826 DETERMINATION AND REGULATION OF THE YIELD. 



For the rest, the method leaves a free hand to the forester, 

 who arranges the cuttings with due regard to sylvicultural 

 requirements and a proper succession of the different coupes. 



The numher of trees of the several size classes were 

 originally ascertained by counting, or measuring, them along 

 narrow strips, generally 100 feet broad, laid through the 

 forest along the line of march (called " linear valuation 

 surveys"). From the contents of these sample strips (or 

 plots), the contents of the blocks, or forest, were calculated. 

 The rate of increment was determined by counting the con- 

 centric rings on a sufficient number of stumps, thus ascer- 

 taining the average number of years, which a teak tree takes 

 to reach the limits of the several size classes. 



The original method was subsequently further elaborated, 

 so that the sample plots are now systematically arranged over 

 the area, with the view of obtaining correct data for the 

 number of trees in the several blocks of the forest. The 

 cuttings, based on these data, were also localised : in other 

 words, an area check was added to the calculated yield, so as 

 to guard against over or under cutting. 



The method does not claim to be theoretically quite correct, 

 but it is correct enough, wherever large areas have to be dealt 

 with in a short time. It works expeditiously, and, if judiciously 

 applied, prevents a deterioration of the forest. Had it not 

 been for this method, the valuable teak forests of Lower 

 Burma might have been exhausted, before their sustained yield 

 capacity had been ascertained. It is a method to be strongly 

 recommended for adoption in countries, where systematic forest 

 administration is in its earlier stages, and where only a limited 

 number of species are as yet of commercial value. 



D. Regiilation of the Yield according to Increment and 

 Growing Stock, combined with the Allotment of 

 Areas to the several Periods of a Rotation. 



This method was originally elaborated by Carl Heyer, and 

 classed under C, as it rested on the xlustrian method. 



