Metcalfe, Daniel B.Lobo-do-Vale, RaquelChaves, Maria ManuelaMaroco, JoãoAragão, Luiz E. O. C.Malhi, YadvinderCosta, António L. daBraga, Alan P.Gonçalves, Paulo L.Athaydes, João deCosta, Mauricio daAlmeida, Samuel S.Campbell, CatherineHurry, VaughanWilliams, MathewMeir, Patrick2012-09-202012-09-202010Functional Ecology, 24, 524-5330269-8463http://hdl.handle.net/10400.12/17101. The Amazon region may experience increasing moisture limitation over this century. Leaf dark respiration (R) is a key component of the Amazon rain forest carbon (C) cycle, but relatively little is known about its sensitivity to drought. 2. Here, we present measurements of R standardized to 25 C and leaf morphology from different canopy heights over 5 years at a rain forest subject to a large-scale through-fall reduction (TFR) experiment, and nearby, unmodified Control forest, at the Caxiuana˜ reserve in the eastern Amazon. 3. In all five post-treatment measurement campaigns, mean R at 25 C was elevated in the TFR forest compared to the Control forest experiencing normal rainfall. After 5 years of the TFR treatment, R per unit leaf area and mass had increased by 65% and 42%, respectively, relative to pre-treatment means. In contrast, leaf area index (L) in the TFR forest was consistently lower than the Control, falling by 23% compared to the pre-treatment mean, largely because of a decline in specific leaf area (S). 4. The consistent and significant effects of the TFR treatment on R, L and S suggest that severe drought events in the Amazon, of the kind that may occur more frequently in future, could cause a substantial increase in canopy carbon dioxide emissions from this ecosystem to the atmosphere.engTropical forestClimate changeMoisture deficitLeaf dark respirationNight-time foliar carbon emissionsSpecific leaf areaLeaf area indexThrough-fall exclusion experimentjournal article