Variation in leaf temperatures of tropical and subtropical trees are related to leaf thermoregulatory traits and not geographic distributions

Abstract To help predict the effects of global warming on plants, previous studies have investigated how the distributions and physiological performances of plants relate to environmental temperatures. This approach implicitly assumes that leaf temperatures are tightly linked to regional air temperatures. However, the thermoregulatory behaviors and physical properties of leaves can differ greatly between species, leading to different plants having different leaf temperatures even when they occur under similar conditions. It is important to understand this variation in leaf thermoregulatory traits and temperatures in order to predict how individual species will be impacted by global warming. We measured the thermal properties of leaves from >50 tropical and subtropical tree species grown at the Gifford Arboretum (Florida, USA). For each species, we measured maximum leaf temperature and rate of leaf warming using a new standardized protocol to control for both environmental variation and select plant thermoregulatory behaviors. We tested the relationships between the two thermal variables and several leaf functional traits. Even under laboratory‐controlled conditions, leaf temperatures varied by over 8.5°C among species. Maximum leaf temperature was positively correlated with leaf area, and rate of leaf warming was negatively correlated with water content per leaf area. This suggests that some species may be able to offset rising air temperatures through acclimation or adaptation of these leaf properties. Next, we tested the relationships between the species’ leaf thermal properties and their climatic niches/distributions, but we found no significant associations. These results call into question the use of regional air temperatures to model plant physiological and demographic performance. Abstract in Spanish is available with online material.