Interaction with orchid mycorrhizal fungi (OMF) is essential to all members of the Orchidaceae, yet we know little about whether or how OMF abundances in substrates shape orchid populations. While root-associated OMF diversity is catalogued frequently, technological constraints have impeded the assessments of OMF communities in substrates until recently, thereby limiting the ability to link OMF communities in a habitat to population responses. Furthermore, there is some evidence that edaphic and microclimatic conditions impact OMF in soil, yet we lack an understanding of the coupled influences of abiotic environment and OMF structure on orchid population dynamics. To discover the linkages between abiotic environment, OMF community structure, and population size, we characterized the microclimatic conditions, soil physicochemistry, and OMF communities hosted by roots and soil across large and small populations of a terrestrial orchid endemic to California Floristic Province in North America. By using high-throughput sequencing of the ITS2 region of nrDNA amplified from root and soil DNAs, we determined that both roots and soil of larger populations, which were high in phosphorus but low in zinc, organic matter, and silt, were dominated by Tulasnellaceae OTUs. In comparison, roots and soil from smaller populations of the orchid hosted higher relative abundances of the Ceratobasidiaceae. In this multiyear, range-wide study that simultaneously measured habitat environmental conditions, and soil and root OMF communities, our results suggest that soil chemistry is clearly linked to soil and root OMF communities, which then likely alter and shape orchid populations.

兰花菌根真菌（OMF）的相互作用对于兰科的所有成员都是必不可少的，但是我们对基质中OMF丰度是否或如何影响兰花种群的了解却很少。尽管与根相关的OMF多样性经常被分类，但是直到最近，技术限制仍阻碍了对底物中OMF群落的评估，从而限制了将栖息地中的OMF群落与种群反应联系起来的能力。此外，有一些证据表明，土壤和有机气候条件影响着土壤中的OMF，但我们对非生物环境和OMF结构对兰花种群动态的耦合影响缺乏了解。为了发现非生物环境，OMF群落结构和种群数量之间的联系，我们表征了微气候条件，土壤物理化学，和OMF群落，由北美和加利福尼亚植物区系特有的陆生兰花的大大小小的种群的根和土壤组成。通过对从根和土壤DNA扩增出的nrDNA的ITS2区域进行高通量测序，我们确定了鸭嘴藻科的主要种群是磷含量高而锌，有机质和淤泥含量低的较大种群的根和土壤。 OTU。相比之下，来自较小兰花种群的根和土壤具有较高的塞拉基底亚科的相对丰度。在这项长达数年，范围广泛的研究中，该研究同时测量了栖息地的环境条件，土壤和根系OMF群落，我们的结果表明土壤化学与土壤和根系OMF群落有着明显的联系，从而可能改变和塑造兰花种群。