THE THEORY AND PRACTICE OF WORKING PLANS 205 



age classes. This modification is predicated on the area of 

 mature and overmature stands, i.e., those of or over the rotation 

 age, on the area of the next youngest age class, and the ratio 

 which the area of all stands less than half the rotation age 

 bears to the area of all stands more than half the rotation 

 age. Where there is an excess of mature stands more than 

 the normal area is cut over; where there is a deficit less is cut 

 over. 



Stands of the I period in which reproduction cuttings have 

 begun are entered with reduced areas in proportion to the per- 

 centage of the stand removed. A distribution of cutting areas 

 for the III, IV, V, and VI periods is obsolete; these stands and 

 their areas are merely entered in the column headed '' later 

 periods." In deciding on stands for the I and II period especial 

 regard is paid to age and thriftiness, volume and value, and, 

 in coniferous stands, on the formation of small cutting series. 



The period method, strictly speaking, is therefore no longer 

 used in Alsace-Lorraine. 



The long period of reproduction — often thirty to fifty years 

 — requires the assignment of stands for two periods — forty 

 years — in advance. The stands intended for cutting in the I 

 and II period are usually calipered; those of the II period, if 

 sufficiently uniform, may be estimated by means of sample 

 areas; thereto must be added the increment calculated to the 

 middle of each period. 



The volume of the allowed annual cut is one-twentieth of 

 the period volume calculated separately by species. In com- 

 munal forests one-fourth of the allowed cut is to be subtracted 

 (see above). 



In selection forest the cut is determined from the actual 

 increment and the relation of the actual to the normal growing 

 stock according to Heyer's formula (method No. 9). In order 

 to determine the actual growing stock, all the trees above 

 3,; inches (8 centimetres) in diameter are calipered. The 

 actual increment is determined by increment borings of trees 

 of various diameter classes; the normal growing stock according 



