Factors of Importance for the Epiphytic Vegetation of Aspen Populus tremula with Special Emphasis on Bark Chemistry and Soil Chemistry

6. There is a need to investigate further the bark-soil relationships and the mechanisms of possible interactions. If the epiphytic species are indirectly affected by the soil through influences on the bark, this could have consequences for conservation management intended to preserve epiphytic species as well as for the use of bryophytes and lichens as indicators of air pollution.