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See detailSentiers de suivi de la croissance, de la mortalité et de la phénologie des arbres tropicaux : Guide méthodologique
Tosso, Dji-ndé Félicien ULiege; Daïnou, Kasso ULiege; Sonké, Bonaventure et al

Book published by Presses Universitaires de Liège (2020)

La durabilité de l’aménagement des forêts naturelles d’Afrique centrale est tributaire d’une connaissance approfondie de la dynamique démographique des populations d’arbres commerciaux. Cette dynamique ... [more ▼]

La durabilité de l’aménagement des forêts naturelles d’Afrique centrale est tributaire d’une connaissance approfondie de la dynamique démographique des populations d’arbres commerciaux. Cette dynamique est étudiée dans des dispositifs destinés à être suivis sur le long terme, dénommés parcelles et sentiers. Si la démarche méthodologique d’installation et de suivi des parcelles est assez bien documentée, celle des sentiers l’est moins. Le présent ouvrage vient combler ce vide en capitalisant l’expérience accumulée depuis plus de 20 ans par les membres du collectif DYNAFAC, un collectif créé à l’initiative de l’ATIBT, du CIRAD, de Nature+ et de Gembloux Agro-Bio Tech. Il s’agit d’un guide pratique et illustré explicitant la démarche nécessaire à l’installation et au suivi de ces sentiers. Outre les procédures techniques, le guide évalue également les coûts en tenant compte des spécificités économiques de différents pays de la sous-région. En s’adressant à l’ensemble des parties prenantes de l’aménagement et de la gestion des forêts d’Afrique, l’ouvrage a pour ambition de promouvoir la mise en œuvre de dispositifs robustes et efficients à la portée de tous. [less ▲]

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See detailRevisiting the North-South genetic discontinuity in Central African tree populations: the case of the low-density tree species Baillonella toxisperma
Ndiade-Bourobou, Dyana; Daïnou, Kasso ULiege; Hardy, Olivier J. et al

in Tree Genetics and Genomes (2020), 16(15),

How the Central African rain forests have been affected by climatic fluctuations of the Quaternary remains debated. Phylogeographical studies have shown that tree species from western Central Africa often ... [more ▼]

How the Central African rain forests have been affected by climatic fluctuations of the Quaternary remains debated. Phylogeographical studies have shown that tree species from western Central Africa often display spatially congruent genetic discontinuities, supporting the hypothesis that the forest was previously fragmented. Extensive seed dispersal is expected to accelerate the admixture between gene pools but most of the species studied so far have presumably limited seed dispersal abilities. Here, we genotyped 15 nuclear and three plastid microsatellite markers in a low-density Central African tree species with long-distance seed dispersal: Baillonella toxisperma (Sapotaceae). While plastid markers revealed a weak structure in Cameroon, nuclear markers highlighted three genetic clusters: two distributed in Cameroon and separating Atlantic coastal forests from the inland forests, and one cluster occurring in Gabon. Substantial genetic differentiation with a phylogeographical signal was detected only between Cameroonian and Gabonese populations, suggesting two major genetic clusters located approximately North and South of the equatorial climatic hinge. Genetic differentiation was very low between the clusters within Cameroon. This pattern could be partially explained by the climate niche distribution modelling applied on the Last Glacial Maximum (LGM) which predicts a unique remnant population per country. The deep North-South differentiation in a species with long-distance seed dispersal supports the hypothesis that Central African rain forests have been fragmented at the height of the equator during a substantial part of the Quaternary. [less ▲]

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See detailPopulation genomics of the widespread African savannah trees Afzelia africana and Afzelia quanzensis reveals no significant past fragmentation of their distribution ranges
Donkpegan, Armel S. L. ULiege; Piñeiro, Rosalía; Heuertz, Myriam et al

in American Journal of Botany (2020), 107(3), 498-509

PREMISE: Few studies have addressed the evolutionary history of tree species from African savannahs. Afzelia contains economically important timber species, including two species widely distributed in ... [more ▼]

