34 ELEMENTS OF SYLVICULTUEE. 



YIELD OF THESE CUTTINGS. The secondary and 

 final cuttings are made so as to favour the seedlings 

 already on the ground ; in consequence they are 

 made at unequal intervals of time, and without any 

 attempt at obtaining equal quantities of timber from 

 equal areas ; moreover the regeneration cuttings give 

 the largest out-turn of the most useful material ; 

 hence their annual yield should be based on volume, 

 and this will ensure a steady yield and the proper 

 carrying out of the cuttings. 



IMPROVEMENT CUTTINGS. Cleanings. Take as 

 many precautions as we may in carrying out the regen- 

 eration cuttings, it almost always happens, especially 

 on rich soils and in temperate climates, that species 

 with a light seed take possession of the ground, 

 notably among these are soft-wooded trees, such as 

 poplars, alders, willows and limes. They are gener- 

 ally rapid growers, and are not long in catching up 

 and overtopping trees of more valuable kinds. At 

 the outset their presence is no doubt useful because 

 they promote the early formation of the leaf-canopy, 

 but they become dangerous as soon as they attain 

 the height of the hard- woods, and when they have 

 once passed this height, they must be gradually re- 

 moved, for when their foliage is in close contact with 

 that of the more valuable trees, and just above it, 

 the latter would soon begin to languish and 

 might ultimately disappear altogether. A similar 

 result often occurs in a mixture of two or more valu- 

 able kinds, one of which springs up more rapidly 

 than the others during the first few years. 



The operation which thus consists in removing 



