PLANTING STUDY 

 Procedures 



In the spring of 1984, soil was collected at Eagle Point 

 and placed in 1.9-liter pots. The four treatments were 

 bracken glade, bracken glade sprayed in 1977 (Znerold 

 1979), adjacent forest, and forestry potting mix (1:1 ratio 

 of peat and vermiculite). Five replications were sampled in 

 each treatment, with 10 soil samples taken from each 

 replicate, for a total of 200 pots. The soil was lifted intact 

 by pushing a hollow metal cylinder into the ground, clamp- 

 ing onto the sample, lifting it out, and placing it into the 

 pot. 



Pots were randomly arranged by replication in a shade- 

 house (50 percent reduction in light) in Moscow, ID. Two 

 container-grown seedlings were planted in each pot— one 

 Douglas-fir and one grand fir in the first 100 pots, and 

 two Engelmann spruce (Picea engelmannii) in each of the 

 other 100 pots. Plastic fruit container lids were sealed, 

 inverted, and placed under individual pots to provide a 

 reservoir of water, reduce leaching, and prevent transfer 

 of leachates among pots. 



Seedlings were grown for two summers. Fresh bracken 

 fern litter was not added between growing seasons. At the 

 end of the second summer, seedlings were measured for 

 second-year height growth and total green top weight. 



Results 



Few seedlings died— four grand fir and two spruce. But 

 tops or branches sometimes died in the bracken treat- 

 ments. Eighteen trees had tops or branches that were 

 dead; of these, 14 trees were from one of the bracken fern 

 treatment soils. 



Height growth during the second year and total green 

 top weight were chosen to test treatment differences. 

 Growth the year of planting is largely a function of pre- 

 determined buds while growth the second year reflects 

 conditions experienced by the seedlings since planting. 

 Total green top weight was recorded as an expression of 

 biomass production. 



Results of analysis of variance are shown in table 1. The 

 number of trees in each analysis is reduced by the number 

 of dead trees and, in the case of growth, the number of 



trees with dead tops. Patterns are similar for all three 

 species. Trees in forest and potting mix soils consistently 

 outperform either of the bracken treatments. Trees in the 

 forest soil or potting mix have about 1.8 times the height 

 increment and 1.6 times the top weight of those in the 

 bracken soil treatments. Growth and top weight are con- 

 sistently lower in the sprayed bracken compared to the 

 unsprayed, but this difference is not significant in most of 

 the comparisons. 



Treatment differences may be conservative in that litter 

 was not added between the two growing seasons and the 

 soil plug around the roots of container-grown seedlings 

 provided a reserve of soil not influenced by bracken fern. 

 Long-term effects on mortality are unknown because, in 

 natural conditions, conifer roots may contact bracken 

 rhizomes or residues from decomposing fronds. 



BIOASSAY STUDY 

 Procedures 



This study was conducted in conjunction with the plant- 

 ing study just described. The objective was to determine if 

 bracken soil reduced germination and growth of woody 

 species and, if so, how far into the soil might the phyto- 

 toxins be effective. 



Three native soil treatments were used: bracken glade, 

 sprayed bracken glade, and adjacent forest. Five soil pits 

 per treatment were dug to a depth of 60 cm or to soil 

 parent material, whichever was deeper. Six soil samples 

 were collected from each pit at levels of to 5 cm, 13 to 

 18 cm, 28 to 33 cm, 43 to 48 cm, 60 to 90 cm, and a mix- 

 ture of the five levels. Soil was transported in plastic bags 

 to the Moscow laboratory. 



Seeds of eight species were sown in this test: Douglas- 

 fir, grand fir, Engelmann spruce, subalpine fir {Abies 

 lasiocarpa), Rocky Mountain maple (Acer glabrum), huckle- 

 berry (Vaccinium globulare), Sitka alder (Alnus sinuata), 

 and chokecherry (Prunus virginiana). Seeds were sown in 

 l-liter pots, with 2 species per pot, 25 seeds per species. 

 Thus, the study design is 3 treatments x 5 replications x 

 6 depths X 8 species x 25 seeds per species, for a total of 

 18,000 seeds. Conifer seed was not stratified, but shrub 

 seed had been stratified by a local nursery specializing in 

 growing native plants. 



Table 1— Planting study: containerized seedling mean 1985 height increment (growth) and total 

 green top weight (top weight) by treatment and species. Within column, means 

 followed by different letters are significantly different at the 5 percent level, using 

 Duncan's multiple range test 



Douglas-fir 



Grand fir 



Spruce 



Treatment 



» 



Growth 



Top 

 weight 



Growth 



Top 



weight 



Growth 



Top 

 weight 





mm 



9 



mm 



9 



mm 



9 



Bracken 



35.4" 



117.3"= 



32.2"'= 



109.8" 



19.3" 



25.3" 



Sprayed 



31.4" 



91.0== 



19.9"= 



78.1"= 



16.9" 



24.1" 



Forested 



57.3^ 



155.6" 



49.9^ 



129.9" 



32.6' 



38.5' 



Potting mix 



68.3=' 



266.4^ 



38.9^" 



160.1^ 



29.1' 



32.3' 



No. of trees 



92 



100 



93 



96 



198 



198 



5 



