Herbaceous vegetation of seasonally wet habitats on inselbergs and lateritic crusts in West and Central Africa

• Autores: Jonas V. Müller
• Localización: Folia geobotánica: A journal of plant ecology and systematics, ISSN-e 1874-9348, ISSN 1211-9520, Vol. 42, Nº 1, 2007, págs. 29-61
• Idioma: inglés
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• Resumen

  • lnselbergs, mountain ridges and lateritic crusts are characteristic landscape elements in many tropical regions. They are of great interest from a botanical point of view. Their vegetation is relatively uniform and differs from the surrounding vegetation. The first synopsis of herbaceous vegetation of seasonally wet or inundated habitats on rocks, inselbergs, mountain ridges and lateritic crusts in several bioclimatic zones of tropical West Africa and Atlantic Central Africa is presented. A classification of 43 partial data sets, based on 378 relev6s, resulted in four associations and several rankless communities, grouped into four different classes (Drosero-Xyridetea, Afrotrilepidetea pilosae, L),copodietea cernui and Microchloetea indicae). Plant communities from Atlantic Central Africa and West Africa are very distinct from a floristic point of view; in an ordination, they are clearly separated. The Drosero indicae-Utricularietalia subulatae (Drosero-Xyridetea) comprises ephemeral vegetation in rock pools and depressions over lateritic crusts. It contains the Eriocaulo pumili-Ophioglossion gomezianum, which combines communities with short-lived plant species in small pools on rock outcrops and in shallow depressions over laterite, and the Genliseo africanae-Sporobolion pauciflori, which colonizes similar habitats but is geographically restricted to few mountains in Guinea, Sierra Leone and Liberia. Mats of monocotyledonous plants (Afi'otrilepidetea pilosae, Afrotrilepidetalia pilosae) are very widespread in humid parts of tropical West Africa. They colonize gentle slopes and are often close to communities of the Drosero-Utricularietalia subulatae. Three alliances can be distinguished: West African alliances Cyanotido lanatae-Afrotrilepidion pilosae and Spermacoco hepperanae-Afrotrilepidion pilosae, and an Atlantic Central African Oreonesiono testui-Afrotrilepidion pilosae. Small-scale alterations of the ecological situation often result in a mosaic-like pattern of the plant communities. Especially small inselberg and rock outcrop habitats are often affected by heavy fluctuations of their environmental and climatic conditions. Besides regular short-term dynamics, there are also long-term vegetation dynamics with cycles spanning several years