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This paper contains a strategy for estimating total aboveground biomass of tropical forests. We developed regression equations to estimate aboveground biomass of individual trees as a function of diameter at breast height, total height, wood density, and Holdridge life zone (sensu Holdridge 1967). The regressions are applied to some 5,300 trees from 43 independent sample plots, and 101 stand tables from large-scale forest inventories in four countries, to estimate commercial and total aboveground biomass per unit area by forest type, and to estimate expansion factors defined as the ratio of aboveground to commercial biomass. The quadratic stand diameter (QSD, i.e., the diameter of a tree of average basal area) in a given forest stand influences the magnitude of the expansion factor. Stands of small trees have large expansion factors (up to 6.4), and as QSD increases, the expansion factor decreases to a constant value (about 1.75). For undisturbed forests in moist, moist transition to dry, and dry life zones respectively, the expansion factors for total aboveground biomass were 1.74, 1.95, and 1.57 respectively. For undisturbed, logged, and nonproductive forest categories used by the FAO to report global commercial wood volume data, we estimated expansion factors of 1.75, 1.90, and 2.00 respectively. Applying these factors to FAO data results in a 28 to 47% increase in previous volume-derived estimates of tropical forest biomass. However, estimates of tropical forest biomass based on small destructive samples continue to be high relative to estimates based on volume data. For. Sci. 35(4):881-902.
Institute of Tropical Forestry, USDA Forest Service, Southern Forest Experiment Station, Call Box 25000, Río Piedras, Puerto Rico 00928
Publication date: December 1, 1989
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Forest Science is a peer-reviewed journal publishing fundamental and applied research that explores all aspects of natural and social sciences as they apply to the function and management of the forested ecosystems of the world. Topics include silviculture, forest management, biometrics, economics, entomology & pathology, fire & fuels management, forest ecology, genetics & tree improvement, geospatial technologies, harvesting & utilization, landscape ecology, operations research, forest policy, physiology, recreation, social sciences, soils & hydrology, and wildlife management.