Status of non-cocoa tree species in cocoa multistrata systems of southern

Investigations to assess the status of non-cocoa tree species in the cocoa systems of southern Cameroon were carried out in four contrasting locations, distinguished by ecology, population density and land use intensity. One set of inventory was done in each of the 20 selected cocoa farms with an average surface area of 1.4 ha in every location. The inventory was carried out over 25% of each farmland following a gradient directed transect method. Within each cocoa farm, only indigenous tree species and shrubs with the capacity of being transformed into tree species were considered. Our findings showed that there was in total 165 different non-cocoa tree species in the 80 cocoa fields observed. The number of shared species between locations was relatively high (54% to 74%). Frequency distribution of the number of species classified by the number of farms where they were found showed that most species were fairly rare. Tree species richness varied widely between cocoa farms within locations. These findings suggest the need for the various stakeholders of the sector to take appropriate actions to protect endangered species of ecological and economical importance in order to enhance the sustainability of these systems. Keywords: Species diversity, cocoa systems, land use, sustainability. International Journal of Biological and Chemical Sciences Vol. 2 (2) 2008: pp. 207-21

Soil structure of an Oxisol as influenced by land use systems in the forest margin zone of Southern Cameroon

Soil structure is the key for controlling soil quality. To assess changes in soil structure and its related indices under different land-use systems, an on-farm investigation was carried out on an Oxisol of Southern Province of Cameroon. Six land-use systems (LUS) consisting of a primary forest, a 30-year old secondary forest, a 25-year old cocoa field, a 15-year old natural fallow, a 3- year old Chromolaena odorata fallow and a 2-month old groundnut (Arachis hypogea) field were tested. Soil samples were collected at 0-5 and 5-10 cm depths and were used to determine particle size distribution (hydrometer method), bulk density and aggregatestability. Soil resistance to penetrometer was measured at the same depths in the field using a hand penetrometer. It was found that the primary forest and the cocoa field were associated with highest claycontents (74.6 and 52.0%, respectively) compared to other LUS. However, bulk density was significantly higher under cocoa field (1.09-1.26 g.cm-3) as compared to primary forest (0.72-0.89 g.cm-3). Soil resistance topenetrometer was the lowest under forests (1.2 - 5.2 bars) as compared to cropped fields (9 -12.5 bars) at 0-5 cm depth. Similar trend was observed at 5-10 cm depth. The proportion of aggregates less than 2 mm indiameter was the least under primary forest (27%) as compared to groundnut field (52%). In contrast, soil aggregates under primary forest and cocoa field were more stable, with the highest mean weight diameter(MWD) of 3.37 and 3.00 mm, respectively.Keywords: Cameroon, humid forest, land use systems, Oxisol, soil structure, structural stability

Termite diversity across an anthropogenic disturbance gradient in the humid forest zone of West Africa

Data are presented for termite assemblages across an anthropogenic disturbance gradient in the humid forest zone of West and Central Africa. Sampling was by standardised 100 mx2 m transects in: primary forest, several ages of regenerating forest, agroforestry plots, short fallows, mixed food crop fields, and mechanically cleared plots. Most sites were in southern Cameroon––two additional transects were conducted in primary forest in Congo (Brazzaville). Species richness was negatively correlated with the disturbance gradient, although transects in areas with a complete or near-complete canopy were broadly similar in species richness. The strongest negative correlation was found for termite species feeding furthest down the humification gradient (group IV soil feeders) probably because these species are energetically constrained from living in non-forest habitats. In contrast species feeding and nesting in dead wood (group I wood feeders) termites, which live in the most protected micro-habitats, were significantly positively correlated with the disturbance gradient. Species composition was also strongly correlated with disturbance level in multivariate redundancy analyses. Pest species were an insignificant element of the assemblage, in part because of the distance of the sites from savanna source pools. Overall, it appears that termite-mediated wood and litter decomposition may be relatively unaffected by light to moderate disturbance intensity, but that soil-conditioning by termites might be greatly reduced in agricultural land cleared from tropical forest

Termite diversity across an anthropogenic disturbance gradient in the humid forest zone of West Africa

Data are presented for termite assemblages across an anthropogenic disturbance gradient in the humid forest zone of West and Central Africa. Sampling was by standardised 100m × 2m transects in: primary forest, several ages of regenerating forest, agroforestry plots, short fallows, mixed food crop fields, and mechanically cleared plots. Most sites were in southernCameroon—two additional transects were conducted in primary forest in Congo (Brazzaville). Species richness was negatively correlated with the disturbance gradient, although transects in areas with a complete or near-complete canopy were broadly similar in species richness. The strongest negative correlation was found for termite species feeding furthest down the humification gradient (group IV soil feeders) probably because these species are energetically constrained from living in non-forest habitats. In contrast species feeding and nesting in dead wood (group I wood feeders) termites, which live in the most protected micro-habitats, were significantly positively correlated with the disturbance gradient. Species composition was also strongly correlated with disturbance level in multivariate redundancy analyses. Pest species were an insignificant element of the assemblage, in part because of the distance of the sites from savanna source pools. Overall, it appears that termite-mediated wood and litter decomposition may be relatively unaffected by light to moderate disturbance intensity, but that soil-conditioning by termites might be greatly reduced in agricultural land cleared from tropical forest