References of "Doucet, Jean-Louis"
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See detailExploring ancient charcoal archives in Central Africa
Hubau, Wannes; Morin-Rivat, Julie ULg; Van den Bulcke, Jan et al

Conference (2012, July)

Fossil pollen and charcoal fragments are preserved in lake sediments, in forest soils and in ancient human settlements, were they can be accompanied by artifacts. As such, vegetation history is remarkably ... [more ▼]

Fossil pollen and charcoal fragments are preserved in lake sediments, in forest soils and in ancient human settlements, were they can be accompanied by artifacts. As such, vegetation history is remarkably well archived and sometimes closely linked to cultural history. Direct evidence for Central African vegetation history has been mainly derived from pollen analysis, while the charcoal archive remains hardly explored. However, analysis of charred wood remains has proven worthwhile for palaeovegetation reconstructions in temperate and arid regions. One of the main challenges for charcoal identification in tropical regions is species diversity. Therefore we developed and present a transparent charcoal identification protocol within an umbrella database of species names and metadata, compiled from the on-line database of wood-anatomical descriptions (InsideWood), the database of the world’s largest reference collection of Central African wood specimens (RMCA, Tervuren, Belgium) and inventory and indicator species lists. We applied the protocol on radiocarbon dated charcoal collections sampled in the Mayumbe forest (Bas-Congo, DRCongo), in human settlements along the Aruwimi and Lomami rivers (Province Orientale, DRCongo), along the Sangha river (Sangha department, Republic of the Congo) and in Pallisco logging concessions (East Province of Cameroon). First charcoal identification results are promising and sometimes seem to be taxonomically more precise than pollen identification. However, next to opportunities, we also present some pitfalls when exploring ancient charcoal archives. [less ▲]

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See detailForest anomalies and human occupation in Central Africa during the last two millennia
Livingstone Smith, Alexandre; Beeckman, Hans; Cerisier, François et al

Conference (2012, June 23)

Central African rainforests are no longer considered as pristine, but as the outcome of a long history of changes due mainly to climatic variation. For the later part of the Holocene it has been ... [more ▼]

Central African rainforests are no longer considered as pristine, but as the outcome of a long history of changes due mainly to climatic variation. For the later part of the Holocene it has been hypothesised that climate changes together with human activities triggered modifications in terms of distribution and botanical composition. While developing a research project to explore the mechanisms of forest change, new research avenues for the archaeology of rainforests became apparent. In this paper, we outline the results of this approach, implemented on a forest concession (Cameroon). We introduce our methodology based on the analysis of botanical inventories (focused on large trees of human linked species and light demanding species), coupled to systematic core boring and test pits. A sampling strategy for the collection of charcoal and its identification is developed and archaeological remains found in association are analyzed at the Royal Museum for Central Africa. [less ▲]

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See detailCurrent Pericopsis elata (Fabaceae) patches in southeastern Cameroon: remnants of a long and rich Human-rainforest relationship?
Bourland, Nils ULg; Cerisier, François; Livingstone Smith, Alexandre et al

Poster (2012, June 23)

Pericopsis elata is one of the most valuable African timber species. This IUCN Red Listed tree suffers from a lack of regeneration, thus its current presence provokes questioning. Our work aimed at ... [more ▼]

Pericopsis elata is one of the most valuable African timber species. This IUCN Red Listed tree suffers from a lack of regeneration, thus its current presence provokes questioning. Our work aimed at understanding its origins so as to help securing its future. This study, lead away from engineering works, was conducted in four different sites located within the natural distribution area of the species and taking into account the different growing conditions were the species occurs. Our observations are based on an analysis of charcoal elements and pottery fragments discovered in subsurface layers of soils as well as current botanical and pedological surveys. Evidence of past human activities we found led to the assumption that this part of the Congo Basin was much more inhabited than previously thought. Some of the results obtained for P. elata could apply for other long lived light demanding species growing in the same environment [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 detailAncient macro-charcoals analysis as a tool to restitute the past history of African tropical forests
Morin-Rivat, Julie ULg; Doucet, Jean-Louis ULg; Beeckman, Hans

Scientific conference (2012, May 22)

