Publications of Jean-Louis Doucet
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See detailOld growth Afrotropical forests critical for maintaining forest carbon
Poulsen, J. R.; Medjibe, V. P.; White, L. J. T. et al

in Global Ecology and Biogeography (in press)

Aim: Large trees [≥ 70 cm diameter at breast height (DBH)] contribute disproportionately to aboveground carbon stock (AGC) across the tropics but may be vulnerable to changing climate and human activities ... [more ▼]

Aim: Large trees [≥ 70 cm diameter at breast height (DBH)] contribute disproportionately to aboveground carbon stock (AGC) across the tropics but may be vulnerable to changing climate and human activities. Here we determine the distribution, drivers and threats to large trees and high carbon forest. Location: Central Africa. Time period: Current. Major taxa studied: Trees. Methods: Using Gabon's new National Resource Inventory of 104 field sites, AGC was calculated from 67,466 trees from 578 species and 97 genera. Power and Michaelis–Menten models assessed the contribution of large trees to AGC. Environmental and anthropogenic drivers of AGC, large trees, and stand variables were modelled using Akaike’s information criterion (AIC) weights to calculate average regression coefficients for all p. ossible models. Results: Mean AGC for trees ≥ 10 cm DBH in Gabonese forestlands was 141.7 Mg C/ha, with averages of 166.6, 171.3 and 96.6 Mg C/ha in old growth, concession and secondary forest. High carbon forests occurred where large trees are most abundant: 31% of AGC was stored in large trees (2.3% of all stems). Human activities largely drove variation in AGC and large trees, but climate and edaphic conditions also determined stand variables (basal area, tree height, wood density, stem density). AGC and large trees increased with distance from human settlements; AGC was 40% lower in secondary than primary and concession forests and 33% higher in protected than non-managed areas. Main conclusions: AGC and large trees were negatively associated with human activities, highlighting the importance of forest management. Redefining large trees as ≥ 50 cm DBH (4.3% more stems) would account for 20% more AGC. This study demonstrates that protecting relatively undisturbed forests can be disproportionately effective in conserving carbon and suggests that including sustainable forestry in programs like reduced emissions for deforestation and forest degradation could maintain carbon dense forests in logging concessions that are a large proportion of remaining Central African forests. © 2020 John Wiley & Sons Ltd [less ▲]

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See detailPalabres autour des arbres : des discours sur leur intelligence aux dérives de l’anthropomorphisme
Doucet, Jean-Louis ULiege

in Biotechnologie, Agronomie, Société et Environnement (2020), 24(3), 203-206

The intelligence of trees is an issue that fascinates people in urban areas. It is the subject of passionate debate between forest sector stakeholders. This article aims to objectify this debate by ... [more ▼]

The intelligence of trees is an issue that fascinates people in urban areas. It is the subject of passionate debate between forest sector stakeholders. This article aims to objectify this debate by synthesizing recent knowledge on the subject. It shows that trees can communicate with each other, either via volatile molecules or via underground exchanges, in particular through a mycorrhizal network. Trees can also perceive light and sound. They can therefore adapt to a changing environment, which reflects a certain form of intelligence. Nevertheless, abandoning timber logging for this reason is not acceptable. This would result in environmental impacts that are often overlooked by the opponents of logging. [less ▲]

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See detailThe global abundance of tree palms
Muscarella, Robert; Emilio, Thaise; Phillips, Oliver L. et al

in Global Ecology and Biogeography (2020), 00

Aim: Palms are an iconic, diverse and often abundant component of tropical ecosystems that provide many ecosystem services. Being monocots, tree palms are evolutionarily, morphologically and ... [more ▼]

