EFFECTS ON SURVIVAL 



Except for the Coeur d'Alene ponderosa pine, and western white pine grown at very 

 high densities, soil fumigation seems to have increased the survival potential of the 

 stock (table 6). Differences were not great and the results were quite variable. 

 Particularly notable were the 9 and 16 percent average increases in survival of Douglas- 

 fir grown in fumigated soils and tested under severe and moderate moisture-stress 

 levels, respectively. Fumigation significantly reduced the survival potential of pon- 

 derosa pine grown at Coeur d'Alene and tested at the moderate moisture stress level. 

 In western white pine, both at Coeur d'Alene and at Savenac, there was no significant 

 effect of fumigation on survival potential at any moisture stress level. 



Although there is evidence that fumigation may reduce the survival potential of 

 2-0 ponderosa, this may not be a problem under the current practice of planting 1-0 

 rather than 2-0 stock. Fumigation, by stimulating early growth, may bring about severe 

 competition at an earlier age. Thus 2-0 stock grown in fumigated soil may be suffering 

 from rather severe competition which could be reflected in reduced survival capabilities 

 In contrast, the 1-0 stock is still relatively free growing in the nursery beds. Some 

 recent field tests show that there is very little, if any, difference in field survival 

 of 1-0 and 2-0 ponderosa pine grown in fumigated nursery soils. 



Table 6 . --Effects of moisture stress on survival of outplanted 2-0 stock grown in 



fumigated and imfxmigated soils 



Nursery and : 

 species : 



Low 



stress 





Moderate stress ', 



Severe stress 



Fum. 



Unfum . 



Diff. : 



Fum . 



Unfum . 



Diff. : 



Fum . 



Unfum. 



Diff. 











- -Percent survival^ - 









Coeur d'Alene 





















Ponderosa pine 



96 



97 



-1 



86 



92 



-6* 



60 



70 



-10 



Douglas-fir 



92 



89 



3 



71 



55 



16* 



46 



35 



9* 



Western white pine 



94 



97 



-3 



92 



91 



1 







1 



-1 



Savenac 





















Ponderosa pine 



96 



96 







95 



86 



9 



62 



53 



9 



Western white pine 





















Low density^ 



96 



94 



2 



97 



89 



8 



1 







1 



High density^ 



83 



93 



-10 



81 



84 



-3 















■^Percent of survival converted to arcsin yj% survival for statistical analysis. 

 ^From fumigation-seedbed-density interaction study (see table 5) . 

 *Differences significant at 95% probability level. 



18 



