Flora and vegetation
The flora of the Niokolo Koba is very rich. Of the roughly 2500 species of higher plants in Senegal the PNNK has about 1500 of them (Adam 1971; Schneider and Sambou 1982; Madsen et al. 1996) and in the Herbarium of the Cheikh Anta Diop University in Dakar 1 117 of them have been stored (Ba et al. 1997). The species recorded in the park belong to 120 families, of which 4 are the most numerously represented: Poaceae (13.6 %), Fabaceae (12.7 %), Cyperaceae (7.2 %) and Rubiaceae (5.5 %). Phytogeographically the PNNK can be broken up into a transitional zone of the Sudanese and Suda-no-Guinean savannahs (White 1983). The most extensive vegetation formation in the Niokolo Koba is grass and woody savanna, in which high stemmed grasses predominate such as Andropogon gayanus, Pennisetum pedicellatum, Cymbopogon giganteus, Diheteropogon amplectens, Schizachyrium sanguineum, and others with more or less thickly growing bushes and trees growing such as Bombax costatum, Burkea africana, Cochlospermum tinctorium, Cordyla pinnata, Crossopteryx febrifuga, Detarium microcarpum, Gardenia ternifolia, Lannea acida, Pterocarpus erinaceus, Sterculia setigera, Stereospermum kunthianum, Strychnos spinosa, Xerroderis stuhlmanii, Vitex madiensis, and interesting formations grow on the bowal – the ferrolateritic crust, which is almost without soil, therefore annual herbs and grasses predominantly grow here such as Lepturella aristata, Danthoniopsis tuberculata and Lepidagathis capituliformis. Along the rivers and temporary wadis gallery forests form with their special microclimate, in which copious amounts of species requiring dampness and deeper soil grow. Here we find evergreen plants and lianas such as Saba senegalensis, Nauclea latifolia, Combretum tomentosum, Strophantus sarmentosus. Some species grow to enormous heights of up to 30 m. Typical species are Anogeissus leiocarpus, Ceiba pentandra, Cola cordifolia, Khaya senegalensis, and others. The marshes in the flooded river valleys of the Gambia are only covered by a low herb and grass growth, with sporadic bushes. The reduced rainfall in recent years has led to the marshes drying up and Mimosa pigra bushes growing. This has become a serious problem as the marshes ensure grazing and water for the fauna, particularly in the peak of the dry period where water becomes the limiting factor in the animals’ survival.
In this time fires are a part of the PNNK’s management, and with a good reason.
But fire also has its darker impacts, the most serious of which is its impact on vegetation. The fire suppresses the natural regeneration of certain wood species Bombax costatum, Cordyla pinnata, Strychnos spinosa, Lannea acida, L. velutina and Terminalia macroptera, whilst Combretum glutinosum and Pterocarpus erinaceus are less influenced. The species composition of the savannah gradually changes in the pyrophytic species’ favour, which can be unsuitable for ensuring herbivores’ food. The most common families in the areas affected by fire are Combretaceae and Caesalpiniaceae, in areas with less frequent fires representatives of the family Rubiaceae (Mbow 2000, Mbow et al. 2003, Sonko 2000, Traoré 1997) can be found.