The below-ground (micro-)biome is central to peat biogeochemistry. Rewetting changes the peat microbiome (bacteria, archaea, fungi, protists; Weil et al. 2020; Wang et al. 2021, 2022) and the composition of the micro- and mesofauna as compared to drained fens (Emsens et al. 2020; Jurasinski et al. 2020; Kreyling et al. 2021). These shifts indicate drastically changed functions in the below-ground biome and consequently in the flow of C and energy to higher trophic levels in the food web. We postulate that the lack of oxygen restricts the activity of most micropredators, due to their obligatory aerobic lifestyle. This lowered predation pressure on bacteria and fungi may result in a reduced C turnover and ultimately in soil organic C storage, i.e., a „trophic latch“ on C mineralisation. Using cutting-edge quantitative meta-omics approaches, we aim to assess the consequences of rewetting and limited oxygen availability on the trophic structure and on interactions among prokaryotes, fungi, and fauna in temperate fens. 

In a series of complementary work packages the structure and function of the below-ground (micro-)biome in rewetted fens  will be analysed. 

1. Using > 100 rewetted Screening Sites we will create the first broad census of below-ground biota in rewetted fens.
2. Spatially and temporally resolved sampling and analysis of Core Sites will enable an understanding of the spatio-temporal microbiome dynamics.
3. To verify the hypothesis of a trophic latch on C mineralization, we will conduct microcosm and mesocosm experiments with peat microbiota and model plant species under oxic and anoxic conditions.
4. NGS and amplicon profiling services will be provided for other subprojects. Results will be shared and integrated with the outcomes of other subprojects, especially A3, A5, A6, A7, B3 and S1.