Long‐term drought effects on the thermal sensitivity of Amazon forest trees

• Published in: Plant, cell and environment Vol. 46; no. 1; pp. 185 - 198
• Main Authors: Docherty, Emma M., Gloor, Emanuel, Sponchiado, Daniela, Gilpin, Martin, Pinto, Carlos A. D., Junior, Haroldo M., Coughlin, Ingrid, Ferreira, Leandro, Junior, João A. S., Costa, Antonio C. L., Meir, Patrick, Galbraith, David
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 01.01.2023; John Wiley and Sons Inc
• Subjects: Air temperature; Amazon rainforest; chlorophyll a fluorescence; Climate change; Climate models; Damage tolerance; Drought; drought and heat stress interactions; Forests; Original; Photosynthesis; Photosystem II; Photosystem II Protein Complex; Plant species; Quantum efficiency; Respiration; thermal traits; thermotolerance; throughfall exclusion; Trees; tropical evergreen trees; Tropical forests; chlorophyll a fluorescence; drought and heat stress interactions; thermotolerance; Amazon rainforest; photosynthesis; throughfall exclusion; tropical evergreen trees; thermal traits; respiration
• ISSN: 0140-7791; 1365-3040
• DOI: 10.1111/pce.14465

The continued functioning of tropical forests under climate change depends on their resilience to drought and heat. However, there is little understanding of how tropical forests will respond to combinations of these stresses, and no field studies to date have explicitly evaluated whether sustained drought alters sensitivity to temperature. We measured the temperature response of net photosynthesis, foliar respiration and the maximum quantum efficiency of photosystem II (Fv/Fm) of eight hyper‐dominant Amazonian tree species at the world's longest‐running tropical forest drought experiment, to investigate the effect of drought on forest thermal sensitivity. Despite a 0.6°C–2°C increase in canopy air temperatures following long‐term drought, no change in overall thermal sensitivity of net photosynthesis or respiration was observed. However, photosystem II tolerance to extreme‐heat damage (T50) was reduced from 50.0 ± 0.3°C to 48.5 ± 0.3°C under drought. Our results suggest that long‐term reductions in precipitation, as projected across much of Amazonia by climate models, are unlikely to greatly alter the response of tropical forests to rising mean temperatures but may increase the risk of leaf thermal damage during heatwaves.