Bryophyte community composition and habitat specificity in the natural forests of Terceira, Azores

In order to characterize the main areas of natural forest on Terceira Island (Azores), some of the most interesting European forests due to their rich and diverse flora of endemic as well as relict species, six forest stands were studied and their flora inventoried using 226 randomized quadrats, which revealed one anthocerote, 64 liverworts, 41 mosses and 16 macrolichen taxa. The alpha-diversity of the samples is particularly species-rich, some quadrats (30 x 30 cm) including more than 25 bryophyte species. A quantitative analysis of the vegetation-environment relationships consistently showed that the distributions of the native forest bryophytes and lichens of Terceira are governed by a complex set of factors related to water availability, the status of the substrata and the influences of the vascular plant community. Considering the generally high values of the Sorensen indices and the low number of specialist species found with Lloyd's index, the differences are more in terms of dominance of species than in terms of species composition. In fact, substratum type was clearly important in the DCA and TWINSPAN analysis using species cover abundance values, largely explaining the distribution of bryophyte species between Juniperus brevifolia (Seub.) Antoine and Laurus azorica (Seub.) Franco bark. The eight putative plant community type groupings achieved with these multivariate methods were able to elucidate some major bryophyte - substratum relationships, that had not previously been considered and they offer a framework for future research.