EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Roles of photosynthetic, respiratory, stomatal and phenological acclimation in controlling carbon and water fluxes of mature Norway spruce in a changing climate  

Shubhangi Lamba1, Remko A. Duursma2, Thomas B. Hasper1, Bjarni D. Sigurdsson3, Belinda E. Medlyn2, Lasse Tarvainen1, Marianne Hall4, Sune Linder5, Göran Wallin1, and Johan Uddling1
Shubhangi Lamba et al.
  • 1Department of Biological and Environmental Sciences, University of Gothenburg, P.O. Box 461, SE-405 30 Göteborg, Sweden
  • 2Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith NSW 2751, Australia
  • 3Agricultural University of Iceland, Keldnaholt, IS-112 Reykjavik, Iceland
  • 4Centre for Environmental and Climate Research, Lund University, Sölvegatan 37, SE-22362 Lund, Sweden
  • 5Southern Swedish Forest Research Centre, Swedish University of Agricultural Sciences, P.O. Box 49, SE-230 53, Alnarp, Sweden

Boreal regions are undergoing rapid climate change but our understanding of the long-term consequences for forest processes is hampered by limited knowledge of how trees acclimate to rising atmospheric CO2 concentrations and temperature. This study used the detailed canopy flux model MAESTRA to simulate the effects of elevated CO2 (eCO2) and warming on net photosynthesis (An) and transpiration (E) of mature boreal Norway spruce, investigating how these effects are influenced by the observed acclimation of photosynthetic capacity, respiration, stomatal behavior, and phenology. Without any type of acclimation, eCO2 increased shoot and crown An during the non-frost growing season by 23-44%, while warming only had a minor effect (±2%). Photosynthetic downregulation greatly decreased the positive effect under eCO2. Under warming, both stomatal and phenological acclimation had substantial effects on An but in opposite directions. Transpiration at shoot and crown level was greatly decreased (23-50%) by eCO2 and increased by warming (27-42%) in the absence of acclimation. However, both these effects were largely cancelled by stomatal acclimation. Effects of eCO2 on An were generally smaller at entire crown compared to shoot level, as a result of photosynthetic stimulation being smaller in shaded canopy positions. In addition, upregulation of respiration in eCO2 had a considerably larger negative effect on An at crown compared to shoot level. Overall, tree physiological acclimation generally acted to dampen non-acclimated responses. We conclude that photosynthetic and respiratory acclimation greatly reduce the positive effect of eCO2 on tree CO2 assimilation, while stomatal and phenological acclimation are crucial for annual water consumption under warming. These results highlight the critical need to account for acclimation in models.


How to cite: Lamba, S., Duursma, R. A., Hasper, T. B., Sigurdsson, B. D., Medlyn, B. E., Tarvainen, L., Hall, M., Linder, S., Wallin, G., and Uddling, J.: Roles of photosynthetic, respiratory, stomatal and phenological acclimation in controlling carbon and water fluxes of mature Norway spruce in a changing climate  , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15118,, 2021.