THE USES OF VOLUME AND YIELD TABLES IN FOREST MANAGEMENT. 59 



standards, (6) selection forest, (c) simple coppice, but in this last 

 case it will for all practical purposes probably be found sufficiently 

 accurate from 30 to 60 years of age, if we ignore entirely the 

 establishment period. It may at least be utilized for simple 

 coppice, until a coppice yield table has been prepared. In 

 considering rotations of sal forests, reference should be made to 

 the remarks on this head in thejpublished fal yield table. 



The same principles will apply in using the data available 

 in chir and deodar yield tables (when these are published) in 

 determining the rotation. 



In the present state of our forests however a careful distinc- 

 tion must be made between " rotation " and " conversion period. " 

 This distinction can best be illustrated by the example of the pine 

 forests of Kumaun. Here we find enormous areas of forest which 

 are very openly stocked (often from 6 to 12 trees per acre only) 

 and very overmature. In some cases 75 per cent, of the whole forest 

 is in this state, and it is obvious that the existing crop of the 

 forest will not survive for the period of a rotation. The quicker 

 we can convert these poorly stocked and deteriorating areas into 

 well stocked and vigorously growing crops, the better it will be. 

 But if we converted them so rapidly that at the end of the 

 conversion period there were only young pole and sapling crops,, 

 there would be a long hiatus before we could again have commercial 

 fellings for large timber. It is evident, therefore, that the conver- 

 sion period should be as short as possible, subject to the qualifi- 

 cation that at the end of the conversion period the oldest crops 

 will give trees of utilizable size. If for example the yield table 

 indicates a rotation of 120 years as the most suitable corresponding 

 perhaps to crops of 22 inches diameter, then it may be not only 

 justifiable but definitely advisable to adopt, for conversion to uniform 

 crops, a period of, say, 90 or 100 years, giving at the end of the 

 conversion period crops of 18 inches or 19 inches diameter. Although 

 the output per tree will be smaller than from the existing trees, yet 

 the fact that we may hope for 50 or 60 trees per acre in place of- 



