Indicator value

Indicator value is a term that has been used in ecology for two different indices. The older usage of the term refers to Ellenberg's indicator values, which are based on a simple ordinal classification of plants according to the position of their realized ecological niche along an environmental gradient. More recently, the term has also been used to refer to Dufrêne & Legendre's indicator value, which is a quantitative index that measures the statistical alliance of a species to any one of the classes in a classification of sites.

Ellenberg's indicator values were the first model of bioindication proposed and applied to the flora of Germany, and they have a long tradition in interpretation and understanding of plant communities and their evolution. The latest edition of Ellenberg's indicator values applies a 9-point scale for each of six gradients: soil acidity, soil productivity or fertility, soil humidity, soil salinity, climatic continentality and light availability. Indicator values also exist in Landolt's Flora of Switzerland and some other floras. A substantial advance on a comparable scale to place a local flora on gradients are the climatic profiles of the French SOPHY online database.

This indicator value is an integral part of the indicator value , which quantifies the fidelity and specificity of species in relation to groups of sites in a user-specified classification of sites, and tests for the statistical significance of the associations by permutation.

The indicator value of species i for class j is obtained with the equation

Here

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