Data from: Mycorrhizal diversity, seed germination and long-term changes in population size across nine populations of the terrestrial orchid Neottia ovata

Orchids rely critically on mycorrhizal fungi for seed germination and seedling establishment, suggesting that the presence of suitable mycorrhizal fungi can exert a major impact on their population dynamics and long-term viability. However, there is little information about the factors determining mycorrhizal availability in natural orchid populations and how it affects orchid population dynamics. In this study, we investigated changes in population size between 2003 and 2013 in 28 populations of the orchid Neottia ovata. In a subset of nine populations, mycorrhizal diversity in both the roots and soil was assessed to test the hypothesis that population size or growth was significantly related to mycorrhizal diversity. Seed germination experiments were performed in situ to test the hypothesis that long-term changes in abundance were related to the ability of seeds to germinate and that seed germination was related to mycorrhizal diversity. Nearly 60% of the studied populations had declined in size (average growth rate across all populations: -0.01). A total of 68 species of putatively mycorrhizal fungi were observed, 21 of which occurred exclusively in roots, 25 that occurred solely in soil and 22 that were observed both in the soil and roots. Seed germination was limited and significantly and positively related to soil moisture content and soil pH, but not to fungal diversity or fungal community composition. Large populations or populations with high population growth rates showed significantly higher germination than small populations or populations declining in size, but no significant relationships were found between population size or growth and mycorrhizal diversity, suggesting that mycorrhizal diversity is not directly limiting the abundance of N. ovata in the study area.兰科植物（Orchids）高度依赖菌根真菌（mycorrhizal fungi）完成种子萌发（seed germination）与幼苗建成（seedling establishment），这表明适宜菌根真菌的存在可对其种群动态（population dynamics）与长期生存力（long-term viability）产生关键影响。然而目前关于自然兰科种群中菌根可获得性的决定因素，以及其如何影响兰科种群动态的相关研究信息仍较为匮乏。本研究针对28个卵形鸟巢兰（Neottia ovata）种群，调查了其2003年至2013年间的种群规模变化。在其中9个种群的子样本中，研究者对根内与土壤中的菌根多样性进行了评估，以检验“种群规模或生长速率与菌根多样性显著相关”这一假说。同时通过原位（in situ）种子萌发实验，验证了“种群丰度的长期变化与种子萌发能力相关，且种子萌发与菌根多样性存在关联”的假说。研究结果显示，近60%的受试种群规模出现下降，所有种群的平均增长率为-0.01。共观测到68种疑似菌根真菌（putatively mycorrhizal fungi），其中21种仅存在于根内，25种仅分布于土壤中，另有22种同时在土壤与根内被检出。种子萌发过程受到限制，其发生率与土壤含水量及土壤pH值呈显著正相关，但与真菌多样性或真菌群落组成无显著关联。种群规模较大或种群增长率较高的种群，其种子萌发率显著高于小型种群或规模衰退的种群；但未发现种群规模或生长速率与菌根多样性之间存在显著关联，这表明菌根多样性并未直接限制研究区域内卵形鸟巢兰的种群丰度。