Caractérisation de la compétition et de la croissance de Pericopsis elata (Harms) Van Meeuven dans les plantations de la Réserve Forestière de Deng-Deng (Est, Cameroun)

Pericopsis elata est une espèce ligneuse à grande valeur commerciale menacée d’extinction. Les plantations d’Assamela installées dans la Réserve Forestière de Deng-Deng en 1974 ont été abandonnées après leur mise en place. Dès lors, très peu de connaissances relatives au développement de ces peuplements sont disponibles. L’objectif de la présente étude est de contribuer à la compréhension des conditions de croissance de Pericopsis elata dans la réserve et induire un aménagement efficace. Trois inventaires exhaustifs ont été conduits, au cours desquels les données dendrométriques et structurales ont été collectées. Les indices de compétition de Hegyi, les semi-variogrammes et la distribution spatiale des tiges ont été analysés et interprétés. Les densités actuelles sont sans effet limitant pour la croissance des tiges. Les effets du milieu se révèlent comme étant le facteur qui a plus d’impact sur la croissance des tiges de Pericopsis elata. La plantation de recrû (33,21 cm), moins sensible à l’effet de la densité en termes de croissance comparée aux plantations des grands layons (26,91 cm et 26,89 cm), enregistre les meilleures performances de croissance en diamètre. Ainsi, des travaux d’entretien et des éclaircies portées vers une réduction considérable des compétitions interspécifique et intra spécifique sont nécessaires.Mots clés : Indice de Hegyi, méthodes sylvicoles, modes de compétition, plantations équiennes, semi-variogramme, Cameroun.   English Title: Characterization of the competition and growth of Pericopsis elata (Harms) Van Meeuven in the plantations of the Deng-Deng Forest Reserve (East, Cameroon)Pericopsis elata is a valuable woody species threatened with extinction. The Assamela plantations established in the Deng-Deng Forest Reserve in 1974 were abandoned after their establishment. As a result, very little knowledge about the development of these stands is available. The objective of the present study is to contribute to the understanding of the growing conditions of Pericopsis elata in the Reserve and to induce proper management. Three exhaustive inventories were conducted, during which dendrometric data were collected. Hegyi’s competition indices, variograms and spatial distribution of stems were developed. Current densities have no limiting effect on stem growth. Environmental effects were found to be the factor that had the greatest impact on the growth of Pericopsis elata stems. The recruiting plantation (33.21 cm), which is less sensitive to the effect of density in terms of growth compared to the large layon method (26.91 cm and 16.89 cm), has the best growth in diameter performance. Thus, maintenance work and thinning leading to a considerable reduction in interspecific and intraspecific competition is necessary.Keywords: Regular plantations, Hegyi’s competition index, mode of competition, Silvicultural methods, semi-variogram, Cameroon. &nbsp

Assessment of in situ nest decay rate for chimpanzees (Pan troglodytes ellioti Matschie, 1914) in Mbam-Djerem National Park, Cameroon : implications for long-term monitoring

Accurate assessment of great ape populations is a prerequisite for conservation planning. Indirect survey methods using nest and dung, and a set of conversion parameters related to nest decay rates, are increasingly used. Most surveys use the standing crop nest count (SCNC) method, whereby nests are counted along transects and the estimated nest density is converted into chimpanzee density using an often non-local nest decay rate. The use of non-local decay rate is thought to introduce substantial bias to ape population estimates given that nest decay rates vary with location, season, rainfall, nest shape, and tree species used. SCNC method has previously been applied in Mbam-Djerem National Park (MDNP) in Cameroon, for chimpanzee surveys using a non-local nest decay rate. This current study aimed to measure a local nest decay rate for MDNP and implications for chimpanzee population estimates in the MDNP. The mean nest decay rate estimated using a logistic regression analysis was 127 [95% CI (100-160)] days. Moreover, the results suggested that rainfall strongly infuenced the nest decay rate over the early stage of the lifetime of the nests. The study confrms that estimates of chimpanzee density and abundance using non-local decay rates should be treated with caution. Our research emphasized the importance of using local nest decay rates and other survey methods which do not depend on decay rates to obtain more accurate estimates of chimpanzee densities in order to inform conservation strategies of these great apes in MDNP

Mapping/assessing carbon stocks in the perspective of Payment for Environmental Services (PES) for rural communities in East Cameroon

Rural Africa plays an important role in the stabilization of the world's climate. Given that greenhouse gases are emitted from different sources and places, they accumulate over time and mix globally. Climate change can then be effectively tackled if collective actions are taken at global level. Though most decisions are taken by international conservation organizations, the implimetations are done at rural levels by local and indegenous communities who direclty depend on forest products. Reason why carbon stocks assessment at the MPEMOG Community Forest was done in order to establish a reference level for emission-reduction in the perspective of Payment for Environmental Services (PES) using the Chave et al. (2014) non-destructive allometric equation. From analysis of variance, carbon stock varied from 53.48±36.17 Ct/ha to 218.29±308.38 Ct/ha in Mixed cropland and Primary forest respectively equally the conversion of Primary Forest to Mixed cropland leads to the highest carbon loss (166.24 Ct/ha) and Cocoa plantations generate both economic and ecological values and contribute significantly to food security. The study concludes that the variation in carbon stocks depends on the degree of human influence and PES is an opportunity to contribute in forest sustainability while improving on the socioeconomic development of forest dependent populations

