QUANTITY INCREMENT. 181 



Scotch pine, according to T. Kunze. 



Spruce, ,, Baur. 



Silver Fir, ,, ,, Lorey. 



Beech ,, ,, Baur. 



These factors refer to trees grown in fairly crowded woods. 



Similar figures for oak, based on the measurements of a 

 sufficiently large number of woods, are not yet available, but 

 until they have been obtained the form factors for beech may, 

 within reasonable limits, be used for oak grown in fully stocked 

 woods. In the case of oak' trees grown in coppice with 

 standards, form factors are out of the question. 



b. Increment of tuJiole Woods. 



The increment of a wood consists, during the first period of 

 life, of the full increment of the individual trees. As soon as 

 the trees close overhead, the extension of the crowns is inter- 

 fered with, followed by a decrease in the diameter increment. 

 As long as the degree of crowdedness is not too great, the 

 height growth is not reduced ; on the contrary, a moderate 

 degree of density of the leaf canopy encourages height growth. 

 Although, during this period, the individual tree has less 

 increment than it would have in a free position, the increment 

 of a fairly crowded wood can have, and generally has, a larger 

 increment per unit of area than an open wood, because the 

 total increment is equal to the mean increment per tree 

 multiplied by the number of trees. What degree of density of 

 a wood gives the maximum increment is a question which 

 awaits solution. In the meantime it must not be forgotten 

 that a fairly crowded condition encourages height growth, 

 decreases the tapering of the stems, and kills off the lowei 

 branches, thus producing more valuable trunks. 



While the loss of material is very small in trees grown in the 

 open, it becomes considerable in the case of fully stocked 

 woods. Not only do all the lower branches die off, but the 

 greater number of the trees, of which the wood originally con- 

 sisted, must be removed by degrees, because they are gradually 



