References of "Doucet, Jean-Louis"
     in
Bookmark and Share    
Full Text
See detailLate-Holocene tropical moist-forests of southeastern Cameroon: some insight from soil charcoal analysis
Morin, Julie ULg; Biwolé, Achille; Bourland, Nils et al

Conference (2015, August)

Tropical forests of Central Africa constitute the second most important block of moist forest of the world. Little is known, however, about past vegetation in this region that remains underexplored ... [more ▼]

Tropical forests of Central Africa constitute the second most important block of moist forest of the world. Little is known, however, about past vegetation in this region that remains underexplored (Vleminckx et al. 2014; Morin-Rivat et al. 2014). Determining the past specific composition of these forests could allow bringing insights into their evolution over time and providing data about their resilience capacity facing global change. We performed a pedoanthracological analysis in the semi-deciduous forests of southeastern Cameroon. We excavated 53 test pits of 53 50 × 50 × 60 cm in plots of botanical inventory along a NS 80-km long mega-transect that followed a vegetation gradient. We sorted and quantified charred macrobotanical remains by layers of 10 cm, then identified species from wood charcoals. We used the InsideWood database, implemented with 163 new anatomical descriptions of woods present in the study area by using the reference collection of African woods of the Royal Museum for Central Africa (Belgium). Finally, we obtained 25 radiocarbon dates on charcoals and oil palm endocarps. Results showed that repeated fire events occurred across the study area during the last 2500 years, soon after the well-documented “rainforest crisis” (e.g. Lézine et al. 2013). The analyzed charcoals are likely human-induced regarding evidence of associated human settlements (e.g. potsherds). Aged were distributed into two time periods: the Early Iron Age (2300-1300 BP) and the Late Iron Age (700-100 BP) with an intermediate hiatus in human occupation (see e.g. Wotzka 2006; Morin-Rivat et al. 2014). Specific composition during both periods did not strongly differ from current composition, which is now dominated by light-demanding canopy trees belonging to old-growth semi-deciduous Celtis forests (Gond et al. 2013; Fayolle et al. 2014). This argues in favor of the maintenance of light-demanding tree species by anthropogenic activities, such as slash-and-burn shifting cultivation. We conclude that moist forests have a good resilience capacity regarding moderate and scattered disturbances. These forests can nonetheless be deeply impacted by land-use intensification (e.g. degraded forests along roads and close to cities; Gond et al. 2013). [less ▲]

Detailed reference viewed: 41 (4 ULg)
Full Text
Peer Reviewed
See detailEvolutionary drivers of species delimitation in African polyploid complex trees genus Afzelia: insights from molecular phylogeny
Donkpegan, Segbedji ULg; Duminil, Jérôme; Daïnou, Kasso ULg et al

Conference (2015, July 13)

Background:. Molecular markers can improve our knowledge of the rain forest biodiversity, especially to decipher species evolution and delimitation within genera. In this study, we investigated ... [more ▼]

Background:. Molecular markers can improve our knowledge of the rain forest biodiversity, especially to decipher species evolution and delimitation within genera. In this study, we investigated evolutionary relationships among the Afzelia genus, an important tropical timber taxon in Africa.. Method: We used nuclear and chloroplast DNA associated with partial plastome sequences data to infer phylogenetic relationships among the six broadly distributed species of the genus: A. africana and A. quanzensis (savannah species), A. bipindensis, A. bella, A. pachyloba and A. parviflora (forest species). Using microsatellite markers (SSR), we also applied a clustering analysis (STRUCTURE) to verify whether the current taxonomic species delimitation matches the biological species concept. Result and discussion: Our SSR data showed for the first time that savannah species were diploid while forest species were tetraploid. Nuclear DNA separates diploid and tetraploid species in two distinct cladesbut plastid markers show that one diploid species forms a well-supported clade with the tetraploids, suggesting historical hybridization, possibly in relation with genome duplication (polyploidization) and habitat shift from dry to rain forests. The genetic structure observed with SSR confirms the taxonomic delimitation of the two diploid species and one tetraploid species (A. pachyloba). It also suggests the existence of a single Afzelia forest species in West Africa, and the presence of two distint species within the A. bipindensis taxon, with potential hybridization with A. bella. Conclusion: The evolutionary history of the genus Afzelia is complex and the potential link between polyploidization and habitat shift needs further investigation. Our data also show that species delimitation must be revisited, at least among three of the four rain forest species. [less ▲]

