Z CIECULAK 3 3 3, U.S. DEPARTMENT OF AGRICULTURE 



species, but these apply to only a few of our many commercial forest 

 types. Further, much of this information deals only with certain 

 stages in the life history of the forest ; thus for some of the pines we 

 know how to achieve a certain degree of success in reproducing stands 

 naturally, but know little or nothing of the cultural methods needed 

 for success in bringing the stands to maturity. 



European experience gives us little help. Most of the forestry 

 methods earliest used in North America were borrowed from Europe 

 almost without change. Some of these, although highly satisfactory 

 in Europe, failed here. Our species, our soils, our climate, our eco- 

 nomic conditions are so radically different from those of European 

 countries that what holds true on one continent does not necessarily 

 hold true on the other. 



Information needed as a basis for forest management can be 

 acquired in several ways. The trial and error method takes much 

 time and is costly. Faced by the fact that our forest supplies are 

 dwindling and that our growing stock is already inadequate, we can- 

 not justifiably place our dependence upon this method. The empirical 

 investigative method also is unsatisfactory. Its results, while indic- 

 ative, are inconclusive. Too often, after long and involved study the 

 investigator finds himself not far from where he started. Here again, 

 too much time is required. The research method alone appears satis- 

 factory. It holds promise of results within the shortest possible 

 period, and of results that will stand the test of time. Also, in the 

 long run it is the cheapest method. In the research method the prob- 

 lem is broken down and its parts studied separately, replications are 

 made to eliminate the influence of accident, and controls are pro- 

 vided to insure definite comparative results. 



The sample-plot method has been found to be the most effective 

 way of studying the growth and behavior of forest stands. A plot 

 can be small enough to permit rather careful observation of develop- 

 ments and at the same time large enough to be truly representative 

 of the forest. 



To obtain really exact comparative data would require the impos- 

 sible procedure of comparing conditions on a given plot after a given 

 treatment with conditions on the same plot, in the same period, after 

 no treatment. The sample-plot method calls for a comparison of con- 

 ditions on a given plot after treatment with contemporary conditions 

 on an untreated plot which it closely resembled before treatment in 

 the characteristics which the experiment involves. This method is 

 adequate if the plots are, in fact, random samples of the experimental 

 area, but is incorrectly applied if treatment is allocated to system- 

 atically arranged plots or to areas chosen arbitrarily. When only 

 1 of 2 comparable plots is to be treated, for example, the choice of 

 the area to be treated should be made absolutely by chance, as by the 

 toss of a coin. This system of sampling is based on the assumption 

 that differences in the unknown factors of site are unrelated to the 

 plot arrangement. 



In some fields of scientific endeavor it is a relatively simple matter 

 to obtain basic data under carefully controlled conditions, and to 

 repeat an experiment at will. Even in dealing with some kinds 

 of plant material it is possible to keep the factors of an experiment 



