Soil organic carbon stocks and properties are affected by plant cover types in an urban ecosystem in Colombia

Soil organic carbon (SOC) is the main element in soil organic matter (SOM) and its storage or release into the atmosphere is sensitive to changes in land use. This study evaluated SOC storage and SOM quality in the Metropolitan Regional Natural Park, Cerro El Volador, MedelIín-Colombia, in areas where plant cover was restored with plants from different functional groups consisting of secondary vegetation (SV), forest plantations of Eucalyptus globulus Labill. (EUC) and Pinus patula Schltdl. & Cham. (PIN), and pastures (PAS). Soil samples were taken at the O horizon and at two soil depths at the A horizon (0–10 and 10–20 cm). The quality of the SOM was evaluated through humification indices, spectrophotometric tests and carbon distribution in humic substances. The highest storage of SOC in the O horizon occurred in PIN, followed by EUC, SV and PAS. In descending order, the vegetation with the highest SOC values for the A horizon at both depths evaluated were EUC, PAS, PIN and SV. Humification indices showed that the SOM was mainly composed of fresh SOM with little humification. The humification process of SOM evolved towards humic acids of the P-group. These results show that the change of cover significantly affects the storage of SOC, the characteristics of SOM and the properties of the soil.