Louis Zapfack

The impact of land conversion on plant biodiversity in the forest zone of Cameroon

Floristic surveys were carried out in different land use systems(primary and secondary forest, fallows of different ages, cocoa plantations,crop fields) within the forest zone of Cameroon, to assess the impact of landconversion on above-ground plant biodiversity. Beside various diversity studies,plant density was measured and diameter at breast height was estimated.The results showed that the forest areas, which represent thehistoric biodiversity of the region, preserve the greatest number of species(160 species in primary forest and 171 in secondary forest). Our resultsindicate the relatively great importance of secondary forests as refuge areasfor primary forest plant species that may function as a starting point forpossible regeneration of original biodiversity. Species richness is reducedprogressively from the original forest (160 spp.) and secondary forests (171spp.), to Chromolaena odorata (Asteraceae) fallow fields(149 spp.), to an old fallow field (139 spp.), to a cocoa plantation (116 spp.)and to the farmland (64 spp.), where only weeds and crops contribute essentiallyto plant biodiversity. Also the number of species that are used for non-timberproducts (construction, food and medicines) decreased with increased landconversion.

On the delineation of tropical vegetation types with an emphasis on forest/savanna transitions

Background: There is no generally agreed classification scheme for the many different vegetation formation types occurring in the tropics. This hinders cross-continental comparisons and causes confusion as words such as ‘forest’ and ‘savanna’ have different meanings to different people. Tropical vegetation formations are therefore usually imprecisely and/or ambiguously defined in modelling, remote sensing and ecological studies. Aims: To integrate observed variations in tropical vegetation structure and floristic composition into a single classification scheme. Methods: Using structural and floristic measurements made on three continents, discrete tropical vegetation groupings were defined on the basis of overstorey and understorey structure and species compositions by using clustering techniques. Results: Twelve structural groupings were identified based on height and canopy cover of the dominant upper stratum and the extent of lower-strata woody shrub cover and grass cover. Structural classifications did not, however, always agree with those based on floristic composition, especially for plots located in the forest–savanna transition zone. This duality is incorporated into a new tropical vegetation classification scheme. Conclusions: Both floristics and stand structure are important criteria for the meaningful delineation of tropical vegetation formations, especially in the forest/savanna transition zone. A new tropical vegetation classification scheme incorporating this information has been developed.

Biodiversity and spatial distribution of vascular epiphytes in two biotopes of the Cameroonian semi-deciduous rain forest

The diversity and spatial distribution of vascular epiphytes were surveyed in two biotopes (dryland forest and swamp-inundated forest) of the semi-deciduous rain forest area in Cameroon. Eight sites in each biotope were selected, which included 530 individuals of phorophytes in dryland forest and 460 in swamp-inundated forest. A total of 148 epiphyte species were recorded, which showed that semi-deciduous rain forests represent a major source of African-epiphyte diversity. Dryland forest hosted 110 epiphyte species, while the swamp-inundated forest harboured 108. A total of 56 species were found only in the dryland forest and 60 were restricted to the swamp-inundated forest. At family level, Orchidaceae exhibited the highest-species richness within both biotopes. Pteridophytes were more abundant in the swamp-inundated forest. A TWINSPAN analysis of the floristic similarities separated the two investigated forest types very clearly. No significant difference existed between the two biotopes regarding vertical distribution of epiphytes within single trees. The swamp-inundated forests may serve as a refuge for many epiphytes that occur in the outer canopy of the dryland forests, both because they are inherently less vulnerable to timber extraction, and enjoy better protection by legislation.

