Impact Type: Direct exposure to pollutant
Studies by Lawrence & Ashenden (1993) have shown that direct exposure to SO2 (exposure to 104 µg/m3 SO2) may affect the growth and reproduction of fern species. However it should be noted that such cases only now occur in Britain in the immediate vicinity of major sources.
There is a lack of information on the relative sensitivity of different fern species.
|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).