Journal of Tropical Ecology

Research Article

Demography and biomass change in monodominant and mixed old-growth forest of the Congo

Jean-Remy Makanaa1, Corneille N. Ewangoa2, Sean M. McMahona3, Sean C. Thomasa4, Terese B. Harta5 and Richard Condita6 c1

a1 Wildlife Conservation Society – DRC Program, Kinshasa, DR Congo

a2 Centre de Formation et de Recherche en Conservation Forestiere (CEFRECOF), Wildlife Conservation Society, Kinshasa, DR Congo

a3 Smithsonian Tropical Research Institute & Smithsonian Environmental Research Center, Edgewater, Maryland, USA

a4 Faculty of Forestry, University of Toronto, Toronto, Canada

a5 Project TL2, Kinshasa, DR Congo

a6 Center for Tropical Forest Science, Smithsonian Tropical Research Institute, Panama MRC 0580-12, Unit 9100 Box 0948, DPO AA 34002 USA


Mbau forest covers much of the Congo, and shifts in its composition could have a large impact on the African tropics. The Ituri forest in east Congo is near a boundary between the monodominant mbau type and non-mbau mixed forest, and two 20-ha censuses of trees ≥ 1 cm diameter were carried out over 12 y to monitor forest change. Based on published diameter allometry, mbau forest had 535 Mg ha−1 biomass above ground and gained 1.1 Mg ha−1 y−1. Mixed forest had 399 Mg ha−1 and gained 3 Mg ha−1 y−1. The mbau tree (Gilbertiodendron dewevrei) increased its share of biomass from 4.1% to 4.4% in mixed forest; other common species also increased. Sapling density declined at both sites, likely because increased biomass meant shadier understorey, but the mbau tree increased in sapling density, suggesting it will become more important in the future. Tree mortality and growth rates were low relative to other tropical forests, especially in the mbau plots. Shifting toward G. dewevrei would represent a large gain in carbon in the mixed forest, but mbau is presently more important as a high-carbon stock: biomass lost during forest harvest could not recuperate for centuries due to slow community dynamics.

(Accepted May 23 2011)

(Online publication August 02 2011)


c1 Corresponding author. Email: