Chasmophytic vegetation of crevices, rocky ledges and faces of rocky cliffs and walls of Europe, North Africa, Middle East, the Arctic archipelagos and Greenland
Asplenietea trichomanis (Br.-Bl. in Meier et Br.-Bl. 1934) Oberd. 1977
Asplenietea trichomanis (Br.-Bl. in Meier et Br.-Bl. 1934) Oberd. 1977
asp01 | The Asplenietea trichomanis is a particularly heterogeneous class. These rupicolous plant communities differ not only in species composition, alpha diversity and ecology, but also in overall structure, prevailing life form, and evolutionary history. Especially in the Mediterranean, the cliff habitats have served as refugia for plants to survive unfavourable climatic conditions as well as grazing pressure. There are a large number of plants exclusive to vertical rock, many of them being regional or local endemics. Researchers generally use different plot sizes when exploring plant communities dominated by hemicryptophytes or by nanophanerophytes. It seems therefore reasonable to assemble into one class only those plant communities of comparable plot size and life form. When applying these considerations as criteria to the Asplenietea trichomanis, the class would have to be split to accommodate herb-dominated rocky-fissure dwelling vegetation, and other assemblages dominated by shrubs and chamaephytes (commonly taxonomically isolated relicts such as in East Mediterranean cliffs). Various ecologically and phytogeographically segregated classes have been suggested to encompass 'nitrophilous' chasmophyte communities (Cymbalario-Parietarietea), communities of wet rocks (Adiantetea), communities of Iberian and North African overhanging rocks (Petrocoptido pyrenaicae-Sarcocapnetea enneaphyllae), epiphytic and rupicolous communities of Mediterranean oceanic conditions (Polypodietea), the Canarian Greenovio-Aeonietea and the Ibero-North African chasmophytic vegetation of the Phagnalo-Rumicetea indurati. This concept, however, seems unbalanced and does not satisfactorily structure the enormous range of rupicolous vegetation types. (E. Bergmeier, L. Mucina).