Photosynthesis is a complex process for capturing carbon from the atmosphere. Multiple steps in this process can control the maximum rate of carbon capture. We use a combination of manipulative experiments and field observations to understand the rate-limiting steps for photosynthesis in different tropical tree species. We also study how environmental conditions and plant ontogeny might influence which step is rate-limiting.

Species may differ in their heat tolerance but they also differ in the extent to which they experience heat, based on their architecture, morphology, and physiology. New technologies enable us to monitor temperatures of leaves in the canopy at a larger scale than traditional methods that involved attaching thermocouple wires to leaves. Monitoring canopy temperatures in diverse forest plots allows us to identify the species that experience the highest temperature extremes. We study these species in more detail to evaluate their physiological capacity to withstand high temperatures, and analyze the relative importance of architecture, morphology, and physiology as predictors of “overheating” of plants.

Little is known about high-temperature thresholds for reproduction in wild plants, but studies on crops suggest that reproduction may fail at 30–39°C. If thresholds for reproduction are universal, tropical species are close to exceeding them, as temperatures there already routinely exceed 30°C. As temperatures continue to rise, seed production may drastically change in tropical forests, with consequences for species composition and community dynamics. Through experiments and field observations, we are studying tropical tree species’ vulnerability to heat-induced sterility, with the ultimate goal of understanding how rising temperatures may change forest community composition.