© 1997 Heron Publishing—Victoria, Canada
Simulating the response of mature yellow poplar and loblolly pine trees to shifts in peak ozone periods during the growing
season using the TREGRO model
John V. H. Constable (1, 2) and William A. Retzlaff (3, 4)
1. Department of Environmental and Resource Science, University of Nevada, Fleischmann Agriculture, Room 128, Reno, NV 89557-0013,
USA / 2. Department of EPO Biology, University of Colorado, Boulder, CO 80309-0334, USA / 3. Boyce Thompson Institute for Plant Research, Tower Road, Ithaca, NY 14853-1801, USA / 4. Author to whom correspondence should be addressed / Received August 12, 1996
Summary
Multiple TREGRO simulations were conducted with meteorological data files containing different growing season peak ozone (O3) episodes at O3 exposures of 1.0 and 2.0 × ambient O3 to assess the relationship between O3 response and the phenology of mature yellow poplar (Liriodendron tulipifera L.) and loblolly pine (Pinus taeda L.) trees. Regardless of O3 exposure and peak O3 episode occurrence, a peak O3 episode in August caused the greatest reduction in carbon (C) gain in yellow poplar, whereas a peak O3 episode in July caused the greatest reduction in C gain of loblolly pine. In both species, timing of the greatest simulated
O3 effect corresponded with the completion of the annual foliage production phenophase.
Simulated C gain of yellow poplar (total tree, coarse root, and total nonstructural carbohydrate) was reduced by O3 to a greater extent than the corresponding compartments in loblolly pine, but the opposite was true for fine roots. This
differential sensitivity to O3 reflects the fact that both C assimilation and the O3 response of the species were parameterized according to observed field measurements of each species. The differential sensitivity
to O3 of these species may have long-term implications for species composition in southeastern USA forests.
Keywords:
air pollutants, Liriodendron tulipifera, phenology, Pinus taeda, total nonstructural carbohydrates.
