The Effects of Rising Temperature on the Ecophysiology of Tropical Forest Trees

Abstract

The response of tropical trees to rising temperatures represents a key uncertainty that limits our ability to predict biosphere-atmosphere feedbacks in a warming world. We review the current understanding of temperature effects on the ecophysiology of tropical trees from organelle to biome level, where we distinguish between short-term responses, acclimation, and adaptation. We present new data on short-term temperature responses of photosynthesis and dark respiration, and temperature acclimation of photosynthesis. We also compare new field and laboratory-obtained photosynthesis-temperature response data. We identify several priority study areas. (1) Acclimation: We need to better understand photosynthetic acclimation, for example to determine whether the adjustment of the thermal optimum of photosynthesis (TOpt) is consistently negated by a decrease in photo- synthesis at TOpt, as we observed. (2) Growth: Whereas tropical seedlings may grow better with warming, canopy trees reportedly grow worse; we do not currently know what explains these contrasting temperature effects. (3) Reproduction: Tropical trees may be close to reproductive temperature thresholds, as heat sterility in crops occurs in the upper 30 °C range. Nonetheless, the temperature sensitivity of tropical tree reproduction is virtually unstudied. (4) Mortality: How does heat-induced atmospheric drought (high leaf-to-air vapor pressure deficit) affect tropical tree mortality? (5) Stomatal behavior: What is the specific role of tem- perature in the induction of midday-stomtal closure on sunny days? Better knowledge in these areas will improve our ability to predict carbon fluxes in tropical forests experiencing ongoing warming.