CHAPTER XXIII 

 DETERMINING THE AGE OF STANDS 



256. Determining the Age of Trees from Annual Rings on the Stimip. 



The age of standing timber can only be determined from the ages of 

 the trees which compose the stands. The age of a tree is the period 

 elapsing from the germination of the seed or origin of the sprout to the 

 present year. A record of the number of years of growth in a tree is 

 made by the formation of the annual rings in which the light spring 

 wood is sharply differentiated in color and texture from the heavier 

 and darker band of summer wood of the year preceding. The count- 

 ing of these annual rings determines the age of the tree. 



It is not always possible or easy to make this determination. Unless 

 the growth of a tree is marked by annual seasonal changes, there are 

 no annual rings to distinguish. This is true of most species of tropical 

 woods, except those growing in regions marked by an annual cessation 

 of growth due to annual recurrence of dry seasons. In some species 

 of hardwoods there is such a slight difference between the texture of 

 the spring and summer wood that the annual rings can be detected 

 only with difficulty and by the aid of coloring matter and magnifying 

 glass. This is true of such trees as basswood, hard maple and sweet 

 gum. Many trees on dry sites grow so slowly that the annual rings 

 are almost impossible to distinguish except by a glass. In counting 

 rings it is usually necessary to smooth off the surface with a sharp knife 

 or chisel in order to bring out the contrast. 



Where growth is affected by severe droughts, and sometimes where 

 the trees are defoliated by insect attacks and later acquire new foliage, 

 a false ring may be formed, giving two rings in a single year which 

 would lead to an exaggeration in the age of the tree. This was found 

 to be the case with Rocky Mountain juniper on dry sites. False 

 rings may be detected if sufficient care is used, since they seldom form 

 a complete circle, but are present on only a portion of the circum- 

 ference and are therefore imperfect. 



The last annual ring of wood is not completed until after the growth 

 for the year is finished. It must be distinguished from the ring of 

 new bark laid down in the same season. The first two or three rings ' 

 on some seedlings are difficult to distinguish. 



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