Aim: Palms are an iconic, diverse and often abundant component of tropical ecosystems that provide many ecosystem services. Being monocots, tree palms are evolutionarily, morphologically and physiologically distinct from other trees, and these differences have important consequences for ecosystem services (e.g., carbon sequestration and storage) and in terms of responses to climate change. We quantified global patterns of tree palm relative abundance to help improve understanding of tropical forests and reduce uncertainty about these ecosystems under climate change. Location: Tropical and subtropical moist forests. Time period: Current. Major taxa studied: Palms (Arecaceae). Methods: We assembled a pantropical dataset of 2,548 forest plots (covering 1,191 ha) and quantified tree palm (i.e., ≥10 cm diameter at breast height) abundance relative to co-occurring non-palm trees. We compared the relative abundance of tree palms across biogeographical realms and tested for associations with palaeoclimate stability, current climate, edaphic conditions and metrics of forest structure. Results: On average, the relative abundance of tree palms was more than five times larger between Neotropical locations and other biogeographical realms. Tree palms were absent in most locations outside the Neotropics but present in >80% of Neotropical locations. The relative abundance of tree palms was more strongly associated with local conditions (e.g., higher mean annual precipitation, lower soil fertility, shallower water table and lower plot mean wood density) than metrics of long-term climate stability. Life-form diversity also influenced the patterns; palm assemblages outside the Neotropics comprise many non-tree (e.g., climbing) palms. Finally, we show that tree palms can influence estimates of above-ground biomass, but the magnitude and direction of the effect require additional work. Conclusions: Tree palms are not only quintessentially tropical, but they are also overwhelmingly Neotropical. Future work to understand the contributions of tree palms to biomass estimates and carbon cycling will be particularly crucial in Neotropical forests. [less ▲]

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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 detailMiocene Diversification in the Savannahs Precedes Tetraploid Rainforest Radiation in the African Tree Genus Afzelia (Detarioideae, Fabaceae)
Donkpegan, Armel S. L.; Doucet, Jean-Louis ULiege; Hardy, Olivier J. et al

in Frontiers in Plant Science (2020), 11(798),

The dating of diversification events, including transitions between biomes, is key to elucidate the processes that underlie the assembly and evolution of tropical biodiversity. Afzelia is a widespread ... [more ▼]

The dating of diversification events, including transitions between biomes, is key to elucidate the processes that underlie the assembly and evolution of tropical biodiversity. Afzelia is a widespread genus of tropical trees, threatened by exploitation for its valuable timber, that presents an interesting system to investigate diversification events in Africa. Africa hosts diploid Afzelia species in the savannahs north and south of the Guineo-Congolian rainforest and autotetraploid species confined to the rainforest. Species delimitation and phylogenetic relationships among the diploid and tetraploid species remained unresolved in previous studies using small amounts of DNA sequence data. We used genotyping-by-sequencing in the five widespread Afzelia species in Africa, the savannah species A. africana and A. quanzensis and the rainforest species A. bipindensis, A. pachyloba, and A. bella. Maximum likelihood and coalescent approaches resolved all species as monophyletic and placed the savannah and rainforest taxa into two separate clades corresponding to contrasted ploidy levels. Our data are thus compatible with a single biome shift in Afzelia in Africa, although we were unable to conclude on its direction. SNAPP calibrated species trees show that the savannah diploids started to diversify early, at 12 (9.09–14.89) Ma, which contrasts with a recent and rapid diversification of the rainforest tetraploid clade, starting at 4.22 (3.12 – 5.36) Ma. This finding of older diversification in a tropical savannah clade vs. its sister rainforest clade is exceptional; it stands in opposition to the predominant observation of young ages for savannahs lineages in tropical regions during the relatively recent expansion of the savannah biome. [less ▲]

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See detailLong-term thermal sensitivity of Earth’s tropical forests
Sullivan, Martin J.P.; Lewis, Simon L.; Affum-Baffoe, Kofi et al

in Science (2020), 368

The sensitivity of tropical forest carbon to climate is a key uncertainty in predicting global climate change. Although short-term drying and warming are known to affect forests, it is unknown if such ... [more ▼]

The sensitivity of tropical forest carbon to climate is a key uncertainty in predicting global climate change. Although short-term drying and warming are known to affect forests, it is unknown if such effects translate into long-term responses. Here, we analyze 590 permanent plots measured across the tropics to derive the equilibrium climate controls on forest carbon. Maximum temperature is the most important predictor of aboveground biomass (−9.1 megagrams of carbon per hectare per degree Celsius), primarily by reducing woody productivity, and has a greater impact per °C in the hottest forests (>32.2°C). Our results nevertheless reveal greater thermal resilience than observations of short-term variation imply. To realize the long-term climate adaptation potential of tropical forests requires both protecting them and stabilizing Earth’s climate. [less ▲]

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See detailAsynchronous carbon sink saturation in African and Amazonian tropical forests
Hubau, Wannes; Lewis, Simon L.; Phillips, Oliver L. et al

in Nature (2020), 579

Structurally intact tropical forests sequestered about half of the global terrestrial carbon uptake over the 1990s and early 2000s, removing about 15 per cent of anthropogenic carbon dioxide emissions1–3 ... [more ▼]

