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| Titel |
Methane cycling in alpine wetlands - an interplay of microbial communities and vascular plants |
| VerfasserIn |
Ruth Henneberger, Simrita Cheema, Josef Zeyer |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250094230
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| Publikation (Nr.) |
 EGU/EGU2014-9630.pdf |
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| Zusammenfassung |
| Wetland environments play an important role for the global climate, as they represent a major
terrestrial carbon store. These environments are potential sinks for atmospheric carbon due to
reduced decomposition rates of plant material in the waterlogged, anoxic subsurface. In
contrast, wetlands are also a major source of the highly potent greenhouse gas methane
(CH4), which is produced in the anoxic zones through methanogenic archaea (methanogens)
degrading organic matter. The CH4 emitted into the pore water diffuses upwards towards the
surface, and is partially oxidized in the oxic zones by aerobic methanotrophic bacteria
(methanotrophs) before reaching the atmosphere. Nonetheless, global emissions of
atmospheric CH4 from natural wetlands are estimated to range from 100 to 230 Tg
a-1.
Natural wetlands can be found around the globe, and are also common in temperate-cold
climates in the Northern hemisphere. Methane release from these environments is influenced
by many factors (e.g., vegetation, water table, temperature, pH) and shows high
seasonal and spatial variability. To comprehend these variations and further predict
potential responses to climate change, the biotic and abiotic processes involved in
CH4 turnover need to be understood in detail. Many research projects focus on
(sub-)arctic wetland areas, while studies on CH4 emissions from alpine wetlands are
scarce, despite similar processes occurring in these different regions. Recently,
we conducted a survey of 14 wetlands (i.e., fens vegetated with vascular plants)
located in the Swiss Alps, showing CH4 emissions between 74 ± 43 and 711 ±
212 mg CH4 m-2 d-1 (Franchini et al., in press). A detailed study of one fen also
revealed that CH4 emission was highest immediately after snowmelt, followed
by a decrease in CH4 emission throughout the snow-free period (Liebner et al.,
2012).
Even though the CH4 cycle is largely driven by microbially mediated processes, vascular
plants also play a crucial role in CH4 emissions from wetlands, as CH4 generated in the
deeper layers can bypass the oxic, methanotrophic zones through the plant aerenchyma. In
addition, O2 transported to the root system facilitates CH4 oxidation in the rhizosphere. To
further comprehend these complex processes, the present study focused on selected fens
dominated by different plants (i.e., Carex spp. or Eriophorum spp.). We combined
field-measurements of overall CH4 emissions, CH4 and O2 pore water concentrations and
plant-mediated bypass with molecular biological analyses of methanogenic and
methanotrophic subpopulations at different soil depths. Methane emissions and pore water
concentrations varied with location and dominating plant species. Nevertheless, in all fens we
observed the presence of active methanogens and methanotrophs throughout the depth
profile, independently of O2 and CH4 concentrations, with active methanogens being
highly abundant even in the oxic layers indicating the presence of microniches.
The often described spatial separation of methanogenic activity in anoxic zones
and methanotrophic activity in oxic zones and oxic-anoxic interfaces could not be
observed. The composition of the methanogenic and methanotrophic subpopulations
that are active at different depths is currently analyzed in detail, providing new
insights into the complex processes involved in CH4 turnover in alpine regions. |
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