A pan-tropical database and synthesis of age–height and age–diameter growth in planted forest stands up to 40 years

: Tree size–age relationships in tropical planted forest stands support management and ecosystem-service assessments, but locally calibrated growth models are unavailable for many taxa and regions. We compiled and harmonised 2,455 age–diameter at breast height (DBH) records from 27 studies and 498 age–height records from 24 studies, covering 234 harmonised taxa and encompassing tree-, sample/plot-, and stand-level reporting. Analyses focused on the best-supported age window, ≤ 40 years, comprising 2,447 DBH and 472 height observations. General relationships were described using nonlinear growth curves, and their robustness was evaluated through weighting, study-balanced, reporting-level, classification-sensitivity, and leave-one-study-out analyses. The pooled unweighted DBH curve provides a general evidence-weighted relationship, while the slow-growth class offers a conservative scenario: DBH( t ) = 34.95 [1 − exp(−0.0279 t )] 0.811 . For height, the recommended general trajectory is H ( t ) = 25.93 [1 − exp(−0.0486 t )] 0.960 . Exceptionally rapid juvenile height growth is represented separately by H ( t ) = 8.235 t 0.4769 , for 1 ≤ t ≤ 10 years. A non-asymptotic power model was also used to represent the fast DBH class over its observed age range. Sensitivity analyses showed that the main trajectories were robust within the age ranges most strongly represented in the database, although long-term parameters and older-age predictions were more sensitive to study composition. Where plantation age is known, but suitable local growth equations are unavailable, the resulting functions provide transparent, reproducible alternatives to arbitrary assumptions or equations borrowed from unrelated systems. They can support benchmarking, provisional size estimation, preliminary biomass scenarios, and the initialization or calibration of more specific models. The open database and scripts allow users to inspect the underlying evidence, add local observations, and refine the relationships as further information becomes available.