55 



3. method of partial enumeration.'- Partial enumeration sur- 

 reys may be carried out («) by the method of sample plots 

 that is, by counting the stock on sample plots of known 

 extent ; or (i) by the linear method, that is, by enumerating 

 the trees on lines of known width run through the crop. 



Where the conditions are such that the method of survey 

 by sample plots is justifiable, separate plots should be marked 

 off in each distinct type of growth. They should be chosen 

 so as to represent fairly t he average conditions of the crop 

 or particular type of growth of which a pattern is taken. 



In other cases it may be more convenient to use sample 

 lines taken at regular intervals through the forest. "Where 

 the crops are mixed r.nd variable, the position of the lines 

 should be traced on the map on which the limits of the 

 different types of forest are shown, and the results should be 

 calculated separately for each crop through which the lines 

 run. The width of the lines should be fixed so as to be 

 convenient for purposes of calculation. 



Thus a line 1 ohain broad would represent O'l aore per chain-length ; and, if the 

 type nf forest through which the line led tras fonad to measure, say, 6 acres, while 

 the length of line was, say, 9 chains, the number of trees oould at once be found as 

 follows ;.— 



number of trees in crop of- 6 acres 6 acres. 



number counted on 9 chains of line 0'9 acres. 



The following rules should also be observed in the case of 

 sample plots. Their application to linear surveys need not 

 be discussed : — 



(1) No sample plot should be selected on the edge of a 



crop ; for a true average will seldom be found 

 there. 



(2) On slopes presenting a wide range of elevation, or 



in crops offering a great variety of aspects and 

 soils, several sample plots judiciously distributed 

 should be selected. 



(3) The form of the plots should be regular : in gene- 



ral, the best shape is ttiat of a long rectangle. 



(i) The aggregate area of the sample plots should not 

 be less tl»an 5 per cent, of the total area of the 

 crop or type of growth of which they jare chos6n 

 as the pattern. 



(5) In mature crops no sample plot should usually be 

 le.ss than from 3 to 5 acres in extent ; and in no 

 case should the area be less than one acre» 

 except, perhaps, in young uniform crops. 



