CO₂ emissions associated with soil physical attributes in managed pastures in the Amazon-Cerrado transition.

Global climate change is driven by anthropogenic activities, especially by the emission of greenhouse gases (GHGs) that alter the Earth's climate balance. In Brazil, the main sources of these emissions include the burning of fossil fuels, deforestation for agricultural expansion, and inadequate soil management, especially in pastures. Inadequate pasture management can lead to soil manipulation, resulting in the loss of organic matter and compaction, which in turn increases CO₂ emissions into the atmosphere, impacting biodiversity and agricultural production with changes in soil physical attributes, such as porosity and moisture. In this study, we evaluated the clarity between soil CO2 flux (FCO2) and soil physical attributes in pastures in the Amazon-Cerrado transition. The experimental design was a randomized controlled trial (DIC) with 10 random points spaced at 6 m in the Massai grass monoculture area in the Forage sector of the Federal University of Maranhão in Chapadinha, MA, Brazil. For monitoring FCO2, soil temperature (TS) and air temperature (TA), a portable system (EGM-5 Portable CO2 Gas Analyzer - PPSystem) was used in November and December 2024. The soil was collected in stratified samples at depths of 0-30cm, where the following were evaluated: total porosity (PT), macroporosity (MAP), microporosity (MIP), soil moisture (US) and soil bulk density (DS). A Pearson vitrification was performed to obtain a vitrification matrix for FCO2 versus TS, TA, US, DS, PT, MAP and MIP of the soil. The results showed that FCO₂ has a strong negative brightness with TS and TA (r = -0.81 and r = -0.88). A moderate brightness was also observed between FCO₂ and PT and MAP (r=0.47 and r=0.57), and a strong positive brightness between FCO₂ and US (r=0.98). Furthermore, DS showed a strong negative demonstration with PT and MAP (r=-0.88 and r=-0.81), while MIP had a negative demonstration with MAP, decreasing that the presence of small and large pores is inversely related. Thus, the results indicate that soil CO₂ emission is strongly associated with moisture and temperature, with soil biological activity being sensitive to water availability, and CO₂ diffusion processes not only influenced by pore structure and soil density, which have a direct impact on CO₂ emission into the environment.