N deposition :: Sphagnum moss

Impact Type: Deposition of pollutant

Key Concerns:

There is extensive evidence to suggest that increasing N deposition is affecting the growth and metabolism of ombrotrophic Sphagnum species (Press et al.1986, Van Der Heijden et al. 2000, Nordin & Gunnarsson 2000). Experimental additions of nitrate and ammonium within the range observed in rainfall in the southern Pennines reduced the growth of Sphagnum cuspidatum (Press et al. 1986) and the decline in health and survival of Sphagnum communities in areas of Wales and the southern Pennines has been related to increased atmospheric N deposition (Woodin & Farmer 1993). Tissue N content of ombrotrophic Sphagna is also related to N deposition, being much larger in areas of high N deposition (e g. Cumbria) than in the cleaner areas of North West Scotland (Pitcairn et al. 1995). Svensson (1995) found that mosses, in particular S. fuscum, can capture mineral nutrients early in their circulation through the ecosystem and retain and relocate them within themselves, so countering the potential spread of vascular plants.

Additional Comments:

Additional growth of grasses and reduction in Sphagnum growth following N addition discussed by Hoosbeek et al. (2001) and Berendse et al. (2001) led to a decrease in carbon sequestration for the atmosphere. Jauhiainen et al. 1998 showed a relationship between capitulum size, the number of exchange sites, and N uptake (e.g. S.pulchrum, S.fallax, S. papillosum & S. magellanicum are very effective at absorbing N).