IMPROVEMENT THINNING. 11 



the ash left to grow. The reason for giving white ash the 

 preference is that white ash stumpage sells for over twice as 

 much as yellow birch stumpage. 



Modifications in Practice. 



After the order of preference has been determined, 

 bearing in mind the market value of the several species in 

 mixture, their habits of growth and adaptability to the soil, 

 and the object that the owner may have in view, it must 

 be modified in many cases on account of defects in individual 

 trees. Using the same example cited a moment ago, but 

 supposing the yellow birch to be 'perfectly sound and the 

 white ash to have a serious defect, such as a large fire 

 scar at its base, then the yellow birch would be given 

 preference over the ash. 



A watchful eye should be kept for defects of other kinds, 

 as well as that just mentioned. The shape of the trunk, the 

 shape of the crown, the presence of indications of decay in- 

 side the trunk, and the general thriftiness of the tree, should 

 all be taken into consideration. 



The shape of the crown and its position in relation to sur- 

 rounding crowns are of especial importance, and should be 

 studied closely. The processes of respiration and assimila- 

 tion are carried on in the foliage which composes the tree's 

 crown. The crown of a tree is its lungs and stomach, so the 

 development and health of the crown are closely related to 

 the growth and health of the tree ; and when a decision is to 

 be made, the position, shape and health of the crown should 

 be given great weight. 



How the Work is Done. 



When a given stand is to be thinned, the forester first 

 ascertains the owner's needs and desires. If a forest work- 

 ing plan for the property has been prepared, he consults this, 

 to acquaint himself with the general policy to be followed in 

 dealing with the case under consideration. He next makes 

 a rapid reconnoissance of the stand. He is then ready to 

 mark the trees which are to be removed. 