PREMISE: Few studies have addressed the evolutionary history of tree species from African savannahs. Afzelia contains economically important timber species, including two species widely distributed in African savannahs: A. africana in the Sudanian region and A. quanzensis in the Zambezian region. We aimed to infer whether these species underwent range fragmentation and/or demographic changes, possibly reflecting how savannahs responded to Quaternary climate changes. METHODS: We characterized the genetic diversity and structure of these species across their distribution ranges using nuclear microsatellites (SSRs) and genotyping-by-sequencing (GBS) markers. Six SSR loci were genotyped in 241 A. africana and 113 A. quanzensis individuals, while 2800 high-quality single nucleotide polymorphisms (SNPs) were identified in 30 A. africana individuals. RESULTS: Both species appeared to be mainly outcrossing. The kinship between individuals decayed with the logarithm of the distance at similar rates across species and markers, leading to relatively small Sp statistics (0.0056 for SSR and 0.0054 for SNP in A. africana, 0.0075 for SSR in A. quanzensis). The patterns were consistent with isolation by distance expectations in the absence of large-scale geographic gradients. Bayesian clustering of SSR genotypes did not detect genetic clusters within species. In contrast, SNP data resolved intraspecific genetic clusters in A. africana, illustrating the higher resolving power of GBS. However, these clusters revealed low levels of differentiation and no clear geographical entities, so that they were interpreted as resulting from the isolation by distance pattern rather than from past population fragmentation. CONCLUSIONS: These results suggest that populations have remained connected throughout the large, continuous savannah landscapes. The absence of clear phylogeographic discontinuities, also found in a few other African savannah trees, indicates that their distribution ranges have not been significantly fragmented during the climatic oscillations of the Pleistocene, in contrast to patterns commonly found in African rainforest trees. [less ▲]

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See detailConservation value of tropical forests: Distance to human settlements matters more than management in Central Africa
Lhoest, Simon ULiege; Fonteyn, Davy ULiege; Daïnou, Kasso ULiege et al

in Biological Conservation (2020), 241(108351),

Tropical forests in Central Africa host unique biodiversity threatened by human degradation of habitats and defaunation. Forests allocated to conservation, production and community management are expected ... [more ▼]

Tropical forests in Central Africa host unique biodiversity threatened by human degradation of habitats and defaunation. Forests allocated to conservation, production and community management are expected to have different conservation values. Here, we aimed to identify the determinants of the conservation value of tropical forests in southeastern Cameroon, by disentangling the effects of forest allocations, proximity to human settlements, and local habitat. We inventoried two taxonomical groups: mammal species with camera traps (3464 independent detection events) and dung beetle species with pitfall traps (4475 individuals). We used an integrated analytical approach, examining both species richness and composition. For both mammals and dung beetles, species richness decreased from the protected area to the community forests, and the logging concession showed intermediate richness. Species richness of both groups was negatively correlated to the proximity to human settlements and disturbance, with a decreasing gradient of body mass and the loss of the most threatened species. The replacement (i.e., spatial turnover) of both mammal and dung beetle species among forest allocations suggest an integration of conservation initiatives to a large number of different sites, with a priority on protected and remote areas of high biodiversity. These results confirm the high conservation value of protected areas and their essential role in conservation strategies, ecologically connected with well-managed production forests with variable conservation value mainly depending on accessibility. Community forests located close to villages are much more degraded but not totally defaunated and still provide bushmeat to local populations. © 2019 Elsevier Ltd [less ▲]

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See detailSpecies delimitation in the African tree genus Lophira (Ochnaceae) reveals cryptic genetic variation
Ewédjè, Eben-Ezer Baba Kayode; Jansen, Simon; Koffi, Guillaume Kouame et al

in Conservation Genetics (2020), 21

Species delimitation remains a crucial issue for widespread plants occurring across forest-savanna ecotone such as Lophira (Ochnaceae). Most taxonomists recognize two parapatric African tree species ... [more ▼]

