germination to a later date, thereby reducing the growing period. It also appeared to 

 act as a physical barrier to vertical seedling growth. Competition from understory 

 vegetation was low, but under those poor growing conditions any competition would be an 

 additional detriment. McDonald (1976) also observed growth impairments where seedlings 

 grew near large overstory pines. 



SUMMARY AND CONCLUSIONS 



Approximately 45 percent of all seeds planted during the fall of 1974 germinated in 

 the spring and early summer of 1975. Germination was much higher on the opening treat- 

 ments than on the pine-associated treatments. The presence of an overhead canopy or a 

 combination of canopy and organic matter reduced germination percentages and rates. 



Moisture, temperature, and light appeared to be the important factors in the germi- 

 nation of ponderosa pine seeds. Snow did not accumulate as deep- under pine canopies and 

 it often melted earlier in the spring than snow in the openings, exposing pine seeds to 

 fluctuating temperature and moisture conditions. Therefore, proper stratification may 

 not have been provided, thus reducing the seeds' ability to germinate. Also, soils with 

 abundant organic matter may have higher moisture tensions and provide poorer seed-soil 

 contact, thereby adding to the unfavorable germination conditions. 



Two weeks after the start of germination, seedlings began to die. Eight categories 

 of mortality were recognized and are listed in order of decreasing importance (numbers 

 of seedlings destroyed); cutworm damage, bird or small mammal damage, chlorotic and 

 brittle (unknown), disappearance, poor root development, sun scald, miscellaneous, and 

 damping-off. When mortality and growth data are being considered, careful attention 

 must be given to the unusually high summer precipitation occurring during this study. 

 Drought, normally a significant detriment to seedling establishment, was not an apparent 

 cause of mortality. Even though ponderosa pine is one of the region's most drought- 

 resistant conifers, mortalities would have likely been higher and growth rates lower with 

 normal rainfall. 



Treatment, as well as location, was a determining factor in the number of seedlings 

 lost. Survival tended to be best on those treatments that were devoid of all surface 

 vegetation. The presence of litter had a variety of effects which likely worked syner- 

 gistically with other factors such as plot location and amount of overhead canopy. In 

 general, the least mortality was observed on treatments with no ground cover, that is, 

 bare mineral soil. 



Initial establishment, or actual numbers of living seedlings at the end of the first 

 growing season, was greatest in the opening treatments. Ponderosa pine seed germina- 

 tion and seedling survival were enhanced in the presence of overstory pine trees by the 

 removal of understory vegetation and the organic layer. However, better results were 

 obtained when seedlings grew some distance from the overstory in addition to removing 

 the ground cover. 



Although the number of seedlings produced is important in the reforestation of 

 conifers, seedling health and vigor are also significant. The effects of fire stimu- 

 lated seedling growth above that in all other treatments. Fire reduced litter and com- 

 peting vegetation, and enriched the soil by releasing nutrients, especially ammonium- 

 nitrogen, phosphates, and potassium, from the organic matter. 



22 



