P-Niche: Parent material and land-use intensity as driver for niche complementarity in phosphorus mobilisation between plants and microbes

• Applicants: Professorin Dr. Nadia Kamal; Professorin Dr. Yvonne Oelmann; Professor Dr. Michael Schloter; Dr. Stefanie Schulz
• Subject Area: Ecology and Biodiversity of Plants and Ecosystems
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 568977277

Phosphorus (P) supply is limited due to its reliance on finite mineral deposits. Additionally, the concentrations of dissolved P species in soil solution are low due to the retention by the soil matrix. Depending on initial parent material properties and land use intensity (LUI), plants and microbes might be forced to develop alternative P acquisition strategies and compete for scarce or difficult to access P resources. For example, P acquisition strategies include the solubilization of inorganic P while mineralization of organic P indicates P recycling strategies. Our overarching objectives are (i) to understand how LUI and its extensification, soil properties and plants determine P acquisition and recycling of microbes, (ii) to identify microbial keystone taxa for P mobilization and their functional redundancy and (iii) to assess the degree to which a functional potential of the soil microbiome translates into real functioning in terms of P mobilization in grasslands. Our project is based on three work packages covering field campaigns in all 150 grassland plots, sample collection in the extensification “Land Use Experiment” (LUX) and controlled isotope labelling-experiments. We will test the following hypotheses: H1: We will observe a gradient from P acquisition to P recycling strategies from high to low LUI being more pronounced in regions with low inherent P contents. H2: Extensification fosters P recycling strategies as well as microbiota with more versatile P mobilization strategies. H3: Plants rely more on P acquisition while soil microorganisms increase P recycling strategies in case of land-use extensification especially at sites with generally low P stocks. At sites with high P stocks additive effects of plants and soil microorganisms can be observed alternatively. H4: During winter, P accumulates in microorganisms, but less so under low LUI because of the microbial use of alternative storage compounds that do not contain P. In spring, accumulated microbial P is turned over and uptake of P by plants starts, which is indicated by an increase of copiotrophic bacteria of versatile mineralization capabilities. The P mobilization from organic sources peaks in summer and this P recycling is most pronounced at low LUI and further reinforced by mowing. With our project we will particularly contribute to the overall Biodiversity Exploratory aims to strengthen in-depth understanding of land use - biodiversity - ecosystem functioning relationships and how these are influenced by temporal dynamics and land use changes. Moreover, we close an important knowledge gap as the consequences of LUI and biodiversity on the P cycle have been barely investigated in the Biodiversity Exploratories in particular and for calcareous soils in general. In a potential second phase of the project, we envision to deepen our understanding about climate-change consequences and biodiversity loss on the identified plant-microbe-soil interactions.

• DFG Programme: Infrastructure Priority Programmes
• Subproject of: SPP 1374: Biodiversity Exploratories
• Co-Investigator: Dr. Amit Fenn