Sulfate concentrations in Norway spruce needles in relation to atmospheric SO2: a comparison of trees from various forests in Germany with trees fumigated with SO2 in growth chambers

Abstract

Concentrations of inorganic sulfur, organic sulfur and water-soluble cations and anions were determined in needles of young Norway spruce trees (Picea abies L. (Karst.)) that had been fumigated in growth chambers for weeks or months with different concentrations of SO₂, SO₂ plus ozone, or SO₂ plus NO₂. Measurements were also made on needles from older trees growing in forests in various regions of Germany with different mean annual atmospheric SO₂ emissions. In the fumigated young trees, sulfate accumulation in the needles was a linear function of atmospheric SO₂ concentration. Little or no sulfur was incorporated into the organic sulfur fraction. The mean accumulation rate of sulfate in needles of fumigated trees was about 0.4 nmol g_dw⁻¹ (nl l⁻¹)⁻¹ h⁻¹, which is very similar to the estimated rate of uptake of atmospheric SO₂ calculated from mean stomatal conductances (15 mmol m⁻² s⁻¹) and the external SO₂ concentration (the calculated rate of uptake was 0.37 nmol g_dw⁻¹ (nl l⁻¹)⁻¹ h⁻¹). Concentrations of organic acids and other inorganic ions did not change much in response to SO₂ fumigation.