Effects of land use change and agricultural management on soil carbon stocks in tropical pastures

In Brazil, land use changes, particularly in the Atlantic Forest biome, significantly impact soil carbon dynamics. Conservation practices, such as no-till farming and integrated systems, can mitigate GHG emissions by enhancing soil organic carbon (SOC) sequestration. This study aims to assess changes in SOCS resulting from three distinct LUC pathways: from natural vegetation (NV) to extensive pasture (EP); from EP to a crop-livestock-forest integration system (iCLF); and from extensive pasture to no-till soybean monoculture (NT). Areas with similar soil types (Oxisol) but different land uses were evaluated: NV, EP, iCLF, and NT. SOC stocks, C-accumulation rates, and isotopic composition (δ¹³C) were analyzed. The conversion of NV to EP increased carbon stocks in the 0–30 cm layer, with δ¹³C indicating pasture contribution. The transition from EP to iCLF further promote SOC accumulation across all depths, with δ¹³C suggesting contributions from both C₃ and C₄ plants. In contrast, converting EP to NT did not significantly affect SOC stocks. The annual SOC accumulation rates (0–100 cm) were 0.34, 5.38, and 2.35 Mg C ha⁻¹ year⁻¹ for NV to EP, EP to iCLF, and EP to NT, respectively. The corresponding SOC change factors were 1.24, 1.52, and 1.03. These findings highlight the potential of integrated systems to enhance soil carbon sequestration compared to conventional pasture and no-till practices.