Diurnal variations in greenhouse gas emissions from Acacia mangium plantation soil

Objective In order to study the diurnal variations in fluxes of greenhouse gases including CO₂, CH₄ and N₂O from Acacia mangium plantation soil, and determine the optimal observation time.

Method The emission fluxes of CO₂, CH₄ and N₂O from A. mangium plantation soil in southern China were continually observed using static-chamber and gas chromatograph.

Result The fluxes of CO₂, CH₄ and N₂O from A. mangium plantation soil had clear diurnal variations. The A. mangium plantation soil was a source of CO₂ and N₂O and a sink of CH₄. The daily fluxes of CO₂, N₂O and CH₄ ranged from 401.33 to 555.59 mg·m^-2·h^-1, 24.50 to 34.72 μg·m^-2·h^-1 and -10.96 to -41.88 μg·m^-2·h^-1 respectively. The fluxes of CO₂ or CH₄ from soil surface had highly significant (P < 0.01) or significant (P < 0.05) positive correlations with soil temperature at 5 cm depth, while CH₄ flux from soil surface was not significantly correlated with soil temperature.

Conclusion Based on the analysis of the correction coefficients of three greenhouse gases and manipulability of sampling, the optimal time for collection and observation of these three greenhouse gases from A. mangium plantation in southern China during rainy seasons is around 09:00.