Historic, archived document Do not assume content reflects current scientific knowledge, policies, or practices. “ POLUITIED ATR Miscellaneous Publication No. 1230 U.S. Department of Agriculture - Forest Service “Fair is foul, and foul is fair: Hover through fog and filthy air.” (Macbeth. Act 1, sc. 1, line 12). No, it didn’t happen overnight. The problem of polluted air has been festering for centuries—wit- ness Shakespeare’s Macbeth, 1605. It’s just that suddenly the problem of air pollution is becoming critical and is erupting in our sight. Not only do our eyes smart as they focus through murky air, but when the air clears, we see trees and vegetation succumbing. We must realize that this destruction can no longer be pinned to some mysterious cause. The one major culprit is air pollu- tion. Air Pollution: Where does it come from? Today’s air pollution is an unfor- tunate by-product of the growth of civilization and civilized man’s de- sire for goods that require heavy industrialization and mass produc- tion. Machines and factories some- times pollute and taint the air with substances that are dangerous to man and the environment. These in- clude radioactive dust, salt spray, herbicide and pesticide aerosols, liquid droplets of acidic matter, gases, and sometimes soil particles. These substances can act alone to irritate objects and forms of life. Or, more dangerously, they join to- gether to act upon the environment. Only lately have we begun recog- nizing some of their insidious con- sequences. 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 and death often follows. Air pollution may also cause hardwoods to lose their leaves. But because their leaves are only borne stresses; 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 3 been spotted up to 100 miles away from any metropolitan source. Along with the combustion of auto- mobile and ozone is added to air by disturbances in the outer stratosphere of the earth and by electrical Ozone probably injury to plants than any other aerial toxicant in the United States. The following lists, representing the personal observations and re- ports of many international scien- tists, are a compilation of the known responses by both hardwoods and sottwoods_ to pollutants. Check these lists before planting. industrial fuels, storms. causes more various SULFUR DIOXIDE SOFTWOODS Balsam fir (Abies balsamae) A “Tolerant” rating indicates that the tree species displays little or no sensitivity to a specific pollutant, but that it might behave differently under other tions. environmental condi- “Sensitive” trees respond to air pollution injury. Trees of “Intermediate” sensitivity show some response to air pollu- tants, but they are not truly tolerant. (These lists should not be taken as an absolute basis for assessing the responses of trees to pollutants. Considerable variation must be anticipated, because of genetic and environmental factors.) local White fir (Abies concolor) Silver fir (Abies pectinata) Lawson cypress (Cupressus lawsonianu) Juniper (Juniperus sp.) Larch (Larix sp.) Engelman spruce (Picea engelmannii) White spruce (Picea glauca) Jack pine (Pinus banksiana) Lodgepole pine (Pinus contorta latifolia) Western white pine (Pinus monticola) Dwarf mugo pine (Pinus mugo mughus) Austrian pine (Pinus nigra) Ponderosa pine (Pinus ponderosa) Eastern white pine (Pinus strobus) Douglas fir (Pseudotsuga menziesii) White cedar (Thuja accidentalis) Western red cedar (Thuja plicata) Mountain hemlock (Tsuga mertensiana) SULFUR DIOXIDE HARDWOODS Hedge maple (Acer campestre) Red maple (Acer rubra) Sugar maple (Acer saccharum) Mountain maple (Acer spicatum) Birch (Betula sp.) European hornbeam (Carpinus betulus) Catalpa (Catalpa sp.) White dogwood (Cornus florida) European beech (Fagus