16 BULLETIN 820, U. S. DEPARTMENT OF AGRICULTURE. 
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 IT and IIT 
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 accounted 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 cubic feet for trees 5 inches and over in diameter, in board 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. 
Site quality good. Site quality poor. 
j Serib- : Serib- 
Mill scale. Mill scale. 
Age. Total. net Total. pee 
5 inches | 5 inches | 8 inches | 8 inches 5 inches | 5 inches | 8 inches | 8 inches 
and and and and and and and and 
over. over. over. over. over. over. over. over. 
Years. | Cu.ft. | Cunft. | Ba.ft. | Ba.ft. | Baje. | Cu.ft. | Cu.ft. | Ba.ft. | Ba.fe. | Ba. fe 
20 36 | 
LigSad.ccos ive eee cna escccsucs Haccoudee| Soodecona| WEaadcdscllacococosslkacsccess 
Scan IIe 44 26 128 28 12 26 5 28 = bE occ aoe eee 
SIR RESBodce 54 45 230 73 23 31 16 G3 Bi eee eae Sas seococ 
SORE ee ses 71 63 300 114 40 36 25 Ue Be es Rasen 
40S eeeee 74 70 330 155 58 40 32 118 eel Pearse 
a Dacseuacce 72 70 331 180 84 42 37 144 24 9 
OO nS aati 69 68 326 192 104 44 40 172 44 16 
WE GAG SGar 67 66 316 198 113 44 41 195 62 27 
WE ooseeoue 64 64 308 203 115 44 42 208 82 42 
Gobesarenna 62 62 302 206 117 44 43 215 102 58 
(Wb ncassoos 60 60 294 207 117 44 43 219 117 70 
STANDARD SITES. 
Tn 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- 
1See Forestry Quarterly, March, 1916. 
