occur so infrequently that managers might risk transfer- 

 ring fast-growing populations into severe environments in 

 an attempt to increase productivity. Indeed, genetic dif- 

 ferentiation may have been detected at levels associated 

 with productive differences so small as to be immaterial. 

 On the other hand, small adaptive differences observed at 

 young ages may portend large differences in the future. 

 Regardless, verification can come only from planting pro- 

 grams that not only incorporate these guidelines but also 

 maintain precise records on the exact location from which 

 planted trees originated. Productivity of such plantings 

 will test the applicability of these guidelines. 



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Baker, F. S. Mountain climates of the western United 



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 Draper, N. R.; Smith, H. Applied regression analyses. 



New York: Wiley and Sons; 1981. 407 p. 

 Madsen, J. L.; Blake, G. M. Ecological genetics of 



ponderosa pine in the northern Rocky Mountains. Silvae 



Genetica. 26: 1-8; 1977. 

 Rehfeldt, G. E. Ecological adaptations in Douglas-fir 



{Pseudotsuga menziesii var. glauca) populations. I. North 



Idaho and northeast Washington. Heredity. 43: 383-397; 



1979a. 



Rehfeldt, G. E. Genetic variation in southern Idaho 

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Rehfeldt, G. E. Genetic gains from tree improvement of 

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Rehfeldt, G. E. Adaptation of Pinus contorta populations 

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Rehfeldt, G. E. Ecological adaptations in Douglas-fir 

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Rehfeldt, G. E. Adaptive variation in Pinus ponderosa 

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SAS Institute. SAS user's guide: statistics. Gary, NC: 

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Wang, C. Genetics of ponderosa pine. Research Paper 

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