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See detailDéfinition du profil écologique de l'azobé, Lophira alata, une espèce ligneuse africaine de grande importance : synthèse bibliographique et perspectives pour des recherches futures
Biwole, Achille ULg; Bourland, Nils ULg; Daïnou, Kasso ULg et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2012), 16(2), 217-228

Over two decades, labors made in order to promote sustainable management of African tropical forests are tackled to the lack of knowledge about this complex ecosystem. Ecological parameters of timber ... [more ▼]

Over two decades, labors made in order to promote sustainable management of African tropical forests are tackled to the lack of knowledge about this complex ecosystem. Ecological parameters of timber species are no more studied, this complicates long-term sustainable forest management. This literature review related to the ecology and silviculture of ekki, Lophira alata Banks ex C.F.Gaertn. (Ochnaceae), a main African timber species recorded as “vulnerable” in the IUCN Red List, will serve as a study’s case. The planned literature review reveals the doubt about its taxonomy, as well as the lack of understanding concerning its reproductive biology, growth conditions, population dynamics parameters, and the spatial distribution of its genetic diversity. The deficiency of knowledge about its ecological needs and the factors which have historically influenced its population dynamics explain why most silvicultural trails provide hazardous and uncertain results. Remedying these gaps in order to improve its ecological characterization and innovative silvicultural trails, would be a significant contribution to the sustainable management of its populations. [less ▲]

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See detailDynamique forestière et enrichissements forestiers. Site de Mbang. Rapport n° 8.
Doucet, Jean-Louis ULg; Amandé, Jean; Bracke, Charles et al

Report (2012)

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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 detailHow pristine is the Congo Basin forest ? Some answers from Erythrophleum spp. (Caesalpiniaceae) and Pericopsis elata (Fabaceae) natural stands in southeastern Cameroon
Bourland, Nils ULg; Livingstone Smith, Alexandre; Guion, Hélène ULg et al

Poster (2012, March 01)

Erythrophleum spp. and Pericopsis elata are two important African timber taxa suffering from regeneration problems. Those light demanding trees could have established in openings made by past human ... [more ▼]

Erythrophleum spp. and Pericopsis elata are two important African timber taxa suffering from regeneration problems. Those light demanding trees could have established in openings made by past human activities (mainly slash-and-burn cultivation). Our study aimed at verifying this assumption in a 340,000 ha forest concession in southeastern Cameroon. Anthracological excavations were made alongside transects opened in patches where those taxa occur as well as the surrounding environment. Numerous charcoal elements and some pottery fragments were found in excavated soils in all studied sites. Charcoals and pieces of pottery were found within the first 100 and 50 cm of soil, respectively. According to radiocarbon dating conducted on charcoals and burnt seeds, fires occurred between 2,150 to 195 years BP. This finding was consistent with the analysis of archaeological materials decoration techniques. Our results revealed intense past anthropological activities in this area, seriously questioning the assumption of a pristine Congo Basin [less ▲]

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See detailCould current Pericopsis elata (Fabaceae) patches in southeastern Cameroon be reasonably linked to past anthropogenic activities ?
Bourland, Nils ULg; Cerisier, François ULg; Livingstone Smith, Alexandre et al

Poster (2012, March 01)

Pericopsis elata is one of the most valuable African timber species. This IUCN Red Listed tree suffers from a lack of regeneration, thus its current presence provokes questioning. Our work aimed at ... [more ▼]

Pericopsis elata is one of the most valuable African timber species. This IUCN Red Listed tree suffers from a lack of regeneration, thus its current presence provokes questioning. Our work aimed at understanding its origins so as to help securing its future. This study, lead away from engineering works, was conducted in four different sites located within the natural distribution area of the species and took into account the different growing conditions were the species occurs. Our observations were based on an analysis of charcoal elements and pottery fragments discovered in subsurface layers of soils as well as on current botanical and pedological surveys. Discovered evidence of past human activities led to the assumption that this part of the Congo Basin was much more inhabited than previously thought. Some of the results obtained for P. elata could apply for other long lived light demanding species growing in the same environment. [less ▲]

