Air Pollution: 



What can it do to trees? 



Scientists have not yet been able 

 to amass a complete report on the 

 effects of air pollution on trees. 

 They do know, however, that sulfur 

 dioxide, fluorides, and ozone are 

 the major tree despoilers and that 

 individual trees respond differently 

 to the numerous particulate and 

 gaseous pollutants. Sometimes trees 

 growing in a single area under 

 seige by pollutants will show symp- 

 toms of injury or will die while 

 their neighbors remain healthy. Sci- 

 entists believe this difference in 

 response depends on the kind of 

 tree and its genetic makeup. Other 

 factors, such as the tree's stage of 

 growth and nearness to the pollu- 

 tion source, the concentration of 

 pollutant, and the duration of the 

 pollution onslaught will also play 

 a part. 



In short, whether or not a tree 

 succumbs as a result of air pollution 

 will depend on a combination of 

 host and environmental factors. 



For the most part, air pollutants 

 injure trees through their foliage. 

 Such foliar injury to conifers is 

 generally more drastic than injury 

 to hardwoods. It can cause conifers 

 to lose their year-round needles 

 prematurely. This precocious bald- 

 ing means that trees cannot main- 

 tain normal food-production levels. 

 Undernourished and weakened, 

 they are vulnerable to attack by a 

 host of insects, diseases, and other 

 environmental stresses; and death 

 often follows. 



Air pollution may also cause 

 hardwoods to lose their leaves. But 

 because their leaves are only borne 



for a portion of the year and are 

 replaced the following year, air 

 pollution injury to hardwoods may 

 not be so severe. 



Air Pollution: 



What can we do about it? 



Home and professional garden- 

 ers, landscapers, arborists, and 

 foresters should be aware of the 

 information available on the rela- 

 tionship between trees and air pol- 

 lution. When undertaking a planting 

 program, look out for nearby 

 sources of pollution. Then plant only 

 vegetation known to tolerate local 

 pollutants. 



You'll find that sulfur dioxide 

 wastes are being emitted from in- 

 dustrial complexes. Sulfur dioxide 

 originates from the combustion of 

 nearly every fuel, but especially 

 from coal and oil and from the heat- 

 ing of sulfide ores in the smelting 

 process. 



Industries and communities both 

 discharge gaseous and particulate 

 fluorides into the atmosphere from 

 the smelting of nonferrous ores, 

 steel, and aluminum; combustion of 

 coal; manufacture of brick, ceramics, 

 cement, glass, and phosphate fer- 

 tilizers; production and use of 

 hydrofluoric acid; and use of fluor- 

 ides as oxidizing agents in rocket 

 fuel. Fluorides are more damaging 

 to vegetation than equivalent con- 

 centrations of other air pollutants. 

 And fluorides in their gaseous form 

 are more harmful than particulate 

 fluorides. 



You'll find ozone — the major 

 pollutant in smog — enshrouding 

 densely populated metropolitan 

 areas; however, ozone damage has 