Structurally intact tropical forests sequestered about half of the global terrestrial carbon uptake over the 1990s and early 2000s, removing about 15 per cent of anthropogenic carbon dioxide emissions1–3. Climate-driven vegetation models typically predict that this tropical forest ‘carbon sink’ will continue for decades4,5. Here we assess trends in the carbon sink using 244 structurally intact African tropical forests spanning 11 countries, compare them with 321 published plots from Amazonia and investigate the underlying drivers of the trends. The carbon sink in live aboveground biomass in intact African tropical forests has been stable for the three decades to 2015, at 0.66 tonnes of carbon per hectare per year (95 per cent confidence interval 0.53–0.79), in contrast to the long-term decline in Amazonian forests6. Therefore the carbon sink responses of Earth’s two largest expanses of tropical forest have diverged. The difference is largely driven by carbon losses from tree mortality, with no detectable multi-decadal trend in Africa and a long-term increase in Amazonia. Both continents show increasing tree growth, consistent with the expected net effect of rising atmospheric carbon dioxide and air temperature7–9. Despite the past stability of the African carbon sink, our most intensively monitored plots suggest a post-2010 increase in carbon losses, delayed compared to Amazonia, indicating asynchronous carbon sink saturation on the two continents. A statistical model including carbon dioxide, temperature, drought and forest dynamics accounts for the observed trends and indicates a long-term future decline in the African sink, whereas the Amazonian sink continues to weaken rapidly. Overall, the uptake of carbon into Earth’s intact tropical forests peaked in the 1990s. Given that the global terrestrial carbon sink is increasing in size, independent observations indicating greater recent carbon uptake into the Northern Hemisphere landmass10 reinforce our conclusion that the intact tropical forest carbon sink has already peaked. This saturation and ongoing decline of the tropical forest carbon sink has consequences for policies intended to stabilize Earth’s climate. [less ▲]

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See detailPast human disturbances and soil fertility both influence the distribution of light-demanding tree species in a Central African tropical forest
Vleminckx, Jason; Bauman, David; Demanet, Marine et al

in Journal of Vegetation Science (2020), 31

Questions: In vast areas of Central African forests, the upper canopy is presently dominated by light-demanding tree species. Here, we confront three hypotheses to explain this dominance: (a) these ... [more ▼]

Questions: In vast areas of Central African forests, the upper canopy is presently dominated by light-demanding tree species. Here, we confront three hypotheses to explain this dominance: (a) these species have expanded their distribution because of widespread past slash-and-burn activities, as suggested by important charcoal amounts recorded in the soils of the region; (b) their abundance is rather explained by soil properties, as this guild establishes preferentially on favourable physico-chemical conditions for rapid growth; (c) soil properties have been substantially influenced by past human disturbances and those two effects cannot be disentangled. Location: Pallisco-CIFM logging concession, southeastern Cameroon (300,000 ha). Methods: We quantified soil charcoal abundance and measured ten soil variables at the basis of 60 target trees that belonged to a list of three long-living pioneer lightdemanding (LLP) and four shade-bearer (SB) species. We identified all stems with a diameter at breast height (DBH) ≥ 20 cm within a distance of 15 m around each target tree. Species were characterised by their wood-specific gravity (WSG), which reflected their light requirement. Multiple regression models were used to quantify and test the relative effects of charcoal abundance and soil variables on the mean WSG of the 60 tree communities, as well as the abundance of three guilds: LLP, SB, and non-pioneer light demanders (NPLD). Results: The mean WSG was the only response variable significantly explained by soil variables and charcoal abundance combined. It was significantly negatively associated with soil calcium and Mg content and with charcoal abundance, with soil and charcoal influencing the mean WSG independently. Conclusion: Our study provides evidence that past human disturbances and soil fertility have independently promoted the establishment of light-demanding species in western Central African forests, thereby shedding light on tree community assembly rules in these ecosystems which remain considerably understudied compared to the tropical forests of other continents. [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 detailRemoval and predation of aril-covered seeds: the case of Afzelia bipindensis (Fabaceae - Detarioidae)
Evrard, Quentin ULiege; Hardy, Olivier; Tagg, Nikki et al

in Plant Ecology and Evolution (2019)

Background and aims – Most tree species with aril-covered seeds are assumed to be dispersed by frugivores. However, the number of studied African rainforest plant species remains low. This study focused ... [more ▼]

