Alfred Ngomanda

Coupled Rock-Eval pyrolysis and spectrophotometry for lacustrine sedimentary dynamics: Application for West Central African rainforests (Kamalété and Nguène lakes, Gabon)

In recent years, Nguène Lake and Kamalété Lake (Gabon, West Central Africa) have been studied repeatedly, providing comprehensive reconstructions of environmental changes over the last millennia. Both lakes are in different geomorphological and environmental settings. They are therefore excellent sites to test new methodological approaches. Indeed, the sedimentary cores provide various facies, and the previous studies provide references for calibrating the results of new methods. In this methodological issue, the present study aims to evaluate the potential of spectrophotometric and Rock-Eval coupled analysis to describe the Holocene lake and marsh deposits from tropical moist forests. This assessment is carried out on samples taken from two well-documented reference cores. The spectrophotometric analysis provides reproducible colour measurements, which inform about the nature of the main colour-bearing constituents. Coupled with Rock-Eval pyrolysis, this technique can be used to describe lithological changes and identify the probable source of sedimentary organic matter. In the studied cases, this approach identified the facies dominated by detrital terrigenous inputs (‘iron bearing’ signature and high OI values) and those associated with a more abundant primary production (‘chlorophyll’ signature, low OI and high HI), providing a distinction between palustrine and lacustrine dynamics. However, although the facies are comparable, sedimentary dynamics and sediment sources may vary depending on geomorphological and climatic contexts.

Opportunity costs of carbon sequestration in a forest concession in central Africa

BackgroundA large proportion of the tropical rain forests of central Africa undergo periodic selective logging for timber harvesting. The REDD+ mechanism could promote less intensive logging if revenue from the additional carbon stored in the forest compensates financially for the reduced timber yield.ResultsCarbon stocks, and timber yields, and their associated values, were predicted at the scale of a forest concession in Gabon over a project scenario of 40 yr with reduced logging intensity. Considering that the timber contribution margin (i.e. the selling price of timber minus its production costs) varies between 10 and US

Seasonality change and the third millennium BP rainforest crisis in southern Cameroon (Central Africa).

40 m −3, the minimum price of carbon that enables carbon revenues to compensate forgone timber benefits ranges between US

First farmers in the Central African rainforest: A view from southern Cameroon

4.4 and US

Site-specific versus pantropical allometric equations: Which option to estimate the biomass of a moist central African forest?

25.9/tCO 2 depending on the management scenario implemented.ConclusionsWhere multiple suppliers of emission reductions compete in a REDD+ carbon market, tropical timber companies are likely to change their management practices only if very favourable conditions are met, namely if the timber contribution margin remains low enough and if alternative management practices and associated incentives are appropriately chosen.