Long-term effects of clear-cutting forestry on ectomycorrhizal fungi in boreal forest

Clear-cutting is detrimental to ectomycorrhizal fungi in a short time perspective, but long-term effects on species richness and community composition are uncertain. To evaluate ecological sustainability of rotation forestry, we examined to what extent communities similar to those in old forests develop within the time frame of a rotation period. We conducted DNA-based analyses of ectomycorrhizal fungal communities in > 1500 sites across Swedish boreal forests and used space for time substitution to analyse the development of species richness, community composition, and abundance with increasing stand age, ranging from recent clear-cuts to 200-yr-old forests. Ectomycorrhizal fungal species richness peaked in 30- to 40-yr-old secondary stands, but community composition remained altered in up to 100-yr-old stands. Certain species in the Atheliaceae family thrived in secondary forests, whereas many Cortinarius and Russula species linked to acidic and unfertile soils were more common in old, natural forests. While Swedish rotation forestry does not appear to decrease species richness, it will progressively change the composition of ectomycorrhizal fungal communities at the landscape level, with species characteristic of acidic and nutrient-poor old-growth boreal forests decreasing in abundance.