Background and aims – Most tree species with aril-covered seeds are assumed to be dispersed by frugivores. However, the number of studied African rainforest plant species remains low. This study focused on Afzelia bipindensis, an important timber species, which produces seeds partly covered by an aril. Specifically, this study aimed to: (1) identify the dispersers and the predators of A. bipindensis seeds, (2) characterize the role of those dispersers and predators in the regeneration process, and (3) understand the role of the aril in seed germination in relation to the feeding behaviour of the identified dispersers. Methods – The study took place in a Gabonese evergreen rainforest in 2015 and in a Cameroonian semideciduous rainforest in 2016 and 2017. We conducted more than 100 hours of direct observations, and used camera traps to monitor animal activities for 3000 hours within the canopy and 10 000 hours on the ground under fruiting trees. Key results – Three rodent taxa (Cricetomys emini, Funisciurus isabella and an undetermined species of Muridae) were mainly observed interacting with the seeds but neither birds nor monkeys were observed. Rodents removed more than 90% of the seeds, after detaching the aril, to probably cache them in burrows or superficial caches. Seeds from which we manually removed the aril (mimicking rodent behaviour) had a higher germination rate. Conclusions – Rodents may play a more important role than expected in the dynamics of tree species producing aril-covered seeds. [less ▲]

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See detailDynamique des populations d’azobé, Lophira alata Banks ex C. F. Gaertn., et implications pour sa gestion durable au Cameroun
Biwolé, Achille ULiege; Ouédraogo, Dakis-Yaoba; Betti, Jean Lagarde et al

in Bois et Forêts des Tropiques (2019), 342(novembre 2019), 55-68

L’impact de l’exploitation forestière sur le renouvellement du stock de bois d’oeuvre reste largement méconnu en Afrique centrale du fait du manque de données sur la dynamique des populations d’arbres ... [more ▼]

L’impact de l’exploitation forestière sur le renouvellement du stock de bois d’oeuvre reste largement méconnu en Afrique centrale du fait du manque de données sur la dynamique des populations d’arbres exploités. C’est en particulier le cas pour l’azobé, Lophira alata, un bois d’oeuvre de grande valeur commerciale. L’objectif de cette étude est double : quantifier l’effet du type forestier et de l’exploitation sur la croissance de l’azobé et simuler l’évolution du stock exploitable et du taux de reconstitution après exploitation. Nous avons effectué pendant trois ans un suivi annuel de la croissance et de la mortalité dans trois types forestiers au Cameroun : en forêt sempervirente, en forêt mixte et en forêt semi-caducifoliée. Le recrutement a été étudié uniquement en forêt mixte, sous deux conditions : en milieu exploité et non exploité. Nous avons calibré, avec ces données, un modèle matriciel de Usher. Douze scénarios d’exploitation ont été simulés en faisant varier le diamètre minimum d’exploitation de 60, 70 et 80 cm, et l’intensité de prélèvement des arbres de 100 à 40 %. La croissance de l’azobé est influencée à la fois par le type forestier et l’exploitation. Les arbres de forêt sempervirente ont une croissance plus faible jusqu’à 50 cm de diamètre, alors que la croissance maximale prédite pour ce type forestier est la plus élevée. L’exploitation a par ailleurs stimulé la croissance. Enfin, l’exploitation de l’azobé ne respecte pas le principe du rendement soutenu : ses taux de croissance à long terme varient entre 0,54 et 0,83 %. Pour garantir la durabilité de son exploitation au Cameroun, une sylviculture dynamisant la croissance des futurs arbres exploitables, ainsi que leur régénération, s’avère indispensable. [less ▲]

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See detailPerceptions of ecosystem services provided by tropical forests to local populations in Cameroon
Lhoest, Simon ULiege; Dufrêne, Marc ULiege; Vermeulen, Cédric ULiege et al

in Ecosystem Services (2019), 38

In Central Africa, local populations are deeply dependent on tropical forests, which provide numerous ecosystem services (ES). For the first time in Central Africa, we assessed the perceptions of ES ... [more ▼]

