THE AUTHORS 



RESEARCH SUMMARY 



CLINTON E. CARLSON is research forester with the 

 Forestry Sciences Laboratory in Missoula, Mont. He 

 earned his B.S. in forest science in 1964, M.S. in forestry 

 in 1966, and Ph.D. in botany in 1978 from the University 

 of Montana. From 1966 until 1979 he was plant patholo- 

 gist with the Northern Region, USDA Forest Service, 

 where he conducted field and laboratory studies on the 

 effects of air pollutants on forest ecosystems. Since 

 1979 he has conducted silvicultural research at the Inter- 

 mountain Forest and Range Experiment Station in 

 Missoula. 



CARMA J. GILLIGAN is biological technician with the 

 Forest Pest Management Group in the Northern Region, 

 USDA Forest Service. She has done technical field and 

 laboratory work with effects of air pollution, insects, and 

 biotic disease on forest ecosystems since 1970. Her 

 work often is the basis for reports and publications con- 

 cerning interrelationships between insects, diseases, 

 and forest ecosystems. 



ACKNOWLEDGMENTS 



We are indebted to Charles Van Hook for his help in 

 conduct of the fumigations and care of the experimental 

 material. 



Histological analyses of pollutant-caused necrosis of 

 Pinus ponderosa and Pseudotsuga menziesii current- 

 year foliage laboratory-fumigated with hydrogen fluoride, 

 sulfur dioxide, and ethyl mercaptan, showed that necro- 

 sis caused by phytotoxic gases can be differentiated 

 from that induced by winter drying, drought, and salt. 

 Hypertrophy and hyperplasia of vascular parenchyma, 

 endodermis collapse, and intense vascular staining were 

 characteristic of injury caused by the pollutants in both 

 species, but were not found in needles injured by the 

 other causes. 



Similar analyses were done on necrotic 2- to 3-year-old 

 conifer foliage collected in the field near industrial 

 sources of fluoride, sulfur dioxide, mercaptans, and 

 hydrogen sulfide and from specimens collected from 

 sites known to have been injured by winter drying. 

 Species included Pinus contorta, Pinus ponderosa, 

 Pseudotsuga menziesii, Pinus sylvestris, and Pinus flex- 

 Ms. As in the laboratory fumigations, winter drying in- 

 jury was readily distinguished from that caused by 

 phytotoxic gases. The internal symptoms caused by in- 

 dustrial fumigations were similar to those induced by 

 gases under controlled conditions and symptoms of 

 winter drying from field-collected specimens were 

 similar to those simulated in the laboratory. These 

 results differ substantially from conclusions reached in 

 a similar study in 1973. The present study shows that 

 histological analysis should be useful in diagnosing air 

 pollution-induced injury and damage in coniferous 

 forests. 



The use of trade, firm, or corporation names in this publication is for the informa- 

 tion and convenience of the reader. Such use does not constitute an official en- 

 dorsement or approval by the U.S. Department of Agriculture of any product or 

 service to the exclusion of others which may be suitable. 



