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| Titel |
The CO2 exchange of biological soil crusts in a semiarid grass-shrubland at the northern transition zone of the Negev desert, Israel |
| VerfasserIn |
B. Wilske, J. Burgheimer, A. Karnieli, E. Zaady, M. O. Andreae, D. Yakir, J. Kesselmeier |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 5, no. 5 ; Nr. 5, no. 5 (2008-10-21), S.1411-1423 |
| Datensatznummer |
250002836
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| Publikation (Nr.) |
 copernicus.org/bg-5-1411-2008.pdf |
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| Zusammenfassung |
| Biological soil crusts (BSC) contribute significantly to
the soil surface cover in many dryland ecosystems. A mixed type of BSC,
which consists of cyanobacteria, mosses and cyanolichens, constitutes more
than 60% of ground cover in the semiarid grass-shrub steppe at Sayeret
Shaked in the northern Negev Desert, Israel. This study aimed at
parameterizing the carbon sink capacity of well-developed BSC in undisturbed
steppe systems. Mobile enclosures on permanent soil borne collars were used
to investigate BSC-related CO2 fluxes in situ and with natural moisture supply
during 10 two-day field campaigns within seven months from fall 2001 to
summer 2002. Highest BSC-related CO2 deposition between –11.31 and
–17.56 mmol m−2 per 15 h was found with BSC activated from rain and
dew during the peak of the winter rain season. Net CO2 deposition by
BSC was calculated to compensate 120%, –26%, and less than 3% of
the concurrent soil CO2 efflux from November–January, February–May
and November–May, respectively. Thus, BSC effectively compensated soil
CO2 effluxes when CO2 uptake by vascular vegetation was probably
at its low point. Nighttime respiratory emission reduced daily BSC-related
CO2 deposition within the period November–January by 11–123% and
on average by 27%. The analysis of CO2 fluxes and water inputs from
the various sources showed that the bulk of BSC-related CO2 deposition
occurs during periods with frequent rain events and subsequent condensation
from water accumulated in the upper soil layers. Significant BSC activity on
days without detectable atmospheric water supply emphasized the importance
of high soil moisture contents as additional water source for soil-dwelling
BSC, whereas activity upon dew formation at low soil water contents was not
of major importance for BSC-related CO2 deposition. However, dew may
still be important in attaining a pre-activated status during the transition
from a long "summer" anabiosis towards the first winter rain. |
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