Ozone Modeling
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Ozone Modeling

Objective:  A process-based model to predict the effects of ozone on photosynthesis was incorporated within an up-dated version of ECOPHYS to investigate whether the observed relative ozone-induced changes in partitioning in aspen clone 259 could be simulated from changes at the leaf level.


Predictions of ozone-induced reduction of carbon sequestration of forests under elevated tropospheric ozone concentrations require robust mechanistic leaf-level models scaled to the whole tree and stand level. This study tests a process-based model that predicts the effects of ozone on the photosynthetic rate of an ozone-sensitive aspen clone when scaled to the whole tree level, as a first step in the process of simulating the competitive response of genotypes to atmospheric and climate change.

 Model components:

ECOPHYS functional-structural process model of aspen and poplar (Rauscher et al., 1990; Host et al., 1999; Isebrands et al., 2000).
Biochemical mechanistic equations of photosynthesis (Farquhar et al., 1980; von Caemmerer and Farquhar, 1981; Sharkey, 1985)
Phenomenological stomatal conductance model (Ball et al., 1987; Harley et al., 1992)
Threshold flux/effective dose ozone model (Martin et al., 2000, based on data from Farage et al., 1991).

Genotype: Aspen clone 259

Ozone model (from Martin et al. 2000)


Relative dry weight accumulation and stem diameter growth


Model simulations of the relative growth response of ozone-sensitive aspen clone 259 under ozone exposure, compared with the charcoal filtered treatment, reflect the trends reported by Karnosky and co-workers (1996). In particular, the model showed that: 

  1. stem dry matter production and stem diameter are dramatically reduced by ozone, while the effect on stem height was small;
  2. ozone-induced earlier leaf abscission dramatically reduces both leaf dry matter production and retained leaf area, but with little or no effect on the number of leaves initiated.

These results corroborate earlier experimental findings (Coleman et al 1995) that the above-ground response of ozone-sensitive aspen to ozone exposure can be accounted for by the direct effects of ozone on photosynthesis. 


Work on the original ozone model was funded by the Natural Environmental Research Council, UK, under grant GT4/92/16/L; initial parameterization of the model for aspen clones was funded by a grant to the University of Essex, from Brookhaven National Laboratory. Development of the ECOPHYS project was funded jointly by the Computational Biology Program of the National Science Foundation, Grant No. DBI-972395, the Northern Global Change Program of the USDA Forest Service, and the US Department of Energy under interagency agreement No. DE-A105-800R20763.  Additional funding came from the NSF/DOE/NASA/USDA Joint Program on Terrestrial Ecology and Global Change through a co-operative agreement with Michigan Technological University. 

Literature Cited

Ball, J.T., Woodrow, I.E., Berry, J.A., 1987. A model predicting stomatal conductance and its contribution to the control of photosynthesis under different environmental conditions. In: Biggins, I. (Ed.), Progress in Photosynthesis Research, Vol. IV. Proceedings of the International Congress on Photosynthesis. Martinus Nihjoff, Dordrecht, pp. 221-224.

Coleman, M.D., Isebrands, J.G., Dickson, R.E., Karnosky, D.F., 1995a. Photosynthetic productivity of aspen clones varying in sensitivity to tropospheric ozone. Tree Physiology 15, 585-592.

Farage, P. K., Long, S. P., Lechner, E. G., Baker, N. R., 1991.  The sequence of change within the photosynthetic apparatus of wheat following short-term exposure to ozone. Plant Physiology 95, 529-535.

Harley, P.C., Thomas, R.B., Reynolds, J.F., Strain, B.R., 1992. Modelling photosynthesis of cotton grown in elevated CO2. Plant, Cell and Environment 15, 271-282.

Isebrands, J.G., Host, G.E., Lenz, K.E., Wu, G., Stech, H.W., 2000. Hierarchical, parallel computing strategies using Component Object Model for process modeling responses of forest plantations to interacting multiple stresses. In: Cuelemans, R.J.M., Veroustraete, F., Gond, V., Van Rensbergen J.B.H.F. (Eds.), Forest Ecosystem Modeling, Upscaling, and Remote Sensing. SPB Academic Publishing, The Hague, The Netherlands, pp. 123-135.

Farquahar, G.D., von Caemmerer, S., Berry, J.A., 1980. A biochemical model of photosynthetic CO2 assimilation in leaves of C3 species. Planta 149, 78-90.

Host, G. E.,  G. W. Theseira, C. Heim, J. G. Isebrands and R. Graham. 1999. EPIC-ECOPHYS: A linkage of empirical and process models for simulating poplar plantation growth. In: (A. Amaro and M. Tome Eds.) Empirical and Process Models for Forest Tree and Stand Growth Simulation.  Edicos Salamandra pp. 419-429.

Karnosky, D.F., Gagnon, Z.E., Dickson, R.E., Coleman, M.D., Lee, E.H., Isebrands, J.G., 1996. Changes in growth, leaf abscission, and biomass associated with seasonal tropospheric ozone exposures of Populus tremuloides clones and seedlings. Canadian Journal of Forestry Research 26, 23-37.

Martin, M.J., Farage, P.K., Humphries, S.W., Long, S.P., 2000. Can the stomatal changes caused by acute ozone exposure be predicted by changes occurring in the mesophyll? A simplification for models of vegetation response to the global increase in tropospheric elevated ozone episodes. Australian Journal of Plant Physiology 27, 211-219.

Rauscher, H.M., Isebrands, J.G., Host, G.E., Dickson, R.E., Dickmann, D.I., Crow, T.R., Michael, D.A., 1990. ECOPHYS: An ecophysiological growth process model for juvenile poplar. Tree Physiology 7, 255-281.

Sharkey, T.D., 1985. O2-insensitive photosynthesis in C3 plants. Plant Physiology 78, 71-75.

von Caemmerer, S., Farquhar, G.D., 1981. Some relationships between the biochemistry of photosynthesis and the gas exchange of leaves. Planta 153, 376-387.

The Northern Forest Ecosystem Experiment (NFEE) is funded by the US Forest Service. The Aspen FACE Experiment is funded principally by the U.S. Department of Energy's Office of Biological and Environmental Research. Additional support is from the USFS Global Change Program, Michigan Technological University, the Canadian Forest Service and the USFS Northern Research Station.
For more information on this project, contact Dr. Andrew J. Burton (Michigan Technological University) at (906) 487-2566 or mailto:ajburton@mtu.edu, or Dr. Mark E. Kubiske (Northern Research Station) at (715) 362-1108 or mailto:mkubiske@fs.fed.us.
For questions or suggestions regarding this website, please contact Janet Pikkarainen at mailto:jmpikkar@mtu.edu.
Last updated: July, 2010