Summer freezing resistance decreased in high-elevation plants exposed to experimental warming in the central Chilean Andes

Background/Question/Methods: Predicted warmer temperatures and longer growing seasons could expose high-elevation plants to very low temperatures, increasing their risk to suffer frosts damage, hence decreasing their population viability. Thus, understanding the ability of these species to withstand frosts under warmer conditions is essential for predicting how species may respond to future climate changes. We assessed the freezing resistance of eleven species from the central Chilean Andes by determining their low temperature damage (LT₅₀) and freezing point (FP) after experimental warming in the field. Plants were exposed during two growing seasons to a passive increase of the air temperature using open top chambers (OTCs).

Results/Conclusions: OTCs increased ca. 3K the mean air and soil daytime temperatures, but had smaller effects on freezing temperatures. Overall, high-Andean species growing inside OTCs increased their LT₅₀ ca. 4K, indicating that warming decreased their ability to survive severe frosts. Moreover, plants inside OTCs increased the FP ca. 2K in some studied species, indicating that warming altered processes of ice-crystals formation. Resistance of very low temperatures is a key feature of high-elevation species, but our results suggest that current climate warming trends will seriously threaten the survival of high-elevation plants by decreasing their ability to withstand severe freezing events.