Concentrations of N, P, S, Na, K, Mg, Ca, Mn, Fe, Cu, Cd, Zn, Pb, Al, and AIA (acid insoluble ash) m mosses (three Sphagnum species and Tomenthypnum nitens, all hummock species) from a variety of mires, both ombrotrophic and minerotrophic, in the coastal western and central parts of Canada are considered in relation to surface water pH and concentrations of Na+, K+, Mg2+, Ca2+, Cl−, and SO42‐ Distinct west‐east concentration gradients were present for most elements in both mosses and water, but there were correlations between surface water and moss concentrations only for Ca and Mg On ombrotrophic sites and sites characterized by poor fen vegetation, wet deposition is the main source of elements in the surface water On rich fen sites, additional Ca and Mg from surrounding soils change the elemental proportions We conclude that hydrochemically the limit between poor and rich fen sites is more decisive than between bog and fen The increase in Ca may give brown mosses a competitive advantage over Sphagnum Moss concentrations of Na and Mg are the only ones decreasing inland The constancy or inland increase of moss elemental concentrations may depend on either an increasing atmospheric supply (e g Pb), differences in moss growth rates (especially N, P, and K) or site conditions related to the water regime (e g Fe and Al)

Microsite and regional vanation in the potential decay rate of Sphagnum magellanicum in south Swedish raised bogs -Ecography 17 50-59In southern Sweden there are regional gradients in the rate of atmosphenc deposUion of nitrogen, and the rate of N deposition has increased in recent decades This may have caused a shift in the growth-limiting nutnent of Sphagnum growth from nitrogen to phosphorus In this study, the influence of N and P concentrations on the decay of litter peat formed by Sp'iagnum magellanicum was examined A total of 90 litter peat samples formed by this species was collected from 15 raised bogs (3 sites per bog, 2 microsites per site) Total N and P of samples were determinecl and the rate of decomposition (COi release) was measured under aerated, laboratory conditions at 18°C Differences in decomposition rates, N and P concentrations were most pronounced among microsites within sites, whereas no significant differences were observed among bogs The results indicate that decomposition of 5 magellanicum litter peat IS influenced more by P than by N Thus, it appears that the recent increase in atmosphenc N deposition has not had a large direct effect on peat decomposition rates It IS suggested that the efficient uptake of N and P by the Sphagnum plant may lead to a positive feedback mechanism, whereby more slowly growing Sphagnum produces more nutrient-ennched litter peat with a more rapid decay Such a mechanism could promote the development of microtopography (hummocks and hollows) on bogs