106 THE THEORY AND PRACTICE OF WORKING PLANS 



13. BY AREA AND VOLUME.— FOR ENTIRE FOREST. METHODE 

 DU CONTROLE (GURNAUD). 



(a) Description of Method.* — This method, intended for 

 selection forest, was originated in France by M. Gurnaud. 

 It has been tried successfully in France and in Switzerland. 

 It consists in making successive measurements of the whole 

 forest, going over the whole area at short intervals of six to 

 ten years. The remeasurements are all made under absolutely 

 like conditions. The amount of increment is obtained by 

 deducting from the volume found at the last measurement 

 that of the preceding. A stand table is made. The stand is 

 divided roughly into three main diameter classes. The first 

 class includes ail trees below .30 meter in diameter (about 

 12 inches), the second, between .30 and .50 meter (approxi- 

 mately 12 to 20 inches), the third, over .50 m^eter (over 20 inches). 

 The cut is taken in per cent of the material on the area; based 

 on the vigor of growth at different ages. 



The method seeks the proportion of trees in the different 

 classes at each remeasurement. Growing stock and increment 

 must be determined by some measure common to both, to be 

 determined by the parties concerned. Muret advocates the 

 use of basal area for estimating the cut, rather than the estimate 

 of the actual cubic contents, since the cubic contents vary 

 in exact proportion with the basal area. 



One cannot establish a sustained annual yield by this method 

 until the beginning of the second period. The more frequently 

 inventories are taken, the more accurately can this yield be 

 determined. 



" The sustained and annual yield v/ill fix and will justify: " 

 I. Whether the cuttings ought to cover all the increment, more 

 than the increment, or less than the increment; 2. How and 



* .Adapted from M. Muret's article: " A Method of Yield Regulation, Methode 

 du Contr61e," translated by K. O. Ward, in Forestry Quarterly, Vol. XIII, No. i, 

 pp. 43-46. 



