Tree retention levels and prescribed burning effects on ectomycorrhizal fungal communities in a boreal Scots pine forest

Ectomycorrhizal fungi (EMF) form essential symbiotic relationships with trees, supporting nutrient cycling and forest health. However, forestry practices such as clear-cutting disrupt this association, threatening EMF survival. This study investigated the effects of tree retention levels and prescribed burning on EMF abundance, species richness, and community composition in old Scots pine forests 4.5 years after logging. Soil samples were analyzed using DNA sequencing, with stand-level replication. Higher retention levels were associated with increased EMF abundance and diversity, while proximity and size of retention trees significantly influenced outcomes. Species richness declined sharply beyond 5–10 m from retained trees. The greatest declines occurred under minimal retention (3 %) and when prescribed burning was combined with a 50 % harvest. Prescribed burning with 50 % tree removal exacerbated EMF losses in the short-term, likely due to the combined effects of harvesting and fire severity, highlighting the need for careful integration of fire management into forestry practices. Community composition shifted noticeably, with disturbance-tolerant taxa replacing dominant species from older forests. Rare species were disproportionately affected by substantial tree removal, while common species persisted. These findings highlight the importance of retaining higher tree densities and strategically placing retention trees. Sustainable management of old boreal Scots pine forests requires tailored retention strategies and cautious planning of harvesting and prescribed burning to balance biodiversity conservation with forestry objectives. • Tree retention increases ectomycorrhizal fungi abundance and diversity post-harvest. • Proximity and size of retention trees strongly influence fungal species richness. • Prescribed burning + 50 % harvest may worsen EMF losses via higher fire severity. • Rare ectomycorrhizal species decline under low retention and high disturbances. • Tailored retention is crucial for sustainable boreal forest management.