3278 Chapter 27 



PRIMARY UNITS— A NEW MEASUREMENT CONCEPT 



Access to electronic computers and dendrometers has enabled foresters to 

 avoid many of the difficulties associated with traditional units of measure. 

 Grosenbaugh (1954) found that the products derivable from trees or logs can be 

 closely approximated in terms of aggregate weight and length. He proposed and 

 developed computer programs (Grosenbaugh 1967ab, 1968), for systems in 

 which felled or standing tree inventory data are sampled with varying probability 

 and measured in terms of these primary units. Essentially, such timber estimates 

 require physical or optical segmenting of tree stems into sections of irregular 

 length but each reasonably homogeneous as to quality and defect, and the 

 measurement, by calipers, diameter tape, or precision dendrometer, of sectional 

 diameters and lengths. Volumes and surface areas, along with lengths, are 

 computer- accumulated by species, quality, and defect classes. 



Local product-yield studies can relate these aggregates of primary units to 

 actual outturn and value for a specific operation, and can provide estimates of 

 costs and residues at any desired stage of the manufacturing process. At the same 

 time, estimates can be cheaply made in terms of traditional units for accounting 

 or other purposes. 



Although not yet widely employed, this concept could greatly improve the 

 accuracy of product estimation wherever a wide range of size, defect, or value 

 classes is involved. 



BIOMASS INVENTORIES 



As recently as 1 975 , whole-tree and complete-tree harvesting accounted for 

 less than 0. 1 percent of the total forest harvest worldwide (Keays 1975). How- 

 ever, the concept is rapidly becoming an economic necessity. As more complete 

 utilization becomes widespread, forest inventories should be developed in terms 

 of whole aboveground biomass and complete above- and below-ground biomass 

 as well as in terms of conventional merchantable timber. 



Traditionally Forest Survey inventories have not included total tree height, 

 and this measurement is essential for calculating the volume or biomass of the 

 complete tree. Thomas ( 1 98 1 ) provided equations for estimating total tree height 

 from data readily available in Forest Survey inventories. The equations, which 

 are based on studies in Arkansas and are now being tested in other parts of the 

 South, give more accurate estimates than those based on dbh alone (R^ = 0.85 

 for these hardwood equations vs 0.74 for estimates by dbh alone). Since the 

 equations are long and complex they are not reproduced here. 



Studies on nearly 2.4 million acres of Maine forests indicated that if a biomass 

 inventory is made in conjunction with a volume inventory, the combined inven- 

 tory costs at most 5 percent more than a volume inventory alone but yields more 

 than twice as much useful information (Young 1978a, p. 40). The additional 

 field work simply involves measuring all trees in the 1-inch class and larger on a 

 point sample and all woody shrubs and trees larger than 1 foot in height and less 

 than 1 inch in diameter on a small sized plot of 1/1000 acre (Young 1978b, p. 

 25). A complete set of fresh and dry weight tables or regression equations for 



