SO2 :: Sphagnum moss

Latin name: 
Sphagnum spp.

Impact Type: Direct exposure to pollutant

Key Concerns:

The virtual absence of Sphagnum species from the blanket bogs of the southern Pennines has been attributed to high SO2 pollution (Ferguson & Lee 1983a,b). Of the 18 species of Sphagnum reported in the area in 1913, only 5 were recorded in 1964 (Tallis 1964) and of those only S. recurvum is common today (Press et al. 1983).

Fumigation experiments by Ferguson et al. (1978) have shown that SO2 can severely inhibit the growth of ombrotrophic species of Sphagna (i.e. S. imbricatum and S. tenellum) at 131µg m-3 SO2, while minerotrophic species of Sphagna (i.e. S. recuvum) are more tolerant of sulphur (Lee et al. 1993).

Additional Comments:

It is not clear to what extent the effects on the Southern Pennines were a result of high SO2 concentrations or high S deposition.

Although SO2 concentrations declined steeply in the 1950s-1970s, no marked recovery of Sphagnum cover occurred in the southern Pennines due to increasing concentrations of nitrogen pollutants which thus assumed the dominant role in determining poor growth of Sphagnum species in the 1980s and 1990s. 

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).

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References: 
Ferguson, N.P.; Lee, J.A. 1983 Past and present sulphur pollution in the southern Pennines. Atmospheric Environment Atmospheric Environment 17 1131-1137
Ferguson, N.P.; Lee, J.A. 1983 The growth of Sphagnum species in the southern Pennines. Journal Bryology 12 579-586
Lee, J.A.; Parsons, A.N.; Baxter, R. 1993 Sphagnum species and polluted environments, past and future Advances in Bryology 5 297-313
Press, M.C.; Fergusson, P.; Lee, J.A. 1983 Two hundred years of acid rain Naturalist 108 125-129
Tallis, J.H. 1964 Studies on southern Pennine blanket peat. 111. The behaviour of Sphagnum Journal of Ecology 52 345-353

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