Influence of Air Pollution on the Epiphytic Lichen Vegetation and Bark Properties of Deciduous Trees in the Copenhagen Area
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The epiphytic lichen vegetation of trees in the Copenhagen area was mapped, and the pH, total sulphur content and buffer capacity of its substratum were measured. The SO2 air pollution during two consecutive winters was mapped. The SO2 isopleths coincide well with the inner distribution limits of the lichens, indicating specific critical SO2 levels for the different species. The critical level of Buellia punctata (Hoffm.) Massal. was 90-110 μg m-3 for Xanthoria parietina (L.) Th. Fr. 80-90 μg m-3, for Lecanora subfusca coll. 70-80 μg m-3 and for Physcia pulverulenta (Schreb.) Hampe 40 μg m-3. These species were considered useful as indicators for biological evaluation of SO2 pollution in the investigation area. The bark properties changed as follows on approaching the city centre: the average pH decreased from 5.0 to 3.0 whilst the average sulphur content in per cent dry weight increased from 0.25% to 0.45%. The buffer capacity of bark was higher both in the city centre and the rural districts than in the intervening area at the periphery of the city.
|Status||Udgivet - 1973|