| 1. Based on a literature search and the study of 300 samples of saxicolous calcifuge lichen communities obtained with the "total sampling" method along several watercourses in continental France, the authors propose the nomenclature of "ekreophilic" for lichens developing on rocks subjected to prolonged water flows and "hydrophilic" when they colonise supports subjected to periodic immersion by watercourses. 2. Statistical analyses of the 300 samples show the existence of three groups defined by their contact times with water. The authors propose the names "subhydrophilic", "mesohydropilic" and "hyperhydrophilic" for lichens in the upper part of the minor bed, the lower part of the minor bed and in the low-flow channel, respectively. 3. A new classification for phytosociology, or plant communities, is proposed. It is defined by the existence of one class of hydrophilic lichens, three orders corresponding to the different times of contact with water, six alliances that depend on bioclimatic stage and finally several associations whose flora compositions should be defined by further work. Research perspectives resulting from this new ecological concept, and the role of symbiotic organisms in phanerogam colonisation of land exposed by receding water are discussed. |
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