Abiotic Stress/Whole Plant Bio

CS-14-5 - Thermal acclimation of photosynthesis and respiration differ across mature conifer species in a boreal forest peatland

Monday, July 16
2:23 PM - 2:43 PM

Boreal forests are often assumed to be temperature-limited, and warming is therefore expected to stimulate their carbon uptake. However, much of our information on the ability of boreal conifers to acclimate photosynthesis and respiration to rising temperatures comes from seedlings. We measured net CO2 assimilation rates (A) and dark respiration (R) at 25 °C (A25 and R25) and at prevailing growth temperatures (Ag and Rg) in mature Picea mariana (spruce) and Larix laricina (tamarack) exposed to ambient, +2.25, +4.5, +6.75 and +9 °C warming treatments in open top chambers in the field at the SPRUCE experiment (MN, USA).


In spruce, A25 and Ag were similar across plots in May and June. In August, spruce in warmer treatments had higher A25, an effect that was offset by warmer leaf temperatures in the Ag data.


 


In tamarack, A25 was stimulated by warming in both June and August, an effect that was mainly offset by higher leaf temperatures when Ag was assessed in June, while in August, Ag was still slightly higher in the warmest treatments (+6.75 and +9) compared to the ambient plots.


 


In spruce, R25 was enhanced in warm-grown trees in May, but was similar across treatments in June and August, indicating little acclimation of R. Rg slightly increased with warming treatments across the season in spruce. In contrast, R in tamarack thermally acclimated, as R25 decreased with warming. But while this acclimation generated homeostatic Rg in June, Rg in August was still highest in the warmest treatments. Our work suggests that the capacity for thermal acclimation in both photosynthesis and respiration varies among boreal tree species, which may lead to shifts in the performance of these species as the climate warms.


 

Co-Authors

Joseph R. Stinziano – The University of Western Ontario; Jeffrey M. Warren – ORNL; Eric J. Ward – ORNL; Stan D. Wullschleger – ORNL; Paul J. Hanson – ORNL; Danielle A. Way – The University of Western Ontario

Mirindi Eric Dusenge

PhD Candidate
The University of Western Ontario

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CS-14-5 - Thermal acclimation of photosynthesis and respiration differ across mature conifer species in a boreal forest peatland



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