The rubber plantations in Sankuru province, located in the Democratic Republic of Congo (DRC), have historically been pivotal to the regional economy. However, the absence of suitable silvicultural practices has promoted self-regeneration, resulting in the proliferation of diverse species. This study aims to characterize species richness and plant structure of these plantations. To this end, 80 subplots measuring 0.25 hectares were meticulously established, with a proportionate division between state-owned and farmer plantations. The results obtained from this study indicate that these plantations are home to approximately 105 species, classified into 33 distinct botanical families, with dominant families such as Fabaceae, Meliaceae, Euphorbiaceae, Olacaceae, Clusiaceae, and Moraceae. Despite the similarity between the two types of plantations (Cs = 58%), significant disparities were observed in terms of individuals, 635 ± 84.06 and 828 ± 144.62 (p < 10⁻³); species, 41 ± 7.49 and 28 ± 4.59 (p < 10⁻³); families, 19 ± 3.06 and 16 ± 1.62 (p < 10⁻²); and basal area, 29.88 ± 5.8 and 41.37 ± 7.57 (p < 10⁻²) for state and peasant plantations, respectively. State plantations exhibited greater diversity (H′ = 1.87) and enhanced equity (J’ = 0.43) than peasant plantations. The diametric structure exhibited an inverted J-shaped distribution, indicating constant and regular regeneration of these plantations. The upper canopy dominates the vertical structure in both types of plantations, with a significantly higher proportion in peasant plantations (83.60%) than in state plantations (73.8%), ANOVA (F (2.24 = 21.78), df = 24; p = 4.03 × 10⁻⁶). The findings indicate that the sustainable management of these plantations could incorporate agroecological principles to promote the coexistence of rubber production and biodiversity conservation while contributing to the restoration of degraded ecosystems and the well-being of local communities.

The province of Sankuru, located in the Democratic Republic of Congo, is home to historic rubber tree plantations (Hevea brasiliensis) that play a significant role in carbon storage. However, despite their ecological and economic importance, little is known about the actual carbon sequestration potential of these abandoned or poorly managed plantations, and their contribution to climate change mitigation remains poorly quantified. This lack of empirical data limits the integration of such plantations into national and global carbon offset and conservation strategies. To address this gap, this study aims to assess the carbon sequestration potential of these plantations, while analyzing their ecological implications for the conservation and sustainable management of natural resources. This study therefore aims to (i) quantify the above-ground carbon stock of historic rubber plantations in Sankuru, (ii) develop a local allometric model adapted to Hevea brasiliensis to improve biomass and carbon estimation accuracy, (iii) assess the ecological and economic implications of carbon storage—including its monetary valuation—and (iv) provide recommendations for integrating rubber plantations into carbon offset and sustainable management frameworks. A floristic inventory was conducted in 80 plots of 0.25 ha across two plantation types, measuring trees with a diameter at breast height (DBH) ≥ 10 cm. A local allometric equation was developed from destructive sampling of 48 rubber trees across eight diameter classes. The quadratic model selected based on statistical performance (RMSE = 0.02; adjusted R² = 0.9971), accurately estimated above-ground biomass and carbon storage. Results revealed that smallholder plantations stored 139.08 tC/ha (USD 6,537/ha), while state plantations stored 180.61 tC/ha (USD 8,489/ha). These findings highlight the significant role of historic rubber plantations as secondary carbon sinks, with strong potential for inclusion in climate mitigation and payment for ecosystem services schemes. The study recommends integrating sustainable management and biodiversity conservation practices to enhance both ecological and economic benefits in the Sankuru region.

The rubber plantations in Sankuru province, located in the Democratic Republic of Congo (DRC), have historically been pivotal to the regional economy. However, the absence of suitable silvicultural practices has promoted self-regeneration, resulting in the proliferation of diverse species. This study aims to characterize species richness and plant structure of these plantations. To this end, 80 plots measuring 0.25 hectares were meticulously established, with a proportionate division between state-owned and farmer plantations. The results obtained from this study indicate that these plantations are home to approximately 105 species, classified into 33 distinct botanical families, with dominant families such as Fabaceae, Meliaceae, Euphorbiaceae, Olacaceae, Clusiaceae, and Moraceae. Despite the similarity between the two types of plantations (Cs = 58%), significant disparities were observed in terms of individuals: 635 ± 84.06 and 828 ± 144.62 (p < 10-3), and species: 41 ± 7.49 and 28 ± 4.59 (p < 10-3), and families: 19±3.06 and 16±1.62 (p < 10-2), and basal area: 29.88 ± 5.8 and 41.37 ± 7.57 (p <10-2) for state and peasant plantations, respectively. State plantations exhibited greater diversity (H'=1.87) and enhanced equity (J'=0.43) than peasant plantations. The diametric structure exhibited an inverted J-shaped distribution, indicating constant and regular regeneration of these plantations. The upper canopy dominates the vertical structure in both types of plantations, with a significantly higher proportion in peasant plantations (83.60%) than in state plantations (73.8%), ANOVA test (p = 4.03e-⁶) . The findings indicate that the sustainable management of these plantations could incorporate agroecological principles to promote the coexistence of rubber production and biodiversity conservation, while contributing to the restoration of degraded ecosystems and the well-being of local communities.

Agroforestry systems are recognized for their potential to enhance soils organic carbon (SOC) storage and to contribute to climate change mitigation, particularly in tropical regions subject to strong anthropogenic pressure. This study assesses the contribution of agroforestry systems to SOC storage through a comparative analysis between agroforestry systems (croplands with scattered multipurpose trees) and non-agroforestry systems (croplands without tree cover) in Kabare Territory, in eastern Democratic Republic of Congo, an area characterized by high population density and progressive degradation of agricultural soils. A comparative analysis was conducted using 10 plots (five agroforestry plots and five non-agroforestry plots). Soil samples were collected at three depths (0–10, 10–20, and 20–30 cm) to determine bulk density, pH, and soil organic carbon, and to estimate carbon stocks. The results show that bulk density increased with depth but remained significantly lower in agroforestry systems across all layers (p < 0.01), indicating improved soil structure. Soil carbon stocks were significantly higher under agroforestry systems, reaching approximately 35.4 ± 4.2 t C ha⁻¹ compared to 25.1 ± 3.8 t C ha⁻¹ in non-agroforestry systems at 0–10 cm, with similar trends at greater depths. A strong positive relationship was observed between SOC content and carbon stocks (R² > 0.90), while bulk density showed a negative relationship with carbon storage. Soil pH had no significant effect on carbon stocks. These findings demonstrate that agroforestry systems significantly enhance soil carbon storage and improve soil physical properties. In the context of the Congo Basin, agroforestry represents a viable strategy for soil restoration, sustainable agricultural intensification, and climate change mitigation.