The relationship between the abundance of the Nigeria-Cameroon chimpanzee (Pan troglodytes ellioti) and its habitat: a conservation concern in Mbam-Djerem National Park, Cameroon

Background Understanding the relationship between great apes and their habitat is essential for the development of successful conservation strategies. The chimpanzee Pan troglodytes ellioti is endemic to Nigeria and Cameroon, and occupies an ecologically diverse range of habitats from forests to forest-savannah mosaic in Mbam-Djerem National Park (MDNP) in Cameroon. The habitat variation in chimpanzees is poorly understood in MDNP which provides an excellent opportunity to assess ecological factors that shape the abundance and distribution patterns of P. t. ellioti over a small geographic scale. Results We counted 249 nests along 132 km of transects in total. Of these, 119 nests along 68 km occurred in dense forest and 130 nests along 64 km in forest-savannah mosaic. Chimpanzee density was 0.88 [95% CI (0.55–1.41)] individuals/km2 in the dense forest and 0.59 [95% CI (0.19–1.76)] in the forest-savannah mosaic. Nest abundance varied with vegetation type and was higher in areas with dense canopy cover, steeper slopes and relatively higher altitudes. Conclusions Our estimates of chimpanzee densities were lower than reported in other studied populations in the range of the Nigeria-Cameroon chimpanzee. However, we found that habitat features, slope and altitude likely play a role in shaping patterns of chimpanzee nesting ecology. Further studies need to be focused on nest decay rates and phenology of useful plants in order to model chimpanzee abundance and distribution in Mbam-Djerem National Park

Déterminants de la gouvernance forestière dans les forêts communautaires de l’Est-Cameroun

Au Cameroun, les communautés locales font face à des défis de gouvernance forestière et de propriété des forêts communautaires. Les déterminants du succès de la gouvernance forestière ont été étudiés dans douze forêts communautaires (FC) de l’Est-Cameroun. Des groupes de discussion et des entrevues individuelles ont permis de réaliser la cartographie des acteurs d’appui, de documenter la perception de la gouvernance des forêts communautaires et d’en identifier les déterminants, pour ensuite proposer une échelle de gouvernance des forêts communautaires. Les résultats montrent que les acteurs d’appui influencent grandement la création des forêts communautaires. L’exception de la FC A3 montre qu’une communauté peut créer une forêt communautaire sous la seule impulsion du chef traditionnel, sans soutien extérieur. La perception de la gouvernance forestière par les communautés était positive lorsque l’appui à la création de la forêt communautaire provenait d’acteurs tournés vers la communauté (organisations non gouvernementales, administration des forêts et Église) et négative lorsque l’appui provenait d’acteurs tournés vers la ressource ligneuse (élites et opérateurs forestiers privés). Le diagramme des déterminants relationnels entre communautés et acteurs d’appui, basé sur la cohésion entre les principes de gouvernance (participation, transparence, légitimité, équité, intégration, imputabilité, capacité et adaptabilité), met en évidence les actions correctives possibles pour mieux tenir compte des besoins des communautés afin d’atteindre la dévolution sur l’échelle de la gouvernance

Assessing Conservation Values: Biodiversity and Endemicity in Tropical Land Use Systems

Despite an increasing amount of data on the effects of tropical land use on continental forest fauna and flora, it is debatable whether the choice of the indicator variables allows for a proper evaluation of the role of modified habitats in mitigating the global biodiversity crisis. While many single-taxon studies have highlighted that species with narrow geographic ranges especially suffer from habitat modification, there is no multi-taxa study available which consistently focuses on geographic range composition of the studied indicator groups. We compiled geographic range data for 180 bird, 119 butterfly, 204 tree and 219 understorey plant species sampled along a gradient of habitat modification ranging from near-primary forest through young secondary forest and agroforestry systems to annual crops in the southwestern lowlands of Cameroon. We found very similar patterns of declining species richness with increasing habitat modification between taxon-specific groups of similar geographic range categories. At the 8 km2 spatial level, estimated richness of endemic species declined in all groups by 21% (birds) to 91% (trees) from forests to annual crops, while estimated richness of widespread species increased by +101% (trees) to +275% (understorey plants), or remained stable (- 2%, butterflies). Even traditional agroforestry systems lost estimated endemic species richness by - 18% (birds) to - 90% (understorey plants). Endemic species richness of one taxon explained between 37% and 57% of others (positive correlations) and taxon-specific richness in widespread species explained up to 76% of variation in richness of endemic species (negative correlations). The key implication of this study is that the range size aspect is fundamental in assessments of conservation value via species inventory data from modified habitats. The study also suggests that even ecologically friendly agricultural matrices may be of much lower value for tropical conservation than indicated by mere biodiversity value