References of "Doucet, Jean-Louis"
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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 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 detailAfzelia populations, a poorly known species complex of timber trees from African tropical forests
Donkpegan, Segbedji ULg; Hardy, Olivier; Daïnou, Kasso ULg et al

Scientific conference (2013, June 26)

The fate of African tropical forests is a major concern for conservation, while their biodiversity is still poorly known. The purpose of this poster is to provide an update of knowledge of the genus ... [more ▼]

The fate of African tropical forests is a major concern for conservation, while their biodiversity is still poorly known. The purpose of this poster is to provide an update of knowledge of the genus Afzelia, a complex of sister tree species exploited for their wood in central Africa. The distribution of Afzelia in Africa suggests various adaptations to ecological factors. In fact, most of Afzelia species occur in parapatry and are so similar that they are often not distinguished by logging companies and forests managers. We show that the genus remains understudied in Africa although some of its species are considered as endangered or vulnerable. Therefore, a revision of its taxonomy along with thorough investigations of ecological and genetic aspects of Afzelia populations, using molecular markers currently in development (nSSR, cpDNA and nDNA), should be relevant and of great interest for conservation and sustainable management purposes. We will describe the different and complementary morpho-genetic approaches that will be used to investigate the biogeographical history of Afzeliapopulation in concert with species boundary questions. [less ▲]

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See detailAnalyzing soil charcoals to assess the naturalness of tropical forest
Morin-Rivat, Julie ULg; Gorel, Anaïs-Pasiphaé; Daïnou, Kasso ULg et al

Conference (2013, June 26)

For conservation biology and sustainable management, the natural character of tropical forest is a crucial issue. Its assessment is usually based on ecological proxies such as forest composition and ... [more ▼]

For conservation biology and sustainable management, the natural character of tropical forest is a crucial issue. Its assessment is usually based on ecological proxies such as forest composition and structure. However the estimation made on this basis only considers short term processes at a local scale. In contrast the long term processes are appraised by palaeoecological proxies (such as pollen) at a regional scale. So as to assess the degree of naturalness of tropical ecosystems in a conservation perspective it is important to combine a long temporal scale as well as a fine resolution spatial scale. Such approaches using palaeoecological proxies have been recently tested in temperate Europe but little in tropical ecosystems. Nonetheless the long term preservation of the palaeoecological material and its broad presence in the environment are necessary conditions to fulfill. In this perspective soil charcoal appears to meet these requirements. In this paper we aimed at assessing the naturalness of tropical forest using soil charcoal from southeastern Cameroon. Fieldwork involving as well archaeology as botany was undertaken at 53 sites. We quantified charcoal in soil samples by layers of 10 cm taken from pits located in the center of plots of botanical inventory. Spatial projections were performed using statistics together with multivariate analyses. Radiocarbon dating allowed interpreting the temporal framework. Results showed 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. These practices shaped the forest over time which cannot be considered as natural anymore. This underlines the potential input of the use of palaeoecological material in conservation biology and sustainable management issues. Charcoal fragments are under taxonomical identification and may provide new insights on the long term history of forest composition. [less ▲]

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See detailImpacts of past Human disturbances on present day tree species assembly in the tropical forests of South-East Cameroon
Vleminckx, Jason; Doucet, Jean-Louis ULg; Daïnou, Kasso ULg et al

Poster (2013, June 25)

Non-random spatial distribution of trees is the result of both neutral and deterministic factors. Neutral models suggest that species within a community are equally competitive, with spatial structures ... [more ▼]

Non-random spatial distribution of trees is the result of both neutral and deterministic factors. Neutral models suggest that species within a community are equally competitive, with spatial structures mainly due to dispersal limitation. Deterministic (or non-neutral) models consider species assemblages as the result of what we name “induced spatial dependence”, where forcing (explanatory) variables shape diversity organization. However, deterministic models have often included habitat variables only, without considering human disturbance which we know enhances the competitive advantage of heliophytic (light-demanding) species and therefore the floristic composition of phytocenoses. Based on charcoal abundance in the soil (used as an indicator of anthropogenic perturbation), species abundance, and environmental data from a forest of south-east Cameroon, we applied modern variation partitioning methods to assess the relative impact of human disturbance on floristic patterns, controlling for purely spatial and habitat effects. Significant signals of human influence have been found so far, and a new collection of data should establish with a better precision the importance of the anthropogenic impact on tree species assemblages. [less ▲]

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See detailLife history traits related to hydraulic functioning in 211 African tropical woody species
Morin-Rivat, Julie ULg; Fayolle, Adeline ULg; Doucet, Jean-Louis ULg et al

Poster (2013, June 06)

In the context of global change understanding the interactions between plant ecology and plant physiology remains a crucial issue. In this study we aimed at analyzing the vascular characteristics involved ... [more ▼]

