Impacts of prescribed burning on soil greenhouse gas fluxes in a suburban native forest of south-eastern Queensland, Australia

[摘要] Prescribed burning is a forestmanagement practice that is widely used in Australia to reduce the risk ofdamaging wildfires. Prescribed burning can affect both carbon (C) andnitrogen (N) cycling in the forest and thereby influence the soil-atmosphereexchange of major greenhouse gases, i.e. carbon dioxide (CO₂), methane(CH₄) and nitrous oxide (N₂O). To quantify the impact of aprescribed burning (conducted on 27 May 2014) on greenhouse gas exchange andthe potential controlling mechanisms, we carried out a series of fieldmeasurements before (August 2013) and after (August 2014 and November 2014)the fire. Gas exchange rates were determined in four replicate plots which wereburned during the combustion and in another four adjacent unburned plots locatedin green islands, using a set of static chambers. Surface soil propertiesincluding temperature, pH, moisture, soil C and N pools were also determinedeither by in situ measurement or by analysing surface 10 cm soil samples.All of the chamber measurements indicated a net sink of atmospheric CH₄,with mean CH₄ uptake ranging from 1.15 to 1.99 mg m⁻² d⁻¹.Prescribed burning significantly enhanced CH₄ uptake as indicated by thesignificant higher CH₄ uptake rates in the burned plots measured inAugust 2014. In the following 3 months, the CH₄ uptake rate wasrecovered to the pre-burning level. Mean CO₂ emission from the forestsoils ranged from 2721.76 to 7113.49 mg m⁻² d⁻¹. The effect ofprescribed burning on CO₂ emission was limited within the first 3 months, as no significant difference was observed between the burned and theadjacent unburned plots in both August and November 2014. The CO₂emissions showed more seasonal variations, rather than the effects ofprescribed burning. The N₂O emission in the plots was quite low, and nosignificant impact of prescribed burning was observed. The changes inunderstory plants and litter layers, surface soil temperature, C and Nsubstrate availability and microbial activities, following the prescribedburning, were the factors that controlled the greenhouse gas exchanges. Ourresults suggested that the low-intensity prescribed burning would decreasesoil CO₂ emission and increase CH₄ uptake, but this effect would bepresent within a relatively short period. Only slight changes in the surfacesoil properties during the combustion and very limited impacts of prescribedburning on the mineral soils supported the rapid recovery of the greenhousegas exchange rates.

[学科分类] 地球化学与岩石