47 research outputs found

    Pentaclethra macrophylla Benth. dans la forêt communautaire de Payo (Est- Cameroun): inventaire, productivité et commercialisation

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    Cette etude a ete conduite a l'Est du Cameroun, dans la foret   communautaire de Payo. Elle a pour objet d'evaluer l'importance   ecologique, productive et socioeconomique de P. macrophylla. Le dispositif d'inventaire est constitue de quatre transects de 40 m x 2000 m2 (8 ha chacun) avec un taux de sondage de 2%. Toutes les tiges de diametre a hauteur de poitrine .10 cm ont ete marquees, georeferencees, comptees et leur diametre mesures a la hauteur 1,30 cm. Les observations et entretiens, ainsi que le suivi de la filiere de commercialisation ont ete realises a Payo puis dans la ville de Lomie. L'espece est abondante dans les forets secondaires jeunes avec une densite de 6 tiges/ha. Le diametre moyen et la surface terriere des tiges recencees sont respectivement  estimes a 56,91 ± 14 cm et 19,46 m2/ha. Lfindice de regeneration   naturelle est evalue a 4,8 et influence par lfintensite lumineuse qui   parvient dans le sous bois. La production de 35 arbres pour une saison de fructification est estimee a 5 157 graines soit en moyenne 147,34  graines/arbre. La production annuelle est estimee a 1 261 255 graines  equivalant a 11 571 combo (unite de mesure locale). La valeur marchande de ces graines est estimee a 5 785 572 Frs CFA (11836 $US).   Lfexploitation des graines de P. macrophylla represente ainsi de bonnes perspectives de revenus pour cette localite.Mots cles : Production, commercialisation, Pentaclethra macrophylla, foret communautaire

    Predominant melliferous plants of the western Sudano Guinean zone of Cameroon

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    Between September 2003 and March 2005, melissopalynological methods were used to access the predominant melliferous plants (PMP) in 104 honey samples collected from the Soudano Guinean highlands zone of west Cameroon. A total of 19 PMP from 11 families were identified, Asteraceae is the most represented. Trees and herbs were frequently exploited. Spontaneous PMP were more represented. Perennial PMP were highly visited by Apis mellifera adansonii. PMP with white colour flower are the most utilized by bees compared to other colours. When seasonal exploitation was considered, the proportion of PMP exploited in the rainy season was higher. Eucalyptus saligna, Terminalia mantaly and Pterocarpus soyauxii were frequently exploited.Key words: Apis mellifera adansonii, melliferous plant, predominant, harvested

    Diversité floristique sous canopée en plantation forestière de Mangombe-Edea (Cameroun)

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    Floristic diversity under canopy in forest plantation of Mangombe-Edea (Cameroon). Trees plantation of Mangombe is situated in rain forest of low altitude. Six plots among which one of Mansonia altissima (A.Chev.) A.Chev., 2 of Lovoa trichilioides Harms, 3 of Terminalia ivorensis A.Chev. and one perturbed natural forest are concerned by this study. The work consisted to the evaluation of the floristic diversity under canopy in order to appreciate the influence of forest plantation on natural regeneration. A total of 26 families, 42 genders and 46 species were censured. Meliaceae and Apocynaceae are present in all the plots. In plot one of T. ivorensis, M. altissima and natural forest, the low value of equitability of Pielou traduces the dominance of flora by few species and the transitory situation of the ecosystem. On contrary the rest of plots present a good repartition of individuals among the species. One can notice a weak organization of the ecologic system in M. altissima plot, this corresponds to favourable conditions of environment for installation of many species represented by a few number of individuals. Shannon indices, relatively low in plot one of T. ivorensis characterize an ecosystem where one species is dominant. Globally, the regeneration under canopy is reconstituted progressively and remains less diversified than the nearest natural forest. Creation of genetic pool through selective entertainment under canopy will permit polycyclic management of plots for sustainable production of wood

    Afforestation/Reforestation Based on Gmelina Arborea (Verbenaceae) in Tropical Africa: Floristic and Structural Analysis, Carbon Storage and Economic Value (Cameroon)

