Biomass and NPP estimation for the mid-Atlantic region (USA) using plot-level forest inventory data

As interest grows in quantification of global carbon cycles, process model predictions of forest biomass and net primary production (NPP) are being de veloped at an accelerating rate. Such models can provide useful predictions at large scales, but it has been difficult to evaluate their performance. Using the network of plots comprising the comprehensive and spatially exten sive Forest Inventory and Analysis (FIA) data set collected and maintained by the USDA Forest Service, we applied methods typically used in field meas urements to develop estimates of forest biomass and NPP for the mid-Atlanti c region of the United States at a scale appropriate for comparison with mo del predictions. Plot-level and tree-level forest inventory data from a sub set of plots were used together with species-specific biomass regression eq uations to calculate maximum current biomass and NPP values for the mid-Atl antic region. Estimates at the plot level were aggregated by forest type an d to the 0.5 degrees x 0.5 degrees scale for analysis and comparison with p rocess model predictions. Maximum current forest biomass averaged 248 and 200 Mg.ha(-1).yr(1) in hard wood and softwood forest types, respectively; wood biomass increment averag ed 559 and 460 g.m(-2)-yr(-1) in hardwood and softwood forest types, respec tively. Aggregated to the 0.5 degrees x 0.5 degrees scale, forest biomass r anged from 101 to 326 Mg/ha, while wood biomass increment ranged from 254 t o 1050 g.m(-2).yr(-1). Biomass and NPP estimates for closed-canopy forests from this study were consistent with values reported in the literature but were as much as 50% lower than values reported for old-growth stands. NPP p redictions from three process models were fairly consistent with the FIA-ba sed estimates, but model predictions of biomass were higher than estimates from FIA data for the region. By describing upper and lower bounds on reaso nable biomass and NPP values for closed-canopy forests, these FIA-derived e stimates provide a foundation for model comparison and continued model deve lopment.