CO2, CH4 and N2O fluxes from soil of a burned grassland in Central Africa

[摘要] The impact of fire on soil fluxes of CO₂, CH₄ and N₂O wasinvestigated in a tropical grassland in Congo Brazzaville during two fieldcampaigns in 2007–2008. The first campaign was conducted in the middle ofthe dry season and the second at the end of the growing season, respectivelyone and eight months after burning. Gas fluxes and several soil parameterswere measured in each campaign from burned plots and from a close-by controlarea preserved from fire. Rain events were simulated at each campaign toevaluate the magnitude and duration of the generated gas flux pulses. Inlaboratory experiments, soil samples from field plots were analysed formicrobial biomass, net N mineralization, net nitrification, N₂O, NO andCO₂ emissions under different water and temperature soil regimes. Onemonth after burning, field CO₂ emissions were significantly lower inburned plots than in the control plots, the average daily CH₄ fluxshifted from net emission in the unburned area to net consumption in burnedplots, no significant effect of fire was observed on soil N₂O fluxes.Eight months after burning, the average daily fluxes of CO₂, CH₄and N₂O measured in control and burned plots were not significantlydifferent. In laboratory, N₂O fluxes from soil of burned plots weresignificantly higher than fluxes from soil of unburned plots only above70% of maximum soil water holding capacity; this was never attained inthe field even after rain simulation. Higher NO emissions were measured inthe lab in soil from burned plots at both 10% and 50% of maximum soilwater holding capacity. Increasing the incubation temperature from 25 °C to 37 °C negatively affected microbial growth, mineralization andnitrification activities but enhanced N₂O and CO₂ production.Results indicate that fire did not increase post-burning soil GHG emissionsin this tropical grasslands characterized by acidic, well drained andnutrient-poor soil.

[学科分类] 地球化学与岩石