Effects of ozone and acid rain on white pine (Pinus strobus) seedlings grown in five soils. III. Nutrient relations

Ozone treatments consisted of frequent exposure to 0.02, 0.06, 0.10 or 0.14 ppm ozone, while acid rain treatments consisted of exposure to simulated rain of pH 5.6, 4.0, 3.5 or 3.0. Plants were treated with all combinations of acid rain and ozone levels, and treatments were administered for 4 months. Acid rain caused significant leaching of Ca, Mg, K, Mn, Zn and Cd from leaf litter on the soil surface, and soil Mg and K content declined as well. Concentrations in needles of N, P, K, Ca, Mn, Cd and Cr were significantly increased as a result of acid rain treatment, and in roots, concentrations of N, Mn, Cd and Cr were significantly elevated. Similar increasing but nonsignificant trends were observed for Mg, Zn and Cu in needles and for P, K, Mg, Ca and Cu in roots. However, despite the increases in all the major nutrients, the nutrient weight proportions of K:N, P:N, Ca:N, and Mg:N generally declined in pine tissue as a result of acid rain. Significant differences between soils in response to acid rain were observed for some elements. Ozone had significant effects on K, Ca and Mn concentrations, and interactions between acid rain and ozone were observed for these elements. The effects of acid rain on tree nutrition may be roughly similar in different soils but the effects on physiology and growth will be heavily influenced by specific soil properties. -from Authors