Relations between sociological-ecological species groups and Ellenberg indicator values
van der Maarei, Eddy
This study reports on a study on the relations between the ecological indicator values for light, moisture, reaction and nitrogen according to Ellenberg (1979) and a system of 80 sociological-ecological groups developed for the flora of the Netherlands. This system was refined on the basis of new or corrected information in Ellenberg (1991), some phytosociological revisions and some corrections of actual indicator values. The resulting groups are homogeneous for all four indicator factors, i.e. they have average values with a standard deviation of less than 1, meaning that 90 % of all values are restricted to maximally three adjacent indicator classes. With examples from the Littorelletea and Molinietalia, it is shown that the sociological-ecological groups are syntaxonomically heterogeneous, which implies that the syntaxonomical position of some species and vegetation units should be reconsidered. With an example of dune meadow relevés it is shown that the calculation of weighted averages for sites can be improved by subjecting the cover-abundance values to an 'optimum transformation', which relates the performance of species to the maximum performance reached by the species as based on growth form and growth rate. While underlining the need for additional field measurements this study suggests that the ecological indication values have a valuable element of synthesis and integration which incidental measurements may miss.