Climate Change Mitigation: Understanding the Distribution, Stock, and Dynamics of Soil Organic Carbon in the Ethiopian Highlands

Abstract

Soil, as a pool of carbon, has a high potential role to help adapt and mitigate climate change because soil organic carbon (SOC) responds most to land management. The understanding of SOC nature contributes to climate mitigation and adaptation strategy development. This study provides a review on SOC and examine SOC distribution, stock, and dynamics in the Ethiopian Highlands under three land use types (LUTs) as cropland use (CLU), forestland use (FLU), and grassland use (GLU) at three sites (Gununo, Anjeni, and Maybar). In 2010, 239 soil samples were taken from 64 profiles representing 0–10, 10–30, 30–50, and 50–100 cm layers. The soil data from the 1980s was used to study SOC dynamics. The Wakley and Black method was used to determine SOC. Findings showed that SOC stock varies from 0.6 to 186 t/ha with 46 t/ha median value under the observed LUTs. The median SOC stocks (t/ha) were 38, 48, and 51 for CLU, FLU, and GLU, respectively. Statistical test results were significant across categories of LUTs (p < 0.02, α = 0.05). Deeper soil profiles (30–100 cm) accounts for 61% SOC stock. Carbon stratification ratio (CSR) was highest at Maybar (among sites), in GLU (among LUTs), and at 10–30 cm sub-layer (among profile layers). CSR temporal comparison of the 1980s and 2010 value of SOC (g/Kg) among ten profiles showed 20% sequestration. An average SOC sequestration rate was 1.6 (g/kg/25 years), while depletion rate ranged from −0.1 to −1.3 (g/kg/20 years). The study recommends SOC monitoring every 5–10 years.