Several studies have recently documented the effects of elevated CO2 on photosynthesis in various varieties of spruce.  In the relatively short-term study of Tjoelker et al. (1998a), black spruce seedlings grown for three months at atmospheric CO2 concentrations of 580 ppm exhibited photosynthetic rates that were about 28% greater than those displayed by control seedlings fumigated with air containing 370 ppm CO2.  Similarly, Egli et al. (1998) reported that Norway spruce seedlings grown at 570 ppm CO2 displayed photosynthetic rates that were 35% greater than those exhibited by seedlings grown at 370 ppm.  In two branch bag studies conducted on mature trees, it was demonstrated that twice-ambient levels of atmospheric CO2 enhanced rates of photosynthesis in current-year needles by 50% in Norway spruce (Roberntz and Stockfors, 1998) and 100% in Sitka spruce (Barton and Jarvis, 1999).  Finally, in the four-year open-top chamber study of Murray et al. (2000), the authors reported that Sitka spruce seedlings growing at 700 ppm CO2 exhibited photosynthetic rates that were 19 and 33% greater than those observed in control trees growing in ambient air and receiving low and high amounts of nitrogen fertilization, respectively.

Because elevated CO2 enhances photosynthetic rates in spruce species, this phenomenon should lead to increased biomass production in these important coniferous trees; and so it does.  In the short-term three-month study of Tjoelker et al. (1998b), for example, black spruce seedlings receiving an extra 210 ppm CO2 displayed final dry weights that were about 20% greater than those of seedlings growing at ambient CO2.  Similarly, after growing Sitka spruce for three years in open-top chambers, Centritto et al. (1999) reported that a doubling of the atmospheric CO2 concentration enhanced sapling dry mass by 42%.

In summary, it is clear that as the CO2 content of the air increases, spruce trees will likely display enhanced rates of photosynthesis and biomass production, regardless of soil nutrient status.  Consequently, rates of carbon sequestration by this abundant coniferous forest species will likely be enhanced.

For more information on spruce growth responses to atmospheric CO2 enrichment see Plant Growth Data: Norway Spruce (photosynthesis), and Sitka Spruce (dry weight, photosynthesis).

References
Barton, C.V.M. and Jarvis, P.G.  1999.  Growth response of branches of Picea sitchensis to four years exposure to elevated atmospheric carbon dioxide concentration.  New Phytologist 144: 233-243.

Centritto, M., Lee, H.S.J. and Jarvis, P.G.  1999.  Long-term effects of elevated carbon dioxide concentration and provenance on four clones of Sitka spruce (Picea sitchensis).  I. Plant growth, allocation and ontogeny.  Tree Physiology 19: 799-806.

Egli, P., Maurer, S., Gunthardt-Goerg, M.S. and Korner, C.  1998.  Effects of elevated CO2 and soil quality on leaf gas exchange and aboveground growth in beech-spruce model ecosystems.  New Phytologist 140: 185-196.

Murray, M.B., Smith, R.I., Friend, A. and Jarvis, P.G.  2000.  Effect of elevated [CO2] and varying nutrient application rates on physiology and biomass accumulation of Sitka spruce (Picea sitchensis).  Tree Physiology 20: 421-434.

Roberntz, P. and Stockfors, J.  1998.  Effects of elevated CO2 concentration and nutrition on net photosynthesis, stomatal conductance and needle respiration of field-grown Norway spruce trees.  Tree Physiology 18: 233-241.

Tjoelker, M.G., Oleksyn, J. and Reich, P.B.  1998a.  Seedlings of five boreal tree species differ in acclimation of net photosynthesis to elevated CO2 and temperature.  Tree Physiology 18: 715-726.

Tjoelker, M.G., Oleksyn, J. and Reich, P.B.  1998b.  Temperature and ontogeny mediate growth response to elevated CO2 in seedlings of five boreal tree species.  New Phytologist 140: 197-210.