THE CHARACTERIZATION AND COMPARISON OF OZONE EXPOSURE INDEXES USED IN ASSESSING THE RESPONSE OF LOBLOLLY-PINE TO OZONE

Using the 1988 and 1989 experimental results obtained for two loblolly pine half-sibling families (GAKR 15-23 and GAKR 15-91) at the Auburn University intensive field research site, we: (1) explored the performance of a set of exposure indices, (2) characterized the ambient air and charcoal-filtered air treatments at Auburn and compared the values of the O3 exposure indices with those values calculated for ambient O3 monitors for a select set of sites; (3) identified and characterized O3 treatments in the Auburn open-top exposure chambers where an adverse effect was noted; and (4) identified where such experimental exposure regimes occurred under ambient conditions. We found that the SUMO exposure index did not perform adequately. We were unable to distinguish among the performances of the SUM06, W126, and SUM08 exposure indices. The results of the analyses of six estimated logistic parameters for a model of diameter2 x height (d2h) vs time indicated O3 effects for both families. At pH 4.3 (near ambient conditions), a response to O3 was detected in the NF x 2.5 treatments for both families for t2, the approximate time of maximum growth during the second year. Using In (final d2h), family 23 did not show O3 effects. A comparison of the exposures experienced in the NF x 2.5 treatments with those occurring under ambient conditions at other locations showed that in 1983 and 1986, the San Bernardino County (CA) site experienced O3 exposures similar to those values experienced at the NF x 2.5 treatments in 1989.