Distribution et richesse taxonomiques des épiphytes de quelques phorophytes au Parc national de Korup (Cameroun)

Les 50 ha de la parcelle permanente établie par le Smithsonian Institutes (Korup Forest Dynamics Plot: KFDP) ont constitués la surface d’étude. Un total de 100 phorophytes appartenant à 5 espèces soit 20 individus par espèce choisie a fait l’objet d’échantillonnage suivant la méthode de Johansson [1]. Des échantillons récoltés indifféremment sur les autres phorophytes de cette parcelle ont permis d’avoir une idée de la flore épiphytique de ce Parc. Au total, 154 espèces dont 19 Ptéridophytes représentant 12,33 % de la flore, 10 Dicotylédones représentant 6,49 % de la flore et 125 Monocotylédones avec 81,17 % des espèces ont été récoltées. Nos investigations révèlent 9 familles et 46 genres. Les plus abondants sont les Orchidaceae (66,23 % des espèces), les Araceae (14,94 % des espèces), les Polypodiaceae (5,84 % des espèces) et les Begoniaceae (5,19 % des espèces). Au niveau genérique, Bulbophyllum est le plus abondant. Il représente 22,07 % de la flore. D’autres genres importants sont Polystachya, Culcacia et Angraecum. L’analyse canonique de la flore de ces cinq espèces supports, montre que Oubanguia alata, Cola praecuta et Strephonema pseudocola présentent une similitude floristique. La distribution verticale des espèces indique que les niveaux II, III et IV de Johansson [1] sont les plus représentés en terme d’abondance épiphytique. Mots clés: Flore; phorophyte; épiphyte; distribution et abondance The study of vascular epiphytic flora of Korup National Park has been carried out in 50 hectares of the Korup Forest Dynamics Plot (KFDP). The sampling used Johansson’s method [1] of over 100 phorophytes belonging to five species of which each species is made up of 20 individuals of the same species. A collection was made through KFDP. It was noted that a total of 154 species where 19 Pteridophytes (12.33 %), 10 Dicotyledons (6.49 %) and 125 Monocotyledons (81.17 %) were thus registered. These epiphytes were divided into nine families and 46 genera. The families of greater abundance are Orchidaceae with the species of 66.23%, Araceae with the species of 14.94% and Polypodiaceae with the species of 5.84%. Other important family is Begoniaceae with the species of 5.19%. The genus Bulbophyllum is the most abundant; it is represented by the species of 22.07%. The analysis of flora, thanks to the statistical test, shows that Oubanguia alata, Cola praecuta and Strephonema pseudocola are floristically the same. The vertical distribution shows that, the II, III and IV levels of Johansson [1] are those mostly represented.

Woody species composition, structure and diversity of vegetation of Kalfou Forest Reserve, Cameroon

Studies were carried out in the Kalfou Forest Reserve to make an assessment of the flora diversity and to develop preservation guidelines facing the increase in its degradation. The composition of woody species, structure, diversity, density, dominance, frequency of species and family importance value were described and evaluated in all the forest reserve area. A total of 86 species representing 58 genera and 28 families of woody species were identified. The families of Combretaceae, Fabaceaecaesalpinioideae and Fabaceae-mimosoideae were the most abundant families in the Kalfou Forest Reserve. The density of stems ≥ 10 cm circumference and the basal area were higher in the Doulouk and Gonoray parts of the reserve. The distribution of stems of the main species in classes of circumference had shown a reverse “J” shaped curve. The number of stems of shrubs species was important and strongly influenced globally the diameter and the height of the stems which were lower. Species diversity was a slight difference among the various parts of the forest reserve area. The species abundance showed that, 20% of the species were infrequent. The dynamic of renewal of species were ensured by the weakly regeneration: seedling (2.03%), rejection issues (41.97%) and the death rate of individual species was 8.02%. Disturbances and the vulnerability of the seedlings did not ensure species sustainability. Preservation systems and adequate management were therefore recommended in order to ensure sustainable management of the Kalfou Forest Reserve resources.

