SOIL ORGANIC CARBON DYNAMICS AFTER DEFORESTATION IN BRAZIL

Soil organic carbon (SOC) plays a key role in ecosystem functioning and climate regulation, particularly under deforestation and land use change. This study assessed the spatio-temporal dynamics of SOC stocks (0–20 cm) in Brazilian lands converted from native vegetation to anthropic use between 1990 and 2023, relating SOC variations to land use and land cover (LULC) trajectories across biomes. The analysis was based on a national SOC stock map (0–20 cm) with moderate predictive performance in the external test set (R² = 0.30; RMSE = 21.26 Mg ha⁻¹), generated using a soil-informed multitemporal Random Forest model, integrating static terrain and mineralogical covariates with dynamic remote sensing variables. The analysis focused on the dominant deforestation pathway associated with agricultural expansion, which consistently corresponded to the conversion of native vegetation to pasture. Results indicate that this dominant transition led to an overall SOC stock reduction of 4.4% in the Amazon, Atlantic Forest, and Pantanal biomes over the study period. Approximately 13.8% of the deforested areas occur on clayey soils, a factor that may influence the magnitude and persistence of carbon losses due to mineral-associated organic matter stabilization processes. In contrast, SOC stocks remained relatively stable in the Pampa biome and increased in the Cerrado and Caatinga. Those gains can be mainly attributed to the replacement of degraded lands with conservation-oriented management systems, such as no-tillage, and public policies. Overall, SOC stock dynamics were strongly governed by LULC trajectories, with important implications for carbon balance and environmental sustainability.