DISCUSSION 



It must be emphasized that 3 years is a small climatic sample from which to draw 

 valid general conclusions or recommendations. On the other hand, 3 years of results 

 obtained under fairly well known study conditions provide a better basis for the com- 

 parisons of planting date effects in northern Idaho than was previously possible. 



Under the conditions represented in this study, spring plantings have had an over- 

 all survival advantage for all species tested. In one of the 3 test years (1968-69), 

 this general advantage shifted slightly from spring to fall planting, which, resulted 

 in a nonsignificant F test for the effect of season in the analysis of variance. After 

 an examination of the long-range weather records, we believe that the results for the 

 1968-69 series of plantings are not in line with normal long-term expectations because 

 of a fortuitous and unusual combination of climatic occurrences. The 1968 fall plant- 

 ing season was unusually moist and cool, which probably contributed to the better over- 

 all survival of fall-planted trees (66 percent compared to 42 percent the previous 

 2 years). In the spring of 1969, the 20-day June drought and attendant low soil mois- 

 ture undoubtedly contributed to a reduction in the survival of spring-planted trees 

 (50 percent compared to 72 percent in the previous 2 years). Similar, but less severe, 

 spring droughts have occurred in about 6 of the past 30 years. Occurrence of both 

 situations the same planting year must have a low probability. Use of some nondormant 

 stock the spring of 1969 also contributed to reduced survival of spring-planted stock. 

 Therefore, we feel that gross comparisons between fall and spring planting for the first 

 2 years of the study are probably closer to long-range expectations than comparisons 

 of averages for all 3 years. 



Regardless of how it is computed, the average survival advantage of spring planting 

 has been considerably greater in tliis study than that indicated in earlier comparisons 

 (Schopmeyer 1940). This difference could be attributed to (a) improved handling and 

 consequent better survival of spring-planted stock, (b) average climatic conditions 

 during our study period that did not approximate average climatic conditions during 

 the period from which Schopmeyer 's survival averages were compiled, or (c) a narrower 

 base of site conditions in this study compared to Schopmeyer' s summary. 



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