Effects of water type on sphagum growth

Some Sphagnum species grow only in the lag zone of bogs while others grow in the central and higher part of it. This vertical zonation is not the result of colonisation of an array of existing habitats above the water table: Sphagnum mosses build the hummock-hollow gradient themselves. We hypothized that sites along the hummock-hollow gradient have a specific ionic ratio. This ionic ratio, the ratio between bivalent cations (calcium and magnesium) monovalent cations (potassium and sodium) seems to give a good explanation for the occurrence of different Sphagnum species in the field. The present research was done to reveal the influence of the ionic ratio on the biomass of Sphagnum under controlled conditions. If Sphagnum species grow on a rather species-specific ionic ratio, this ratio may be an important selecting mechanism in the occurrence of Sphagna along the hummock-hollow gradient. Sphagnum niagellanicum (hummock species), Sphagnum recurvum (intermediate species) and Sphagnum majus (hollow species) were treated with four water types. Each water types had a species-specific ionic ratio. This pilot study seems to point out the ionic ratio as well as the total ion concentrations seem to influence the growth of Sphagnum. However, Sphagnum species do not have a rather narrow tolerance for a speciesspecific ionic ratio.