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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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See detailQuaternary rainforests of the Northern Congo Basin: contribution of charcoal analysis
Morin-Rivat, Julie ULg; Bremond, Laurent; Gillet, Jean-François ULg et al

Conference (2014, March 27)

In comparison with the wood charcoals uncovered in the soils of the temperate regions, charcoals from the tropical regions remain little studied yet, in particular those from the dense humid forests of ... [more ▼]

In comparison with the wood charcoals uncovered in the soils of the temperate regions, charcoals from the tropical regions remain little studied yet, in particular those from the dense humid forests of Central Africa. Here we aim at showing the interest of the analysis of soil charcoals so as to understand the current environments through some examples of taxonomical identifications conducted on charcoals sampled in several soil pits in Cameroon and in the Republic of the Congo. These charcoals were hand-split then observed under an incident light microscope. The anatomical features that are hold in the charcoals and described according to a standard method were compared to wood samples from the reference collection of the RMCA. Results demonstrated that the identified species are still present in the vegetal environment today and that only limited changes occurred over the past two millennia. Charcoal analysis can thus allow a better understanding of the past history of the forests in relationship with the ancient disturbances. The temporal and spatial framework of human settlements as well as the impact of the colonial period on the evolution of the forest is also discussed. [less ▲]

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See detailHistoire humaine des forêts tropicales du nord du Bassin du Congo durant les deux derniers millénaires
Morin-Rivat, Julie ULg; Biwolé, Achille; Bourland, Nils ULg et al

Scientific conference (2014, March 26)

Identifier les indices d’activités humaines anciennes et les mettre en relation avec la composition floristique actuelle grâce à une approche multidisciplinaire.

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See detailWood charcoal analysis: a relatively new tool for palaeoecology in tropical Africa
Morin-Rivat, Julie ULg; Biwole, Achille ULg; Bourland, Nils ULg et al

Scientific conference (2014, February 14)

This is an introduction about wood charcoal properties, collection and taxonomical identification in the framework of palaeoecological studies in Central Africa through examples of possible applications.

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See detailImprove the characterization of tropical forests to improve management: policy brief
Gourlet-Fleury, Sylvie; Aleman, Julie; Bayol, Nicolas et al

Report (2014)

CoForChange has shown that management plans based on timber stock recovery are not enough to ensure the sustainability of these production forests. The variability of forest characteristics and their ... [more ▼]

CoForChange has shown that management plans based on timber stock recovery are not enough to ensure the sustainability of these production forests. The variability of forest characteristics and their different responses to disturbance should be considered in management decisions. [less ▲]

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See detailLes forêts à Marantaceae au sein de la mosaïque forestière du Nord de la République du Congo : origines et modalités de gestion
Gillet, Jean-François ULg

Doctoral thesis (2013)

The Marantaceae forests are conspicuous by an unusual physiognomy with a giant herbaceous continuous stratum in association with a scattered tree component regenerating with difficulty. This vegetation ... [more ▼]

The Marantaceae forests are conspicuous by an unusual physiognomy with a giant herbaceous continuous stratum in association with a scattered tree component regenerating with difficulty. This vegetation, arranged as a heterogeneous patchwork within the lowland semi-deciduous forests, is widely extended in the Northern Republic of Congo. The thesis aims to define and describe the vegetation types of this forest patchwork in order to identify the key factors that have shaped it and to recommend an appropriate forestry. To achieve this, the study was conducted in the CIB-OLAM logging concession (Sangha and Likwala departments). Two types of monodominant G. dewevrei forests and three hydromorphic vegetation types have been described trough on ordination multivariate analysis of the woody stand in relation with the hydrological conditions. In addition, a multi-strata classification of mixed terra firma forests has individualized five vegetation types that are defined and characterized. These are: (1.1) open vegetation types with Marantaceae and Aframomum cf. subsericeum, (1.2) sparse Marantaceae forests with Megaphrynium macrostachyum and (1.3) with Haumania liebrechtsiana, (1.4) dense forests with Marantaceae and (2) moist semi-deciduous dense forests (3 forms: (2.1) with Sarcophrynium schweinfurthianum, (2.2) with Haumania danckelmaniana and (2.3) with Triplochiton scleroxylon). They are characterized by their specific richness, floristic composition and/or structural parameters. Thanks to an archaeo-pedological study coupled with 14C dating, we established that the Marantaceae forests suffered the strongest past disturbances. The perturbations were mostly caused by humans and predominated around 1,550 yrs BP. They would be related to an expansion phase of the oil palm Elaeis guineensis and its exploitation by humans. The simultaneous degradation of the forest cover, combined with poor and wet soils, has facilitated the expanding of giant herbs, gradually inhibiting the tree regeneration. The dense forests on the contrary, whose the dominant species are light-demanding and wind-dispersed trees (eg. T. scleroxylon) would have a more recent origin. Indeed, they date back about 7 to 2 centuries and are related to shifting cultivation on richer and well-drained soils. The logging within the open canopy Marantaceae vegetation types results in a recovery of the forest dynamic on skid trails. Thanks to the destruction of the herbaceous understorey by logging equipment. On these trails, an assisted regeneration by selection and freeing of seedlings and an additional planting turns out to be an effective technique for woody species regeneration. The results are especially encouraging for the following species: Canarium schweinfurthii, Terminalia superba, Ricinodendron heudelotii and Nauclea diderrichii whose average height growth is respectively 154, 130, 125 and 124 cm, one year after the silvicultural treatment. Given the evolutionary dynamics of these open canopy Marantaceae vegetation types, systematic reforestation with timber species on skid trails seems to be the most appropriate silvicultural technique to ensure sustainable exploitation. [less ▲]