In Central Africa, local populations are deeply dependent on tropical forests, which provide numerous ecosystem services (ES). For the first time in Central Africa, we assessed the perceptions of ES provided by tropical forests to local populations, considering three land allocation types: a protected area, a Forest Stewardship Council (FSC)-certified logging concession, and three community forests. We conducted a questionnaire survey with 225 forest stakeholders in southeastern Cameroon, combining an open-ended question and 16 directed questions to evaluate the perceptions of ES significance and abundance, respectively. The ES most frequently reported as significant were provisioning (93% of respondents) and cultural & amenity services (68%), whereas regulating services were less mentioned (16%). Bushmeat provision was the only ES perceived as highly significant but not very abundant. There were slight variations of perceptions among forest land allocation types and respondents, suggesting a relative homogeneity in ES abundance. For further integrative ES assessment, we suggest quantifying ES with complementary ecological and economic approaches, such as meat provision, recreation, tourism, timber provision, spiritual experience, firewood provision, water quality regulation, and inspiration for culture. We also give three concrete recommendations for forest management, the most urgent being to provide sources of protein alternative to bushmeat. [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 detailAn assessment of the terrestrial mammal diversity in a sustainably logged forest in east Gabon: Impact of camera trap placement strategy on the detected species
Fonteyn, Davy ULiege; Cornélis, Daniel; Deflandre, Nicolas et al

Conference (2019, August)

Camera traps are widely used for assessing terrestrial vertebrate diversity across tropical forests. Non-random placement strategy is traditionally adopted, with camera traps oriented towards specific ... [more ▼]

Camera traps are widely used for assessing terrestrial vertebrate diversity across tropical forests. Non-random placement strategy is traditionally adopted, with camera traps oriented towards specific features such as game trails. However, this could artificially bias the capture rates of certain species. Here, we first assessed the terrestrial mammal diversity of sustainably logged forests in east Gabon. Then, we investigated the impact of placement strategy on the detected diversity by comparing game-trail based and systematically oriented camera traps. We followed a grid design replicated consecutively in four areas, composed of 15-17 sampling points placed every 2 km², and left for one month on the field. Each sampling point was composed of two cameras: the ‘systematic camera’ was placed close to the theoretical point and oriented towards a naturally cleared area, while the ‘game-trail oriented camera’ was located within a 20 m radius of the random camera. A total of 31 mammal species were identified, including gorillas, chimps, elephants, and leopards. Game-trail placement provided greater relative abundance for most species and the deviation to this pattern only concerned extremely infrequent species (sitatunga, golden cat). Multivariate analyses did not distinguish different species composition between the two strategies at the site scale (grid), although local differences did appear between pairs at the camera scale. When examining species occupancy, game-trail strategy does not seem to bias inventories compared to the random placement, and data from both strategies can be used in multi-site analyses, but this does not hold true for relative abundance. However, it is almost impossible to set up a strict random sampling and both strategies need a subjective decision when installing camera traps. We recommend maintaining game-trail orientation for large-scale camera trapping inventories conducted at species or community level. [less ▲]

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See detailAn assessment of the terrestrial mammal diversity in a sustainably logged forest in east Gabon: Impact of camera trap placement strategy on the detected species
Fonteyn, Davy ULiege; Cornélis, Daniel; Deflandre, Nicolas et al

Conference (2019, August)

Camera traps are widely used for assessing terrestrial vertebrate diversity across tropical forests. Non-random placement strategy is traditionally adopted, with camera traps oriented towards specific ... [more ▼]

Camera traps are widely used for assessing terrestrial vertebrate diversity across tropical forests. Non-random placement strategy is traditionally adopted, with camera traps oriented towards specific features such as game trails. However, this could artificially bias the capture rates of certain species. Here, we first assessed the terrestrial mammal diversity of sustainably logged forests in east Gabon. Then, we investigated the impact of placement strategy on the detected diversity by comparing game-trail based and systematically oriented camera traps. We followed a grid design replicated consecutively in four areas, composed of 15-17 sampling points placed every 2 km², and left for one month on the field. Each sampling point was composed of two cameras: the ‘systematic camera’ was placed close to the theoretical point and oriented towards a naturally cleared area, while the ‘game-trail oriented camera’ was located within a 20 m radius of the random camera. A total of 31 mammal species were identified, including gorillas, chimps, elephants, and leopards. Game-trail placement provided greater relative abundance for most species and the deviation to this pattern only concerned extremely infrequent species (sitatunga, golden cat). Multivariate analyses did not distinguish different species composition between the two strategies at the site scale (grid), although local differences did appear between pairs at the camera scale. When examining species occupancy, game-trail strategy does not seem to bias inventories compared to the random placement, and data from both strategies can be used in multi-site analyses, but this does not hold true for relative abundance. However, it is almost impossible to set up a strict random sampling and both strategies need a subjective decision when installing camera traps. We recommend maintaining game-trail orientation for large-scale camera trapping inventories conducted at species or community level. [less ▲]

