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| Titel |
Infiltration, water holding capacity and growth patterns of biological soil crusts on sand dunes under arid and temperate climates |
| VerfasserIn |
T. Fischer, A. Yair, M. Veste |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250062941
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| Zusammenfassung |
| Water repellency and, once wetted, finer pores and grains, pore clogging as well as higher
water holding capacities of biological soil crusts (BSCs) are known to inhibit infiltration and
to promote surface runoff, thereby holding moisture inside the crusts and redirecting rain off
the slope towards the dune base. On the other hand, available water is crucial for growth and
development of crust microphytes, mosses and vascular plants. In a 2-factorial design we
studied the relation between crust microstructure, infiltration and water holding capacity
under arid and temperate conditions (Factor A: Climate) on BSCs sampled along a
catena on mobile sand dunes (Factor B: Catena). The arid and temperate study sites
were located near Nizzana, Israel (precipitation: ~80 mm a-1, PET: ~2500 mm
a-1) and Lieberose, Germany (precipitation: ~600 mm a-1, PET: ~750 mm a-1),
respectively. BSCs were sampled near the dune crest, at the center of the dune slope and
at the dune base at each site. Scanning electron microscopy (SEM) was used to
characterize BSC development and microstructure. Infiltration was determined using
microinfiltrometry under controlled moisture conditions in the lab, water holding capacities
were determined after water saturation of the dry BSCs. Wettability of the crusts was
characterized using a “repellency index”, which was calculated from water and ethanol
sorptivities.
It was found that thickness and density of biogenic elements in the BSCs increased
downslope at each study site and correlated positively with water holding capacities and
negatively with infiltration and wettability with one exception: At the dune base of the
temperate site, where water holding capacity was highest, infiltration and wettability
increased again due to emergence of mosses. It is hypothesized that a positive feedback
between crust growth and surface runoff intensifies downslope, resulting in highest water
availability in the topsoil of the dune base. Under arid conditions, low amounts of total
precipitation as well as extended periods of drought preclude growth of mosses and
vascular vegetation, and facilitate the development of thicker microbiotic crusts.
Under temperate conditions, however, BSCs, initially present in young ecosystems at
the dune base, promote favorable for moss and vascular plant growth moisture
conditions, which then take over. Hence, BSC induced water redistribution has
important implications for the development of vegetational patterns on a dune scale. |
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