Exploring charcoal as a natural archive for palaeofire and vegetation history of the Mayumbe, Democratic Republic of the Congo

Direct evidence for Central African vegetation history is primarily based on pollen analysis. In addition, charcoal analysis has proven successful for palaeobotanical reconstructions in moderate and arid regions. Yet in the tropics this discipline meets fundamental obstacles inherent in species-richness and the lack of a systematic identification procedure. Therefore, the first part of this PhD presents a transparent identification procedure for Central African charcoal, based on large databases and well-defined wood-anatomical characters. The procedure uses complementary imaging techniques and a methodology for the evaluation of identification reliability. The validity of the protocol has been proven by the mutual consistency of charcoal identification results and compatibility with vegetation history based on pollen research. In the second part of this PhD the charcoal identification and evaluation methodologies are applied on charcoal fragments found in 7 soil profiles excavated in the southern Mayumbe forest (Bas-Congo, DRCongo). Each soil profile yielded one or more charcoal assemblages, each archiving a palaeofire. Radiocarbon dating showed that all recorded palaeofires occurred during or shortly after one out of three well-known dry climate anomalies: the 8.2 ka BP event, the third millennium BP rainforest crisis (3000-2000 cal yr BP) and the Medieval Climate Anomaly (MCA, 1000 - 700 cal yr BP). During and after these periods the rainforests were very sensitive to drought and fire, primarily around open patches during the dry season. Charcoal identifications show that forests close to the Central African rainforest boundary were locally replaced by savanna and open forest types due to drought, whereas it remained relatively intact deeper in the heart of the rainforest. Moreover, forest regeneration during recovery periods was hampered by recurring forest fires, making it a very slow process. However, artefacts associated with some of the charcoal assemblages show that forest fragmentation was not a direct result of climatic drought only, but it was also reinforced by human disturbance, which started around the third millennium BP but probably became important only during the last millennium

Charcoal from the Congo Basin : palaeo-botanical evidence for climate change?

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Asynchronous carbon sink saturation in African and Amazonian tropical forests

Structurally intact tropical forests sequestered about half of the global terrestrial carbon uptake over the 1990s and early 2000s, removing about 15 percent of 1–3 anthropogenic carbon dioxide emissions. Climate-driven vegetation models 4,5 typically predict that this tropical forest ‘carbon sink’ will continue for decades . Here we assess trends in the carbon sink using 244 structurally intact African tropical forests spanning 11 countries, compare them with 321 published plots from Amazonia and investigate the underlying drivers of the trends. The carbon sink in live aboveground biomass in intact African tropical forests has been stable for the three decades to 2015, at 0.66 tonnes of carbon per hectare per year (95 percent confidence 6 interval0.53–0.79), in contrast to the long-term decline in Amazonian forests. Therefore the carbon sink responses of Earth’s two largest expanses of tropical forest have diverged. The difference is largely driven by carbon losses from tree mortality, with no detectable multi-decadal trend in Africa and a long-term increase in Amazonia. Both continents show increasing tree growth, consistent with the expected 7–9 net effect of rising atmospheric carbon dioxide and air temperature. Despite the past stability of the African carbon sink, our most intensively monitored plots suggest a post-2010 increase in carbon losses, delayed compared to Amazonia, indicating asynchronous carbon sink saturation on the two continents. A statistical model including carbon dioxide, temperature, drought, and forest dynamics accounts for the observed trends and indicates a long-term future decline in the African sink, whereas the Amazonian sink continues to weaken rapidly. Overall, the uptake of carbon into Earth’s intact tropical forests peaked in the 1990s. Given that the global terrestrial carbon sink is increasing in size, independent observations indicating greater recent carbon uptake into the Northern Hemisphere landmass10 reinforce our conclusion that the intact tropical forest carbon sink has already peaked. This saturation and ongoing decline of the tropical forest carbon sink has consequences for policies intended to stabilize Earth’s climate

The earliest iron-producing communities in the Lower Congo region of Central Africa : new insights from the Bu, Kindu and Mantsetsi sites

In 2015 the KongoKing research project team excavated the Bu, Kindu and Mantsetsi sites situated in the Kongo-Central Province of the Democratic Republic of Congo (DRC). All are part of the Kay Ladio Group. This is the first detailed publication on this cultural group, to which no contemporary ones can currently be linked, either from the Atlantic coast of Congo-Brazzaville or from along the Congo River and its tributaries upstream of Kinshasa. Dated to between cal. AD 30 and 475, these settlements mark the presence of what are so far the oldest known iron-producing communities south of the Central African equatorial forest. Evidence for metallurgy is associated with remants of polished stone axes, which were perhaps being used for ritual purposes by this point in time. The charcoal remains found at the sites indicate a savanna environment that was more wooded in Kindu and Mantsetsi than in Bu

Management of African economic trees for new research, the review of Entandrophragma genus (Meliaceae)

Entandrophragma genus includes exclusively African species (10 to 12), five of which are on the IUCN Red List. Characterized by a taxonomic evolution that has resulted in an important synonymy of species names (36-3 7) and insufficient ecological knowledge, it is the richest in valuable species exploited as timber in Africa. This important exploitation is likely to compromise their durability in the absence of sustainable management. Our study is mainly based on scientific data (e.g., publications), economic data (production and export statistics) and legal data (laws and regulations); on management plans and inventory reports. The heavy industrial exploitation as artisanal does not always proceed in the respect of a validated management plan, nor of the duration of the rotations which would make it possible to reach a rate of reconstitution likely to perpetuate the resource which these species represent. Their sustainable management requires the development and respect of management measures to make their exploitation sustainable in the long term. This exploitation must be based on an adequate management of natural stands and on reforestation as well as on conservation measures. The research to be developed must focus on their growth rate (eg, in the face of climate change), the analysis of stable rings and isotopes, the evaluation of their stocks (production, biomass, carbon), their spatial distribution and molecular phylogeny, the improvement of their natural regeneration, their reproduction, phenology and anatomy, as well as the reinforcement of other relevant lines of research to guarantee the durability of these forest species