Resumo. The adoption of management practices that ensure the stability of soil organic matter also maintain the stability or quantitative increase of carbon (C) in the lithosphere, reducing the amount of CO 2 in the atmosphere. You can also minimize the losses of C to the atmosphere by using conservation practices, or using cover crops to keep the soil C stocks, and the forest cover are considered great abduction and forest systems considered large reservoirs of C. This work was performed on a property located in Chapecó, Santa Catarina state, where soils were sampled from different forest formations distributed in a homogeneous soil range. The local climate is mesothermal, rainy, and the soil was characterized as an association Cambissolo Háplico/Neossolo Litólico. The objectives were to estimate the C stocks in soils and estimate the C losses occurred due to the change of soil cover. It was evaluated soils under natural forest (FN), of secondary stage, with a high degree of preservation; planted forest of eucalyptus ( Eucalyptus saligna ) (PE), with eight years of cultivation, preceded by 17 years under crop conventional tillage; and a planted forest of herb mate ( Ilex paraguariensis ) (EM), with 25 years of cultivation under conventional system (cutting interval of 18 months, with removal of all waste produced and maintenance of the ground without cover, with periodic use of herbicide - glyphosate). In each area were opened four trenches with 50 cm deep, where soil samples were collected in depths of: 0-5 cm, 5-10 cm, 10-20 cm, 20-30 cm, 30-40 cm, and 40-50 cm, with kopeck rings. It was possible to determine the bulk density (Mg m -3 ), the soil volume per layer (depth) and per hectare, and the concentration of soil C in the different studied areas. To quantify the C stocks equal amounts of soil were used for each depth evaluated. It was observed higher densities of soils and under PE and EM, to FN the lowest density are explained by the large amount of organic material and the absence of anthropogenic effects. In FN, despite the lower bulk density, there was a greater soil content C, with 107.67 Mg C ha -1 . On the soil under PE, with stock 79.58 Mg C ha -1 , depending on previous use (17 years under crop conventional tillage), it is assumed that part of C has been recovered. Under EM, with stock of 47.29 Mg C ha -1 , C losses were evident, with about 221 Mg CO 2 ha -1 emitted from the soil. It was evident that the change in forest cover and management procedures can lead to large losses of C stored. Thus, the soil under forest, or the soil-plant a forest canopy, considered a major reservoir of C, can become a major source of C to the atmosphere, contributing to increased the greenhouse effect.