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See detailAbove-ground biomass and structure of 260 african tropical forests
Lewis, Simon L.; Sonké, Bonaventure; Sunderland, Terry et al

in Philosophical Transactions of the Royal Society B (2013), 368

We report above-ground biomass (AGB), basal area, stemdensity and wood mass density estimates from 260 sample plots (mean size: 1.2 ha) in intact closed-canopy tropical forests across 12 African countries ... [more ▼]

We report above-ground biomass (AGB), basal area, stemdensity and wood mass density estimates from 260 sample plots (mean size: 1.2 ha) in intact closed-canopy tropical forests across 12 African countries. Mean AGB is 395.7 Mg dry mass ha21 (95% CI: 14.3), substantially higher than Amazonian values, with the Congo Basin and contiguous forest region attaining AGB values (429 Mg ha21) similar to those of Bornean forests, and significantly greater than East or West African forests. AGB therefore appears generally higher in palaeo- comparedwithneotropical forests.However, mean stem density is low(426+11 stems ha21 greater than or equal to 100 mm diameter) compared with both Amazonian and Bornean forests (cf. approx. 600) and is the signature structural feature of African tropical forests. While spatial autocorrelation complicates analyses, AGB shows a positive relationship with rainfall in the driest nine months of the year, and an opposite association with the wettest three months of the year; a negative relationship with temperature; positive relationship with clay-rich soils; and negative relationshipswith C :Nratio (suggesting a positive soil phosphorus–AGB relationship), and soil fertility computed as the sum of base cations. The results indicate that AGB is mediated by both climate and soils, and suggest that the AGB of African closed-canopy tropical forests may be particularly sensitive to future precipitation and temperature changes. [less ▲]

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See detailClimatic and cultural changes in the west Congo Basin forests over the past 5000 years
Oslisly, Richard; White, Lee; Bentaleb, Ilham et al

in Philosophical Transactions : Biological Sciences (2013), 368(1625), 1-11

Central Africa includes the world's second largest rainforest block. The ecology of the region remains poorly understood, as does its vegetation and archaeological history. However, over the past 20 years ... [more ▼]

Central Africa includes the world's second largest rainforest block. The ecology of the region remains poorly understood, as does its vegetation and archaeological history. However, over the past 20 years, multidisciplinary scientific programmes have enhanced knowledge of old human presence and palaeoenvironments in the forestry block of Central Africa. This first regional synthesis documents significant cultural changes over the past five millennia and describes how they are linked to climate. It is now well documented that climatic conditions in the African tropics underwent significant changes throughout this period and here we demonstrate that corresponding shifts in human demography have had a strong influence on the forests. The most influential event was the decline of the strong African monsoon in the Late Holocene, resulting in serious disturbance of the forest block around 3500 BP. During the same period, populations from the north settled in the forest zone; they mastered new technologies such as pottery and fabrication of polished stone tools, and seem to have practised agriculture. The opening up of forests from 2500 BP favoured the arrival of metallurgist populations that impacted the forest. During this long period (2500–1400 BP), a remarkable increase of archaeological sites is an indication of a demographic explosion of metallurgist populations. Paradoxically, we have found evidence of pearl millet (Pennisetum glaucum) cultivation in the forest around 2200 BP, implying a more arid context. While Early Iron Age sites (prior to 1400 BP) and recent pre-colonial sites (two to eight centuries BP) are abundant, the period between 1600 and 1000 BP is characterized by a sharp decrease in human settlements, with a population crash between 1300 and 1000 BP over a large part of Central Africa. It is only in the eleventh century that new populations of metallurgists settled into the forest block. In this paper, we analyse the spatial and temporal distribution of 328 archaeological sites that have been reliably radiocarbon dated. The results allow us to piece together changes in the relationships between human populations and the environments in which they lived. On this basis, we discuss interactions between humans, climate and vegetation during the past five millennia and the implications of the absence of people from the landscape over three centuries. We go on to discuss modern vegetation patterns and African forest conservation in the light of these events. [less ▲]

