Browsing by Author "Malhi, Yadvinder"
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- Impacts of experimentally imposed drought on leaf respiration and morphology in an Amazon rain forestPublication . Metcalfe, Daniel B.; Lobo-do-Vale, Raquel; Chaves, Maria Manuela; Maroco, João; Aragão, Luiz E. O. C.; Malhi, Yadvinder; Costa, António L. da; Braga, Alan P.; Gonçalves, Paulo L.; Athaydes, João de; Costa, Mauricio da; Almeida, Samuel S.; Campbell, Catherine; Hurry, Vaughan; Williams, Mathew; Meir, Patrick1. 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.
- Shifts in plant respiration and carbon use efficiency at a large-scale drought experiment in the eastern AmazonPublication . Metcalfe, Daniel B.; Meir, Patrick; Aragão, Luiz E. O. C.; Lobo-do-Vale, Raquel; Galbraith, David; Fisher, Rosie; Chaves, Maria Manuela; Maroco, João; Costa, António L. da; Almeida, Samuel S.; Braga, Alan P.; Gonçalves, Paulo L.; Athaydes, João de; Costa, Mauricio da; Portela, T. T. B.; Oliveira, A. A. R. de; Malhi, Yadvinder; Williams, MathewThe effects of drought on the Amazon rainforest are potentially large but remain poorly understood. Here, carbon (C) cycling after 5 yr of a large-scale through-fall exclusion (TFE) experiment excluding about 50% of incident rainfall from an eastern Amazon rainforest was compared with a nearby control plot. • Principal C stocks and fluxes were intensively measured in 2005. Additional minor components were either quantified in later site measurements or derived from the available literature. • Total ecosystem respiration (Reco) and total plant C expenditure (PCE, the sum of net primary productivity (NPP) and autotrophic respiration (Rauto)), were elevated on the TFE plot relative to the control. The increase in PCE and Reco was mainly caused by a rise in Rauto from foliage and roots. Heterotrophic respiration did not differ substantially between plots. NPP was 2.4 ± 1.4 t C ha)1 yr)1 lower on the TFE than the control. Ecosystem carbon use efficiency, the proportion of PCE invested in NPP, was lower in the TFE plot (0.24 ± 0.04) than in the control (0.32 ± 0.04). • Drought caused by the TFE treatment appeared to drive fundamental shifts in ecosystem C cycling with potentially important consequences for long-term forest C storage.