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| Titel |
Development and hydrology of biological soil crusts -- first results from a
surface inoculation experiment |
| VerfasserIn |
Larysa Mykhailova, Thomas Raab, Stella Gypser, Thomas Fischer |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250126411
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| Publikation (Nr.) |
 EGU/EGU2016-6129.pdf |
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| Zusammenfassung |
| Representing a set of various micro-biocoenoses, biocrusts often reside in adjacent patches,
which not necessarily relate to structural elements of the habitat, like (micro-) topography or
vegetational patterns. Such biocrust patches may become more stable through the formation
of mutually dependent ecohydrological regimes. For example, algal patches inhibiting
infiltration and generating runoff alternate with runoff-receiving moss patches possessing
high water holding capacities. Here, we preliminarily report on a lysimeter field experiment
where natural biocrust isolates were used for surface inoculation to (I) prove stochastic vs.
deterministic biocrust development and (II) to quantitatively relate biocrust development to
soil hydrology. Lysimeter sand was collected from 3-4 m below surface at natural dune
outcrops in south-eastern Brandenburg, Germany (Glashütte (GLA) and Neuer Lugteich
(LUG)), where biocrust samples were collected at the respective dune bases. The lysimeters
were designed to prevent runoff. In a completely randomized full-factorial design, three
factors were considered. (A) Inocolum in three treatments (bare control, mosses,
algae), (B) mineral substrate texture in two treatments (GLA: 55% and LUG: 79%
particles >630 μm), and (C) surface compaction in two treatments (control, 41.5 kN
m−2 for 30 seconds). The samples were kept dry and re-moistened to -60 hPa two
days before inoculation. After a species inventory, the inoculate was isolated by
gently washing off sand particles from the biocrust samples. Algal/lichen crusts were
dominated by Zygogonium ericetorum and Cladonia sp. at both sites. All moss
crusts were dominated by Polytrichum piliferum and Ceratodon purpureus, whereas
Brachythecium albicans was present at GLA only. 20 g of homogenized moist inoculate were
spread over the surface of each lysimeter (Ø 19 cm, 22 cm depth). We performed
autochthonous inoculation, i.e. biocrust isolates collected from GLA were used for
inoculation of GLA substrate etc. The experiment started at 12.02.2015 and was located
at an open area in the vicinity of a meteorological station, where all relevant for
HYDRUS modeling data, as well as global radiation have been recorded every 10 min.
Crust development was monitored by non-destructive NDVI imaging and a per
lysimeter determination of the areal share of biocrust developmental stages: mineral
surface (NDVI ≤ 0), BSC1 (0 < NDVI ≤ 0.15), BSC2 (0.15 < NDVI ≤ 0.40)
and BSC3 (NDVI > 0.40). The general water balance equation and the amount
of lysimeter leachate were used to determine evaporation and changes in water
stocks by regular weighing. Biomass growth was inhibited in summer compared to
autumn, where mosses developed faster than algae. Finer grained substrate promoted
biocrust growth. Evapotranspiration increased with biomass development, presumably
because the amount of water held close to the surface increased with biomass. It
can be expected that this effect strengthens with increasing amounts of silt and
clay. Biodiversity studies are pending, but incipient biocrust growth in the controls
points to atmogenic superinfection. So far, it can be concluded that availability
of water, depending on both precipitation and substrate texture, were the driving
factors of biocrust development. Apart from runoff losses in hillslope conditions,
biocrusts are hypothesized to take advantage over their vascular competitors by
preventing water infiltration into deeper soil through increased evapotranspiration. |
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