Changing climates are pushing species outside of their evolved tolerances; populations must acclimate or adapt to the new conditions or migrate to avoid extinction. However, because plants associate with diverse microbial communities that shape their phenotype, shifts in microbial associations may provide an alternative source of novel climate tolerance. Here we show that tree seedlings inoculated with microbial communities sourced from drier, warmer, or colder sites displayed higher survival when facing drought, heat, or cold stress, respectively. Microbially mediated drought tolerance was associated with increased diversity of arbuscular mycorrhizal fungi, while cold tolerance was related to reduced diversity of non-adapted taxa. Understanding microbially mediated climate tolerance may enhance our ability to predict and manage the adaptability of forest ecosystems to changing climates.

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