Species delimitation remains a crucial issue for widespread plants occurring across forest-savanna ecotone such as Lophira (Ochnaceae). Most taxonomists recognize two parapatric African tree species, widely distributed and morphologically similar but occurring in contrasted habitats: L. lanceolata in the Sudanian dry forests and savannahs and L. alata in the dense Guineo- Congolian forests. Both species co-occur along a ca. 3000 km long forest-savanna mosaic belt, constituting ideal models for investigating hybridization patterns and the impact of past glacial periods on the genetic structures in two types of ecosystems. We genotyped 10 nuclear microsatellites for 803 individuals sampled across the distribution range of Lophira. Both species exhibit similar levels of genetic diversity [He = 0.52 (L. alata); 0.44 (L. lanceolata)] and are well differentiated, consistent with taxonomic delimitation (FST = 0.36; RST = 0.49), refuting the hypothesis that they might constitute ecotypes rather than distinct species. Furthermore, L. alata displayed two deeply differentiated clusters (FST = 0.37; RST = 0.53) distributed in parapatry, one endemic to Western Gabon while another cluster extended over the remaining species range, suggests that L. alata is made of two cryptic species. We showed that rare hybrids occur in some contact zones between these three species, leaving a weak signal of introgression between L. lanceolata and the northern cluster of L. alata. At the intra-specific level, the latter species also show weak genetic structuring between Upper and Lower Guinea and the intensity did not differ strikingly between rainforest and savanna ecosystems. The discovery of a new species of Lophira with a narrow distribution in West Gabon where it is intensively exploited for its timber requires to evaluate its conservation status. [less ▲]

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See detailCylicodiscus gabunensis Harms : une espèce prisée dans le commerce international (synthèse bibliographique)
Ndonda Makemba, Romaric ULiege; Tosso, Dji-ndé Félicien ULiege; Moupela, Christian et al

in Biotechnologie, Agronomie, Société et Environnement (2019), 23(3), 188-202

Introduction. En raison de la diminution des ressources en bois d’oeuvre tropicaux, il convient d’améliorer les connaissances sur les espèces ligneuses en vue de développer des politiques d’exploitation ... [more ▼]

Introduction. En raison de la diminution des ressources en bois d’oeuvre tropicaux, il convient d’améliorer les connaissances sur les espèces ligneuses en vue de développer des politiques d’exploitation réellement durables. Reconnu pour la grande qualité de son bois, Cylicodiscus gabunensis Harms (Fabaceae-Caesalpinioideae) est une essence à haute valeur socio-économique. Cet article dresse la synthèse bibliographique des connaissances relatives à cette espèce en vue de mettre en avant l’ensemble des aspects méritant des investigations scientifiques approfondies. Littérature. Commercialisée sous le nom d’okan, C. gabunensis est une espèce ligneuse non grégaire vivant dans les forêts denses humides tropicales sempervirentes et semi-décidues. Arbre fétiche pour certains peuples autochtones, C. gabunensis est utilisé par les communautés rurales pour de multiples usages. C’est une espèce à phénologie régulière avec une dispersion anémochore des graines. Les populations d’arbres affichent un déficit de régénération en forêt dense humide sempervirente, ce qui compromettrait l’exploitation de l’espèce à long terme. Ce risque est accru par le manque évident d’informations écologiques et sylvicoles permettant une gestion durable. Conclusions. Cette revue bibliographique résume l’ensemble des informations disponibles sur C. gabunensis principalement en botanique, anatomie du bois, écologie et ethnobotanique. Elle renseigne sur l’état actuel des connaissances au regard des rythmes d’exploitation et de l’état des populations de l’espèce. Des informations complémentaires sont nécessaires pour (i) statuer sur la conservation des populations de l’espèce et (ii) proposer des stratégies de gestion adaptées. [less ▲]

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See detailA few north Appalachian populations are the source of European black locust
Bouteiller, Xavier; Verdu, Cindy ULiege; Aikio, E et al

in Ecology and Evolution (2019), 9(5), 2398-2414

The role of evolution in biological invasion studies is often overlooked. In order to evaluate the evolutionary mechanisms behind invasiveness, it is crucial to identify the source populations of the ... [more ▼]

The role of evolution in biological invasion studies is often overlooked. In order to evaluate the evolutionary mechanisms behind invasiveness, it is crucial to identify the source populations of the introduction. Studies in population genetics were carried out on Robinia pseudoacacia L., a North American tree which is now one of the worst invasive tree species in Europe. We realized large-scale sampling in both the invasive and native ranges: 63 populations were sampled and 818 individuals were genotyped using 113 SNPs. We identified clonal genotypes in each population and analyzed between and within range population structure, and then, we compared genetic diversity between ranges, enlarging the number of SNPs to mitigate the ascertainment bias. First, we demonstrated that European black locust was introduced from just a limited number of populations located in the Appalachian Mountains, which is in agreement with the historical documents briefly reviewed in this study. Within America, population structure reflected the effects of long-term processes, whereas in Europe it was largely impacted by human activities. Second, we showed that there is a genetic bottleneck between the ranges with a decrease in allelic richness and total number of alleles in Europe. Lastly, we found more clonality within European populations. Black locust became invasive in Europe despite being introduced from a reduced part of its native distribution. Our results suggest that human activity, such as breeding programs in Europe and the seed trade throughout the introduced range, had a major role in promoting invasion; therefore, the introduction of the missing American genetic cluster to Europe should be avoided. © 2019 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd. [less ▲]

