{"id":"westfall-2024-quercus-alba-m220-small","source":{"id":"westfall-2024","citation":"Westfall, J.A., Coulston, J.W., Gray, A.N., Shaw, J.D., Radtke, P.J., Walker, D.M., Weiskittel, A.R., et al. (2024). A national-scale tree volume, biomass, and carbon modeling system for the United States. Gen. Tech. Rep. WO-104. Washington, DC: USDA Forest Service. 37 p.","title":"A national-scale tree volume, biomass, and carbon modeling system for the United States","authors":["Westfall, J.A.","Coulston, J.W.","Gray, A.N."],"year":2024,"venue":"USDA Forest Service General Technical Report WO-104","doi":"10.2737/WO-GTR-104","url":"https://doi.org/10.2737/WO-GTR-104","read_url":"https://research.fs.usda.gov/download/treesearch/66998.pdf","access":"open","checked_at":"2026-11-01","status":"current","notes":"The National Scale Volume and Biomass (NSVB) framework, adopted by FIA as the current US standard for tree volume, biomass and carbon (replacing the Component Ratio Method built on Jenkins et al. 2003). Read: May 2024 GTR, slightly revised February 2026. Models are fitted by species (or species group) within FIA ecodivision, with D in inches at 4.5 ft, H in feet, output in pounds; four model forms (Schumacher-Hall, segmented, continuously variable, modified Wiley). Coefficients live in supplemental CSV tables S1a–S11 (doi:10.2737/WO-GTR-104-Supp1), which we could not download (fs.usda.gov returned HTTP 403 to scripted requests). Only the white oak AGB model printed in full in Example 4 is captured here; other target species (loblolly pine SPCD 131, which has separate planted/natural fits; yellow-poplar; sweetgum; red oak) need table S8a. AGB here excludes foliage and is the gross 'AGBPredicted' before cull/broken-top reductions and harmonization with components."},"name":"NSVB white oak, Hot Continental Mountains (M220), segmented model, D < 11 in (27.94 cm)","output":{"quantity":"agb","excludes":["foliage"]},"expression":"0.45359237 * 0.024470323124 * (D/2.54)^1.93799905037 * (H/0.3048)^1.403264431619","published":{"expression":"0.024470323124 * DBH^1.93799905037 * HT^1.403264431619","units":{"DBH":"in","HT":"ft"},"variables":{"DBH":"D","HT":"H"},"output_unit":"lb"},"taxon":{"level":"species","name":"Quercus alba","family":"Fagaceae","group":"broadleaf"},"region":{"scope":"regional","countries":["US"],"place":"FIA ecodivision M220, Hot Continental Mountains (Appalachian/Ozark highlands)","biomes":["temperate","montane"]},"stand":"mixed","fit":{"dbh_max_cm":27.94,"method":"NSVB segmented model (Eq. 2), lower branch; same coefficients a, b, c as printed in Example 4"},"evidence":[{"field":"expression","quote":"AGBPredicted = 0.024470323124 × 11^(1.93799905037 – 1.886819489967) × 18.1^1.886819489967 × 65^1.403264431619 = 2285.319903933610","locator":"Example 4, p. 24"},{"field":"taxon","quote":"a live white oak (Quercus alba; SPCD = 802) tree having D = 18.1 inches, H = 65 feet","locator":"Example 4, p. 21"},{"field":"region","quote":"growing in the Hot Continental Mountains (DIVISION = M220)","locator":"Example 4, p. 21"},{"field":"expression","quote":"k is a set segmentation point that is 9.0 inches for softwoods (SPCD<300) and 11.0 inches for hardwoods (SPCD≥300)","locator":"Methods, Model development, p. 2"},{"field":"published.units","quote":"Di is diameter (inches) at breast height (4.5 feet), Hi is total tree height (feet)","locator":"Methods, p. 2"},{"field":"expression","quote":"yi = a × Di^b × Hi^c + εi; Di < k","locator":"Eq. 2, p. 2"}],"check":[{"inputs":{"D":20.32,"H":15.24},"expected":151.2158,"origin":"computed","note":"computed from the published form at D = 8 in (20.32 cm), H = 50 ft (15.24 m), converted lb→kg"}],"verification":"original_read","checked_at":"2026-11-01","notes":"Lower branch of the segmented model (D < 11 in = 27.94 cm). The GTR does not print a worked value for this branch; the check is computed. a, b and c are the values printed in Example 4 (b = 1.93799905037 is the exponent inside k^(b−b1)). dbh_max_cm is the segmentation point, not a data range. Same output definition and unit conversions as the large-tree branch."}