Impacts of fire suppression on above-ground carbon stock and soil properties in Borana rangelands, southern Ethiopia

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.