Impacts of experimentally imposed drought on leaf respiration and morphology in an Amazon rain forest
2010
Metcalfe, Daniel B. | Lobo‐do‐Vale, Raquel | Chaves, Manuela M. | Maroco, Joao P. | C Aragão, Luiz E. O. | Malhi, Y. (Yadvinder) | Da Costa, Antonio L. | Braga, Alan P. | Gonçalves, Paulo L. | De Athaydes, Joao | Da Costa, Mauricio | Almeida, Samuel S. | Campbell, Catherine | Hurry, Vaughan | Williams, Mathew | Meir, Patrick
1. 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 Caxiuanã 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.
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