SECTION VIII— GENERAL GROWTH STUDIES 



Explanation. — Studies in the growth of trees are made chiefly for the pur- 

 pose of determining the number of years required for trees to become mer- 

 chantable in size, for the prediction of future yield in volume, as a basis for 

 silvicultural practice and as steps in organizing forests for continuous timber 

 production. Studies are made on growth in diameter, height, basal area, 

 and volume. These may be made for individual trees or as an average for 

 small groups or even for extensive areas. As a basis for predicting the vol- 

 ume growth of stands studies are usually made in terms per acre and are 

 then known as yield studies. Growth in diameter and height form the 

 direct basis for the volume and yield studies. 



In many studies it is necessary to distinguish growth with reference to 

 time. Thus we have (C. A. G.) Current Annual Growth, that for any one 

 specific year; (M. A. G.) Mean Annual Growth, the average annual rate of 

 growth during the life of the tree; the (P. G.) Periodic Growth, the rate for 

 any specific period of years. In some problems, particularly the prediction 

 of growth in the future, we have growth per cent, which is determined by 

 means of a simple interest formula that shows the per cent of increase in 

 relation to the present size of the tree or stand. 



Prerequisite Study. — Before taking up the exercises included in this section 

 the student should review the general method of collecting data for growth 

 studies, Problem 7. 



Caution. — In all growth studies it should be remembered that the number of 

 measurements required both as to kind and quantity will vary with the 

 specific problem to be solved. Since separate studies must be made for 

 trees growing under different conditions, a completed curve or table will 

 have no value unless it is labeled with all the conditions of growth. This is 

 even more important in growth studies than in volume studies. All of the 

 points enumerated in the outline below should be considered in the title or 

 label for each distinct growth study, though not all need be included because 

 some conditions may be wholly obvious from some others already stated. 

 For example, if a study had been made of the growth of Virgin Yellow Pine 

 in Eastern Oregon, it would be practically obvious that it represents the 

 growth in an uneven-aged stand. 



Points to he Considered in Connection with Title.* 



1. The general problem. 



2. Species. 



* Those italicized should appear in the title of each problem. 

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