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See detailConservation value of protected and logged tropical forests in Cameroon
Lhoest, Simon ULiege; Fonteyn, Davy ULiege; Daïnou, Kasso ULiege et al

Scientific conference (2019, January 25)

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See detailHighlighting convergent evolution in morphological traits in response to climatic gradient in African tropical tree species: The case of genus Guibourtia Benn.
Tosso, Dji-ndé Félicien ULiege; Doucet, Jean-Louis ULiege; Daïnou, Kasso ULiege et al

in Ecology and Evolution (2019)

Adaptive evolution is a major driver of organism diversification, but the links between phenotypic traits and environmental niche remain little documented in tropical trees. Moreover, trait-niche ... [more ▼]

Adaptive evolution is a major driver of organism diversification, but the links between phenotypic traits and environmental niche remain little documented in tropical trees. Moreover, trait-niche relationships are complex because a correlation between the traits and environmental niches displayed by a sample of species may result from (a) convergent evolution if different environmental conditions have selected different sets of traits, and/or (b) phylogenetic inertia if niche and morphological differences between species are simply function of their phylogenetic divergence, in which case the trait-niche correlation does not imply any direct causal link. Here, we aim to assess the respective roles of phylogenetic inertia and convergent evolution in shaping the differences of botanical traits and environmental niches among congeneric African tree species that evolved in different biomes. This issue was addressed with the tree genus Guibourtia Benn. (Leguminosae and Detarioideae), which contains 13 African species occupying various forest habitat types, from rain forest to dry woodlands, with different climate and soil conditions. To this end, we combined morphological data with ecological niche modelling and used a highly resolved plastid phylogeny of the 13 African Guibourtia species. First, we demonstrated phylogenetic signals in both morphological traits (Mantel test between phylogenetic and morphological distances between species: r =.24, p =.031) and environmental niches (Mantel test between phylogenetic and niche distances between species: r =.23, p =.025). Second, we found a significant correlation between morphology and niche, at least between some of their respective dimensions (Mantel's r =.32, p =.013), even after accounting for phylogenetic inertia (Phylogenetic Independent Contrast: r =.69, p =.018). This correlation occurred between some leaflet and flower traits and solar radiation, relative humidity, precipitations, and temperature range. Our results demonstrate the convergent evolution of some morphological traits in response to climatic factors in congeneric tree species and highlight the action of selective forces, along with neutral ones, in shaping the divergence between congeneric tropical plants. © 2019 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd. [less ▲]

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See detailTesting the divergent adaptation of two congeneric tree species on a rainfall gradient using eco-physio-morphological traits
Gorel, Anaïs ULiege; Steppe, Kathy; Beeckman, Hans et al

in Biotropica (2019)

In tropical Africa, evidence of widely distributed genera transcending biomes or habitat boundaries has been reported. The evolutionary processes that allowed these lineages to disperse and adapt into new ... [more ▼]

In tropical Africa, evidence of widely distributed genera transcending biomes or habitat boundaries has been reported. The evolutionary processes that allowed these lineages to disperse and adapt into new environments are far from being resolved. To better understand these processes, we propose an integrated approach, based on the eco-physio-morphological traits of two sister species with adjacent distributions along a rainfall gradient. We used wood anatomical traits, plant hydraulics (vulnerability to cavitation, wood volumetric water content and hydraulic capacitance) and growth data from the natural habitat, in a common garden, to compare species with known phylogeny, very similar morphologically, but occupying contrasting habitats: Erythrophleum ivorense (wet forest) and Erythrophleum suaveolens (moist forest and forest gallery). We identified some slight differences in wood anatomical traits between the two species associated with strong differences in hydraulics, growth, and overall species distribution. The moist forest species, E. suaveolens had narrower vessels and intervessel pits, and higher vessel cell-wall reinforcement than E. ivorense. These traits allow a high resistance to cavitation and a continuous internal water supply of the xylem during water shortage, allowing a higher fitness during drought periods, but limiting growth. Our results confirm a trade-off between drought tolerance and growth, controlled by subtle adaptations in wood traits, as a key mechanism leading to the niche partitioning between the two Erythrophleum species. The generality of this trade-off and its importance in the diversification of the African tree flora remains to be tested. Our integrated eco-physio-morpho approach could be the way forward. [less ▲]