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See detailUne forte saisonnalité du climat et de la phénologie reproductive dans la forêt du Mayombe : l’apport des données historiques de la Réserve de Luki en République démocratique du Congo
Ilondea, B. A.; Beeckman, H.; Ouédraogo, D.-Y. et al

in Bois et Forêts des Tropiques (2019), (341), 39-53

En Afrique, la phénologie reproductive des arbres tropicaux, majoritairement annuelle, semble présenter une certaine régularité. Cette étude documente les variations intra- et interannuelles de la ... [more ▼]

En Afrique, la phénologie reproductive des arbres tropicaux, majoritairement annuelle, semble présenter une certaine régularité. Cette étude documente les variations intra- et interannuelles de la phénologie reproductive des arbres de la forêt du Mayombe à partir des données historiques de la Réserve de Luki (République démocratique du Congo). Le diamètre de reproduction des espèces exploitées pour le bois, encore largement méconnu, a été également examiné pour les espèces suffisamment représentées dans les données. Le suivi phénologique de 3 642 arbres appartenant à 158 espèces et 39 familles a été réalisé tous les 10 jours de 1948 à 1957. Les statistiques circulaires ont été utilisées pour tester le synchronisme de la phénologie entre arbres, à l’échelle de la communauté, pour la forêt dans son ensemble, et individuellement pour 87 espèces, dont 35 espèces bien représentées (n ≥ 20 arbres), 16 espèces commerciales et 36 autres espèces. Des régressions logistiques ont permis de déterminer le diamètre de fructification (minimum et régulier) de ces espèces. Pour la majorité des espèces, la floraison était régulière, annuelle et largement saisonnière (81,6 %, 71 espèces). Les pics étaient plus marqués pour la floraison que pour la fructification, plus étalée dans le temps, bien que significativement agrégée temporellement. La majorité des arbres et des espèces fleurissaient entre décembre et février, pendant la petite saison sèche, bien que des fleurs et des fruits étaient observables toute l’année à l’échelle de la communauté. Seules 13 espèces ont montré une relation significative entre le diamètre et la reproduction, parmi lesquelles sept espèces de canopée, cinq de sous-bois et une héliophile. Pour ces espèces, la moyenne du diamètre minimum de reproduction était de 17,3 cm. [less ▲]

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See detailSeed and pollen dispersal distances in two African legume timber trees and their reproductive potential under selective logging
Hardy, Olivier J.; Delaide, Boris; Hainaut, Hélène et al

in Molecular Ecology (2019)

The natural regeneration of tree species depends on seed and pollen dispersal. To assess whether limited dispersal could be critical for the sustainability of selective logging practices, we performed ... [more ▼]

The natural regeneration of tree species depends on seed and pollen dispersal. To assess whether limited dispersal could be critical for the sustainability of selective logging practices, we performed parentage analyses in two Central African legume canopy species displaying contrasted floral and fruit traits: Distemonanthus benthamianus and Erythrophleum suaveolens. We also developed new tools linking forward dispersal kernels with backward migration rates to better characterize long‐distance dispersal. Much longer pollen dispersal in D. benthamianus (mean distance dp = 700 m, mp = 52% immigration rate in 6 km2 plot, s = 7% selfing rate) than in E. suaveolens (dp = 294 m, mp = 22% in 2 km2 plot, s = 20%) might reflect different insect pollinators. At a local scale, secondary seed dispersal by vertebrates led to larger seed dispersal distances in the barochorous E. suaveolens (ds = 175 m) than in the wind‐dispersed D. benthamianus (ds = 71 m). Yet, seed dispersal appeared much more fat‐tailed in the latter species (15%–25% seeds dispersing >500 m), putatively due to storm winds (papery pods). The reproductive success was correlated to trunk diameter in E. suaveolens and crown dominance in D. benthamianus. Contrary to D. benthamianus, E. suaveolens underwent significant assortative mating, increasing further the already high inbreeding of its juveniles due to selfing, which seems offset by strong inbreeding depression. To achieve sustainable exploitation, seed and pollen dispersal distances did not appear limiting, but the natural regeneration of E. suaveolens might become insufficient if all trees above the minimum legal cutting diameter were exploited. This highlights the importance of assessing the diameter structure of reproductive trees for logged species. [less ▲]

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See detailQuelles forêts laisserons-nous à nos petits-enfants ?
Doucet, Jean-Louis ULiege; Lejeune, Philippe ULiege

Conference given outside the academic context (2019)

•Les forêts et la déforestation •Les forêts d’Afrique centrale •La forêt wallonne •Les forêts et le changement climatique

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