Measures and yields of products and residues 3275 



the Southeastern average (Florida, Georgia, North Carolina, and Virginia) 

 above-ground green weight of wood and bark in all live trees 1 .0-inch dbh and 

 larger (foliage-free) was 70.7 tons per acre, representing a very wide range. The 

 average for Florida was 55.2 tons and that for Virginia 81.8 tons (table 27-98 A). 

 Three factors obviously influence the biomass on a forest acre — age, stocking, 

 and productivity of the site. A newly established stand may contain no woody 

 material in stems over 1 inch in diameter at breast height, while a mature 

 hardwood sawtimber stand on a good site may contain over 250 green tons of 

 biomass per acre. In Forida, where average biomass per acre is relatively low, 

 more than half of the material is softwood. A large proportion of this softwood 

 biomass is in pine plantations that are managed on short rotations. At the end of 

 each rotation, biomass returns to near zero. In Virginia, on the other hand, more 

 than three-fourths of the biomass is hardwood, and many of the hardwood stands 

 are not managed for high timber production. Biomass has been allowed to 

 accumulate in these stands for long periods, and it will continue to do so as long 

 as hardwoods are underutilized (McClure et al. 1981). 



For mixed hardwood stands on a variety of sites, table 27-44 provides 

 estimates of the green and dry weight of (1) all live trees, (2) all trees between 

 3.5 and 5.5 inches in dbh, and (3) residues left after subtracting the board-foot 

 component of the stand. 



For evenaged, upland oak forests, the yield per acre of all trees and of all 

 trees 5 inches or more in dbh has been tabulated for stand ages 10 to 100 years 

 and for five site indexes (table 27-98). Wiant and Castaneda (1978) developed 

 these preliminary tables by applying the species weight equations (Wiant et al. 

 1977) to Schnur's (1937) stand tables for fully stocked, evenaged second-growth 

 upland oak forests. Wiant and Castaneda (1978) give tables for both green and 

 dry weights, with and without bark; only the dry weight with bark is reproduced 

 here. For bark weights, see chapter 13. 



In a study of stands on various sites and containing species mixtures typical of 

 Appalachian mountain hardwoods, Frederick et al. (1979) developed regres- 

 sion equations for predicting the weight yields of the total stand and of the 

 merchantable boles. Merchantable basal area (BA) expressed as square feet per 

 acre was found to be the most reliable variable for estimating total stand weight 

 yields in tons per acre: 



Total green weight =9.34 + 1.22 (BA) R2 = 0.84 (27-35) 

 Total dry weight = 1.81 + 0.76 (BA) R^ = 0.81 (27-36) 



Weight of merchantable boles in tons per acre to a 4-inch dob top was best 

 related to the ratio between merchantable basal area (B A) in square feet per acre 

 and number of merchantable trees (NM) per acre: 



Green weight of merchantable boles = 



-26.50 -f- 271.22— R2 = 0.73 (27-37) 



NM 



Dry weight of merchantable boles = 



RA 



-20.83 + 167.59-^^ R2 = 0.71 (27-38) 



NM 