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See detailRole of western lowland gorilla (Gorilla gorilla gorilla Savage & Wyman, 1847) on the dynamics of tropical logged forest ecosystems
Haurez, Barbara ULg; Petre, Charles-Albert ULg; Doucet, Jean-Louis ULg

Poster (2012, February 08)

The western lowland gorilla (Gorilla gorilla gorilla Savage & Wyman) (WLG) which is considered as a critically endangered species by IUCN, could play a fundamental function in seeds dispersal of several ... [more ▼]

The western lowland gorilla (Gorilla gorilla gorilla Savage & Wyman) (WLG) which is considered as a critically endangered species by IUCN, could play a fundamental function in seeds dispersal of several plant species. This could be related to its frugivorous diet, its stomach capacity and the long gut retention time of the ingested food, its extensive daily path length, and its ability to swallow seeds of variable sizes. In addition, this animal tends to deposit most of ingested seeds in suitable habitats (especially logging gaps and old logging roads) for light-demanding plant development. This research will be conducted within the moist evergreen forest of Central Gabon in a logging concession granted to the company CEB Precious Woods. A preliminary study was undertaken as a Master thesis. It was aiming at obtaining a first insight of interactions between WLG and timber exploitation in Central Gabon and at assessing the extent to which they may benefit of each other. WLG abundances were estimated in unlogged and logged sites in the concession, and nesting behavior described. Seeds dispersed during the study period (February-May) by WLG were identified through fecal analysis. Relatively high WLG abundances were observed in the concession. WLG were found to nest preferentially in open areas and to frequently use old logging road network for nesting and feeding. Sixteen species were observed to be dispersed by WLG. Seeds of the most abundant species, Santiria trimera, were subjected to four treatments: (1) passed seeds, (2) passed seeds in fecal matrix, (3) seeds surrounded by fresh pulp and (3) seeds extracted from fresh fruits. The germination successes of S. trimera were significantly higher after gut passage partly thanks to fruit pulp removal. Our PhD study aims to characterize the functional ecology of WLG in tropical forests dynamics, especially regarding logging biotopes. Our research will be organized in three parts: (1) the survey of gorilla populations in the study area coupled with the characterization of their nests and habitats, (2) the study of dispersed species and of the effect of passage through gorilla gut on seed germination, (3) the estimate of dispersal distances for the species Santiria trimera (Burseraceae) by using molecular markers. Data for the second and third parts will be collected in one site selected thanks to the results of the survey for its high gorilla density, to assess the following assumptions: (1) gorillas favor the regeneration of many plant species, including timber trees; (2) they improve the genetic diversity and limit the genetic structure by widening the genetic pool and dispersing diasporas on large distances. If these hypotheses are accepted, sylvicultural practices may be adapted so as to take advantage from the presence of gorilla population. [less ▲]

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See detailDéfinition du profil écologique de l'azobé (Lophira alata Banks ex Gaertn F., Ochnaceae) dans les forêts sempervirentes du Cameroun
Biwole, Achille ULg; Bourland, Nils ULg; Doucet, Jean-Louis ULg

Poster (2012, February 08)

Ekki or L. alata is a commercial timber species in Guinea-Congolian region considered vulnerable (IUCN, 2011). Indeed, its population structure shows a severe lack of regeneration in some rainforests ... [more ▼]

Ekki or L. alata is a commercial timber species in Guinea-Congolian region considered vulnerable (IUCN, 2011). Indeed, its population structure shows a severe lack of regeneration in some rainforests (Palla et al., 2002). Moreover, in logging areas, insufficient knowledge about its ecological profile limits any reliable modeling of population dynamics on a long term. Consequently, original research, to improve its ecological characterization to ensure its sustainable management is conducted in moist evergreen forest in southern Cameroon. First results on population dynamics of this species show, in plots study of recruitment, a population without major deficit regeneration. On its silvicultural ability, although that estimated on plantations on parks under 2 years old, the trends of growth (ca 30 and 0.5 cm / year respectively in height and diameter) and mortality (3, 3% / year) suggest a positive perspective. Current work in relation to other topics of research should provide further insights into its ecological profile in the evergreen forests of Cameroon. [less ▲]

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