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    The study was carried out in three selected plantations. Sampling was made infive 100x20 m2 plots per site. Overall, 32 species, 36 genera and 17 families were surveyed. Hymenocardia acida, Combretum adenogonium, Daniellia oliveri, Entada africana, Terminalia macroptera, T. laxiflora, Lannea schimperi, Lophira lanceolata, Maytenus senegalensis, Ochna schweinfurthiana, Protea madiensis, Psorospermum senegalense, Piliostigma thonningii, Sarcocephalus latifolius and Securidaca longepedunculata were the most important species. The richness index ranged from 2.53±0.05-7.74±0.03. Shannon index was 3 in all sites. Density ranged from 98±2.01-253±10.23 stems/ha. Basal area was statistically significant among the sites (p70 %). The vertical structure showed three types of figures; L shape, symmetrical bell shape and unsymmetrical bell shape. These structures confirmed a good regeneration of timbers in the sites. There was a positive correlation of the species dispersal in the sites (p<0.001). The amount of AGB was 23.50±0.38 t C/ha. The amount of C sequestration was 86.28±16.57 t CO2eq/ha. The ecosystem service payments ranged between 258.87±24.88-8629.25±248.16 €/ha with the lowest values for CDM price and the highest for REDD+price. A financing of such projects is required in the frame of creating adaptation and attenuation measures to global warming effects

    Moabi (Baillonella toxisperma Pierre): Arbre Ă  usage multiple de forĂŞt dense humide du Cameroun

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    Le Moabi est un grand arbre de la for&#234;t dense humide du Cameroun. Cet arbre &#224; usages multiples, est recherch&#233; par l&#8217;industrie foresti&#232;re pour la qualit&#233; de son bois et par les populations rurales pour ses produits autres que le bois tels l&#8217;&#233;corce et les racines pour leurs importances m&#233;dicinales, les fruits pour la fabrication d&#8217;huile. Ces formes d&#8217;exploitations concurrentielles, tr&#232;s souvent sans soucis de durabilit&#233; ont consid&#233;rablement r&#233;duit les populations d&#8217;arbres, avec pour cons&#233;quence la raret&#233; des produits d&#233;riv&#233;s. Face &#224; cette forte pression anthropique qui s&#8217;exerce sur le Moabi dans le sud Cameroun, il a paru n&#233;cessaire d&#8217;effectuer une &#233;tude socio&#233;conomique et &#233;cologique dans les villages &#224; fortes activit&#233;s d&#8217;exploitation. En effet, la compr&#233;hension des atouts socioculturels et des divers liens et usages que les ruraux tissent autour de cet arbre, l&#8217;estimation des stocks disponibles dans les terroirs villageois est un pr&#233;alable imp&#233;ratif &#224; l&#8217;&#233;laboration des r&#232;gles de gestion durable. Les enqu&#234;tes aupr&#232;s des utilisateurs et les inventaires forestiers ont &#233;t&#233; r&#233;alis&#233;s dans sept villages. La distribution de cette esp&#232;ce est estim&#233;e &#224; 0,8 arbre/ha pour les individus d&#8217;un diam&#232;tre &#224; 1,3 m sup&#233;rieur &#224; 10 cm. Cet arbre rev&#234;t une importance socioculturelle et incarne des pouvoirs divins ind&#233;niables pour 65% des ruraux. Les femmes repr&#233;sentent 56,5% des exploitants des produits forestiers non ligneux issus de cet arbre. Elles sont plus que les hommes, tributaires de l&#8217;exploitation des fruits et des &#233;corces du Moabi. De ce fait, elles sont les principales victimes des conflits d&#8217;int&#233;r&#234;ts. Les &#233;corces et le latex sont utilis&#233;s en pharmacop&#233;e. La production d&#8217;huile &#224; partir des fruits peut g&#233;n&#233;rer jusque 1 050 000 Fcfa de rentr&#233;es financi&#232;res dans le village Melondo. L&#8217;importance de ce gain incite &#224; promouvoir l&#8217;extraction d&#8217;huile de Moabi dans le cadre de la diversification des sources de revenus et de la lutte contre la pauvret&#233;.Mots cl&#233;s: Moabi, usages multiples, gestion soutenue, communaut&#233; rurale, Camerou

    Correlation between Associated Trees, Cocoa Trees and Carbon Stocks Potential in Cocoa Agroforests of Southern Cameroon

