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The prolific orphan trees in the Cameroon forests

29.04.2003


The Ntumu (the Beti-Fang), live in the equatorial forest in southern Cameroon, in the north of Gabon and of Equatorial Guinea. They practice a semi-nomadic slash-and-burn form of agriculture. Their farming is highly diversified, mainly of food crops (such as cassava, plantain banana, sweet potato, yam and taro) but they also produce cash crops (cacao, groundnuts). When they clear a plot (1 ha on average), the Ntumu systematically spare certain trees, generally about 15 whatever cutting methods or implements they use: chainsaw or axe. Thus, contrary to what is often stated, selective felling is conducted not because the workforce is insufficient or for lack of time. Nor is determined by the hardness of the timber or the exhausting nature of the task. On the contrary, it is a deliberate traditional practice which requires a sophisticated knowledge of the environment and the different types of forest trees. It demands a long learning period.



Why do the Ntumu spare these trees, “orphans of the forest”, as they call them? Investigation of the species preserved reveals that they have a high social, cultural, agronomic and even ecological value in the long term. They are varieties that can provide food or medicinal resources (fruit and seeds), firewood or construction timber or represent prized hunting grounds. Some species, such as the kapok tree also contribute to the habitat’s fertility; their presence improves food production thanks to the humus generated by falling leaves, flowers and fruit as well as the shade they offer for crops. The three species – Ceiba pentandia, Triplochiton scleroxylon and Terminalia superba – which most particularly play this fertilizing role have a high cultural value and hence together represent a third of all protected trees left in the fields.

The orphan trees have, other than their immediate utility in the Ntumu’s subsistence economy, a driving role in forest regeneration when the fields return to fallow. These trees constitute highly attractive sites for seed-dispersing animals (birds, bats, monkeys) which use them to perch or as shelter against predators and sometimes find abundant food in them. In addition, under their crown, the seed density and diversity (over 100 different species1 have been recorded) are clearly higher than for those observed where no such trees remain. Most of these seeds belong to ligneous species (97% as against 60% in open fields)2. The trees isolated in the fields also create a microclimate which favours, or even accelerates, regrowth of forest species. They supply an input of nutrients (leaves, fruit, animal excreta) and increased soil humidity thanks to the shade under the crown. This shade encourages long-life forest tree species. In contrast, in some areas of the open plots, more short-life heliophile pioneer species are found. These species, most often herbaceous, are sometimes invasive. Forest regrowth thus develops more rapidly and intensively under the orphan trees: they act as the nuclei of regeneration which, when they coalesce will contribute to the rapid reconstitution of the forest cover.


At the level of agricultural regime, this ancestral practice favours the maintenance of a forest cover and contributes to the continuation of slash-and-burn agricultural systems. At the landscape level, the farmers have over the centuries, by systematically selecting certain species as they clear forest, oriented the specific diversity of the Cameroon forest towards a greater proportion of useful species, which can become highly valued. This long-term strategy of forest management thus represents one of the many agricultural approaches in which environmental factors are taken into account that forest-dwelling peoples in the tropics have developed.

Marie-Lise Sabrie | alfa
Further information:
http://www.ird.fr

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