Methods to estimate total forest biomass for extensive forest inventories: applications in the northeastern U.S.

BackgroundSince 1928, the USDA Forest Service has measured the Nation's forest resources, supplying information about their nature and condition.In the past, forest inventories focused on volume estimation: cubic feet for growing stock and board feet for sawtimber (these and other terms are defined in Appendix F).Volume statistics have proven useful to resource planners and managers for quantifying the timber supply and for tracking changes in the timber resource over time.But conventional methods for measuring timber volume do not adequately define conditions of the entire forest and, therefore, have limited applicability to the kinds of assessments required of today's resource planners, managers, and researchers.We now recognize that our forests are not only a source of wood for traditional timber products but also of wood fiber for new industrial products and nonindustrial products such as fuelwood.In addition, the nation's forest resource plays an important part with respect to wildlife habitat, plant diversity, nutrient recycling, and biochemical interchanges so essential to our survival that are affected by climatic change and manmade pollution.Merchantable-stem biomass is best reported in both green weight and dry weight.Most of the other components of forest biomass-branches, foliage, stumps and roots, cull trees, seedlings and saplings, shrubs, etc.-are best reported in dry weight since biomass studies today tend to be directed more to vegetation analysis and biodiversity studies, that generally require biomass to be reported in dry weight. Procedures for Estimating Dry WeightFor extensive forest surveys, the most important parts of total forest biomass to report (Fig. 1 ) are: *The woody biomass in the merchantable stem of growing-stock trees (also called growing stock), which can be further apportioned into poletimber, sawtimber, and the upper stem portion above sawtimber.*Additional sources of biomass in growing-stock trees-branches, foliage, and the stump-root system-and cull trees which together constitute timber..The biomass in nontimber trees, e.g., salvable dead trees, seedlings, and saplings.*Other kinds of nontree-related forest biomass, for example, shrubs..The biomass on land that is not capable of producing commercial crops of timber. 2 Key species (I b/ff) K e y species (I b/f?) (I blf?) Key species glwrt') Key species