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    This study was conducted in the Cocoa Agro-Forests (CAF) of Mengomo’s locality. The aim was to evaluate the influence of some factors on carbon stocks. The sampling was done in 30 plots of 25 x 25 m 2 in which all trees with a dbh?10 cm were inventoried. The Shannon, Simpson and Evernnessindexes were calculated to characterize the diversity of trees associated with cocoa. 62 species belonging to 48 genera and 27 families were identified, the Anacardiaceae, Moraceae, Caesalpiniaceae,  Mimosaceae and Rutaceae, were revealed the most diverse families, with 5 species each. Shannon’s (3.66), Evernness’s (0.76) and Simpson’s (0.96) indexes have reflected a low diversity, dominated by some fewspecies. The average density of cocoa trees is 1028 trees/ha. They store about 22.51±5.86 Mg C/ha. Associated trees stored 124.20±60.05Mg C/ha for tree density of 113 trees/ha. These CAF sequestered about 146.71Mg C/ha. The multiple correspondence analyses showed that carbon stocks in the CAF are positively correlated with the associated trees and the age of the CAF and negatively correlated with the abundance of cocoa trees. The biomass of cocoa is independent of the associated trees, but is inversely related to the density of the associated trees

    Foliar trait contrasts between African forest and savanna trees: Genetic versus environmental effects

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    Journal ArticleVariations in leaf mass per unit area (Ma) and foliar concentrations of N, P, C, K, Mg and Ca were determined for 365 trees growing in 23 plots along a West African precipitation gradient ranging from 0.29 to 1.62m a-1. Contrary to previous studies, no marked increase in Ma with declining precipitation was observed, but savanna tree foliar [N] tended to be higher at the drier sites (mass basis). Generally, Ma was slightly higher and [N] slightly lower for forest vs savanna trees with most of this difference attributable to differences in soil chemistry. No systematic variations in [P], [Mg] and [Ca] with precipitation or between trees of forest vs savanna stands were observed. We did, however, find a marked increase in foliar [K] of savanna trees as precipitation declined, with savanna trees also having a significantly lower [K] than those of nearby forest. These differences were not related to differences in soil nutrient status and were accompanied by systematic changes in [C] of opposite sign. We suggest an important but as yet unidentified role for K in the adaption of savanna species to periods of limited water availability; with foliar [K] being also an important factor differentiating tree species adapted to forest vs savanna soils within the 'zone of transition' of Western Africa.Natural Environment Research Council TROBIT Consortium projectRoyal Society - University Research Fellowshi

    Structural, physiognomic and above-ground biomass variation in savanna-forest transition zones on three continents - How different are co-occurring savanna and forest formations?

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    Through interpretations of remote-sensing data and/or theoretical propositions, the idea that forest and savanna represent "alternative stable states" is gaining increasing acceptance. Filling an observational gap, we present detailed stratified floristic and structural analyses for forest and savanna stands located mostly within zones of transition (where both vegetation types occur in close proximity) in Africa, South America and Australia. Woody plant leaf area index variation was related to tree canopy cover in a similar way for both savanna and forest with substantial overlap between the two vegetation types. As total woody plant canopy cover increased, so did the relative contribution of middle and lower strata of woody vegetation. Herbaceous layer cover declined as woody cover increased. This pattern of understorey grasses and herbs progressively replaced by shrubs as the canopy closes over was found for both savanna and forests and on all continents. Thus, once subordinate woody canopy layers are taken into account, a less marked transition in woody plant cover across the savanna-forest-species discontinuum is observed compared to that inferred when trees of a basal diameter > 0.1 m are considered in isolation. This is especially the case for shrub-dominated savannas and in taller savannas approaching canopy closure. An increased contribution of forest species to the total subordinate cover is also observed as savanna stand canopy closure occurs. Despite similarities in canopy-cover characteristics, woody vegetation in Africa and Australia attained greater heights and stored a greater amount of above-ground biomass than in South America. Up to three times as much above-ground biomass is stored in forests compared to savannas under equivalent climatic conditions. Savanna-forest transition zones were also found to typically occur at higher precipitation regimes for South America than for Africa. Nevertheless, consistent across all three continents coexistence was found to be confined to a well-defined edaphic-climate envelope with soil and climate the key determinants of the relative location of forest and savanna stands. Moreover, when considered in conjunction with the appropriate water availability metrics, it emerges that soil exchangeable cations exert considerable control on woody canopy-cover extent as measured in our pan-continental (forest + savanna) data set. Taken together these observations do not lend support to the notion of alternate stable states mediated through fire feedbacks as the prime force shaping the distribution of the two dominant vegetation types of the tropical lands
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