336 



DETERMINING THE AGE OF STANDS 



The increment borer (§ 277) may be used to determine the age 

 of standing trees at breast height or at any section accessible, provided 

 the diameter is not too great and the position of the core of the tree 

 can be found by the instrument. This method is used with such 

 species as spruce. 



257. Correction for Age of Seedling below Stump Height. The 

 number of rings in any cross section of a tree will indicate only the age 

 of the tree at that cross section and not the total age. No rings can 

 be formed at a given height above the ground until the tree reaches 

 that height. The age of each cross section made in sectioning a tree 

 will be less than that of the section below by just the number of years 

 occupied in height growth between the two points. Although the 

 total age of a tree can be determined theoretically by taking a section 

 even with the surface of the ground, this is seldom if ever done. The 

 rings are counted at the stump, which gives the age of the tree minus 

 the time which it took the seedling to reach this height. To get the 

 true age of any tree, seedling ages based on height must be added to 

 ring counts taken at stump heights. By cutting at the ground and 

 counting the rings on a sufficient number of dominant seedlings which 

 are sure to survive and therefore represent the average height growth 

 of mature timber when at this age, a table is constructed showing the 

 relation between the age of seedlings and different stump heights. In 

 rapidly growing trees this makes from one to five years' difference 

 in the total age, but with some species which have a long juvenile period, 

 as much as twenty years may be required for a seedling to grow 2 feet 

 in height. This is true of certain Western conifers. Hardwood sprouts 

 on the other hand attain stump height in the first year. 



TABLE L 



Height of Seedlings at Different Ages, Western Yellow Pine, Colfax Co., 

 New Mexico 



* Forest Tables— Western YeUow Pine. Circular 127, U. S. Forest Service, 1908. 