In the context of global change understanding the interactions between plant ecology and plant physiology remains a crucial issue. In this study we aimed at analyzing the vascular characteristics involved in the ecological traits of woody species from the northern Congo Basin. We crosschecked three databases: the botanical inventories (857 spp.) and the database of life history traits (464 spp.) produced during the CoForChange project, and the anatomical database Inside Wood (761 spp. and genera for tropical Africa). A total of 211 shared species was obtained. We performed correspondence analyses between the tangential diameter of the vessel lumina (40-43), the number of vessels per mm² (46-50) and five life history traits: leaf phenology, light requirement, seed dispersal, tree size and wood density. Species were distributed along a gradient from species with numerous small vessels to species with few large vessels. This distribution was correlated to a gradient in leaf phenology and light requirement: from evergreen shade-tolerant species to deciduous non-pioneer and pioneer light-demanding species. Dispersal followed this distribution in a lesser extent: from zoochoria to autochoria via anemochoria. Finally, a gradient in size was observed, from small shrubs to tall trees, as well as a gradient in wood density, from dense to light woods. We conclude that the ecological traits of the African tropical woody species are closely related to their hydraulic functioning. The strategies adopted by plants regarding light and water availability can thus be deduced from their vascular characteristics. On this basis we anticipate that climate change will foster light-demanding tree species as better competitors than shade-tolerant species, especially as drought stress is concerned. Further research is needed to increase the input of wood anatomy in explaining the life history traits in African tropical species. [less ▲]

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See detailImpacts of logging and hunting on western lowland gorilla (Gorilla gorilla gorilla) populations and consequences for forest regeneration. A review
Haurez, Barbara ULg; Petre, Charles-Albert ULg; Doucet, Jean-Louis ULg

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2013), 17(2), 364-372

Timber exploitation is rapidly expanding throughout the Congo Basin. Forest areas assigned to timber harvesting have sharply expanded over the decades and logging concessions now largely overlap with the ... [more ▼]

Timber exploitation is rapidly expanding throughout the Congo Basin. Forest areas assigned to timber harvesting have sharply expanded over the decades and logging concessions now largely overlap with the range of western lowland gorilla (Gorilla gorilla gorilla Savage & Wyman, 1847). However this species, which is considered as critically endangered by IUCN, could play an essential role in maintaining the structure and composition of tropical rainforest notably through seed dispersal services. This is likely due to its frugivorous diet, high stomach capacity and ability to swallow seeds of variable sizes. Moreover gorillas have a long gut retention time of ingested food, travel long daily distances and deposit most ingested seeds in suitable habitats for plant development (such as logging gaps). Consequently, the preservation of the role of gorilla in forest regeneration is essential in the context of logged forest ecosystems. Timber harvesting has two major opposing impacts on gorilla populations: on the one hand, gorillas benefit from growth of herbaceous vegetation (e.g. Marantaceae and Zingiberaceae) following forest canopy opening, as such herbs provide both staple food and nest-building materials; on the other hand, gorilla populations suffer with the rise in hunting associated with logging activity, especially with road network installation. Considering the potential negative knock-on effects of logging concessions on the ecological function of western lowland gorilla, the implementation of timber harvesting methods that preserve gorilla populations is a considerable challenge for forest sustainability, as well as for gorilla’s conservation. [less ▲]

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See detailSpecies delimitation and diversification in the widespread tree genus Milicia (Moraceae)
Daïnou, Kasso ULg; Mahy, Grégory ULg; Duminil, Jérôme et al

Conference (2013, June)

The long generation time and large effective size of widespread forest tree species can result in slow evolutionary rate and incomplete lineage sorting, complicating species delimitation. We addressed ... [more ▼]

The long generation time and large effective size of widespread forest tree species can result in slow evolutionary rate and incomplete lineage sorting, complicating species delimitation. We addressed this issue with the African timber tree genus Milicia that comprises two morphologically similar and often confounded species: M. excelsa, widespread from West to East Africa, and M. regia, endemic to West Africa. We combined information from nuclear microsatellites (nSSRs), nuclear and plastid DNA sequences, and morphological systematics to identify significant evolutionary units and infer their evolutionary and biogeographical history. We detected five geographically coherent genetic clusters using nSSRs and three levels of genetic differentiation. First, one West African cluster matched perfectly with the morphospecies M. regia, which formed a monophyletic clade at both DNA sequences. Second, a West African M. excelsa cluster formed a monophyletic group at plastid DNA and was more related to M. regia than to Central African M. excelsa, but shared many haplotypes with the latter at nuclear DNA. Third, three Central African clusters appeared little differentiated and shared most of their haplotypes. Although gene tree paraphyly could suggest a single species in Milicia following the Phylogenetic Species Concept, the existence of mutual haplotypic exclusivity and non-admixed genetic clusters in the contact area of the two taxa indicate strong reproductive isolation, and thus, two species following the Biological Species Concept. Molecular dating of the first divergence events showed that speciation in Milicia is ancient (Tertiary), indicating that long-living tree taxa exhibiting genetic speciation may remain similar morphologically. [less ▲]

