Strong family- and guild-specific responses of arbuscular mycorrhizal fungi to long-term deficiencies and imbalances of N, P and K

Abstract

Many agroecosystems face nitrogen (N), phosphorus (P) or potassium (K) deficiencies due to imbalanced or insufficient nutrient replenishment after plant biomass harvest. How this affects the symbiosis between plants and arbuscular mycorrhizal fungi (AMF), and the abundance of exploration-based AMF guilds (i.e., rhizophilic, edaphophilic, ancestral) remains largely unknown. We studied a 70-year nutrient-deficiency experiment in a managed grassland in central Austria, where aboveground biomass was harvested three times annually. Nitrogen, phosphorus and potassium were fully, partially, or not replenished, causing strong 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 changes. Soil AMF communities were primarily affected by N and P deficiencies, while root AMF communities were most susceptible to K deficiency, with a 50% reduction in root AMF biomass. We observed distinct, guild- and family-specific responses: edaphophilic AMF declined with nitrogen deficiency, while rhizophilic fungi decreased with phosphorus and potassium deficiencies. Families within each guild, particularly ancestral ones, exhibited 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.

Competing Interest Statement

The authors have declared no competing interest.