Throughfall chemistry in a red maple provenance plantation sprayed with "acid rain"

Abstract

Trees of three red maple (Acer rubrum L.) seed sources in a plantation were sprayed with simulated acid rain (SO42-:NO3-, 2:1) at pH 5.2, 4.2, and 3.2 on five dates (May to September) and throughfall chemistry was monitored. All pH treatments produced throughfall that was less acid than the spray solution. Ca, K, Mg, and Fe were evident in throughfall on more than one date; concentrations generally were at their lowest levels in the spring, reaching a peak in mid to late summer. Na, Zn, and B were detectable only in September. Concentrations of all mineral elements in throughfall, except K, increased with increasing acidity of the spray solution. On most dates K showed little sensitivity to spray pH, but on the August application date K concentrations were significantly higher at pH 5.2 and 4.2 than at 3.2. There were small but significant differences among provenances in concentrations of Ca, Fe, and Zn in throughfall. Concentrations of mineral elements in throughfall resulting from simulated acid rain were similar to concentrations of elements in throughfall resulting from natural precipitation of comparable pH and time.