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See detailHow closely are Pericopsis elata (Fabaceae) patches linked to past human disturbances in South-Eastern Cameroon
Bourland, Nils ULg; Cerisier, François; Daïnou, Kasso ULg et al

Conference (2013, June 26)

Studies conducted in the Congo Basin forests concluded that soil parameters and large disturbances induced by human activities since 3000–2000 BP could be the main driver for the persistence of long lived ... [more ▼]

Studies conducted in the Congo Basin forests concluded that soil parameters and large disturbances induced by human activities since 3000–2000 BP could be the main driver for the persistence of long lived light-demanding tall tree species. Today most of the timber species belong to this group, among them Pericopsis elata (Fabaceae). Like many other light-demanding trees, this species suffers from important regeneration problems. While the conditions for its establishment must have been met in the past, they obviously have become unfavourable. Because of ongoing logging activities and a natural decline of its populations, this species is recorded in both the IUCN Red List and the CITES Appendix II listings. Our goal was to investigate the roles of both pedological and anthropogenic factors in the persistence of forest patches characterized by this clustered species. Soil surveys, botanical inventories and anthracological excavations were conducted in three different forest sites located in south-eastern Cameroon. P. elata patches (3.3-14.7 ha) were studied and compared to their close surroundings. No statistical differences were observed between the results of botanical inventories conducted inside and outside the patches (Morisita-Horn indices from 0.69-0.77). Soils only differed in Fe content, but otherwise no significant differences could be observed. Charcoal is widespread and abundant in study sites, mostly inside the patches. Charcoal radiocarbon dating (2,150-195 BP) was consistent with decoration techniques of archaeological materials that we discovered. The average age of P. elata individuals coincides with fire events that occurred in a region where fires rarely occur naturally. We present evidence of past anthropogenic disturbances (human settlement, slash-and-burn cultivation) in the Congolese mixed moist semi-evergreen forest in south-eastern Cameroon. We discuss the potential influence of our findings on the management of light-demanding tall trees populations in a context of logging activities. [less ▲]

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See detailLes équations allométriques pan-tropicales plurispécifiques sont-elles valables en Afrique centrale ?
Fayolle, Adeline ULg; Doucet, Jean-Louis ULg; Gillet, Jean-François ULg et al

in Picard, Nicolas; Henry, Mathieu (Eds.) Compte-rendu de l'Atelier scientifique régional sur les équations allométriques en Afrique Centrale : PREREDD, Yaoundé 2-5 avril 2013 (2013, April)

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See detailLes forêts vierges du Bassin du Congo - mythe ou réalité ?
Morin-Rivat, Julie ULg; Bourland, Nils ULg; Gillet, Jean-François ULg et al

Scientific conference (2013, March 21)

Les forêts du bassin du Congo ont longtemps été considérées comme des massifs historiquement épargnés par l'action de l'homme. Des résultats plus ou moins récents de recherches scientifiques remettent en ... [more ▼]

Les forêts du bassin du Congo ont longtemps été considérées comme des massifs historiquement épargnés par l'action de l'homme. Des résultats plus ou moins récents de recherches scientifiques remettent en question cette vision des forêt denses humides africaines. [less ▲]

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See detailLarge trees drive forest aboveground biomass variation in moist lowland forests accross the tropics
Slik, J. W. Ferry; Paoli, Gary; McGuire, Krista et al

in Global Ecology & Biogeography (2013), 22

Aim Large trees (d.b.h. 70 cm) store large amounts of biomass. Several studies suggest that large trees may be vulnerable to changing climate, potentially leading to declining forest biomass storage. Here ... [more ▼]

