The aim of our research was to investigate the concentration and stock of organic carbon (SOC) in soils of Golija Mountain, Serbia, under different land uses (grassland, forest, and arable land) at different altitudes (1,500 m, 1,000 m, and 500 m) and at two soil depths (0-10 cm and 10-20 cm), and to assess resilience of soil organic matter to decomposition under each of the ecosystems by measuring the amount of SOC and soil respiration rate. The results show the highest SOC stock under forest and lowest under grass, a decreasing trend in SOC from higher to lower altitudes, the lowest cumulative soil respiration under forest and the highest under grass. This study demonstrates that the land use system and altitude are important factors affecting SOC.