SITK UKTl'RMIiNATION- AM) VIKF.n FCUECAST 13 



out of the site classification has su<=^g,ested two methods for forecasting 

 tlie yields of irregular stands. One is simply the use of the yield tables 

 for regular stands, which would give about the maximum yield of 

 a well-stocked area ; allowance for cull, understocking, etc.. could be 

 made by means of an estimated reducing factor," and it is probable 

 that rather close forecasts could be made in this way. The other 

 method is 1)\' means of individual tree growth tables on d.b.h. basis 

 classilied according to the sites ])reviously described and arranged for 

 easy use in the field in the preparation of local yield and increment 

 tables suitable for forecasting the growth of the dominant trees under 

 the conditions locally i)revailing in an understocked stand. 



The plan proposed for the construction and application of the indi- 

 vidual tree tables is briefly as follows: Tables are prepared for each 

 species and for each site showing for 2-incli d.b.h. classes, the future 

 d.b.h. at end of 10, 20, etc., years (up to 50 years) of trees now dom- 

 inant and which may be expected to remain dominant during the period 

 for which the forecast is to be made. Similar tables are made showing 

 the present volume in cubic and board feet and that at the end of 10, 

 20, etc., years (up to 50 years) of trees corresponding in d.b.h. to those 

 in the tables just described, and in height to the figures in the height 

 growth site classification. The field man who wishes to apply these 

 tables in forecasting the growth of an understocked stand first 

 determines the site of the area according to the height growth 

 table, lie then la\s out and tallies one or more sample plots rep- 

 resentative of the local conditions of stocking, mixture, etc. 

 This tally is by 2-inch d.b.h. classes, by species, and by crown classes. 

 Having the number of dominants of a given species and d.b.h. class, 

 the present volume and probable future volume of these trees at the 

 end of any decade can be quickly determined from the volume forecast 

 table by a simple multiplication. When this is completed for all the 

 d.b.h. classes and all the species the results are added and placed on 

 an acre basis. The figures thus obtained give the total present and 

 probable future yields per acre of the dominant trees on the area, and 

 furnish a means by which the future rate of growth, may be readily 

 estimated. The intermediate and subordinate crown classes are ignored 

 in this growth forecast, since their growth is small and many of the 

 trees will likely disappear from the stand before long. Their volumes 



"Or the plan suggested by Ashe ("Determination of Stocking in Uneven-aged 

 Stands," referred to in footnote 8) may provide a means for applying "normal"' 

 yield tables to irregular stands. 



