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Ecological Society of America (ESA) abstract for 2002 |
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No evidence for photosynthetic downregulation in 11 tree species in the forest understory to Free Air Carbon-dioxide Enrichment (FACE) |
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Moore, D.J., Mohan, J. and DeLucia, E.H. |
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The photosynthetic response to long-term elevated CO2 exposure is often different from the instantaneous response. In a blocked experimental design consisting of 6 FACE rings, 11 species of deciduous trees in the understory of an unmanaged pine plantation were exposed to ambient and elevated CO2 levels (+200 p.p.m., similar to those predicted for year 2050) for > 2 years. We tested whether down-regulation of photosynthesis occurred in seedlings of a range of species of similar age, and whether species responded differently to elevated [CO2]. Steady state photosynthesis was higher in elevated CO2 in all species (p<0.0001). Expected treatment by species interactions were absent (p=0.3603). There was no evidence of photosynthetic down-regulation, and on average the photosynthetic rate at ambient CO2 was indicative of the rate at elevated CO2 (R2= 0.764). The lack of differential species responses to elevated CO2 simplifies predictions of future forest photosynthetic responses. However, the percentage stimulation of photosynthesis was greater for species with low than high photosynthetic rates under ambient conditions, suggesting that carbon gain and persistence in the understory may be disproportionately enhanced under future elevated levels of CO2 for species with low rates of photosynthesis. |
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ESA 2003 abstract |
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