Land‐use history alters the diversity, community composition and interaction networks of ectomycorrhizal fungi in beech forests

Abstract

Abstract Forests have expanded across Europe over the last centuries as a consequence of farmland (agricultural and pasture) abandonment. Agricultural practices usually increase soil fertility and reduce the diversity and abundance of ectomycorrhizal (ECM) fungi, essential mutualists of many woody species in temperate and Mediterranean forests. The recovery of this biotic interaction after the cessation of human activities is, thus, crucial for the re‐establishment of functional forest ecosystems. Here we addressed the legacies of past land use and the recovery of the mutualism between ECM fungi and Fagus sylvatica trees in recent beech forests (<50 years) in Northeast Spain. Soil and root samples were collected in six long‐established and eight recent beech forests to analyse soil abiotic properties and the ECM fungi associated with beech roots (Illumina DNA metabarcoding of ECM tips). Up to 609 amplicon sequence variants (ASVs) of ECM fungi were identified, with 220 ASVs found in both forest types. Recent forests had a significantly lower soil organic matter and phosphorus content, which had a significant effect on the community structure of ECM fungi in beech roots. Moreover, beech trees in recent forests interacted with less fungal taxa but had a higher relative abundance of Ascomycota. Tarzetta spp. (Ascomycota, Pezizales) and Lactarius blennius (Basidiomycota, Russulales) emerge as the particular taxa associated with recent and long‐established forests respectively. More specialized mutualistic networks with a lower species normalized degree were found in recent forests, which might result in a lower quality and resilience of the ECM mutualism. Synthesis. Land‐use history modulated the mycorrhizal symbiosis in regenerating beech forests through changes in soil organic matter and nitrogen, which were the main drivers of the differences in fungal community composition and functional types associated with beech trees in recent forests.