{"id":"wirabuana-2025-h-sigmoid","source":{"id":"wirabuana-2025","citation":"Wirabuana, P., Nugroho, Y., & Mulyana, B. (2025). Diameter-Height relationship model for Shorea assamica in secondary tropical rainforest, South Borneo. Journal of Sylva Indonesiana, 8(2), 82-91.","title":"Diameter-Height relationship model for Shorea assamica in secondary tropical rainforest, South Borneo","authors":["Wirabuana, P.","Nugroho, Y.","Mulyana, B."],"year":2025,"venue":"Journal of Sylva Indonesiana","doi":"10.32734/jsi.v8i2.18749","url":"https://doi.org/10.32734/jsi.v8i2.18749","read_url":"https://talenta.usu.ac.id/Jsi/article/download/18749/9304","access":"open","license":"CC BY-SA 4.0","checked_at":"2026-11-02","status":"current"},"name":"Shorea assamica height from D, Sigmoid model (Table 4)","output":{"quantity":"height"},"expression":"exp(3.28 - 18.89 / D)","published":{"expression":"exp(3.28 - 18.89 / DBH)","units":{"DBH":"cm"},"variables":{"DBH":"D"},"output_unit":"m"},"taxon":{"level":"species","name":"Shorea assamica","family":"Dipterocarpaceae","group":"broadleaf"},"region":{"scope":"site","countries":["ID"],"place":"Tabalong District, South Kalimantan (PT Aya Yayang Indonesia concession, secondary lowland dipterocarp forest)","biomes":["tropical"]},"stand":"natural","fit":{"n_trees":1009,"dbh_min_cm":20,"dbh_max_cm":67,"h_min_m":11,"h_max_m":28,"r2":0.69,"method":"nonlinear least squares height-diameter model, fitted on 1009 of 1440 trees"},"evidence":[{"field":"expression","quote":"Sigmoid H = e^(a + b/DBH); a = 3.28, b = -18.89","locator":"Table 1 and Table 4, Sigmoid row"},{"field":"fit.n_trees","quote":"1009 tree height and diameter datasets were utilized","locator":"Section 3.1"},{"field":"fit.r2","quote":"R2 0.69","locator":"Table 4"}],"check":[{"inputs":{"D":25},"expected":12.4834,"origin":"computed","note":"computed from the published form (coefficients as printed)"},{"inputs":{"D":40},"expected":16.5726,"origin":"computed","note":"computed from the published form (coefficients as printed)"},{"inputs":{"D":60},"expected":19.3979,"origin":"computed","note":"computed from the published form (coefficients as printed)"}],"verification":"original_read","checked_at":"2026-11-02","notes":"Sigmoid form H = exp(a + b/DBH) as printed in Table 1 (typeset with b/DBH in the exponent). Fitted on the 70% model-development subset (1009 trees); DBH and height ranges are that subset (Table 3). Only trees with DBH >= 20 cm were recorded. Coefficients are printed to two decimals. The paper also lists Exponential and Gompertz models (Table 4) that were not added: the Exponential b is printed as 0.01 (too coarse to reproduce the fit) and the Gompertz coefficients as printed (a=152.37, b=0.01, c=170.49) do not give a sensible curve."}