SO2 :: Usnea species

Latin name: 
Usnea spp.

Impact Type: Direct exposure to pollutant

Key Concerns:

Usnea spp. are highly sensitive to SO2, and are also believed to be sensitive to acidic deposition (Seaward & Hitch 1982). Hawksworth & Rose (1970a) suggest that some species can tolerate up to 40 µg m-3 SO2 (U. subfloridana), U. ceratina and rubiginea can tolerate up to 35 µg m-3 SO2, and that U. florida under 30 µg m-3 SO2, with U. artculata and filpendula only found in area with pure air.

Additional Comments:

There is very little literature publi shed on the effect of air pollution on this genus. 

Critical Load/level: 
Habitat/ Ecosystem Type Critical Load/ Level Status Reliability Indication of exceedance Reference
Forests and semi-natural vegetation

20 µg SO2 m-3 annual mean and half-year(Oct-March) mean

UNECE, 2004 quite reliable i.e. the results of some studies are comparable

Low temperature appears to enhance the negative effects of SO2, and the lower critical level of 15 µg SO2 m-3 is used where the effective temperature sum (ETS) (i.e. the sum of temperatures) above 5oC is below 1000 degree days (d.d) (Ashmore et al., 1994).

809
References: 
Hawksworth, D.L.; Rose, F. 1970 Lichens as Pollution Monitors Studies in Biology (66)
Seaward, M.R.D.; Hitch, (Eds) C.J.B. 1982 Atlas of the lichens of the British Isles 1
Species group: 

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