SAMPLE PLOTS IN SILVICULTURAL RESEARCH 61 



erly regarded as inferior suddenly becomes valuable. Maintenance 

 of such plots requires time; compilation of the records probably 

 requires more. The question arises as to whether plots affected by 

 such changes should be dropped and forgotten or whether collection 

 and compilation of data from them should continue. 



Occasionally, also, an investigator is confronted by the fact that 

 certain plots established many years previously are too small, were 

 not comparable, or were abnormal in composition, age, site, or stand. 

 In such cases there may be some doubt as to whether the plots should 

 be continued and, if so, for how long. 



Despite precautions, accidents happen to sample plots rather fre- 

 quently. An electric transmission line may be put through one 

 corner of a plot; a band of sheep may be bedded down in an en- 

 closed plot area ; woodcutters may make a hole in the stand ; a storm 

 may break or uproot a large percentage of the stand; fire may de- 

 stroy part of the reproduction; insects may suddenly become epi- 

 demic ; or disease may break out. 



No hard and fast rule can be given as to whether, in such cir- 

 cumstances, plots should be abandoned or retained. Obviously, more 

 than temporary considerations should be taken into account and no 

 plot should be abandoned unless it is so far awry that further effort 

 is certain to fail of a reasonable return. When plots are found to 

 be too small, otherwise inadequate, or noncomparable, little can be 

 done to remedy the situation. Such plots should be dropped unless 

 they have some intrinsic merit that will make them valuable in the 

 future. In many instances, however, when the value of plots has 

 been destroyed so far as their original purpose was concerned the 

 plots have retained value from other points of view, sometimes be- 

 cause of developments unforeseen at the time when they were 

 established. 



Foremost of the considerations to be taken into account is the fact 

 that all plots increase in value as they grow older, regardless of 

 what they show, because thus far we have in North America no 

 authentic data on forest growth and mortality over long periods. 

 Such data are needed in growth predictions. Even if the original 

 purpose must be abandoned or if the plots are not as they should be 

 to meet a specific need, often the value of prospective data is suffi- 

 cient to warrant further work. 



Second, plot records systematically built up over many years can 

 be expected to tell us much about the reactions of trees to their 

 environment. Reliable data on such reactions are now nonexistent 

 for most of our forest tree species. Such information is essential 

 to putting American silviculture on a sound basis. 



When the applicability of plot data is changed through changes 

 in utilization practices, instead of abandoning the existing plots it 

 may be desirable to establish supplemental plots. For this reason 

 it is well at the initiation of a plot series to lay out a larger number 

 of plots than that the need of which is foreseen. 



When the value of a plot is in question it may be advisable to con- 

 tinue plot measurements on a reduced scale only. Measurements 

 may be made at intervals longer than the period originally prescribed, 

 or irregularly rather than regularly. Tags can go longer without 

 pulling, or paint can weather still more before being freshened. 



