References of "Doucet, Jean-Louis"
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See detailExplorer la banque de graines du sol pour mieux comprendre la dynamique de régénération des forêts tropicales africaines (synthèse bibliographique)
Douh, Chauvelin ULg; Daïnou, Kasso ULg; Loumeto, Jean Joël et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (in press), 18(4),

La banque de graines du sol des forêts denses humides africaines a été très peu étudiée, alors qu’elle pourrait jouer un rôle déterminant dans les cycles sylvigénétiques naturels. Elle pourrait également ... [more ▼]

La banque de graines du sol des forêts denses humides africaines a été très peu étudiée, alors qu’elle pourrait jouer un rôle déterminant dans les cycles sylvigénétiques naturels. Elle pourrait également être avantageusement utilisée dans les programmes de restauration, à l’instar de ce qui se fait sur d’autres continents. La présente synthèse bibliographique fait le point sur les connaissances actuelles relatives à la banque de graines du sol, en mettant l’accent sur le continent africain. Elle montre qu’une meilleure caractérisation de la banque de graines du sol des différentes communautés végétales constituerait une contribution notable pour la gestion durable des forêts tropicales d’Afrique. [less ▲]

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See detailThe need for site-specific height-diameter allometry of Central African moist forests
Loubota Panzou, Grâce Jopaul ULg; Doucet, Jean-Louis ULg; Fayolle, Adeline ULg

Conference (2015, March 21)

L’utilisation de l’allométrie hauteur-diamètre globale ou régionale en milieu tropical pourrait avoir des conséquences importantes dans les estimations de biomasse et des stocks de carbone. L’objectif de ... [more ▼]

L’utilisation de l’allométrie hauteur-diamètre globale ou régionale en milieu tropical pourrait avoir des conséquences importantes dans les estimations de biomasse et des stocks de carbone. L’objectif de ce travail est d’identifier les variations de l’allométrie hauteur-diamètre au sein de deux types de forêts (forêt sempervirente et forêt semi-décidue) au sud du Cameroun et d’examiner leurs conséquences sur les estimations de biomasse. Le diamètre et la hauteur ont été mesurés sur un total de 521 arbres appartenant à 15 espèces et couvrant une gamme de diamètre de 10 à 240 cm. Une calibration des mesures non destructives et destructives de la hauteur a été réalisée sur 60 arbres. Dix modèles allométriques ont été ajustés sur ces données. Le meilleur modèle a été sélectionné avec Akaike Information Criterion (AIC). L’allométrie hauteur-diamètre au niveau des sites et entre les espèces a montré une tendance asymptotique (Modèle de Michaelis-Menten). Pour un même diamètre, les arbres étaient plus hauts dans les forêts semi-décidues que dans les forêts sempervirentes. Les différences de biomasse entre les deux types de forêts sont dues par les variations de l’allométrie hauteur-diamètre. Les variations de l’allométrie hauteur-diamètre sont donc d’une extrême importance dans les estimations de biomasse et des stocks de carbone des forêts denses humides tropicales d’Afrique centrale. [less ▲]

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See detailApproche agroforestière. Synthèse des travaux menés par le projet DACEFI2 en agroforesterie. Document de capitalisation.
Boldrini, Sylvie; Meunier, Quentin; Boukouendji, Basile et al

E-print/Working paper (2015)

Le projet DACEFI-2 a eu pour mission première la promotion de la foresterie communautaire comme outil de développement des communautés rurales. L’approche au Gabon en matière de gestion des terroirs ... [more ▼]

Le projet DACEFI-2 a eu pour mission première la promotion de la foresterie communautaire comme outil de développement des communautés rurales. L’approche au Gabon en matière de gestion des terroirs villageois s’est voulue plus embrassante, promouvant en sus de l’exploitation forestière des activités comme l’agriculture, le maraîchage, la collecte des produits forestiers non ligneux ou encore l’agroforesterie. L’agroforesterie est une thématique qui converge parfaitement avec la gestion raisonnée de la forêt, et idéalement avec les modes d’interaction préexistants des villageois avec celle-ci. Concilier dans un même espace la culture de plantes vivrières et l’accès à des arbres à fort intérêt socio-économique apporte une plus-value notoire aux parcelles cultivées. L’optimisation des techniques culturales permet une meilleure productivité et une incitation à la sédentarisation des cultures, élément important à considérer compte tenu des difficultés d’entretien des parcelles éloignées du village (notamment liées aux dégâts causés par les animaux). Ce recueil compile les travaux réalisés en agroforesterie par les équipes du projet DACEFI-2. Il rappelle la stratégie d’intervention et les différentes activités menées, de la sensibilisation auprès des plus jeunes à la promotion de certains produits forestiers non ligneux à potentiel économique avéré. La promotion de l’arbre, de la récolte de la graine jusqu’à sa plantation en passant par sa mise en pépinière aura également animé toute l’équipe durant ces années d’exercice, afin de faire un peu plus valoir ses multiples intérêts et susciter les efforts de gestion, de conservation et de reboisement. [less ▲]

