In the Cuitzeo Basin (Michoacán, Mexico), land degradation has reduced soil fertility and productivity. The necessity of rural communities of searching resources for improving the local economy has lead to an increase in timber extraction activities during the last years. This practice has been associated to a decrease in the vegetation cover and an increase in the soil surfaces affected by degradation processes. As a consequence, the SOM stored in the soils of this area is in high risk of being lost, especially in the upper soil horizons. Thermal stability of soil organic matter (SOM) refers to its resistance to thermal oxidation during heating treatments and relationships between thermal properties and biological stability have been found (1). Thus, thermal techniques allowing to detect gross changes in SOM as a consequence of land-use changes has also been referred. The objective of this work was to determine how land use and forest degradation affected the SOM of volcanic soils located at the Mexican Volcanic Belt, using as a tool the thermal responses of the C associated to the silt- and clay- sized fractions.