1. 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.
2. 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).
3. 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.
4. 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.
5. 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.

中文翻译：

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土地利用历史改变了山毛榉林外生菌根真菌的多样性、群落组成和相互作用网络

1. 在过去的几个世纪里，由于农田（农业和牧场）被遗弃，森林在整个欧洲扩张。农业实践通常会增加土壤肥力并减少外生菌根 (ECM) 真菌的多样性和丰度，外生菌根 (ECM) 真菌是温带和地中海森林中许多木本物种的重要互利者。因此，人类活动停止后这种生物相互作用的恢复对于重新建立功能性森林生态系统至关重要。
2. 在这里，我们解决过去土地利用遗产和ECM真菌之间的共生的回收水青冈树在西班牙东北部最近的山毛榉森林（<50岁）。在六个历史悠久的山毛榉森林和八个最近建立的山毛榉森林中收集土壤和根部样本，以分析土壤非生物特性和与山毛榉根部相关的 ECM 真菌（ECM 尖端的 Illumina DNA 元条形码）。
3. 鉴定了多达 609 个 ECM 真菌的扩增子序列变体 (ASV)，在两种森林类型中都发现了 220 个 ASV。近期森林土壤有机质和磷含量显着降低，这对山毛榉根部ECM真菌群落结构有显着影响。此外，最近森林中的山毛榉树与较少的真菌类群相互作用，但子囊菌的相对丰度较高。塔泽塔属 （子囊菌门，Pezizales）和Lactarius blennius（担子菌门，Russulales）分别作为与新近和长期建立的森林相关的特定分类群出现。
4. 在最近的森林中发现了具有较低物种归一化程度的更专业的互惠网络，这可能导致 ECM 互惠互利的质量和弹性较低。
5. 合成。土地利用历史通过土壤有机质和氮的变化调节了山毛榉森林再生过程中的菌根共生，这是近期森林中与山毛榉树木相关的真菌群落组成和功能类型差异的主要驱动因素。