The first life stages of a tree are subject to strong environmental stresses and competition, limiting their chances of survival. Establishing a mutualistic relationship with mycorrhizal fungi during early life stages may increase growth and survival rates of trees, but how mycorrhizal communities assemble during these stages remains unclear. Here, we studied variation in the ectomycorrhizal (EcM) fungal communities in the soil and roots of Fagus sylvatica seedlings and saplings. Fungal DNA was extracted from the soil and seedling and sapling roots collected in 156 plots across the beech-dominated Sonian forest (Belgium) and community composition was determined through metabarcoding. EcM fungal community composition significantly differed between soil, seedlings and saplings. Russula, Amanita and Inocybe were most abundant in soil, while Lactarius and Scleroderma were more abundant in seedling and sapling roots and Xerocomellus and Laccaria were most abundant in sapling roots. Our results provide evidence of partner turnover in EcM fungal community composition with increasing age in the early life stages of F. sylvatica.

树木的最初生命阶段受到强烈的环境压力和竞争，从而限制了它们生存的机会。在生命的早期阶段与菌根真菌建立互惠关系可能会提高树木的生长速度和存活率，但是在这些阶段菌根群落的组装方式仍不清楚。在这里，我们研究了青冈（Fagus sylvatica）幼苗和树苗的土壤和根中的外生菌根（EcM）真菌群落的变化。从土壤和幼苗中提取真菌DNA，并在以山毛榉为主的Sonian森林（比利时）的156个样地中收集幼树根，并通过元条形码确定群落组成。EcM真菌群落组成在土壤，幼苗和幼树之间明显不同。鹅膏菌拉斯鲁拉在土壤和幼苗中，Inocybe和Inocybe的含量最高，在幼苗和幼树的根中，乳杆菌和硬皮病的含量最高，在幼树的根中，Xerocomellus和Laccaria的含量最高。我们的研究结果提供了合作伙伴在EcM真菌群落组成中的周转率的证据，表明其在F. sylvatica生命早期阶段的年龄随着年龄的增长而增加。