Interacting effects of elevated CO2 and weather variability on photosynthesis of mature boreal Norway spruce agree with biochemical model predictions

• According to well-known biochemical and biophysical mechanisms, the stimulation of C3 photosynthesis by elevated atmospheric CO2 concentration ([CO2]) is strongly modified by changes in temperature and radiation. In order to investigate if a static parameterisation of the commonly used Farquhar et al. model of photosynthesis (i.e. without CO2-induced seasonal or thermal acclimation of photosynthetic capacity) can accurately predict these interactions in mature boreal Norway spruce (Picea abies (L.) Karst.) during the frost-free part of the growing season, shoot gas exchange was continuously measured on trees during their second/third year of exposure to ambient or doubled [CO2] inside whole-tree chambers. The relative CO2-induced enhancement of net photosynthesis (An) at a given temperature remained stable over the study period, but increased strongly with temperature and radiation, in agreement with predictions by the model. Light-saturated An (+67% at 20 C), dark respiration (+36%) and intercellular to ambient [CO2] ratio (ci/ca; +27%) were significantly increased by CO2 treatment. Stomatal conductance (gs) was not significantly affected. Our results demonstrate that the Farquhar et al. model of photosynthesis has the capability to predict interactions between [CO2] and seasonal weather variability on An in Norway spruce during the non-frost growing season without accounting for CO2-induced seasonal and/or thermal photosynthetic acclimation. However, stomatal model assumptions of reduced gs and constant ci/ca under rising atmospheric [CO2] did not hold.

Ämnesord

NATURVETENSKAP  -- Biologi -- Ekologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Ecology (hsv//eng)

NATURVETENSKAP  -- Biologi -- Botanik (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Botany (hsv//eng)

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Annan geovetenskap och miljövetenskap (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Other Earth and Related Environmental Sciences (hsv//eng)

Nyckelord

carbon dioxide

photosynthesis

Picea abies

respiration

stomatal conductance

whole-tree chambers

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)