Thermal Decoupling May Promote Cooling and Avoid Heat Stress in Alpine Plants

In alpine ecosystems, where low temperatures dominate, prostrate growth forms play a crucial role in thermal resistance by enabling thermal decoupling from ambient conditions, creating a warmer microclimate. However, this strategy could be maladaptive during the heatwaves driven by climate change. This study combined microclimatic and plant characterization, infrared thermal imaging, and leaf photoinactivation to evaluate how thermal decoupling affects heat resistance (LT50) in six alpine species from the Nevados de Chillán volcano complex in the Andes of south-central Chile. Results showed plant temperature increased with solar radiation, air, and soil temperatures, but decreased with increasing humidity. Most species exhibited negative thermal decoupling (TD), remaining 6.7K cooler than the air, with variations across species, time of day, and growth form - shorter, rounded plants showed stronger negative TD. Notably, despite negative TD, all species exhibited high heat resistance (Mean LT50 = 46°C), with LT50 positively correlated with TD, but only in shrubs. These findings highlight the intricate relationships among thermal decoupling, environmental factors, and plant traits in shaping heat resistance. This study provides insights into how alpine plants may respond to the increasing heat stress associated with climate change, emphasizing the adaptive significance of thermal decoupling in these environments.