Impact Type: Deposition of pollutant
In a forest experiment where Sitka spruce received 50 kg N ha-1 yr-1 as NH4NO3 there were no negative effects on the understory Polytrichum commune (Sheppard pers comm.). Generally this moss seems fairly tolerant of wet deposited N. An insitu experiment where 30 kg N ha-1 yr-1 was applied to a cutover bog in the Jura mountains on Switzerland (ambient deposition 15 kg N ha-1 yr-1 ) showed positive responses (+100%) in the growth of P.strictum for 3 years (Mitchell et al 2002). In this study P.strictum expanded at the expense of Sphagnum fallax.
P. jumperinum likewise tends to dominate communities suppressing lichens and other bryophytes in response to N, although additions >10 kg N ha-1 yr-1 inhibit nitrate reductase (Gordon et al 2001).
|Critical Load/ Level|
No comparable habitat with established critical load estimate available