Detailed reference viewed: 147 (7 ULg)
Full Text
Peer Reviewed
See detailIs western lowland gorilla a good gardener? Effect of fecal matrix and deposition at nest sites on seedling growth
Haurez, Barbara ULg; Brostaux, Yves ULg; Petre, Charles-Albert ULg et al

Conference (2015, June 25)

The Western lowland gorilla is a key dispersal agent, which disperses viable seeds of various size. In consequence of its nesting behavior, gorilla deposits half of its feces, and therefore about half of ... [more ▼]

The Western lowland gorilla is a key dispersal agent, which disperses viable seeds of various size. In consequence of its nesting behavior, gorilla deposits half of its feces, and therefore about half of dispersed seeds, at nest sites. This study was conducted in a logging concession of southeast Gabon where 78 % of the observed nest sites (n=183) were installed in open canopy terra firma forest. The aim of this research was to assess if seed deposition by gorillas (i) in fecal matrix and (ii) at nest sites is advantageous for seedling growth. To assess the effect of fecal matrix, seeds of Santiria trimera (Burseraceae), Chrysophyllum lacourtianum (Sapotaceae) and Plagiostyles africana (Euphorbiaceae) collected in gorilla feces were sown with and without fecal matrix in a nursery at the study site. The impact of seed deposition at nest sites on seedling growth was evaluated in situ. Seedlings of Santiria trimera and Dacryodes normandii (Burseraceae) were installed at nest sites and at closed canopy terra firma forest sites. For both type of trials, seedling growth was monitored. [less ▲]

Detailed reference viewed: 34 (11 ULg)
Full Text
Peer Reviewed
See detailAn estimate of the number of tropical tree species
Slik, J.W. Ferry; Arroyo-Rodriguez, Victor; Aiba, Shin-Ichiro et al

in Proceedings of the National Academy of Sciences of the United States of America (2015), 112(24), 7472-7477

The high species richness of tropical forests has long been recognized, yet there remains substantial uncertainty regarding the actual number of tropical tree species. Using a pantropical tree inventory ... [more ▼]

The high species richness of tropical forests has long been recognized, yet there remains substantial uncertainty regarding the actual number of tropical tree species. Using a pantropical tree inventory database from closed canopy forests, consisting of 657,630 trees belonging to 11,371 species, we use a fitted value of Fisher’s alpha and an approximate pantropical stem total to estimate the minimum number of tropical forest tree species to fall between ∼40,000 and ∼53,000, i.e., at the high end of previous estimates. Contrary to common assumption, the Indo-Pacific region was found to be as species-rich as the Neotropics, with both regions having a minimum of ∼19,000–25,000 tree species. Continental Africa is relatively depauperate with a minimum of ∼4,500–6,000 tree species. Very few species are shared among the African, American, and the Indo-Pacific regions. We provide a methodological framework for estimating species richness in trees that may help refine species richness estimates of tree-dependent taxa. [less ▲]

Detailed reference viewed: 81 (8 ULg)
Full Text
See detailLes arbres utiles du Gabon
Meunier, Quentin; Moumbogou, Carl; Doucet, Jean-Louis ULg

Book published by Presses Agronomiques de Gembloux (2015)

La forêt gabonaise comprend plusieurs centaines d’espèces d’arbres. Une poignée est très connue, beaucoup le sont nettement moins, et certaines sont encore anonymes. Ce guide vous emmène à la découverte ... [more ▼]