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See detailSite-specific height-diameter allometry of Central African moist forests
Loubota Panzou, Grâce Jopaul ULg; Doucet, Jean-Louis ULg; Fayolle, Adeline ULg

Poster (2015, February 04)

In this study we aimed to identify the variation in height-diameter allometry between forest types and among species in Central African moist forests. We also examined the consequences on biomass ... [more ▼]

In this study we aimed to identify the variation in height-diameter allometry between forest types and among species in Central African moist forests. We also examined the consequences on biomass estimation. Two forest sites in southern Cameroon with contrasting levels of deciduousness. Height and diameter were measured for a total of 521 trees belonging to 12 timber species over a large range of diameter, 10-240 cm for the Ma’an site and 11-182 cm for the Mindourou site. Non-destructive height measurements were calibrated with destructive measurements for a total of 60 trees, 30 in each site. Commercial forest inventory data (n=7253 0.5ha plots) were gathered for the Ma’an (n=34 samples and 2101 plots) and Mindourou (n=117 samples and 5152 plots) sites. A total of ten allometric models (including asymptotic and non-asymptotic models) were fitted to the height-diameter data at species (n=12) and site (n=2) level. Biomass estimates were computed based on forest inventory data and general allometric models using both site-specific and published height-diameter equations. Given the strong correlation between the non-destructive and destructive height measurements we had confidence in using the non-destructive height measurements to establish site- and species-specific height-diameter allometric equations. The height measurements performed over a wide range of diameters, 10-240 cm, tended to support an asymptotic shape (and most often the Michaelis Menten model) for the height-diameter allometry either at species and site level. We identified a significant difference in height-diameter allometry between the two study sites. For a given diameter, trees tended to be taller in the more semi-deciduous Mindourou site than in the more evergreen Ma’an site, with a maximum height of 39.5 and 46.5 m, respectively. The two sites significantly differed in stand structure and biomass. This difference is due to the variation in height-diameter allometry. Height-diameter allometry strongly varies between sites and site-specific height-diameter allometric equations should be developed to further improve the estimation of biomass and carbon stock contained in tropical forests. [less ▲]

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See detailNew data on the recent history of the littoral forests of southern Cameroon: an insight into the role of historical human disturbances on the current forest composition
Biwolé, Achille ULg; Morin-Rivat, Julie ULg; Fayolle, Adeline ULg et al

in Plant Ecology and Evolution (2015), 148(1), 19-28

Background and aims – Prior to European colonisation of Central Africa, human populations were dispersed through the forests, where they practiced slash-and-burn cultivation. From the 19th century they ... [more ▼]

Background and aims – Prior to European colonisation of Central Africa, human populations were dispersed through the forests, where they practiced slash-and-burn cultivation. From the 19th century they were progressively concentrated in villages along roads, leaving large areas of forest derelict. In south-western Cameroon, and elsewhere in Central Africa, forest canopy is dominated by long-lived lightdemanding tree species, suggesting a possible role of human disturbance. The aim of this study was to bring new insights into the possible effect of historical human disturbances in terms of timing and spatial extent on the current forest composition. Location – Wet evergreen littoral forest in south-western Cameroon. Methods and key results – A combined vegetation sampling and archaeobotanical survey were conducted. Potsherds, oil-palm endocarps, and charcoal were found throughout the study area, suggesting generalised human occupation and anthropogenic fire. Human occupancy occurred in two periods: between 2200 and 1500 BP, and, more recently, beginning three centuries ago. High frequency of fire and the presence of Elaeis guineensis both dated recently (between 260 and 145 BP) suggest slash-and-burn shifting cultivation practices. These human-induced disturbances may coincide with the age of the current emergent lightdemanding species, the age of which can be estimated around 200 years, or with the phases of drying climate recorded in the Central African forest in the early 18th century. Conclusions – These results support the idea that historical human disturbances are one of the major factors that shaped the current forest composition in Central Africa. [less ▲]

