Use of a single-tree simulation model to predict effects of ozone and drought on growth of a white fir tree.

A physiologically based, single-tree simulation model, TREGRO, was parameterized with existing phenological, allometric, and growth data and used to predict effects of ozone and drought on growth of a 53-year-old white fir (Abies concolor (Gord. & Glend.) Lindl. exHildebr.) tree following a 3-year model simulation. Multiple experimental simulations were conducted to assess the individual and interactive effects of ozone (O3) exposure and drought on growth of white fir. The effects of O3 were imposed as reductions in carbon (C) assimilation of 0, 2.5, 5, 10, and 20%. Drought was imposed as 0, 10, 25, and 50% reductions in total annual precipitation. The results of the simulations were compared with the effects of O3 on white fir seedlings grown in the presence and absence of ozone in open-top chambers and with a field survey of white fir trees subjected to a gradient of O3. [ABSTRACT FROM PUBLISHER]