Dynamique et services des écosystèmes agroforestiers autour d'une aire protégée du Cameroun

Authors: Djiongo Boukeng, Jose Elvire
Advisor: Khasa, Phambu; Avana Tientcheu, Marie Louise
Abstract: Agroforestry is a dynamic system of ecological management of renewable natural resources for biodiversity conservation in both tropical and temperate regions. In addition to ensuring connectivity between protected areas and inhabited areas, it could provide ecosystem services and reduce pressure on forest resources. This study was conducted in and around the Bouba Ndjidda National Park (BNNP) in the Sudano-Sahelian zone of Cameroon in Central Africa. The objectives of the study were: i) to analyse the spatio-temporal dynamics of land use in the BNNP as well as the determining factors of changes; ii) to determine the structural characteristics and uses of woody species in agroforestry systems (AFS); and iii) to evaluate the carbon stocks in the AFS around the BNNP. Using satellite images from 1990, 1999 and 2016, land cover maps were produced using the maximum likelihood supervised classification method. Field validation of the different land use classes coupled with socioeconomic data was carried out to corroborate the cartographic results. A total survey of woody trees in the AFS was then carried out and dendrometric and ethnobotanical data collected. Finally, carbon stock measurements were carried out at the level of above-ground biomass, underground biomass, and soil. For soil carbon, soil samples were taken from 37 plots of 50 x 50 m distributed across 17 dispersed trees on cropland, 10 fallows, 6 home gardens and 4 lives fences. Diversity indices and carbon stock measurements were analyzed using linear mixed models and Tukey or Kruskal-Wallis multiple comparison tests where necessary. The main results show that in 1990, the most important land use classes in and around the BNNP were woody savannah (42.9%), gallery forest (20.2%) and clear forest (16.3%). Between 1990 and 2016, there was an increase in fields from 2.2 to 6.3% at the expense of other types of land use. At the time of the study, these fields around the BNNP were made up of AFS, essentially dispersed trees on cropland (98%). The AFS contain an average floristic richness of 50 species belonging to 23 families, the dominant one being the Fabaceae (62.4%), mainly represented by Acacia polyacantha. Two species on the International Union for the Conservation of Nature (IUCN) Red List were among the woody species listed. These are Vitellaria paradoxa and Khaya senegalensis. Farmers used AFS woody species mainly as fuel wood (66.5%) and as a source of food (63.5%). Total carbon stocks ranged from 26.9 ± 4.9 t C/ha for fallows land to 31.9 ± 7.7 t C/ha for life fences, but no significant difference was found between carbon stocks according to the types of AFS. Soil carbon averaged 31-59% of total carbon and decreased significantly with soil depth (Kruskal-Wallis test, p = 0.009). In terms of payments for environmental services, AFS carbon stock prices were estimated at between 986 and 1170$ US/ha depending on the system. The results of this thesis show that the evolutionary dynamics in favour of agroforestry fields around Sudano-Sahelian protected areas contributes to the provision of ecosystem services. The study therefore suggests that such systems should be promoted and intensified to increase their capacity to provide these services for the socio-ecological systems around protected areas known to be highly vulnerable to anthropogenic pressure.
Document Type: Thèse de doctorat
Issue Date: 2021
Open Access Date: 8 February 2021
Permalink: http://hdl.handle.net/20.500.11794/68067
Grantor: Université Laval
Collection:Thèses et mémoires

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