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| Titel |
Dew formation on the surface of biological soil crusts in central European sand ecosystems |
| VerfasserIn |
T. Fischer, M. Veste, O. Bens, R. F. Hüttl |
| 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 ; 9, no. 11 ; Nr. 9, no. 11 (2012-11-20), S.4621-4628 |
| Datensatznummer |
250007400
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| Publikation (Nr.) |
 copernicus.org/bg-9-4621-2012.pdf |
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| Zusammenfassung |
| Dew formation was investigated in three developmental stages of biological
soil crusts (BSC), which were collected along a catena of an inland dune and
in the initial substrate. The Penman equation, which was developed for
saturated surfaces, was modified for unsaturated surfaces and used for
prediction of dewfall rates. The levels of surface saturation required for
this approach were predicted using the water retention functions and the
thicknesses of the BSCs. During a first field campaign (2–3 August 2011),
dewfall increased from 0.042 kg m−2 for the initial sandy substrate to
0.058, 0.143 and 0.178 kg m−2 for crusts 1 to 3, respectively. During a
second field campaign (17–18 August 2011), where dew formation was recorded in
1.5 to 2.75-h intervals after installation at 21:30 CEST, dewfall
increased from 0.011 kg m−2 for the initial sandy substrate to 0.013,
0.028 and 0.055 kg m−2 for crusts 1 to 3, respectively. Dewfall rates
remained on low levels for the substrate and for crust 1, and decreased
overnight for crusts 2 and 3 (with crust 3 > crust 2 > crust 1
throughout the campaign). Dew formation was well reflected by the model
response. The suggested mechanism of dew formation involves a delay in water
saturation in near-surface soil pores and extracellular polymeric substances
(EPS) where the crusts were thicker and where the water capacity was high,
resulting in elevated vapor flux towards the surface. The results also
indicate that the amount of dewfall was too low to saturate the BSCs and to
observe water flow into deeper soil. Analysis of the soil water retention
curves revealed that, despite the sandy mineral matrix, moist crusts
clogged by swollen EPS pores exhibited a clay-like behavior. It is
hypothesized that BSCs gain double benefit from suppressing their
competitors by runoff generation and from improving their water supply by
dew collection. Despite higher amounts of dew, the water availability to the
crust community decreases with crust development, which may be compensated
by ecophysiological adaptation of crust organisms, and which may further
suppress higher vegetation or mosses. |
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