THE PACIFIC NORTHWEST 55 



4 l /2 feet a year. It will not give equal return for the soil, 

 moisture and light it monopolizes during these 25 years. At 

 the same time, probahly there are young trees nearby which 

 hitherto have averaged below the maximum, but if released 

 from its competition will forge ahead for a period at the end 

 of which they will give a greater annual return than if cut 

 at present. It would be as bad economy to cut these today 

 as to spare the over-mature tree. In short, the production of 

 the forest is not only sustained, but actually increased, by 

 removing the oldest trees at just the proper time; and is 

 decreased by taking out young trees either not yet at the 

 natural age of greatest mean annual increment or capable of 

 artificial stimulation by thinning. 



By studying the relation of age to production in the par- 

 ticular locality, the proportion of different age classes, and 

 also finding the approximate average diameter which corre- 

 sponds to the age at which he desires to cut, the professional 

 forester can make a very accurate selection of the trees which 

 can be removed to best advantage at present and also fix the 

 time and yield of the next cutting. Fortunately, however, 

 commercial and silvicultural considerations accidentally co- 

 incide so nearly under average yellow pine conditions as to 

 make certain rough rules which can be laid clown entirely con- 

 sistent with logging methods now in practice. Diameter is 

 far from exact indication of age, for the location of the forest 

 and the situation of the individual tree, especially as it af- 

 fects the relation between height and diameter growth, are 

 potent factors, but as a rule merchantability for saw-material 

 is not far from maturity. 



In a great majority of cases the approximate minimum 

 diameter for cutting which would be fixed by a forester would 

 be someAvhere between 16 and 30 inches, but say it were 18 

 inches, for example, it would not arbitrarily apply throughout 

 the stand. Most trees with yellow, smooth bark and small 

 heavy-limbed tops, perhaps partially dead, are mature regard- 

 less of their size. If small, they have been crowded or stunted 

 and may as well be cut. Trees with large, healthy crowns 



