Lichens are indicators of 



ozone and other pollutants. 



Lichen species disappear as 



pollution increases. 



Lichens and mosses are "poikilohydric" organisms, mean- 

 ing they cannot maintain constant internal moisture the 

 way most plants do. Daily drying and wetting cycles 

 concentrate pollutants dissolved in rain, fog, or dust in 

 tissues, independent of their sensitivity to air pollution. 

 Lichens are thus excellent accumulators of sulfur, nitrogen, 

 and metals, as well as more elusive but long-lived pollut- 

 ants such as radioactivity and pesticides. Deposition 

 patterns and "hot spots" of specific air pollutants can be 

 mapped by analyzing their concentrations in samples of 

 lichens and mosses. 



Lichens As Bioindicators 



Lichens (plants made up of a symbiotic as- 

 sociation of alga and fungus) are sensitive to 

 common pollutants in the Pacific Northwest: 

 sulfur dioxide; oxidants such as ozone, acid 

 rain, and fluorine; and some metals. Lichen 

 species vary in their sensitivity to different pol- 

 lutants. The presence or absence of different 

 lichen species and the symptoms of pollution 

 injury can help locate places with relatively 

 high amounts of air pollution. 



Lichens are being inventoried and monitored 

 extensively west of the Cascades. Initial analy- 

 sis of monitoring results showed a curious ab- 

 sence of leafy, nitrogen-fixing (air-pollution 

 sensitive) lichens and an unexpected abun- 

 dance of nitrogen-loving (pollution tolerant) li- 

 chens in the Willamette Valley and the Colum- 

 bia River gorge. 



Acidity of Cloud Water 



Water in clouds and fog can become acidic 

 through interaction with atmospheric pollut- 

 ants. Plants can absorb this acidic moisture 

 through aboveground parts or through their 

 roots after the moisture condenses and drips 

 to the ground. Acidic cloud water can inhibit 

 growth of sensitive species. Cloud water was 

 monitored during the summer of 1991 at Stam- 

 pede Pass and Granite Peak in the Alpine Lakes 

 Wilderness, and during the summer of 1994 

 at Green Mountain in the Glacier Peak Wilder- 

 ness. The minimum acidity of cloud water (pH 

 3.6) collected in 1991 for both sites was far 



more acidic than is necessary to Inhibit growth 

 of some species. Unfortunately, the only In- 

 formation currently available about effects on 

 local species Is for conifer seedlings exposed 

 to acidic fog under controlled conditions. More 

 Information Is needed about the effects of 

 acidic cloud water, as well as Injury thresh- 

 olds to local species, before cause for concern 

 is verified. 



MONITORING METHODS 



Changes in forest health can be detected by 

 monitoring the condition of the forest. 



Several monitoring tools and methods are 

 available for measuring the forest. Some have 

 been used for years; others are new and have 

 had only limited use. Many forest monitoring 

 programs, such as forest Inventories, focus pri- 

 marily on vegetation condition and change. 

 Other parts of the environment — like weather, 

 air quality, riparian habitat, fisheries, and wild- 

 life — are measured in separate surveys or, more 

 recently. In multiresource surveys. 



Aerial Survey 



The Forest Service and the States of Oregon 

 and Washington began a cooperative aerial 

 survey for insect damage in 1947; only National 

 Forests and some state lands were surveyed. 

 From the 1960s and continuing to the present, 

 all forested lands In the two states, regardless 

 of ownership, are surveyed by air. The states 

 also fly special aerial surveys to track specific 



Overview — 2 1 



