212 Studies in Forestry [CHAP. x. 



in which this makes itself apparent is very frequently rather 

 in the energetic formation of new roots and of thicker foliage, 

 which ultimately exert their due influence on the increment of 

 the stem, than in the immediate thickening of the annual rings, 

 or the immediate formation of woody-fibrous tissue. And, 

 wherever the other main factors exerting influence on the pro- 

 ductive capacity of the soil are not at the same time tended 

 and well provided for, stimulated increment cannot always be 

 expected as the natural result of diminishing the number of 

 trees forming the crop. Thus, for example, care must be taken 

 to prevent deterioration of the soil (where necessary, even by 

 underplanting) in consequence of insolation, and of the drying 

 and exhausting effects of winds, or with regard to the soil- 

 moisture and to the soil-covering of dead foliage requisite for 

 the formation of humus or vegetable mould. 



In one case, however, the current increment of the trees 

 may be directly decreased at first in place of stimulated. 

 This is, when the fuller exposure to light and air leads in 

 the first instance to abnormal increase in the production of 

 seed, in consequence of a tendency to the formation of albu- 

 minoid substances in place of carbo-hydrates ', as is especially 

 liable to take place in the case of trees that were already pre- 

 dominating throughout the canopy at the time of the partial 

 clearance being made. And, of course, if the partial clearance 

 be carried too far, the increment on the remaining crop will 

 probably be injuriously affected by the natural consequences 

 resulting from over-exposure of the soil to insolation and the 

 action of winds, and from exposure of the stems themselves 

 to sunburn or scorching of the bole in smooth-barked species, 

 to increased danger from windfall and insects, as well as to 

 the greater damage apt to be done during the felling of the 

 stems that are being removed, and the grubbing up of their 

 stumps. 



1 Rinicker, Der Zuivachsgang in Fichten- und B^uhenbestdnden, 1886, 

 p. 30. 



