112 MISC. PUBLICATION 43 4, U. S. DEPARTMENT OF AGRICULTURE 



possible to inventory standing trees in the nursery in late summer and 

 determine roughly the probable amount of usable stock which the 

 nursery will produce. Some nurserymen for various reasons use the 

 root collar or thickened portion of the plant just below the juncture 

 of stem and root as a point of calipering. One advantage of this 

 method is that some species, especially shrubs, which do not develop 

 a definite central stem, if calipered above the ground line would be 

 classed as culls in spite of satisfactory total weight and root develop- 

 ment. Table 24 gives the caliper relationship of measurements at 

 the root collar, and at points one-half, 1, and 2 inches above it for 

 2 different sizes of trees for 10 common deciduous species. It will be 

 noted that there is a more rapid taper in such species as walnut, 

 catalpa, and coffeetree than for honeylocust or Osageorange. The 

 amount of taper may be influenced somewhat by soil and by density 

 of seedlings in the row but seems to be correlated much more closely 

 with the species. Caliper relationship of other sizes of trees can be 

 obtained by plotting caliper 2 inches above the root collar as the 

 abscissa on coordinate paper and the higher caliper values on the 

 ordinate. The 2 plotted points for any one species can be connected 

 and projected, and other values can be read from the straight line 

 drawn through the 2 points. Thus a black walnut seedling calipering 

 -£% inch at 2 inches will measure |^ inch at the root collar. 



The point where stock is measured may seem unimportant, but it 

 must be kept in mind that one-sixteenth inch difference in caliper 

 specifications may represent as many as 20 percent of the seedlings, 

 especially in the slower-growing species. 



Table 24. — Relation of caliper at 2 inches above root collar {in thirty-seconds of an 

 inch) to calipers at other points on the stem of 1-year-old nursery seedlings 



Species 



Black walnut 



Northern catalpa _ 



Coffeetree 



American elm 



Black locust 



Green ash 



Chinese elm 



Russian mulberry 



Honeylocust 



Osage-orange- ._. 



When caliper at 2 inches above 

 root collar is 4.0 



1 inch 



above root 



collar 



5.0 

 5.1 

 4.5 

 4.8 

 4.6 

 4.8 

 4.7 

 4.4 

 4.7 

 4.4 



Yz inch 



above root 



collar 



6.2 

 6.2 

 5.0 

 5.7 

 5.5 

 5.8 

 5.6 

 4.8 

 5.0 

 5.0 



Root col- 

 lar 



7.8 

 7.8 

 6.5 

 7.0 

 6.7 

 6. \ 

 6.4 

 6.3 

 5.6 

 5.8 



When caliper at 2 inches above 

 root collar is 6.0 



1 inch 



above root 



collar 



7.3 

 7.3 

 6.5 

 6.9 

 6.7 

 7.0 

 6.7 

 6.6 

 6.8 

 6.5 



Yi inch 



above root 



collar 



8.8 

 7.6 

 8.0 

 7.7 

 8.1 

 7.6 

 7.2 

 7.3 

 7.0 



Root col- 

 lar 



10.5 

 10.5 

 9.4 



9.4 

 9. 1 

 8.9 

 8.7 

 8.5 

 8.3 

 8.0 



Grading Standards for Various Species 



The only logical criterion for grading nursery stock is field survival 

 of various sizes of stock over a period of years. In order to set up a 

 grading standard, the Forest Service conducted a rather compre- 

 hensive experiment near Mangum, Okla., in 1936, in which over 

 20,000 1-year-old seedlings involving 14 different species were care- 

 fully graded into various sizes and then field planted (36). For most 

 species there were 10 or more lots of 100 trees each. Survival counts 

 were made at the end of the first year and data were obtained on the 

 height growth and vigor of the surviving seedlings. 



