STEM ANALYSES. 

 By John Bentlky, Jr. 



From the experience gained in instructing several classes in 

 the subject of volume growth in individual trees, it is apparent 

 that the method described in the text books in use in this country 

 is difficult of comprehension by the average student of forest 

 mensuration. As a general rule, the problems of height growth 

 and diameter growth are handled by the majority of students 

 quite readily, but they frequently have difficulty in mastering the 

 subject of volume growth as exemplified in "stem analyses." In 

 searching for the cause of this trouble, it appears that much of 

 it arises from the form in which stem analyses are usually re- 

 corded in this country; and the object of this discussion is to 

 recommend a more logical tabulation of the data usually included 

 on a stem analysis blank. 



It will be remembered that the blanks provided for stem 

 analysis by the Forest Service (Form 334, "Tree Measurements") 

 include a page in which the measurements on each cross-section 

 of the tree are recorded in columns numbered i, 2, 3, 4, 5, etc., 

 (which represent decades), the values showing the "distance on 

 average radius from heart to each tenth ring." If, as is gener- 

 ally the case, there is not an even multiple of ten annual rings 

 on the section, the measurement of the odd years is recorded 

 under column i, (since the measurements begin with the inner- 

 most period and proceed outward), and from that point on, the 

 difference between the values in any two adjacent columns repre- 

 sents a decade's growth. So far, so good ; but when the measure- 

 ments for the second and subsequent cross-cuts are recorded, the 

 measurements in each case are tabulated beginning in column i 

 again; and since there is almost always at least ten years differ- 

 ence in the total ages of successive cross-cuts, and sometimes 

 twenty, or more, the measurement for the last, or current decade, 

 falls, not in the column for the corresponding decade on the pre- 

 vious cross-cut, but in a column to the left. Glancing down the 

 numbered columns, then, we find a series of measurements each 

 one of which represents a diflferent decade in the tree's life- 



