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  • The effects of land use, temperature and water level fluctuations on the emission of nitrous oxide (N2O), carbon dioxide (CO2) and methane (CH4) from organic soil cores in Iceland
  • Meistara
  • Agricultural practices can affect soil microbial production and emission of the major
    greenhouse gases (GHG’s) nitrous oxide (N2O), carbon dioxide (CO2) and methane
    (CH4). The purpose of this study was to gain insight into the influence of temperature,
    water level and water level fluctuations on the GHG emission of soils representing the
    three major types of landuse in Iceland: undisturbed peatland, drained uncultivated
    peatland and hayfield on drained peatland. Twenty-four soil cores, from three different
    areas were set up in controlled laboratory conditions and subjected to varying
    temperatures and water table levels. Vegetation was removed on eighteen of the twentyfour
    soil cores. On six soil cores the vegetation was kept undisturbed to gain information
    on the GHG emission effect of vegetation. Gas samples were collected by a common
    methodology based on a static chamber technique for N2O and CH4 and a dynamic
    chamber method for CO2. The results show that landuse type significantly affects soil
    GHG’s production (P=0.000). Raised temperatures increased the emission of CO2
    (P<0.001) and CH4 (P<0.001) significantly but not the emission of N2O (P=0.458). Water
    level fluctuations (WL), which were only conducted for the drained peatland and hayfield
    soil cores, had a strong influence on soil N2O emission. The N2O emission increased
    significantly (P=0.000) with water level fluctuations for both drained peatland soil cores
    and hayfield soil cores. However, the magnitude of the hayfield on drained peatland
    emission was 3-fold compared to drained soil cores. Water fluctuations increased the
    hayfield soil CO2 emission significantly (P=0.002), but no significant change was
    detected in the emission of the drained peatland soil cores (P=0.086) nor between the
    landuse groups (drained and hayfield) (P>0.005). No CH4 emission change was recorded with soil water fluctuations, which may be due to an insufficiently long incubation time.
    These studies show that draining of peatland increases emission of N2O and CO2 and
    decreases emission of CH4. Temperature had significant effect on the emission of CH4
    and CO2 but not on N2O emission. Water level fluctuations significantly affected N2O
    production in both drained and hayfield soil cores but CO2 production was only
    significantly affected in the hayfield soil cores. Vegetation had significant effect on the
    production of N2O and CO2.
    Here, the highest emission calculated in CO2 equivalents was measured from the
    undrained peatland. The reason for this was the very high methane emission at the highest
    temperatures, 13°C and 18°C. However, if the results are evaluated for each temperature
    compared to average annual temperature in Iceland, the hayfield soil cores emitted most
    GHG’s. From the WL study the highest GHG emission was measured from the hayfield
    soils and secondly from the drained peatland soils.

  • 20.1.2009

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