How does rising atmospheric CO2 affect marine organisms?

Click to locate material archived on our website by topic

Growth Response to CO2 With Other Variables -- Nitrogen (Trees: Other) -- Summary
In exploring the effects of soil nitrogen concentration on the ability of atmospheric CO2 enrichment to stimulate the growth and development of earth's trees, we have previously reviewed and summarized the results of multiple studies that have been conducted on aspen, pine and spruce [see Nutrients x CO2 Effects on Plants (Nitrogen - Trees: Aspen, Pine and Spruce) in our Subject Index].  Here, we review what has been learned about some other trees in this regard.

Maillard et al. (2001) grew pedunculate oak seedlings for three to four months in greenhouses maintained at atmospheric CO2 concentrations of either 350 or 700 ppm under conditions of either low or high soil nitrogen concentration.  The elevated CO2 of their study stimulated belowground growth in the seedlings growing in the nitrogen-poor soil, significantly increasing their root-to-shoot ratios.  However, it increased both the below- and above-ground biomass of seedlings growing in nitrogen-rich soil.  In fact, the CO2-enriched seedlings growing in the nitrogen-rich soil produced 217 and 533% more stem and coarse-root biomass, respectively, than their ambient-air counterparts growing in the same fertility treatment.  Overall, the doubled CO2 concentration of the air in their study enhanced total seedling biomass by approximately 30 and 140% under nitrogen-poor and nitrogen-rich soil conditions, respectively.

Schortemeyer et al. (1999) grew seedlings of Acacia melanoxylon (a leguminous nitrogen-fixing tree native to south-eastern Australia) in hydroponic culture for six weeks in growth cabinets, where the air was maintained at CO2 concentrations of either 350 or 700 ppm and the seedlings were supplied with water containing nitrogen in a number of discrete concentrations ranging from 3 to 6,400 mmol m-3.  In the two lowest of these nitrogen concentration treatments, final biomass was unaffected by atmospheric CO2 enrichment; but, as in the study of Maillard et al., it was increased by 5- to 10-fold at the highest nitrogen concentration.

Temperton et al. (2003) measured total biomass production in another N2-fixing tree - Alnus glutinosa (the common alder) - seedlings of which had been grown for three years in open-top chambers in either ambient or elevated (ambient + 350 ppm) concentrations of atmospheric CO2 and one of two soil nitrogen regimes (full nutrient solution or no fertilizer).  In their study, by contrast, they found that the trees growing under low soil nutrient conditions exhibited essentially the same growth enhancement as that of the well-fertilized trees.

Rounding out the full gamut of growth responses, Gleadow et al. (1998) grew eucalyptus seedlings for six months in glasshouses maintained at atmospheric CO2 concentrations of either 400 or 800 ppm, fertilizing them twice daily with low or high nitrogen solutions.  They found that their doubling of the air's CO2 concentration increased total seedling biomass by 134% in the low nitrogen treatment but by a smaller 98% in the high nitrogen treatment.  In addition, the elevated CO2 led to greater root growth in the low nitrogen treatment, as indicated by a 33% higher root:shoot ratio.

In light of these several results, it is clear that different species of trees may respond in qualitatively different ways to atmospheric CO2 enrichment in terms of their growth stimulation being greater or smaller under conditions of low vs. high soil nitrogen fertility.  In the majority of cases, however, as may be discerned by reviewing the results of similar studies conducted on aspen, pine and spruce trees (see appropriate links in the opening paragraph of this summary), the most common response is for the growth-promoting effects of atmospheric CO2 enrichment to be expressed to a greater degree when soil nitrogen fertility is optimal as opposed to less-than-optimal.

Gleadow, R.M., Foley, W.J. and Woodrow, I.E.  1998.  Enhanced CO2 alters the relationship between photosynthesis and defense in cyanogenic Eucalyptus cladocalyx F. Muell.  Plant, Cell and Environment 21: 12-22.

Maillard, P., Guehl, J.-M., Muller, J.-F. and Gross, P.  2001.  Interactive effects of elevated CO2 concentration and nitrogen supply on partitioning of newly fixed 13C and 15N between shoot and roots of pedunculate oak seedlings (Quercus robur L.).  Tree Physiology 21: 163-172.

Schortemeyer, M., Atkin, O.K., McFarlane, N. and Evans, J.R.  1999.  The impact of elevated atmospheric CO2 and nitrate supply on growth, biomass allocation, nitrogen partitioning and N2 fixation of Acacia melanoxylonAustralian Journal of Plant Physiology 26: 737-774.

Temperton, V.M., Grayston, S.J., Jackson, G., Barton, C.V.M. , Millard, P. and Jarvis, P.G.  2003.  Effects of elevated carbon dioxide concentration on growth and nitrogen fixation in Alnus glutinosa in a long-term field experiment.  Tree Physiology 23: 1051-1059.