The effect of land use intensity on biodiversity and functional role of biological soil crust communities with an emphasis on the biogeochemical cycling of carbon, nitrogen and phosphorus - CRUSTFUNCTION III

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Biological soil crusts (biocrusts) are microbial biodiversity and activity hotspots acting as “ecosystem-engineers” that drive nutrient (N, P) turnover and stabilize soil surfaces. Biocrusts are characterized by complex community networks integrating various microorganisms with different life styles. However, drivers for the structure and function of biocrusts are fairly unknown, in particular in temperate regions. Thus, we will investigate diversity of biocrust microorganisms (bacteria, protists, fungi, algae) and their biogeochemical role in nutrient cycling in different forest plots of the Biodiversity Exploratories along a land use gradient, and understand how biocrusts are influenced by land use intensity and environmental factors.The centrally organized new disturbance experiment in forest plots offers great opportunity to study the structure and function of biocrusts by following their development from initial to mature stages after strong disturbance: one plot with the removed logs simulates a large clear-cut area, a widely applied method in forest-harvesting; the other plot, where the logs remain, simulates natural tree fall after a storm, extreme events that become more likely in Germany due to climate change. We will follow the structure and function of biocrusts at these experimental sites from young to mature stages over two years by regular inspection (biocrust areal coverage) and sampling (biomass, nutrients, soil organic matter, microbiota) using a combination of field, analytical and molecular methods. We will also participate in the joint soil sampling campaign, visit all 150 forest plots and sample biocrusts.We will quantify the microbial biomass in biocrusts, identify their community structure by high-throughput-sequencing/metagenomics, and link these results to the nutrient turnover of N and the poorly studied P-cycle by using a well-established qPCR approach. To identify and visualize key players with high spatial resolution in the nutrient cycling, we will conduct a lab experiment applying stable isotope probing and NanoSims. The obtained data on biodiversity and functional genomic will be linked to the nutrient status of the biocrusts, for which concentrations and most important chemical species of C, N and P will be quantified. The lab experiment with stable isotopes will lead to a fundamental understanding on the key players of nutrient cycling and their spatial heterogeneity. Finally, this allows for the first time the reconstruction of qualitative and quantitative major nutrient cycles and microbial interaction patterns in biocrusts in response to land use intensity and disturbance. The obtained data will be integrated into the joint soil network in the Biodiversity Exploratories, and will be the nucleus for a synthesis proposal, which aims to qualitatively and quantitatively compare the performance of biocrusts with other microbial hotspots in soils (detitrus-/rhizosphere).