{"id":"baia-2025-varzea-quadratic","source":{"id":"baia-2025","citation":"Baia, A.L.P., Nascimento, H.E.M., Guedes, M., Hilário, R., Toledo, J.J. (2025). Tree height-diameter allometry and implications for biomass estimates in Northeastern Amazonian forests. PeerJ, 13, e18974.","title":"Tree height-diameter allometry and implications for biomass estimates in Northeastern Amazonian forests","authors":["Baia, A.L.P.","Nascimento, H.E.M.","Guedes, M."],"year":2025,"venue":"PeerJ","doi":"10.7717/peerj.18974","url":"https://doi.org/10.7717/peerj.18974","read_url":"https://europepmc.org/article/MED/40093411","access":"open","license":"Creative Commons Attribution License","checked_at":"2026-11-02","status":"current","notes":"Read the full text and tables via Europe PMC (PMC11908443); the publisher site blocks scripts. Height-diameter models, not biomass. Seven of the ten candidate models in Table 2 are captured (the best ones per forest type and for both forests pooled). The RSE in Table 2 is on the height scale (m), not log scale."},"name":"Height from DBH, Quadratic model, várzea","output":{"quantity":"height"},"expression":"exp(0.51504 + 1.07489 * ln(D) - 0.10005 * ln(D)^2)","published":{"expression":"exp(0.51504 + 1.07489 * ln(DBH) - 0.10005 * ln(DBH)^2)","units":{"DBH":"cm"},"variables":{"DBH":"D"},"output_unit":"m"},"taxon":{"level":"mixed","name":"Mixed Amazonian forest trees (367 species in terra-firme, 65 in várzea)","group":"mixed"},"region":{"scope":"site","countries":["BR"],"place":"Seasonally flooded várzea forest, Mazagão, Amapá, Brazil","biomes":["tropical"]},"stand":"natural","fit":{"n_trees":806,"dbh_min_cm":5,"dbh_max_cm":139.5,"h_min_m":2.3,"h_max_m":38.8,"r2":0.65,"method":"nonlinear least squares height-diameter model; R2 is the adjusted pseudo R2"},"evidence":[{"field":"expression","quote":"H = exp(a + b × ln(DBH) + c × ln(DBH)²) + ε ; Table 2: Quadratic a 0.51504 0.158 4.161 0.65 4,590.7 | b 1.07489 0.1 | c −0.10005 0.015","locator":"Table 1 (form) and Table 2, Várzea block"},{"field":"fit.n_trees","quote":"We sampled 1,156 trees of 367 species ... in the terra-firme sites, and 806 trees of 65 species ... in várzea","locator":"Abstract"},{"field":"fit.dbh_min_cm","quote":"In the terra-firme sites, trees ranged from 1 to 109.1 cm DBH and 1.2 to 51.9 m in total height. In várzea sites, trees ranged from 5 to 139.5 cm DBH and 2.3 to 38.8 m in total height.","locator":"Results, first paragraph"},{"field":"fit.r2","quote":"Adj. pseudo R2 0.65","locator":"Table 2, Várzea block"}],"check":[{"inputs":{"D":10},"expected":11.7,"origin":"computed","note":"computed from the published form (coefficients as printed)"},{"inputs":{"D":30},"expected":20.36,"origin":"computed","note":"computed from the published form (coefficients as printed)"},{"inputs":{"D":60},"expected":25.503,"origin":"computed","note":"computed from the published form (coefficients as printed)"}],"verification":"original_read","checked_at":"2026-11-02","notes":"Predicts total tree height from DBH. The quadratic form is read as a + b ln(DBH) + c (ln DBH)^2 inside exp(); Table 1 prints ln(DBH) with a superscript 2, and ln(DBH^2) would not be separable from the b term. RSE printed in Table 2 is 4.161 (height scale, m), so fit.rse is not stored. Ranges are those printed for the trees sampled in this forest type. No correction factor is applied; the paper reports local models deviate 0.1% from measured heights."}