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See detailGrowth determinants of timber species Triplochiton scleroxylon and implications for forest management in central Africa
Ligot, Gauthier ULiege; Fayolle, Adeline ULiege; Gourlet-Fleury, Sylvie et al

in Forest Ecology and Management (2019), 437

The sustainability of the polycyclic logging system in tropical forests has been increasingly questioned for a variety of reasons, and particularly in central Africa as commercial species, mostly light ... [more ▼]

The sustainability of the polycyclic logging system in tropical forests has been increasingly questioned for a variety of reasons, and particularly in central Africa as commercial species, mostly light-demanding long-lived pioneer species, usually fail to recover a stable number of large trees after exploitation. Several factors are known to affect tropical tree demographic processes, like tree growth, survival and recruitment. Tree growth has particularly been showed to depend on ecological conditions, tree genetics, and competition with surrounding vegetation, as well as tree size or ontogeny. Yet, due to the paucity of available data, the importance of such factors is unclear and usually ignored when estimating future timber yields. To fill this gap, we chose to evaluate the variability in growth of one African long-lived pioneer and commercially very important species: Triplochiton scleroxylon K. Schum, gathering a broad dataset composed of tree ring data recorded in one site in Cameroon and periodic field inventory data recorded in seven sites across central Africa. In total, we analyzed 13,225 records of annual tree diameter increments recorded over 920 trees from seven sites in Cameroon, Republic of the Congo and Central African Republic. We evaluated (i) to what extent the average growth of trees that reach harvestable dimensions differs from population average and (ii) to what extent past perturbations influence the growth of remaining trees. We found the diameter growth of T. scleroxylon to be remarkably variable and this study provided an unprecedented quantification of the magnitude of some key growth determinants. In unlogged forests, the diameter increment of T. scleroxylon ranged between 0.40 cm year-1 in Southern Cameroon and 0.83 cm year-1 in South-Eastern Cameroon. The diameter increment was weakly related to tree size but increased twofold from unlogged to logged forests. Perturbation caused by logging stimulates growth of T. scleroxylon for at least 10-15 years. Finally, harvestable timber stock of large-sized T. scleroxylon was found to be constituted by trees that grew in average twice faster than trees of the entire extant population. As more and more inventory data become available, quantifying these effects could be replicated for other timber species and in other sites, to improve the accuracy of future timber resource estimates and improve forest management guidelines. [less ▲]

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See detailBanque de graines du sol et déterminants de la germination du tali, Erythrophleum suaveolens (Guill. & Perr.) Brenan
Douh, Chauvelin ULiege; Gorel, Anaïs ULiege; Daïnou, Kasso ULiege et al

in Bois et Forêts des Tropiques (2018), 338

Cette étude évalue l’abondance des graines d’Erythrophleum suaveolens dans la banque du sol des forêts denses humides d’Afrique centrale. Les travaux ont été menés au Nord-Congo dans deux types forestiers ... [more ▼]

