Impact Type: Deposition of pollutant
Key Concerns:
The Usneaceae are characterised by a broad strap based thallus attached usually to trees, by a basal sheath. Usneas have a filamentous thallus with primary and secondary branches and are known as the beard lichens. They often cohabit tree trunks with mosses preferring damper regions especially the west coast. Those growing on trees as opposed to rocks or fence posts will be semi protected by the filtering effect of the tree canopy from direct effects of the H+ ions (Gilbert 1968).
Usnea spp. are highly sensitive to SO2, and are also believed to be sensitive to acidic deposition (Seaward & Hitch 1982).
Additional Comments:
There is very little literature published on the effect of air pollution on this genus.
| Critical Load/ Level |
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No estimate available |