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See detailEcological wood anatomy of 155 African tropical hardwoods
Beeckman, Hans; Fayolle, Adeline ULg; Doucet, Jean-Louis ULg et al

Conference (2013, April 19)

In this study we aimed at identifying the anatomical characters expressing life history traits of woody species from the northern Congo Basin. We crosschecked three databases: the botanical inventories ... [more ▼]

In this study we aimed at identifying the anatomical characters expressing life history traits of woody species from the northern Congo Basin. We crosschecked three databases: the botanical inventories produced during the CoForChange project (857 spp.), the database of life history traits established by the CIRAD (France) and GxABT (Belgium) (464 spp.), and the anatomical database Inside Wood (761 spp. and genera for tropical Africa). A total of 155 shared species was obtained. We performed correspondence analyses between the anatomical characters and two main groups of traits: leaf phenology and light-requirement. Results showed: (i) that wood anatomy is involved in leaf phenology and light-requirement in a significant way (7.56% of the variance on axe1), (ii) that evergreenness was correlated to IAWA characters 14 to 18 (scalariform perforation plates, e.g. Olacaceae) and deciduousness to characters 118 to 122 (storied structures, e.g. Malvaceae and Meliaceae), (iii) that pioneer (P) and non-pioneer light-demanding (NPLD) species showed similar traits but were different from shade-tolerant (ST) species, (iv) that deciduous and evergreen species showed separate distributions, and (v) that wood anatomy validated the well documented strong correlation between evergreen species and ST species, with an inversion of the tendency for deciduous species correlated to P and NPLD species. We conclude that anatomical characters can be used as indicators of life history traits in species-rich biomes. Further investigations are needed to increase the input of wood anatomy in explaining the life history traits in African tropical species. [less ▲]

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See detailWestern lowland gorilla populations and logging concessions: is the coexistence possible?
Haurez, Barbara ULg; Petre, Charles-Albert ULg; Doucet, Jean-Louis ULg

Conference (2013, April)

Timber exploitation is rapidly expanding throughout the Congo Basin. Around 26 % of the moist forests are devoted to logging activities. Logging concessions largely overlap with the range of western ... [more ▼]

Timber exploitation is rapidly expanding throughout the Congo Basin. Around 26 % of the moist forests are devoted to logging activities. Logging concessions largely overlap with the range of western lowland gorilla (WLG) considered as critically endangered by IUCN. However, this species could play an essential role in maintaining vegetal diversity notably through seed dispersal services. Particularly some tree species harvested for their timber may be dispersed by WLG. In this communication interactions between WLG and a timber exploitation are studied in Central Gabon. WLG density is estimated in an Annual Allowable Cut (AAC), and nesting behavior is described. Seeds dispersed by WLG are identified through fecal analysis and germination trials are conducted to assess seed viability after gut passage. Four treatments are realized for the most abundant species: passed seeds, passed seeds in fecal matrix, seeds surrounded by fresh pulp and seeds extracted from fresh fruits. A relatively high WLG density is observed in the AAC (2.0 weaned gorillas/km²). WLG nest preferentially in open terra firme forest and frequently use old logging road covered with herbaceous vegetation for nesting and feeding. They avoid nesting in closed terra firme forest. Seed dispersal and impacts of the passage in gorilla’s gut on seed germination are currently described. Germination success after gut passage depends on the seed species and varies from 0.0 to 100% in the course of monitoring time. The first results of this study suggest that timber exploitation and WLG conservation are not mutually exclusive. WLG are important agents of forest regeneration by dispersing seeds in logged areas. Nest sites in logging gaps could be particularly favorable for seedlings development. This consideration must encourage forest managers to strengthen WLG-conservative practices in their concessions. [less ▲]

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See detailLes forêts communautaires, c'est aussi une histoire de femmes
Meunier, Quentin; Boldrini, Sylvie ULg; Morin, Amélie et al

Learning material (2013)

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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 detailRelation entre composition floristique et accumulation de biomasse dans deux types de forêts de la Réserve de Biosphère du Dja (Cameroun)
Djuikouo, Marie Noel K.; Doucet, Jean-Louis ULg; Nguembou, Charlemagne K. et al

Poster (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 detailLettre d’information trimestrielle du projet Développement d’Alternatives Communautaires à l’Exploitation Forestière Illégale
Boldrini, Sylvie; Moumbogou; Meunier, Quentin et al

E-print/Working paper (2013)

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