Most of the park is situated in the central basin of democratic republic of Congo, although it is called the lower part, this actually consisted of steep mountains cut by deep valleys whose altitude varies from 600m to 1200m above sea level. Here the prevailing vegetation type is the equatorial rain forest, it is a typical tropical rain forest, and a great diversity of plant species is dominated by tall trees that branch only at the top from dense, ever green canopy 45 m above the ground. This canopy creates an atmosphere of half –shade and half-light that is barely sufficient for the growth of herbaceous plants and other understory species. These develop in the forest edge and its clearings, many species of big trees have buttress roots or in more humid places, still roots. The humidity in the forest is always high, The ground is often soaking wet and its humus layer is very thin because the conditions of high temperature and humidity are ideal for decomposing organisms. A leaf can be disgested within two months. In the mountainous parts of Kahuzi biega national park are the succession of the vegetation types from 900 to 3300m has been well studied. Six different primary vegetation types are distinguished, each one accompanied by its typical secondary form.