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

Abstract

Abstract During 1996/1997, the total epiphytic flora (lichens and bryophytes) of Olea europaea was studied at 52 representative sites from an industrial area of the Tagus valley-Abrantes region (Portugal). The Index of Atmospheric Purity (IAP) based on floristic richness was calculated at each site. The new data 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 the different IAP zonation on the two dates. With the aim of detecting affinities between sites with similar epiphytic composition and various environmental variables, a factorial analysis (Redundancy analysis-RDA) was used. The conclusion of this study, was that the epiphytic richness was deteriorating, probably as a result of an increase in SO2 concentration, as well as other atmospheric pollutants. As a result, some of the species had become rare or had disappeared during this period. The distribution of some epiphytic species of lichens and bryophytes sensitive to SO2 pollution is also presented.