56 CIRCULAR 3 3 3, TT. S. DEPARTMENT OE AGRICULTURE 



REMEASUREMENTS 



The proper interval between reineasurements cannot be exactly 

 decided upon at the time of plot establishment, for it depends on 

 the rate of change on the plot. Obviously, the more rapidly a 

 stand grows the more often it should be remeasured. 



The nature of the experiment determines how closely growth 

 and other changes should be followed. Since significant changes 

 take place rapidly during the reproduction stage, in methods-of- 

 cutting studies it is common practice to examine reproduction sub- 

 plots annually, at least for the first few years. Intensive studies 

 of reproduction sometimes call for examining the subplots each 

 week or every few days. 



For stands beyond the reproduction stage, a 5-year interval be- 

 tween reineasurements is generally satisfactory. If growth is ex- 

 tremely slow, as on poor sites and in very old stands, the interval 

 may be lengthened to as much as 10 years. TThere growth is ex- 

 ceedingly rapid, a 3-year remeasurement interval may be appropriate. 



Diameters are measured at each remeasurement period. 



Heights, except in thriftily growing stands, usually need be meas- 

 ured only at alternate remeasurement periods. 



Tree-description data, such as data on size, shape, and confor- 

 mation of crown, are ordinarily taken not oftener than every 10 

 years, and on mature trees may be taken at even longer intervals; 

 in some studies in which changes occur rapidly, as in young thrifty 

 stands and in stands of fast-growing species, it is necessary to 

 take these data more often. 



On plots that are known to be liable to disturbance, measure- 

 ments should be made at shorter intervals. 



Mortality is of course recorded, and trees that have died since 

 the last preceding measurement should be permanently blazed, at 

 each remeasurement. 



T\ Tien height data are taken on a height-diameter-curve basis, in 

 remeasurement it is well to run strips through the plot in such a 

 manner as to include a part of the strip on which height measure- 

 ments were previously made. This helps to keep the distribution of 

 height measurements well balanced and truly representative of the 

 stand. In order to determine whether changes in mechantable 

 height and in clear length are such as to call for a complete remeas- 

 urement. reineasurements should be made on representative trees. 



Reineasurements should be made at the same time of year that 

 the original data were taken. Uniformity in this regard has a 

 particularly important bearing on the significance of records of 

 seedling survival. If reineasurements cannot be made at the same 

 time of year as the original measurements, they should preferably 

 be taken"during the period of vegetative rest. 



The first duty of those remeasuring plots is to become familiar 

 with the work previously done on the plots and with the technic 

 used. They should carefully review the records and study the plan 

 so as to appreciate fully the intent behind the experiment and fully 

 understand the method of procedure. 



The methods used in the original measurement should be fol- 

 lowed in all reineasurements, and so far as possible the same in- 

 struments or types of instruments should be used. Reineasurements 



