{"id":"jenkins-2003-aspen-alder-cottonwood-willow","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: Aspen/alder/cottonwood/willow (Table 4)","output":{"quantity":"agb"},"expression":"exp(-2.2094 + 2.3867 * ln(D))","published":{"expression":"exp(-2.2094 + 2.3867 * ln(dbh))","units":{"dbh":"cm"},"variables":{"dbh":"D"},"output_unit":"kg"},"taxon":{"level":"mixed","name":"Aspen/alder/cottonwood/willow species group (hardwood), United States","group":"broadleaf"},"region":{"scope":"national","countries":["US"],"place":"Conterminous United States","biomes":["temperate","boreal"]},"stand":"mixed","fit":{"dbh_min_cm":2.5,"dbh_max_cm":70,"r2":0.953,"rse":0.507441,"method":"OLS on ln-transformed pseudodata (230 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":"Aspen/alder/cottonwood/willow −2.2094 2.3867 230 70 0.507441 0.953","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":368.057,"origin":"computed","note":"computed from the published form at dbh = 30 cm"},{"inputs":{"D":10},"expected":26.7405,"origin":"computed","note":"computed from the published form at dbh = 10 cm"}],"verification":"original_read","checked_at":"2026-11-01","notes":"Group membership: Alnus, Populus and Salix (Table 1); includes Populus deltoides, P. tremuloides and hybrid-poplar parents. 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) = 1.1374. Superseded for FIA reporting by NSVB (Westfall et al. 2024) but still widely used in carbon protocols."}