98 BRITISH FOREST TREES 



backs under which pure forests of spruce suffer. With the 

 cessation of total clearances over large areas it is beyond all 

 doubt that dangers from insects during the youthful period 

 of growth, from snow during the pole-forest stage of develop- 

 ment, and from wind when approaching maturity, would all 

 be practically, and very considerably, lessened by the forma- 

 tion of several blocks, each with its growing stock of successive 

 annual crops from one to eighty or a hundred years according 

 to the period of rotation fixed on, in place of having the total 

 area divided simply into eighty or a hundred compartments as 

 the case may be, from the oldest of which a total clearance 

 of the mature timber is annually made. 



The usual method of regeneration of pure forests of 

 spruce is, as above indicated, total clearance with artificial 

 reproduction, except at very high altitudes where considera- 

 tions of treatment are usually secondary to those relative to 

 the general economic value of maintaining the higher moun- 

 tains under forest in order to prevent landslips, and to regu- 

 late the flow of moisture through the soil and ensure the peren- 

 nial feeding of the streams which have their sources there. 



The unsuitability of the method of natural reproduction 

 under parent standards that is customary in the case of the 

 other two densely foliaged shade-bearing species, silver fir 

 and beech, finds easy explanation in the indifferent resistance 

 which the spruce is able to offer to the violence of storms, 

 otherwise the diminished increment that is attained by 

 the young crop during the earlier stage of growth would 

 be amply compensated by the protection against various 

 dangers which the parent trees would secure to their 

 progeny during the first ten to twenty years. Experience 

 has, however, shown that attempts at natural reproduction 

 in this manner, except in very sheltered localities, usually 

 lead to the parent standards being thrown by wind, when a 

 rank growth of weeds soon covers the soil, and chokes a large 



