Advances in quantifying soil organic carbon under different land uses in Ethiopia: a review and synthesis

Abstract

Background: In the face of climate change and global warming, scientists globally are striving for effective techniques on how best to sequester carbon in order to reduce global warming and achieve environmental sustainability. This paper reviews the available literature on the influence of various land use changes on gains and/ or losses of soil carbon (C) stocks in Ethiopia. Results: Our review indicated that 33.3% of the studies reported soil organic carbon (SOC) concentration, 13.9% reported only SOC stock while 52.8% reported both SOC concentration and stock. Studies focusing on 0-30 cm only were 44%, other studies extending up to 40 to 100 cm were 50%, and studies extending to more than 100 cm accounted for 2.8% while studies without any depth specification accounted for 2.8%. Irrespective of soil type, C stocks in the top soil (0-30 cm) were found to be higher than at subsoil depths. Even though there is significant improvement in C sequestration in exclosures and community forests, the level of C sequestered is still below that of church forests. Conclusion: Conversion of native forest to other land uses resulted in a significant decrease in the SOC stocks across Ethiopia. Absence of long-term field trials and non-existence of SOC database are among the major drawbacks of SOC studies in Ethiopia identified in this review. With better management practices, it is possible to restore depleted C concentrations and stocks even in degraded lands and to conserve C in more pristine lands across the rugged landscapes of Ethiopia.

Micronutrient Content, Soil Carbon and Nitrogen Stocks in Forested and Deforested Sites

“…Many leguminous tree species contribute to higher soil organic carbon and nitrogen stocks. These results corroborate the findings by Okolo et al (2019), who showed higher soil carbon in forests than in deforested lands. Furthermore, the low carbon stocks in the deforested sites may be due to leaching and surface erosion losses.…”

“…This research is in line with Tashi (2017), who found that the wood roots buried in the soil after deforestation decay steadily and continue to improve the organic matter content of the soil. Also, Okolo et al (2019) projected the organic carbon and nitrogen stocks in the forested and deforested sites in the range between 230 Mg ha -1 and 65 Mg ha -1 , respectively.…”

Integrated Modeling of Land Degradation Dynamics and Insights on the Possible Future Management Alternatives in the Gidabo River Basin, Ethiopian Rift Valley

“…This could be attributed to the significant conversion of forestlands (-1.16%, -4.23%), grasslands (−1.31%, −3.26%) and shrublands (−2.41%, −3.59%) to other land uses, mainly croplands (Table S3) and extractive nature of the farming practice. In line with this, Negasa et al [72] and Okolo et al [73] indicated that conversion of native forest to other land uses and the intensification of agricultural activities resulted in a significant decrease in the SOC stocks across Ethiopia.…”

Soil organic carbon, total nitrogen stocks and CO2 emissions in top- and subsoils with contrasting management regimes in semi-arid environments

“…Low BD in natural (forests) and semi-natural (exclosures) ecosystems, could be attributed to constant input of high soil organic residues on the upper layer of the soil [83][84][85][86] . The contribution of tree roots to the subsoil organic matter (OM) accumulation, including root litter decomposition leads to the decrease in BD in forests [87][88][89] .…”