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Title: Causes of reduced leaf-level photosynthesis during strong El Niño drought in a Central Amazon forest
Authors: Santos, Victor Alexandre Hardt Ferreira dos
Ferreira, Marciel José
Rodrigues, J. V. F. C.
Garcia, Maquelle Neves
Ceron, João Vitor Barbosa
Nelson, Bruce Walker
Saleska, Scott Reid
Keywords: Chlorophyll
Climate Change
Drought Stress
El Nino
Extreme Event
Stomatal Conductance
Tropical Forest
El Nino
Plant Leaf
El Nino-southern Oscillation
Plant Leaves
Issue Date: 2018
metadata.dc.publisher.journal: Global Change Biology
metadata.dc.relation.ispartof: Volume 24, Número 9, Pags. 4266-4279
Abstract: Sustained drought and concomitant high temperature may reduce photosynthesis and cause tree mortality. Possible causes of reduced photosynthesis include stomatal closure and biochemical inhibition, but their relative roles are unknown in Amazon trees during strong drought events. We assessed the effects of the recent (2015) strong El Niño drought on leaf-level photosynthesis of Central Amazon trees via these two mechanisms. Through four seasons of 2015, we measured leaf gas exchange, chlorophyll a fluorescence parameters, chlorophyll concentration, and nutrient content in leaves of 57 upper canopy and understory trees of a lowland terra firme forest on well-drained infertile oxisol. Photosynthesis decreased 28% in the upper canopy and 17% in understory trees during the extreme dry season of 2015, relative to other 2015 seasons and was also lower than the climatically normal dry season of the following non-El Niño year. Photosynthesis reduction under extreme drought and high temperature in the 2015 dry season was related only to stomatal closure in both upper canopy and understory trees, and not to chlorophyll a fluorescence parameters, chlorophyll, or leaf nutrient concentration. The distinction is important because stomatal closure is a transient regulatory response that can reverse when water becomes available, whereas the other responses reflect more permanent changes or damage to the photosynthetic apparatus. Photosynthesis decrease due to stomatal closure during the 2015 extreme dry season was followed 2 months later by an increase in photosynthesis as rains returned, indicating a margin of resilience to one-off extreme climatic events in Amazonian forests. © 2018 John Wiley & Sons Ltd
metadata.dc.identifier.doi: 10.1111/gcb.14293
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