Spatial distribution of biomass in forests of the eastern USA

We produced a map of the biomass density and pools, at the county scale of resolution, of all forests of the eastern US using new approaches for conve rting inventoried wood volume to estimates of above and belowground biomass . Maps provide a visual representation of the pattern of forest biomass den sities and pools over space that are useful for forest managers and decisio n makers, and as databases for verification of vegetation models. We estima ted biomass density and pools at the county level from the USDA Forest Serv ice, Forest Inventory and Analysis database on growing stock volume by fore st type and stand size-class, and mapped the results in a geographic inform ation system. We converted stand volume to aboveground biomass with regress ion equations for biomass expansion factors (BEF; ratio of aboveground biom ass density of all living trees to merchantable volume) versus stand volume . Belowground biomass was estimated as a function of aboveground biomass wi th regression equations. Total biomass density for hardwood forests ranged from 36 to 344 Mg ha(-1), with an area-weighted mean of 159 Mg ha(-1). Abou t 50% of all counties had hardwood forests with biomass densities between 1 25 and 175 Mg ha(-1). For softwood forests, biomass density ranged from 2 t o 346 Mg ha(-1), with an area-weighted mean of 110 Mg ha(-1). Biomass densi ties were generally lower for softwoods than for hardwoods; ca. 40% of all counties had softwood forests with biomass densities between 75 and 125 Mg ha(-1). Highest amounts of forest biomass were located in the Northern Lake states, mountain areas of the Mid-Atlantic states, and parts of New Englan d, and lowest amounts in the Midwest states. The total biomass for all east ern forests for the late 1980s was estimated at 20.5 Pg, 80% of which was i n hardwood forests. Published by Elsevier Science B.V.