Cette étude évalue l’abondance des graines d’Erythrophleum suaveolens dans la banque du sol des forêts denses humides d’Afrique centrale. Les travaux ont été menés au Nord-Congo dans deux types forestiers : la forêt à Celtis sur des sols argilo-sableux à sablo-argileux et la forêt à Manilkara sur des sols sableux. Les tiges d’E. suaveolens (dhp ≥ 10 cm) ont été inventoriées dans deux parcelles de 400 ha, et les structures diamétriques de leurs populations ont été comparées. En outre, 80 fosses (2 x 40 fosses par type de forêt) ont été creusées aux pieds de 20 arbres (10 par forêt), sur trois couches contiguës de 10 cm chacune, soit à une profondeur totale de 30 cm, et l’abondance des graines dans la banque du sol a été évaluée. La dormance des graines récoltées a été testée par des essais de germination après traitement au H2SO4 et cinq graines prélevées jusqu’à une profondeur de 20 cm dans la forêt à Celtis ont été utilisées pour estimer leur âge par Spectroscopie de Masse par Accélérateur (SMA). La comparaison des structures diamétriques indique une plus grande proportion de tiges de faible diamètre dans la forêt à Celtis. Alors que les densités de tiges (dhp ≥ 10 cm) sont proches, avec 0,85 et 1,05 tige/ha respectivement, dans la forêt à Celtis et la forêt à Manilkara, les densités de graines sont significativement plus élevées dans la forêt à Celtis (8,55 graines/m2) que dans la forêt à Manilkara (0,15 graine/m2). Le pourcentage maximum de germination obtenu était de 19,1 % pour des graines n’ayant subi aucun traitement. Les lots traités à l’acide ont présenté de moindres taux de germination. Ces graines pourraient se conserver une dizaine d’années dans la banque du sol. Les facteurs pouvant influencer les variations de densité des graines sont discutés et des recommandations sylvicoles sont formulées. [less ▲]

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See detailGorilla @ work! Why should loggers take care of their gorillas?
Haurez, Barbara ULiege; Petre, Charles-Albert; Vermeulen, Cédric ULiege et al

Scientific conference (2018, November 05)

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See detailSoil seed bank characteristics in two central African forest types and implications for forest restoration
Douh, Chauvelin ULiege; Daïnou, Kasso ULiege; Joël Loumeto, J. et al

in Forest Ecology and Management (2018), 409

This study evaluates the characteristics of soil seed bank in two types of central African rainforests: Celtis forest on clay soils and Manilkara forest on sandy soils. In each study site, 30 samples were ... [more ▼]

This study evaluates the characteristics of soil seed bank in two types of central African rainforests: Celtis forest on clay soils and Manilkara forest on sandy soils. In each study site, 30 samples were collected per soil layers (litter, 0–5 cm, 5–10 cm and 10–20 cm depth). The species diversity and abundance of the soil seed bank were estimated after soil samples were brought to germination. We globally observed 297 seedlings of 53 species for the Celtis forest and 222 seedlings of 39 species for the Manilkara forest. The total densities of germinated seeds were 330 seedlings m−2 and 247 seedlings m−2, respectively. Herbaceous species dominated with percentages of 41.0 and 45.3%, respectively in the Manilkara forest and the Celtis forest. Both forest types displayed a regeneration potential through the soil seed bank. However, this potential seems higher in the Celtis forest. Pioneer taxa were more abundant in the soil seed bank of the Celtis forest (13 woody pioneer species) than the Manilkara forest (9 woody pioneer species). The values of Sorensen similarity index between the standing tree vegetation and the soil seed bank in each site were relatively low: 11.0% for the Celtis forest and 8.8% for the Manilkara forest. But these similarity values were higher when only the pioneer species were considered: 46.8% in the Celtis forest and 38.9% in the Manilkara forest. The highest species richness were obtained in the first two soil layers (0–10 cm depth) while 21.8% and 21.4% of the species were exclusively found in the deepest layer (10–20 cm) in the Celtis forest and the Manilkara forest, respectively. Among the timber species found in the forest, only three were observed in the soil seed bank of the two sites: Nauclea diderrichii, Erythrophleum suaveolens and Staudtia kamerunensis. N. diderrichii was particularly abundant in the soil seed stock of the two sites (14.4–34.4 seeds m−2). Results suggested that to improve regeneration of timber species, planting in open forest habitats with seedlings coming from tree nursery should be more efficient. © 2017 Elsevier B.V. [less ▲]

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See detailThe size at reproduction of canopy tree species in central Africa
Ouedraogo, Dakis-Yaoba ULiege; Doucet, Jean-Louis ULiege; Daïnou, Kasso ULiege et al

in Biotropica (2018), 50(3), 465-476

Size at reproduction is a key aspect of species life history that is relatively understudied for long-lived tropical trees. Here, we quantified reproductive diameter for 31 major timber species across 11 ... [more ▼]