La forêt gabonaise comprend plusieurs centaines d’espèces d’arbres. Une poignée est très connue, beaucoup le sont nettement moins, et certaines sont encore anonymes. Ce guide vous emmène à la découverte de 37 familles botaniques et de 225 espèces, dont plus de 140 sont illustrées. Il vous permet de les identifier et de mieux les connaître à l’aide de schémas simples et de près de 1 000 photographies de détails botaniques en couleur. Pour les plus expérimentés, de nouvelles données concernant l’écologie permettront de consolider leurs connaissances. L’objectif de cet ouvrage est le partage et la vulgarisation des connaissances, afin que les agents des administrations en charge des forêts, tout comme les exploitants forestiers ou encore les populations locales, puissent mieux comprendre et gérer ces essences utiles. Il pourra aussi se glisser dans la poche des randonneurs et des naturalistes, qui seront en mesure de reconnaître et de nommer plus facilement ces arbres précieux de la forêt gabonaise. [less ▲]

Detailed reference viewed: 2621 (56 ULg)
Full Text
See detailContributing to wood anatomical databases to improve species identification, phylogeny and functional trait research in Central Africa
Morin, Julie ULg; Fayolle, Adeline ULg; De Ridder, Maaike et al

Poster (2015, May 26)

Central African rainforests shelter a high number of woody species that are anatomically very different. Knowledge of taxon-specific wood anatomical features has proven indispensable for scientific and ... [more ▼]

Central African rainforests shelter a high number of woody species that are anatomically very different. Knowledge of taxon-specific wood anatomical features has proven indispensable for scientific and non-scientific applications. The field of wood anatomy and identification has been drastically revolutionized by the development of internationally recognized lists of precisely illustrated microscopic features (e.g. IAWA Committee 1989), together with the launch of InsideWood, an online search database using these features to narrow down identification results (e.g. Wheeler 2011). However, despite these massive efforts, the anatomy of many species or even genera remains in the dark, especially in species-rich regions. Wood anatomy has been formally described for less than 25% of the Central African woody species (Hubau et al. 2012), the focus has been mainly on timber species and variations in wood anatomical structure remain to be explored. Therefore, we are assembling a wood anatomical database of about 800 species covering the Guineo-Congolian region using material from InsideWood and the Tervuren xylarium (new descriptions). As such, we present how large anatomical databases hold interesting perspectives for (i) wood and charcoal identification, (ii) exploring the phylogenetic signal of wood anatomy, and (iii) the relationship between wood anatomical features and functional traits. [less ▲]

Detailed reference viewed: 33 (3 ULg)
Full Text
Peer Reviewed
See detailQuantity and spatial distribution of seeds dispersed by a western lowland gorilla population in south-east Cameroon
Petre, Charles-Albert ULg; Tagg, Nikki; Beudels-Jamar et al

in Journal of Tropical Ecology (2015), 35(03), 201-212

Detailed reference viewed: 44 (17 ULg)
Full Text
See detailHigh spatial resolution of late-Holocene human activities in the moist forests of Central Africa using soil charcoal and charred botanical remains
Morin, Julie ULg; Biwolé, Achille; Gorel, Anaïs ULg et al

Conference (2015, April 27)

Palaeoecological and archaeological studies have demonstrated that human populations have long inhabited the moist forests of central Africa. However, spatial and temporal patterns of human activities ... [more ▼]

Palaeoecological and archaeological studies have demonstrated that human populations have long inhabited the moist forests of central Africa. However, spatial and temporal patterns of human activities have hardly been investigated with satisfactory accuracy. In this study, we propose to characterize past human activities at local scale by using a systematic quantitative and qualitative methodology based on soil charcoal and charred botanical remains. A total of 88 equidistant test-pits were excavated along six transects in two contrasting forest types in southern Cameroon. Charred botanical remains were collected by water-sieving and sorted by type (wood charcoals, oil palm endocarps, and unidentified seeds). A total of 50 Accelerator Mass Spectrometry 14C dates were also obtained. Results showed that charred macroremains were found at multiple places in the forest, suggesting scattered human activities, which were distributed into two main periods (Phase A: 2300-1300 BP – Phase B: 580 BP to the present). Charred botanical remains indicated two types of land use: (i) domestic, with oil palm endocarps most often associated with potsherds (villages) and (ii) agricultural, with charcoal as probable remnant of slash-and-burn cultivation (fields). Oil palm endocarp abundance decreased with distance from the identified human settlements. Our methodology allowed documenting, at high resolution, the spatial and temporal patterns of human activities in central African moist forests and could be applied to other tropical contexts. [less ▲]

