{"id":"ntonmen-2022-trunk-d-h-rho","source":{"id":"ntonmen-2022","citation":"Yonkeu Ntonmen, A. F., Zapfack, L., Djomo Chimi, C., et al. (2022). Complementary allometric model of understory tree biomass in the semi-deciduous rainforest of Cameroon. Acta Botanica Brasilica, 36, e2020abb0475.","title":"Complementary allometric model of understory tree biomass in the semi-deciduous rainforest of Cameroon","authors":["Yonkeu Ntonmen, A. F.","Zapfack, L.","Djomo Chimi, C."],"year":2022,"venue":"Acta Botanica Brasilica","doi":"10.1590/0102-33062020abb0475","url":"https://doi.org/10.1590/0102-33062020abb0475","read_url":"https://www.scielo.br/j/abb/a/ykhPLqBFcf98nZLQ5nZSKZv/?lang=en&format=pdf","access":"open","checked_at":"2026-11-02","status":"current"},"name":"Understorey trunk biomass from D30, height and wood density","output":{"quantity":"stem_biomass"},"expression":"exp(-3.48 + 1.731 * ln(D30) + 1.096 * ln(H) + 0.897 * ln(rho))","published":{"expression":"exp(-3.48 + 1.731 * ln(D) + 1.096 * ln(H) + 0.897 * ln(rho))","units":{"D":"cm","rho":"g/cm3","H":"m"},"variables":{"D":"D30"},"output_unit":"kg"},"taxon":{"level":"mixed","name":"Understorey trees and saplings, 184 species (stems 1–10 cm diameter)","group":"broadleaf"},"region":{"scope":"site","countries":["CM"],"place":"Semi-deciduous rainforest, East region, Cameroon","biomes":["tropical"]},"stand":"natural","fit":{"n_trees":1023,"h_min_m":0.86,"h_max_m":15.55,"rse":0.438,"method":"log-log regression, lnM = a + b ln(X1) + ..."},"evidence":[{"field":"expression","quote":"lnM= a + b × ln(D)+c × ln(H) + d × ln (ρ) 1023 -3.480*** 1.731*** 1.096*** 0.897*** 1.318 0.438 0.939 1220 0.10 2.44","locator":"Table 3, block \"Trunk\", p. 6"},{"field":"published.units","quote":"H: tree height; ρ: wood density; C: crown diameter; N: sample size; a, b, c and d are the model’s fitted parameters","locator":"Table 3 note, p. 6"},{"field":"fit.n_trees","quote":"AGB and several measurement variables (diameter, height, crown diameter, and wood density) were measured on 1023 understorey stems belonging to 184 species","locator":"Data collection, p. 3"},{"field":"notes","quote":"The diameter was measured at 30 cm aboveground level","locator":"Data collection, p. 3"},{"field":"notes","quote":"The correction factor (CF) calculated by the formula CF= RSE²/2 (5)","locator":"Data analysis, p. 4"}],"check":[{"inputs":{"D30":3,"H":4,"rho":0.56},"expected":0.56,"origin":"computed","note":"computed with python3 from the published form (uncorrected, as printed)"},{"inputs":{"D30":8,"H":9,"rho":0.6},"expected":7.921,"origin":"computed","note":"computed with python3 from the published form (uncorrected, as printed)"}],"verification":"original_read","checked_at":"2026-11-02","notes":"Selected from Table 2/3 \"All\" (1 ≤ diameter < 10 cm, n = 1023) block; the paper also gives separate seedling (1-5 cm) and sapling (5-10 cm) fits and crown-diameter models (not included: crown diameter unit is ambiguous, Table 1 header says cm but values are 0.19-7.55). D is the stem diameter at 30 cm above ground (D30), not DBH, so no DBH range is stored; Table 1 gives D 1.00-9.99 cm and H 0.86-15.55 m for the whole data set. Wood density is the mean of base, trunk and branch samples (dry weight / fresh volume). Published as the plain exp() back-transform: the paper lists a CF column (= RSE²/2, an additive term on the log scale) but does not print the corrected equation, so no correction factor is applied or stored. Total AGB = trunk + branches + leaves (dry mass, oven-dried at 105/70 °C). Recommended by the authors: the models with more predictors fit better (Adj.R² up to 0.956 with four predictors); the D-only model is the simplest. Stem (trunk) component only."}