Soil CO2 CH4 and N2O fluxes from an afforested lowland raised peatbog in Scotland: implications for drainage and restoration

[摘要] The effect of tree (lodgepole pine) planting with and without intensivedrainage on soil greenhouse gas (GHG) fluxes was assessed after 45 yr ata raised peatbog in West Flanders Moss, central Scotland. Fluxes ofCO₂ CH₄ and N₂O from the soil were monitored over a 2-yrperiod every 2 to 4 weeks using the static opaque chamber method in arandomised experimental block trial with the following treatments: drainedand planted (DP), undrained and planted (uDP), undrained and unplanted(uDuP) and for reference also from an adjoining near-pristine areaof bog at East Flanders Moss (n-pris). There was a strong seasonal patternin both CO₂ and CH₄ effluxes which were significantly higher inlate spring and summer months because of warmer temperatures. Effluxes ofN₂O were low and no significant differences were observed between thetreatments. Annual CH₄ emissions increased with the proximity of thewater table to the soil surface across treatments in the order: DP < uDP < uDuP < n-pris with mean annual effluxes over the2-yr monitoring period of 0.15, 0.64, 7.70 and 22.63 g CH₄ m⁻² yr⁻¹, respectively. For CO₂, effluxes increased in the order uDP < DP< n-pris < uDuP, with mean annual effluxes of1.23, 1.66, 1.82 and 2.55 kg CO₂ m⁻² yr⁻¹, respectively.CO₂ effluxes dominated the total net GHG emission, calculated using theglobal warming potential (GWP) of the three GHGs for each treatment(76–98%), and only in the n-pris site was CH₄ a substantialcontribution (23%). Based on soil effluxes only, the near pristine(n-pris) peatbog had 43% higher total net GHG emission compared with theDP treatment because of high CH₄ effluxes and the DP treatment had33% higher total net emission compared with the uDP because drainageincreased CO₂ effluxes. Restoration is likely to increase CH₄emissions, but reduce CO₂ effluxes. Our study suggests that ifestimates of CO₂ uptake by vegetation from similar peatbog sites wereincluded, the total net GHG emission of restored peatbog would still behigher than that of the peatbog with trees.

[学科分类] 地球化学与岩石