Contrasting acclimation abilities of two dominant boreal conifers to elevated CO2 and temperature
Plant Cell Environ. 2018 Feb 7[Epub ahead of print]
Kurepin LV, Stangl ZR, Ivanov AG, Bui V, Mema M, Hüner NPA, Öquist G, Way D, Hurry V

Abstract
High latitude forests will experience large changes in temperature and CO2 concentrations this century. We evaluated the effects of future climate conditions on two dominant boreal tree species, Pinus sylvestris L. and Picea abies (L.) H. Karst, exposing seedlings to three seasons of ambient (430 ppm) or elevated CO2 (750 ppm) and ambient temperatures, a +4 °C warming, or a +8 °C warming. Pinus sylvestris responded positively to warming: seedlings developed a larger canopy, maintained high net CO2 assimilation rates (Anet ) and acclimated dark respiration (Rdark ). In contrast, carbon fluxes in Picea abies were negatively impacted by warming: maximum rates of Anet decreased, electron transport was redirected to alternative electron acceptors, and thermal acclimation of Rdark was weak. Elevated CO2 tended to exacerbate these effects in warm-grown Picea abies, and by the end of the experiment Picea abies from the +8 °C, high CO2 treatment produced fewer buds than they had three years earlier. Treatments had little effect on leaf and wood anatomy. Our results highlight that species within the same plant functional type may show opposite responses to warming, and imply that Picea abies may be particularly vulnerable to warming due to low plasticity in photosynthetic and respiratory metabolism.

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