In 2000, a standardized sampling protocol was developed by a group of European researchers to provide a repeatable and
objective strategy for mapping lichen diversity as an indicator of environmental changes; this protocol is nowadays adopted in
the guidelines to air quality bioindication in Italy.
The present paper shows the results of a study of epiphytic lichen diversity performed according to both the new protocol
and the standard methodology previously used in Italy; diversity values are based on frequency counts of all lichen species
within particular sampling grids positioned on the trunks and divided in subunits. The survey was carried out in 61 sampling
sites of two areas of the Friuli Venezia Giulia region (Italy) and Slovenia, characterized by similar climatic conditions and a
wide range of anthropic pressure. Biodiversity values obtained following the two sampling methods are highly statistically
correlated; this suggests an interpretative continuity of lichen diversity data for biomonitoring purposes. Lichen communities
and diversity values occurring in natural areas, far from heavy human influences, are investigated by means of multivariate
analysis of floristic releve´s of 11 sites. Diversity values scored in natural areas are rather variable, and are mainly influenced by
the different vegetation types, Parmelion communities having lower diversity values than communities with Xanthorion
elements. Evaluation scales of environmental alteration based on lichen diversity in the North Adriatic submediterranean
bioclimatic area are provided. Some critical aspects of the sampling strategies are discussed.
