Biodiversity and functional role of biological soil crusts

 

Previous project phase (2014 - 2017)

 

Scientific investigators:

Prof. Dr. Ulf Karsten

Prof. Dr. Peter Leinweber

Dr. Karen Baumann

Dr. Karin Glaser

Samira Khanipour Roshan

(Uni Rostock)

 

Background

Biological soil crusts are complex communities consisting of photosynthetically active green algae, cyanobacteria, bryophytes and lichens, heterotrophic fungi, protozoa and bacteria, which cover the top few millimetres of soil.

The organisms and their by-products create a micro-ecosystem, whose ecological function is of great importance in particular on bare soils (e.g. nitrogen fixation by cyanobacteria, primary production, water retention, soil stabilisation or allocation of plant available nutrients).

Although soil crusts are ecologically important, investigations have been mainly focused on arid and semiarid habitats so far. Hence, in this project soil crust species assemblages of temperate regions should be elucidated and a possible correlation with land use intensity and soil parameters should be investigated.

 

Aims

Investigation of biodiversity within the soil crust should contribute to the identification of relationships among organisms and their reactions to external factors such as e.g. land use intensity.

The functional role of soil crusts in biogeochemical cycles of C and N should be analysed by carrying out mass spectrometric fingerprints (Py-FIMS, pyrolysis field ionisation mass spectrometry) and XANES (X-ray Absorption Near Edge Structure). Different C- and N-containing component classes originating from crusts and adhering soil will be identified and quantified so that an effect of land use intensity on molecules or component classes can be investigated statistically.

P fraction analyses of crust and adhering soil should reveal the ecological function of the soil crust as mineral soil P mobilizer.

 

Hypotheses


1. With increasing land use intensity the abundance of nitrogen fixing cyanobacteria decreases causing a shift in the partner organism community (ammonium oxidizing bacteria and archeae).

2. Increasing land use intensity decreases the biochemical diversity of molecules derived from soil organic matter while at the same time stable, N-containing molecules accumulate.

3. The biological soil crust transforms mineral P fractions into organic fractions. An increase in land use intensity increases the organic P fraction in the soil crust.

 

Methods

  • Cultivation of photosynthetically active organisms
  • Light-microscopy
  • PCR and 454 sequencing
  • Py-FIMS (pyrolysis field ionisation mass spectrometry)
  • C-, N-, P – XANES (X-ray Absorption Near Edge Structure)
  • P-fractionation
  • 31P-NMR (nuclear magnetic resonance)

 

Previous project contribution of Prof. Dr. Ulf Karsten: Soilcrust
Previous project contribution of Dr. Karin Glaser: ACTIFLAG

 

 

Schematic image showing soil crust and adhering transitional zone soil
Soil
Enrichment cultures
Moss
Liverwort
Prof. Ulf Karsten is documenting impressions of the Schorfheide
Empty spot after soil crust removal
Soil crusts and control soil
Soil crust samples on plot SEW 7
Prof. Peter Leinweber samples soil crusts from lower side of fallen beech tree on plot SEW 6
Taking soil crust samples along a skid trail on plot SEW 30
Pyrolysis-field ionisation mass spectrum with corresponing thermogram of total ion intensity (upper insert)

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