In the laboratory seedbed experiments, all of the seedbed materials were very 

 moist, with uniform temperatures. In the field seedbed experiments, the opening seedbed 

 received more rain and snow than the canopy seedbed. The opening seeds all had greater 

 germination, although there was some difference between opening treatments. Together 

 these two experiments suggest that the seedbed on which pine seeds overwinter is not 

 greatly significant providing there is adequate moisture. 



ALLELOPATHY AND MYCORRHIZAE 



It is well known that most forest tress require mycorrhizal associations for good 

 growth and survival. Although trees can survive without mycorrhizae, under natural 

 conditions they usually become stunted and may die (Meyer 1973) . Therefore, chemicals 

 from natural foliage leachates, the decomposition of litter, or chemicals from micro- 

 organisms produced during litter decomposition that inhibit the growth and development 

 of mycorrhizae could indirectly reduce the growth and development of conifer seedlings. 



Handley (1963) describes the suppression of tree growth when planted on ancient 

 Calluna heathlands in Europe. He attributed the inhibition to antibiotics (phytotoxins) 

 produced by the Calluna roots or its associated mycorrhizae that inhibited the growth 

 and development of mycorrhizal associates on the sensitive tree species. Without suffi- 

 cient mycorrhizae tree growth was checked. Brown and Mikola (1974) conducted experiments 

 that indicated that lichens, particularly Cladon'la alpestvis , produce toxic chemicals 

 that adversely affect the mycorrhizae of pine and spruce seedlings in Finland and con- 

 sequently reduce their growth. 



The effect of pine leachates and extracts were not tested for toxicity to associ- 

 ated ectomycorrhizae in these experiments, but the mycorrhizae were examined on pine 

 seedlings grown under a variety of conditions at the field study site. The field results 

 will be presented in a separate publication. 



Future allelopathic studies of tree species with ectomycorrhizal associates should 

 include investigation into both the direct suppression of seedlings by phytotoxins, as 

 well as the indirect suppression of seedlings through the inhibition of mycorrhizae. 



SUMMARY 



Volatile compounds present in ponderosa pine tissues (green needles, surface litter, 

 decomposing duff, roots, and bark) did not inhibit the germination of pine seeds and the 

 growth of seedling radicles. In the tests for water-soluble inhibitors, the germination 

 of ponderosa pine seeds was inhibited by the 10 percent bark solution, the 5 and 10 

 percent duff solution, the natural stemflow, the 5 and 10 percent green needle solution, 

 and the 5 and 10 percent root solution compared to the rainwater controls. Throughfall, 



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