458 Forestry Quarterly 



contained from 5 to 80 trees per acre. Upon closer examination, 

 it was noted that 28 trees per acre was the dividing line, so to 

 speak, between the average and the maximum, for only 14 acres 

 out of the total 700 contained more than 28 trees per acre. 

 Below 28 inches the stands were divided as follows and the 

 entire 700 acres classified: 



TABLE 1 



No. Trees No. Acres Per Cent 

 Class per Acre Measured of Total 



I Very open 5-9 222 32 



II Open 10-15 220 31 



III Medium 16-20 148 21 



IV Dense 21-28 96 14 



V Very dense 28-80 14 2 



Total 700 100 



From this table it will be seen that a large majority, in fact 

 84 per cent, of our Yellow pine stands contain 20 trees or less 

 per acre. If distributed evenly over an acre, these trees, young 

 and old, would be about 50 feet apart. This condition imme- 

 diately reflects the conditions of soil exposure, drouth and brush, 

 which, as a matter of fact, are present. 



The various density classes were found to conform very 

 closely to various sub-types in the Yellow pine region. It seems 

 only natural that the density of a stand should be closely related 

 -o the site which that stand occupies. In general, the lower the 

 iltitude and the drier the site, the more open the stand ; and the 

 ligher the altitude up to a certain limit, the greater the amount 

 )f soil and atmospheric moisture available, the greater is the 

 endency towards a mixture with other species, the denser is the 

 3tand and the better the forest conditions. The description of 

 zhese classes is as follows : 



I. Very open. — (5-9 trees per acre.) Usually pure, but occa- 

 sionally mixed with Lodgepole pine of poor quality. Soil : light 

 volcanic ash. Site : poor, open, dry, sage-brush flats. Elevation : 

 5400 to 5700 feet. 



II. Open. — (10-15 trees per acre.) Usually pure, but occa- 

 sionally mixed with White fir ; on lava flats with heavy under- 

 g^rowth of manzanita and snow-brush. Soil : volcanic ash with 

 loam and clay. Elevation : 5400 to 5700 feet. 



III. Medium. — (16-20 trees per acre.) Sometimes pure, but 

 often mixed with White fir and Lodgepole pine ; on lava flats 

 with light to medium cover of snow-brush and manzanita. Soil: 

 volcanic ash, with considerable loam and clay. Elevation: 5400 

 to 5700 feet. 