Size at reproduction is a key aspect of species life history that is relatively understudied for long-lived tropical trees. Here, we quantified reproductive diameter for 31 major timber species across 11 sites in Cameroon, Congo, and Central African Republic. Specifically, we examined whether (1) between-species variability is correlated with other species traits; (2) reproductive diameter varies within-species among sites; (3) reproductive status varies with crown exposure; and (4) the minimum cutting diameter limits (MCDL) imposed by national forest regulations enable seed trees to persist after logging operations. Consistent with studies conducted elsewhere in the tropics, we found great variability in diameter at reproduction among species, which correlated with adult stature (maximum diameter and height). For some species, reproductive diameter thresholds substantially varied between sites, and crown exposure had a significant positive effect on reproductive status. Most MCDLs were found to be suitable, with trees having a high probability of being seed trees at MCDL. Our findings have implications for the sustainable management of production forests, and they highlight questionable MCDLs for some species and between-site variation in reproductive diameter. The study also highlights the need for long-term phenological monitoring of tree species spanning a large range of ecological strategies to address both theoretical (species life history, allocation tradeoffs) and practical questions (MCDL). [less ▲]

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See detailProjet Flux de gènes. Aide à l'application des normes d’aménagement et de certification sur la régénération et la diversité génétique des essences du bassin du Congo.
Daïnou, Kasso ULiege; Donkpegan Segbedji, Armel Loïc; Doucet, Jean-Louis ULiege et al

Conference given outside the academic context (2017)

Contexte • Peu de connaissances sur l’écologie des essences commerciales, dont les processus intervenant dans la régénération • Très peu d’informations sur l’impact de l’exploitation forestière sur la ... [more ▼]

Contexte • Peu de connaissances sur l’écologie des essences commerciales, dont les processus intervenant dans la régénération • Très peu d’informations sur l’impact de l’exploitation forestière sur la régénération des essences commerciales Or exigences croissantes, notamment : • Normes de gestion durable des forêts de production, dont la circulaire 0086 relative à la sylviculture • Normes de certification, dont le critère FSC 6.3 relatif à la régénération et au maintien de la diversité génétique Objectifs : Mieux comprendre les processus en amont de la régénération et proposer des normes d’exploitation considérant la diversité génétique 1. Estimer les distances de dispersion du pollen et des graines, par des outils de biologie moléculaire (tests de parenté et de paternité) 2. Etudier l’effet de l’isolement spatial sur le succès reproducteur, par l’évaluation des niveaux de consanguinité et d’autofécondation, l’écologie classique [less ▲]

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See detailDevelopment of nuclear SNP markers for genetic tracking of Iroko, Milicia excelsa and Milicia regia
Blanc-Jolivet, Céline; Kersten, Birgit; Daïnou, Kasso ULiege et al

in Conservation Genetics Resources (2017)

Iroko, Milicia excelsa, is an economically important tropical hardwood species widely distributed in tropical Africa, from Ivory Coast in Western Africa to Tanzania in Eastern Africa. The species occurs ... [more ▼]

Iroko, Milicia excelsa, is an economically important tropical hardwood species widely distributed in tropical Africa, from Ivory Coast in Western Africa to Tanzania in Eastern Africa. The species occurs at low densities in contrasting habitats such as rainforest and woodlands. Former studies using chloroplast and nuclear sequences, as well as nSSRs, revealed a strong differentiation within the species among West and Central African populations and the presence of three genetic groups in Central Africa (Daïnou et al. 2010, 2014). The genus Milicia also includes another species, M. regia, co-occurring with M. excelsa in West Africa. Both species can be identified genetically and morphologically (Daïnou et al. 2014), but identification is difficult in the field. Although the spatial genetic structure of the species is well described, it is mostly based on nSSRs. Despite their lower diversity, SNP markers provide several advantages including the uncomplicated standardization of data among laboratories and the easy, rapid and low-cost development of markers for large sets of loci. These features make SNPs the ideal markers for setting up genetic reference data for timber tracking (Blanc-Jolivet and Liesebach 2015; Degen et al. 2017; Jardine et al. 2016; Pakull et al. 2016). In this paper, we describe the development of a new set of nuclear SNPs on M. excelsa meant to be used for genetic timber tracking. [less ▲]

