244 SYLVICULTURE IN THE TROPICS 



rr. in 



While thinnings are being made, the cutting of 

 climbers should also always be attended to, and if the 

 trees are infested- by parasites, those which are so 

 attacked should be removed by preference, especially if 

 they belong to inferior species. 



In a forest the upper tier of which, if there are more 

 than one, is composed entirely of crowns of trees which 

 have attained their full height, there is no longer a fight 

 among them for attaining the light, but for expansion of 

 the crown. If no thinnings are done, the crowns of the 

 weaker get gradually compressed, but this is a slow pro- 

 cess, and in the meanwhile the production of timber per 

 unit of area is not as great as it might be. It has been 

 proved that by giving more growing room to a certain 

 number of the dominant crowns the production of 

 timber gets much increased. To what degree the thin- 

 ning out may be done will no doubt largely depend on 

 species, soil, and locality, but the opinion of European 

 foresters seems to favour the complete isolation of the 

 strongest or most valuable of the trees, in order that they 

 may have plenty of room to spread out and attain an 

 exploitable size as soon as possible. These thinnings, 

 which have been called Plenary thinnings, 1 might lead 

 to the deterioration of the soil, and where they are 

 carried out it is necessary to provide for an underwood, 

 either by means of species which have sprung up under 

 shelter of the upper tier or which have been left behind 

 in the struggle for height, or to provide one artificially 

 by sowing or planting, preferably the latter, as it will 

 attain the necessary dimensions earlier. As has already 

 been seen, where the species in the upper tier are mostly 

 shade-avoiding, a lower tier, naturally raised, is easier to 

 obtain. 



The time for marking trees for thinnings is when they 

 are in full foliage ; it is only then that the space occupied 

 by the crowns can be fully appreciated. The best time 

 for felling, on the other hand, is during the period of 

 least vegetable activity. By so doing the damage done 



1 E. E. Fernandez, Manual of Indian Sylviculture, p. 499. 



