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.MANUAL OF FORESTRY 



TABLE LXVIII. PAPER BIRCH. YIELD PER ACRE. 

 PURE (100 PER CENT) BIRCH STANDS. 



Penobscot, Piscataquis, Somerset and Franklin counties, Maine. 

 (Data gathered by R. L. Marston for Paper Birch Study, 1903-1907.) 



Note. These sample plots were taken in unmanaged stands. All plots with a density less than 

 50 per cent were discarded. All plots containing less than 40 per cent birch were discarded and the 

 remainder reduced to 100 per cent birch by dividing the actual birch yield by the percentages of 

 the total basal area formed by the birch. Hence the table applies only to pure birch stands of aver- 

 age density (quality I, 83 per cent and quality II, 75 per cent). For the yield of a mixed stand, 

 containing, for example, 60 per cent of birch, a corresponding reduction would be made in the yield. 

 The number of trees per acre was exceedingly irregular and was, therefore, excluded from the table. 



The volume given is total stem volume, though the lowest measurement taken in the sample 

 trees was at 4.5 feet, and this disregard for butt swelling makes the yield conservative. 



Based on 20 quality I and 26 quality II, sample plots. 



