The mangrove swamps of Kaneba, lower Gambia river basin. I. Descriptive notes on the climate, the mangrove swamps and the physical composition of their soils.
The swamps consist mainly of areas under Rhizo-phora racemosa and Avicennia germinans mangroves, Sesuvium portulacastrum lawns, and barren mud flats. The evolution and zonation of the complex are related to the low single-peak rainfall and long drying season. Both alluvial material in which particle size varied with depth, and layers of colluvial sand occurred. The textural horizons reflected influences of vegetation, topography and flow of water courses. Contents of organic C (5-10%) and fibrous roots (11-26%) were high under Rhizophora; they were also high at some depths under Avicennia and in the mud flats, suggesting previous colonization by Rhizophora. Rhizophora soils, which were flooded daily, were strongly gleyed throughout the profile; in other profiles where the effects of tides and water-table level varied through the year, mottled horizons occurred. As alluvial deposition, mechanical sieving of water-borne material, and deposition of colluvial and wind-borne material have raised the level of the land, there has been a succession of vegetation from Rhizophora to Avicennia, to Sesuvium, and finally to Paspalum and other grasses not adapted to saline conditions.