360 NATURAL EEGHNERATION BY SEED. 



The differentiation of a forest into dissimilar groups results from 

 one or more of the following causes : — difference of aspect, eleva- 

 tion and gradient, different degrees of exposure to dangerous winds, 

 differences in the depth, physical characters, chemical composition 

 and moisture of the soil, differences of subsoil, &c. An important 

 consequence, flowing from the great principle of independent treat- 

 ment on which the group method is based, is that no group is 

 taken in hand for regeneration unless circumstances are ripe for it, 

 unless, in other words, its success is from the very beginning 

 assured. 



We are now in a position to consider the extent and manner of 

 application, in the present case, of the three classes of serial rege- 

 neration fellings. 



ARTICLE 1. 



The peepaeatory fellings. 



It will nearly always happen that when a group is taken in hand, 

 a more or less complete advance growth has already made its ap- 

 pearance, rendering preparatory fellings entirely superfluous. In 

 some groups, however, it may be found that the trees require 

 encouragement in order to become good seed-bearers and nurses', 

 and that the soil is not in a fit condition for the reception and ger- 

 mination of seed and the prosperous growth of the resulting seed- 

 lings ; in such groups the preparatory fellings cannot be dispensed 

 with, but they will assume a different character according to the ' 

 special conditions obtaining. For instance, in one case, although 

 the trees in the group itself may be thin and weak-crowned and un- 

 able to sow the ground for many years to come, yet the surrounding 

 groups may contain good seed-bearers capable of sowing most, if 

 not the whole, of its area, in which cise the preparatory operations 

 as such will be limited mainly to improving the soil, and in any 

 felting that may be made, the preparation of the trees as seed- 

 bearers and nurses will be entirely subordinated to the constant 

 maintenance of a protection-affording leaf-canopy and to the thin- 

 ning out of the forest growth for increased production. This 

 thinnino- will do nothing more than remove only weak, suppressed 

 or unhealthy and unsound trees and those that are low-crowned, 

 and the leaf-canopy will never be opened out to the same extent as 

 under similar conditions in the uniform method. In a second case, 

 the stock in the group to be operated upon being the same as be- 

 fore, the surrounding groups also may contain unfertile trees ; ia 



