NORWAY PINE IN THE LAKE STATES. 



21 



sand barrens where there are small openings may, even in the case of 

 plantations, be from three-fourths to one-fourth of these amounts. 

 Table 11 is based on 85 sample plots from 40 to 200 years old. 



Table 11. — Yield per acre of fully stocked even-aged stands according to three quality 



classes. 





Yield per acre. 



Age 









(years). 



Quality I. 



Quality II. 



Quality HI. 





Board ft. 



Board ft. 



Board ft. 



40 



4,100 



2,000 





50 



9,400 



6,100 



2,800 



60 



15, 100 



10, 200 



5,300 



70 



20, 900 



14,300 



7,900 



80 



26, 500 



18, 600 



10, 700 



90 



32, 300 



22, 900 



13, 700 



100 



38, 500 



27, 400 



16, 900 



110 



44, 700 



32, 000 



20, 100 



120 



50, 800 



36, 700 



23, 100 



130 



56, 800 



41,200 



25, 800 



140 



60, 500 



43,900 



27, 900 



150 



62, 300 



45, 700 



29, 500 



160 



63, 300 



46, 900 



30, 600 



170 



63, 700 



47, 500 



31, 100 



180 



03, 700 



47, 700 



31,300 



190 



63, 000 



47, 300 



31,300 



200 



61, 800 



46, 500 



31,000 



The mean annual growth in board feet culminates on all the quali- 

 ties of site at about 140 years. There is a slight further increase in 

 volume until 170 years on Quality I, and to 180 years on Qualities II 

 and III, but the mean annual growth per acre falls off, and soon 

 the stand itself begins to lose in volume from windfalls, old age, and 

 fire. The maximum mean annual yield on good soils hardly exceeds 

 400 per year, and on Quality III sites 200 feet. These yields are for 

 natural Norway pine sites, whose quality is at best much below that 

 of soils occupied by white pine and hardwoods. Since Norway pine 

 will grow on any well-drained soil, if started in full sunlight, yields 

 from plantations, even when unthinned, on the richer soils may 

 amount to from 500 to 800 board feet per acre per year. Since Nor- 

 way pine can form fully stocked stands only under ideal conditions 

 of light and moisture, which are seldom met with in nature, the aver- 

 age stand per acre of pine, either Norway or white, actually comes 

 nearer to being 5,000 or 10,000 feet, instead of the 40,000 or 60,000 

 feet yielded by fully stocked areas. 



The openings in ordinary stands of Norway pine are occupied by 

 poplar, birch, and scrub oaks, although none of these species do as 

 well as Norway pine on sandy soils. Even if these inferior species 

 could be utilized, nothing like the returns can be secured as from fully 

 stocked stands of Norway pine. It is safe to say that with complete 

 stocking the average production of large areas can be increased five- 

 fold. 



The number of trees on fully stocked areas depends in part on the 

 width and shape of the crown. Table 12 gives an idea of the average 

 width of crowns of trees of different diameters. 



