Seasonal variation in arbuscular mycorrhizal fungal diversity and abundance among adjacent forest and agricultural systems

Arbuscular mycorrhizal fungi (AMF) play a significant role in ecosystem sustainability and plant productivity, improving soil physical properties and facilitating mineral nutrient uptake by plant hosts. Seasonal variation may influence plant-fungal interactions over time, and it is important to understand if this occurs consistently regardless of vegetation type. This study examined communities of AMF in soils over a 12-month period across three different sites representing two agroecosystems (improved pasture and cherry orchard) and a native forest in close proximity within a cool-temperate region of southern Tasmania, Australia. Total AMF abundance was quantified using qPCR. AMF community composition, species richness, and relative abundance were determined using Single Molecule Real Time (SMRT) sequencing with reference to databases optimised for long-read AMF sequences. A total of 147 operational taxonomic units (OTUs) were detected, representing 11 genera, 8 families and 4 orders within Glomeromycota taxa. The majority (78.2%) of AMF taxa were shared among all three sites, with the Glomeraceae dominating all communities, followed by Paraglomeraceae . In this local area, total AMF DNA abundance in soil was 13.2-fold higher in the improved pasture and 8.7-fold higher in the cherry orchard site compared to the native forest. Data analysis showed that AMF community composition across sites was primarily influenced by vegetation cover and soil chemical properties, with key drivers including soil pH, nitrogen content, phosphorus availability, and electrical conductivity. Time of sampling (season) led to similar trends in AMF abundance across all sites, with significant increases observed during warmer months. Overall, the results demonstrate site-level differences in AMF communities within a shared landscape while indicating broadly similar seasonal responses across contrasting vegetation systems. These findings highlight the combined roles of vegetation structure and soil chemistry in shaping AMF communities at a local scale. • Sequencing identified 147 Glomeromycotan OTUs from soil in an Australian study area. • AMF abundance in soils was affected by season, for all vegetation types. • Over 78% of AMF taxa were common to all three sites. • AMF community composition was shaped by vegetation cover and some soil properties.