Aim Large trees (d.b.h. 70 cm) store large amounts of biomass. Several studies suggest that large trees may be vulnerable to changing climate, potentially leading to declining forest biomass storage. Here we determine the importance of large trees for tropical forest biomass storage and explore which intrinsic (species trait) and extrinsic (environment) variables are associated with the density of large trees and forest biomass at continental and pan-tropical scales. Location Pan-tropical. Methods Aboveground biomass (AGB) was calculated for 120 intact lowland moist forest locations. Linear regression was used to calculate variation in AGB explained by the density of large trees. Akaike information criterion weights (AICcwi) were used to calculate averaged correlation coefficients for all possible multiple regression models between AGB/density of large trees and environmental and species trait variables correcting for spatial autocorrelation. Results Density of large trees explained c. 70% of the variation in pan-tropical AGB and was also responsible for significantly lower AGB in Neotropical [287.8 (mean) 105.0 (SD) Mg ha-1] versus Palaeotropical forests (Africa 418.3 91.8 Mg ha-1; Asia 393.3 109.3 Mg ha-1). Pan-tropical variation in density of large trees and AGB was associated with soil coarseness (negative), soil fertility (positive), community wood density (positive) and dominance of wind dispersed species (positive), temperature in the coldest month (negative), temperature in the warmest month (negative) and rainfall in the wettest month (positive), but results were not always consistent among continents. Main conclusions Density of large trees and AGB were significantly associated with climatic variables, indicating that climate change will affect tropical forest biomass storage. Species trait composition will interact with these future biomass changes as they are also affected by a warmer climate. Given the importance of large trees for variation in AGB across the tropics, and their sensitivity to climate change, we emphasize the need for in-depth analyses of the community dynamics of large trees. [less ▲]

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See detailThe abundance of charcoal fragments emphasizes the assumption of huge palaeofires in the mixed moist semi-evergreen rainforest of the northern republic of Congo
Gillet, Jean-François ULg; Doucet, Jean-Louis ULg

in Damblon, Freddy (Ed.) Proceedings of the Fourth International Meeting of Anthracology (2013)

In this paper, we study the origins of the northern Congo Republic rainforests. Macroscopic charcoal fragments were systematically recorded through auger investigations and pits observations in four ... [more ▼]

In this paper, we study the origins of the northern Congo Republic rainforests. Macroscopic charcoal fragments were systematically recorded through auger investigations and pits observations in four forest types: the open canopy Marantaceae forest, the dense forest with Marantaceae, the Gilbertiodendron dewevrei forest and the Triplochiton scleroxylon forest. In addition, the charred Elaies guineensis seeds were distinguished from the other charcoals in the pits. Ten selected charcoals, including charred E. guineensis seeds, were dated by AMS. Abundance of charcoal fragments in the soils at various depths indicated several episodes of fires in the region. A dryer climatic phase, between 2320 and 1330 BP, associated with a large scale human occupation related to the important harvesting of oil palm nuts, could explain the widespread Marantaceae forests. Recent slash-and-burn shifting cultivation, c. 200 BP, would allow T. scleroxylon installation. Implications for forest management are discussed. [less ▲]

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See detailPericopsis elata (Harms) Meeuwen in Cameroon: Ecological Check-up of an Endangered Timber Species
Bourland, Nils ULg; Kouadio, Yao Lambert; Lejeune, Philippe ULg et al

Poster (2012, June 20)

Pericopsis elata (Fabaceae – assamela, afrormosia, kokrodua) is a high valued timber species of the moist semi deciduous African forests. Because of logging which started more than 50 years ago, it is ... [more ▼]