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See detailLe genre Guibourtia Benn., un taxon à haute valeur commerciale et sociétale (synthèse bibliographique)
Tosso, Dji-ndé Félicien ULg; Daïnou, Kasso ULg; Hardy, J. Olivier et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2015), 19(1),

Known as a genus of great socio-cultural and economical importance, Guibourtia Benn. includes morphologically very similar multipurpose sister species, found in various habitats with different climate and ... [more ▼]

Known as a genus of great socio-cultural and economical importance, Guibourtia Benn. includes morphologically very similar multipurpose sister species, found in various habitats with different climate and soil conditions. In many places, Guibourtia is subject to local overexploitation by forest companies and local communities. As the population density of Guibourtia species is generally very low, it may be necessary to conduct scientific investigations that will provide valuable information for the management of the populations concerned. This paper is based on an extensive literature review and summarizes the available information on the genus Guibourtia, in terms of botany, ecology, genetics, forestry and ethnobotany. Our review provided evidence that, to date, ecological and silvicultural knowledge regarding Guibourtia species is lacking and that it is very difficult to morphologically differentiate very similar sister species. In addition, we provide a new determination key for the genus Guibourtia. Based on the available information, it is difficult to assess the conservation status of these taxa. Further investigations are needed to suggest appropriate management strategies for Guibourtia. Moreover, species diversity within this genus and its distribution in various tropical biomes make it an excellent biological model for understanding the historical, biological and environmental mechanisms that explain the diversity of tropical moist forests. [less ▲]

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See detailLe genre Erythrophleum (Fabaceae) en Afrique, un modèle pour l’étude des mécanismes de différenciation de niches climatiques
Gorel, Anaïs ULg; Duminil, Jérôme; Doucet, Jean-Louis ULg et al

Conference (2014, December 16)

Comprendre l’origine des patrons de diversité est un défi en écologie des communautés et en écologie évolutive, notamment dans le contexte du futur changement climatique. Ce poster aura deux objectifs : i ... [more ▼]

Comprendre l’origine des patrons de diversité est un défi en écologie des communautés et en écologie évolutive, notamment dans le contexte du futur changement climatique. Ce poster aura deux objectifs : i) présenter pourquoi le genre Erythrophleum en Afrique est un modèle d’étude idéal à la compréhension des mécanismes de différenciation de niche et de spéciation au sein d’une lignée d’arbre en région tropicale; ii) mettre en lumière les démarches statistiques et expérimentales permettant de valider et de comprendre ces mécanismes. Le genre Erythrophleum, largement distribué en Afrique, est représenté par quatre espèces d’arbre : E. ivorense, E. suaveolens, E. africanum et E. lasianthum. Ces espèces morphologiquement très proches, présentent des aires de distribution géographiques et climatiques adjacentes. Elles sont distribuées de façon parapatrique sur un gradient pluviométrique, du plus humide pour E. ivorense ou plus sec pour E. lasianthum. Ce mode de distribution apparent, combiné à des données issues d’études phylogénétiques, suggère un rôle majeur des gradients climatiques comme pilotes des différenciations spécifiques du genre et pourrait donc confirmer l’hypothèse du gradient écologique (« The ecological gradient hypothesis » suppose que des gradients environnementaux peuvent induire des spéciations parapatriques sans que les populations ne soient isolées géographiquement. Néanmoins, des études sur les niches climatiques et leurs degrés de conservatisme sont indispensables pour valider cette hypothèse. Aujourd’hui, ces études sont rendues plus aisées grâce au développement de nouvelles techniques de modélisation des niches environnementales (Species Distribution Model ou SDM) et de tests statistiques de quantification du conservatisme/divergence de niche (voire Warren et al., 2008). En complément de la modélisation des niches observées (c.à.d. niches réalisées selon la définition de Hutchison (1957)), il est intéressant de comprendre les stratégies fonctionnelles sous-jacentes aux différenciations de niche. Les différenciations de niche au sein des espèces du genre sont probablement issues d’une distinction de leurs stratégies d’utilisation des ressources (lumière/eau) et de leurs différents positionnements au sein du slow-fast continuum (sensu Reich, 2014). Cette hypothèse peut être testée par la mise en place d’expériences en milieu contrôlé mesurant les réponses des individus à des stress environnementaux. [less ▲]

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See detailLes progrès de la foresterie sociale en Afrique centrale
Vermeulen, Cédric ULg; Doucet, Jean-Louis ULg

Conference given outside the academic context (2014)

