PLOTS FOR MEASUREMENT OF CURRENT GROWTH 



443 



TABLE LXVII 

 Areas Remaining Stocked on Cut-over Lands 



340. Permanent Sample Plots for Measurement of Current Growth. 



The best method of measuring the current growth of a stand is by means 

 of permanent sample plots, established in stands which are typical of 

 the conditions to be studied, and re-measured at intervals of from five 

 to ten years. Methods of establishing and measuring such plots are 

 described in § 243. In this way, just as for yield tables the actual net 

 results of all factors which affect the current growth of the stand as a 

 whole, such as wind, insects, disease, suppression, or increased growth, 

 are measured, rather than either compared or predicted. The only 

 precautions to observe on re-measurement of plots are that the diameters 

 and heights of the trees must be taken in successive measurements in 

 such a way as to give exact comparisons, whose difference indicates 

 growth rather than discrepancies in re-measurements. 



Krauch has pointed out that the height of trees should be measured 

 on such plots from the same position or point at each measurement, 

 to avoid discrepancy due to the departure of the tree from the per- 

 pendicular (§ 199). The diameter tape insures consistency in re-measure- 

 ment of diameters (§ 190). The same volume table should be used in 

 calculating successive volumes for trees of each size class. These pre- 

 cautions insure the isolation of the current growth in successive measure- 

 ments. 



341. Measurement of Increment of Immature Stands as Part of 

 the Total Increment of a Forest or Period. The increment of a forest 

 or large area, just as in the case of a single stand, may be expressed as 

 the total growth over a definite period, or yield, the average annual 

 growth or mean for this period, or the actual volume laid on each year 



