CHAP, ix.] Tending of Woods 189 



equal strength with which the individual struggle for supremacy 

 is waged on soils of indifferent quality, the growing- space per 

 stem is, up to the sixtieth to eightieth year, often considerably 

 less than on better soils, although in the case of the Scots Pine 

 this difference is less marked than in any other species. The 

 practical lesson thereby conveyed is that, on soils just of or 

 below the average in quality, both financial and purely sylvi- 

 cultural considerations point to the advisability of stimulating, 

 by means of early, oft-repeated, and moderate thinnings, the 

 development of all individuals which it is desired to retain. 

 Thin early, often, and moderately is the golden rule of tending 

 woodlands. Anything approaching interruption of the canopy 

 during the period of most active growth in height must of 

 necessity lead to a further development of the crown at the 

 expense of the length and cleanness of the bole ; and this will 

 consequently tend towards a diminished technical and monetary 

 value of the timber produced. 



Between the two extremes of overcrowding and of free 

 individual growing-space there must be in every kind of 

 crop a happy medial point or a normal density of canopy, at 

 which the quantity and the quality of the crop attain their com- 

 bined maximum. To show the practical effect which thinning 

 has on the increment of the basal area of the individual stems left 

 forming the crop, the following example may be given. In two 

 different parts of an extensive forest three areas were selected 

 on soil of similar nature and quality, and thinnings were carried 

 out on equal areas in the following degrees : 



I. Slight, only dead and dying poles being removed. 

 II. Moderate, all suppressed poles being removed. 

 III. Heavy, all dominated poles being removed. 



The conditions as to soil and situation were in each locality 

 as similar as possible, the soil being a fresh, loamy sand 

 throughout. The results of the experiment were tested five 

 years after the thinnings took place. 



