Tropical Forest Soil Microbiome Modulates Leaf Heat Tolerance More Strongly Under Warming than Ambient Conditions

Tropical forests are increasingly threatened by climate change. Yet, it is still unclear how tropical plants respond to increasing temperatures. Leaf heat tolerance (LHT) in tropical plants is often at its upper limit, suggesting that climate change might negatively impact tropical forests. We hypothesized that intraspecific variation in this leaf trait might be associated with changes in the soil microbiome, which might also respond to climate. Specifically, we hypothesized that warming would increase LHT through changes in the soil microbiome: this study combined an in-situ tropical warming experiment with a shade house experiment in Puerto Rico. In the field, seedlings from ambient temperature plots showed higher FV/Fm values under high temperatures than seedlings from the warming plots. In the shade house, the soil microbiome treatments significantly altered leaf heat tolerance and raw FV/Fm values, more so for seedlings grown with soil inoculum from the warmed plots.