University of Veterinary Medicine Vienna Arbuscular mycorrhizal fungal families and exploration‐based guilds exhibit distinct responses to long‐term N, P and K deficiencies and imbalances Many agroecosystems face nitrogen (N), phosphorus (P) or potassium (K) deficiencies due to imbalanced or insufficient nutrient replenishment after biomass harvest. How this affects the symbiosis between plants and arbuscular mycorrhizal fungi (AMF) and the abundance of exploration-based AMF guilds (rhizophilic, edaphophilic and ancestral) remains largely unknown. We studied a 70-yr nutrient deficiency experiment in a managed grassland in central Austria, where aboveground biomass was harvested three times annually. N, P and K were fully, partially or not replenished, causing long-term nutrient deficiencies and imbalances. We analysed AMF communities in soil and roots by DNA/RNA amplicon sequencing and fatty acid biomarkers, alongside soil and plant community properties. Soil AMF communities were affected by N and P deficiencies, while root AMF communities were most susceptible to K deficiency, showing up to 50% biomass reduction, particularly when N was abundant. We observed a shift from rhizophilic to ancestral guilds under P deficiency in soil, and under K deficiency in roots. Families within each guild, particularly ancestral, showed differential responses, indicating complementary nutrient specializations at the family level. Our findings underscore the previously unrecognized role of K deficiency in AMF symbiosis and suggest the existence of nutrient-related functional subgroups within exploration-based AMF guilds. https://phaidra.vetmeduni.ac.at/o:5457 en TEXT journal article Wissenschaftlicher Artikel Articolo scientifico Text journal article Text Wissenschaftlicher Artikel Documento PDF Articolo scientifico Keywords AMF abundance and community composition ancestral arbuscular mycorrhizal fungi edaphophilic exploration-based functional guild long-term nutrient deficiencies and imbalances managed grassland rhizophilic 2026 2026 Kian Jenab Lauren Alteio Ksenia Guseva Stefan Gorka Sean Darcy Lucia Fuchslueger Alberto Canarini Victoria Martin Julia Wiesenbauer Felix Spiegel (Centre for Food Science, Clinical Department for Farm Animals and Food System Transformation, Departments, University of Veterinary Medicine Vienna) Bruna Imai Hannes Schmidt Karin Hage‐Ahmed Erich M. Pötsch Andreas Richter Jan Jansa Christina Kaiser Wiley