ANNUAL WHORLS OF BRANCHES AS AN INDICATION OF AGE 337 



The juvenile period for conifer seedlings is, as a rule, longer than 

 that for hardwoods, though there are exceptions. Stump height may 

 be separated into 6-inch height classes for determining the number of 

 years to add for seedling heights to get total age of tree. 



258. Annual Whorls of Branches as an Indication of Age. There 

 is another method, of very limited application, for determining the age 

 of standing trees. This is applied to conifers and is confined to those 

 species which form but one whorl of branches per year. Species like 

 jack pine or loblolly pine, which form two or more whorls per year, 

 cannot be judged in this manner. The approximate age of the tree 

 and stand is obtained by counting the number of whorls. This record 

 holds good only when the branches or dead stubs remain visible and 

 when the height growth continues normal. The record is lost if all 

 traces of the lower whorls are obliterated. If this is only for a height 

 of from 5 to 10 feet, the average age of trees of this height may be 

 obtained from a study of seedling heights and used to supplement 

 the remaining count. When the height growth of the tree has reached 

 its maximum, a new whorl of branches is no longer formed annually, 

 but the leader, as well as the branches, extends its growth by prolonging 

 a single shoot. 



The ages of seedlings of many species may be determined by count- 

 ing whorls of branches, or terminal bud scars if the whorls are not all 

 there. In such cases it is not necessary to cut the seedlings and count 

 rings. The bud scars are distinct for many years on species such as 

 Douglas fir, Alpine fir, and others. 



259. Definition of Even-aged versus Many-aged Stands. The age 

 of trees determines the age of stands. But unless it is known that 

 the entire stand originated in a single year, as is the case with sprouts 

 or with some species of conifers, such as jack pine or loblolly pine 

 on burns, there will be a variation in age due to natural seeding for 

 a period of reproduction which may extend to fifteen or twenty years. 

 Stands are termed even-aged if their crowns form practically a single 

 canopy or one-storied forest, which is true when the period of repro- 

 duction does not exceed approximately one-fifth of the rotation or 

 period required to reach full maturity. Where the crown cover of 

 stands of mixed ages varies so greatly that it is composed of different 

 stories, and must be separated into component age classes whose aver- 

 age age is separately distinguished, the stand is termed many-aged 

 or in some cases all-aged. The separation of such stand may be either 

 directly into age groups, or into groups based on size or diameter with 

 a limited range of age, whose average age is sought. 



260. Average Age. Definition and Determination. The average 

 age of a group of trees showing a range of ages nuist be that age which 



