16 



BUIiiETIN 820, U. S. DEPARTMENT OF AGRICULTUBE. 



It is interesting to compare the growth, and yield of unmanaged 

 natural jack pine stands as shown in Tables 9 and 10, with the growth 

 and yield of well-managed Scotch pine stands in Europe, as shown in 

 Table 32 (appendix). In yield per acre the "good" quality site in 

 the Hubbard County table averages between site qualities II and III 

 for Scotch pine, and the "poor" quality site averages between IV 

 and V. In the matter of height, the Hubbard County trees on sites 

 whose quality is described as "good" and "poor" rank considerably 

 higher than the Scotch pine trees on the above-mentioned sites. 

 This may be partly accoimted for by the fact that Table 9 gives the 

 average dominant height, while Table 32 gives the average height 

 of the stand. In general, however, a comparison of the greater 

 heights and lesser yields of unmanaged jack pine stands with the 

 lesser heights and greater yields of managed Scotch, pine suggests 

 the possibility of increasing the yield of jack pine by growing it 

 under management. 



Table 13 gives the average annual increment in cubic feet and 

 board feet of the stands of different ages computed on the basis of 

 volumes given in Tables 9 and 10. 



Table 13. — Mean annual increment of pure, even-aged, densely stocked stands of jack 

 pine, figured in total cabic feet for trees. 5 inches and over in diameter, in hoard feet mill 

 scale for trees 5 inches and over and for trees 8 inches and over in diameter, and in board 

 feet by Scribner log rule for trees 8 inches and over in diameter. 





Total. 



Site quality good. 



Total. 



Site quality poor. 



Age. 



Mill scale. 



Scrib- 

 ner. 



Mill scale. 



Scrib- 

 ner. 





5 inches 

 and 

 over. 



5 inches 

 and 

 over. 



8 inches 

 and 

 over. 



8 inches 

 and 

 over. 



5 inches 

 and 

 over. 



5 inches 

 and 

 over. 



8 inches 

 and 

 over. 



8 inches 

 and 

 over. 



Years. 

 20 



Cu.ft. 

 36 

 44 

 54 

 71 

 74 

 72 

 69 

 67 

 64 

 62 

 60 



Cu.ft. 

 8 

 26 

 45 

 63 

 70 

 70 

 68 

 66 

 64 

 62 

 60 



Bd.ft. 

 25 

 128 

 230 

 300 

 330 

 331 

 326 

 316 

 308 

 302 

 294 



Bd.ft. 



Bd.ft. 



Cu.ft. 



Cu.ft. 



Bd.ft. 



Bd.ft. 



Bd.ft. 



25 



28 

 73 

 114 

 155 

 180 

 192 

 198 

 203 

 206 

 207 



12 

 23 

 40 

 58 

 84 

 104 

 113 

 115 

 117 

 117 



26 

 31 

 36 

 40 

 42 

 44 

 44 

 44 

 44 

 44 



5 

 16 

 25 

 32 

 37 

 40 

 41 

 42 

 43 

 43 



28 

 63 

 91 

 118 

 144 

 172 

 195 

 208 

 215 

 219 





30 



1 



35 



j 



40 



5 

 24 

 44 



62 

 82 

 102 

 117 





45 



9 



50 



16 



55 



27 



60 



42 



65 



S8 



70 



70 







STANDARD SITES. 



In figure 3 are exhibited all the available age-height data plotted 

 in accordance with Prof. Roth's plan for site classification.^ Accord- 

 ing to this plan all species whose dominant trees reach an average 

 height of only 90 feet in 100 years on the best sites (to be called Site 

 I for those species) are to be classified as standard C species, stand- 



1 See Forestry Quarterly, March, 1916. 



