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| Titel |
Estimating the contribution of bryophytes to the atmospheric COS budget |
| VerfasserIn |
Teresa Gimeno, Jerome Ogee, Lisa Wingate |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250148824
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| Publikation (Nr.) |
 EGU/EGU2017-13117.pdf |
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| Zusammenfassung |
| In the past decade, global biogeochemical modellers have embraced enthusiastically the
potential of carbonyl sulphide (COS) as a tracer for gross primary productivity (GPP). COS is
the most abundant sulphur-containing gas in the atmosphere, it is produced mainly in the
ocean and it is consumed by the biosphere, with terrestrial vegetation being the most
important contributor. Plant COS uptake is proportional to photosynthetic CO2 withdraw and
that is why measurements of the biosphere-atmosphere COS flux can serve a proxy for GPP.
Plant COS uptake is mediated by the light-independent enzyme carbonic anhydrase that
irreversibly hydrolyses COS into H2S, which is quickly utilised as a sulphur source.
Currently, there are no described plant-processes with COS as a by-product and
hence the atmospheric-plant COS flux is assumed unidirectional. So far, we had
focused on characterizing plant COS uptake dynamics on vascular plants and previous
studies are consistent with the unidirectional flux assumption. However, although
early works on sulphur metabolism suggested non-vascular plants might not abide
to this assumption, we lack estimates of COS uptake dynamics for non-vascular
communities.
Bryophytes are key constituents of biocrusts and non-vascular photoautrophic
communities and in temperate and cold latitudes contribute significantly to ecosystem carbon
and nutrient cycling. We expect that in these ecosystems the coupling between COS and CO2
uptake will be influenced by specific environmental cues that control gas-exchange in
bryophytes. We expect tissue hydration to be the most influential driver on COS uptake. In
contrast, light would constrain CO2 but not COS uptake and therefore we expect greater
uncoupling of COS and CO2 in the dark than in vascular plants. We characterized COS and
CO2 uptake dynamics in two broadly distributed bryophytes, with contrasting life forms and
evolutionary origins: the liverwort Marchantia polymorpha and the feather moss
Scleropodium purum. We measured CO2 and COS uptake with varying hydration status, light
and temperatures.
Our results showed that COS uptake is limited by either excess or low tissue water
content, similar to photosynthetic CO2 uptake. We found that COS uptake continued in the
dark, despite impaired photosynthesis. We demonstrate that the COS flux in bryophytes is not
unidirectional and that COS emissions are temperature and not light driven. Our results also
suggest that both the uptake and the emission components are subject to seasonal regulation,
with both uptakes limited in winter by low temperatures. Our results serve as a first
approximation to model seasonal COS fluxes from air temperature and humidity in
bryophyte-dominated ecosystems in high latitudes. We suggest that bryophytes might have an
unexpected contribution to the ecosystem COS budget: during the day, when photosynthesis
dominates the CO2 flux, COS emission are enhanced by warmer temperatures, while COS
uptake is limited by tissue hydration and bryophytes act a net COS source; at night
when the temperatures are cool and humidity is high, COS uptake dominates and
bryophytes would act a net COS sink, while continuing to emit CO2 from respiration. |
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