How does rising atmospheric CO2 affect marine organisms?

Click to locate material archived on our website by topic


Ozone (Effects on Plants -- Tree Species: Beech) -- Summary
In discussing the problem of elevated tropospheric ozone (O3) concentrations, Liu et al. (2004) wrote that "ozone is considered to be one of the air pollutants most detrimental to plant growth and development in both urban and rural environments (Lefohn, 1992; Skarby et al., 1998; Matyssek and Innes, 1999)," because it "reduces the growth and yield of numerous agronomic crops as well as fruit and forest trees (Retzlaff et al., 1997; Fumagalli et al., 2001; Matyssek and Sandermann, 2003)." In addition, they say that ozone concentrations are "currently two to three times higher than in the early 1900s (Galloway, 1998; Fowler et al., 1999)," and that they likely "will remain high in the future (Elvingson, 2001)." Hence, in our quest to determine how the ongoing rise in the atmosphere's CO2 concentration might impact this unfortunate situation, we here briefly summarize the results of studies that have examined the issue as it pertains to European beech (Fagus sylvatica L.) trees.

Liu et al. (2005) grew 3- and 4-year-old European beech seedlings for five months in well watered and fertilized soil in containers located within walk-in phytotrons maintained at either ambient or ambient + 300 ppm CO2 (each subdivided into ambient and double-ambient O3 concentration treatments, with maximum ozone levels restricted to <150 ppb), in both monoculture and in competition with Norway spruce, after which they examined the effects of each treatment on leaf non-structural carbohydrate levels (soluble sugars and starch). In doing so, they found that the effects of elevated O3 alone on non-structural carbohydrate levels were small when the beech seedlings were grown in monoculture. When they were grown in mixed culture, however, the elevated O3 slightly enhanced leaf sugar levels, but reduced starch levels by 50%.

With respect to elevated CO2 alone, for the beech seedlings grown in both monoculture and mixed culture, levels of sugar and starch were significantly enhanced. Hence, when elevated O3 and CO2 significantly affected non-structural carbohydrate levels, elevated CO2 tended to enhance them, whereas elevated O3 tended to reduce them. In addition, the combined effects of elevated CO2 and O3 acting together were such as to produce a significant increase in leaf non-structural carbohydrates in both mixed and monoculture conditions. As a result, the researchers concluded that "since the responses to the combined exposure were more similar to elevated pCO2 than to elevated pO3, apparently elevated pCO2 overruled the effects of elevated pO3 on non-structural carbohydrates."

In a slightly longer study, Grams et al. (1999) grew European beech seedlings in glasshouses maintained at average atmospheric CO2 concentrations of either 367 or 667 ppm for a period of one year. Then, throughout the following year, in addition to being exposed to the same set of CO2 concentrations the seedlings were exposed to either ambient or twice-ambient levels of O3. This protocol revealed that elevated O3 significantly reduced photosynthesis in beech seedlings grown at ambient CO2 concentrations by a factor of approximately three. In contrast, in the CO2-enriched air the seedlings did not exhibit any photosynthetic reduction due to the doubled O3 concentrations. In fact, the photosynthetic rates of the CO2-enriched seedlings actually rose by 8% when simultaneously fumigated with elevated O3, leading the researchers to conclude that "long-term acclimation to elevated CO2 supply does counteract the O3-induced decline of photosynthetic light and dark reactions."

Last of all, in a still longer study, Liu et al. (2004) grew 3- and 4-year-old beech seedlings for two growing seasons under the same experimental conditions as Liu et al. (2005) after the seedlings had been pre-acclimated for one year to either the ambient or elevated CO2 treatment. At the end of the study, the plants were harvested and fresh weights and dry biomass values were determined for leaves, shoot axes, coarse roots and fine roots, as were carbohydrate (starch and soluble sugar) contents and concentrations for the same plant parts. This work falsified the hypothesis that "prolonged exposure to elevated CO2 does not compensate for the adverse ozone effects on European beech," as it revealed that ALL "adverse effects of ozone on carbohydrate concentrations and contents were counteracted when trees were grown in elevated CO2."

These results are certainly good news for the biosphere (and especially for beech trees), as well as for human activities that result in CO2 being emitted to the atmosphere. In addition to the latter activities having their own "excuse for being," they have the doubly good fortune of producing a byproduct that goes on to fight -- and overpower -- the deleterious consequences of one of the world's most devastating air pollutants.

References
Elvingson, P. 2001. For the most parts steadily down. Acid News 3: 20-21.

Fowler, D., Cape, J.N., Coyle, M., Flechard, C., Kuylenstrierna, J., Hicks, K., Derwent, D., Johnson, C. and Stevenson, D. 1999. The global exposure of forests to air pollutants. In: Sheppard, L.J. and Cape, J.N. (Eds.). Forest Growth Responses to the Pollution Climate of the 21st Century. Kluwer Academic Publisher, Dordrecht, The Netherlands, pp. 5032.

Fumagalli, I., Gimeno, B.S., Velissariou, D., De Temmerman, L. and Mills, G. 2001. Evidence of ozone-induced adverse effects on crops in the Mediterranean region. Atmospheric Environment 35: 2583-2587.

Galloway, J.N. 1998. The global nitrogen cycle: changes and consequences. Environmental Pollution 102: 15-24.

Grams, T.E.E, Anegg, S., Haberle, K.-H., Langebartels, C. and Matyssek, R. 1999. Interactions of chronic exposure to elevated CO2 and O3 levels in the photosynthetic light and dark reactions of European beech (Fagus sylvatica). New Phytologist 144: 95-107.

Lefohn, A.S. 1992. Surface Level Ozone Exposure and Their Effects on Vegetation. Lewis Publishers, Chelsea, UK.

Liu, X.-P., Grams, T.E.E., Matyssek, R. and Rennenberg, H. 2005. Effects of elevated pCO2 and/or pO3 on C-, N-, and S-metabolites in the leaves of juvenile beech and spruce differ between trees grown in monoculture and mixed culture. Plant Physiology and Biochemistry 43: 147-154.

Liu, X., Kozovits, A.R., Grams, T.E.E., Blaschke, H., Rennenberg, H. and Matyssek, R. 2004. Competition modifies effects of ozone/carbon dioxide concentrations on carbohydrate and biomass accumulation in juvenile Norway spruce and European beech. Tree Physiology 24: 1045-1055.

Matyssek, R. and Innes, J.L. 1999. Ozone - a risk factor for trees and forests in Europe? Water, Air and Soil Pollution 116: 199-226.

Matyssek, R. and Sandermann, H. 2003. Impact of ozone on trees: an ecophysiological perspective. Progress in Botany 64: 349-404.

Retzlaff, W.A., Williams, L.E. and DeJong, T.M. 1997. Growth and yield response of commercial bearing-age "Casselman" plum trees to various ozone partial pressures. Journal of Environmental Quality 26: 858-865.

Skarby, L., Ro-Poulsen, H., Wellburn, F.A.M. and Sheppard, L.J. 1998. Impacts of ozone on forests: a European perspective. New Phytologist 139: 109-122.

Last updated 7 June 2006