Biological Soil Crusts 
Linking ecophysiology and soil processes

Biocrusts on reclaimed post-mining site, Lower Lausatia, GermanyMoss-soil lichens crust at reclaimed post-mining site, Brandenburg, GermanyBiocrust wetness sensorsDevelopment of biocrusts and their application in restoration ecologySpatial analysis of photosynthesis using Imaging-Chlorophyll FluoresenceNDVI images of biocrusts with a modified consumer cameraCyanobacterial biocrust on desert dunes, Succulent Karoo, South AfricaMoss-soil lichens crust covering inland dunes, Lieberoser Heide, BrandenburgSoil lichens crust, Karoo, South AfricaInitial green-algae soil crust on temperate sand dunes, Brandenburg, Germany

Biocrusts as drivers for ecosystem functions and development on reclaimed post-mining sites in Lower Lusatia, Germany

Surface mining activities are often large scale disturbances, which affects entire landscapes and ecosystem processes. Those reclaimed ecosystems undergo long time periods of succession for full recovery. These initial soils, consisting of excavated and dumped material, are characterized by a high vulnerability to erosion, low water holding capacity, lack of nutrients, low pH or sparse vegetation. Stress tolerant microorganisms colonize the new soil surface in reclaimed areas. On the upper few millimeters of the topsoil they are forming a biological soil crust (biocrust); containing cyanobacteria, bacteria, green algae, mosses, lichens and fungi, which crosslink soil particles. The successional development of biocrusts communities and the resulting spatiotemporal heterogeneity of biocrust patches in the landscape depend on various abiotic factors e.g. surface stability, soil chemistry, microclimate and surface wetness. The different successional stages are characterized by different composition and structures, which vary from initial green algae dominated biocrusts to moss-soil lichens crusts. We investigate the influence of biocrust succession on ecosystem processes on different reclaimed soils in the open-cast lignite mining district of Lower Lusatia (Brandenburg, NE Germany). 

Photosynthetic activity and community respiration are measured in relation to successional stage and species composition. The ecophysiological processes of the biocrusts organisms are highly dependent on water availability, differing in time and space. Therefore, the determination of spatial biocrust activity and photosynthetic capacity are linked by using latest digital imaging systems for NDVI and imaging chlorophyll fluorescence analysis in the lab and field, and additionally climatic parameters (radiation, temperature, precipitation) and surface wetness duration. 

Field experiments are carried out on the Research Platform Chicken Creek / Quellberg Hühnerwasser and at the inland sand dunes of the Lieberoser Heide (Brandenburg). 

The project is funded by the Geschwister-Staude-Stiftung / University of Hohenheim (2016-2017).


Investigations of biological soil crust on the Research Platform Chicken Creek / Quellberg Hühnerwasser 

Ecological functions of biocrusts in arid sand dunes 

Sand dunes occur in many parts of the world, not only in deserts and other arid regions but also along many coastlines in humid biomes and environments.  Biological soil crusts plays important role for ecosystem processes is desert ecosystems. Biocrusts influencing the ecosysten processes: they decrease infiltration rates and, thus, run-off could be observed even in a sandy area when covered by a biological crust. In addition to the influence on the ecohydrological conditions, the biological crust also stabilises the topsoil, reduces soil erosion, and enhances the nitrogen pools by nitrogen fixation. Long-term investigations on ecological functions and development of various biocrusts types were carried out  in the Negev desert (Nizzana test site)  and in China. The sand dunes of the north-western Negev are the eastern most part of the sand field covering the northern part of the Sinai Peninsula and the northwestern Negev. The climate is determined by a sharp gradient from semi-arid in north to the arid in the south. 

Read more about biocrusts in deserts...

Development of biocrusts in initial ecosystems in the temperate zone

The spatial and temporal variance of biocrust formations and their impact for soil hydrology, carbon accunulation and biological nitrogen fixation. As photoautotroph microbiotic communities they contribute to carbon accumulation and soil formation of initial soils. Furthermore, they change hydrological properties of the soil surface and alternate sub-critical water hydrophobicity. Spatial and temperal variance of photosynthesis of biocrusts from the temperate zone using chlorophyll fuorescence and NDVI measurements are related to biocrusts pattern.

Read more about biocrusts in inital ecosystems...

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