Abstract: The existence of orchids strongly depends on their associated mycorrhizal fungi. The research of orchid mycorrhizal fungi (OMF) provides important reference for the conservation of orchids. Here, we took eight species of orchid with extremely small populations in Liaoning as examples to study the fungi diversity of orchids using nextgeneration sequencing technique. The results showed that Amitostigma gracile,Platanthera chlorantha,Goodyera repens and Oreorchis patens preferred to associate with Ceratobasidiaceae. Liparis makinoana preferred to associate with Tulasnellaceae. Cephalanthera longibracteatawas mainly associated with Thelephoraceae and Sebacinaceae.Spiranthes sinensiswas not only associated with Rhizoctonia, but also with Sebacinaceae. Meanwhile, different S. sinensisindividuals growing in the same habitat may choose differentOMF, and different species of orchid growing in the same place may associate with distinct OMF, indicating that the composition of OMF in the roots of orchids may not be completely controlled by orchids. However, the selection of main OMF may still depend on the orchids themselves. Most of the fungi existing in the roots of orchids were non-mycorrhizal fungi, while the abundance of OMF was usually much lower, which may be related to the rarity of orchids in Liaoning, China.

Key words: soil particle-size distribution, fractal dimension characteristics, vegetation mini-patch, desert steppe