Water-table changes and nutritional status affect trace gas emissions from laboratory columns of peatland soils

Peatlands potentially play a significant role in the global emission of three trace gases: carbon dioxide; methane; and nitrous oxide. We investigated the effect of a relatively small lowering of the water-table (10 cm) on the emission of these gases using repacked, root-free peat columns in the laboratory with peat from a nutrient-rich (eutrophic) site and a more nutrient-poor (mesotrophic) site, respectively. At a static high water-table (at the peat surface) high rates of anaerobic CO2 production were found, which were reflected in high (> 1.18) molar ratios of CO2 and CH4. A static water-table of IO cm below soil surface led to equal (eutrophic soil) or lower CO2 emission (mesotrophic soil) compared with the high static water-table. However, at a regularly changing water-table (between 0 and 10 cm below the peat surface), CO2 emission at a low water-table was 1.5 (mesotrophic soil) to 3 times (eutrophic soil) higher than at a high-water table. Maximum rates of CO2 emission from the eutrophic soil exceeded those from the mesotrophic soil, except at a static high water-table. Methane emission was about one order of magnitude lower at a low static water-table compared with the static high water-table. There was no clear effect of the nutritional status of the peat on maximum methane emission in the various water-table treatments. The nutritional status of the peat had a profound influence on the effect of water-table lowering on N2O emission: nitrous oxide emission from the eutrophic soil was strongly increased at a low water-table, whereas there was no detectable N2O emission from the mesotrophic soil. Despite a clear effect of the water-table treatments on both trace gas emissions and on redox potentials in the soil, no significant correlation between these variables was found in either soil type. (C) 1997 Elsevier Science Ltd.