Affinité des mycorhizes arbusculaires et diversité ligneuse dans les parcelles permanentes de la réserve de faune du Dja

Abstract

Tropical soils are known to be poor in macroelements, and the diversity of species that make them up develop mycorrhizal associations to better fix macroelements not directly accessible to root systems. This mechanism influences the floristic diversity of forest stands. The aim of this study was to determine the affinity between endomycorrhizae and wood diversity in permanent plots in the Dja wildlife reserve. The methodological approach consisted in carrying out a floristic inventory of woody species with diameters ≥ 10 cm in five 100 m x 100 m plots. This woody flora was characterized on the basis of diversity indices and plant type. To determine the type of associated mycorrhizae, rootlet samples were taken, cleaned, stained and examined under a microscope to identify the species that form the mycorrhizae. A total of 196 woody species belonging to 144 genera and 43 families were recorded in the study area. The Shannon, Simpson and Fisher-α index values are 4.43; 0.98 and 51.77 respectively. The average basal area found was 30.53 m2/ha, with ecologically important species such as Petersianthus macrocarpus (18.24), Tabernaemontana crassa (9.13), Desbordesia glaucescens (9.06), Carapa procera (8.00) and Uapaca guineensis (7.15). Of the 98 species whose fine roots were sampled, 74 (75.51%) formed mycorrhizal associations. Mycorrhization infection showed that mycorrhization intensity was highest in the Allanblackia floribunda (64.25%). Mycorrhization frequency was 100% for species such as Allanblackia floribunda, Antidesma membranaceum, Beilshmiedia obscura, Monodora tenuifolia and Pycnanthus angolensis. In terms of family, this frequency was highest in the Lauraceae (19%). However, analysis of the results shows that mycorrhization is not species-specific. One species may mycorrhize on one stem, but not on another. The majority of forest species showed strong endomycorrhizal infection in the ecosystem.