Dr Rachel Hestrin1,2, Dr Edith Hammer3, Dr Carsten Mueller4, Dr Johannes Lehmann2
1Lawrence Livermore National Laboratory, Livermore, United States, 2Soil and Crop Sciences, Cornell University, Ithaca, United States, 3Department of Biology, Lund University, Lund, Sweden, 4Lehrstuhl fur Bodenkunde, Technical University of Munich, Munich, Germany
Arbuscular mycorrhizal (AM) fungi are ubiquitous plant symbionts that can improve plant nitrogen (N) acquisition from organic sources, with implications for soil organic matter (SOM) cycling and soil-climate feedbacks. Recent work shows that interactions with other soil biota mediate AM N acquisition from SOM. We used the stable isotopes 15N and 13C, controlled mesocosms, and soil microbial communities from a N gradient experiment to investigate these complex relationships and their response to long-term N enrichment. Multipartite interactions between plants, AM fungi, and soil microbial communities greatly enhanced total plant biomass and resulted in up to a tenfold increase in plant N acquisition from organic matter. This far exceeded the expected increase in plant N acquisition based on the sum of N taken up when plants were grown alone, grown only with AM fungi, or grown only with soil microbial communities. Like plants, AM fungi acquired more N from organic matter in the presence of soil microbial communities. These synergistic interactions also resulted in a significant increase in microbial utilization of plant-derived carbon, demonstrating an important link between SOM mineralization, AM N utilization, and plant carbon allocation belowground. Long-term N enrichment disrupted these synergies, resulting in diminished plant and fungal N acquisition from organic matter. Taken together, these results shed light upon multipartite biotic interactions involved in SOM cycling and their response to environmental change.
Biography: Rachel Hestrin is a postdoctoral scientist investigating soil nutrient cycling and plant-microbe interactions at Lawrence Livermore National Laboratory. Rachel received her PhD in Soil and Crop Sciences from Cornell University in 2018, where her work focused on nitrogen biogeochemistry, mycorrhizal fungi, and pyrogenic organic matter.