WESTERN YELLOW PINE IN OREGON. 



19 



small group by themselves, the reason being that a group of many 

 yoimg trees usually starts in the gap which a large one makes when 

 it dies. In the virgin stands throughout the State there seems to be 

 a very large proportion of trees whose age is about 225 or 275 years, 

 suggesting that after this age their mortality is greater. 



Table 5 shows the uneven age of an average yellow-pine stand. 

 It is an enumeration of the trees of each age on a logged-over tract 

 near Embody, Lake County, the rings on the stumps of practically 

 all the sound merchantable trees being counted. 



Table 5. — Number of trees of each age by decades on a representative 40-acre tract near 

 Embody, Oreg., only trees {cut in a clean-cutting logging operation) whose annual 

 rings could be counted being taken. 





Num- 





Num- 





Num- 





Num- 



Age. 



ber of 



Age. 



ber of 



Age. 



ber of 



Age. 



ber of 





trees. 





trees. 





trees. 





trees. 



100 



4 



190 



22 



280 



15 



370 



3 



110 



2 



200 



19 



290 



9 



380 



1 



120 



13 



210 



8 



300 



7 



390 



1 



130 



8 



220 



13 



310 



11 



400 



5 



140 



14 



230 



17 



320 



8 



410 



2 



150 



31 



240 



28 



330 



13 



420 



2 



160 



16 



250 



21 



340 



10 



430 



1 



170 



21 



260 



13 



350 



6 



440 



6 



180 



20 



270 



10 



360 



2 



450 



17 



NUMBER OF TREES PER ACRE. 



Table 6 shows the average space in square feet controlled by trees 

 of various sizes in a representative stand of pure yeUow pine in cen- 

 tral Oregon.^ 



Table 6. — Space available to average trees of various sizes in pure yellow-pine forests. 



Basis, 45 trees. 



[Data taken near Mill Creek, Crook County.] 



Diam- 

 eter 

 class. 



Space 



available 



to each 



tree. 



Diam- 

 eter 

 class. 



Space 



available 



to each 



tree. 



Inches. 

 16 

 18 

 20 

 22 

 24 



Square 

 feet. 

 1,031 

 944 

 1,122 

 1,225 

 1,235 



iTwhes. 

 26 

 28 

 30 

 32 

 34 



Square 

 feet. 

 1,022 

 1,307 

 1,405 

 1,366 

 1,947 



By this table it is seen that each tree 16 inches in diameter occupies 

 in the virgin forest 1,031 square feet, allowing thereby only a possible 

 42 trees per acre; if they averaged 30 inches in diameter and required 

 1,405 square feet, there would be space for but 31 trees. But there 

 arc usually so many gaps in the yellow-pine forest that there are 

 c(jrisidcrably less than this possible theoretic number of trees. The 

 difference between the yeUow-pine and the Douglas-fir forests is 



' The area controlled by each tree is considered to be the irregular polygon about the tree whose comers 

 arc at half the distance to each neigli boring tree's base. 



