Leaf Temperatures and Physiological Vulnerability of a Tropical Forest in Western Ghats

Abstract

Global surface temperatures are increasing, and extreme weather events like heat waves are becoming more frequent and intense, posing a threat to the functioning and dynamics of tropical forests around the world. The study reports long-term, high-resolution leaf temperatures data to discuss the exceedences and continuous exposure times above physiological thermal thresholds, and further expands to evaluate potential heat-induced damages post a hot and dry period and understand the overall vulnerability of a tropical forest in Western Ghats. The leaves are consistently approaching and exceeding CO2 assimilation thresholds spending considerable amounts of time under non-optimal temperatures. Average continuous times of exposure above T50 - temperature at which Photosystem II quantum yield reduces to 50% - are not yet suggestive of prevalence of irreversible damages. Estimates of thermal safety margins for 55 species using the leaf energy budget model were able to identify species that are likely to be vulnerable under current and future climate conditions. The results suggest that there is large variation in how vulnerable physiological function is to extreme temperautres, some species may be particularly sensitive to heat induced damages in future climates with increased global temperatures.