Ecological groups

In 1969, Thange laid the foundations of the ecological groups for southern Belgium. These are defined as a set of forest plants that share the same ecological niche. These ecological groups are since then commonly used in southern Belgium for the description of forest sites.

The ecological groups are defined by Duvigneaud (1974) as a set of species having a more or less great sociological affinity between them, marked by a tendency to gather in a determined biotope, i.e. in determined environmental conditions.

The ecological groups of Belgium were revised in 2020 before the publication of an illustrated guide. It is this very recent version of the ecological groups that is presented in this web application. For more information, we recommend the new catalog of ecological groups;

The "Ecological Group" tab

This tab presents the list of groups and the species that constitute them. The catalog of ecological groups, located on the right, groups the different groups according to their indicator character of the trophic level. This catalog allows you to filter the groups in order to display only some of them.
The species present in the survey are displayed with a grey background.
In this tab, a click on the Latin name of a species willadd this species to the floristic survey.
To obtain a description of the ecological group, a double-click on the name of the group will open a window with additional information. Moreover, the ecological niche of the group is displayed in the ecogram after clicking on the group name.

The ecogramme matrix

The ecogram is the cornerstone concept at the heart of the Forest Trees Autecology Guide method. Sometimes used to define the aptitudes of forest species, sometimes to illustrate the distribution of indicator species, this hydro-trophic matrix deserves to be described. Especially since there are many different ecograms, mainly used in botany and ecology. But the key word is always the following; to represent graphically the different environmental conditions that prevail on a forest site. These environmental conditions are articulated around three major gradients; the climat, the moisture gradient and the nutrient gradient. Making the assumption that the climatic information available in Belgium allows a complete description of the entire Walloon territory, for which ten bioclimatic zones are defined, the two gradients likely to change locally are the availability of water (and oxygen to some extent) and the availability of mineral elements.

The ecogram that is shown on the left of Phytospy application does not include a legend. But, hovering the mouse cursor over a disk representing a hydro-trophic regime, a tooltip informs the appropriate label.

Reading the floristic diagnosis on the ecogram

As long as the floristic relevé contains indicator plants, an automatic prediction of nutrient and moisture regimes is performed. The nutrient and moisture regimes are predicted individually, because PhytoSpy uses two different models. The prediction results are drawn on the top for the nutrient gradient and on the right for the moisture gradient, and this is done in the form of sticks/bar whose size and color vary proportionally with the value of the prediction percentage. Indeed, the classification algorithm used is a Random Forest: this algorithm assigns to each regime a probability as a percentage. The regime that is assigned the highest percentage is the regime that is chosen by the classification algorithm. The stick for this regime is surrounded by the color yellow.

A minimum number of indicator species is required to obtain a valid prediction of nutrient and moisture regimes.

The predictive power of the nutrient regime by indicator species is high: the floristic determination of the availability of mineral elements is relatively precise. On the other hand, the indicator character of the water regime is less marked. This is why the floristic diagnosis is limited to the prediction of a group of moisture regime. Thus, a grouping of dry soils (regimes +3, +4 and +5), mesic soils (regimes +1 and +2), slightly wet soils (regimes 0 and -1) and wet or marshy soils (regimes -2, -3 and -4) is made. Soils with a fluctuating moisture regime, characteristic of a winter waterlogging period and a dry period during the vegetation period, are not subject to automated floristic determination. In these cases, the expert must make his own determination on the basis of the phytosociological relevé and taking into account the topographical and soils characteristics of the station.

Reference Documentation

Lisein, Jonathan, Adeline Fayolle, Andyne Legrain, Céline Prévot, et Hugues Claessens. « Prediction of forest nutrient and moisture regimes from understory vegetation with random forest classification models ». Ecological Indicators 144 (2022): 109446. https://doi.org/10.1016/j.ecolind.2022.109446.