available; and (2) observations were for consecutive 

 or nearly consecutive years. Since periodicity in 

 cone production of western white pine tends to follow 

 3- and 4-year cycles, 1 yields for each tree were rep- 

 resented for nearly all stages of cyclic production. 

 It is therefore assumed that minimal confounding is 

 represented in the data. 



RESULTS AND DISCUSSION 

 Yield of Cones 



At tree ages of 30 to 50 years, annual production 

 of cones averaged about 28 per tree. This mean char- 

 acterizes cone production inadequately because yield 

 is subject to an interaction of exogenous and endogen- 

 ous factors . The interaction causes tremendous varia- 

 tion in cone production among seed years, geographic 

 localities, and maternal trees within each locality. 



Within the 18-year period, mean yield of cones 

 for individual seed years differed by as much as 55 

 cones per tree (table 1). In fact, the mean yield of 

 cones per tree, in successive seed years, differed by 

 as much as 34 cones. These differences in yield among 

 seed years reflect a periodicity in cone production 

 which is documented elsewhere in greater detail. 1 



Mean yield for geographic localities over all 

 years of observation differed by as much as 64 cones 

 per tree (table 2). However, the degree of difference 

 between localities depended on the seed year. For 

 instance, in 1967 which was a year of high mean yield, 

 localities differed by as much as 78 cones per tree; 

 but in 1956 when few cones were produced, maximum dif- 

 ferences between localities were only 20 cones per 

 tree. Thus, differences in yield among localities 

 were evident, especially in years of high yield. Lo- 

 calities characterized by low cone yields, however, 

 produced few cones even in favorable seed years. 



l G. E. Rehfeldt, A. R. Stage, and R. T. Bingham. 

 Time series analysis for production of female strobili 

 in western white pine. Manuscript in preparation. 



2 



