Structure and function of biocrusts in weathering, soil formation and erosion processes (CRUSTWEATHERING).

• Applicants: Professor Dr. Jörg Bendix; Professor Dr. Burkhard Büdel; Professor Dr. Ulf Karsten; Professor Dr. Peter Leinweber
• Subject Area: Physical Geography
• Term: from 2015 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 280661654

On a global scale, biological soil crusts (biocrusts) form the most productive microbial biomass of the Earth´ -Critical Zone- in arid regions. Biocrusts are formed by living organisms such as heterotrophic bacteria, fungi, lichens, bryophytes, cyanobacteria and algae and their by-products, creating a top-soil layer of inorganic particles bound together by organic materials. They can be characterized as ecosystem-engineers forming water-stable, aggregated surface layers that have important multi-functional ecological roles in primary production, mineralization, bioweathering, dust trapping, and the stabilization of soils, slopes and entire landscapes, thereby affecting the nutrient and hydrological cycles across scales. Intensive literature reviews made us aware, that these communities are almost unstudied in South America, although highly abundant in the study areas of the Priority Programme. Therefore, the objectives of this interdisciplinary proposal are to 1) evaluate the almost unknown community structure of Chilean biocrust types using a combination of field and laboratory methods to address the relative abundance of the full spectrum of biocrust organisms, particularly with regard to their role in weathering and landscape forming processes (who is doing what?); 2) disclose which of the abundant organisms contribute by which biochemical processes to bioweathering, and quantify the reaction rates in relation to community structure and environmental conditions; 3) uncover the function of biocrusts in the coupled biogeochemical cycling of P- (particular emphasis!), C- and N-compounds across spatial scales from the atomic/molecular-, the single mineral grain-, biocrust patch- and soil profile- up to the slope/catchment-scale, the latter with the help of remotely sensed spectral data and jointly developed transfer functions; 4) understand how microclimatic conditions and water availability determine the biocrust community structure and activity, coverage and their functioning in the arid ecosystems. The research will start with a joint field campaign for pedological, geobotanical and physical-geographical site descriptions, observation plot instrumentation, and biocrust and soil samplings. The advanced methodological approaches involve the latest molecular-biological, electron-microscopic, plant physiological, chemical-analytical (mass- and synchrotron-based spectroscopies) and remote sensing techniques, and the corresponding multivariate data evaluation methods. The expected results will not only disclose presently unknown biocrust organisms and their physiological and ecological functioning but also enlighten their contribution to bioweathering and fundamental Earth-shaping processes, and provide overall knowledge and data background for regional or global-scale geosystem models.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1803: EarthShape: Earth Surface Shaping by Biota