Comparative Analysis of Floristic Diversity in Primary and Secondary Forests at the IFA–Yangambi Experimental Plot, Ituri Forest, D.R. Congo

Background and Objectives: Deforestation and land-use changes pose a major threat to floristic biodiversity in many forests. This study compared floristic diversity between primary and secondary forests at IFA-Yangambi Experimental Forest Plot, Democratic Republic of Congo. Materials and Methods: Floristic assessments were conducted in eight plots of 100×25 m, four in primary forest and four in secondary forest. Plant species in each plot were inventoried and identified. The Shannon diversity index (H'), Pielou’s evenness, and Sørensen similarity index were used to assess species richness, evenness, and floristic composition. Results: The individual density was higher in the primary forest (588 ind/ha) than in the secondary forest (294 ind/ha), with a statistically significant difference (χ² = 26.322; p = 0.0018). The primary forest showed greater floristic richness than the secondary forest. Significant differences were observed in species number (t = -8.175; p = 0.0038) and genera (t = -5.435; p = 0.01223), but not in family-level diversity. Functionally, aboveground biomass was concentrated in medium to large diameter classes in the primary forest (up to 43.41 t/ha in the 60-70 cm class; CV = 17.48%), whereas in the secondary forest, biomass was dominated by smaller diameters (68.8 t/ha in the 10-20 cm class; CV = 97.15%), reflecting greater structural heterogeneity. Conclusion: The intensity of anthropogenic disturbances negatively affects species richness, floristic diversity, and functional forest structure