (SRP)(r = 0.89) in marshes. Cellulose decomposition was best related to SRP in fens (r = 0.70) and marshes (r = 0.64) alike. An arithmetic/logarithmic decay model most accurately described plant mass losses during decomposition (59%) compared to the widely used logarithmic/arithmetic model (12%).