sylvatica) Green ash (Fraxinus pennsylvanica) Maidenhair tree (Gingko biloba) English holly (Ilex aquifolium) English walnut (Juglans regia) Tulip tree (Litriodendron tulipfera) Apple (Malus sp.) Texas mulberry (Morus microphylla) Black gum (Nyssa sylvatica) Sourwood (Oxydendron arboreum) American planetree (Platanus occidentalis) Oriental planetree (Platanus orientalis) Balsam poplar (Populus balsamifera) Eastern cottonwood (Populus deltoides) Bigtooth aspen (Populus grandidentata) Lombardy poplar (Populus nigra ‘Italica’) Quaking aspen (Populus tremuloides) Pear (Pyrus communis) English oak (Quercus robur) Red oak (Quercus rubra) Black locust (Robinia pseudocacia) Willow (Salix sp.) European mountain ash (Sorbus aucuparia) American elm (Ulmus americana) HYDROGEN FLUORIDE SOFTWOODS Juniper (Juniperus sp.) Western larch (Larix occidentalis) White spruce (Picea glauca) Colorado spruce (Picea pungens) Intermediate Tolerant Intermediate Lodgepole pine (Pinus contorta (latifolia) Dwarf mugo pine (Pinus mugo mughus) Ponderosa pine (Pinus ponderosa) Eastern white pine (Pinus strobus) Scotch pine (Pinus sylvestris) Loblolly pine (Pinus taeda) Douglas fir (Pseudotsuga menziesii) Japanese yew (Taxus cuspidata) Arborvitae (Thuja sp.) Sensitive Sensitive HYDROGEN FLUORIDE HARDWOODS Hedge maple (Acer campestre) Boxelder (Acer negundo) Silver maple (Acer saccharinum) Tree of heaven (Ailanthus altissima) European black alder (Alnus glutinosa) European white birch (Betula pendula) Cutlead European birch (Betula pendula ‘Gracilis’) Tolerant Intermediate European hornbeam (Carpinus betulus) Spanish chestnut (Castanea sativa) Cornelian cherry (Cornus mas) European filbert (Corylus avellana) Russian olive (Elaeagnus angustifolia) European beech (Fagus sylvatica) European ash (Fraxinus excelsior) Sensitive Green ash (Fraxinus pennsylvanica) Modesto ash (Fraxinus velutina ‘Modesto’) English holly (Ilex aquifolium) Black walnut (Juglans nigra) English walnut (Juglans regia) Red mulberry (Morus rubra) Paulownia (Paulownia sp.) Planetree (Platanus sp.) Oriental planetree (Platanus orientalis) Lombardy poplar (Populus nigra ‘Italica’) Quaking aspen (Populus tremuloides) Eugene poplar (Populus canadensis eugenei) Flowering apricot (Prunus americana) & Flowering plum (Prunus cerasifera) Bradshaw plum (Prunus domestica ‘Bradshaw’) ® Oriental cherry (Prunus serrulata) English oak (Quercus robur) Smooth sumac (Rhus glabra) Black locust (Robinia pseudoacacia) Willow (Salix sp.) European elder (Sambucus nigra) European red elder (Sambucus racemosa) European mountain ash (Sorbus aucuparia) American mountain ash (Sorbus domestica) American linden (Tilia americana) Little leaf linden (Tilia cordata) European linden (Tilia europaea) American elm (Ulmus americana) OZONE SOFTWOODS Balsam fir (Abies balsamea) White fir (Abies concolor) Western juniper (Juniperus occidentalis) European larch (Laris decidua) Japanese larch (Larix leptolepis) Incense cedar (Libocedrus decurrens) Norway spruce (Picea abies) White spruce (Picea glauca) Black Hills spruce (Picea glauca densata) Colorado spruce (Picea pungens) Knobcane pine (Pinus attenuata) Jack pine (Pinus banksiana) Coulter pine (Pinus coulteri) Jeffrey pine (Pinus jeffreyi) Sugar pine (Pinus lambertiana) Singleleaf pinyon pine (Pinus monophylla) Austrian pine (Pinus nigra) Ponderosa pine (Pinus ponderosa) Monterey pine (Pinus radiata) Red pine (Pinus resinosa) Pitch pine (Pinus rigida) Digger pine (Pinus sabiniana) Eastern write pine (Pinus strobus) Scotch pine (Pinus sylvestris) Torrey pine (Pinus torreyana) Virginia pine (Pinus virginiana) Douglas fir (Pseudotsuga menziesii) Giant sequoia (Sequoia gigantea) Redwood (Sequoia sempervirens) Arborvitae (Thuja sp.) 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