10 IMPROVEMENT THINNING. 



ning is in progress ; although it would not, except in extraor- 

 dinary cases, pay to go into a stand for suppressed and dead 

 trees alone. And, on the general principle of clearing a 

 stand of all useless material which might add to the dissem- 

 ination of disease or increase the danger from fire, it is some- 

 times expedient to remove dead and suppressed trees, when 

 it can be done without extra cost, while thinning is being 

 done. On the other hand, it is sometimes desirable to re- 

 tain the suppressed trees, or a portion of them, in order to 

 keep the ground as well shaded as possible. 



Another method of determining in a rough way the ex- 

 tent to which a thinning is to be carried, is to estimate the 

 amount of wood standing on the area to be thinned, and to 

 remove approximately a certain percentage of the volume 

 of the stand. For instance, a given stand would run 25 

 cords per acre ; approximately, 3.75 cords per acre, or 15 

 per cent of the volume of the stand, would be removed in a 

 moderate thinning. 



Order of Preference. 



Certain species in a mixed stand are more desirable than 

 others. The relative desirability of species is dependent in 

 part on their market value, in part on the particular object 

 that the owner may have in view, and in part on habits of 

 growth and adaptability to the soil in which they may be. 

 The forester, therefore, finds it useful to list the species in 

 their proper order, bearing in mind the points mentioned 

 above. For want of a better name, this list may be called 

 the order of preference. 



For hard- wood stands in Massachusetts the order of pref- 

 erence would usually be as follows : chestnut, white ash, 

 hickory, white and red oak, sugar maple, yellow birch and 

 paper birch, whitewood, beech, elm, etc. In the case of 

 pine lands that are covered by a mixed growth, white pine 

 would head the list. 



To illustrate the use of such a list, let us suppose that a 

 white ash and a yellow birch tree are standing side by side, 

 and that the conditions are such that one should be removed. 

 All other things being equal, the choice rests solely on the 

 difference in species, and the birch would be removed and 



