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| Titel |
Subsurface concentrations and surface emissions of greenhouse gases from a seasonally waterlogged peatland in the UK |
| VerfasserIn |
Alex Boon, Steve Robinson, Laura Cardenas, David Chadwick, Anne Verhoef |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250074612
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| Zusammenfassung |
| Northern peatlands are globally valuable carbon stocks that can act as either sinks or sources
of greenhouse gases (GHGs); carbon dioxide (CO2), methane (CH4) and nitrous oxide
(N2O). We present the results of a year-long field study of subsurface concentrations
and surface emissions of CO2, CH4 and N2O in a seasonally flooded, managed
lowland fen in the UK. This study aimed to determine the extent to which water
status and temperature varies at the site throughout the year and how this affects
both the subsurface production and surface emission of GHGs. Measured GHG
fluxes were compared to estimations using measured subsurface concentrations
with Fick’s Law (gradient method). Fick’s Law was parameterised with either a
measured or a modelled value for the diffusion coefficient for gas transport through
soil.
Water-table depth was shown to be a more significant control on surface GHG emissions
and subsurface concentrations than ambient temperature. CO2 emissions increased as the
water-table lowered from the surface until 35cm, wherein CO2 emissions began to decrease
once more. This break in the relationship was attributed to low available water for respiration
due to drying and competition with plants, and to reduced substrate availability as a result of
prolonged optimal respiration conditions. Subsurface CO2 concentrations showed the
opposite relationship with water-table depth, increasing as the water-table moved toward the
surface. Both CH4 emissions and subsurface concentrations showed an exponential
relationship with water-table depth, increasing dramatically as the soil entered a
flooded condition. N2O fluxes were primarily small and negative throughout the
course of the year. N2O concentrations below the surface in the field under ungrazed
conditions were shown to be low, decreasing even further under flooded conditions,
suggesting full denitrification to N2. The gradient method overestimated emissions
of CO2, CH4 and N2O by up to 500, 200 and 15x respectively. The divergence
between subsurface and surface CO2 became unworkable when combined with an
artifact of overestimation discovered when using silicone rubber soil atmosphere
collectors in saturated or near saturated soils. Further studies into improved methods
for accurate subsurface GHG measurement in waterlogged peat soils are needed. |
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