Assessing Short-Term Temporal Variability of CO2 Emission and Soil O2 Influx in Tropical Pastures and Regenerating Forests

Soil respiration, the exchange of gases between soil and the atmosphere (O2 consumption and CO2 production), plays a key role in ecosystem functioning and climate regulation. This study investigated the short-term temporal variability of soil CO2 emissions and O2 influx and their relationship with tropical climate conditions and soil attributes in the Cerrado region, Selvíria, MS, Brazil. Soil CO2 emissions were measured using the LI-8100 portable system, while soil O2 influx was estimated by linear interpolation of O2 variation inside the chamber using a UV Flux 25% (ultraviolet light) sensor. Soil temperature and moisture were measured simultaneously in three land use types: pasture (~11 years) and reforested areas with native species and eucalyptus (~35 years). Soils were classified as Oxisoils according to Soil Taxonomy. Significant short-term temporal variability was observed in CO2 emissions (mean 3.2 ± 0.5 µmol m−2 s−1), O2 influx (mean 1.8 ± 0.3 mg O2 m−2 s−1), soil temperature and moisture across the land use types. Pasture areas exhibited the lowest CO2 emission rates, associated with improved soil attributes (soil organic matter, sum of bases and pH) due to management practices, while reforested areas showed overlapping soil respiration patterns and higher temporal variability. Principal component analysis revealed strong coupling between O2 influx and CO2 emission in reforested soils. These findings highlight the influence of land use on short-term soil respiration dynamics and underscore the importance of sustainable pasture management and reforestation in the Brazilian Cerrado. The results also support public policies aimed at restoring degraded pastures, reducing deforestation and burning, and enhancing soil carbon sequestration to mitigate climate change.