THINNING AND PRUNING 137 



length of the stem. Where large timber is most in demand, 

 therefore, this system of thinning has many advantages ; but 

 where, on the other hand, moderate-sized trees of long length 

 and clean boles fetch as much or more per cubic foot than 

 larger but shorter boles, it is probably as well to thin 

 gradually and lightly to the end of the rotation. 



Such a system of thinning could, we are convinced, be 

 appropriately applied to every pure plantation in the country, 

 provided it has been planted thick enough to begin with. 

 This latter point is a more important one than many foresters 

 suppose, but upon it is based the success or failure of the 

 self-thinning system, which is either denounced or upheld, 

 according to the personal experience of the observer. When 

 planted too wide apart to begin with, however, the conditions 

 are altogether different. In the first place, no real struggle 

 for existence begins until the plants are strong enough to 

 render this struggle a serious one for both the victors and 

 the vanquished, and it has a far more weakening effect in 

 the case of a plant of ten or twelve years of age than in a 

 seedling of three or four or a stronger plant of five or six 

 years. With trees standing 3 or 4 feet apart at, say, five 

 years of age, the struggle begins before the side branches 

 have acquired any great size or strength, and there is not 

 much the matter ; but, where this distance has been increased 

 by death or other causes to 8 feet or so, one plant is able 

 to weaken the other to an injurious extent when close order 

 is reached, while the lower branches have acquired a strength 

 which leaves nasty snags upon the stem for many years 

 afterwards. The height-growth of such trees, again, will be 

 considerably less than those crowded up from the start, as 

 numerous examples, even in nursery lines, testify. Fully 

 5 per cent, of the height-growth of crowded light-demanding 

 or deciduous trees is lacking in those which have been 

 exposed throughout their growth, and, although height-growth 

 is not always everything, it makes a great difference in the 

 total value and cubic contents of the crop. With silver fir 

 or spruce the difference in height-growth due to density 

 alone is less marked ; but here we get rough timber with an 

 open order of growth, which is a worse feature than loss in 

 height for some purposes. 



