Ozone Danger to Trees
Ozone Danger to Trees. Trees in urban and suburban settings directly affect air quality by altering the urban atmospheric environment. Yet, while trees contribute to healthier air, they are also harmed by an unhealthy environment.
Urban trees affect air quality in four major ways:
- Temperature reduction. Trees reduce energy consumption in summer by shading cars and buildings. A reduced air temperature due to the cooling effects of trees can improve air quality because the emissions of some pollutants and ozone-forming chemicals are temperature-dependent.
- Removal of air pollutants. Trees remove air pollution through uptake by leaf stomata (microscopic gates). Trees also remove pollution by intercepting airborne particles.
- Emission of volatile organic compounds. Because VOC emissions are temperature dependent and trees generally lower air temperatures, increased tree cover can lower overall VOC emissions, lowering ozone levels in urban areas.
- Energy effects on buildings. Trees reduce building energy use by shading buildings and lowering temperatures during the summer, and also blocking winds in winter.
Humans aren’t the only ones to be affected by recent ozone alerts in various parts of the country, Many of the most commonly planted trees in the nation’s urban forest also suffer from high levels of ozone pollution.
Ozone pollution is the result of a chemical reaction that converts car exhaust into ozone, a colorless unstable toxic gas, in the presence of light. The regions that have the highest automobile traffic and sunshine are the most at risk. But even areas without congested traffic may suffer since ozone is transportable over long distances. The pollutant acts as an oxidant that disrupts the chemical pathways in a plant’s photosynthetic powerhouse, the chloroplast. In response, the tree manufactures antioxidants such as vitamins E and C. This process may offer relief from low levels of ozone, yet are no match for repeated exposure to toxic levels.
Ozone injury on trees looks different on different species. On the leaves of poplar and black cherry, the homeowner may see brownish lesions on a leaf that appears water-soaked. On ash and hickory, however, the lesions are white. On other species, damage appears as a purple stippling all over the leaf. Evergreens appear to have burnt needle tips.
At present, the best thing homeowners can do to protect trees from ozone injury is to keep them in an overall healthy state. This includes protecting trees from wounding and keeping them well watered. Use fertilizer only if results of a soil test call for it.”
What to do
Call a Certified Arborist like Johnson Ops Tree Care can examine your trees to find the source of the problem.
Call us at 608 526-6297 for an appointment