Multivariate Approaches to the Ecology of Algae on Terrestrial Rock Surfaces in North Wales

Abstract

In the present study quantitative and qualitative data on terrestrial algae were collected from two restricted areas in North Wales, and their ecology is discussed in the light of the multivariate analysis of these data. The use of modern multivariate techniques for analysis of ecological data is rare in algology. The only other use of ordination in algology, is Abou-Elkheir's (1966) investigation of some tropical freshwater algae. Even in her study the ordination was a secondary part of the work. Data of a type suitable for ordination techniques (i.e. records of species occurrence at a large number of sites) are, however, fairly commonly collected by algologists but much of the information in such data is usually ignored because powerful techniques of analysis, such as ordination, are not used. One example which is particularly related to the present study is that of Marchesoni (1939) on the occurrence of a large number of species recorded for thirty-seven epilithic collections of algae in the Alps of northern Italy. Marchesonis conclusions are reached intuitively and probably only the more obvious ecological trends are detected. A very useful and concentrated literature review of epilithic algae was made by Fritsch (1945). One of the most extensive works published of epilithic algae is by Golubic (1967), in which a phytosociological approach involving subjective classification of communities (after Braun-Blanquet 1951) is taken. The phytosociological section of the investigation of large epilithic algae by Jaag (1945) is on a similar basis.