Soil Crust InterNational

The aim of SCIN (Soil Crust InterNational) is to achieve both better appreciation of the functioning and importance of biological soil crusts (BSCs) in Europe and to add value by contributing to the development of better and simpler soil protection practices and policies. BSCs are the biologically modified soil surface that form naturally in open areas. They are typically composed of cyanobacteria, algae, micro fungi, lichens and bryophytes in varying amounts and can be the only vegetation cover in arid and semi-arid regions such as hot and cold deserts or xerothermic steppe vegetation. BSCs contribute to several ecological services. They are also the first colonizers of disturbed soils and have major impacts on the soil properties through stabilization, erosion limitation, and facilitation of colonization by higher plants. BSCs are thought to contribute as much as 6% of the annual global CO2-fixation and 10-40% of the annual global nitrogen input into the earth`s ecosystems. Despite these immensely important properties that provide protection to large, particularly marginal areas, soil crusts are neither well understood nor well appreciated by conservation and regularity authorities who are missing opportunities for improved policies and actions in the area of land protection. SCIN is a project that will provide a much improved understanding of BSC functionality in Europe, from the severest desert to the alpine ecosystems. Estimates of annual productivity will be achieved through continual, in situ, and monitoring of BSC activity linked to detailed photosynthetic measurements. Rates of change and recovery will be determined leading to indices of sensitivity. The functional studies will be backed by detailed biodiversity assessments that aim to reveal the key organisms in BSC functioning over a wide latitudinal, altitudinal and climatic range. Local adaptations in physiology and genetics will be determined as an important help in restoration projects. Information transfer to stakeholders such as local conservation and land management authorities, and to policy makers will be achieved through a series of consultations and reports including highly visual material that will support the work of these organizations. The use of BSCs as examples in education will be investigated. Small local workshops will be held each year to link the science to stakeholders. Scientific transfer will be achieved by regular publication in peer reviewed journals and the holding of an international workshop in Year 2 of the project (2013). European added value will not only be through policy and protection but by improved scientific excellence through the collaboration of diverse groups targeting BSCs. This will provide a unique opportunity for the transfer of skills and knowledge to young scientists. How common are Biological Soil Crusts (BSC) along the climatic gradient. Key questions: How is their taxonomic composition and how diverse are the BSC itself. How is diversity and productivity linked? What is their role in the referring ecosystems (e.g. N + C input, soil stabilization, enhancement of succession). What do they contribute to the ecosystems CO2-fixation/N-input? How unique are the key species at the different sites.

Biological soil crusts (BSCs) provide important ecosystem services in dryland regions, including erosion control and contribution to nitrogen and CO2 fixation. In the BiodiveERsA framework of the Soil Crust International project we analyzed the microbial communities in BSCs from 4 sampling sites in Europe: (1) Tabernas representing semi-deserts of S Europe, (2) Gössenheim as a temperate dry steppe, (3) Great Alvar of Öland as moist and cool site in N Europe, and (4) Hochtor in the Austrian Hohe Tauern as an alpine site. This sampling range spans over 20 latitude and 2,300 m altitude. Our work in this project covered the characterization of the prokaryotic fraction in BSCs, at the soil surface, below ground, and in association with representative lichens. We used microscopic techniques including fluorescence in situ hybridization and confocal laser scanning microscopy to visualize the bacteria in the samples, and we applied next generation sequencing to characterize the taxonomic composition. The differences at the four sites are described, and potential key taxa are discussed. We also tracked the successional shift of bacterial communities in cases of parasitic interaction among other soil crust members (using the juvenile parasitic lichen Diploschistes muscorum as an example). Since no data were available for Europe we also conducted experiments to study the potential of BSC recovery after disturbance. Beside Cyanobacteria, heterotrophic Proteobacteria, Actinobacteria, Bacteriodetes dominated. Clear stratification of bacterial communities was found, as belowground communities differed in their composition (e.g. with Acidobacteria, Verrucomicrobia and others becoming more dominant). Among the fungi the Ascomycete order Pleosporales were dominant (in lichen-free crusts). Alterations of the dominating fungi leads to a cascade of subsequent shifts, as found by the analysis of a parasitic lichen-fungus Diploschistes muscorum. Infection of the host Cladonia leads to changes in the presence of algal partnerships, and to significant alteration of the associated bacterial community. Experiments also showed that microbial community composition was neither resistant nor resilient to BSC disturbances. These results strongly suggest that severe or repeated disturbances will cause a loss of soil surface material, and represent an important potential threat not only to biodiversity but also to ecosystem services provided by biological soil crusts.