io8 



FOREST COMMISSIONERS REPORT. 



Table 8. — Solid contents per stacked cord for paper birch spoolwood 

 bolts of different diameters, in the round. 



Table 9 shows the yield of pure paper birch stands at differ- 

 ent ages and in different situations. The best situations are desig- 

 nated as quality i, the medium situations as quality 2, and the 

 poorest situations as quality 3. Figures are given only for quali- 

 ties I and 2. The situations in which birch is found throughout 

 the region probably average slightly better than quality 2. The 

 yields given were obtained by a field party under R. L. Marston, 

 of the Forest Service, from 46 sample plots of different ages, 

 all of which contained at least 40 per cent birch and had a 

 density of over 50 per cent. Where the plots contained other 

 species in mixture the figures were reduced to correspond to a 

 pure (100 per cent) birch stand. Hence the table applies only 

 to pure birch stands of average density (83 per cent in quality 

 I, and 75 per cent in quality 2). For a mixed stand containing, 

 for example, 60 per cent of birch, a corresponding reduction 

 would have to be made in the yield. 



