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Native Andean–Patagonian Nothofagus forests harbour a unique diversity of microorganisms with diverse ecological roles. Although ectomycorrhizal associations constitute an important fragment of the biota associated with these forests, the factors affecting such communities are largely unknown. We investigated the biodiversity, relative abundance, and composition of ectomycorrhizal fungal communities in relation to two host tree species and ages and the soil properties in six monospecific and mixed evergreen–deciduous Nothofagus forests. We used the internal transcribed spacer (ITS2) region by sequencing 9,600 ectomycorrhizae (ECM) root tips for the identification of fungi. In total, 1,125 fungal taxa at the genus level distributed over 131 orders were identified. The phyla Ascomycota (34.5%) and Basidiomycota (62.1%) were the most abundant, whereas Mucoromycota (3.1%), Chytridiomycota, Cryptomycota, Olpidiomycota, and Zoopagomycota occurred less frequently. The highest taxon diversity was found in old trees, whereas young trees often exhibited a lower diversity of the associated fungi. The fungal taxa were grouped into seven broad ecological categories, of which saprotrophic associations were most common, followed by pathotrophic, pathotrophic–saprotrophic–symbiotrophic, pathotrophic–saprotrophic, and symbiotrophic associations. We did not detect significant differences in the number of taxa in each category between young and old N. dombeyi and N. obliqua. Overall, the scale of the Illumina sequencing approach allowed us to detect a fungal taxa diversity that would not be possible to find through surveys of fruiting bodies alone and that have never been observed in Nothofagus forests before. Our findings suggest the impact of the proximity between sites, the similarity of the soil conditions, and anthropogenic use of the forests on the belowground fungal community’s diversity and composition. Furthermore, there were differences between above- and belowground occurrences of the edible mushrooms B. loyo and Ramaria spp. However, future research, including on EMC tips found beneath fairy rings could provide significantly better correlations with the occurrence of aboveground fruiting body.

安第斯-巴塔哥尼亚原生南山毛榉（Nothofagus）林蕴藏着兼具多样生态功能的独特微生物多样性。尽管外生菌根（ectomycorrhizal）共生体是这类森林关联生物群落的重要组成部分，但目前学界对影响此类真菌群落的核心因素仍知之甚少。本研究针对6处单优种及常绿-落叶混交南山毛榉林，探究了外生菌根真菌群落的生物多样性、相对丰度及群落组成，并分析其与两种宿主树种、树龄及土壤理化性质的关联。本研究通过对9600条外生菌根（ECM）根尖进行测序，靶向内转录间隔区2（ITS2）以完成真菌物种鉴定。总计鉴定得到隶属于131个目的1125个属级真菌分类单元。其中丰度最高的门类为子囊菌门（Ascomycota，34.5%）与担子菌门（Basidiomycota，62.1%），而毛霉门（Mucoromycota，3.1%）、壶菌门（Chytridiomycota）、隐真菌门（Cryptomycota）、油壶菌门（Olpidiomycota）及捕虫霉门（Zoopagomycota）的占比相对较低。老龄宿主树木的真菌分类单元多样性最高，而幼龄宿主树木的共生真菌多样性通常较低。研究将所鉴定的真菌分类单元划分为7大类生态功能群，其中腐生型共生体最为常见，其次依次为寄生型、寄生-腐生-共生混合型、寄生-腐生混合型及共生型共生体。在幼龄与老龄的智利南山毛榉（N. dombeyi）及歪叶南山毛榉（N. obliqua）之间，各生态功能群的分类单元数量均未检测到显著差异。总体而言，本研究采用的Illumina测序技术足以检测到仅通过子实体调查无法发现的真菌多样性，且此类多样性此前从未在南山毛榉林中被观测到。研究结果表明，样地间的空间邻近性、土壤条件的相似性以及森林的人为开发利用活动，均会对地下真菌群落的多样性与组成产生影响。此外，可食用真菌洛约牛肝菌（B. loyo）与枝瑚菌属（Ramaria spp.）的地下与地上分布存在显著差异。不过未来的研究（包括针对蘑菇圈下的外生菌根根尖开展的调查），将有望更精准地揭示地下真菌群落与地上子实体出现情况之间的关联。