Biatora aegrefaciens – återfunnen efter 119 år

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Biatora aegrefaciens – återfunnen efter 119 år

62 Allan Pentecost & J. H. Williams GRAPHIS SCRIPTA 13 (2002)

Figure 2. Climatic data for the Snowdon Thamnolia sites during 1999 Precipitation (3-day

totals) at the Snowdon summit weather station.

dry and total acid deposition than did the 20

km × 20 km Cadair Idris square (Stevens et al.

1997). Another possible explanation is grazing

pressure. During summer, sheep graze the low

turf of Crib y Ddysgl and are bound to disrupt

thalli by trampling. There was clear evidence

of grazing adjacent to the sites so some

damage appears inevitable, but it is not clear

whether the intensity of grazing has varied

historically, or how trampling affects reestablishment

of the lichen fragments. Cooper

et al. (2001) noted damage to High Arctic

lichens and its amelioration by sustained

periods of precipitation. However at our

Snowdon sites there was no evidence of

regeneration of damaged thalli and the

population as a whole appears to be declining

rapidly. Another possible cause of these

changes is the global increase in temperature

over the past 30 years. Since Cadair Idris and

Snowdon receive almost identical weather, but

only Snowdon has suffered a decline in

Thamnolia, such changes are unlikely to be

the cause of decline.

Acknowledgements

We thank Dr. M. O. Hill for some of the

bryophyte identifications and Jack Grasse for

information on the distribution of Thamnolia

on Cadair Idris. The senior author is grateful

for a small travel grant from the British

Lichen Society.

References

Barry, R. G. 1981: Mountain weather and

Climate. Methuen, London and New

York.

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