Feedback loops between land use intensity, microbial diversity and easily available nutrients on the amount and degradation of phenolic C sources (FeeLoo)

• Applicants: Dr. Sara Louise Bauke; Dr. Qing-Fang Bi; Professor Dr. Michael Schloter; Dr. Marion Schrumpf; Dr. Stefanie Schulz
• Subject Area: Ecology and Biodiversity of Plants and Ecosystems ; Soil Sciences
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 512307488

Phenolic-rich compounds play a major role in organic matter inputs and organic matter turnover in grassland soils. In contrast to other plant-derived substances in soil they are hard to degrade or even toxic for selected microbial taxa. The microbial community involved in the degradation has a low diversity and reduced functional redundancy compared to other microbial groups. Thus, it is assumed that the effects of LUI are more pronounced on degraders of phenolic compounds compared to other plant derived substances in soil. Further the activity of degraders of phenolic compounds in soil is strongly influenced by the availability of other nutrients to ensure stable nutrient stoichiometry in microbial cells. This results in a trade-off between microbial diversity and nutrient availability along the land use intensity gradient of the Biodiversity Exploratories. With this proposal we would like to evaluate, if (1) the microbial community composition is altered along the land use intensity gradients in a way that reduces its functional potential to degrade phenolic compounds. (2) If this causes a feedback loop of reduced activity of oxidative, lignin-degrading enzymes, which leads to a reduced degradation of phenolic compounds derived from plant-litter or root-exudates and (3) if this process is reversible after grassland extensification. To achieve these aims we will combine interdisciplinary expertise from the fields of microbiome analysis, SOM characterization and turnover process analysis, which we will apply in a series of experiments. First, we will characterize SOM quality and nutrient availability as well as the microbial community involved in the degradation of phenolic compounds on all 150 grassland plots to evaluate which consequences a shift in nutrient and microbial composition has on the degradation potential. Second, we will test in a 13C-labelling experiment the effect of LUI on the fate of lignin (as model substance for root debris) and coumaric acid (model root exudate and metabolite of lignin degradation) derived C and identify the actively involved microbes. Thirdly, we will perform a root-litter degradation experiment in extensified LUX plots to evaluate how efficient lignin from root litter is degraded at different LUI and if this can be improved when fertilization of easily available nutrients is skipped. Based on this comprehensive data set we will be able to perform a data synthesis to identify the limiting factors for the efficient degradation of phenolic compounds and significantly improve our mechanistic understanding about the degradation of root litter versus root exudate derived phenolic compounds.

• DFG Programme: Infrastructure Priority Programmes
• Subproject of: SPP 1374: Biodiversity Exploratories