AbstractThe carbon cycle includes important fluxes of methane (CH₄) and carbon dioxide (CO₂) between the ecosystem and the atmosphere. The fluxes may acquire either positive (release) or negative values (consumption). We calculated these fluxes based on short-campaign in situ chamber measurements from four ecosystems of South Vietnam: intact mountain rain forest, rice field, Melaleuca forest and mangroves (different sites with Avicennia or Rhizophora and a typhoon-disturbed gap). Soil measurements were supplemented by chamber measurements of gas fluxes from the tree stems. Measuring CH₄ and CO₂ together facilitates the assessment of the ratio between these two gases in connection with current conditions and specificity of individual ecosystems. The highest fluxes of CH₄ were recorded in the Melaleuca forest, being within the range from 356.7 to 784.2 mg CH₄–C m⁻² day⁻¹ accompanied by higher fluxes of CH₄ release from Melaleuca tree stems (8.0–262.1 mg CH₄–C m⁻² day⁻¹). Significant negative soil fluxes of CH₄ were recorded in the mountain rain forest, within the range from − 0.3 to − 0.8 mg CH₄–C m⁻² day⁻¹. Fluxes of CO₂ indicate prevailing aerobic activity in the soils of the ecosystems investigated. Quite a large variability of CO₂ fluxes was recorded in the soil of the Avicennia mangroves. The in situ measurements of different ecosystems are fundamental for follow-up measurements at different levels such as aerial and satellite gas fluxes observations.