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THE OUTLOOK FOR TIMBER IN THE UNITED STATE& 



Stand-size class. A classification of forest land based on 

 the size class of growing-stock trees on the area; that is, 

 sawtimber, poletimber, or seedlings and saplings. 



Stocking. The degree of occupancy of land by trees, 

 measured by basal area and/or number of trees by size or 

 age and spacing, compared to a stocking standard, i.e., 

 the basal area and/or number of trees required to fully 

 utilize the growth potential of the land. 



Timber demand. The volume of timber that would be 

 purchased at specified prices at a specified point in time 

 under specified or implied assumptions relating to popula- 

 tion, income, and other technological or institutional factors. 



Timber supply (or timber harvest) . Net volume of round- 

 wood products available to forest industries from all sources 

 at specified or implied price levels. 



Tree size class. A classification of trees based on diameter 

 at breast height, including sawtimber trees, poletimber 

 trees, saplings and seedlings. 



Trend level. Estimate based on a curve or regression 

 equation constructed from observed values over time. 



Unproductive forest land. Forest land incapable of 

 producing 20 cubic feet per acre of industrial wood under 



natural conditions because of adverse site conditions such 

 as sterile soils, dry climate, poor drainage, high elevation, 

 steepness, or rockiness. 



Unregulated forest land. Commercial timberland in 

 National Forests not organized for timber production 

 under sustained-yield principles, including experimental 

 forests, recreation and administrative sites, and tracts of 

 commercial timberland so remote from manufacturing 

 centers that scheduling sustained periodic harvest is 

 impractical. 



Upper stems. That part of the bole of sawtimber trees 

 above the saw-log top to a minimum top diameter of 4.0 

 inches outside bark or to the point where the central stem 

 breaks into limbs. 



Wilderness area. An area of undeveloped Federal land 

 retaining its primeval character and influence, without 

 permanent improvements or human habitation, which is 

 protected and managed so as to preserve natural conditions. 



Young-growth stands. Stands in which 50 percent or 

 more of the stand is occupied by sawtimber trees less than 

 100 years old. 