Detailed reference viewed: 19 (4 ULg)
Full Text
Peer Reviewed
See detailComparative effectiveness of silvicultural interventions for increasing timber production and sustaining conservation values in natural tropical production forests. A systematic review protocol
Petrokofsky, Gillian; Sist, Plinio; Blanc, Lilian et al

in Environmental Evidence (2015), 4(8),

Background: Currently, about 400 million hectares of tropical moist forests worldwide are designated production forests, about a quarter of which are managed by rural communities and indigenous peoples ... [more ▼]

Background: Currently, about 400 million hectares of tropical moist forests worldwide are designated production forests, about a quarter of which are managed by rural communities and indigenous peoples. There has been a gradual impoverishment of forest resources inside selectively logged forests in which the volume of timber extracted over the first cutting cycle was mostly from large, old trees that matured over a century or more and grew in the absence of strong anthropological pressures. In forests now being logged for a second and third time, that volume has not been reconstituted due in part to the lack of implementation of post-logging silvicultural treatments. This depletion of timber stocks renders the degraded forests prone to conversion to other land uses. Although it is essential to preserve undisturbed primary forests through the creation of protected areas, these areas alone will not be able to ensure the conservation of all species on a pan-tropical scale, for social, economic and political reasons. The conservation of tropical forests of tomorrow will mostly take place within human-modified (logged, domesticated) forests. In this context, silvicultural interventions are considered by many tropical foresters and forest ecologists as tools capable of effectively conserving tropical forest biodiversity and ecosystem services while stimulating forest production. This systematic review aims to assess past and current evidence of the impact of silviculture on tropical forests and to identify silvicultural practices appropriate for the current conditions in the forests and forestry sectors of the Congo Basin, Amazonia and Southeast Asia. Methods: This systematic review will undertake an extensive search of literature to assess the relative effectiveness of different silvicultural interventions on timber production and the conservation value of forests, and to determine whether there is a relationship between sustainability of timber harvesting and the maintenance/conservation of other ecosystem services and biodiversity in production forests. Data will be extracted for meta-analysis of at least sub-sets of the review questions. Findings are expected to help inform policy and develop evidence-based practice guidelines on silvicultural practices in tropical forests. [less ▲]

Detailed reference viewed: 45 (10 ULg)
Full Text
Peer Reviewed
See detailSeed and pollen dispersal in Guineo-Congolian canopy tree species – insights from genetic markers in multiple species
Hardy, Olivier J.; Duminil, Jérôme; Daïnou, Kasso ULg et al

Conference (2015, April)

Detailed reference viewed: 48 (13 ULg)
Full Text
See detailNineteenth century human history explains the dominance of light-demanding tree species in Central African moist forests
Morin, Julie ULg; Fayolle, Adeline ULg; Favier, Charly et al

Poster (2015, March 21)

The canopy of central African moist forests is dominated by light-demanding trees. Most of these species show a distribution of diameters that indicates a regeneration shortage. Here we show through the ... [more ▼]

The canopy of central African moist forests is dominated by light-demanding trees. Most of these species show a distribution of diameters that indicates a regeneration shortage. Here we show through the combined analysis of botanical, palaeoecological, archaeological and historical data that most of these trees are not older than ca. 180 years. This age corresponds to the early 19th century (around 1830) when the slave-raiding, the interethnic wars and the colonization of the inlands by the Europeans disturbed the human spatial occupancy. After 1885, the spatial clumping of people and villages along the main communication axes induced less itinerancy in the forest. We believe that former activities such as shifting cultivation created scattered openings in the canopy, large enough to allow light-demanding trees to establish. Nowadays, common logging operations do not create openings sufficiently large for the regeneration of these high value timber species. Our findings emphasize the need to include considerations about the history of human spatial occupancy and activities to understand forest dynamics. We need silvicultural guidelines adapted to the autecology of the species. Population enforcements (e.g. enrichment) will be needed to ensure the sustainability of timber yields in forests dominated by long-lived light-demanding trees. [less ▲]

