Hogsett, William E., and C. P. Andersen. 1997. Ecological effects of tropospheric ozone: a U.S. perspective - past, present, and future. In: Fifth U.S.-Dutch International Symposium 1997(In press).
The paper reviews past research, including conclusions from the recent critical evaluation of the published literature for the 1996 EPA Oxidant Criteria Document, and discusses the direction for future research that WED scientists suggest is necessary for developing a national standard to protect ecological resources in the 21st century. Past and current research has focused primarily at the species-level developing quantitative exposure-response functions characterizing effects on biomass or reproduction (crop yield) in a single species to a single pollutant. This approach has been useful, in particular, to establish the need for a biologically-relevant exposure index for the National Ambient Air Quality Standard (NAAQS) protecting vegetation. However, the single pollutant, single species approach assumes that individual plant response does not change in the presence of other stresses or in natural systems where considerably more complexity is present (e.g. an assemblage of species, complex soil food webs, and competition for limited resources like nitrogen). The importance of this biological complexity was illustrated recently by WED scientists incorporating natural biological complexity belowground into potting soils which resulted in measured responses quite different from those predicted from individual plant studies using artificial media lacking natural soil foodwebs. The WED studies indicate that future research should focus on developing necessary linkages to extrapolate experimental data taken at the individual level, often in artificial conditions, to predict changes in more complex environments. WED scientists are presently involved in a number of experimental and modeling activities to address the problems of scale, complexity, and multiple stresses in forested ecosystems exposed to tropospheric ozone.