Predicting the regional impact of ozone and precipitation on the growth ofloblolly pine and yellow-poplar using linked TREGRO and ZELIG models

To simulate the long-term effects of ozone on forests in the US, we linked TREGRO, a mechanistic model of an individual tree, to ZELIG, a forest stand model, to examine the response of forests to five ozone exposure regimes ( 0 to similar to 100 ppm h SUM06 per year) in 100-year simulations. TREGRO a nd ZELIG were parameterized using biological and meteorological data from t hree climate sites in the southeastern US. TREGRO was used to generate 3-ye ar exposure-response relationships between ozone and growth of loblolly pin e (Pinus taeda L.) and yellow-poplar (Liriodendron tulipifera L.). Ratios ( response at ozone exposure: response at base case) of total tree mass, leaf mass, and line root/leaf mass were calculated and used to modify growth fu nctions in ZELIG. At the end of the ZELIG simulation, the change in basal a rea of loblolly pine ranged from an increase of 44% to a decrease of 87%, d epending on precipitation and ozone exposure. The basal area of yellow-popl ar, simulated in competition with loblolly pine was not affected over most of its range. Over the range of the two species, the simulated changes in b asal area due to ozone exposure were generally within +/- 10% of the base c ase. Competitive interactions between the species were not altered. (C) 200 1 Elsevier Science B.V. All rights reserved.