&4 



by the volumetric method. In such cases the analysis of the 

 crop is not complete until the enumeratioa has been oarri§i 

 out. 



Ihe material in the standing crop may be ascertained 

 accurately by complete survey, that is to say, by counting 

 and measuring the individual trees over the whole area. Or 

 it may be estimated, more or less accurately as desired, hy 

 partial enumerations, that is, by counting the stock on 

 sample plots of know.n extent or on lines oi known width audi 

 length run through the crop ;-after which, by means of simple 

 proportion, the ' number' of trees in the whole area can be 

 deduced. 



3. Choice of a method.— The circumstances of each case 

 must decide which of these methods should be adopted. 

 Obviously the most correct is to count and measure each tree 

 in the crop. But this involves the expenditure of si) much 

 time apd labour that, except where a Very accurate plan is- 

 required, and is justified by the high revenue expected from 

 the forest, it is generally best not to employ it. It may, 

 however, suitably be used when, as frequently happens, only 

 one or two species irregularly distributed in a mixed crop 

 are saleable, and when the plan is to provide for the work- 

 ing of those species only. In such cases the cost is not unduly 

 high, and the results obtained from countings over sample 

 areas are unsatisfactory. 



The chief considerations which should determine the 

 method to be adopted whether a complete or a partial enu- 

 meration survey, are (a) the purpose of the survey and the 

 degree of accuracy demanded in the plan, and (6) the nature 

 of the crop. Thus, it may be only necessary lo ascertain 

 the average production per acre, so as to calculate the yield, 

 in the manner described in the selection method. It is 

 usually unprofitable to attempt to calculate the material on_ 

 the ground with extreme accuracy ; and, in any case, even 

 complete enumeration and cubing of each individual tree 

 might not ensure accuracy. 



On the other hand, a partial enumeration survey by 

 samjple plots should be avoided in the case of very irregular 

 and open crops, or in crops containing only scattered trees^ 

 for enumeration as in the case of selection -worked areas in 

 which only one or two species sparsely distributed in a mixed 

 crop are exploitable. Again, the method is unsuited to the 

 case of very small areas ; as there would be difficulty in 

 Selecting plots representative of the whole. 



