YIELD TA1JLICS 55 



must depend on the judgment of the man in charge of the work. 

 In ordinary wildwoods the selection of stands for yield table work 

 is not always easy, in some cases impracticable. 



It is much easier in conifers than hard woods, and generally 

 easier for young stands than old. Even in pure stands, the variation 

 in age, the irregular condition of the trees, and the question of 

 stocking, complicate matters. The question whether a stand is fully 

 stocked is not always easy to answer. The same stand of Pine 100 

 years old, fully slocked, and in excellent condition, might have 20% 

 less trees, and yet 10% more volume if it had been heavily thinned 

 at the right time. Here then, neither the number, nor the volume 

 fully decide the case. This whole matter must remain debatable 

 until new stands have grown up under the care of man, and accept- 

 able standards established. Generally a fully stocked stand must 

 be accepted to be one on which as many good trees exist as have 

 fair growing space under the given conditions of species and site.* 

 Since the Yield tables as above indicated deal with perfect stands, 

 they have also been called Normal Yield Tables. In using them it 

 is necessary to make allowances, for it is utterly impossible to 

 develop all the stands of a forest through an 80 or 100 year Rota- 

 tion without disturbance or accidents. In the Bavarian Instructions 

 a reduction of 20% for Spruce and 1020% for Beech is suggested. 



Of late, Yield tables have been prepared giving the volumes 

 over large areas as actually found. While these tables are of value 

 as indicating actual conditions of the forest, their use in predicting 

 the growth of timber on the particular site is rather uncertain, since 

 the conditions of the wild woods are commonly too irregular and 

 accidental to serve as criterion of what can be done in forestry. On 

 the other hand the best 10% (or less) of all the acres of 

 mature stuff calipered may very well be used in setting a provisional 

 Normal Yield for mature timber and thus also serve to determine 



* This matter of Normality or what constitutes a fully stocked Stand 

 ("Vollbestands factor") and 'how a stand is to be gauged, is still a debated 

 point. For purposes of volume-calculations the prevailing German plan puts : 



-Degree of Stocking =^ Area of Cross Section of trees of Stand divided 

 by Normal Area of Cross Section. 



Sec also: Martin, "Forsteinrichtung" and Schilling's Comment in "Zeit- 

 schrift fiir Forst und Jagdwessen," 1911, p. 582, and particularly Fricke, 

 "Standorts und Bestandesbeschreibung" in same paper, 1911, p. 227. 



