Functional differentiation of arbuscular mycorrhizal fungi in top- vs. subsoil: do subsoils harbor nutrient acquisition traits supportive for sustainable agriculture?

• Applicant: Dr. Svenja Stock
• Subject Area: Soil Sciences
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 521884211

Monocropping and inefficient resource utilization, accompanied by soil degradation and soil biodiversity loss in conventionally managed agricultural systems, pose challenges to stable food production. Sustainable strategies are needed to ensure food production without (further) compromising the health and functionality of agroecosystems. Arbuscular mycorrhizal fungi (AMF) are the most widespread symbionts among crops and have received increasing attention for their beneficial effects on plant nutrition, promotion of crop resistance, and improving soil stability. Most studies on the benefits of AMF for crop production, however, have focused on AMF in the topsoil, i.e., the thin plow layer in conventionally managed systems. The potential of AMF in agricultural subsoils (i.e., the mineral soil below the plow layer) for sustainable agriculture is rarely studied. While the abundance of AMF decreases from top- to subsoil, it has been shown that subsoils can host a unique set of AMF taxa that are assumed to differ in traits and functionality from topsoil AMF. The main objective of this project is the functional differentiation of top- and subsoil AMF communities with respect to their nutrient acquisition and allocation strategies. The project aims to answer the question of (i) whether subsoils harbor AMF communities with functional traits that are distinct from, or even more diverse than, AMF communities in topsoil, and (ii) whether these traits can be beneficial for sustainable management. DNA amplicon sequencing and metatranscriptome analysis of AMF communities associated to plants of different plant functional groups will allow a first assessment of the functional diversity of subsoil AMF communities, based on the assumption of a trait-based partner selection between plants and fungi. For a further functional characterization, the uptake and transfer of readily available N and K by subsoil AMF communities is assessed using 15N-enriched compounds and trace elements that act as K analogs during nutrient uptake. The stimulation of N and P mobilization from organic matter by AMF subsoil communities is investigated using dual isotopic labeled (15N, 33P) organic matter. With 13CO2-pulse labeling, the carbon allocation of crop plants to different subsoil AMF communities will be analyzed. The project will provide insights into the potential of subsoils as reservoirs for functionally diverse AMF communities and their potential to improve nutrient utilization in agricultural systems. Thereby, the project will help to clarify whether an adequate subsoil management is suitable to promote functional diversity of AMF in agricultural systems, or even target specific functional traits, to help stabilize food production.

• DFG Programme: Research Grants