Fragmentation is the main driver of residual forest aboveground biomass in West African low forest-high deforestation landscapes
Soulemane Traoré, Irié C. Zo‐Bi, Camille Piponiot, Raphaël Aussenac, Bruno Hérault
Abstract
Tropical forests play a crucial role in climate regulation due to their high carbon sequestration capacity. However, degradation and disturbances in these forests may result in significant carbon losses. This study focuses on the impact of various biophysical, anthropogenic, and landscape factors on aboveground biomass (AGB) in heavily disturbed landscapes of Côte d'Ivoire (West Africa), a typical low-forest and high-deforestation country. AGB estimates from a National Forest Inventory dataset have been linked to five categories of variables (Climate, Soil, Topography, Landscape, and Human-related) through a random forest modeling approach that addressed collinearity among variables, selected key variables from each category, and used spatial cross-validation to evaluate model performance. The comprehensive model, combining landscape composition, physical soil properties, and climate variables, demonstrated strong performance with an R-squared of 0.62. Notably, the percentage of landscape occupied by forest within a radius of 1000m (PLAND1000) had a highly significant impact on AGB, exhibiting a notable increase when PLAND1000 exceeded 80% and a decrease when it felt below 25%. Soil properties, both physical (Bulk Density and Coarse Fraction) and chemical (soil pH), significantly influenced AGB, too. Interestingly, climatic, topographic, and other anthropogenic variables had minimal relevance in predicting AGB, suggesting that their effects may have been captured by landscape and soil integrative variables. In order to enhance forest preservation and restoration initiatives in the face of deforestation and fragmentation challenges in the West African region, we recommend (i) evaluating the appropriate landscape scale of effect (a 1000m radius circle being the most significant in this study); (ii) prioritizing the preservation or restoration of dense forest landscapes; and (iii) integrating landscape composition into forest management policies.