Detailed reference viewed: 27 (2 ULg)
See detailThe need for site-specific height-diameter allometry of Central African moist forests
Loubota Panzou, Grâce Jopaul ULg; Doucet, Jean-Louis ULg; Fayolle, Adeline ULg

Conference (2015, March 21)

L’utilisation de l’allométrie hauteur-diamètre globale ou régionale en milieu tropical pourrait avoir des conséquences importantes dans les estimations de biomasse et des stocks de carbone. L’objectif de ... [more ▼]

L’utilisation de l’allométrie hauteur-diamètre globale ou régionale en milieu tropical pourrait avoir des conséquences importantes dans les estimations de biomasse et des stocks de carbone. L’objectif de ce travail est d’identifier les variations de l’allométrie hauteur-diamètre au sein de deux types de forêts (forêt sempervirente et forêt semi-décidue) au sud du Cameroun et d’examiner leurs conséquences sur les estimations de biomasse. Le diamètre et la hauteur ont été mesurés sur un total de 521 arbres appartenant à 15 espèces et couvrant une gamme de diamètre de 10 à 240 cm. Une calibration des mesures non destructives et destructives de la hauteur a été réalisée sur 60 arbres. Dix modèles allométriques ont été ajustés sur ces données. Le meilleur modèle a été sélectionné avec Akaike Information Criterion (AIC). L’allométrie hauteur-diamètre au niveau des sites et entre les espèces a montré une tendance asymptotique (Modèle de Michaelis-Menten). Pour un même diamètre, les arbres étaient plus hauts dans les forêts semi-décidues que dans les forêts sempervirentes. Les différences de biomasse entre les deux types de forêts sont dues par les variations de l’allométrie hauteur-diamètre. Les variations de l’allométrie hauteur-diamètre sont donc d’une extrême importance dans les estimations de biomasse et des stocks de carbone des forêts denses humides tropicales d’Afrique centrale. [less ▲]

Detailed reference viewed: 108 (17 ULg)
Full Text
Peer Reviewed
See detailDifferences in dung beetle activity at western gorilla defecation sites in south-east Cameroon: implications for establishment of Uapaca spp. seedlings
Petre, Charles-Albert ULg; Zinque, Marie-Hélène; Tagg, Nikki et al

in Journal of Tropical Ecology (2015), 31(02), 161-174

Detailed reference viewed: 24 (9 ULg)
Full Text
See detailApproche agroforestière. Synthèse des travaux menés par le projet DACEFI2 en agroforesterie. Document de capitalisation.
Boldrini, Sylvie; Meunier, Quentin; Boukouendji, Basile et al

E-print/Working paper (2015)

Le projet DACEFI-2 a eu pour mission première la promotion de la foresterie communautaire comme outil de développement des communautés rurales. L’approche au Gabon en matière de gestion des terroirs ... [more ▼]

