Ecology of a key African multipurpose tree species, Balanites aegyptiaca (Balanitaceae): the state-of-knowledge

Abstract

Published information on the distribution of Balanites aegyptiaca (Linnaeus) Del. was assembled and summarised as a distribution map interpreted using soil and vegetation maps of Africa and the Middle East, meteorological data and information in the ecological literature. Balanites aegyptiaca is reported from most African countries and also from the Arabian peninsula and adjacent parts of the Middle East. Within Africa the range is from Mauritania in the west to Somalia in the east and from Egypt southwards to Zimbabwe. Occurrence south of the Sahara desert is generally related to rain-fed situations with a mean annual rainfall of 400–800 mm, but there has been spread to disturbed sites in wetter climates. Further north, Balanites aegyptiaca is present in numerous localities where sub-optimal rainfall is augmented with water from other sources. Other conditions associated with the species are a mean annual temperature 20°C and freedom from frost. Typical sites are level and low-lying, with relatively fertile loamy or clayey soil of low salinity but, particularly in the northern Sahel, Balanites aegyptiaca is also widely present on lighter, better-drained soil. Balanites aegyptiaca is characteristic of vegetation in which woody species are widely spaced, with full crown exposure. Associated woody species vary through the range but listings frequently include the families Caesalpiniaceae, Capparaceae, Combretaceae (especially Combretum) and Mimosaceae (especially Acacia). When present in abundance, the number of individuals more than 5 cm diameter at breast height may exceed 25 ha −1, representing 15% of woody individuals present. Attention is drawn to numerous relationships with animals (including Man and domestic livestock) and the significance of these in the conservation and management context. Practicable action in terms of provenance trials, which would lead to improved understanding of the potential of the species as a resource, is outlined and suggestions are made for positive management measures and planting initiatives.