Sulphur oxide injury
Damage, symptoms and biology
SO2 or sulphur dioxide is one of the main atmospheric pollutants. SO2 is transported over great distances, especially when it is released from the tall smokestacks of industrial facilities that burn fossil fuels. The problem thus reaches well beyond industrial regions, threatening forests located in areas with good air quality. Because it is a gas, SO2 is transported readily by air currents. It can also penetrate needles and leaves, where it dissolves into the cellular fluids and becomes transformed into an acid, leading to cell destruction. SO2 also dissolves in the clouds, forming acid precipitation, which damages the upper layers of leaves and needles and penetrates into the organs, causing serious metabolic disturbances. Acid precipitation also leads to acidification of the soil and leaching of the nutrients contained in the soil. Various types of damage result from the combination of these different phenomena. A frequent sign of damage is yellowing and discoloration of needles in conifers and tissue necrosis followed by defoliation in deciduous trees.
As a rule, conifers are more sensitive to the environmental disturbances caused by sulphur dioxide. Wheat and apple trees are particularly sensitive to this pollution source, but maples appear to have some resistance.
Canadian Forest Service Publications
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