Le projet DACEFI-2 a eu pour mission première la promotion de la foresterie communautaire comme outil de développement des communautés rurales. L’approche au Gabon en matière de gestion des terroirs villageois s’est voulue plus embrassante, promouvant en sus de l’exploitation forestière des activités comme l’agriculture, le maraîchage, la collecte des produits forestiers non ligneux ou encore l’agroforesterie. L’agroforesterie est une thématique qui converge parfaitement avec la gestion raisonnée de la forêt, et idéalement avec les modes d’interaction préexistants des villageois avec celle-ci. Concilier dans un même espace la culture de plantes vivrières et l’accès à des arbres à fort intérêt socio-économique apporte une plus-value notoire aux parcelles cultivées. L’optimisation des techniques culturales permet une meilleure productivité et une incitation à la sédentarisation des cultures, élément important à considérer compte tenu des difficultés d’entretien des parcelles éloignées du village (notamment liées aux dégâts causés par les animaux). Ce recueil compile les travaux réalisés en agroforesterie par les équipes du projet DACEFI-2. Il rappelle la stratégie d’intervention et les différentes activités menées, de la sensibilisation auprès des plus jeunes à la promotion de certains produits forestiers non ligneux à potentiel économique avéré. La promotion de l’arbre, de la récolte de la graine jusqu’à sa plantation en passant par sa mise en pépinière aura également animé toute l’équipe durant ces années d’exercice, afin de faire un peu plus valoir ses multiples intérêts et susciter les efforts de gestion, de conservation et de reboisement. [less ▲]

Detailed reference viewed: 102 (10 ULg)
Full Text
See detailSite-specific height-diameter allometry of Central African moist forests
Loubota Panzou, Grâce Jopaul ULg; Doucet, Jean-Louis ULg; Fayolle, Adeline ULg

Poster (2015, February 04)

In this study we aimed to identify the variation in height-diameter allometry between forest types and among species in Central African moist forests. We also examined the consequences on biomass ... [more ▼]

In this study we aimed to identify the variation in height-diameter allometry between forest types and among species in Central African moist forests. We also examined the consequences on biomass estimation. Two forest sites in southern Cameroon with contrasting levels of deciduousness. Height and diameter were measured for a total of 521 trees belonging to 12 timber species over a large range of diameter, 10-240 cm for the Ma’an site and 11-182 cm for the Mindourou site. Non-destructive height measurements were calibrated with destructive measurements for a total of 60 trees, 30 in each site. Commercial forest inventory data (n=7253 0.5ha plots) were gathered for the Ma’an (n=34 samples and 2101 plots) and Mindourou (n=117 samples and 5152 plots) sites. A total of ten allometric models (including asymptotic and non-asymptotic models) were fitted to the height-diameter data at species (n=12) and site (n=2) level. Biomass estimates were computed based on forest inventory data and general allometric models using both site-specific and published height-diameter equations. Given the strong correlation between the non-destructive and destructive height measurements we had confidence in using the non-destructive height measurements to establish site- and species-specific height-diameter allometric equations. The height measurements performed over a wide range of diameters, 10-240 cm, tended to support an asymptotic shape (and most often the Michaelis Menten model) for the height-diameter allometry either at species and site level. We identified a significant difference in height-diameter allometry between the two study sites. For a given diameter, trees tended to be taller in the more semi-deciduous Mindourou site than in the more evergreen Ma’an site, with a maximum height of 39.5 and 46.5 m, respectively. The two sites significantly differed in stand structure and biomass. This difference is due to the variation in height-diameter allometry. Height-diameter allometry strongly varies between sites and site-specific height-diameter allometric equations should be developed to further improve the estimation of biomass and carbon stock contained in tropical forests. [less ▲]

Detailed reference viewed: 161 (45 ULg)
Full Text
Peer Reviewed
See detailDifferential Performance between Two Timber Species in Forest Logging Gaps and in Plantations in Central Africa
Fayolle, Adeline ULg; Ouedraogo, Dakis-Yaoba ULg; Ligot, Gauthier ULg et al

in Forests (2015), 6(2), 380-394

To develop silvicultural guidelines for high-value timber species of Central African moist forests, we assessed the performance of the pioneer Milicia excelsa (iroko, Moraceae), and of the non-pioneer ... [more ▼]

