Understanding the biogeographic patterns of root-associated fungi and their sensitivity to temperature may improve predictions of future changes in terrestrial biodiversity and associated ecosystem processes, but data are currently limited. Anticipating change will require combining observational data, which predict how climatic factors limit current species distributions, with direct manipulations of climate, which can isolate responses to specific climate variables. Root endophytes are common symbionts of plants, particularly in arctic and alpine environments, yet their responses to climate warming are not resolved. Here, we directly cultured endophytic fungi from roots collected along altitudinal gradients in replicated mountain watersheds and from a 27 y field warming experiment in the Rocky Mountains, USA, to improve understanding of climate impacts on fungal root endophytes. Fungal taxa that were common at high elevations declined most under climate warming, whereas low elevation dominants responded neutrally or increased with experimental warming. Altitudinal gradients in fungal communities were strongly specific to the plant host species. Specifically, Poa species had 25–60% greater fungal isolate abundance and 25–38% greater fungal diversity at high elevations than at low elevation sites. In contrast, Festuca thurberi had 64% lower fungal diversity on roots at high elevation than at low elevation. Our results help to improve understanding of the potential for climate change to alter plant-fungal interactions in mountain ecosystems.

了解与根相关的真菌的生物地理模式及其对温度的敏感性可能会改善对陆地生物多样性和相关生态系统过程未来变化的预测，但目前数据有限。预测变化将需要结合观测数据（可预测气候因素如何限制当前物种分布）和直接操纵气候，从而可以隔离对特定气候变量的响应。根内生植物是植物的常见共生体，特别是在北极和高山环境中，但它们对气候变暖的反应尚未解决。在这里，我们直接在复制的山地流域中从沿海拔梯度收集的根中直接培养内生真菌，并在美国落基山进行了27年的田间变暖实验，增进对气候对真菌根内生植物影响的了解。在气候变暖下，高海拔地区常见的真菌类群下降最多，而低海拔优势种随实验变暖而呈中性响应或增加。真菌群落中的垂直梯度对植物寄主物种具有强烈的特异性。特别，与高海拔地区相比，高海拔地区的Poa物种真菌分离物丰度高25-60％，真菌多样性高25-38％。相反，高海拔的Festuca thurberi根部的真菌多样性比低海拔的低。我们的结果有助于增进对气候变化潜力的理解，以改变山区生态系统中的植物与真菌的相互作用。