Organic matter stabilization mechanisms in tropical soils with carbon sequestration areas: evaluation by physicochemical methods and carbon modeling

Abstract

Since the industrial revolution, the exponential population growth has generated the need to increase the food production. Expansion of territories for agriculture has caused the replacement of natural ecosystems, changing the carbon flows to the atmosphere. Agriculture accounting for 30% of Greenhouse Gas (GHG) emissions, land use change (especially deforestation) accounting for 18% and fossil fuel emissions and industrial activities accounting for the other 52%. The high presence of GHG in the atmosphere has been increasing the planet's temperature, which has caused alarming consequences such as melting glaciers and rising sea levels. New technologies are necessary to mitigate GHG emissions and to reduce the temperature. The implementation of agriculture sustainable systems are desirable to achieve the agriculture decarbonisation. Integrated Systems (IS), such as crop-livestock-forest has demonstrated the ability to sequester carbon, by capturing gases in biomass growth (especially in trees) and by increasing soil carbon content, contributing to GHG mitigation. Studies to evaluate the mechanisms of carbon storage in tropical soils are essential to understand the IS contribution to carbon sequestration. Thus, the carbon accumulated mechanisms in the crop-livestock-forest IS in tropical soils will be evaluated, as well its quality. The main carbon source in soils is organic matter which can be stabilized by three mechanisms: organo-mineral interactions, stabilization through of humification process and physical protection by the aggregates. Soil carbon accumulation will be evaluated through physical and chemical soil fractionation methods and compared to reference areas (a native forest and a degraded pasture areas). Both intact soils and organic matter extracted will be quantified by traditional methods and also with new tools such as LIBS. It will be characterized by spectroscopic techniques such as nuclear magnetic resonance, electronic paramagnetic resonance, laser-induced fluorescence and imaging techniques (atomic force microscopy) to evaluate structural aspects in soils and their fractions. The data generated from the accumulation of organic matter in the IS will enable the modeling with CQESTR software and to project it in long-term. Therefore, through the results it will be possible to understand the carbon accumulation processes in tropical soils, which will be reference data for government organizations to adopt policies to implement IS. Also, it will allow advances in current understanding on the organic matter accumulation in soils, a topic of extreme relevance and current discussion. (AU)