Biomass estimation for temperate broadleaf forests of the United States using inventory data

Abstract

A potentially valuable data source for estimating forest biomass is forest volume inventory data that are widely collected and available throughout the world. In this paper we present a general methodology for using such data to reliably estimate aboveground biomass density (AGBD) and to develop expansion factors for converting volume directly to AGBD from USDA Forest Service Forest Inventory and Analysis (FIA) data. Growing stock volume inventory data and stand tables were combined with independently developed biomass regression equations to estimate AGBD and to calculate biomass expansion factors (BEF: factors that convert volume to mass, accounting for noncommercial components) for the extensive oak-hickory and maple-beech-birch forest types of the eastern United States. Estimated aboveground biomass for both forest types ranged between 28 and 200 Mg ha-1. Expansion factors decreased from more than 4.0 at low growing stock volume to nearly 1.0 when growing stock volume was as high as 190 m3 ha-1, consistent with theoretical expectations. In stands with low AGBD (< 50 Mg ha-1), small diameter trees (< 10 cm diameter) contained up to 75% of the AGBD in trees ≤ 10 cm diameter; this proportion dropped to < 10% for stands with AGBD > 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 broadleaf forests. Further, the pattern between BEF and stand volume was similar to that obtained for tropical broadleaf forests, except that tropical forests generally had larger BEFs than temperate forests at a given volume. The implications of these results suggest that a recent assessment of forest biomass in developed countries is too low.