mean values for populations ranged from only 0.7 to 1.2 

 inches. Significant effects of populations in leaf length 

 reflected mean differences as large as 0.8 inch. And 

 finally, the significant effects of populations for adjusted 

 height show that populations would have differed in 

 3-year height even if all trees had been the same height 

 at age 2, even though 2-year height accounted for 64 

 percent of the variance in 3-year height of individual 

 trees. 



Significant interactions of populations and environ- 

 ments were detected only for adjusted height; conse- 

 quently, main effects for this variable were significant 

 with a rather low level of probability (table 2). The inter- 

 action was caused by (1) a lack of differences between 

 populations in the environment at high elevation, com- 

 bined with (2) statistically detectable differences at low 

 elevation. Consequently, subsequent analyses for 

 adjusted height use only those data from the low- 

 elevation site. 



Periodicity of Shoot Elongation 



The logistic function described periodicity of shoot 

 elongation of individual trees nearly perfectly. Values of 

 R- ranged from 0.94 to essentially 1.0 while averaging 

 0.99. Analyses of variance detected strong effects of 

 populations for duration, rate, cessation, and amount of 

 shoot elongation (table 3). These effects accounted for 21 

 to 38 percent of the total variance and are illustrated in 

 figure 2. Differences between populations were as large 

 as 15 days in cessation, 16 days in duration, 0.1 

 inch/day in rate, and 3.4 inches in the amount of elonga- 

 tion. Populations differed by only 0.8 day in the initia- 

 tion of shoot elongation, and, consequently, no differ- 

 ences could be detected statistically. 



Cold Hardiness 



Effects of test temperatures dominated analyses of 

 variance (table 4). These effects are associated with a 

 range in injury from 36 percent at —4 °F to 78 percent 

 at —12 °F. Effects of populations were significant but 

 accounted for only 5 percent of the total variance. Mean 

 differences between populations amounted to as much as 

 55 percent injury. 



5440 



5840 



10 20 30 40 50 



DAYS 



Figure 2.— Periodicity of stioot elongation for 

 populations from a range of elevations (feet) 

 ttiat represented maximum differences in 

 response. 



Patterns of Variation 



Elevation of the seed source had a pronounced effect 

 on population performance (table 5, fig. 3). Elevational 

 models accounted for more than 70 percent of the vari- 

 ance between populations for five variables and were 

 statistically significant for all variables except the initia- 

 tion of shoot elongation. As elevation increases, growth 

 potential decreases, largely because of an associated 

 decline in late growth and in the rate, duration, and ces- 

 sation of shoot elongation. Leaf lengths also decline with 



Table 3.— Results of analyses of variance for periodicity of shoot 



elongation presented as intraclass correlations, the ratio of a 

 variance component to the sum of all components 



Source of 

 variance 



Initiation 



Duration 



Rate 



Cessation 



Elongation 



Blocks 



0.10** 



0.04** 



0.03** 







0.01 



Populations 



.02 



.22** 



.21** 



0.23** 



.38** 



Interaction 



.15** 







.06 







.03* 



Within plots 



.73 



.73 



.70 



.77 



.58 



'Statistical significance of the F-value at the 5 percent level. 

 "Statistical significance of the F-value at the 1 percent level. 



4 



