Indicator value is a term that is used in the

ecology Ecology () is the natural science of the relationships among living organisms and their Natural environment, environment. Ecology considers organisms at the individual, population, community (ecology), community, ecosystem, and biosphere lev ...

of plants for two different indices. The older usage of the term refers to Ellenberg's indicator values from 1974, which are based on a simple ordinal classification of plants according to the position of their realized

ecological niche In ecology, a niche is the match of a species to a specific environmental condition. Three variants of ecological niche are described by It describes how an organism or population responds to the distribution of Resource (biology), resources an ...

along an environmental gradient.Ellenberg H. Zeigerwerte der Gefässpflanzen Mitteleuropas / H. Ellenberg // Scripta geobotanica. Göttingen, 1974. – Vol. 9. – 197 p. Since 1997, the term has also been used to refer to Dufrêne & Legendre's indicator value, which is a quantitative index measuring the statistical alliance of a species to any one of the classes in a classification of sites.

According to Ellenberg

Ellenberg's indicator values were the first model of bioindication proposed and applied to the flora of Central Europe, 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 seven gradients: R - reaction (soil or water acidity/pH)
N - nitrogen (but really soil fertility or productivity, and not mineral nitrogen)
F - soil humidity or moisture
S - salt (

soil salinity Soil salinity is the salt (chemistry), salt content in the soil; the process of increasing the salt content is known as salinization (also called salination in American and British English spelling differences, American English). Salts occur nat ...

)
K - climatic continentality
L - light availability
T - temperature Indicator values have also been published in 1977 by Elias Landolt for Switzerland, by Mark O. Hill and others for Great Britain, France (Baseflor, SOPHY, Ecoplant) and some other floras.

According to Dufrêne and Legendre

The indicator value of Dufrêne and Legendre from 1997 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 In statistical hypothesis testing, a result has statistical significance when a result at least as "extreme" would be very infrequent if the null hypothesis were true. More precisely, a study's defined significance level, denoted by \alpha, is the ...

of the associations by

permutation In mathematics, a permutation of a set can mean one of two different things: * an arrangement of its members in a sequence or linear order, or * the act or process of changing the linear order of an ordered set. An example of the first mean ...

.De Caceres, M., P. Legendre, and M. Moretti. 2010. Improving indicator species analysis by combining groups of sites. Oikos 119:1674-1684. The indicator value of species ''i'' for class ''j'' is obtained with the equation :''IndVal_ij'' = 100 · ''A_ij'' · ''B_ij'' Here :''A_ij'' is specificity, i.e. the proportion of the individuals of species ''i'' that are in class ''j'' :''B_ij'' is fidelity, i.e. the proportion of sites in class ''j'' that contain species ''i''

References

{{DEFAULTSORT:Indicator Value Measurement of biodiversity Environmental and ecological indicators