Epiphytic lichens associated with different traffic intensities along the highway E4

Abstract: Inventories of epiphytic lichens on Scots pine (Pinus sylvestris) were conducted at three sites in east central Sweden: along the newly build motorway (Road E4), along the old road (Road 600) and in a reference site, to compare the effects of traffic pollution on lichen diversities. At each site, species richness, lichen mean sensitivity value (MK), air quality index of the forest stand/sample plot (LKI) and nitrogen impact value (N) were calculated and it was tested if there was any difference between the sites. Twenty-four species were observed in total, and Parmeliopsis ambigua and Hypogymnia physodes were the most common species at all sites. At Road E4, fewer lichen species were observed than at the other sites and this might be due to the impact of air pollution. The species richness at Road 600 was similar to that of the reference site, which might be explained by the improved air quality. These results imply that some lichens may disappear or recover at fast pace with the change in pollution intensities. Yet, lack of previous lichen data prevented further analysis of the impact of air pollution on the lichen diversity. In terms of the air quality indices, they did not result in the expected pattern of better air quality at a lower-polluting site since the results were influenced by the only minor differences. Hence, the results of the air quality assessment based on these indices were not reliable in this study. Furthermore, the nitrogen impact value was not the relevant index since all the recorded species were acidophytes. The study area was a forest environment with high microenvironmental variables and a relatively low pollution level.