102 PRACTICAL FOKEST MANAGEMENT. 



This formula is more conservative than the formula Y=rr 



K A. 



given above, and is therefore preferable to adopt. Howard's 

 formula is obviously a special case of this general formula, where 



X= R, (if X=4 R>) the formula becomes 

 ' v 



Y = 7~^~iRi~ V V 



t B( 1-*- ) iK X i "~ *B 



Howard's formula has a great practical disadvantage of neces- 

 sitating alterations in the diameter or girth classes in making 

 enumerations of growing stock for every alteration of quality class 

 and of rotation, which is not feasible in actual practice. For the 

 above formula enumerations can be made in standard diameter 

 classes regardless of quality or rotation. It has been adopted for 

 the calculation of the yield in North Kheri forests, the calculations 

 for which are given below as an example. 



In utilising any of the other standard formulae such as Heyer, 

 Hufnagel or C. A. I., a considerable error will be introduced if 

 these formulae are applied to a partial growing stock V represent- 

 ing only trees over 8? diameter, and volume per tree up to 8" 

 diameter. This question has been discussed at length in an article 

 in the Indian Forester 42 and need not be repeated here, but in all 

 cases allowance must be made for the unmeasured growing stock 

 below 8" diameter. 

 Calculation of the yield for Working Circle (I) of North Eheri on 



Blanford's formula. 



An actual example of the calculation of the yield by this 

 modified formula for North Kheri is given below : 



" From the yield tables for sal it will be seen that the M. A. I. 

 for timber in the round culminates at 90 years for high 

 II Quality, that is including the usual 10 years of 

 establishment, and this corresponds with a mean crop 

 diameter of 17* '. This diameter is the average of the 

 crop, the best trees will be considerably larger, i.e., in 

 the 20" 24" diameter class. Owing to the unsoundness 



41 Indian Foreilcr, December. 1922. pages 626 to 636. 