Pericopsis elata (Fabaceae – assamela, afrormosia, kokrodua) is a high valued timber species of the moist semi deciduous African forests. Because of logging which started more than 50 years ago, it is considered as threatened and included on both IUCN Red List and CITES Appendix II. Nevertheless, there is still little information available on the species ecology: essential biological parameters controlling its population dynamics remain unknown. Our study first aims at improving the knowledge of its main ecological parameters, then at assessing the impact of selective logging on its populations in a forest management unit in Cameroon (ca 120,000 ha). After inventorying the species (sampling rate of 1.2%), mortality and growth were assessed over continuous 5 and 2-year periods in unlogged and logged areas, respectively. Phenology was monitored in the unlogged forest during 5 years (leaf shedding and flushing, flowering, ripe and unripe fruiting). The population structure followed a bell-shaped curve. Mean annual diameter increments in both environments did not differ significantly between unlogged and logged areas (0.29±0.06 0.31±0.04 cm for unlogged and logged areas, respectively). P. elata is a deciduous species that flowers at the end of the main dry season (Marsh-April). The minimum reproduction and effective flowering diameters were, respectively, 32 and 37 cm. Fruit maturation took place during 7 months (the seed rain occurs in December-January), but all unripe fruits abort 3 years out of 5. With a minimum logging diameter of 90 cm, the recovery rate computed over a 30-year period was greater than 100%. Selective logging harvested only 12.1% of the total number of seed trees and had little influence on the species biological parameters. Securing sufficient regeneration as a post-logging action is probably the most important consideration for achieving long-term sustainability. [less ▲]

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See detailRecent disturbances in the Congo Basin : an anthracological contribution to vegetation reconstructions
Morin-Rivat, Julie ULg; Hubau, Wannes; Gillet, Jean-François ULg et al

Poster (2012, March 01)

In contrast to the well-known vegetation history of the northern hemisphere, few is known about past vegetation change in Central Africa. However, recent palaeoecological and biogeographical studies ... [more ▼]

In contrast to the well-known vegetation history of the northern hemisphere, few is known about past vegetation change in Central Africa. However, recent palaeoecological and biogeographical studies suggest that early human disturbances had a substantial influence on Central Africa vegetation patterns, particularly allowing the expansion of light-demanding species. This interesting hypothesis is the basis of one of the main research questions of the ERA-net BIODIVERSA CoForChange project: what was and is the relationship between (increasing) human activity and vegetation change? A recently developed protocol for the identification of ancient Central African charcoal fragments opened the door for vegetation reconstructions with a high spatial and taxonomical resolution. Therefore, we chose to study macro-charcoals from pedoanthracological profiles situated in N Congo and SE Camero0n. In total, 48 taxa were found in nine radiocarbon dated profiles. At the moment, three taxa have been identified down to species level. First, we found numerous fragments of Gilbertiodendron dewevrei under a current monodominant forest of G. dewevrei (40 cm depth, 1421-1327 cal. BP). This seems to confirm the presumption that monodominant forests of G. dewevrei, shade-bearer species, are relatively stable. Second, we evidenced the lack of Triplochiton scleroxylon charcoals under a T. scleroxylon stand, which could confirm the hypothesis of the recent nature of those stands. Finally, our results suggest that taxonomic diversity of charcoal findings in open canopy Marantaceae forests is greater than in dense forests. Pterocarpus soyauxii and Millettia drastica have been found under an open Marantaceae forest at 40 cm depth (1184-1055 cal. BP). The abundance of the light-demanding species P. soyauxii appears to be decreasing over time (levels 20 to 40 cm depth) to the benefit of giant herbs. Anthracology in Central Africa is on the rise and the first results of the CoForChange project are promising. More identifications will follow, resulting in a better understanding of the evolution of Central African forests. [less ▲]

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See detailExtent of paleofires and past human settlements in the current rainforest patchwork of the Northern Republic of Congo
Gillet, Jean-François ULg; Doucet, Jean-Louis ULg

Poster (2012, January 04)

Objectives The origins of the patchwork of lowland semi-deciduous forests in the Northern Republic of Congo were apprehended. The aim of this study was to show that dense forests suffered fewer ... [more ▼]

