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| Titel |
Analyzing carbon losses from dry soils after precipitation pulses by stable carbon isotopes |
| VerfasserIn |
Stephan Unger, Cristina Máguas, João Santos-Pereira, Christiane Werner |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250040289
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| Zusammenfassung |
| Rain events after drought periods strongly increase soil respiration (Birch effect) and affect
plant activity, and thus, may influence the isotopic signal of ecosystem respiration. These
CO2-pulses may largely affect the C-balance of arid and semi-arid systems. Here, we evaluate
the origins of the Birch effect in a Mediterranean forest and its influence on the isotopic
signal of ecosystem (δ13CR) and soil respiration (δ13CSoil). We conducted artificial rain
pulses in May and August 2005 and estimated δ13CSoil on intact vegetation, bare and
root-free soil in response to watering. After watering in May δ13CSoil showed strong
enrichment (-18) and a rapid return to initial values (-27). This transient enrichment was
smaller in August than in May (ca. -22). Further, we compared δ13CR and δ13CSoil after first
natural rains in October 2005, where both revealed a good relationship over the diurnal and
the fortnight cycle. We hypothesize that the “Birch effect” immediately after irrigation
is the result of a hypo-osmotic stress response of the soil microbial community:
during sudden moisture changes enriched osmoregulants are rapidly released and
mineralized by the soil microbes to avoid cell lysis. After the pulse soil respiration
followed a common moisture response. The overall impact of the Birch effect on
C-sequestration will depend on both timing and frequency of the rains and thus,
on whether the respired CO2 source is microbial or soil organic matter carbon. |
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