Soil greenhouse gas emissions under different land uses in the Eastern Amazon

Resumo

Land-use changes significantly affect soil greenhouse gas (GHG) emissions by altering the biogeochemical cycles of carbon and nitrogen in tropical ecosystems. This study aimed to evaluate CO₂, CH4, and N₂O emissions from soils under different land uses in the Eastern Amazon (forest, agriculture, intensive pasture, and nominal pasture) through a laboratory incubation experiment using static chambers. The experiment followed a completely randomized design with four treatments and five replicates. Gas fluxes and production were quantified using gas chromatography. The results indicated that the nominal pasture showed the highest cumulative CO₂ emissions (246.0 ng CO₂ g^-1 dry soil), while the intensive pastures registered the highest cumulative N₂O emissions (64.3 ng N₂O g^-1 dry soil). In contrast, the lowest fluxes were observed in forest soils (64.2 ng CO2 g^-1 and 26.8 ng N2O g^-1 dry soil). Regarding CH4, all systems acted as sinks, with the highest oxidation rates observed in intensive pasture (–199.7 ng CH4 g^-1 dry soil) and nominal pasture soils (–249.3 ng CH4 g^-1 dry soil), while forest soils showed lower efficiency in removing this gas (–49.0 ng CH4 g^-1 dry soil). It is concluded that land use significantly influences soil GHG emissions in the Eastern Amazon. Nominal pasture increases CO₂ emissions, whereas intensive pasture enhances N₂O emissions. Soil physical and hydrological properties directly affect CH4 oxidation. The adoption of sustainable management practices, such as optimized fertilization and proper control of soil compaction, may help mitigate GHG emissions and promote the balance of carbon and nitrogen cycles in Amazonian soils.