Physicochemical properties of soils drive floristic richness of pastures in eastern Democratic Republic of Congo

Abstract Background The eastern Democratic Republic of the Congo (DRC) presents unique environmental conditions that shape pasture composition and productivity. However, overgrazing, deforestation, and recurrent bushfires have degraded the grasslands, threatening livestock productivity and biodiversity. Despite these challenges, little is documented on the dominant plant species and their ecological adaptations. By analysing the floristic diversity and soil properties across these regions, this study seeks to identify key constraints and opportunities for optimizing pasture management. Results The findings revealed 209 plant species belonging to 49 botanic families where Poaceae, Fabaceae and Asteraceae were dominant. Annual grasses (40.7%) were dominant type over perennial grasses (29.3%) and shrubs (23.6%). The soils in the Ruzizi plain are mainly sandy and medium in nitrogen and very low in phosphorus, and are clayey and slightly acidic. The regions of Kabare and Kalehe have low phosphorus content and medium nitrogen content while those in Kalemie are mainly loamy besides being rich in silt and with relatively favorable pH for plant growth (5.5–6.5). The fidelity index (FI) of plant species revealed that the grazing lands in the Hinterland of Bukavu were characterized by 4 plant species including Centella asiatica , Digitaria vestida , Sporobolus pyramidalis and Pennisetum clandestinum , while the Ruzizi plain was characterized by 40 species with Brachiaria ruziziensis , Sporobolus sp., Acacia spinoza and Stylosanthes scabra being dominant; and Kalemie had 21 characteristic species among which Hypparhenia sp., Parinaria sp., Costus sp. and Guizotia scabra presented a FI > 0.65. Conclusions These findings demonstrate that the floristic composition of grazing lands in eastern DRC is richly diverse and is mainly influenced by soil properties and agroecological conditions. Despite the high floristic richness observed in the study area, most of the plant species are increasers that have survived under disturbance conditions such as overgrazing and repeated bushfires, and therefore are not suitable for guaranteeing the optimum productivity of grazing animals. In the communal grazing system, common approaches are suggested for joint interventions between pasture users and relevant government departments. In the private grazing system, removal of increasers and introduction of improved grasses such as improved Brachiaria cultivars are suggested to achieve a balance among species diversity protection, cattle production, and soil quality management.