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Background: Fire is a natural disturbance that releases carbon back into the atmosphere. Pastoralists have used fire for many thousands of years for rangeland management. The use of fire in the Borana rangelands of southern Ethiopia was a common practice to improve the productivity of the rangelands. However, the use of fire as a tool to manage rangeland was prohibited by government policy in the early 1970s. Methods: In this study, we assessed the long-term impacts of fire suppression on aboveground carbon stocks of woody and herbaceous biomass, soil organic carbon stocks, and total nitrogen stocks at burned versus adjacent unburned areas in the Borana rangelands of southern Ethiopia. The investigation was conducted in two locations: Dikale and Sanke. The upland location was represented by Dikale, while the bottomland location was represented by Sanke. Each study site was replicated three times, with burned versus adjacent unburned areas representing each replicate. Soil samples were collected in three soil depths (0-5, 5-15, and 15-30 cm), while vegetation attributes were collected from 60 plots within three burned and three adjacent unburned sites in each landscape. Results: The soil organic carbon stock and pooled carbon stock between burned and unburned sites across the two landscapes showed minimal variation. The above-ground carbon biomass accumulation for woody and herbaceous plants did not show any significant difference between burned and unburned sites both at the bottomland and upland areas. The total nitrogen contents recorded at uplands in burned sites were significantly (p < 0.05) higher than the total nitrogen stocks for the unburned adjacent sites. Conclusions: Burned areas accumulated relatively more carbon stocks in terms of herbaceous biomass (3.27 ± 0.43 Mg ha −1 ) than the adjacent unburned areas (0.98 ± 0.43 Mg ha −1 ). The results of the current study suggest that burning improved the carbon sequestration potential of herbaceous plants in arid savanna ecosystems.

This study was conducted in Adami-Tullu Jido-Kombolcha and Arsi Negelle districts, south central Ethiopia. The objectives of the study were to evaluate the interactive effects of grazing management systems and rangeland sites on dry-matter production and chemical composition of herbaceous plants in south central Ethiopia. Data were analyzed using GLM procedure in SPSS 16.0 version, which was used for mean comparisons using post-hoc t-test that can be employed to compare mean differences for enclosure and open-grazed areas. To test the effects of management systems and altitudinal variation on dry-matter production and chemical composition of herbaceous species, mixed model analysis was employed using sample site as a random variable while grazing management systems and altitude were fixed variables. A total of 28 herbaceous species were identified. Of the identified herbaceous species, 20 species were grasses, 2 species were legumes while 6 species were forbs. Among the recorded grass species, some were highly desirable, while others were in the categories of intermediate in terms of desirability and less desirable. We identified the dominant and common grass species that included: Arstida adscensionis, Cenchrus ciliarus, Chloris gayana, Chloris roxburghiana, Bothriochloa insculpta, Eragrostis papposa, Heteropogon contorus, Panicum maximum, Indigofer spinosa, Tephrosia pumila, Sporobolus pyrmidalis, Themeda triandra, B. nigropedata, Ocimum basilicum, Amaranthus dubis, Tribulos terrestris and Achyrantes aspera. The chemical composition of herbaceous plants were analyzed for DM, CP, NDF, ADF, ADL and Ash comparing two grazing management systems and three rangeland sites as patch mosaic units. The results of the present analysis showed that the average CP content in the open-grazed areas was significantly (P<0.05) higher than that of the enclosed areas. The upper and middle rangeland sites displayed significantly (P<0.05) higher CP content for the open-grazed areas than the enclosure management across the study areas. The present findings suggest that the DM, NDF, ADF, ADL and Ash contents of herbaceous species was significantly (P<0.05) lower in the open-grazed areas than in the enclosure management.