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See detailIntegrating phylogenetic and environmental niche models to explore speciation mechanisms in the Erythrophleum genus in tropical Africa
Gorel, Anaïs ULg; Fayolle, Adeline ULg; Doucet, Jean-Louis ULg et al

Conference (2014, December 10)

In the context of global climate change, it is of primary importance to understand the species response to climate (habitat tracking or adaptation). In this study we investigated the evolutionary history ... [more ▼]

In the context of global climate change, it is of primary importance to understand the species response to climate (habitat tracking or adaptation). In this study we investigated the evolutionary history of the climatic niche between and within closely related tropical tree species of the Erythrophleum genus (Fabaceae, Caesalpinioideae): E. ivorense, E. suaveolens and E. africanum. Two major hypotheses, the refuge theory and the ecological gradient hypothesis, have been developed to explain the current distribution of tree clades across tropical Africa. To identify the speciation mechanisms, we used a combination of geographic data and environmental factors to quantify the degree of niche conservatism (or divergence). We used two sets of distribution data for the purpose of this study. Species distribution data for the whole of tropical Africa were gathered from herbarium records. Distribution data of the two sister species E. ivorense and E. suaveolens assigned to genetic cluster were available for the lowland tropical forests of western and central Africa. Using a Species Distribution Model (SDM) approach based on MaxEnt algorithm, we tested for the environmental differences (BIOCLIM data) between species and genetic clusters within species. We developed SDMs for each of the three Erythrophleum species (over the whole range) and for each of the five genetic clusters. We quantified the niche overlap using new niche similarity metrics. At species level, the climatic niches differed significantly and overlapped only sligthly, suggesting a parapatric speciation along a climatic gradient. Within the two sister species, the niche of the parapatric central African clusters strongly overlapped, suggesting a secondary contact following the recolonization from different forest refugia. The west African cluster however showed contrasted climatic niches possibly due to either recent (< 100 yrs) climate change in west Africa, or ongoing differentiation on the dry part of the climatic gradient. [less ▲]

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See detailSoil charcoal to assess the impacts of past human disturbances on tropical forests
Vleminckx, Jason; Morin-Rivat, Julie ULg; Biwolé, Achille et al

in PLoS ONE (2014)

The canopy of many central African forests is dominated by light-demanding tree species that do not regenerate well under themselves. The prevalence of these species might result from ancient slash-and ... [more ▼]

The canopy of many central African forests is dominated by light-demanding tree species that do not regenerate well under themselves. The prevalence of these species might result from ancient slash-and-burn agricultural activities that created large openings, while a decline of these activities since the colonial period could explain their deficit of regeneration. To verify this hypothesis, we compared soil charcoal abundance, used as a proxy for past slash-and-burn agriculture, and tree species composition assessed on 208 rainforest 0.2 ha plots located in three areas from Southern Cameroon. Species were classified in regeneration guilds (pioneer, non-pioneer light-demanding, shade-bearer) and characterized by their woodspecific gravity, assumed to reflect light requirement. We tested the correlation between soil charcoal abundance and: (i) the relative abundance of each guild, (ii) each species and family abundance and (iii) mean wood-specific gravity. Charcoal was found in 83% of the plots, indicating frequent past forest fires. Radiocarbon dating revealed two periods of fires: ‘‘recent’’ charcoal were on average 300 years old (up to 860 BP, n = 16) and occurred in the uppermost 20 cm soil layer, while ‘‘ancient’’ charcoal were on average 1900 years old (range: 1500 to 2800 BP, n = 43, excluding one sample dated 9400 BP), and found in all soil layers. While we expected a positive correlation between the relative abundance of light demanding species and charcoal abundance in the upper soil layer, overall there was no evidence that the current heterogeneity in tree species composition can be explained by charcoal abundance in any soil layer. The absence of signal supporting our hypothesis might result from (i) a relatively uniform impact of past slash-and-burn activities, (ii) pedoturbation processes bringing ancient charcoal to the upper soil layer, blurring the signal of centuries-old Human disturbances, or (iii) the prevalence of other environmental factors on species composition. [less ▲]

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See detailImportance des modèles de distribution de niche potentielle dans la gestion des espèces tropicales exploitées: cas des taxons du genre Guibourtia Benn
Tosso, Dji-ndé Félicien ULg; Daïnou, Kasso ULg; Hambuckers, Alain ULg et al

Poster (2014, September 24)

De la famille des (Fabaceae / Caesalpinioideae) et composé de 13 espèces en Afrique, le genre Guibourtia comporte des taxons à forte valeur culturelle et à forte valeur commerciale. Aujourd'hui, la ... [more ▼]

