1134 
Journal of Agricultural Research 
Vol. XXXI, No. 12 
fir attains a greater average mature height than yellow pine; and that 
consequently land is site 3 for white fir which for yellow pine is only 
site 4. This tentative conclusion further indicates that more wood 
per acre can be produced on a given area by white fir than by yellow 
pine. 
The indication is, indeed, that for stands with the same average 
mature heights, white fir produces more wood per acre than yellow 
pine. This can readily be explained by the greater ability of white 
nr to endure shade, and consequently to tend toward a greater num- 
Fig. 11 —Yields per acre in white fir type 
ber of trees per acre than yellow pine. It is thus probably true that 
white fir has decidedly the greater wood-producing capacity on a 
given piece of land. Whether future forest management shall favor 
pine or fir will depend primarily on the relative advantages of a high 
yield of less intrinsically valuable white fir and a lower yield of more 
valuable yellow pine. 
SUMMARY 
The present study indicates that on an average western yellow 
pine site, by preserving the young growth already on the ground 
under many of the virgin stands, a yield up to 40,000 board ieet an 
acre can be obtained. This rate of growth is exceeded in several of 
