{"id":"jenkins-2003-hard-maple-oak-hickory-beech","source":{"id":"jenkins-2003","citation":"Jenkins, J.C., Chojnacky, D.C., Heath, L.S., Birdsey, R.A. (2003). National-scale biomass estimators for United States tree species. Forest Science, 49(1), 12–35.","title":"National-scale biomass estimators for United States tree species","authors":["Jenkins, J.C.","Chojnacky, D.C.","Heath, L.S.","Birdsey, R.A."],"year":2003,"venue":"Forest Science","doi":"10.1093/forestscience/49.1.12","url":"https://doi.org/10.1093/forestscience/49.1.12","read_url":"https://research.fs.usda.gov/download/treesearch/6996.pdf","access":"open","checked_at":"2026-11-01","status":"current"},"name":"US national species group: Hard maple/oak/hickory/beech (Table 4)","output":{"quantity":"agb"},"expression":"exp(-2.0127 + 2.4342 * ln(D))","published":{"expression":"exp(-2.0127 + 2.4342 * ln(dbh))","units":{"dbh":"cm"},"variables":{"dbh":"D"},"output_unit":"kg"},"taxon":{"level":"mixed","name":"Hard maple/oak/hickory/beech species group (hardwood), United States","group":"broadleaf"},"region":{"scope":"national","countries":["US"],"place":"Conterminous United States","biomes":["temperate"]},"stand":"mixed","fit":{"dbh_min_cm":2.5,"dbh_max_cm":73,"r2":0.988,"rse":0.236483,"method":"OLS on ln-transformed pseudodata (485 points, generally at 5 cm dbh intervals) generated from published equations; no back-transform correction applied"},"evidence":[{"field":"expression","quote":"bm = Exp(β0 + β1 ln dbh)","locator":"Table 4 footnote, p. 20"},{"field":"expression","quote":"Hard maple/oak/hickory/beech −2.0127 2.4342 485 73 0.236483 0.988","locator":"Table 4 row, p. 20"},{"field":"fit.dbh_min_cm","quote":"bm = total aboveground biomass (kg) for trees 2.5cm dbh and larger","locator":"Table 4 footnote, p. 20"},{"field":"fit.rse","quote":"Root mean squared error or estimate of the standard deviation of the regression error term in natural log units.","locator":"Table 4 footnote §"},{"field":"fit.cf","quote":"we do not include CFs for the reader to use after back-transformation","locator":"p. 19, Correction factors"}],"check":[{"inputs":{"D":30},"expected":526.6281,"origin":"computed","note":"computed from the published form at dbh = 30 cm"},{"inputs":{"D":10},"expected":36.3158,"origin":"computed","note":"computed from the published form at dbh = 10 cm"}],"verification":"original_read","checked_at":"2026-11-01","notes":"Group membership: hard Acer, Carya, Fagus and Quercus (Table 1), i.e. white and northern red oak. dbh_max_cm is the 'Max dbh of trees measured in published equations'; data points are pseudodata, not trees. Hardwood groups were extended to 230 cm dbh with Freedman (1984) pseudodata. No log-bias correction: the authors deliberately omit it; a user could multiply by exp(RMSE²/2) = 1.0284. Superseded for FIA reporting by NSVB (Westfall et al. 2024) but still widely used in carbon protocols."}