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Ciceu, Albert García Duro, Juan Seceleanu, Ioan Badea, Ovidiu 2024-02-08T07:54:28Z 2024-02-08T07:54:28Z 2020 Forest Ecology and Management, December 2020, vol. 477, art. 118507 0378-1127 https://uvadoc.uva.es/handle/10324/65958 10.1016/J.FORECO.2020.118507 118507 Forest Ecology and Management 477 Producción Científica Tree height measurements are laborious and require more time and effort compared to tree diameter measurements. That being the case, height-diameter (H-D) models are usually used to predict individual tree heights, which are necessary for estimating the tree volume and the site index, as well as for projecting the stand development over time. Using a permanent sampling network (400x400m) from Retezat National Park in Romania, twenty-one (H-D) functions were evaluated for their fit performance, sensitivity to outliers and prediction ability for Norway spruce in mixed uneven aged stands. A set of twenty-three stand variables, both spatial and non-spatial, were used to describe the stand structure, species inter-mingling and competition, in order to be used as stand predictors in a generalized H-D model. Nonlinear mixed effects model was used in modelling the H-D relationship of Norway spruce. We developed the first generalized height-diameter model in Romania using three stand predictors as measures of the stand vertical structure, density and competition. Random and fixed effects calibration techniques were compared, testing various sampling designs in order to improve the height prediction accuracy of the model on a new dataset. Measuring six trees around the median and the thickest tree gave the best result in calibrating both fixed and random effects. On average, the best calibration design increased the accuracy of the prediction by 50 cm compared to the fixed effects prediction. The use of the estimated coefficients and the calibration design will significantly decrease the amount of work done by forest management planners, while ensuring high accuracy and reducing costs. The dataset used in this study was provided by a Core GENERESERV project supported by the Romanian Ministry of Research and Innovation within the National “Nucleu” Program – project code PN 09460117 aimed at long-term monitoring of the state of forest ecosystems. application/pdf eng Elsevier info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by-nc-nd/4.0/ © Elsevier Attribution-NonCommercial-NoDerivatives 4.0 Internacional Norway spruce (Piceaabies (L.) H.Karst) Uneven aged stands Mixed unmanaged spruce forest Nonlinear generalized mixed-effects height-diameter model Random and fixed effects calibration 3106.08 Silvicultura A generalized nonlinear mixed-effects height-diameter model for Norway spruce in mixed-uneven aged stands info:eu-repo/semantics/article info:eu-repo/semantics/acceptedVersion https://www.sciencedirect.com/science/article/pii/S0378112720312767?via%3Dihub SI