BIOMASS ESTIMATION FOR TEMPERATE BROADLEAF FORESTS OF THE UNITED-STATES USING INVENTORY DATA

A potentially valuable data source for estimating forest biomass is fo rest volume inventory data that are widely collected and available thr oughout the world. In this paper we present a general methodology for using such data to reliably estimate aboveground biomass density (AGED ) and to develop expansion factors for converting volume directly to A GED from USDA Forest Service Forest Inventory and Analysis (FIA) data. Growing stock volume inventory data and stand tables were combined wi th independently developed biomass regression equations to estimate AG ED and to calculate biomass expansion factors (BEF: factors that conve rt volume to mass, accounting for noncommercial components) for the ex tensive oak-hickory and maple-beech-birch forest types of the eastern United States. Estimated aboveground biomass for both forest types ran ged between 28 and 200 Mg ha(-1). Expansion factors decreased from mor e than 4.0 at low growing stock volume to nearly 1.0 when growing stoc k volume was as high as 190 m(3)ha(-1), consistent with theoretical ex pectations. In stands with low AGED (< 50 Mg ha(-1)), small diameter t rees (< 10 cm diameter) contained up to 75% of the AGED in trees great er than or equal to 10 cm diameter; this proportion dropped to < 10% f or stands with AGED > 175 Mg ha(-1). The similarity of our results for two major forest types suggests that they may be generally applicable for estimating AGBD from inventory data for other temperate broad lea f forests. Further, the pattern between BEF and stand volume was simil ar to that obtained for tropical broadleaf forests, except that tropic al forests generally had larger BEFs than temperate forests at a given volume. The implications of these results suggest that a recent asses sment of forest biomass in developed countries is too low.