THE TYPE. 



mixed stand appears to be due to the influence of the original forest, 

 composed of yellow pine alone or perhaps yellow pine and Douglas 

 fir in mixture, which moderated conditions of light, temperature, 

 and soil and air moisture to an extent which made possible the en- 

 trance of spruce. 



Both the western yellow pine and the Douglas fir are older than 

 the spruce, and the yellow-pine veterans range from 75 to 125 years 

 older than those of the fir. All the spruce alive at present has come 

 in within the last 150 years, most of it within the last 100 years. 

 According to this the present yellow-pine veterans were over 200 

 years old and the Douglas fir over 100 years old when the spruce now 

 present gained a foothold. On certain areas within the spruce-pine 

 subtype all the spruce has entered within the last 50 years. Even 

 here there is no evidence of a former generation of spruce. 



AVERAGE STAND. 



A stand survey of the composite type was made to determine 

 accurately the number of trees per acre as well as the volume in 

 board feet. Five plots selected in different localities throughout the 

 type were taken as an average of the whole. The timber on these 

 plots, which aggregated 500 acres, or approximately 0.3 per cent of the 

 entire area covered by the type, was actually measured. All the 

 trees of each species 4 inches diameter breast high and over were 

 calipered and recorded by inch diameter classes. 



Table 1 shows the average number of trees per acre by diameter 

 classes for five species — white fir and Mexican white pine in addition 

 to the three principal species of the type. 



Table 1. — Stand on sample acre of composite type. 



Diameter breast 

 high. 



Trees per acre. 



Yellow 

 pine. 



Douglas 

 fir. 



Spruce. 



White 

 fir. 



White 

 pine. 



All 



species. 



Inches. 

 4 



1.42 



1.72 



1.71 



1.68 



1.67 



1.48 



1.44 



1.33 



1.12 



1.06 



1.02 



.93 



.94 



.83 



.83 



.77 



.'65 

 .62 

 .52 

 .51 

 .49 

 .40 

 .44 

 .38 



1.80 



1.89 



1.70 



1.52 



1.39 



1.36 



1.16 



1.11 



.89 



.91 



.73 



.59 



.53 



.45 



.48 



.42 



.38 



.35 



.34 



.29 



.29 



.30 



.29 



.24 



.25 



1.19 



1.55 



1.48 



1.33 



1.52 



1.19 



1.14 



.97 



.81 



.69 



.44 



.38 



.26 



.23 



.20 



.12 



.09 



.07 



.05 



.04 



.04 



.02 



.01 



.02 



.01 



0.08 

 .12 

 .11 

 .09 

 .14 

 .11 

 .08 

 .08 

 .09 

 .06 

 .09 

 .08 

 .08 

 .06 

 .06 

 .06 

 .05 

 .07 

 .07 

 .06 

 .06 

 .05 

 .06 

 .05 

 .06 



0.61 

 .52 

 .45 

 .40 

 .34 

 .30 

 .26 

 .22 

 .20 

 .16 

 .17 

 .12 

 .15 

 .15 

 .12 

 .12 

 .12 

 .12 

 .07 

 .09 

 .06 

 .07 

 .08 

 .05 

 .06 



5.1 

 5.5 

 5.4 

 5.0 

 5.0 

 4.4 

 4.1 

 3.7 

 3.1 

 2.9 

 2.5 

 2.1 

 2.0 

 1.7 

 1.7 

 1.5 

 1.3 

 1.3 

 1.2 

 1.0 

 1.0 

 .9 

 .8 

 .8 

 .8 



5... 



6 



7. 



8 



9 



10 



11 



12... 



13 



14... 



15 



16 



17 



18 . 



19 



20 . 



21 



22 



23 



24 



25 



26 . 



27 



28.... 





