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Effects of rising temperatures and (CO2) on the physiology of tropical forest trees

Effects of rising temperatures and (CO2) on the physiology of tropical forest trees,Jon Lloyd,Graham D. Farquhar

Effects of rising temperatures and (CO2) on the physiology of tropical forest trees   (Citations: 21)
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Using a mixture of observations and climate model outputs and a simple parametrization of leaf-level photosynthesis incorporating known temperature sensitivities, we find no evidence for tropical forests currently existing 'dangerously close' to their optimum temperature range. Our model suggests that although reductions in photosynthetic rate at leaf temperatures (TL )a bove 308C may occur, these are almost entirely accountable for in terms of reductions in stomatal conductance in response to higher leaf- to-air vapour pressure deficitsD. This is as opposed to direct effects ofTL on photosynthetic metabolism. We also find that increases in photosynthetic rates associated with increases in ambient (CO2 )o ver forthcoming decades should more than offset any decline in photosynthetic productivity due to higherD or TL or increased autotrophic respiration rates as a consequence of higher tissue temperatures. We also find little direct evidence that tropical forests should not be able to respond to increases in (CO2 )a nd argue that the magnitude and pattern of increases in forest dynamics across Amazonia observed over the last few decades are consistent with a (CO2)-induced stimulation of tree growth.
Published in 2008.
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    • ...Although one cannot rule out some influence of sampling biases in the results, these results are consistent with the expected response to increased atmospheric CO2 (Lloyd and Farquhar 2008) and with the finding in temperate regions that small trees showed stronger growth increases over time than larger trees (Voelker et al. 2006; Wang et al. 2006)...

    Danaë M. A. Rozendaalet al. Dendroecology in the tropics: a review

    • ...Studies on carbon isotope ratios over longer time scales in tropical trees are particularly important as the degree to which tropical forests have responded to increasing [CO2] and acted as carbon sinks over the last century is still a topic of heated scientific debate (Ko ¨rner 2003; Lewis et al. 2009; Lloyd and Farquhar 2008)...
    • ...Decadal scale inventory studies show an increase in biomass of tropical forests, thought to be due to CO2 fertilisation (Lewis et al. 2009; Lloyd and Farquhar 2008)...
    • ...Temperature increases may indirectly result in higher Wi as higher temperatures increase vapour pressure deficits (vpd), to which plants may respond by closing their stomata (reducing gs) (Lloyd and Farquhar 2008)...
    • ...However, temperature and irradiance may also indirectly influence stomatal behaviour, and thereby the carbon isotope signal, through their effects on the water vapour pressure deficit across stomata (Lloyd and Farquhar 2008; Seibt et al. 2008)...

    Roel J. W. BrienenWolfganget al. Stable carbon isotopes in tree rings indicate improved water use effic...

    • ...Our hypothesis was based on the assumption that RRD is closely associated with plant activity (Lloyd and Farquhar 2008 )w hileROM is associated both with the recalcitrance of soil organic matter and nutrient availability in soils...
    • ...The fact that the percentage of A subsequently respired via RRD (RRD/A ,T able3) was significantly lower for the paspalum in the HF soil compared to the ryegrass in the LF soil contradicts previous reports which showed that the percentage of assimilated C lost as RRD was relatively higher in tropical plants when compared to temperate plants (Lloyd and Farquhar 1996; Lloyd and Farquhar 2008)...

    Yoshitaka Uchidaet al. Soil properties and presence of plants affect the temperature sensitiv...

    • ... In addition, warmer climates may also cause a deceleration in tree growth by increasing rates of respiration. However, since growth is not limited by carbon and acclimation of respiration is likely occurring, respiration cannot explain growth declines ...

    Lucas C. R. Silvaet al. Recent Widespread Tree Growth Decline Despite Increasing Atmospheric C...

    • ...Our simulated increase in productivity and widening of foliar C:N ratios in response to elevated [CO2] have been observed in tropical rain forests [Lloyd and Farquhar, 2008], suggesting that elevated [CO2] may affect plant growth, although the evidence is inconclusive...

    Sönke Zaehleet al. Terrestrial nitrogen feedbacks may accelerate future climate change

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