The effect of induced heat waves on Pinus taeda and Quercus rubra seedlings in ambient and elevated CO2 atmospheres.
Here, we investigated the effect of different heat-wave intensities applied at two atmospheric CO2 concentrations ([CO2]) on seedlings of two tree species, loblolly pine (Pinus taeda) and northern red oak (Quercus rubra). Seedlings were assigned to treatment combinations of two levels of [CO2] (380 or 700 μmol mol(-1)) and four levels of air temperature (ambient, ambient +3°C, or 7-d heat waves consisting of a biweekly +6°C heat wave, or a monthly +12°C heat wave). Treatments were maintained throughout the growing season, thus receiving equal heat sums. We measured gas exchange and fluorescence parameters before, during and after a mid-summer heat wave. The +12°C heat wave, significantly reduced net photosynthesis (Anet) in both species and [CO2] treatments but this effect was diminished in elevated [CO2]. The decrease in Anet was accompanied by a decrease in Fv'/Fm' in P. taeda and ΦPSII in Q. rubra. Our findings suggest that, if soil moisture is adequate, trees will experience negative effects in photosynthetic performance only with the occurrence of extreme heat waves. As elevated [CO2] diminished these negative effects, the future climate may not be as detrimental to plant communities as previously assumed.
Laboratory of Plant Ecology, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, B-9000, Ghent, Belgium.
Maarten
M
Ameye
Daniel B. Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA, 30602, USA.
Timothy M
TM
Wertin
Laboratory of Plant Ecology, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, B-9000, Ghent, Belgium.
Ingvar
I
Bauweraerts
Daniel B. Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA, 30602, USA.
Mary Anne
MA
McGuire
Daniel B. Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA, 30602, USA.
Robert O
RO
Teskey
Laboratory of Plant Ecology, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, B-9000, Ghent, Belgium.
Kathy
K
Steppe
D001272:Atmosphere / Q000737:chemistry*; D002245:Carbon Dioxide / Q000494:pharmacology*; D005453:Fluorescence; D006358:Hot Temperature; D016014:Linear Models; D015999:Multivariate Analysis; D010788:Photosynthesis / Q000187:drug effects; D045332:Photosystem II Protein Complex / Q000378:metabolism; D041603:Pinus taeda / Q000187:drug effects / Q000502:physiology*; D054046:Plant Stomata / Q000187:drug effects / Q000502:physiology; D018526:Plant Transpiration / Q000187:drug effects / Q000502:physiology; D029963:Quercus / Q000187:drug effects / Q000502:physiology*; D036226:Seedlings / Q000187:drug effects / Q000254:growth & development / Q000502:physiology*
D045332:Photosystem II Protein Complex; D002245:Carbon Dioxide