Odzala National Park is a national park in the Cuvette-Ouest Region of the Republic of the Congo. Founded in 1935, the park now covers 13,600 sq km. It is known as "one of the most important strongholds for forest elephant and western gorilla conservation remaining in Central Africa".
As of 1996, he entire area of the reserve is found within the catchment area of the Mambili River, which drains the area towards the south. The region is quite varied due to the juxtaposition of several habitat types, including savanna, forest and rivers. The site is astride the savanna-forest boundary of North-Central Congo, allowing for a high biodiversity of flora and fauna, with species from forest, savanna and riverine forest. The area is densely forested in the northwest; towards the south and east the forest becomes more open with an understorey of Marantaceae carpeting the ground. In the south of the region an extensive forest-savanna mosaic is found, including gallery forests and dry and swamp savanna.
Two broad forest types are present: forests of hydromorphic soils, and forests of terra firma. The forests of terra firma are the most extensive, and may be further subdivided into closed canopy forests and open forests. The forests of terra firma are generally quite heterogeneous in terms of species, although patches of Lophira alata-dominated forest exist. In Odzala, both forest types of terra firma are classed as Marantaceae forest: that is, the understorey is an often impenetrable mass of lianescent or erect giant herbs in the family Marantaceae. This forms a thick carpet, up to 3-4m deep, giving the impression of a giant 'lawn' through which tree seedlings must grow to reach the light.
In the open Marantaceae forests, the middle-sized trees are much less common than in a closed-canopy forest, sometimes giving one the impression of being an ant in a lawn, with trees so far apart that they are like a London park!. Data from transects in Odzala show that both tree density and basal area of Marantaceae forest is much lower per hectare than "classic" tropical humid forests of Central Africa. Marantaceae forest is thought to be a stage in the succession of the forest recolonization of the savanna. Several other forest types are recognizable at Odzala as stages in this succession.
The marsh forests are quite extensive, especially along the floodplain of the Mambili. They are generally relatively short, dense forests, often dominated by Mitragyna ciliata, and do not have the thick carpet of Marantaceae found on dry land. Beside the Mambili, patches of monodominant or bi-dominant forest occur, of Gilbertiodendron dewevreii and/or Guibourtia demeusei. Smaller patches of low diversity forest occur on marshy soils here and there, the most frequent of which are Raphia swamp, Xylopia forest, Phoenix reclinata patches and Pandanus swamp.