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| Titel |
Estimating global nitrous oxide emissions by lichens and bryophytes with a process-based productivity model |
| VerfasserIn |
Philipp Porada, Ulrich Pöschl, Axel Kleidon, Christian Beer, Bettina Weber |
| 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 |
250148975
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| Publikation (Nr.) |
 EGU/EGU2017-13285.pdf |
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| Zusammenfassung |
| Lichens and bryophytes have been shown to release significant amounts of nitrous oxide
(N2O), which is a strong greenhouse gas and atmospheric ozone - depleting agent. Relative
contributions of lichens and bryophytes to nitrous oxide emissions are largest in dryland
and tundra regions, with potential implications for the nitrogen balance of these
ecosystems. So far, this estimate is based on large-scale values of net primary productivity
of lichens and bryophytes, which are derived from empirical upscaling of field
measurements. Productivity is then converted to nitrous oxide emissions by empirical
relationships between productivity and respiration, as well as respiration and nitrous oxide
release.
Alternatively, we quantify nitrous oxide emissions using a global process-based
non-vascular vegetation model of lichens and bryophytes. The model simulates
photosynthesis and respiration of lichens and bryophytes directly as a function of climatic
conditions, such as light and temperature. Nitrous oxide emissions are then derived from
simulated respiration, assuming a fixed relationship between the two fluxes, which
is based on laboratory experiments under varying environmental conditions. Our
approach yields a global estimate of 0.27 (0.19 - 0.35) Tg N2O yr−1 released by
lichens and bryophytes. This is at the lower end of the range of a previous, empirical
estimate, but corresponds to about 50 % of the atmospheric deposition of nitrous
oxide into the oceans or 25 % of the atmospheric deposition on land. We conclude
that, while productivity of lichens and bryophytes at large scale is relatively well
constrained, improved estimates of their respiration may help to reduce uncertainty of
predicted N2O emissions. This is particularly important for quantifying the spatial
distribution of N2O emissions by lichens and bryophytes, since simulated respiration
shows a different global pattern than productivity. We find that both physiological
variation among species as well as variation in climatic conditions are relevant for
variation in respiration and, consequently, N2O emissions simulated by LiBry. To
constrain our predictions, field observations of respiration in combination with a more
process-based approach for relating nitrous oxide emissions to respiration may be
helpful. |
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