ROTATIONS AND CUTTING CYCLES 229 



One of the chief difficulties in computing rotations, and especially 

 financial rotations, is that the forester must use present statistics or the 

 trend of present statistics for calculations which pretend to answer 

 management problems on the basis of unknown or roughly approxi- 

 mated conditions a half century or a century hence obviously im- 

 possible to fathom. But the proper regulation viewpoint is that the 

 problem should be solved for the present on the basis of the best avail- 

 able data on the assumption that when the working plan is systemati- 

 cally revised these calculations will be recomputed and brought up to 

 date. The fact that a revised and altered answer to the rotation prob- 

 lem will be certain is no reason for not doing our best with available 

 statistics. As a matter of policy it is safe to estimate future conditions 

 based on the trend of economic conditions, rather than to follow blindly 

 present stumpage prices, present cost values, present current interest 

 rates, and market requirements for forest products. The best regulation 

 implies some attempt to fathom the future. We know from past history 

 that forest conditions change; therefore to follow blindly present condi- 

 tions we arrive at the least accurate predictions. There is a middle 

 ground between following to-day's data on the one hand and on the 

 other of making unwarranted guesses at the future. Moreover, we must 

 realize that our calculations are at best approximations and therefore 

 the minutia may often be omitted with profit and propriety. 



Efficient thinnings not only enable the forest to grow timber of a 

 specified size in fewer years, but they increase seed production and 

 promote earlier seed crops, they decrease the date of the culmination 

 of mean annual growth, and, as Endres puts it, "The greatest benefit 

 is felt where the highest soil rent is maintained. It is recalled that 

 large, early yields produce large soil rent and vice versa ... a stand 

 that has been thinned up to the nth year will have higher value than 

 one that has not been thinned." 



In intensive regulation, as for example in parts of New England, the 

 forester must, in theory, distinguish between the rotation for a particular 

 stand and the rotation for a working group which is composed of a number 

 of stands of varying quality, but in the West, in northern Arizona for 

 example, a rough general average rotation for even an entire region 

 will usually be a sufficiently close approximation for conditions preva- 

 lent while National Forests are being organized. Even in a selection 

 forest such as Chamonix (see p. 252) the French prescribe one technical 

 rotation for Norway spruce and larch based on a rough proportion of 

 the length of time it takes to grow the two species weighted according 

 to the aggregate volume present. This rightly emphasized the futility 

 of minute mathematical calculations for the solution of a problem which 

 demands only an approximate answer. 



