{"id":"brown-1997-moist-quadratic","source":{"id":"brown-1997","citation":"Brown, S. (1997). Estimating Biomass and Biomass Change of Tropical Forests: a Primer. FAO Forestry Paper 134. Rome: Food and Agriculture Organization of the United Nations. ISBN 92-5-103955-0.","title":"Estimating Biomass and Biomass Change of Tropical Forests: a Primer (FAO Forestry Paper 134)","authors":["Brown, S."],"year":1997,"venue":"FAO Forestry Paper 134","url":"https://www.fao.org/4/w4095e/w4095e00.htm","read_url":"https://www.fao.org/4/w4095e/w4095e06.htm","access":"open","checked_at":"2026-11-01","status":"current"},"name":"Moist tropical zone AGB, quadratic (Eq. 3.2.3)","output":{"quantity":"agb"},"expression":"42.69 - 12.800 * D + 1.242 * D^2","published":{"expression":"42.69 - 12.800 * D + 1.242 * D^2","units":{"D":"cm"},"output_unit":"kg"},"taxon":{"level":"mixed","name":"Tropical broadleaf trees (mixed species)","group":"broadleaf"},"region":{"scope":"pantropical","countries":[],"place":"Tropics, moist zone","biomes":["tropical"]},"stand":"natural","fit":{"n_trees":170,"dbh_min_cm":5,"dbh_max_cm":148,"r2":0.84},"evidence":[{"field":"expression","quote":"Y = 42.69-12.800(D)+1.242(D2)","locator":"Eq. 3.2.3, Section 3.2.1 table"},{"field":"published.units","quote":"Y= biomass per tree in kg, D = dbh in cm, and BA = basal area in cm2","locator":"Section 3.2.1, biomass regression equations table header"},{"field":"fit.n_trees","quote":"5-148 | 170 | 0,84","locator":"Eq. 3.2.3 row: range in dbh (cm), number of trees, adjusted r2"}],"check":[{"inputs":{"D":30},"expected":776.49,"origin":"computed","note":"computed with python3 from the published form"},{"inputs":{"D":100},"expected":11182.69,"origin":"computed","note":"computed with python3 from the published form"}],"verification":"original_read","checked_at":"2026-11-01","notes":"A. J. R. Gillespie (pers. comm.) revision of the Brown et al. (1989) moist equation. The primer recommends this form for trees with dbh above about 160 cm because it behaves better there than Eq. 3.2.4. r2 is adjusted r². Note: the primer's worked stand-table example says it uses Eq. 3.2.3 but its per-tree values match Eq. 3.2.4. The primer does not say whether a log back-transform correction is included; none applied. Climatic zones per the primer: dry <1500 mm/yr rain with a dry season of several months; moist 1500–4000 mm/yr; wet >4000 mm/yr, lowland conditions only."}