100 THINNING OF PLANTATIONS. 



the ground^ and afterward from time to time as may be necessary till the forest gains 

 its full maturity. These operations may be repeated every five years at first, and after- 

 ■ward at longer intervals. In the State forests of Franco, where the most valuable 

 timber is the object, and time of less consequence, the interval is some fifteen or twenty 

 years. Although in these operations no particular number of trees can be fixed as a 

 rule, it may serve as some guide to give the following as approximately the proper 

 number to be left : 



At ;30 to 40 years— 1,300 to 1,620 to theacre.i 



At 50 to GO years — 190 to 60« to the acre. 



At 70 to 80 vears— :}05 to 410 to the acre. 



At 90 to 100 yeai-s— 200 to 360 to the acre. 



The selection of trees to be removed in tliiuuing out forests so as to 

 allow the reserves the better chance for development, can best be done 

 in summer, when the foliage is the densest, and the effect of shade the 

 most apparent. An experiehced eye can at such a time more readily 

 judge as to what trees are most promising and what can best be taken 

 out. 



A recent writer upon practical forestry ^ in speaking of the proper 

 time for thinning a plantation, recommends that it be done early, and as- 

 signs as a reason that the lemaiEing trees will then have seasonable 

 opportunity for developing their lower-side branches. He remarks : 



It is those branches situated upon the lower part of the stem of the tree that supply 

 food and nourishment to the roots, and imless they are preserved vital at this critical 

 period of the tree's existence it very soon caases to develop itself and make wood. In 

 fact it ceases to grow to anything like satisfaction at that very early period when it 

 should be making wood faster than any other. To the preservation of the lower 

 branches of the celebrated larch forests of the Duke of Athol, more than anything 

 else, may be attributed their succeesful growth. The larch there were planted 6 feet 

 apart, and that distance, admitting that all the trees grew, allowed all the lower 

 branches to grow 3 feet in lengtfi all around. But as many of tbem would no doubt 

 decay, and from accident and other causes perish, many of the trees would thereby 

 produce their lower branches twice that length, hence the unparalleled results of the 

 growth of the larch in those forests. 



Having witnessed so much injury inflicted upon young plantations and some en- 

 tirely ruined by the lower branches being interfered with at a stage of growth too 

 early, I would recommend in the strongest ijossible terms the special attention of all 

 who have the management of plantations to this particular aspect of the subject. It 

 is often asked what rule can be given and how it may be known when either individ- 

 ual trees or plantations have the exact and proper quantify of branches upoi; them. 

 The rule for this is, as far as any rule can be given, to maintain a due proportion of 

 girth to the height of the tree, and these proportions are girth in inches to feet in 

 height. For example, a tree twelve feet hiy,h should have a girth a little above the 

 swell of the root of twelve iDches, and so of larger sizes. When trees attain the height 

 of 30 or 35 feet thinning thould be entirely discontinued, and frequently it should not 

 be prolonged after the trees are 20 to 25 i'eet in height, but allow the plantation to 

 grow undisturbed (except by cutting down dead or decaying trees) till it is ripe for 

 cutting down and clearing the ground. There is a danger of old trees having too 

 many as well as too few branches ; l)ut there is no danger of young trees having too 

 many, and if the rule given should be observed there will be no superfluity of 

 branches at any time, for if the proportional girth is too great it can soon (if there are 

 sufficient trees upon the ground) be reduced. 



The form of the tree, up to the period when the thinning should be discontinued, 

 should be conical or tapering, both in the stem and general form of the tree. After 

 thinning is discontinued the shape of the tree altera, both in the stem and branches; 

 the latter wither and fall off", till only the top is covered, and the form gradually changes 

 from a cone to a cylinder. The cause of this is the increase of woody deposits near 

 the live branches, and the decrease of it where the branches have fallen off'. 



1 In France, Duhamel and Varenne de Feaille advised a much greater reduction, 

 allowing, in fact, almost as much land for an oak as an apple-tree in an orchard. The 

 object in view was the thickness of the trees, rather than the height, and such broad 

 spreading trunks as ten or eleven meters between the trees would produce, could not. 

 fail of yi*"lding an abundance of the crooked pieces so much prized in ship-building. 



""On Thinning Plantations, as applicable in Practical Forestry," by Christopher 

 Young Michie, of Gullen House, CuUen. ( Transac. of Highland and Ag. Soc, 1876, p. 199.) 



