Prof. Dr. Peter Leinweber (assoc.)
Dr. Karen Baumann (assoc.)
(Helmholtz Zentrum München)
Prof. Dr. Michael Schloter (assoc.)
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. In the first phase we focused on the biodiversity in soil crusts and their function in biogeochemical phosphorus turnover. These correlations were analysed in greater depth during the second phase. In the current phase spatial distribution of nutrient turnover in biocrusts will be investigated as well as their recovery after ecosystem disturbance.
We plan to link phosphorous turnover and nitrogen cycling in biological soil crusts to the abundance and diversity of genes coding for selected functions driving N and P transformation processes and relate the data to the structure of the crust communities and compare those to other microbial hotspots like the detritusphere and rhizosphere. This project will improve our understanding on the biodiversity and interactions of ALL organisms in biocrusts from forest plots of the BEs.
A combination of metagenomic and fatty acid profiling of the community structure of bacteria, archaea, fungi, cyanobacteria and algae will be evaluated for the first time in taxonomic depth (who is there in what numbers?). Further we will use stable isotopes to identify nutrient hotspots in biocrusts and combine this with transcription analyses of microbial groups involved in N and P turnover (Where happens what?).
The abundance and functional composition of biocrusts will be evaluated after severe surface disturbances due to tree felling will be investigated. The recovery of biocrusts will be related to their organismic diversity, the land use intensity of the forest and biogeochemistry of P and N. The concentrations and chemical species of these elements will indicate whether BSCs act as sink or source for P-and N-compounds after disturbance (who is doing what?).
1. Biocrust communities play a key ecological role in the biogeochemical, often interlinked cycles of N, P and C in forests. Biocrust communities are involved in transformation from inorganic to organic fractions in the biogeochemical cycling of P and N.
2. Biocrust microorganisms prefer organic N molecules. A high availability of N will also increase the mobilisation of P in order to maintain intracellular N:P homeostasis of microorganisms.
3. Functional pattern of biocrusts depend less on the level of disturbance then on site specific properties. Strong disturbance at plots with low silvicultural management intensity will result in a faster development of biocrusts.
4. Functional pattern of biocrusts differ from those of the rhizosphere and detritusphere at the same site (all microbial hotspots).
- Metagenomic and transcriptomic analyses
- Amplicon Sequencing of 16S rRNA and 18S rRNA genes
- qPCR targeting specific genes for N- and P-turnover
- fatty acids analyses
- total C, N, P determination
- NanoSIMS and stable isotopes
Previous project contribution of Dr. Stefanie Schulz: ForNit