To develop silvicultural guidelines for high-value timber species of Central African moist forests, we assessed the performance of the pioneer Milicia excelsa (iroko, Moraceae), and of the non-pioneer light demander Pericopsis elata (assamela, Fabaceae) in logging gaps and in plantations in highly degraded areas in south-eastern Cameroon. The survival and size of each seedling was regularly monitored in the silvicultural experiments. Differences in performance and allometry were tested between species in logging gaps and in plantations. The two species performance in logging gaps was significantly different from plantations and concurred with the expectations of the performance trade-off hypothesis but not with the expectations of species light requirements. The pioneer M. excelsa survived significantly better in logging gaps while the non-pioneer P. elata grew significantly faster in plantations. The high mortality and slow growth of M. excelsa in plantations is surprising for a pioneer species but could be explained by herbivory (attacks from a gall-making psyllid). Identifying high-value native timber species (i) with good performance in plantations such as P. elata is of importance to restore degraded areas; and (ii) with good performance in logging gaps such as M. excelsa is of importance to maintain timber resources and biodiversity in production forests. [less ▲]

Detailed reference viewed: 29 (5 ULg)
Full Text
See detailIdentification of charred botanical remains provides more accurate information on past history in Central Africa
Morin, Julie ULg; Biwolé, Achille; Bourland, Nils et al

Poster (2015, January 30)

In palaeoenvironmental studies, charred botanical remains have rarely been identified to the species level before being sent to radiocarbon dating. Moreover, the age of most tropical spp. and thereby the ... [more ▼]

In palaeoenvironmental studies, charred botanical remains have rarely been identified to the species level before being sent to radiocarbon dating. Moreover, the age of most tropical spp. and thereby the age of the carbon sequestered during plant growth is not known. Dating unidentified charred wood in the tropics should be thus treated with caution because the accuracy of the dates is not guaranteed. Here we present 71 dates obtained on charred endocarps and wood charcoals sampled in soil pits in Cameroon and in the Rep. of the Congo. We taxonomically identified 43 samples then selected both identified and unidentified individual fragments for radiocarbon dating. We performed summed probability distributions of the dates calibrated in BP for the 43 identified and the 28 unidentified samples separately then for the whole dates. Results showed that the dates obtained on unidentified samples better fit the established chronology for Central Africa but that they also presented less precise standard deviations than the dates obtained on identified short-lived material, and that the dates on identified samples provide more detailed trends about the phases of human occupation in Central Africa after 2,500 BP. We can assume that dating unidentified material may introduce some blur into chronologies and that the selection of identified charred botanical remains should be systematically applied for palaeoenvironmental reconstructions in tropical contexts to refine the chronologies. [less ▲]

Detailed reference viewed: 21 (2 ULg)
Full Text
Peer Reviewed
See detailHow Tightly Linked Are Pericopsis elata (Fabaceae) Patches to Anthropogenic Disturbances in Southeastern Cameroon?
Bourland, Nils; Cerisier, François; Daïnou, Kasso ULg et al

in Forests (2015), 6(2), 293-310

While most past studies have emphasized the relationships between specific forest stands and edaphic factors, recent observations in Central African moist forests suggested that an increase of slash-and ... [more ▼]

While most past studies have emphasized the relationships between specific forest stands and edaphic factors, recent observations in Central African moist forests suggested that an increase of slash-and-burn agriculture since 3000–2000 BP (Before Present) could be the main driver of the persistence of light-demanding tree species. In order to examine anthropogenic factors in the persistence of such populations, our study focused on Pericopsis elata, an endangered clustered timber species. We used a multidisciplinary approach comprised of botanical, anthracological and archaeobotanical investigations to compare P. elata patches with surrounding stands of mixed forest vegetation (“out-zones”). Charcoal samples were found in both zones, but were significantly more abundant in the soils of patches. Eleven groups of taxa were identified from the charcoals, most of them also present in the current vegetation. Potsherds were detected only inside P. elata patches and at different soil depths, suggesting a long human presence from at least 2150 to 195 BP, as revealed by our charcoal radiocarbon dating. We conclude that current P. elata patches most likely result from shifting cultivation that occurred ca. two centuries ago. The implications of our findings for the dynamics and management of light-demanding tree species are discussed. [less ▲]