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See detailEntandrophragma cylindricum (Sprague) Sprague (Meliaceae), une espèce ligneuse concurrentielle en Afrique centrale (synthèse bibliographique)
Tabi Eckebil, Paule ULiege; Verheggen, François ULiege; Doucet, Jean-Louis ULiege et al

in Biotechnologie, Agronomie, Société et Environnement (2017), 21(1), 80-97

Introduction. De nos jours, la gestion des ressources forestières ne se focalise plus sur l’exploitation exclusive du bois d’oeuvre, mais prend également en considération les produits forestiers non ... [more ▼]

Introduction. De nos jours, la gestion des ressources forestières ne se focalise plus sur l’exploitation exclusive du bois d’oeuvre, mais prend également en considération les produits forestiers non ligneux. Entandrophragma cylindricum (Sprague) Sprague, de son nom commercial « sapelli/sapele », de la famille des Meliaceae, illustre parfaitement cette situation. Le présent article fait un état de l’art des connaissances concernant E. cylindricum et présente quelques informations sur la chenille qui lui est inféodée. Littérature. Le sapelli est une des espèces ligneuses les plus exploitées d’Afrique centrale pour son bois d’oeuvre. Il est répandu dans la forêt dense humide semi-caducifoliée du domaine guinéo-congolais. C’est une espèce semi-héliophile, son mode de dispersion est anémochore et sa phénologie est régulière. Selon la sylviculture appliquée, sa croissance en diamètre peut atteindre jusque 0,82 cm par an. Cette essence est également l’hôte d’une espèce de chenille comestible riche en protéines, I. oyemensis Rougeot. Fortement appréciée par les populations locales, cette chenille fait également l’objet d’un commerce régional et international. Enfin, l’écorce du sapelli est reconnue pour son intérêt ethnobotanique, particulièrement en médecine traditionnelle. Conclusions. Les informations tirées de la littérature ont permis de mettre en évidence certaines lacunes relatives à l’écologie et au mode de reproduction de cette espèce et, ceci, en dépit de son importance pour le commerce du bois. De plus, les inconnues quant à la productivité et la saisonnalité des chenilles d’Imbrasia oyemensis sur cet arbre nécessitent de développer des recherches complémentaires pour garantir la durabilité de l’exploitation simultanée de la ressource ligneuse et non ligneuse et pour proposer des modes de gestion concertés entre exploitants industriels et populations locales. [less ▲]

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See detailA look at Intact Forest Landscapes and their relevance to Central African forest policy
Haurez, Barbara ULiege; Daïnou, Kasso ULiege; Vermeulen, Cédric ULiege et al

Conference (2017, February)

Tropical forests are important providers of natural resources and ecosystem services but their ecological functions are facing increasing human pressure, linked to economic development. The preservation ... [more ▼]

Tropical forests are important providers of natural resources and ecosystem services but their ecological functions are facing increasing human pressure, linked to economic development. The preservation of tropical forest ecosystems is interrelated with effective land use planning and identification of priority areas for conservation. Initially defined by Greenpeace and the World Resources Institute (WRI) in 2000, Intact Forest Landscapes (IFLs) are large areas of forest minimally impacted by human activities. IFLs were identified by mapping industrial activities, road networks and infrastructure using remote sensing. Since 2014, when IFLs were recognized and adopted by the certification scheme Forest Stewardship Council (FSC), the IFLs have become integrated into forest management policies. In order to trace the history and evaluate the applicability of IFLs for forest management policy in the Central African context, we searched for documents related to the IFL method, and previous similar concepts. The IFL method is simple and cost-effective and enables the monitoring of forest degradation at a global scale. However, the approach mainly considers forest cover and is imprecise at the local scale. For example, hunting, one of the main threats faced by Central African ecosystems, cannot be detected by satellite imagery and is therefore disregarded in IFL identification processes. In contrast, there are other considered anthropogenic activities, such as reduced-impact selective logging, which may be compatible with forest ecosystem conservation. To better tailor the IFL approach to Central African forests, we recommend (i) the consideration of wildlife communities distribution in the analysis of disturbance, (ii) a thorough evaluation of the impacts of different human activities on forest ecosystems, and (iii) the integration of local stakeholders and governments in the design of land management strategies devised to address social, economic and environmental needs. [less ▲]

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