Cryptogamic epiphytes as indicators of air quality around an industrial complex in the Tagus valley, Portugal. Factor analysis and environmental variables

During 1996/1997, the total epiphytic flora (lichens and bryophytes) of Ole a europaea was studied at 52 representative sites from an industrial area o f the Tagus valley-Abrantes region (Portugal). The Index of Atmospheric Pur ity (IAP) based on Aoristic richness was calculated at each site. The new d ata were compared with original data sampled in 1986/1987 in the same area. There was a general decline in the air quality, which is demonstrated by t he different IAP zonation on the two dates. With the aim of detecting affin ities between sites with similar epiphytic composition and various environm ental variables, a factorial analysis (Redundancy analysis-RDA) was used. T he conclusion of this study, was that the epiphytic richness was deteriorat ing, probably as a result of an increase in SO2 concentration, as well as o ther atmospheric pollutants. As a result, some of the species had become ra re or had disappeared during this period. The distribution of some epiphyti c species of lichens and bryophytes sensitive to SO2 pollution is also pres ented. (C) 2000 Adac / Editions scientifiques et medicales Elsevier SAS.