De la famille des (Fabaceae / Caesalpinioideae) et composé de 13 espèces en Afrique, le genre Guibourtia comporte des taxons à forte valeur culturelle et à forte valeur commerciale. Aujourd'hui, la pression de l'exploitation combinée aux faibles densités de ce genre, fait a priori peser d’importantes menaces sur certaines de ses populations. Un projet de recherche a donc été initié afin de mieux comprendre la structure et la diversité génétique des populations de Guibourtia, en lien avec l'exploitation forestière et les patrons de reproduction spécifiques. Un premier volet de la recherche a consisté à identifier les déterminants climatiques expliquant la distribution des espèces. Nous avons combinée des modèles statiques (Maxent et régression logistique) avec des données du modèle climatique global CNRM CM5, et sur la base de l'occurrence de ces taxons entre 1950 et 2000. Il en ressort que les espèces du genre Guibourtia sont sensibles aux facteurs précipitation (69,2 %) et amplitude thermique (74,3 %). Dans un second temps, il sera utilisé les modèles climatiques des ères géologiques passées afin d'inférer la distribution de l'espèce au cours du Quaternaire, et de faire le lien avec des analyses phylogénétiques et phylogéographiques. Il sera également possible d'évaluer la distribution future de l'espèce tenant compte des modèles d'évolution du climat. Enfin, le projet de recherche s'attèlera particulièrement aux relations phylogénétiques entre espèces morphologiquement similaires en sympatrie ou parapatrie, en caractérisant en détail les flux de gènes entre individus de ces taxons proches, ainsi que leur degré de similarité physiologique. Les résultats de l’étude in fine contribueront à proposer des stratégies de conservation et de gestion durable dans le contexte de l’exploitation forestière d’Afrique centrale et du changement climatique en cours. [less ▲]

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See detailStand structure and species co-occurence in mixed and monodominant Central African tropical forests
Djuikouo, Marie Noël K.; Peh, Kelvin S.H.; Nguembou et al

in Journal of Tropical Ecology (2014), 30(5), 447-455

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See detailSeed dispersal by western lowland gorillas: what about gut passage effect?
Haurez, Barbara ULg; Petre, Charles-Albert ULg; Doucet, Jean-Louis ULg

Conference (2014, July 21)

Animal-mediated seed dispersal is an essential ecological process in the tropics. Among African primates, the critically endangered western lowland gorilla (WLG) seems to fulfill many characteristics of ... [more ▼]

Animal-mediated seed dispersal is an essential ecological process in the tropics. Among African primates, the critically endangered western lowland gorilla (WLG) seems to fulfill many characteristics of an effective seed disperser. WLG preferentially disperses species of various seed-size into open canopy habitats suitable for seedling growth. However, few studies have addressed the effects of the passage through the digestive tract on germination. Thus, the effectiveness of WLG in ecological processes governing forest dynamics and regeneration is still poorly known. Seed dispersal by WLG was studied in Central Gabon and Southeast Cameroon. Dispersed seed were identified from fresh fecal samples. Comparative germination trials based on 5 treatments (seeds from fresh fruits, seeds from fresh fruits surrounded by pulp, seeds from fresh fruits with fecal matrix, seeds from feces and seeds from feces with fecal matrix) were realized for 13 species. We recorded germination success for all species and germination delay for 6 species. Our results suggest a neutral gut passage effect for 54% and positive effect for 40% of tested species. Germination success enhancement was linked to another factor than pulp suppression. For two species, pulp suppression enhanced germination success, but not gut passage. The presence of pulp or fecal matrix surrounding the seed seemed to longer germination delay, while gut passage would not fasten germination. Globally, we conclude that WLG dispersed seeds are not damaged by gut passage. Consequently, WLG is thought to provide effective ecological services that could be essential to the maintenance and the recovery of forest ecosystems. [less ▲]

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See detailWestern lowland gorilla in a logging concession: comparison of density and nesting behavior before and after logging
Haurez, Barbara ULg; Petre, Charles-Albert ULg; Doucet, Jean-Louis ULg

Conference (2014, May 22)

Timber exploitation is rapidly expanding throughout the Congo Basin. In Gabon, timber industry is currently the second working sector and logging concessions cover 45% of the country forest area, largely ... [more ▼]

