Interplay between the soil microbiome and tree species richness as well as tree species identity in subtropical forests of China

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Soil microorganisms play a crucial role for the functioning of forest ecosystems by influencing uptake and cycling of nutrients and shaping plant diversity and productivity. In the last decade knowledge on microbial diversity and community structure in soils has been triggered dramatically by advances in sequencing technologies. This opens new avenues to address microbial ecological questions in large and multidisciplinary projects. In the previous phases of the Research Unit BEF-China we used high-throughput pyrotag sequencing to analyse soil microbial communities both in the Comparative Study Plots (CSPs) and in the Main Experiment at both Sites A and B. We found a strong relationship between forest age, plant community and soil microbial community in the CSPs. Results from the Main Experiment indicated clear effects of both tree species identity and tree richness on the soil fungal community already at this early stage of tree seedling establishment. Further shifts in the microbial community composition are to be expected with ongoing growth of the plants. For forest ecosystems it is known that the major part of the primary production is transferred to the soils either as root exudates or as dead organic matter. This defines the rhizosphere and coarse wood debris as two hot spots of plant influence on soil microbial communities in forests. These hot spots are only weakly explored, but can be expected to be of major importance especially in the highly diverse subtropical forests.In the 3rd phase of the BEF-China research unit SP7 will focus on understanding the functional relationships between plant biodiversity and below ground microbial diversity in subtropical forest ecosystems. Both the rhizosphere and coarse wood debris (CWD) will be investigated as the two key soil compartments where cycling and acquisition of nutrients are controlled. Our two objectives are: (1) To analyse changes in the diversity and community composition of the rhizosphere soil microbiomes of single tree species along increasing plant species richness gradients within the BEF-China Main Experiment. (2) To study the impact of tree species identity, wood trait, decay rate, canopy gap and plant diversity levels on the microbial communities decomposing (CWD), using the multi-functionality multi-diversity array (MMA) designed by SP10. We will employ both targeted fungal ITS rDNA pyrotag and prokaryotic 16S rDNA illumina paired end sequencing approaches. Addressing this broad array of the soil microbial communities will enable us to analyse the patterns of cooccurrence and interaction networks of specific functional groups of microbes and the tree species in order to obtain a mechanistic understanding of the plant-microbe interactions in the rhizosphere and CWD hot spots. The results will improve our understanding of the role of the plant microbiome in maintaining plant diversity and productivity in forest ecosystems.