We measured plant water potential on the main 

 stem of each seedling before dawn using a pressure 

 bomb. 



Growth Chamber Tests 



We tested the effects of vermiculite slurry on lodge- 

 pole pine seedUngs in growth chambers. AU roots were 

 trimmed to 8 inches. The composition of the slurry 

 was a 12:10 ratio of number 4 grade agricultural ver- 

 miculite to water. The mixture was run through a 

 pump to grind up the vermiculite and form a muddy 

 suspension. Treated seedlings were dipped before 

 being potted in 9-inch pots. Control seedlings were 

 not dipped. Pots were randomly Eirranged in three 

 growth chambers. Conditions were set at 16 hours 

 light period daily, with temperatures of 75 °F during 

 light and 60 °F during dark. At the end of 1 month, 

 the seedhngs were carefully removed from the pots, 

 soil was washed from their roots, and the hght-colored 

 new roots were counted and measured. 



Growth Chamber Experiment 1— The objective 

 of our first experiment in the growth chamber was 

 to determine the effects of a vermiculite slurry root 

 dip on lodgepole pine root and shoot growth. It lasted 

 31 days in February and March of 1984. The sample 

 size was 30 seedlings: 15 dipped and 15 controls. The 

 potting medium was a 1:1:1 mixture by volmne of 

 sandy loam soil, peat moss, and vermicuMte. The pots 

 were watered to satiiration twice a week. 



Growth Chamber Experiment 2— The objective 

 of the second experiment was to determine the effects 

 of the same root-dip substance on the shoot and root 

 growth of lodgepole pine seedlings in four different 

 soils. It lasted 30 days in March and April of 1985. 

 The sample size was 48 seedlings. Six replications 

 of eight seedlings were divided between three growth 

 chambers, two replications in each chamber. Each 

 replication consisted of a dipped and an vmdipped tree, 

 planted in soils of four different origins: limestone 

 forest soil, granitic forest soil, basaltic forest soil, and 

 peat-vermicuhte-sandy loam (see Growth Chamber 

 Experiment 1). Pots were randomly arranged within 

 the growth chamber for each replication. Pots were 

 watered to saturation once each week. 



Greenhouse Tests 



Greenhouse temperatures were held between 60 and 

 80 °F at Lucky Peak Nursery. All pots were watered 

 to saturation once a week. As in the growth chamber 

 experiments, the seedlings were carefully removed 

 from thefr pots after 30 days, the soil was washed 

 fix)m their roots, and the new root growth was coimted 

 and measured. Other measurements included leader 

 elongation, plant water potential at 30 days, and the 



number of mycorrhizal root tips per 10-cm sample of 

 root. 



Greenhouse Experiment 1— The objective of 

 the first experiment was to determine the effects 

 of the vermiculite slurry root dip on shoot and root 

 growth of ponderosa pine and Douglas-fir seedlings. 

 It was conducted in March and April of 1984. Forty- 

 eight Douglas-fir and 48 ponderosa pine seedlings 

 were trimmed to a root length of 8 inches and potted in 

 9-inch pots. Eight blocks of 12 seedlings were grouped 

 on the center bench of the greenhouse. Each block 

 consisted of six ponderosa pine and six Douglas-fir 

 seedlings, half of them root dipped and half undipped, 

 planted in soils of three different origins: granitic for- 

 est soil, basaltic forest soil, and peat-vermicuhte-sandy 

 loam (see Growth Chamber Experiment 1). The root- 

 dip material was the vermiculite slurry described in 

 the growth chamber experiments. Pot arrangement 

 within each block was random. 



Greenhouse Experiment 2— The objective of the 

 second experiment was to determine the effects of four 

 different root-dip substances on shoot and root growth 

 of four conifer species planted on three different soils. 

 The experiment took place in March and April of 1985. 

 We tested four conifer species: Douglas-fir, Engehnann 

 spruce, lodgepole pine, and ponderosa pine. They 

 were treated in one of five ways: 



• Root dipped in a 12:10 (by volume) vermicuhte 

 and water mixtiu-e. 



• Root dipped in a vermiculite slurry with a 6:10 

 vermiculite-to-water ratio. 



• Root dipped in a vermiculite slurry with a 12:10 

 vermiculite-to-water ratio. 



• Root dipped in a vermiculite slurry with a 18:10 

 vermiculite-to-water ratio. 



• No root dip. 



Vermicuhte slurries were prepared in a blender. All 

 of the seedlings were potted in half-gallon cardboard 

 milk cartons. The potting soil was from three differ- 

 ent parent materials: granitic forest soil, basaltic for- 

 est soil, and a mixture of peat moss, vermiciihte, and 

 sandy loam (see Growth Chamber Experiment 1). 

 Seedlings from each of the root-dip treatments and a 

 control were potted in each soil. Five treatments for 

 each of three soUs for each of fo\ir species made a total 

 of 60 seedlings per block. Treatments were randomly 

 arranged in eight blocks. 



Field Tests 



All seedlings were stored, handled, and prepared for 

 planting according to Forest Service Intermoimtain 

 Region Reforestation Guidelines (Dahlgreen 1976). 

 Seedlings were divided into groups of about 20, and 

 the roots were submerged up to the root collars in a 



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