IMPACT OF PETROLEUM CONTAMINATION ON SOIL AND PASTORAL VEGETATION IN SOUTH SUDAN RANGE-LANDS: A CASE STUDY OF PALOUGE OIL FIELD AS A STEP TOWARD NATURAL REHABITALIZATION

: Petroleum contamination in oil-producing regions of South Sudan, especially inside and surrounding Palouge oil field, has resulted in severe degradation of natural range lands represented by soil and vegetation. This study traces the magnitude of degradation in soil physical and chemical properties, beside, identifying native range species and their resilience to petroleum contamination. Commonly, petroleum contamination has been shown to significantly alter soil chemical and physical properties in oil-producing regions of South Sudan. These alterations are represented by a decrease in pH value, reflecting an oxidation to hydrocarbon, an elevation in electrical conductivity, indicating an increased salinity, an increase in total carbon (%) coupled with a decrease in total nitrogen (%), which results in an increase in C: N ratio. Also, bulk density was increased because of compaction and loss of porosity. These alterations resulted in a significant reduction of soil water-holding capacity. The overall result of pH value decline and the increase in salinity and bulk density is inappropriate conditions for native and /or cultivated plant species. At the Palouge site, Sorghum bicolor and Sorghum vulgare showed the highest percentage cover in uncontaminated and contaminated plots (21.2 and 20.6% vs. 17.3 and 17.6% for the first and the second species in uncontaminated and contaminated plots, respectively). Also, the only graminous species that showed significant reduction in percentage cover with contamination were Hyparrhenia rufa, Zea mays, and Festuca rubra. Frequency (%) of graminous species was generally significantly reduced in contaminated plots, except for Oryza longistaminate and Sorghum vulgare. The forbs species’ percentage cover was significantly favored with contamination for Gossypium barbadense and Medicago sativa (6.1 and 15.2% under contamination vs. 2.9 and 6.9% under uncontaminated conditions for the first and the second species, respectively). Plant cover was dominated by graminous species (90.2 vs. 73.9 for uncontaminated and contaminated plots, respectively). Native pastoral species showed variable levels of resilience with elite species such as Tihonia diversifolia, Sorghum sp < /em>, Medicago sativa, and Gossypium barbadense, proposing well qualifications as well-qualified phytoremediators. Proposed plans for soil restoration, environmental monitoring, and phytoremediation in oil-contaminated ranges of South Sudan are essential for long-term pasture rehabilitation.