The south sector includes the watershed between the basin of the Luilaka to the north and east, Likoro to the west, and Lukenje to the south. Soils are a thin humus layer over Kalahari sands with several lateritic flushes. Rains are mostly downpours and on only 30 days in the year is precipitation less than 20mm. 24.5 C. Temperatures are stable with daily mean variations from 20 C at night to 30 C during the day. Cloud cover is often complete until 1000 hours, associated with fog and storms from midday to 1500 hours, but skies are often clear at night to 0400 hours.
Equatorial forest covers most of the area, varying in composition according to the geomorphology.
The principal forest types are swamp, riverine, and dry-land forests. Evergreen ombrophile forest is dominated by well-developed stands of Gilbertiodendron dewevrei . Semi-deciduous forest covers almost all areas between the rivers, most frequently comprising Staudtia stipitata , Polyalthia suavaeoleus , Scorodophloeus zenkeri , Anonidium mannii and Parinari glaberrimum . Pioneer or transitory communities are found along river banks, including Macaranga lancifolia and Harungana madagascariensis . Grassland vegetation, rather than savanna, occurs in the north sector, known locally as 'botoka-djoku' or elephant's bath.