We investigated arbuscular mycorrhizal (AM) fungal communities in secondary forests and/or Chamaecyparis obtusa plantations at eight study sites in Japan’s temperate region. In the secondary forests, AM plants of the families Lauraceae, Sapindaceae, Rutaceae, Araliaceae, Rosaceae, Magnoliaceae, Cornaceae, Piperaceae, and Anacardiaceae were found. The AM fungal communities were evaluated based on compositions of the AM fungal operational taxonomic units (OTUs), which were clustered at a 97% similarity threshold of the sequences of a partial small subunit of a nuclear ribosomal RNA gene obtained from the plant roots. The compositions of AM fungal OTUs were significantly correlated with the plant family compositions and were significantly differentiated among the study sites and between the study forests. Interestingly, only 19 OTUs remained after selecting for those that had more than 1.0% of the total reads, and these 19 OTUs accounted for 86.3% of the total rarefied reads that were classified into 121 OTUs. Furthermore, three dominant OTUs constituted 48.0% of the total reads, and the most dominant OTU was found at all study sites, except at one. These results indicate that AM fungal communities are primarily constituted by limited AM fungal taxa in the forest ecosystems with diverse plant taxa in Japan’s temperate region. The results of basic local algorithm search tool (BLAST) searches against MaarjAM, a database of AM fungal sequences, also revealed that the AM fungi which were the three dominant OTUs are distributed in forest ecosystems on a worldwide scale.

中文翻译：

---

日本温带地区森林生态系统中的丛枝菌根真菌群落可能主要由有限的真菌类群组成。

我们调查了次生林和/或Chamaecyparis obtusa中的丛枝菌根（AM）真菌群落日本温带地区八个研究地点的人工林。在次生森林中，发现了月桂科，Sapindaceae，Rutaceae，Araliaceae，Rosaceae，Magnoliaceae，Cornaceae，Piperaceae和Anacardiaceae的AM植物。基于AM真菌操作分类单位（OTU）的组成对AM真菌群落进行了评估，该分类单位聚集在从植物根部获得的核糖体RNA基因的部分小亚基序列的97％相似性阈值上。AM真菌OTU的组成与植物科组成显着相关，并且在研究地点之间和研究森林之间也有明显区别。有趣的是，在选择读取次数占总读取量1.0％以上的OTU之后，仅剩下19个OTU，而这19个OTU占86个。归入121个OTU的所有稀有读物的3％。此外，三个主要OTU占总读取量的48.0％，在所有研究地点（一个处除外）都发现了最主要的OTU。这些结果表明，在日本温带地区森林生态系统中，AM真菌群落主要由有限的AM真菌分类组成。基本本地算法搜索工具（BLAST）针对Maarj的搜索结果AM，AM真菌序列的数据库，还揭示了AM真菌，这是三个主要的OTU，在全球范围内分布在森林生态系统中。