Modeling direct and indirect stem density and forest canopy effects on above-ground biomass stocks in Isoberlinia spp woodland

As the demand for renewable energy and forest products continues to rise, the optimal management of subtropical forests raises significant concerns. Natural stands of Isoberlinia spp . have become crucial in meeting these needs. This study aims to evaluate the effects of stem density, forest canopy closure, and diameter heterogeneity on aboveground biomass stocks (AGB) in young and mature natural stands of Isoberlinia spp. Forty 400 m² plots were established in young and mature Isoberlinia spp . stands in the Sudano-Guinean zone of Benin. Forest canopy cover, stem density, and diameters at breast height (DBH) were measured. The AGB was estimated using an allometric model. A structural equation model was developed to analyze the direct and indirect effects of stem density, canopy cover, and the coefficient of variation of DBH on AGB. In young stands (average density 472.50 stems/ha), high stem density had a significantly negative effect on AGB. In mature stands (average density 236.25 stems/ha), high diameter heterogeneity (high coefficient of variation of DBH) significantly reduced the AGB, while a dense forest canopy (67.50%) tended to increase it. The combination of the two stages revealed the importance of reducing density and maximizing forest canopy closure to optimize AGB over time. The results highlight the need to adapt silvicultural practices to the stage of development of the forest, in order to optimize the growth of individual trees to increase the AGB stock, while preserving these Isoberlinia spp . woodlands.