Table 5 — Average lodgepole pine root growth after 30 days and average seedling heights and survival after 3 years on the 

 Targhee National Forest. Treatment means showed no significant differences (a = 0.05) 



New root growth 



Treatment 



No. of roots 

 0.2-1.5 cm/tree 



Roots 



>1.5 cm 



No. mycorrhlzal 

 root tips/1 0-cm 

 sample 



Third year 



No./tree 



Avg length 



Height 



Survival 





A/0. - - 





cm 



No. 



cm 



Percent 



Vermiculite 



51 



7 



2.1 



15 



37.6 



70 



Vermiculite slurry 



26 



9 



2.7 



17 



33.9 



60 



Terra Sorb® 



67 



11 



2.5 



19 



34.0 



62 



Not dipped 



54 



15 



2.5 



18 



33.6 



61 



Vermiculite 

 Slurry 



Terra Sorb® 

 Not dipped 



Years 



Figure 8 — Average lodgepole pine seedling 

 survival from 480 seedlings after the first three 

 growing seasons on the Targhee National 

 Forest (field experiment 2). Seedlings were 

 root dipped in vermiculite, vermiculite slurry, 

 or Terra Sorb®, or they were not dipped. 



growing seasons (fig. 11). However, spring measure- 

 ments indicated most of that mortality took place 

 during the first winter, probably fi"om the stresses 

 of the preceding summer. Survival was very good 

 between the second and third years. 



Discussion 



We conducted two experiments in the growth cham- 

 ber, two in the greenhouse, and two in the field. In 

 these tests, the effects of root dipping depended on 

 root-dip treatment, soil parent material, and conifer 

 seedling species. We tightly controlled environments 

 in the growth chamber experiments. The greenhouse 

 experiments allowed us to trade some of the control 

 for an increased sample size. In the field experiments 



we examined whether our results applied in a practi- 

 cal sense. The data showed a great deal of vEtriabUity. 

 Nevertheless, I found good consistency in the results 

 between most of the greenhouse and growth chamber 

 experiments and field tests. 



The root-dip treatments we studied did not increase 

 seedling root growth. None of the treatments had 

 much effect on the mean length of new roots or mycor- 

 rhizae production. The number of long roots, the total 

 length of long roots, and the number of short roots 

 was the same for undipped seedlings as for dipped 

 seedlings or was even better. Most of the time, vermic- 

 ulite and hydrophilic gels did not reduce root growth. 

 However, the thicker the vermicuMte slurry treatment, 

 the more detrimental it was to root growth. 



The exception was in the second field experiment 

 where the vermiculite slurry increased seedling root 

 growth over the undipped seedlings. This may be 

 because the site conditions were moister during the 



Years 



Vermiculite Slurry Terra Sorb® Not dipped 



Figure 9 — Average lodgepole pine seedling 

 heights from 480 seedlings after the first three 

 growing seasons on the Targhee National For- 

 est (field experiment 1 ). Seedlings were root 

 dipped in vermiculite, vermiculite slurry, or 

 Terra Sorb®, or they were not dipped. 



8 



