The research described in this article has been funded by the US Environmental Protection Agency. This document has been prepared at the EPA’s Western Ecology Division in Corvallis, Oregon, through cooperative agreement CR-824072 with the National Research Council and through contract 68-C6- 0005 with Dynamac, Inc. It has been subject to the agency’s peer and administrative review. It has been approved for publication as an EPA document.
Atmospheric carbon dioxide -- Physiological effect, Douglas fir -- Growth, Photosynthesis, Acclimatization (Plants)
- Here we examined correlations between needle nitrogen concentration ([N]) and photosynthetic responses of Douglas-fir (Pseudotsuga menziesii) seedlings to growth in elevated temperatures and atmospheric carbon dioxide concentrations ([CO2]).
- Seedlings were grown in sunlit, climate-controlled chambers at ambient or ambient+3.5° C and ambient or ambient +180 μmol mol-1 CO2 in a full factorial design. Photosynthetic parameters and needle [N] were measured six times over a 21-month period.
- Needle [N] varied seasonally, and accounted for 30–50% of the variation in photosynthetic parameters. Across measurement periods, elevated temperature increased needle [N] by 26% and light-saturated net photosynthetic rates by 17%. Elevated [CO2] decreased needle [N] by 12%, and reduced net photosynthetic rates measured at a common [CO2], maximum carboxylation activity (Vc,max) and electrontransport capacity (Jmax), indicating photosynthetic acclimatization. Even so, elevated [CO2] enhanced net photosynthesis, and this effect increased with needle [N].
- These results suggest that needle [N] may regulate photosynthetic responses of Douglas-fir to climate change. Further, needle [N] may be altered by climate change. However, effects of elevated [CO2] on photosynthesis may be similar across growth temperatures.
Lewis, J. D., Lucash, M. M., Olszyk, D. M., & Tingey, D. T. (2004). Relationships between needle nitrogen concentration and photosynthetic responses of Douglas-fir seedlings to elevated CO2 and temperature. New Phytologist, 162(2), 355-364.