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Published VersionCC BY V4.0, Open Access
Journal article
Describing and Modelling Stem Form of Tropical Tree Species with Form Factor: A Comprehensive Review
Forests, Vol.16(1), pp.1-20
2025
Abstract
The concept of tree or stem form has been central to forest research for over a century, playing a vital role in accurately assessing tree growth, volume, and biomass. The form factor is an essential component for expressing the shape of a tree, enabling more accurate volume estimation, which is vital for sustainable forest management and planning. Despite its simplicity, flexibility, and advantages in volume estimation, the form factor has received less attention compared to other measures like taper equations and form quotient. This review summarizes the concept, theories, and measures of stem form, and describes the factors influencing its variation. It focuses on the form factor, exploring its types, parameterization, and models in the context of various tropical species and geographic conditions. The review also discusses the use of the form factor in volume estimation and the issues with using default or generic values. The reviewed studies show that tree stem form and form factor variations are influenced by multiple site, tree, and stand characteristics, including site quality, soil type, climate conditions, tree species, age, crown metrics, genetic factors, stand density, and silviculture. The breast height form factor is the most adopted among the three common types of form factors due to its comparative benefits. Of the five most tested form factor functions for predicting tree form factors, Pollanschütz’s function is generally considered the best. However, its performance is often not significantly different from other models. This review identifies the “Hohenadl” method and mixed-effects modelling as overlooked yet potentially valuable approaches for form factor modelling. Using the form factor, especially by diameter or age classes, can enhance tree volume estimation, surpassing volume equations. However, relying on default or generic form factors can lead to volume and biomass estimation errors of up to 17–35%, underscoring the need to limit variation sources in form factor modelling and application. Further recommendations are provided for improving the statistical techniques involved in developing form factor functions.
Details
- Title
- Describing and Modelling Stem Form of Tropical Tree Species with Form Factor: A Comprehensive Review
- Authors
- Tomiwa Victor Oluwajuwon (Corresponding Author) - University of the Sunshine Coast, Queensland, School of Science, Technology and EngineeringChioma E. Ogbuka (Author) - University of Arkansas at MonticelloFriday N. Ogana (Author) - Virginia Polytechnic Institute and State University (United States)Md. Sazzad Hossain (Author) - Technische Universität DresdenRebecca Israel (Author) - University of IbadanDavid Lee (Author) - University of the Sunshine Coast, Queensland, Forest Research Institute
- Publication details
- Forests, Vol.16(1), pp.1-20
- Publisher
- MDPI AG
- Date published
- 2025
- DOI
- 10.3390/f16010029
- ISSN
- 1999-4907
- Copyright note
- © 2024 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
- Data Availability
- No new data were created or analysed in this study.
- Grant note
- This work received funding support to cover its publishing costs from the Forest Research Institute, University of the Sunshine Coast.
- Organisation Unit
- School of Science, Technology and Engineering
- Language
- English
- Record Identifier
- 991090998802621
- Output Type
- Journal article
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- Forestry
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