24 .CIRCULAR 3 3 3, U.S. DEPARTMENT OE AGRICULTURE 



tags. The objections to painting are that it takes longer to paint 

 numbers than to place tags, especially on small trees ; chemical com- 

 pounds contained in the bark of certain tree species cause the paint 

 to fade quickly, with the result that the numbers have to be repainted ; 

 the bark on some species scales freely ; cracks in the bark, caused by 

 growth, make numbers difficult to read if not often renewed; the 

 smoothing of rough bark to receive the painted numbers sometimes 

 affects the growth of the tree ; and painted numbers may be effaced 

 by fires. 



TAGGING 



The kind and size of tag to be used in marking sample-plot trees 

 are largely matters of personal preference. Zinc, copper, brass, 

 aluminum, iron, and tin tags have been used. Of these metals iron 

 and tin are the least durable out-of-doors. Aluminum is lightest 

 in weight. Small painted galvanized-iron or wooden panels have 

 been used (pi. 5, D). 



Under conditions of fairly high atmospheric moisture, and espe- 

 cially in regions in which the atmosphere contains industrial gases, 

 aluminum and zinc tags attached to trees by copper wire or nails are 

 rapidly corroded by electrolytic action. There should be recognition 

 of this phenomenon in the choice of tag and wire or nail material. 



Tags may be bought already numbered in series, numbers may 

 be stamped with hand dies on tags of soft metal like copper or zinc, 

 or tags of aluminum ribbon may be numbered on an embossing 

 machine. Figures one-half to three-fourths of an inch high on 

 tags iy 2 inches in diameter are easy to read, but the tags are bulky 

 and are so conspicuous that they are likely to be stolen. Figures 

 much less than one-fourth of an inch high, on the other hand, are 

 hard to read. 



Perhaps the greatest satisfaction is given by tags punched out 

 of aluminum ribbon on an embossing machine. Such tags, shown 

 in plates 3, 4, and 6, B, can be made up as needed, and are light and 

 easy to handle. The ribbon is thin and likely to tear, however, 

 and in a hot forest fire may melt. Tags of fairly heavy aluminum 

 ribbon three-fourths of an inch wide are the most satisfactory for 

 use on large trees. For use on small trees and on reproduction, 

 %-inch ribbon is usually adequate. 



Durable nails should be used to affix tags to trees. Copper nails, 

 brass escutcheon pins, or galvanized nails may be used. Copper 

 nails when embedded in a tree are less injurious to saws than nails 

 of other metals. Size depends to some extent on the size and growth 

 rate of the trees. Galvanized wire nails 2% to 3% inches long, with 

 shanks that slip easily through the holes in the tags and with heads 

 large enough to hold the tags, are satisfactory in most cases. In 

 species with such hard wood as hickory or white oak, difficulty is 

 experienced with any type of nail. 



Tags are usually hung at breast height. 



The point of the nail should not be driven deeply into the wood. 

 The shank should protrude sufficiently to allow for radial growth 

 up to the time of the next remeasurement, and at that time it should 

 be pulled out so that it again protrudes. On trees with very thick 

 bark the nail need not be driven to the cambium, in which case it 

 will not be grown over at all. In some species with moderately 