Detailed reference viewed: 52 (9 ULg)
Full Text
Peer Reviewed
See detailMicrosatellite Development and Flow Cytometry in the African Tree Genus Afzelia (Fabaceae, Caesalpinioideae) Reveal a Polyploid Complex
Donkpegan, Segbedji ULg; Doucet, Jean-Louis ULg; Daïnou, Kasso ULg et al

in Applications in Plant Sciences (2015), 3(1)

Premise of the study: Microsatellites were developed in the vulnerable African rainforest tree Afzelia bipindensis to investigate gene flow patterns. Methods and Results: Using 454 GS-FLX technique, 16 ... [more ▼]

Premise of the study: Microsatellites were developed in the vulnerable African rainforest tree Afzelia bipindensis to investigate gene flow patterns. Methods and Results: Using 454 GS-FLX technique, 16 primer sets were identified and optimized, leading to 11 polymorphic and readable markers displaying each six to 25 alleles in a population. Up to four alleles per individual were found in each of the loci, without evidence of fixed heterozygosity, suggesting an autotetraploid genome. Cross-amplification succeeded for all loci in the African rainforest species A. pachyloba and A. bella, which appeared tetraploid, and for most loci in the African woodland species A. africana and A. quanzensis, which appeared diploid, but failed in the Asian species A. xylocarpa. Flow cytometry confirmed the suspected differences in ploidy. Conclusions: African Afzelia species are diploid or tetraploid, a situation rarely documented in tropical trees. These newly developed microsatellites will help in the study of their mating system and gene flow patterns. [less ▲]

Detailed reference viewed: 29 (8 ULg)
Full Text
Peer Reviewed
See detailModéliser la croissance de quatre essences pour améliorer la gestion forestière au Cameroun
Fétéké, Fousseni; Perin, Jérôme ULg; Fayolle, Adeline ULg et al

in Bois et Forêts des Tropiques (2015), 325(3), 5-20

En Afrique centrale, l’aménagement forestier repose sur une méthode de simulation de la production forestière peu précise, susceptible d’hypothéquer la durabilité de l’exploitation. L’objectif de cette ... [more ▼]

En Afrique centrale, l’aménagement forestier repose sur une méthode de simulation de la production forestière peu précise, susceptible d’hypothéquer la durabilité de l’exploitation. L’objectif de cette étude est d’améliorer la prédiction de la croissance pour quatre essences commerciales importantes en Afrique centrale. Le dispositif d’étude a été installé dans le Sud-Est du Cameroun et comporte 387 arbres : 136 assamela (Pericopsis elata), 54 moabi (Baillonella toxisperma), 124 sapelli (Entandrophragma cylindricum), et 73 tali (Erythrophleum suaveolens). Le diamètre a été mesuré régulièrement entre 2009 et 2012. L’intensité de la compétition a été quantifiée à l’échelle d’une placette circulaire de 20 m de rayon installée autour de chaque arbre focal. Les caractéristiques topographiques et hydrologiques ont été estimées à l’aide d’un système d’information géographique. La croissance a été modélisée en intégrant le diamètre des arbres et les conditions de croissance (indice de compétition et environnement local). Les valeurs d’accroissement utilisées actuellement au Cameroun ne sont pas différentes des valeurs observées en forêt non perturbée par l’exploitation forestière pour l’assamela, le moabi et le tali, mais surestiment la croissance de 20 % pour le sapelli. Un modèle log-normal intégrant le diamètre des arbres et l’intensité de la compétition permet d’estimer l’accroissement des quatre essences avec un coefficient de détermination (R2) variant de 0,092 pour l’assamela à 0,47 pour le moabi. Les variables topographiques et hydrologiques ne permettent pas d’améliorer significativement la qualité des prédictions. Ces modèles peuvent être utilisés pour prédire l’accroissement à partir des données d’inventaires forestiers d’aménagement tels qu’ils sont réalisés en Afrique centrale, en vue d’améliorer la définition de paramètres de gestion tels que le diamètre minimum d’exploitation ou le taux de reconstitution pour les quatre essences étudiées. [less ▲]

Detailed reference viewed: 9 (1 ULg)