410 



NORMAL YIELD TABLES FOR EVEN-AGED STANDS 



TABLE LXIII 



Percentage of the Various Species in Mixture prom Table LXII Classified 

 as to Type and Site Class 



* Under miscellaneous are included all species whose combined representation in the plots of 

 any one type or site class is leBS than 5 per cent of the total number of trees. These species 

 are: white oak, black cherry, pignut hickory, white pine, hemlock, elm, butternut, hop horn- 

 beam, black birch, flowering dogwood, and shad bush. 



By either of the above two methods of constructing yield tables for 

 mixed stands, the yield of the entire stand is taken as the standard of 

 yields. 1 



The classification of mixed stand may be greatly simplified by group- 

 ing together all plots in which 80 per cent or over of the merchantable 

 volume is made up of certain species. In a study of the mixed conifer 

 type on the Plumas National Forest in California, containing Western 

 yellow pine, sugar pine, Douglas fir, white fir, and incense cedar, 

 75 per cent of 156 plots were found to contain but two principal species 

 whose combined volume was over 80 per cent of the plot. The yields 

 could be grouped as 



1. Yellow pine — Douglas fir. 



2. Yellow pine — Fir (Douglas or white). 



3. Douglas fir — white fir. 



As indicating the possibilities of simplifying the problem of yields of 

 mixed stands, it was found in this study that the average basal areas, for 

 plots showing the same standard of height growth (§ 296) was as follows: 



1 A method by which the per cent of yields in plots of mixed species is recorded 

 on the cross section paper, and the yield per acre expressed for different species 

 which constitute different per cents of the total stand, is described in Graves' 

 Forest Mensuration, Chapter XVII, p. 332. 



