A comparison of several dose-response models based on laboratory exposures of tree seedlings to sulfur dioxide

River birch and Virginia pine seedlings were exposed to 0.3, 0.6, 0.9, 1.2 and 2.4 ppm SO₂ (800, 1600, 2400, 3100, and 6300 μg m³, respectively) for 1, 2, 4, and 8 h in modified controlled environment chambers. Data quantifying the severity of SO₂ induced leaf necrosis provided by these exposures were used to evaluate dose-response models developed by O'Gara, Guderian et al., Zahn, and Larsen and Heck, or simple extensions of them. Model performance was assessed based on R² values and P-values from tests for aptness of the model. The four original models gave acceptable R² values but failed tests for aptness. Extensions of the Larsen-Heck and Zahn models performed better than the other models examined.