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 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.

This study aimed to evaluate the role of trees outside forests on agricultural land (TOF-AL) in preserving the initial aboveground biomass (AGB) of forests within the agricultural landscape of Mongala province in the Democratic Republic of Congo. In 2024, tree inventories were conducted over four months in the forests and agricultural lands of Mongala province to estimate above-ground biomass (AGB). The effects of artisanal logging and charcoal production activities on the AGB conservation rate were considered. The study indicates that 78.3% of trees encountered in the agricultural lands were large-diameter trees (DBH ≥ 10 cm). In forest areas, large-diameter trees account for 55.9% of tree density. The average AGB are 66.8 Mg ha^-1 for TOF-AL and 373.5 Mg ha^-1 for forest trees. The AGB of TOF-AL accounts for 17.9% of the total forest trees AGB. The AGB conservation rates vary by region, with Lisala having the highest at 22.1%, Bumba the lowest at 11.2%, and Bongandanga at 20.5%. Artisanal logging and charcoal production reduce the AGB conservation rate by TOF-AL. The AGB conservation rate is positively correlated with the distances to the major cities. These results prove that conserving trees in agricultural landscapes can reduce AGB losses associated with slash-and-burn agriculture and contribute to mitigating climate change effects.

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.

This study investigated the diversity and ethnobotanical use values of trees outside forests on agricultural lands (TOF-AL) in the Mongala province, Democratic Republic of Congo. To achieve this, inventories of TOF-AL, linked to surveys on ethnobotanical use values, were conducted in 45 villages across the three territories of this province (Bongandanga, Bumba and Lisala). The results identified 136 TOF-AL species, revealing significant species richness and diversity variations across three territories. Bongandanga and Lisala exhibited higher species diversity compared to Bumba. Five dominant species (Petersianthus macrocarpus (P.Beauv.) Liben., Pycnanthus angolensis (Welw.) Warb., Ricinodendron heudelotii (Baill.) Pierre ex Heckel., Erythrophleum suaveolens (Guill. & Perr.) Brenan., and Piptadeniastrum africanum (Hook.f.) Brenan.) accounted for over 50% of the total tree abundance and were widely cited for their ethnobotanical significance. P. macrocarpus, E. suaveolens, and R. heudelotii were universally recognised by local populations for their diverse uses, including medicine, food, and trade. Hierarchical clustering analysis revealed three distinct groups of preferred species based on their primary use values: (1) species valued for energy and construction, (2) species valued for crafts and trade, and (3) species valued for medicine, food, and trade. These results highlight the critical role of TOF-AL in supporting local livelihoods and underscores the importance of conserving these resources for sustainable agricultural landscapes.

This study aimed to evaluate the role of trees outside forests on agricultural land (TOF-AL) in preserving the initial aboveground biomass (AGB) of forests within the agricultural landscape of Mongala province in the Democratic Republic of Congo. In 2024, tree inventories were conducted over four months in the forests and agricultural lands of Mongala province to analyse AGB. The effects of artisanal logging and charcoal production activities on the AGB conservation rate were considered. This study indicates that 78.3% of the trees encountered in agricultural lands were large-diameter trees (diameter at breast height (DBH) ≥ 60 cm). In forest areas, large-diameter trees accounted for 55.9% of tree density. The average AGBs are 66.8 Mg ha⁻¹ for TOF-AL and 373.5 Mg ha⁻¹ for forest trees. The AGB of TOF-AL accounts for 17.9% of the AGB of the total forest trees. The AGB conservation rates vary by region, with Lisala having the highest at 22.1%, Bumba the lowest at 11.2%, and Bongandanga at 20.5%. Artisanal logging and charcoal production reduce the AGB conservation rate of TOF-AL. The AGB conservation rate is positively correlated with the distances to major cities. These results prove that conserving trees in agricultural landscapes can reduce the AGB losses associated with slash-and-burn agriculture and contribute to mitigating climate change effects.