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

The effects of acid rain and ozone on nutrient relations of white pine (Pinus strobus L.) were assessed for potted seedlings grown in each of five forest soils. 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 treatments. In roots, concentrations of N, Mn, Cd, and Cr were significantly elevated as a result of acid rain. 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. Although the above relationships were relatively consistent for pine in all soils, 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 three elements. In general, the results of these experiments suggest that the effects of acid rain on tree nutrition may be roughly similar in different soils but that the effects on physiology and growth will be heavily influenced by specific soil properties.