FIXTURE VOLUME IX MATURE STANDS 79 



2. Compare the results of this exercise with tliose derived by the three 



different methods of the previous exercise, and conmient on the 

 efficiency of Pressler's formula. 



3. What is Pressler's formula for mature or nearly mature stands? 



PROBLEM 38. (Field.) The Prediction of Future Volume in Mature 

 Stands BY Means of Growth Per Cent. 



Explanation. — Schneider's formula is applicable only to mature trees. It 

 has been found to be one of the most reliable and easily used formulae. 



Illustration. — To determine what the volume of a stand will be 10 years 

 hence by means of Schneider's formula. 



Explanation. — Schneider's formula uses the periodic annual growth as 

 determined by the last inch radius as interest and the average of the volume 

 one year ago and one year hence as principle. He assumes there will be no 

 change in height or form factor. 



DiRECTION.s: 



A. Formula. 



400 

 nD 

 where j) = growth per cent ; 



D = present D.B.H. (outside bark) ; 



n = number of rings in the last inch radius. 



B. Method of Procedure. 



1. Lay off a sample area of ^ acre in an old stand of timber. (If the 



trees are very large or scattered use 1 acre.) 



2. Determine the average tree by means of the Mean Sample Tree 



Method. 



3. Make the necessary measurements on three trees. Average and apply 



in the formula for growi:h per cent. 



4. By means of the growth per cent calculate the volume of the tract 



(40 acres) 10 years hence. 



C. Discussion. 



1. Show step by step how your results were derived. 



2. Show by means of the mathematical derivation of Schneider's formula 



why it is not applicable to immature trees. 



