Data from: The mesic savannas of the Bateke Plateau: carbon stocks and floristic composition

The Bateke Plateau in the Republic of Congo is one of the last frontiers
for ecology, with little known about its floristics and physiognomy.
Despite occupying 89,800 km2 and its importance for local livelihoods, its
ecology and ecosystem functions are poorly understood. Situated on
Kalahari sands, the Bateke has a complex evolutionary history, mainly
isolated from other savannas for much of its past, with currently
unresolved ecological implications. Here we assess the biomass and
floristic diversity of this savanna. We established four 25 ha permanent
sample plots at two savanna sites, inventoried all trees, and assessed
shrub, forb and grass species and biomass, and characterised the soils.
Total plant carbon stocks (aboveground and belowground) were only 6.5 ±
0.3 MgC/ha, despite precipitation of 1600 mm/yr. Over half the biomass was
grass, with the remainder divided between trees and shrubs. The carbon
stock of the system is mostly contained in the top layer of the soil (16.7
± 0.9 MgC/ha in 0-20 cm depth). We identified 49 plant species (4 trees,
13 shrubs, 4 sedges, 17 forbs and 11 grass species), with an average
species richness of 23 per plot. There is tree hyperdominance of
Hymenocardia acida (Phyllanthaceae), and a richer herbaceous species
composition dominated by Loudetia simplex and Hyparrhenia diplandra. The
low carbon stocks and tree biodiversity, compared to other African
savannas, is surprising considering the high rainfall. We speculate it is
due to low nutrient soils, high fire frequency and the effect of a
temporally variable and restricted connection to the main southern African
savanna complex.