Classification and Ecology of Closed-Canopy Forest in Ghana

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Abstract
A practical classification of closed-canopy forest in Ghana is presented, based on the ordination by reciprocal averaging of the presence of 749 vascular plant species, including herbs, climbers and trees, in 155 plots of 0.0625 ha each, distributed through the forest zone. Soil samples from each plot were analyzed. Seven forest-types are recognized, named and mapped, and defined by areas on the 2-dimensional ordination diagram. Of the environmental parameters investigated, rainfall was the best correlated with the 1st axis of the ordination. Total exchangeable bases and pH of the soil were largely dependent on rainfall; in the drier types, forest composition was related to Ca content which varied with the nature of the underlying rock independently of rainfall. Other environmental factors affecting forest type include: altitude, topography and the occurrence of occasional fires in the litter layer. Floristic diversity, expressed as total species per plot, is correlated with the major floristic gradient, reaching 190 at the high-rainfall end of the gradient, and falling to 20 at the low-rainfall end. Deciduousness, and proportions of species with microphyll leaves, and with acuminate leaf apices, are also correlated with floristics. The advantages of using small plot sizes and recording all species present are discussed. Initial ordination of data from even a broad survey, and the use of ordination of the majority of species recorded, have the practical advantage that subsequently studied forest can readily be identified by co-ordinate estimation.