I have been looking at the effects of ozone pollution on
vegetation productivity and carbon sequestration. Ground-level ozone has been
observed to inhibit photosynthesis by direct cellular damage. I have
incorporated the empirical approach of Ollinger et
al. (1997) and Reich (1987) derived for deciduous and coniferous trees and
crops to the TEM model. This method inversely relates gross primary
productivity (GPP) to accumulated hourly ozone levels. The ozone values are
based on the AOT40 index, which is a measure of hourly-accumulated ozone above
a threshold of 40 ppb. In order to apply the equation to TEM, I have developed
a gridded map of AOT40 for the U.S. developed from the EPA CASTNET and AIRS
datasets, and a globally, gridded map of AOT40 values based on the MIT
Integrated Global System Model (IGSM) and MATCH models. Results for the
Figure 1: a) Location of CASTNET (filled circles) and AIRS (asterices) sites containing hourly ozone data for the
Figure 2: Transient Net Carbon Exchange (NCE) responses from 1950-1995, showing how ozone effect compares to other disturbances. Effect of CO2 fertilization, climate variability, land use, agricultural management, ozone, and the cross terms between ozone and nitrogen fertilization on cumulative carbon sequestration. All units in (Tgyr-1).
Figure 3: a) Mean global AOT40 (ppm-hr)
for June-July-August of 1998, b) Map of mean annual Net Primary Productivity
(NPP) percent difference between the ozone and control simulations for the
years 1989-1993. Largest decrease is
60.0% and largest increase is 8%, which occurs for only 2.6 % of grids. Most significant decreases in NPP occur in
the southeastern half of the
Felzer, B., Kicklighter, D., Melillo, J., Wang, C., Zhuang,
Q., and R. Prinn. (2004). “Effects of ozone on
net primary production and carbon sequestration in the conterminous
Felzer, B. S., Reilly, J. Melillo, J., Kicklighter, D. W., Sarofim, M., Wang, C., Prinn, R. G., and Q. Zhuang. (2005). “Future effects of ozone on carbon sequestration and climate change policy using a global biochemistry model”, Climatic Change, 73 (3): 345-373.
Felzer, B. S., Cronin, T., Reilly, J. M., Melillo, J. M. and Wang, X. 2007. Impacts of ozone on trees and crops. Comptes rendus Geosience. 339/11-12: 784-798 DOI: 10.1016/j.crte.2007.08.008.
Ren, W., Tian, H., Liu, M., Zhang, C., Chen, G., Pan, S., Felzer, B., Xu, X. 2007. Effects of tropospheric ozone pollution on net primary productivity and carbon storage in terrestrial ecosystems of China. Journ. Geophys. Res. 112, D22S09, doi:10.1029/2007JD008521.