Past clearing and harvesting of the deciduous hardwood forests of eastern USA released large amounts of carbon dioxide into the atmosphere, but through recovery and regrowth these forests are now accumulating atmospheric carbon (C). This study examined quantities and distribution of aboveground biomass density (AGBD, M-g ha(-1)) of US eastern hardwood forests and assessed their biological potential for continued biomass accumulation in the future. Studies have shown that the presence of a large proportion of the AGBD of moist tropical forests in large diameter trees (> 70 cm diameter) is indicative of mature and undisturbed conditions. This relationship was tested as a criterion for the eastern US deciduous forests to assess their stage of recovery and maturity, and evaluate their potential for continued C storage. The approach was to compare AGBD and its distribution in large trees for old-growth forests derived from published studies and for oak-hickory and maple-beech-birch forests using the extensive US Forest Service Forest Inventory and Analysis (FIA) data base. Old-growth forests generally had AGBD of 220-260 Mg ha(-1) with up to 30% in trees with diameter > 70 cm. In contrast, maximum AGBD for the FIA units was about 175-185 Mg ha(-1) with 8%-10% in large trees. Most units, however, were below these maximum values, suggesting that the forests represented by the FIA inventory are in various stages of recovery from past disturbance. Biologically, therefore, they have the potential to accumulate significant quantities of additional biomass, if left unharvested, and thus storing atmospheric C into the future. (C) 1997 Elsevier Science B.V.