Objectives The origins of the patchwork of lowland semi-deciduous forests in the Northern Republic of Congo were apprehended. The aim of this study was to show that dense forests suffered fewer disturbances than the open canopy forest types. Old disturbances associated with fires and human settlements seem to have had and still have today a substantial impact on the physiognomy and the composition of the forest types. Understanding past forest dynamics is a major component to predict the effects of both present climate change and human activities. Method Fifteen locations were studied along a 400-km-long SW-NE gradient in the NW of the Congo Basin through the ERA-net BiodivERsA CoForChange project. An anthraco-archaeological study was carried out in association with floristic inventories of three strata. Two main geology substrates were considered: the Mesozoic sandstones and Quaternary alluvial deposits. The abundance of charcoal fragments and human artifacts were evaluated by a network of 1-m-deep boring augers (n =208) and a 1.5-m-deep reference soil pit (n =15) in each site. A rating system was used to quantify the abundance of charcoal, charred Elaeis guineensis seeds and other artifacts (ceramic and metallurgic slag). Estimations were based on 20-cm-depth intervals (augers) or on pedological layers (pits). Twelve radiocarbon dating were performed in the major disturbed layers of each vegetation type studied. Results Two main groups of vegetation were highlighted according to the relative openness of the woody stand, the importance of the woody regeneration, and the development of the herbaceous cover. The two dense forests sampled were preferentially found in the northern part: the dense forest with Manilkara mabokeensis and Haumania dankelmaniana, and the Gilbertiodendron dewevrei forest on dry land. Most parts of the understorey exhibited the woody regeneration. The southern part presented more openness including the largest areas of open canopy vegetation types. Three forest types were identified: the Macaranga barteri pioneer forest, the open canopy vegetation type with Aframomum and Marantaceae, and the sparse forest with Megaphrinium macrostchyum and/or Haumania liebrestisiana. The understorey was a dense thicket of giant herbs belonging to the families Marantaceae and Zingiberaceae, causing a very scarce woody regeneration. Regardless the auger depth, charcoals were more profuse in the soils of the southern open canopy vegetation types (2-Way ANOVA, F=5.46, p=0.02). As in pit layers, charred oil palm nuts were more plentiful in the soils of these vegetation types (Mann-Whitney test, p<0.05). Of the five sites containing artifacts, only one recent potsherd dated 466-302 BP was located in dense forest but near a main river. The oldest signs of ceramic and metallurgical activities dated 2160-1407 BP were found in the current open canopy vegetation types. Within the latter, two expansion phases of the oil palm tree E. guineensis were observed: between 2146-1055 BP and 558-347 BP. Conversely, the oldest palaeofire was discovered in the M. mabokeensis dense forest and dated at 5467-5285 BP. Conclusions The dense forests contained less evidence of ancient fires and human settlements. They currently include evergreen and shade-tolerant tree species such as G. dewevrei and M. mabokeensis. The more sustained and repeated fires in the open canopy vegetation types were often associated with ancient human occupation. Today, the light-demanding giant herbaceous species such as Aframomum sp. and M. macrostchyum proliferate in the understorey below a simplified woody component of pioneer species such as M. barteri. The largest expansion phases of the oil palm tree E. guineensis in the southern part would be linked to ancient human occupation associated with larger canopy openings and fire events. The water availability, more evenly distributed near the heavily-irrigated Congo Basin, would also be a discriminating factor. [less ▲]

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See detailA commented checklist of woody plants in the Northern Republic of Congo
Gillet, Jean-François ULg; Doucet, Jean-Louis ULg

in Plant Ecology and Evolution (2012), 145(2), 258-271

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See detailFirst results of an enrichment method tested on recent skidding trails in Marantaceae forests (Republic of Congo)
Gillet, Jean-François ULg; Doucet, Jean-Louis ULg

in CIRAD Montpellier (Ed.) IUFRO International Conference, Research priorities in tropical silviculture : towards new paradigms ? : Abstracts (2011, November)

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See detailSoil seed bank characteristics in Cameroonian rainforests and implications for post-logging recovery
Daïnou, Kasso ULg; Bauduin, Aline ULg; Bourland, Nils ULg et al

in Ecological Engineering (2011), 37(10), 1499-1506

The soil seed bank is considered as an important component for resilience of climacic vegetation. No investigation has ever been conducted in Central African rainforests regarding this topic. We studied ... [more ▼]

The soil seed bank is considered as an important component for resilience of climacic vegetation. No investigation has ever been conducted in Central African rainforests regarding this topic. We studied the soil seed bank characteristics in relation to the standing vegetation in three Cameroonian forest zones with different disturbance regimes. There was no significant difference between sites in terms of density of the seed bank. But dissimilarities of the floristic compositions between sites were high. Overall, seeds came from 43 species including three commercial tree species. Whereas the seedlings emerging from soil samples mostly came from weedy and short-lived pioneer species, climax species predominated in the extant vegetation, leading to a very weak similarity between soil seed flora and the surrounding vegetation. Canopy openness could significantly affect the species richness of soil seed stocks but not the seed density. These results show that the soil seed bank contribution to the resilience of mature tropical forests is low. In particular, very few timber tree species could benefit from soil seed stocks for their regeneration. Therefore, the development of enrichment techniques including use of the soil seed bank as a source of tree regeneration in such a context would be irrelevant. [less ▲]

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