Land use and cover changes lead to loss of vegetation cover and subsequent change in soil organic carbon (SOC) and soil quality. This study was carried out in a lake retreat area in the Main Ethiopian Rift Valley, to investigate SOC stock build-up in function of duration of land emergence and SOC dynamics in function of land use and cover changes. Based on an analysis of Landsat imagery (1973, 1986 and 2000), coupled with soil and land use studies, determinants for SOC stock were found. Firstly, SOC stock significantly differed between cultivated land and grazing land (3301 and 2626 g m
− 2) on the one hand, and woodland (4594 g m
− 2) on the other. Further, only weak relations were found between SOC stock and vegetation index or IR and green band reflectances, which is related to low canopy density (even in woodland) and low leaf density of Acacia during the dry season.
The strongest explanation of SOC stock is related to the duration of emergence and hence of pedogenesis. Its proxy, elevation, explains much of the variability of SOC (R2 = 0.48). There is a non-negligible long-term trend of SOC build-up from < 2000 g m− 2 (inherited C-rich limnic sediments) to > 4500 g m- 2 under the climax Acacia–Balanites woodland (on land that emerged approximately 4233–4540 BP). Using a multiple regression model involving elevation and presence of forest or woodland, the SOC stock in the study area could be assessed at 3966 (± 1799) g m− 2 SOC in 2000, against 4319 (± 1835) g m− 2 in 1986 and 4199 (± 1866) g m− 2 in 1973, thereby confirming the rapid SOC depletion after removal of vegetation.
