The Ecology of African Floodplain Forests in Semi-Arid and Arid Zones: A Review

Abstract

Publications describing forests on floodplains in semi-arid and arid parts of Africa are reviewed in order to identify common features in their form and functioning. These forests are little studied but valuable natural resources. Their composition and extent appear to be greatly influenced by both natural and human factors. The distribution of vegeta- tion within them is related to frequency of flooding, and their overall extent to the depth of the water table. On most floodplains, mature trees can only exist on the highest parts, whilst grasslands dominate in the more frequently flooded areas. On floodplains in areas of very low rainfall, the forest vegetation is more dependent on groundwater and the outer forest edge tends to be more abrupt than in wetter areas. These general patterns are complicated by the firing of floodplain grasslands by pastoralists to improve grazing for their stock and by browsing by wild animals. A study of some of these factors in the Tana River floodplain forests of Kenya is then described, and the results discussed in the context of general trends apparent from the literature.