04 - Studia Geobotanica - An International Journal - Vol. 4 (1984)

In the course of numerical ordinations of Apennines woodlands, the problem arose of different performance of ordination methods, using different character sets and methods. To reveal underlying trends and relationships, 47 ordinations are jointly examinated, corresponding to combinations of 6 methods and 8 character types. The Spearman formula has been used to measure the similarity between different ordinations. The ordinations based on families are, on the average, the most similar to the other ones irrespective to the method used. The ordination based on detailed life forms (growth forms) are the least similar to the other ordinations. Ordinations based on the same character set and different methods could be different as well as ordinations based on different character sets and the same method. The suggested procedure can be the basis to select among different ordinations those explaining complementary informations.

Two examples of application of numerical classification and ordination methods to textural and chorological data of vegetation types defined with the Braun-Blanquet approach are presented.

Six community types of epiphytic lichen vegetation are reported from the Calamone Lake area (N-Apennines). Data analysis is based on multivariate methods. The ecological interpretation of the compositional variation was based on indirect gradient analysis. Each of the communities is well characterized in floristical. ecologica! and phytogeographical terms.

The efficiency of Intersection Analysis in producing species groups at different noise and sampling intensity levels has been tested on the basis of a simulated coenocline. The results suggest that lntersection Analysis is a robust method for detecting species groups and that it could be used in field surveys to find out the sampling intensity sufficient to describe the vegetation under study.