FOREST PLANTING IN THE INTERMOUNTAIN REGION. 



41 



planting regions to demonstrate this point clearly. In Table 19, 

 however, an attempt has been made to indicate the probabilities of 

 the case by applying a factor to the rainfall of certain valley stations 

 with long records, which will indicate the rainfall at altitudes in 

 that general region where planting is carried on (western yellow 

 pine). This factor has been determined for each region by a careful 

 study of rainfall increment with altitude, during the summer months 

 for many United States Weather Bureau stations in each region. It 

 is evident from this table that while Utah suffers from no such pro- 

 tracted period of drought as California, conditions at the time of 

 planting and for the two months following are more severe in Utah, 

 drying the plants before they become established. 



Table 19. — Rainfall interpolated by 10-day periods following the average date of 

 planting western yellow pine in different parts of the West. 





Rainfall. 



Days after planting. 



Eastern Ore- 

 gon, May 4. 



Colorado, 

 Apr. 7. 



Western 

 Montana, 

 Apr. 20. 



Northern 



California, 



May 1. 



Utah, 

 May 10. 



1-10 



Inches. 

 0,76 

 1.04 

 1.63 

 .81 

 .71 

 .42 

 .38 

 .17 

 .14 

 .17 

 .26 

 .23 

 .47 

 .40 

 .45 



Inches. 



0.75 

 .98 

 .92 

 .81 

 .97 



1.08 

 .66 

 .30 

 .47 

 .55 

 .68 

 .57 

 .50 

 .52 

 .38 



Inches. 

 0.61 

 .66 

 .90 

 .79 

 1.02 

 1.07 

 .65 

 .58 

 .44 

 .35 

 .28 

 .19 

 .29 

 .63 

 .47 



Inches. 

 1.09 



.71 

 .55 

 .38 

 .35 

 .18 



Inches. 



0.69 



11-20 



.64 



21-30 



.50 



31-40 



.32 



41-50 



.12 



51-60 



.18 



61-70 



.22 



71-80 





.15 



81-90 





.20 



91-100 





.25 



101-110 





.32 



111-120 





.32 



121-130 . 



.16 

 .22 



.87 



.22 



131-140 



.33 



141-150 



.50 







Total 



8.04 

 Baker City- 



10.14 

 Denver 



8.93 

 Helena 



4.51 

 Red Bluff... 



4.96 



Base station used - . ... . 



Salt Lake City. 







The high mortality during the first growing season is due primarily 

 to the inability of the roots to absorb moisture from the soil as 

 rapidly as it is lost from the leaves through transpiration. This may 

 be due to several factors within the plant such as (1) improper bal- 

 ance between root and top (over amount of transpiring surface), 

 (2) failure of roots to develop new growth, (3) inability of the roots 

 to grow fast enough to keep abreast of the falling water level, (4) 

 wilting with a relatively high moisture content of the soil due to 

 either a large amount of nonavailabie moisture in the soil or a low 

 concentration of the sap of the plant, or (5) a relatively high trans- 

 piration rate in comparison with the absorbing surface of the roots. 

 On the other hand, with plant conditions satisfactory, high mor- 

 tality may be due to unfavorable site factors such as (1) a deficiency 

 of soil moisture due to the inability of the soil to conduct moisture 

 to the roots as fast as they absorb it or a rapid reduction of moisture 

 below the point of availability, (2) lack of shade inducing high 

 transpiration, and (3) a physically impervious soil with low porosity 

 or a nigh lime content which may induce chlorosis. 



To avoid losses from summer drought, planting should be made 

 at as high elevations as the adaptability of the species in question 



