A PRACTICAL APPLICATION OF PRESSLER'S 



FORMULA 



By a. B. RecknageIv^ 



The purpose of this paper is to show how Pressler's well-known 

 formula^ may be used in a practical way to determine the current 

 annual increment in mixed, selection forest and, from this, to 

 work out the regulation of the cut. The data used were ob- 

 tained in connection with work done by Cornell University 

 students in the Catskills and Adirondacks during 1914 and 

 1915. Criticisms of the methods used and the results secured 

 are invited in order that the method, if at all meritorious, may 

 be perfected. 



Probably no stands present greater difficulties in determining 

 the current annual increment than do those of the hardwood type 

 in the Northwoods. Aside from the conifers, at least three chief 

 hardwood species are involved — beech, birch and maple. The 

 stands are uneven-aged and markedly irregular in composition. 

 The condition of the stand encountered in the Catskills is well 

 illustrated by the stand and stock tables (tables 4, 5, 6 and 7) 

 printed Bulletin 11 of the New York State Conservation Com- 

 mission.^ 



To get some idea of the growth in this heterogeneous forest, 

 stump analyses were made on 132 beech, 123 Yellow birch, 71 

 Hard maples and 8 White ash trees in nearby cuttings. Incre- 

 ment borings were made on 109 hemlock and 167 balsam trees. 

 The customary diameter-age curves were prepared for the hard- 

 woods ; the data for the conifers were also averaged and curved. 

 In this way, the year required to grow one inch in d.b.h. were 

 obtained, and from this, by the use of Pressler's formula, the 

 current annual increment per cent. The results are as follows: 



^Professor of Forestry, Cornell University. 



'See Graves' Forest Mensuration, John Wiley & Sons, New York, 

 1906, pp. 304-9. 



'Bulletin 11, Forest Survey of a Parcel of State Land, Albany, N. Y., 

 1915. 



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