Environmental Engineering Reference
In-Depth Information
trains. Thus some of the first records from northeast England came from rural
railway stations (Gilbert
1980b
). Background air pollution then sustained its
progress. Britain was the first country in the world to be industrialised, and
it was the resulting air pollution here which created favourable conditions
and enabled it to spread so rapidly (Laundon
1973
). L. conizaeoides became
ubiquitous in areas where winter mean atmospheric SO
2
concentrations
ranged from 50 to 150
m
gm
3
(Seaward & Hitch
1982
). In Scandinavia, Lecanora
conizaeoides was recorded much later, in 1915 in Sweden (Gøteborg) and 1947
in Norway (Stavanger). The Norwegian distribution agrees with Ahti's (
1965
)
that is essentially suboceanic in distribution. However, occurrence at Hamar
indicates that it can withstand considerable cold temperatures in winter
(Tønsberg
1992
).
Imperial College London has a detailed record of the lichen flora on free-
standing oak trees along a 70-km transect extending south-southwest from
central London almost to the southeast coast of England (Bates et al.
1990
,
2001
; Bell et al.
2004
). Over a 21-year period, declines were observed in Lecanora
conizaeoides. A decline in cover was recorded over the period 1979 1999 at
nearly all stations, apart from the innermost site (Kensington Gardens), the
only station to retain appreciable SO
2
levels. When the transect was started
in 1979, it was absent at Putney Heath, by the mid 1980s as SO
2
levels fell, it
increased dramatically in cover. Then as SO
2
levels fell still further. the cover
fell to zero by 1998.
In North America, Lecanora conizaeoides was first recorded at St John's
Newfoundland by Teuvo Ahti in 1956 (Ahti
1965
). It subsequently appeared
in several North American cities and is believed to have been introduced
recently into eastern Massachusetts via soredia attached to lumber from a ship
(LaGreca & Stuzman
2006
). A similar pattern of invasion was recorded here as
in Europe. In eastern Massachusetts, L. conizaeoides was first recorded as colonis-
ing highly acidic (pH
4) wood (less often bark) in rural swamps of Atlantic
white cedar, subsequently spreading to other suburban sites which contain
sufficiently acidic substrates. However, in this case, acidification of tree species
at the suburban sites cannot be explained by high atmospheric sulphur dioxide
<
Figure 3.3.
(cont.)
relation to decreasing air pollution from the railway at Aviemore, Highland, Scotland.
Pollution arose from the continuous burning of coal at an engine shed built in 1896
which was in constant daily use for the shunting of steam locomotives until 1960. The
abundance of each lichen species was recorded by percentage cover or presence/absence
(Domain scale) using 11 80
20 cm quadrats on randomly selected mature vertical silver
birch Betula pendula boles in open-canopy birch woodland along a transect running
northeast downwind from the shed alongside the old bridle-road between Aviemore and
Dalfaber in 1868 (Laundon
2003
).
