THE AUTHORS 



DENNIS E. FERGUSON is a research forester, Intermoun- 

 tain Research Station, Forestry Sciences Laboratory, 

 Moscow, ID. He has worked primarily with predicting 

 regeneration establishment and growth of young trees and 

 stands in the Northern Rocky Mountains. 



RAYMOND J. BOYD is a research forester (retired), Inter- 

 mountain Research Station, Forestry Sciences Laboratory, 

 Moscow, ID. He has an extensive research background 

 dealing with regenerating and managing young stands. 



RESEARCH SUMMARY 



Results of investigations on allelopathy of bracken fern 

 in northern Idaho are reported. The study objective was to 

 gain an understanding of how bracken fern interferes with 

 establishment of conifers and shrubs, often to their com- 

 plete exclusion. 



Containerized conifer seedlings grown in pots of soil 

 from a bracken fern glade grew less than seedlings grown 

 in pots of forest soil or potting mix. Mortality was minimal. 

 In greenhouse tests, bracken soil had little effect on ger- 

 mination of conifer and shrub seeds. Although statistically 

 significant differences were found in germination and 

 growth of shrub species, the differences are not significant 

 in a practical sense because sufficient seed of all species 

 became established and grew in greenhouse conditions. 

 Five soil depths were also tested to determine the depth to 

 which phytotoxins might be effective in preventing seedling 

 establishment. Only the 0- to 5-cm layer of bracken soil 

 decreased germination and growth of shrub species. 



Additional testing was conducted under field conditions. 

 Conifer seed was stratified over the winter on soils in 

 bracken glades and on potting mix transported to the site. 

 In the spring, seeds germinated well on both soil types, 

 but most seeds germinating on bracken soil died. Radicles 

 were long, indicating adequate germination energy, but 

 germinates died before shedding seedcoats. Radicles were 

 dark brown to black in color. Seeds that germinated on 

 potting mix were healthy and shed their seedcoats, but 

 some radicle tips were slightly discolored. 



Death of germinants in this study probably resulted from 

 absorption of bracken phytotoxins that have accumulated 

 in the soil over a number of years. Phytotoxins are thought 

 to be concentrated in a thin layer near the soil surface. 

 Allelopathy tests should be conducted under field condi- 

 tions because transporting, mixing, or drying the soil can 

 reduce the effect of phytotoxins bound in the soil complex. 



Intermountain Research Station 

 324 25th Street 

 Ogden, UT 84401 



