PLENARY THINNINOa. 481 



a new ^owtb forming a full undercrop and obtained either by 

 natural or artificial means. 



Plenary thinnings are too recent an invention in sylviculture td 

 have yet been fully worked out to their legitimate consequences. 

 Nevertheless several systems have already been under trial long 

 enough to warrant the assertion that these thinnings are not only 

 not opposed to Nature, but enable the forester to favour to the 

 utmost the growth of his best trees and most valuable species, and 

 even put into his hands a most effective means of increasing the 

 proportion of these latter or of re-introducing them there whence 

 uncontrolled fellings in the past have driven them out. 



It will suffice, in a Manual written in the present condition of 

 Indian sylviculture, to describe in a very siunmary and general 

 manner the various systems adopted by European foresters in the 

 interests of their own species. That some such system will ulti- 

 mately be employed in our teak areas with immense benefit to 

 that species admits of little doubt. 



1. The young undercrop raised uniformly hy spontaneous 

 sowing over the entire area. 



Seebach's Method. — This is the simplest of all the systems of 

 plenary thinnings. As soon as a crop, that has been carefully 

 strengthened by means of ordinary thinnings, has become fully 

 fertile and a good seed year arrives, a plenary thinning is made of 

 sufficient severity to allow the new crop to be completely estab- 

 lished before the trees above can meet their crowns and reform 

 the leaf-canopy. In Europe, where this system is in use in beech 

 forests, the crop is opened out to such an extent as not to be able 

 to close up again for from 30 to 40 years. If, in the meanwhile, 

 it should be found that the thinning has not been sufficiently 

 severe, a second operation is of course permissible in order to 

 effect the necessary corrections. The rate of growth is found to 

 be doubled by this method of plenary thinnings (increased from 

 1'44 per cent in an unthinned crop to 2*90 per cent in one that 

 has been operated upon). 



HoMBUKs's Method. — In this method, which is employed only 

 in mixed forests, regeneration fellings on the uniform system are 

 commenced early and it is these fellings which actually constitute 

 the plenary thinnings, the after-fellings being made with a light 

 hand and at long intervals. This method differs from the pre- 

 ceding in that in the latter the upper crop necessarily ends by form- 

 ing a distinct leaf-canopy above the young one, whereas in this 

 one the favoured trees either always stand apart from one another 



