ELEVATION OF SEED SOURCE, M 



Figure 3— Population means for six variables plotted by elevation of the seed source. 

 Localities A to E are keyed to figure 1. The length of each regression line reflects eleva- 

 tional distributions at each locality. Brackets quantify Isd (0.05). 



Figure 3 illustrates steep elevational clines for five 

 variables. The higher the elevation of the seed source, the 

 lower the 7-year height, the less the late growth, the 

 greater the needle cast, and the less the snow damage. 

 And, if all trees at PREF 640 had been the same height 

 after 5 years, the height of populations at age 7 still would 

 have been distributed according to elevational clines. 

 Moreover, the model for adjusted height at PREF 1,500 

 (fig. 3) shows that populations from about the same eleva- 

 tion as the 1,500-m planting site have grown the most 

 from a common height at age 5. 



Elevational clines for mites, spring frost injury, and ad- 

 justed height at Lost Valley are so gentle that they are 

 biologically insignificant. The model for shoot borers is not 

 presented because it was fit primarily to the population 

 for which 19 percent of the trees were infested. 



Because elevation and geography are not independent of 

 each other, geographic patterns of variation can be 

 described either as (1) performance at a constant elevation 

 or (2) performance at a base elevation, the lowest eleva- 

 tion that the species occurs at a given locality. Figxu-e 3 

 shows that populations at the base elevations for localities 

 A and E, for example, differ tremendously for most traits. 

 But most of these differences arise because populations at 

 base elevations occupy much different positions along the 

 elevational cline (fig. 3). 



Nevertheless, geographic variation at a constant eleva- 

 tion was significant for five of the variables (fig. 3). In all 

 cases, however, the differences barely exceeded Lsd (.05). 

 Therefore, geographic clines for a constant elevation can 

 be described by the relatively gentle clines of figure 4. In 

 this figure, geographic patterns are depicted by isopleths 



6 