Timber exploitation is rapidly expanding throughout the Congo Basin. In Gabon, timber industry is currently the second working sector and logging concessions cover 45% of the country forest area, largely overlapping with the range of western lowland gorilla (Gorilla gorilla gorilla WLG). Logging may negatively impact gorilla because of an increase in hunting pressure linked to human concentration and easier access to forest. On the other hand, WLG might benefit from forest opening and the associated growth in Terrestrial Herbaceous Vegetation, following timber felling and roads/trails implementation. In the present study, gorilla density and nesting behavior were studied in a 617,000-ha logging concession located in Central Gabon. A Standing Crop Nest Count census was realized 25 years after the first timber harvesting cycle, consisting in the assessment of the potentiality of logged forest to hold viable WLG populations. A second census was undertaken four to six months after the second logging wave. Comparing nesting behavior and estimated gorilla density between the two census allows to highlight the short-term effects of logging on gorilla populations. A relatively high WLG density was observed during the first census (2.1 weaned gorillas/km²). This figure dropped down to 1.0 weaned gorillas/km² after the second felling cycle. Both density values fall within the range of documented WLG densities documented at other sites. Gorillas consistently nested preferentially in open terra firme forest and built the majority of their nests using herbs of the Marantaceae and Zingiberaceae families. Both these observations underline the importance of Terrestrial Herbaceous Vegetation for nesting. The results of this study suggest that timber exploitation and WLG conservation are not mutually exclusive. The initial high density might traduce an effective anti-poaching strategy for now. The decline in gorilla density observed directly in the second census is probably linked with the avoidance of the disturbance of logging operations. Monitoring the evolution of WLG density would be important in order to control if the figure will rise over time to reach its initial value, but also to assess if a positive effect of Terrestrial Herbaceous Vegetation growth will be observed. [less ▲]

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See detailDynamique d’une espèce ligneuse héliophile longévive dans un monde changeant le cas de Pericopsis elata (Harms) Meeuwen (Fabaceae) au sud-est du Cameroun
Bourland, Nils ULg; Doucet, Jean-Louis ULg

Scientific conference (2014, May 13)

Exposé sur l'origine et la dynamique des peuplements formés par Pericopsis elata au Sud-Est du Cameroon.

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See detailRecords of human activity during the late-Holocene in the soils of the African dense humid forest
Morin-Rivat, Julie ULg; Biwolé, Achille; Bourland, Nils ULg et al

Conference (2014, April 30)

Recently, several authors gathered data about the presence of past human populations in tropical regions covered by dense forest nowadays. In central Africa, there is a growing body of evidence for past ... [more ▼]

Recently, several authors gathered data about the presence of past human populations in tropical regions covered by dense forest nowadays. In central Africa, there is a growing body of evidence for past human settlements along the Atlantic coast, but very little information is available further inland. In this perspective, soil records seem to be the most appropriated so as to appraise the spatial and temporal extent of human activity in the African dense humid forest. In this paper, we thus aimed to present a synthesis of the archaeological and archaeobotanical data obtained during several fieldwork campaigns in an archaeologically unexplored area of 200,000 km² located in southern Cameroon and the northern Republic of Congo. A total of 275 test pits, among them 30 pedological pits up to 150 cm deep, were excavated in the study area. So as to get a long temporal scale as well as a fine resolution spatial scale, we quantified wood charcoal and charred endocarps in soil samples by layers of 10 cm taken for 100 pits located along transects of systematic sampling. Spatial projections were performed using statistics together with multivariate analyses. AMS radiocarbon dating allowed interpreting the temporal framework. Evidence of past human activities through either artifacts or charred botanical remains was observed in all pits, in particular with the ubiquitous presence of charcoal at each site. Main charcoal peaks were interpreted as fields (slash-and-burn agriculture) in the vicinity of ancient villages, the later marked by the presence of both potsherds and oil palm endocarps. The dichotomy of these kinds of activities may have impacted differentially the environment during the past. The set of 73 radiocarbon dates extending from 15,000 BP to the present time provided more dates in the late-Holocene showing a bimodal distribution which was interpreted as two phases of human expansion with an intermediate phase of population crash. The 2300–1300 BP phase is correlated with the migrations of supposed farming populations from northwestern Cameroon. Between 1300 and 670 BP, less material could be dated. Following that population collapse, the 670–20 BP phase corresponds to a new period of human expansion known as the Late Iron Age. The dates obtained support the established chronology reported for whole central Africa. This study underlines the necessity of fieldwork efforts and of the usefulness of archives sealed in soil records so as to bring new, extensive and precise evidence of human activities in the Congo Basin. [less ▲]

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