Potential NH4+ and NO3− uptake in seven Sphagnum species

The rate of nitrogen uptake by seven Sphagnum species, which from a gradient from hummock to hollow and from ombrotrophic to minerotrophic conditions, was measured as the decrease in the concentrations of NH₄⁺ and NO₃⁻ from solutions in which capitula were grown under laboratory conditions.
The highest uptake rate was by individuals of each species with large capitula and a high number of ion exchange sites, i.e. lawn species ( S. pulchrum , S. fallax , S. papillosum and S. magellanicum ). On a dry-mass basis, the most effective species were the hummock species ( S. fuscum and S. rubellum ), even though these species have a low dry mass. Hummock species, which occur in high densities and have high potential N-uptake rates on a dry-mass basis, were the most effective species in retaining available nitrogen.