Host plants of Stictococcus vayssierei Richard (Stictococcidae) in non-crop vegetation in the Congo Basin and implications for developing scale management options

Surveys were carried out in five vegetation types to identify, in non-crop vegetation, host plants of Stictococcus vayssierei Richard, a pest of cassava in the Congo basin. Along transects within each of these vegetation types, all plants with underground storage structures and including those belonging to the plant families known to be used by S. vayssierei were uprooted and inspected for the presence of the scale. Sixteen plant species belonging to 13 families were identified as hosts of S. vayssierei. Eleven out of the host species are indigenous and 13 are newly identified hosts for S. vayssierei. Six new host families were identified. Infestation levels and the distribution of S. vayssierei indicated that native Dioscorea species may play an important role in the maintenance of the scale in long fallows and in secondary and primary forests, while exotic plants such as cassava may contribute to S. vayssierei population growth in fallows less than eight years old. Our findings suggest that destruction and removal of S. vayssierei host plants from non-crop vegetation might be useful in reducing S. vayssierei infestations and improving cassava yields.

DENSITY AND NATURAL REGENERATION POTENTIAL OF SELECTED NON-TIMBER FOREST PRODUCTS SPECIES IN THE SEMI-DECIDUOUS RAINFOREST OF SOUTHEASTERN CAMEROON

evariste fongnZoSSie feDoung Higher Teacher’s Training School for Technical Education (ENSET), University of Douala marlene ngAnSoP tounKAm louis ZAPfAcK Department of Plant Biology, Faculty of Science, University of Yaounde 1 Victor Aime KemeuZe Department of Plant Biology, University of Ngaoundere Denis Jean SonWA Center for International Forestry Research (CIFOR) guy merlin nguenAng German Cooperation, GIZ-ProPSFE program, Bertoua Cameroon bernard-Aloys nKongmenecK Department of Plant Biology, Faculty of Science, University of Yaounde 1

Height-diameter allometry and above ground biomass in tropical montane forests : insights from the Albertine Rift in Africa

Tropical montane forests provide an important natural laboratory to test ecological theory. While it is well-known that some aspects of forest structure change with altitude, little is known on the effects of altitude on above ground biomass (AGB), particularly with regard to changing height-diameter allometry. To address this we investigate (1) the effects of altitude on height-diameter allometry, (2) how different height-diameter allometric models affect above ground biomass estimates; and (3) how other forest structural, taxonomic and environmental attributes affect above ground biomass using 30 permanent sample plots (1-ha; all trees ≥ 10 cm diameter measured) established between 1250 and 2600 m asl in Kahuzi Biega National Park in eastern Democratic Republic of Congo. Forest structure and species composition differed with increasing altitude, with four forest types identified. Different height-diameter allometric models performed better with the different forest types, as trees got smaller with increasing altitude. Above ground biomass ranged from 168 to 290 Mg ha-1, but there were no significant differences in AGB between forests types, as tree size decreased but stem density increased with increasing altitude. Forest structure had greater effects on above ground biomass than forest diversity. Soil attributes (K and acidity, pH) also significantly affected above ground biomass. Results show how forest structural, taxonomic and environmental attributes affect above ground biomass in African tropical montane forests. They particularly highlight that the use of regional height-diameter models introduces significant biases in above ground biomass estimates, and that different height-diameter models might be preferred for different forest types, and these should be considered in future studies.

Floristic structure and sequestration potential of cashew agroecosystems in Africa: A case study from Cameroon

ABSTRACT Agroecosystems are not only recognized by their high capacity of carbon storage and sequestration, they could also offer an opportunity of financial benefits in the event of payment for environmental services. The present study aimed to evaluate the carbon storage and describe the structure of cashew nut plantation. Three types of cashew stand were selected according to the age of plantations; we also used savannah as a treatment witness. Carbon stocks varied according to the age of plantations; 14.51 ± 0.306 t C/ha for plantations aged 0–10 yr; 34.78 ± 0.331 t C/ha for plantations aged 10–20 yr, and 40.02 ± 0.381 t C/ha for plantations aged over 20 yr. In the witness, we found 13.05 ± 0.177 t C/ha. These values were significantly different between the studied sites (p < 0.05). The mean values of the service of carbon sequestration also varied with the age of stands;

Community of vascular epiphytes on some phorophytes in the Babadjou Subdivision (Western Cameroon): Case of Bamelo

53.5/ha/yr (0–10 yr);