Recovery of the Epiphytic Lichen Flora Following Air Quality Improvement in South-West Sweden
Authors: Hultengren, Svante; Gralén, Helena; Pleijel, Håkan
Source: Water, Air, and Soil Pollution, Volume 154, Numbers 1-4, May 2004 , pp. 203-211(9)
Abstract:The development of the epiphytic lichen vegetation on tree trunks inside and nearby twelve towns and industrial areas in south-west Sweden was investigated 1986/88 and 1997 using a photographic technique. The lichen vegetation studied in terms of area cover as well as the air pollution sensitivity and preference for nitrogen of the individual lichens. During both surveys the lichen flora was strongly impoverished in urban areas compared to suburban areas and especially to the countryside (reference) areas nearby. The air pollution situation has improved in the area both before and during the study period. This holds especially for SO2, to a lesser extent also for NO2. Following the improvement of the air quality, an increased lichen area cover on the tree trunks was observed. Also the cumulative pollution sensitivity of the lichens present was higher in 1997 compared to 1986/88 in suburban and countryside areas. For the nitrogen impact, the increase from 1986/88 to 1997 was smaller than for pollution sensitivity, but still statistically significant. The trends are interpreted as signs of a normalisation of the lichen flora. It is concluded that the observed pattern of lichen recovery reflects the fact that the reduction of the air pollution level in the central parts of the towns is still not large enough to permit a large-scale recovery of the lichen flora, while in the suburban areas and the countryside next to the towns, the air quality has now improved to an extent, which permits the reinvasion of a number of lichens.
Document Type: Research article
Publication date: 2004-05-01