Ecologie et régénération naturelle des espèces à produits forestiers non ligneux de la périphérie du parc national de Boumba-bek, Sud-est Cameroun

Abstract

Non-Timber Forest Products (NTFPs) represent many good and services benefical for the livelihood of the populations who depend on them. However, the sustainable management of their population is limited by the little knowledge on their available potential, distribution and regeneration dynamics in their ecosystems. However, this information is essential for their sustainable use, especially near Protected Areas whose creation gives regulated access to the natural resources. This study assessed the natural regeneration status of eight major NTFPs species (Afrostyrax lepidophyllus, Baillonella toxisperma, Irvingia gabonensis, Panda oleosa, Pentaclethra macrophylla, Ricinodendron heudelotii, Scorodophloeus zenkeri and Tetrapleura tetraptera) according to their frequency of utilization and commercialization near Boumba-bek National Park, South-East Cameroon. Linear transects sampling design was used and these transect were placed on both side of a 16 km baseline. Sampling was carried out on 16 transects of 5000 m long by 20 m wide with 1 km equidistant. Habitat types were characterized along transects following the basic forest classification system used in ecology. For each species, all the seedlings to individuals of DBH ≥ 5 cm, were identified and georeferenced. The population distribution of each species by class diameter was used to characterize their structure. Spatial methods using Geographic Information System (GIS) and the spatial distribution model of Dajoz were used to describe the spatial distribution of natural regeneration. The study of spatiotemporal dynamics of NTFPs harvesting was used to evalued the impact of harvesting on natural regeneration of NTFPs species. A total of 13 habitat types were identified, of which the young secondary forests and periodically floodable forests were the most represented 32.70% and 26.31% respectively. The least represented habitat was young fallows with Chromolaena odorata (0.08%). Seven of the eigth species were predominantly represented in young secondary forests, only S. zenkeri was more abundant in the young secondary forests with Marantaceae. High density species were A. lepidophyllus (32.0 ± 26.1 stems / ha), P. macrophylla (11.3 ± 8.2 stems / ha), R. heudelotii (10.3 ± 18.5 stems / ha) and S. zenkeri (7.4 ± 12.8 stems / ha). The diametric structure and spatial distribution of these species shows that they have high regeneration potentials at equilibrium and are distributed in aggregates. Low densities were recorded for P. oleosa (2.1 ± 1.0 stems / ha), I. gabonensis (1.9 ± 1.6 stems / ha), T. tetraptera (0.9 ± 0.8 stems / ha) and B. toxisperma (0.1 ± 0.1 stems / ha). Their diametric structures combined with their spatial structure permit to characterize them as species with low regeneration potentials and random distribution, except for B. toxisperma which showed uniform distribution and I. gabonensis, which showed aggregated distribution with a non-significant unit deviation. Overall, the best area with a high density of individuals of these eight NTFPs species was within 8 km from the village. The harvesting of fruits and seeds of these eight NTFPs species takes place throughout the year. The most collected NTFPs were respectively the kernels of I. gabonensis (68.12%), seeds of P. macrophylla, kernels of R. heudelotii (11.0%), and seeds of A. lepidophyllus (7.64%). The main collection camps were concentrated in the Forest Management Unit (FMU) 10-018 and close to the Park, representing the areas in which NTFPs species indicate poor natural regeneration. It is known that intensive collection negatively affects the availability of NTFPs species that are highly exploited by local communities. This intensive collecting activity justifies the low densities of young individuals observed beyond the 8 km from the village. Generally, the fruits of the targeted NTFPs species are being disseminated by frugivorous, therefore the harvest of almost all fruits by humans limit the action of the frugivorous, therefore main disseminators of these NTFPs, thus negatively affects their natural regeneration. The periphery of Boumba-bek National Park is much diversified in terms of habitat with a high proportion of secondary forests, indicating an advanced secondary state. However, the different types of young secondary forest appear to be favorable for the growth of the eight NTFPs species studied. The pressure due to fruit harvesting, combined with the scarcity of P. oleosa, I. gabonensis, T. tetraptera and B. toxisperma, highlights them as species in need of protection and domestication. To ensure the sustainability and management of the eight NTFP species identified this study, it is essential to promote their domestication, particularly in young secondary forests and agro-ecosystems. This would increase the availability of resources and the diversification of sources of income and thus contribute to the well-being of local communities at the periphery of the Boumba-bek National Park.