Net primary production (NPP), decomposition, changes in C, N and TP tissue concentrations and responses to N or P fertilization of aboveground vascular vegetation along a bog--fen--marsh peatland gradient in central Alberta, Canada, were measured during the 1993 and 1994 growing seasons. The peatlands were a bog, an open rich fen (ORF), a lacustrine sedge fen (LSF), a riverine sedge fen (RSF), a riverine marsh (RM) and a lacustrine marsh (LM).

Total plant NPP of the bog and the fens were similar but significantly lower than that of the marshes. The plant production values obtained conform to a latitudinal gradient for North American wetlands, although the marshes of this study were substantially less productive than Canadian counterparts at similar latitudes. Moss and herb production varied significantly between years and among sites, whereas shrubs production only varied significantly among sites but not years.

Litter quality and the surface water nutrient status of the sites partially explained the rates of decomposition of the dominant and standard plant litters and cellulose (filterpaper) over varying lengths of time. Decay of the plant litter was similar in fens and marshes, but cellulose decomposed significantly faster in the eutrophic marshes than in the oligotrophic fens. Nitrogen and phosphorus surface water parameters related best to litter decay in these peatlands. The carbon to nitrogen (C:N) ratio changes during plant litter decay depended on the litter type and quality and the surface water nutrient concentrations within sites. The nutrient status of the site, plant species, life history and stand density partly explained the C:N ratio changes throughout the growing season. Generally, C:N ratios decreased towards late August.

Fertilization with N or P generally did not reveal which nutrient limits plant production in Alberta peatlands. In the bog, ericaceous and deciduous shrubs, mosses and herbs were variable in their responses to fertilization. Fen and marsh plant species generally did not respond significantly to N or P addition, possibly due to luxury consumption of the fertilizers or immediate microbial uptake.