DYNAMICS OF LABILE SOIL CARBON UNDER DIFFERENT LAND USES IN THE DOCE RIVER BASIN

Labile carbon (labile C) is the fraction of soil organic matter that responds most rapidly to changes in management. Its quantification is, therefore, an essential tool for assessing the short-term impacts of land use changes on soil health. Thus, this study evaluated how different land use systems (natural succession - SN, eucalyptus cultivation - EU, and abandoned pasture - PA) and conversion times (9 and 22 years) influenced labile C contents. For this purpose, soil samples were collected at four depths (0.0-10 cm; 10-30 cm; 30-60 cm and 60-100 cm) in a Red-Yellow Latosol in the Doce River Basin (MG), following a systematic design in a 3×2×4 factorial scheme. The labile C contents were determined in the laboratory using the potassium permanganate oxidation method. The results showed that SN had the highest values (p < 0.1) of labile C. Although there was no difference in total content (0-100 cm) between the systems at 9 years, SN already stood out with the highest contents in the surface layer (0-10 cm) in this period, maintaining its superiority at 22 years, when it presented the highest values in the total profile (p < 0.1). Therefore, SN stands out as the most effective land use system for the accumulation of labile C, which indicates a rapid recovery of soil functional health, especially on its surface. It is evident that longer conversion periods (22 years) favor an increase in labile C contents, which are mainly concentrated in the surface layers, decreasing with depth.