SPATIAL AND TEMPORAL VARIABILITY OF ALGAL AND LICHEN EPIPHYTES ON TREES IN RELATION TO POLLUTANT DEPOSITION IN SWEDEN

Green algae on Norway spruce needles and lichens on Scots pine and birch bark have been monitored for four and ten years, respectively, within the National Swedish Environmental Monitoring Program (PMK). Their spatial and temporal patterns in Sweden were analyzed. Algal colony thickness and colonization rate on needles increased from north to south and from east to west, but also with length of growing season and amount of atmospheric N and S deposition. However, no clear temporal trend was found over the 10 yr monitoring period. In general, patterns for sensitive lichens were opposite to those observed for the algae. Weighted Mean Sensitivity (WMS) of lichens was determined to be the best index of air quality among three indices evaluated. WMS increased from south to north, from west to east, and decreased with increasing deposition of N and S. The observed geographic, pollutional and biological variables were highly correlated with each other. Therefore, the relationships between biological, and environmental factors cannot be clarified at the present time.