SAMPLE PLOTS IN" SILVICULTURAL RESEARCH 25 



thick bark the nail will be held tightly but not overgrown if its 

 point barely penetrates the cambium. The nail should be driven 

 in such a way that the head is very slightly lower than the point. 

 The tag thus held rests at the head of the nail by reason of gravity, 

 and is not so likely to be grown over or coated with pitch. 



Tags made from metal tapes can be read in the field more quickly 

 and with fewer errors if nailed at the left of the number, only 

 one nail being used on each tag. 



When a plot is abandoned, all nails and tags should be removed. 



PAINTING NUMBERS 



Numbers painted on trees should be placed a foot above breast 

 height if the trees are not to be cut, and below stump height if the 

 trees are to be cut. The figures should be large enough to be easily 

 legible. In general, large figures are less subject than small ones to 

 distortion by the splitting of bark that results from rapid growth. 

 On rough-barked trees the place for the figures should be smoothed 

 off with a draw knife or a stiff wire brush. In this operation, which 

 is illustrated in plate 7, A, the cambium should not be exposed and 

 the bark should not be cut away at the point of diameter measure- 

 ment. Just how the removal of bark affects growth is not fully 

 understood. It may injure the cambium, retard growth, cause 

 " pitch-soaking " of the wood, or lead to the development of ad- 

 ventitious sprouts. The area of thinned bark may serve, also, as a 

 point of entrance for insect or disease, or may attract rodents such 

 as porcupines. 



It is not believed that painting has any direct effect upon the 

 cambium, although some colors absorb heat and so may tend, when 

 used on thin-barked trees, to stimulate growth in the region behind 

 the painted area. 



Figures may be painted freehand or by means of stencils or rubber 

 stamps. 15 Freehand numbering works better on large than on small 

 trees, and stenciling is more effective on small than on large trees. 

 Under present conditions, it appears necessary to go over stenciled 

 figures with a fine brush in order to correct irregularities and to give 

 the figures more body. Although this practice may seem to consume 

 too much time, it is believed to reduce the time requirement for 

 subsequent repainting. Painted numbers remain legible for from 

 5 to 15 years, according to the quality of the paint, the climate, and 

 how much the bark cracks. Under optimum conditions, painting 

 may last 20 years without great need of freshening. Under the most 

 severe American conditions, high-grade paints and carefully applied 

 numbers may not be legible for as long as 5 years. 



Usually, the numbers can be read more readily if the digits are 

 arranged vertically. 



For freehand painting or stenciling almost any kind of durable 

 paint can be used ; among paints of good quality none has thus far 

 been proved to give better service than another. Addition of a small 

 quantity of turpentine seems to enable most commercial paints to 

 penetrate the bark more thoroughly. If the paint is worked well 



15 A rubber-stamping method is described by Berg (10). Information obtained through 

 actual trials under American conditions is greatly needed. 



