Hydrogen sulphide and epiphytic lichen vegetation: A case study on Mt. Amiata (Central Italy)

A survey aimed at studying the effects of hydrogen sulphide (H2S) on epiphy tic lichen vegetation was carried our at Acquapassante (Mr. Amiata, Central Italy). In 1992, lichen vegetation was surveyed using a sampling grid of t en units, on 18 chestnut trees along a transect from a chimney emitting H2S to c. 200 m in the direction of the prevailing winds. A Lichen Biodiversit y Index (LBI) was calculated as the sum of the frequencies of all species p resent within the grid. The same survey was repeated five years later. Conc entration Analysis was applied to describe the data structure, and Procrust es Analysis was used to verify the congruence between the ordinations of 19 92 and 1997. The statistically significant linear and non-linear regression s found between environmental variables (distance of releves from the chimn ey, bark pH, lichen biomass of selected foliose and fruticose species, tota l sulphur content of Evernia prunastri, Hypogymnia physodes, Parmelia sulca ta and Ramalina fastigiata) and the position of the releve points on the or dination axes suggest that species distribution along the transect is relat ed to differences in H2S tolerance. However, some crustose species (Lecanor a cf. conizaeoides, L. saligna and Scoliciosporum umbrinum) should be proba bly excluded from the computation of the LBI for monitoring purposes, as th eir optimum is in the immediate vicinity of the H2S source. (C) 1999 The Br itish Lichen Society.