Impactos das mudanças de uso da terra e manejo nos estoques de carbono do solo em diferentes biomas brasileiros.

Abstract

The balance between C input and output in the soil has strong influence on atmospheric CO2 concentrations and the land-use change can affect this natural cycle by altering the CO2 fluxes from soil to atmosphere (emission) or from atmosphere to soil (sequestration). Thus, there is a strong interest to promote the C sequestration in agricultural soils as a strategy to mitigate the current CO2 levels in the atmosphere. In this context, the goals of this work were to evaluate the impacts of main land-uses and agricultural management systems on soil organic carbon stocks over time and in different soil layers in the Brazilian biomes. A database with 246 pairs of observations was use to derive, through a linear mixed model, 74 factors for different soil layers (0-30, 0-50, and 0-100 cm) and time spans (5, 10, 15, 20, 30 and 40 years). Those factors were distribute in four types of conversion: native vegetation to full-tillage (NV-FT), native vegetation to no-tillage (NV-NT), full-tillage to no-tillage (FT-NT) and pasture to no-tillage (PA-NT). The removal of NV to introduce FT systems, reduced carbon stocks by 10% for the depth of 30 cm in the Cerrado biome; 17, 13 and 4% for the depth of 30, 50 and 100 cm, respectively, in the Caatinga biome; 14 and 9% for the depth of 30 and 50 cm, respectively, in the all Brazilian biomes, after 20 years of land-use in relation to NV. The conversion of NV to NT also promoted SOC losses, with reductions ranging between 2 and 8% in the Cerrado biome, depending on the soil depth and the evaluated period. The estimates made for Brazil the losses were 4% for the depth of 30 cm, after 20 years of land-use in comparison to NV. The change of management from FT to NT increased SOC stocks by 22% in the Cerrado, 13% in the Atlantic Forest and 9% in Brazil, considering the depth of 30 cm after the 20 years of land-use. While the replacement of pasture by NT increased the SOC content by 16% for the depth of 30 cm after 20 years of its implantation.