Impact Type: Deposition of pollutant
Montane heaths, which are dominated by Racomitrium lanuginosum, have declined in distribution and health in recent decades (Ratcliffe and Thompson 1988). Both land use changes and atmospheric N deposition have been implicated in the decline (Thompson & Baddeley 1991). The tissue N content of the moss was shown to be least in north-western Scotland and greatest near urban areas of northern England (Pitcairn et al. 1995). The importance of atmospheric N supply in determining the tissue N content of the moss was demonstrated by transplant studies between regions (with different N deposition) and between sites within a mountain system. Increases in tissue N content may affect the N assimilation processes, decomposition and the partitioning of N between the various components of the ecosystem (Baddeley et al. 1994). Increased N content may make the moss more attractive as a food source.
There are substantial effects of nitrogen deposition on bryophytes, making it difficult to separate the effects of acidification from those of eutrophication. R. lanuginosum abundance is also effected by climate change (Tallis 1995). Two recent experiments have confirmed the sensitivity of Racomitrium to wet deposited N (Jones et al. 2002, Pearce and van der Wal 2002).
|Habitat/ Ecosystem Type||Eunis Code||Critical Load/ Level||Status||Reliability||Indication of exceedance||Reference|
|Moss and lichen dominated mountain summits||E4.2||
5-10 kg N ha-1 year-1
|UNECE 2010 - Noordwijkerhout workshop||quite reliable||
Effects upon bryophytes or lichens.